Happy Sci-Day, everyone! As we continue progress on the game, we are continuing to provide you with educational posts so that you will have a better understanding of exactly what goes into development, and why it takes so much effort to do what we wish to do. Today, I will be continuing with my Evolutionary Biology Crash Course mini-series - this week, we're going to cover Darwinian evolution!
First thing we need to understand is the difference between the terms "pattern" and "process" as they are used in Evolutionary Biology, and how they relate to one another. Studying patterns is identifying the order in nature - this is the stuff we see with our own eyes (as well as genetic sequence data). Studying patterns is where we infer or determine the actual mechanisms that generate and maintain this order. Patterns are the result of processes. An analogy you might use to remember this would be to think of baking a cake - the cake itself is the 'pattern', and the raw ingredients and instructions for mixing them are the 'processes'.
Now, let's move on to Darwinian evolution. Darwinian evolution is concerned with natural selection, which consists of three main components. Two of these relate to traits - genes, and environment. The third is related to the limits of natural selection, which we will cover later. The result of these three components is a change in the population over time.
There are some important things we need to understand about how natural selection works. Natural selection sorts based on phenotypes (the actual observed characteristic that results from interactions between genes and environment), not genotypes. Genes or genotypes by themselves do not code for specific traits. Rather, genotypes determine traits in the context of some particular set of environmental conditions. Natural selection results in adaptation. An adaptation is any trait that makes an organism more fit in its environment. An example would be the flat, paddle-like tail of Champsosaurus, which would allow it to swim far more efficiently than it would otherwise.
There are some key differences between natural selection and evolution. Natural selection acts on an individual level, whereas evolution occurs within populations. Even though an individual changes over time (development - the study of development within individuals over time is also known as ontogeny), individuals do not experience biological evolution. Furthermore, natural selection is merely one possible mechanism that can result in biological evolution - we will cover additional mechanisms as we get further into this crash course.
As I briefly mentioned further up, natural selection has limits. Some of these are due simply to physics - ie there is a maximum size to individual cells due to surface area/volume ratio which has key implications for nutrient exchange. Others are due to more biological/ecological factors. Natural selection can only act on existing variation - while new alleles/traits arise through things such as mutation, natural selection cannot act upon them until they are introduced. Furthermore, traits are only beneficial in a certain set of environmental conditions - natural selection cannot result in perfection. A great example of the costs of natural selection would be the modern cheetah. They have many traits that allow them to run at incredible speeds, but these result in a far more lightweight and fragile anatomy. This fragility means that they are not able to defend a kill against larger predators, and thus they may end up wasting lots of energy on a hunt only to have their food taken by a lion or hyena.
Another very important thing to understand is that evolution does not show foresight. One of my pet peeves as an evolutionary biologist is when someone uses words like "try", "need", or "want" when they are describing natural selection. Unlike in Disney movies, making a wish will not lead to any increase in fitness, nor will the "power of friendship." For example, if a hypothetical trait required several less-fit intermediates to evolve (again, this is purely hypothetical), it would not evolve because those required intermediates would be removed from the population.
Well, I hope this has helped you understand a bit more about natural selection/Darwinian evolution! Before you tune in next week, make sure to read Sci-Day #1 that reviews cladistics and phylogenetics!
Acknowlegements:
BIOL 412 (Evolutionary Biology). Lecture slides, January 26, 2016.
Showing posts with label Sci-Day. Show all posts
Showing posts with label Sci-Day. Show all posts
Friday, June 17, 2016
Friday, June 10, 2016
Sci-Day 20: Crash Course in Evolutionary Biology, part 1
Greetings, fans! I've decided to start a new Sci-Day mini-series, that will be based on my Evolutionary Biology class that I took in the Spring semester, in terms of organization (ie subject order) and topics. For this reason, unless otherwise stated, most of this information comes from the relevant lecture slides from the course, though I'm certain any Evolutionary Biology textbook would also contain the same or at least similar information. I will also say that because there will be a lot of stuff related to inheritance, alleles, and genes, you should do some reading up on exactly what those terms mean. You should have a good understanding of Mendelian inheritance, what an allele/locus/gene is, but we will not have to worry about things such as how DNA is replicated or any of the molecular processes. Since I am focusing all of my time on writing this, I do not have the time to give links to specific sources to get that information, but a decent Google search for terms such as "Mendelian inheritance" should give you a good enough start.
A key thing that I think is most interesting is that, while the things we will discuss are not really possible to test or examine in extinct species, once Dinosaur Battlegrounds has been fully released and all features are in place, simulations could let us investigate such questions given certain assumptions. One thing of note: I have covered several topics that would otherwise be included in this mini-series, so I will reference those posts instead of posting the same thing again.
In this post, I will just be introducing you to the topic of evolutionary biology, why it's important, and what it is. I hope you enjoy this, and learn something new!
Before we get started on anything, we need to ask ourselves one key question:
What is evolution?
To put it very simply, evolution is CHANGE. This may be development in an individual, such as in the life cycle of a frog. It can also be ecosystem change; for example, the recession of the Western Interior Seaway towards the very close of the Cretaceous altered the ecosystems surrounding it (as well as the Seaway itself, obviously). There is also cultural evolution - these are changes in how humans communicate with one another, but because humans are boring and we want to get to the good stuff that relates to dinosaurs, we'll just pretend it doesn't count.
However, the type of evolution that you probably first think of when you hear the word is biological evolution. Biological evolution is the change in properties of some population of organisms over generations. These properties must be HERITABLE, which leads us to a more precise and accurate definition: biological evolution is the change in allele frequencies in a population over time. A sort of 'synonym' for biological evolution is 'descent with modification', a term used by Darwin himself in his famous work, "On the Origin of Species".
Evolution is extremely important to understand because it is the central unifying theory of modern biology. As Dobzhansky put it, Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts some of them interesting or curious but making no meaningful picture as a whole" (Dobzhansky, 1973). It allows us to gain an understanding of both how observed features (on a genetic and anatomical basis) developed, and why. Perhaps the best example I can think of would be the evolution/origin of birds. Without any evolutionary context it would be impossible to understand just how birds evolved powered flight, or their origins. Now, because of our great understanding of biological evolution, as well as advances in both methodology and biological theory, we know that birds evolved from a lineage of theropod dinosaurs during the Mesozoic.
That is all for this week - I could go on forever about how cool and important evolution is, but I don't want to end up being redundant and boring! Next week we'll go a bit more into Darwinian evolution, so stay tuned!
Acknowledgements:
Evolutionary Biology, Spring 2016. Lecture Notes. University of Kansas.
Dobzhansky, T. 1973. Nothing in biology makes sense except in the light of evolution. The American Biology Teacher 35: 125-129.
A key thing that I think is most interesting is that, while the things we will discuss are not really possible to test or examine in extinct species, once Dinosaur Battlegrounds has been fully released and all features are in place, simulations could let us investigate such questions given certain assumptions. One thing of note: I have covered several topics that would otherwise be included in this mini-series, so I will reference those posts instead of posting the same thing again.
In this post, I will just be introducing you to the topic of evolutionary biology, why it's important, and what it is. I hope you enjoy this, and learn something new!
Before we get started on anything, we need to ask ourselves one key question:
What is evolution?
To put it very simply, evolution is CHANGE. This may be development in an individual, such as in the life cycle of a frog. It can also be ecosystem change; for example, the recession of the Western Interior Seaway towards the very close of the Cretaceous altered the ecosystems surrounding it (as well as the Seaway itself, obviously). There is also cultural evolution - these are changes in how humans communicate with one another, but because humans are boring and we want to get to the good stuff that relates to dinosaurs, we'll just pretend it doesn't count.
However, the type of evolution that you probably first think of when you hear the word is biological evolution. Biological evolution is the change in properties of some population of organisms over generations. These properties must be HERITABLE, which leads us to a more precise and accurate definition: biological evolution is the change in allele frequencies in a population over time. A sort of 'synonym' for biological evolution is 'descent with modification', a term used by Darwin himself in his famous work, "On the Origin of Species".
Evolution is extremely important to understand because it is the central unifying theory of modern biology. As Dobzhansky put it, Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts some of them interesting or curious but making no meaningful picture as a whole" (Dobzhansky, 1973). It allows us to gain an understanding of both how observed features (on a genetic and anatomical basis) developed, and why. Perhaps the best example I can think of would be the evolution/origin of birds. Without any evolutionary context it would be impossible to understand just how birds evolved powered flight, or their origins. Now, because of our great understanding of biological evolution, as well as advances in both methodology and biological theory, we know that birds evolved from a lineage of theropod dinosaurs during the Mesozoic.
That is all for this week - I could go on forever about how cool and important evolution is, but I don't want to end up being redundant and boring! Next week we'll go a bit more into Darwinian evolution, so stay tuned!
Acknowledgements:
Evolutionary Biology, Spring 2016. Lecture Notes. University of Kansas.
Dobzhansky, T. 1973. Nothing in biology makes sense except in the light of evolution. The American Biology Teacher 35: 125-129.
Friday, May 20, 2016
Sci-Day 19: Color in Dinosaurs
Greetings, fans! This Sci-Day I will be discussing a rather interesting topic that relates to some of my own work - coloration in dinosaurs [though my work currently is focused on modern reptiles].
For obvious reasons, when imagining coloration in long-extinct creatures we mostly have to make educated guesses based on modern animals. However, there are exceptions, such as in the case of the early Cretaceous Microraptor, where scans with an electron microscope revealed preserved melanosomes [pigmentation cells] within the feathers, the orientation/stacking of which was consistent with black, iridescent coloration in modern birds such as the starling - this may have served a similar function as in the modern analogue, for sexual display purposes (Li, 2012). Preserved melanosomes have also been found in Sinornithosaurus, though its coloration was not uniform across the body (Zhang et al., 2010). A follow-up study in 2012 showed that the colors were reddish brown, yellow, black, and gray, which were distributed across the body (Naish, 2012). It is important to note that such exceptions are rare, and for the most part we do not know what color dinosaurs were. For this reason, we must look at modern analogues for inspiration. This requires us to understand the uses of coloration in the natural world, so that we may hypothesize the possible roles colors may have played in the lives of dinosaurs.
In order to hypothesize what roles and importance color might have had in the lives of dinosaurs, we first need to understand a bit more about color vision from both an anatomical and evolutionary standpoint. In vertebrates, there are two specialized types of receptors in the back of the eye - rods and cones. The former of the two are responsible for low-light contrast, whereas the latter are responsible for perceiving color. Cone cells contain one of several proteins called opsins, each of which has a different spectral sensitivity - in other words, each type of pigment is best able to detect a particular set of wavelengths in the spectrum. By having many, many cone cells with several different pigment types, the eye can perceive multiple different colors.
Based on this information, it is somewhat intuitive that the number of different types of cone cell pigment an animal has influences its ability to see colors. Humans and other primates have three different types of pigment - in other words, we have trichromatic color vision. However, the earliest vertebrates actually had tetrachromatic color vision, which was then lost in mammals. Thus, reptiles and birds actually both have tetrachromatic vision (Bowmaker, 1998), meaning that they have a much better ability to see color than we do. Taking this into account, along with the many examples of the importance of color in both lineages, it is rather safe to assume that dinosaurs also used color in many different ways.
Another thing we must understand is the mechanisms responsible for coloration in both reptiles and birds. As many people know, color is generated by specialized cells collectively known as chromatophores. The most widely known of these is the melanophores, which produce melanin (the pigment responsible for black and shades of brown). However, reptiles and other poikilothermic vertebrates have two additional types of chromatophore that produce chemical pigments, known as xanthophores (responsible for yellows) and erythrophores (responsible for reds) - these two contain a mixture of different pteridine and carotenoid pigments (Bechtel, 1978). In addition, they also have structural chromatophores called iridophores - rather than containing chemical pigments, these cells reflect different wavelengths of light based on the structure of the cells themselves. Together, different combinations, densities, and distribution of these chromatophores allows for a diversity of colors. However in birds, the only chemical pigment cells are melanophores - the many colors that we see in bird plumage is due to the structure of the feathers themselves. For example, peacock feathers are actually pigmented brown, but their structure interacts with these melanophores to create the vivid colors we perceive (Ball, 2012).
This makes one wonder - when were these specialized chromatophores we find in reptiles lost? My intuition tells me that it likely coincided with the appearance of feathers - since they have an alternate mechanism for generating diverse colors, there is no need for the chromatophores (plus they are found in the skin which is covered by the feathers). However, this is simply speculation and would require further evidence such as molecular data to investigate.
Back to the topic at hand, given the diversity of coloration within reptiles and birds, it is fair to assume that non-avian dinosaurs also came in many different colors. Many modern reptiles and birds use color as a signaling tool, as an indicator of mate quality/health, to intimidate rivals, and obviously to blend in to the environment. Additionally, many reptile and bird species that make use of conspicuous color signals show significant variation in the color of the relevant appendage/body part across their range. A great example of this would be the dewlaps found in the genus Anolis, where a single species may have vastly differing dewlap color and shape between localities. This might have been the case in some dinosaur species if they too used such a signal. For example, perhaps Triceratops would flood its frill with blood to create bright colors to attract mates and intimidate rivals - if it did so, there may have been vastly differing frill colorations between areas of its natural range. Obviously this is purely hypothetical, but it is not beyond the bounds of sound reasoning.
Well, I hope you have enjoyed this week's Sci-Day! Since my current project is related to pigmentation in reptiles, it is helpful for me to explain the mechanisms behind it as well!
Acknowledgements:
Li, Quanguo. 2012. Reconstruction of Microraptor and the Evolution of Iridescent Plumage. Science 335: 1215-1219.
Zhang, Fucheng; Kearns, Stuart L.; Orr, Patrick J.; Benton, Michael J.; Zhou, Zhonghe; Johnson, Diane; Xu, Xing; Wang, Xiaolin. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463 (7284): 1075-1078.
Naish, Darren. 2012. Planet Dinosaur: The Next Generation of Killer Giants. Firefly Books. p. 192.
Bowmaker, J. K. 1998. Evolution of colour vision in vertebrates. Eye 12 (3b): 541-547.
For obvious reasons, when imagining coloration in long-extinct creatures we mostly have to make educated guesses based on modern animals. However, there are exceptions, such as in the case of the early Cretaceous Microraptor, where scans with an electron microscope revealed preserved melanosomes [pigmentation cells] within the feathers, the orientation/stacking of which was consistent with black, iridescent coloration in modern birds such as the starling - this may have served a similar function as in the modern analogue, for sexual display purposes (Li, 2012). Preserved melanosomes have also been found in Sinornithosaurus, though its coloration was not uniform across the body (Zhang et al., 2010). A follow-up study in 2012 showed that the colors were reddish brown, yellow, black, and gray, which were distributed across the body (Naish, 2012). It is important to note that such exceptions are rare, and for the most part we do not know what color dinosaurs were. For this reason, we must look at modern analogues for inspiration. This requires us to understand the uses of coloration in the natural world, so that we may hypothesize the possible roles colors may have played in the lives of dinosaurs.
In order to hypothesize what roles and importance color might have had in the lives of dinosaurs, we first need to understand a bit more about color vision from both an anatomical and evolutionary standpoint. In vertebrates, there are two specialized types of receptors in the back of the eye - rods and cones. The former of the two are responsible for low-light contrast, whereas the latter are responsible for perceiving color. Cone cells contain one of several proteins called opsins, each of which has a different spectral sensitivity - in other words, each type of pigment is best able to detect a particular set of wavelengths in the spectrum. By having many, many cone cells with several different pigment types, the eye can perceive multiple different colors.
Based on this information, it is somewhat intuitive that the number of different types of cone cell pigment an animal has influences its ability to see colors. Humans and other primates have three different types of pigment - in other words, we have trichromatic color vision. However, the earliest vertebrates actually had tetrachromatic color vision, which was then lost in mammals. Thus, reptiles and birds actually both have tetrachromatic vision (Bowmaker, 1998), meaning that they have a much better ability to see color than we do. Taking this into account, along with the many examples of the importance of color in both lineages, it is rather safe to assume that dinosaurs also used color in many different ways.
Another thing we must understand is the mechanisms responsible for coloration in both reptiles and birds. As many people know, color is generated by specialized cells collectively known as chromatophores. The most widely known of these is the melanophores, which produce melanin (the pigment responsible for black and shades of brown). However, reptiles and other poikilothermic vertebrates have two additional types of chromatophore that produce chemical pigments, known as xanthophores (responsible for yellows) and erythrophores (responsible for reds) - these two contain a mixture of different pteridine and carotenoid pigments (Bechtel, 1978). In addition, they also have structural chromatophores called iridophores - rather than containing chemical pigments, these cells reflect different wavelengths of light based on the structure of the cells themselves. Together, different combinations, densities, and distribution of these chromatophores allows for a diversity of colors. However in birds, the only chemical pigment cells are melanophores - the many colors that we see in bird plumage is due to the structure of the feathers themselves. For example, peacock feathers are actually pigmented brown, but their structure interacts with these melanophores to create the vivid colors we perceive (Ball, 2012).
This makes one wonder - when were these specialized chromatophores we find in reptiles lost? My intuition tells me that it likely coincided with the appearance of feathers - since they have an alternate mechanism for generating diverse colors, there is no need for the chromatophores (plus they are found in the skin which is covered by the feathers). However, this is simply speculation and would require further evidence such as molecular data to investigate.
Back to the topic at hand, given the diversity of coloration within reptiles and birds, it is fair to assume that non-avian dinosaurs also came in many different colors. Many modern reptiles and birds use color as a signaling tool, as an indicator of mate quality/health, to intimidate rivals, and obviously to blend in to the environment. Additionally, many reptile and bird species that make use of conspicuous color signals show significant variation in the color of the relevant appendage/body part across their range. A great example of this would be the dewlaps found in the genus Anolis, where a single species may have vastly differing dewlap color and shape between localities. This might have been the case in some dinosaur species if they too used such a signal. For example, perhaps Triceratops would flood its frill with blood to create bright colors to attract mates and intimidate rivals - if it did so, there may have been vastly differing frill colorations between areas of its natural range. Obviously this is purely hypothetical, but it is not beyond the bounds of sound reasoning.
Well, I hope you have enjoyed this week's Sci-Day! Since my current project is related to pigmentation in reptiles, it is helpful for me to explain the mechanisms behind it as well!
Acknowledgements:
Li, Quanguo. 2012. Reconstruction of Microraptor and the Evolution of Iridescent Plumage. Science 335: 1215-1219.
Zhang, Fucheng; Kearns, Stuart L.; Orr, Patrick J.; Benton, Michael J.; Zhou, Zhonghe; Johnson, Diane; Xu, Xing; Wang, Xiaolin. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463 (7284): 1075-1078.
Naish, Darren. 2012. Planet Dinosaur: The Next Generation of Killer Giants. Firefly Books. p. 192.
Bowmaker, J. K. 1998. Evolution of colour vision in vertebrates. Eye 12 (3b): 541-547.
Bechtel,
H. Bernard. 1978. Color and Pattern in Snakes (Reptilia: Serpentes). Journal of
Herpetology 12 (4): 521-532.
Ball, Philip. 2012. Nature's Color Tricks. Scientific American 306 (5): 74-79
Friday, May 13, 2016
Sci-Day 17: T Rex expedition details
THE T. REX:
The Tyrannosaurus rex specimen has already been partially excavated, and the material that has been cleaned up is on display at the KU Natural History Museum. So far, the consists of the left maxilla, lacrimal, jugal, and postorbital, the nasal, the right dentary, several cervical ribs, the furcula, a few vertebrae, fragments of the pubis and ischium, and several bones from the hind limbs. Based on measurements of the dentary, this individual was between 14 and 16 years old. This age estimate is also supported by the fact that the teeth are shorter in proportion to body size than in older T. rex specimens. This probably means that it would have hunted smaller prey - given that juvenile T. rex had proportionally longer hindlimbs and a lighter overall build than adults, they may have been better equipped for tackling more swift-moving herbivores.
Additionally, a cross-section of the femur shows what may be evidence of medullary bone - though it could also be due to some sort of pathology such as an infection. If upon closer analysis it does turn out to be evidence of medullary bone, this would give us another T. rex specimen of known (ie confirmed) sex. In T. rex specimens, there are two distinct morphotypes, called the 'gracile' and 'robust' morphs. Some have argued that this represents sexual dimorphism, with the robust morphotype representing the females, but due to the fact that it is nearly impossible to determine the sex of a fossil animal in normal circumstances this has been an issue of debate. However, given that [provided that the medullary bone presence is confirmed] both confirmed female T. rex are of the robust morphotype, this could be solid evidence that the morphotypes represent the two sexes (though a sample size of 2 is not going to give a great level of certainty). Since there are many other dinosaur species showing the same pattern of 'gracile' and 'robust' morphotypes, understanding the cause of this dichotomy in T. rex could allow us to apply that knowledge to other species.
A secondary reason why the presence of medullary bone in this specimen would be significant is due to its age. Since medullary bone is only found in birds that are gravid (eggs not laid yet) or have recently laid eggs, this would indicate that the animal reached sexual maturity before it was finished growing.
The specimen also shows evidence of past injury - there is a raised, roughened area on the left tibia, providing evidence of possible infection or disease. However, whether or not this played a role in the death of this individual is uncertain. Closer inspection and excavation/cleaning of more skeletal material may give us a better idea, and may even reveal additional pathologies - only time will tell!
The Tyrannosaurus rex specimen has already been partially excavated, and the material that has been cleaned up is on display at the KU Natural History Museum. So far, the consists of the left maxilla, lacrimal, jugal, and postorbital, the nasal, the right dentary, several cervical ribs, the furcula, a few vertebrae, fragments of the pubis and ischium, and several bones from the hind limbs. Based on measurements of the dentary, this individual was between 14 and 16 years old. This age estimate is also supported by the fact that the teeth are shorter in proportion to body size than in older T. rex specimens. This probably means that it would have hunted smaller prey - given that juvenile T. rex had proportionally longer hindlimbs and a lighter overall build than adults, they may have been better equipped for tackling more swift-moving herbivores.
Additionally, a cross-section of the femur shows what may be evidence of medullary bone - though it could also be due to some sort of pathology such as an infection. If upon closer analysis it does turn out to be evidence of medullary bone, this would give us another T. rex specimen of known (ie confirmed) sex. In T. rex specimens, there are two distinct morphotypes, called the 'gracile' and 'robust' morphs. Some have argued that this represents sexual dimorphism, with the robust morphotype representing the females, but due to the fact that it is nearly impossible to determine the sex of a fossil animal in normal circumstances this has been an issue of debate. However, given that [provided that the medullary bone presence is confirmed] both confirmed female T. rex are of the robust morphotype, this could be solid evidence that the morphotypes represent the two sexes (though a sample size of 2 is not going to give a great level of certainty). Since there are many other dinosaur species showing the same pattern of 'gracile' and 'robust' morphotypes, understanding the cause of this dichotomy in T. rex could allow us to apply that knowledge to other species.
T. rex femoral cross-section, showing possible medullary bone (light colored center of the bone).
A secondary reason why the presence of medullary bone in this specimen would be significant is due to its age. Since medullary bone is only found in birds that are gravid (eggs not laid yet) or have recently laid eggs, this would indicate that the animal reached sexual maturity before it was finished growing.
The specimen also shows evidence of past injury - there is a raised, roughened area on the left tibia, providing evidence of possible infection or disease. However, whether or not this played a role in the death of this individual is uncertain. Closer inspection and excavation/cleaning of more skeletal material may give us a better idea, and may even reveal additional pathologies - only time will tell!
THE LOCALITY:
The locality is fluvial mudstone, likely representing a curve in a river - it is likely that the T. rex was carried downstream after death. In the same locality, a femur attributed to an Ornithomimosaur has been uncovered, though it is not known whether or not there is more material from the specimen since the site where the femur was found has not been excavated any further. I do hope that at some point someone does more digging to see if there is more material, as it could potentially be a specimen of Ornithomimus velox, which is currently only known from a few ankle bones. As more work is done on the layer, there may be yet more fossils uncovered.
In the pictures, the fossil-bearing layer is visible as a purplish-brown layer of rock. This summer, we will be working with awls and brushes from the level of the shovel (see attached photo) to the cliff face.
As I've said, I'm super excited for this amazing opportunity, and I hope that this post about the specifics of the expedition has gotten you excited as well!
Sci-Day 16: T-Rex Excavation!!!
Like I've been building up for the past week, today's Sci-Day is very exciting, and is not like any other Sci-Day. Rather than talking about a general concept in science, this is going to be about a very specific paleontological endeavor that is in progress right now: the excavation of a Tyrannosaurus rex skeleton.
I managed to help secure a large portion of the funding necessary for this excavation that is led by the Vertebrate Paleontology team here at the University of Kansas. Additionally, I will be going out to the site (in Montana) for a week sometime this summer to help with the dig. I think that anyone who truly understands what Dinosaur Battlegrounds is about can see why this is very exciting! While I do have some lab experience and have read many papers and published literature on paleontology, I have never actually had the chance to go out into the field and uncover fossils. I hope that this will be only the first of many more such expeditions in the future!
Another reason this is so wonderful is because it gives me a chance to give back to the paleontological community - the reason Dinosaur Battlegrounds has resonated with so many people and has the potential to do so well is because our focus is on accuracy. Our accuracy is based on the hard work and sweat of many smart, experienced people who have dedicated their lives to learning about the ancient earth. If it weren't for them, Dinosaur Battlegrounds would be nothing more than just another dinosaur game. We owe them our gratitude, and it is only fair that we do our part.
Furthermore, in order for us to be as accurate as possible, we need to learn as much as we can about the ecosystems we are working to restore. To do that, we need to fund research and field expeditions as much as possible so that we can continue to improve our simulations. Further field expeditions could yield more complete remains of various species that we had to make lots of approximations for, it could help us reduce the number of 'placeholder models', and things of that nature. As we start expanding to include formations such as the Kem Kem beds (with Spinosaurus), this will become even more critical as even the 'main attraction' species are rather mysterious and not much is known with extreme certainty.
Later today, I will post a second Sci-Day after talking with Dr. Krishtalka (he was the one who proposed this fantastic opportunity, I am forever in his debt), giving a bit more information about the specific T Rex, and other things of that nature. I also plan to have a day-by-day journal during the experience, talking about things as they are going along, so that all of our fans can get a true idea of what field work is actually like. I will also talk a little bit about preparations beforehand, so that people can understand a bit about what it takes. This way, for any of you who are hoping to one day enter the fascinating and wonderful field of paleontology, you know what things you will need!
I hope you all are at least half as excited about this as I am - seeing fossils on display or in a museum collection is one thing, but the experience of actually unearthing them from the rock is another! I'd like to thank Doctor Leonard Krishtalka as well as everyone on the KU Vertebrate Paleontology team for offering me this opportunity, and for being so helpful as resources of information on all things prehistoric!
I managed to help secure a large portion of the funding necessary for this excavation that is led by the Vertebrate Paleontology team here at the University of Kansas. Additionally, I will be going out to the site (in Montana) for a week sometime this summer to help with the dig. I think that anyone who truly understands what Dinosaur Battlegrounds is about can see why this is very exciting! While I do have some lab experience and have read many papers and published literature on paleontology, I have never actually had the chance to go out into the field and uncover fossils. I hope that this will be only the first of many more such expeditions in the future!
Another reason this is so wonderful is because it gives me a chance to give back to the paleontological community - the reason Dinosaur Battlegrounds has resonated with so many people and has the potential to do so well is because our focus is on accuracy. Our accuracy is based on the hard work and sweat of many smart, experienced people who have dedicated their lives to learning about the ancient earth. If it weren't for them, Dinosaur Battlegrounds would be nothing more than just another dinosaur game. We owe them our gratitude, and it is only fair that we do our part.
Furthermore, in order for us to be as accurate as possible, we need to learn as much as we can about the ecosystems we are working to restore. To do that, we need to fund research and field expeditions as much as possible so that we can continue to improve our simulations. Further field expeditions could yield more complete remains of various species that we had to make lots of approximations for, it could help us reduce the number of 'placeholder models', and things of that nature. As we start expanding to include formations such as the Kem Kem beds (with Spinosaurus), this will become even more critical as even the 'main attraction' species are rather mysterious and not much is known with extreme certainty.
Later today, I will post a second Sci-Day after talking with Dr. Krishtalka (he was the one who proposed this fantastic opportunity, I am forever in his debt), giving a bit more information about the specific T Rex, and other things of that nature. I also plan to have a day-by-day journal during the experience, talking about things as they are going along, so that all of our fans can get a true idea of what field work is actually like. I will also talk a little bit about preparations beforehand, so that people can understand a bit about what it takes. This way, for any of you who are hoping to one day enter the fascinating and wonderful field of paleontology, you know what things you will need!
I hope you all are at least half as excited about this as I am - seeing fossils on display or in a museum collection is one thing, but the experience of actually unearthing them from the rock is another! I'd like to thank Doctor Leonard Krishtalka as well as everyone on the KU Vertebrate Paleontology team for offering me this opportunity, and for being so helpful as resources of information on all things prehistoric!
Friday, April 29, 2016
Sci-Day 15: Speciation
Happy Sci-Day, everyone! This week will be somewhat related to last week's topic, as well as topics that I will be covering related to evolutionary biology in future posts. The topic for today is speciation - basically, the formation of new, distinct species.
The reason this relates to last week's post is because in order to understand how a 'species' is formed, we have to have some idea of what a species actually is. Speciation basically involves the splitting of an original, single population of organisms into two new populations, each of which is reproductively isolated from the other. Through some process, whether that is biological or abiotic, this isolation means there is no gene flow between the two populations, leading to independent evolution in each new population. Over time, mutations build up in each lineage, and they become more and more distinct (This could be purely on a genetic level - there don't necessarily have to be any evident morphological differences).
There are two main modes of speciation, defined by the process that split the original population. The first mode, and the one that is the easiest to identify in paleontology, is called allopatric speciation. In allopatric speciation, the ranges of the two new populations do not overlap - one example would be a large mountain range rising within the range of some species, where populations of that species on one side of the range are isolated from the population on the other side due to geographical factors - the species cannot cross that new barrier and as such the population is split.
A second type of speciation that is a bit harder to examine, especially from a paleontological standpoint, is called sympatric speciation. Unlike allopatric speciation, the ranges of the two new populations are not separated geographically - the two populations at least partially overlap at some part of their range. Since observing sympatric speciation relies primarily on genetic/molecular data, it is not exactly an issue that paleontologists can investigate with long-extinct creatures. For that reason, we will focus on allopatric speciation.
There are two main subtypes of allopatric speciation - these are allopatric and peripatric. The difference is that for peripatric speciation, rather than an existing population being split by the creation of some barrier to gene flow, some portion of a population enters a new area that is geographically isolated from the rest of the population. One very good example of this mode of speciation is island colonization by various organisms. Many islands across the world are formed by volcanism, rising up over many thousands of years to finally break the surface of the ocean. This means that no terrestrial organisms exist there to start out with. Basically, through some process, plants and animals from other islands (or perhaps even the mainland) manage to colonize the new island - since said island is geographically isolated from the original population, over time there will be a divergence.
Out of the two subtypes, allopatric is the most easy to observe in paleontology. This is because we have a good understanding of the movement of tectonic plates through geological time, and thus we can understand how continents moved, mountains formed, sea levels changed, etc. There are mounds of easily observable evidence of this type of speciation throughout organisms in history.
As many of you all know, all of the continents were joined into a single landmass called Pangea during the Triassic period. This meant that any population of terrestrial organisms had relatively continuous gene flow - there were no seas to split up these populations. This is why we see very closely related organisms from Triassic rocks across continents that today are thousands of miles away from each other. An example would be Coelophysis - while Coelophysis bauri is found in the Southwest United States, there are closely related species (sometimes even classified in the same genus) in Africa - this is because at that time, there was little to no isolation.
Throughout the rest of the Mesozoic, the continents began to split up, and we can actually see the effects it had on diversity and speciation over time by looking at species from different stages. In the Late Jurassic, we find species of Allosaurus, Ceratosaurus, and Torosaurus from both the Western United States and from Portugal, because during that time those regions had only just started to split up - the populations had only recently become isolated and as such had not diverged all that much.
Another very cool pattern we see is due to the fact that there was a clear North-South divide in the way the continents split, and this is reflected in the types of Theropods we find on different continents. In the Northern continents such as Asia and North America, Tyrannosauroids dominated as the largest carnivores during the Late Cretaceous, whereas the Abelisaurs dominated the Southern continents at that time. We do not find any Abelisaurs in those Northern continents at that time, nor do we find Tyrannosaurs in the South. However, another note is that we see closely related Tyrannosaurs [and dromaeosaurs] in both Mongolia and Western North America. This is because Asia and North America had only split relatively recently, much more recently than the split that resulted in the North-South divide.
Another interesting thing is that North America was split in two during much of the mid to late Cretaceous by a shallow sea, creating two subcontinents called Laramidia [on the west side] and Appalachia [on the East side]. While we have a rich collection of fossil organisms from Laramidia, there is very little material of that age from Appalachia. Since this sea would have isolated any species that ranged across the continent prior to the rise of sea levels, it is certainly plausible, if not probable, to assume that Appalachia would have been home to organisms somewhat similar to those in Laramidia, but still somewhat distinct. However, until more remains from Appalachia of the relevant age are recovered, we will not know to what extent this is true, if it is at all.
Well, I hope this has helped you learn about the fascinating topic of where species come from! Have a wonderful weekend, everyone!
The reason this relates to last week's post is because in order to understand how a 'species' is formed, we have to have some idea of what a species actually is. Speciation basically involves the splitting of an original, single population of organisms into two new populations, each of which is reproductively isolated from the other. Through some process, whether that is biological or abiotic, this isolation means there is no gene flow between the two populations, leading to independent evolution in each new population. Over time, mutations build up in each lineage, and they become more and more distinct (This could be purely on a genetic level - there don't necessarily have to be any evident morphological differences).
There are two main modes of speciation, defined by the process that split the original population. The first mode, and the one that is the easiest to identify in paleontology, is called allopatric speciation. In allopatric speciation, the ranges of the two new populations do not overlap - one example would be a large mountain range rising within the range of some species, where populations of that species on one side of the range are isolated from the population on the other side due to geographical factors - the species cannot cross that new barrier and as such the population is split.
A second type of speciation that is a bit harder to examine, especially from a paleontological standpoint, is called sympatric speciation. Unlike allopatric speciation, the ranges of the two new populations are not separated geographically - the two populations at least partially overlap at some part of their range. Since observing sympatric speciation relies primarily on genetic/molecular data, it is not exactly an issue that paleontologists can investigate with long-extinct creatures. For that reason, we will focus on allopatric speciation.
There are two main subtypes of allopatric speciation - these are allopatric and peripatric. The difference is that for peripatric speciation, rather than an existing population being split by the creation of some barrier to gene flow, some portion of a population enters a new area that is geographically isolated from the rest of the population. One very good example of this mode of speciation is island colonization by various organisms. Many islands across the world are formed by volcanism, rising up over many thousands of years to finally break the surface of the ocean. This means that no terrestrial organisms exist there to start out with. Basically, through some process, plants and animals from other islands (or perhaps even the mainland) manage to colonize the new island - since said island is geographically isolated from the original population, over time there will be a divergence.
Out of the two subtypes, allopatric is the most easy to observe in paleontology. This is because we have a good understanding of the movement of tectonic plates through geological time, and thus we can understand how continents moved, mountains formed, sea levels changed, etc. There are mounds of easily observable evidence of this type of speciation throughout organisms in history.
As many of you all know, all of the continents were joined into a single landmass called Pangea during the Triassic period. This meant that any population of terrestrial organisms had relatively continuous gene flow - there were no seas to split up these populations. This is why we see very closely related organisms from Triassic rocks across continents that today are thousands of miles away from each other. An example would be Coelophysis - while Coelophysis bauri is found in the Southwest United States, there are closely related species (sometimes even classified in the same genus) in Africa - this is because at that time, there was little to no isolation.
Throughout the rest of the Mesozoic, the continents began to split up, and we can actually see the effects it had on diversity and speciation over time by looking at species from different stages. In the Late Jurassic, we find species of Allosaurus, Ceratosaurus, and Torosaurus from both the Western United States and from Portugal, because during that time those regions had only just started to split up - the populations had only recently become isolated and as such had not diverged all that much.
Another very cool pattern we see is due to the fact that there was a clear North-South divide in the way the continents split, and this is reflected in the types of Theropods we find on different continents. In the Northern continents such as Asia and North America, Tyrannosauroids dominated as the largest carnivores during the Late Cretaceous, whereas the Abelisaurs dominated the Southern continents at that time. We do not find any Abelisaurs in those Northern continents at that time, nor do we find Tyrannosaurs in the South. However, another note is that we see closely related Tyrannosaurs [and dromaeosaurs] in both Mongolia and Western North America. This is because Asia and North America had only split relatively recently, much more recently than the split that resulted in the North-South divide.
Another interesting thing is that North America was split in two during much of the mid to late Cretaceous by a shallow sea, creating two subcontinents called Laramidia [on the west side] and Appalachia [on the East side]. While we have a rich collection of fossil organisms from Laramidia, there is very little material of that age from Appalachia. Since this sea would have isolated any species that ranged across the continent prior to the rise of sea levels, it is certainly plausible, if not probable, to assume that Appalachia would have been home to organisms somewhat similar to those in Laramidia, but still somewhat distinct. However, until more remains from Appalachia of the relevant age are recovered, we will not know to what extent this is true, if it is at all.
Well, I hope this has helped you learn about the fascinating topic of where species come from! Have a wonderful weekend, everyone!
Friday, April 22, 2016
Sci-Day 14: What is a Species?
Happy Sci-Day, everyone! I hope you have all enjoyed this blog so far, at least as much as I have enjoyed writing it! As I've said before, the biggest goal of this blog is to educate people more about the science behind dinosaur battlegrounds, and biology in general (including paleontology in this context). This week, I will be covering one of the most hotly debated topics in modern science - when we talk about a "species", or refer to an organism as a "species", what exactly do we mean? How do we distinguish different species - where do we draw the line from say a subspecies, locality, or individual variation and a full-fledged species?
An important thing to note about a species is that it is fundamentally distinct from other terms that are used in classification, such as family, genus, order, class, etc. The key difference is that the latter terms are arbitrary - a genus is not a defined unit. If you are comparing two genera, for example, and one has more species than another, this does not tell you that the one with more species has evolved or diversified more quickly - there is no strict definition as to what constitutes a genus or any other term besides species - as long as the higher ranks are monophyletic (see Sci-Day #1 for more details on what monophyletic means), it doesn't matter where they are placed on a cladogram or phylogeny. A species, however, is a meaningful and distinct unit - it is a unique population of organisms that is not arbitrary. One of the biggest problems in biology, however, is figuring out how to identify species. This can also be referred to as "the species problem."
This question has no clear or 'right' answer, because the issue is so complex. One scientist named Edward Wiley stated in 1978 that "a species is a single lineage of ancestor-descendant populations which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate" [quote retrieved from Evolutionary Biology lecture]. This essentially means that a species is in some way distinct from other organisms, and its population evolves on its own trajectory - ie, the population may be influenced by changes in environment or other organisms that it interacts with (like in coevolution), but the species does not evolve the exact same changes as the other or evolves in its own unique way. This definition of a species is called the "Evolutionary Species Concept".
There are many different species concepts, all of which have benefits and drawbacks in their application. The most relevant one in paleontology is called the Phenetic [or Morphological] Species Concept. This concept identifies species based on morphological characters such as length of certain bones or other structures, or any observable morphological character. To distinguish species, one can create a chart in "phenotype space", as shown in this image:
First, the character states are graphed in a chart like the one above, and one looks for distinct clusters. In the example above, there appear to be three distinct clusters, which would represent 3 different species.
However, there are several drawbacks to this concept. One issue is choosing characters to analyze. How do we choose what characters to plot? Which characters are important to distinguish species, and which ones are simply representations of variation between localities or individuals? Another drawback is that some species may actually look very similar, but are actually different species (known due to a lack of gene flow between them) - these are called cryptic species. Unfortunately, it is the only species concept that we can use when examining fossil taxa - this could mean that specimens which we all lump into a single species may actually represent several different species - differences between them might have been limited to soft tissue or genetics, which would mean if this were the case we might never even know it. This issue with applying species concepts to modern taxa is also displayed by the fact that the species status of several dinosaurs (including Dracorex, Stygimoloch, Nanotyrannus, and Torosaurus latus) is disputed as being due to ontogenetic variation. If we had fully intact specimens like we have of modern animals, we would be able to tell whether or not these are species in their own right or are just juvenile/adult forms of other species.
Another concept that I will briefly address is one of the most commonly used ones in biology of extant organisms - the Biological Species Concept. the Biological Species Concept says that "species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups" [Quote retrieved from Evolutionary Biology lecture]. Observations that led to the formulation of this concept include variation within populations, sexual dimorphisms, life cycle (some organisms display extreme morphological changes in development), geographic variation, and cryptic species [as described above]. While this is beneficial due to addressing some of the limitations of the Phenetic Species Concept, it too has its drawbacks.
Drawbacks of the BSC are mostly related to the issue of 'reproductive isolation'. How can we determine the species boundaries of animals if we have no data on their reproductive habits or capabilities? Another issue is that occasionally, two species might interbreed and hybridize, which would mean they are the same species if one takes the BSC at face value. However, if this is only occasional and the populations seem to represent distinct species in all practical purposes, should we really lump them together? Additionally, many times the offspring of these hybridizations are nonviable or infertile - meaning that they are an evolutionary dead end. What do we do in these cases? This is a conundrum that the BSC has trouble answering.
I have only talked about two commonly used Species Concepts, but there are many more, each with their own pros and cons. I do not have time to talk about all of them in detail, but if you are interested you can find plenty of information about them on the good ol' internet! I hope that this post has educated you a bit more on a very hotly debated topic that we may never truly have an answer for!
A special thanks to my professors in Evolutionary Biology, as their lectures are very helpful for providing good quotes and other useful information!
An important thing to note about a species is that it is fundamentally distinct from other terms that are used in classification, such as family, genus, order, class, etc. The key difference is that the latter terms are arbitrary - a genus is not a defined unit. If you are comparing two genera, for example, and one has more species than another, this does not tell you that the one with more species has evolved or diversified more quickly - there is no strict definition as to what constitutes a genus or any other term besides species - as long as the higher ranks are monophyletic (see Sci-Day #1 for more details on what monophyletic means), it doesn't matter where they are placed on a cladogram or phylogeny. A species, however, is a meaningful and distinct unit - it is a unique population of organisms that is not arbitrary. One of the biggest problems in biology, however, is figuring out how to identify species. This can also be referred to as "the species problem."
This question has no clear or 'right' answer, because the issue is so complex. One scientist named Edward Wiley stated in 1978 that "a species is a single lineage of ancestor-descendant populations which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate" [quote retrieved from Evolutionary Biology lecture]. This essentially means that a species is in some way distinct from other organisms, and its population evolves on its own trajectory - ie, the population may be influenced by changes in environment or other organisms that it interacts with (like in coevolution), but the species does not evolve the exact same changes as the other or evolves in its own unique way. This definition of a species is called the "Evolutionary Species Concept".
There are many different species concepts, all of which have benefits and drawbacks in their application. The most relevant one in paleontology is called the Phenetic [or Morphological] Species Concept. This concept identifies species based on morphological characters such as length of certain bones or other structures, or any observable morphological character. To distinguish species, one can create a chart in "phenotype space", as shown in this image:
However, there are several drawbacks to this concept. One issue is choosing characters to analyze. How do we choose what characters to plot? Which characters are important to distinguish species, and which ones are simply representations of variation between localities or individuals? Another drawback is that some species may actually look very similar, but are actually different species (known due to a lack of gene flow between them) - these are called cryptic species. Unfortunately, it is the only species concept that we can use when examining fossil taxa - this could mean that specimens which we all lump into a single species may actually represent several different species - differences between them might have been limited to soft tissue or genetics, which would mean if this were the case we might never even know it. This issue with applying species concepts to modern taxa is also displayed by the fact that the species status of several dinosaurs (including Dracorex, Stygimoloch, Nanotyrannus, and Torosaurus latus) is disputed as being due to ontogenetic variation. If we had fully intact specimens like we have of modern animals, we would be able to tell whether or not these are species in their own right or are just juvenile/adult forms of other species.
Another concept that I will briefly address is one of the most commonly used ones in biology of extant organisms - the Biological Species Concept. the Biological Species Concept says that "species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups" [Quote retrieved from Evolutionary Biology lecture]. Observations that led to the formulation of this concept include variation within populations, sexual dimorphisms, life cycle (some organisms display extreme morphological changes in development), geographic variation, and cryptic species [as described above]. While this is beneficial due to addressing some of the limitations of the Phenetic Species Concept, it too has its drawbacks.
Drawbacks of the BSC are mostly related to the issue of 'reproductive isolation'. How can we determine the species boundaries of animals if we have no data on their reproductive habits or capabilities? Another issue is that occasionally, two species might interbreed and hybridize, which would mean they are the same species if one takes the BSC at face value. However, if this is only occasional and the populations seem to represent distinct species in all practical purposes, should we really lump them together? Additionally, many times the offspring of these hybridizations are nonviable or infertile - meaning that they are an evolutionary dead end. What do we do in these cases? This is a conundrum that the BSC has trouble answering.
I have only talked about two commonly used Species Concepts, but there are many more, each with their own pros and cons. I do not have time to talk about all of them in detail, but if you are interested you can find plenty of information about them on the good ol' internet! I hope that this post has educated you a bit more on a very hotly debated topic that we may never truly have an answer for!
A special thanks to my professors in Evolutionary Biology, as their lectures are very helpful for providing good quotes and other useful information!
Friday, April 15, 2016
Sci-Day 13: Sexual Selection
Hello, everyone! This week, I'm going to talk about a specific mechanism of evolution that can shape species in many different ways - sexual selection. One thing to keep in mind while reading this is that it is incredibly difficult, if not impossible to tell the sex of a fossil organism in the vast majority of cases, so even if there are two distinct morphs of a species it is not necessarily possible to tell whether it is due to sexual dimorphism, geographical variation, or some other factor. However, there are some features in many groups of fossil organisms that seem to have played some role in mating behaviors and displays, and sexual selection may have helped to shape their development.
One of the key requirements for sexual selection is anisogamy - this means that one sex produces small gametes, and the other sex produces large gametes. Biologically, this is how we can assign male or female - it is not the presence of a certain chromosome (not all creatures share the same sex chromosome system, and some species have temperature-dependent sex determination), but rather the size of the gametes they produce that defines their sex. Males produce the smaller gametes, and females produce the larger gametes. Since these two gametes are very distinct, selection can favor different traits in males and females.
One of the very important things about the size difference is that the larger gametes (eggs) are MUCH more expensive to produce than smaller gametes (sperm), and as such they are a limiting resource. For this reason, females are often much "choosier" than males - they stand to lose far more fitness than males by making bad mate choices (a male can easily produce more sperm if he makes a bad choice, it costs far more for the female to make more eggs).
As you may have noticed as you've read this, sexual selection is a logical equivalent to natural selection. Heritable traits in males that increase mating success should increase in frequency, whereas heritable traits that decrease mating success should decrease. These traits may be elegant displays, horns or spikes to fight off other males, or simply a high sperm count.
There are two subtypes of sexual selection. These two types are called intrasexual selection and intersexual selection:
Intrasexual selection is the result of interactions between individuals of the same sex. One of the most easily observed examples are those that happen before copulation. In these scenarios, there is competition between individuals of the same sex for mating opportunities (often males). Examples of traits that may be favored by this type of sexual selection are visual displays, traits that make the animal look larger, horns/tusks [or other features] used for physical confrontation, and features that help to establish dominance such as coloration or vocalizations.
Intersexual selection is the result of interactions between individuals of the opposite sex. In these scenarios, one sex preferentially mates with individuals of some specific phenotype, and consequentially those individuals displaying said phenotype produce more offspring. Examples of features that may be favored by intersexual selection include vivid color patterns/ornamentation, vocalizations, and display behaviors.
As I stated above, it is unfortunately very difficult to distinguish sexes of fossil animals, and as such we can not always determine whether or not there was sexual selection occurring. For example, it was originally hypothesized that the crests on species such as Dilophosaurus were used to attract mates, but due to the fact that there is no evidence of sexual dimorphism in the species (and even if there was, it would be very difficult to be sure), it is considered more likely that they were used for species recognition.
However, there are some species that show evidence of specialized features that may have been at least partially shaped by sexual selection. One such example are the frills and horns of Triceratops. There is considerable evidence that Triceratops engaged in non-fatal intraspecific combat (Petersen et al., 2013; Reid, 1997; Horner and Goodwin, 2009; Horner and Lamm, 2011; Farlow and Dodson, 1975), though we do not know if this was based on competition for mates - if one were to identify all individuals showing cranial pathologies linked to such combat as the same sex, that might reinforce the idea that sexual selection played a role, but the behavior could also be unrelated to mating and simply be a way of settling territorial disputes. Triceratops frills apparently began to develop at a young age (before the onset of sexual maturity), and were likely also used for display and species recognition (Goodwin et al., 2006). Whether the display was simply shape or if there were vivid colors is unknown, though if the idea of sexual selection playing a role in the evolution of frills and horns is correct, there may have been distinct colors patterning that area to help attract mates.
Additionally, as I talked about in my Creature Feature about Pachycephalosaurus, there is similar evidence for headbutting behavior in that species. Like with Triceratops, it is not known whether or not this behavior was based on competition for mates, or if it was simply a way of settling territorial disputes (or both), but the idea is the same.
To sum it up, sexual selection is a very important driver in the development of many features as observed in modern taxa, and I personally believe it is safe to assume that it played some role in the evolution of prehistoric creatures as well. However, the difficulty of sexing fossil animals and the lack of preservation of soft tissues such as non-bony crests/flaps or vivid colors means that even if it did play a role, it would be very difficult if not impossible to say so with any great degree of certainty. Dinosaur Battlegrounds could help to investigate the possibility of sexual selection playing a role in the evolution of certain animals by running simulations with different AI behaviors specifically regarding mating preferences/behaviors in one [or both] sexes, and see whether or not the results match existing data. This is yet another example of how Dinosaur Battlegrounds' nature as a full paleoecosystem restoration can help us answer questions that we cannot uncover from the rocks.
I hope you enjoyed this week's Sci-Day! I'd like to thank my Evolutionary Biology professors for providing great lecture materials that I could use to help organize this post.
Acknowledgements:
Peterson, J. E.; Dischler, C.; Longrich, N. R. 2013. Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae). PLoS ONE 8 (7): e86820.
Reid, R. E. H. 1997. Histology of bones and teeth. In: Currie, P. J. and Padian, K, editors. Encyclopedia of Dinosaurs. Academic Press, San Diego, CA. 329-339.
Horner, J. R.; Goodwin, M. B. 2009. Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus. PLoS ONE 4 (10): e7626.
Horner, J. R.; Lamm, E. 2011. Ontogeny of the parietal frill of Triceratops: a preliminary histological analysis. Comptes Rendus Palevol 10: 439-452.
Farlow, J. O.; Dodson, P. 1975. The behavioral significance of frill and horn morphology in ceratopsian dinosaurs. Evolution 29: 353-361.
Goodwin, M. B.; Clemens, W. A.; Horner, J. R.; Padian, K. 2006. The smallest known Triceratops skull: new observations on ceratopsid cranial anatomy and ontogeny. Journal of Vertebrate Paleontology 26 (1): 103.
One of the key requirements for sexual selection is anisogamy - this means that one sex produces small gametes, and the other sex produces large gametes. Biologically, this is how we can assign male or female - it is not the presence of a certain chromosome (not all creatures share the same sex chromosome system, and some species have temperature-dependent sex determination), but rather the size of the gametes they produce that defines their sex. Males produce the smaller gametes, and females produce the larger gametes. Since these two gametes are very distinct, selection can favor different traits in males and females.
One of the very important things about the size difference is that the larger gametes (eggs) are MUCH more expensive to produce than smaller gametes (sperm), and as such they are a limiting resource. For this reason, females are often much "choosier" than males - they stand to lose far more fitness than males by making bad mate choices (a male can easily produce more sperm if he makes a bad choice, it costs far more for the female to make more eggs).
As you may have noticed as you've read this, sexual selection is a logical equivalent to natural selection. Heritable traits in males that increase mating success should increase in frequency, whereas heritable traits that decrease mating success should decrease. These traits may be elegant displays, horns or spikes to fight off other males, or simply a high sperm count.
There are two subtypes of sexual selection. These two types are called intrasexual selection and intersexual selection:
Intrasexual selection is the result of interactions between individuals of the same sex. One of the most easily observed examples are those that happen before copulation. In these scenarios, there is competition between individuals of the same sex for mating opportunities (often males). Examples of traits that may be favored by this type of sexual selection are visual displays, traits that make the animal look larger, horns/tusks [or other features] used for physical confrontation, and features that help to establish dominance such as coloration or vocalizations.
Intersexual selection is the result of interactions between individuals of the opposite sex. In these scenarios, one sex preferentially mates with individuals of some specific phenotype, and consequentially those individuals displaying said phenotype produce more offspring. Examples of features that may be favored by intersexual selection include vivid color patterns/ornamentation, vocalizations, and display behaviors.
As I stated above, it is unfortunately very difficult to distinguish sexes of fossil animals, and as such we can not always determine whether or not there was sexual selection occurring. For example, it was originally hypothesized that the crests on species such as Dilophosaurus were used to attract mates, but due to the fact that there is no evidence of sexual dimorphism in the species (and even if there was, it would be very difficult to be sure), it is considered more likely that they were used for species recognition.
However, there are some species that show evidence of specialized features that may have been at least partially shaped by sexual selection. One such example are the frills and horns of Triceratops. There is considerable evidence that Triceratops engaged in non-fatal intraspecific combat (Petersen et al., 2013; Reid, 1997; Horner and Goodwin, 2009; Horner and Lamm, 2011; Farlow and Dodson, 1975), though we do not know if this was based on competition for mates - if one were to identify all individuals showing cranial pathologies linked to such combat as the same sex, that might reinforce the idea that sexual selection played a role, but the behavior could also be unrelated to mating and simply be a way of settling territorial disputes. Triceratops frills apparently began to develop at a young age (before the onset of sexual maturity), and were likely also used for display and species recognition (Goodwin et al., 2006). Whether the display was simply shape or if there were vivid colors is unknown, though if the idea of sexual selection playing a role in the evolution of frills and horns is correct, there may have been distinct colors patterning that area to help attract mates.
Additionally, as I talked about in my Creature Feature about Pachycephalosaurus, there is similar evidence for headbutting behavior in that species. Like with Triceratops, it is not known whether or not this behavior was based on competition for mates, or if it was simply a way of settling territorial disputes (or both), but the idea is the same.
To sum it up, sexual selection is a very important driver in the development of many features as observed in modern taxa, and I personally believe it is safe to assume that it played some role in the evolution of prehistoric creatures as well. However, the difficulty of sexing fossil animals and the lack of preservation of soft tissues such as non-bony crests/flaps or vivid colors means that even if it did play a role, it would be very difficult if not impossible to say so with any great degree of certainty. Dinosaur Battlegrounds could help to investigate the possibility of sexual selection playing a role in the evolution of certain animals by running simulations with different AI behaviors specifically regarding mating preferences/behaviors in one [or both] sexes, and see whether or not the results match existing data. This is yet another example of how Dinosaur Battlegrounds' nature as a full paleoecosystem restoration can help us answer questions that we cannot uncover from the rocks.
I hope you enjoyed this week's Sci-Day! I'd like to thank my Evolutionary Biology professors for providing great lecture materials that I could use to help organize this post.
Acknowledgements:
Peterson, J. E.; Dischler, C.; Longrich, N. R. 2013. Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae). PLoS ONE 8 (7): e86820.
Reid, R. E. H. 1997. Histology of bones and teeth. In: Currie, P. J. and Padian, K, editors. Encyclopedia of Dinosaurs. Academic Press, San Diego, CA. 329-339.
Horner, J. R.; Goodwin, M. B. 2009. Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus. PLoS ONE 4 (10): e7626.
Horner, J. R.; Lamm, E. 2011. Ontogeny of the parietal frill of Triceratops: a preliminary histological analysis. Comptes Rendus Palevol 10: 439-452.
Farlow, J. O.; Dodson, P. 1975. The behavioral significance of frill and horn morphology in ceratopsian dinosaurs. Evolution 29: 353-361.
Goodwin, M. B.; Clemens, W. A.; Horner, J. R.; Padian, K. 2006. The smallest known Triceratops skull: new observations on ceratopsid cranial anatomy and ontogeny. Journal of Vertebrate Paleontology 26 (1): 103.
Friday, April 8, 2016
Sci-Day 12: The K-T Extinction Event
Happy Sci-Day, everyone! This week, I will be writing about one of the most tragic events in Earth's history. This event spelled the doom of many creatures, with non-avian dinosaurs among the casualties. Reading about this catastrophic time in history always makes me feel a bit sad - as a herpetology enthusiast, the Mesozoic represents a golden age for reptiles. In the Mesozoic, you could go to any ecosystem and almost universally the largest animal present would be a reptile. In the sky, you had pterosaurs - in the sea, there were the plesiosaurs and mosasaurs, and of course there were dinosaurs on the land. All of these groups were completely extinguished by this event - I would give almost anything to be able to travel back and study such creatures in the same way that I can study extant taxa.
The K-T extinction event marks the end of the Cretaceous period and the close of the Mesozoic Era. It also marks the beginning of the Paleocene period and Cenozoic Era, the latter of which continues today. While older estimates date this event at 65 million years ago, more recent estimates have revised this to around 66 million years (Renne et al., 2013).
One of the most common hypotheses for the cause of the K-T extinction is that it was triggered by a large comet or asteroid impact. Such an impact would have caused devastation on a global scale - the effect would be like nuclear winter on steroids. With all the debris and dust from the collision blocking out much of the sun's light and warmth, plants and phytoplankton would find it all but impossible to undergo photosynthesis (Alvarez et al., 1980), leading to widespread plant death and subsequent food chain collapse. In the 1990s, this hypothesis was further supported by the discovery of a 180-km wide impact crater (dubbed the Chicxulub crater) in the Yucatan peninsula (Hildebrand et al., 1991). Additionally, there is a thin layer of sediment marking the KT event (known as the 'KT boundary) present in all sedimentary rocks of the relevant age. This sediment shows high concentrations of iridium - this metal is rare in the Earth's crust, but is common in asteroids. This fact could mean that the KT boundary layer represents deposit of debris from the impact (Schulte et al., 2010). Furthermore, the fact that there is the fact that the extinctions seem to have happened around the same time as the impact, which is interpreted by some as strong situational evidence for this hypothesis.
While this hypothesis is generally accepted as the event that caused the demise of the non-avian dinosaurs [as well as many other groups of organisms], it is still a somewhat controversial issue. Some have actually argued that the extinction of non-avian dinosaurs was more gradual than some might claim, and both sides of the debate have support from the fossil record. A study of 29 fossil sites in Europe revealed that dinosaurs had significant diversity up until the KT event, with over 100 species present across the sampled sites (Riera et al., 2010) - this appears to support the hypothesis of a sudden extinction. Additionally, further research suggested that global non-Avian dinosaur diversity was significantly higher, with somewhere between 678 and 1078 species existing up until the event (Le Loeuff, 2012). However, there is evidence of a gradual decrease in non-avian dinosaur species richness at some fossil sites - a study of fossil-bearing rocks along the Red Deer River in Alberta shows that the number of species declined from roughly 45 to around 12 over the course of 10 million years (Ryan et al., 2001). If this is indeed true and is not due to differing preservation potentials of the sediment with age, it seems to support the gradual extinction hypothesis of non-avian dinosaurs. One possibility is that dinosaurs were gradually on the decline in some parts of the world, while they continued to thrive in other regions. However, without more data/evidence, we will not know for sure.
Dinosaurs were not the only group affected by the KT event. Many groups of squamates such as monstersaurs and polyglyphanodonts were nearly wiped out by the event, taking 10 million years to recover (Longrich et al., 2012). Additionally, both mosasaurs and plesiosaurs died out (Chattergee and Small, 1989). Mosasaurs and plesiosaurs were the apex marine predators of their time, growing to truly immense proportions. It is truly a pity that they are no longer with us.
The K-T extinction also spelled the end for the last pterosaurs. By the end of the Cretaceous, the only family definitely present was the Azhdarchidae; while there is some evidence of other families, the remains are far too fragmentary to assign them to any specific groups (Barrett et al., 2008). Evidence seems to suggest that pterosaurs were on the decline at the time, while modern families of birds were simultaneously increasing in diversity. While it was originally thought that this increase was indicative of birds 'replacing' pterosaurs due to interspecific competition or by filling niches left empty by the disappearance of pterosaur species (Robertson et al., 2004), the correlation between pterosaur diversity decline and bird diversity increase is simply not conclusive to the competition hypothesis (Butler et al., 2009). Additionally, there were small pterosaurs during the Late Cretaceous (Prondvai et al., 2014), further disputing the idea of direct competition.
I hope that this has given you a bit of a better understanding of the K-T extinction! While many groups of taxa were devastated in addition to the non-avian dinosaurs, it would take far too much time and space for me to go into any great depth on all of them. If you are interested in learning more, I encourage you to find resources online such as Google Scholar to read more about this subject!
Acknowledgements:
Renne, Paul R.; Deino, Alan L.; Hilgen, Frederik J.; Kuiper, Klaudia F.; Mark, Darren F.; Mitchell, William S.; Morgan, Leah E.; Mundil, Roland; Smit, Jan. 7 February, 2013. Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary. Science 339 (6120): 684-687.
Alvarez, Luis. W.; Alvarez, Walter; Asaro, Frank; Michel, Helen V. 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208 (4448): 1095-1108.
Schulte, Peter. March 5, 2010. The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science (American Association for the Advancement of Science) 327 (5970): 1214-1218.
Riera, V.; Marmi, J.; Oms, O.; Gomez, B. March 2010. Orientated plant fragments revealing tidal palaeocurrents in the Fumanya mudflat (Maastrichtian, southern Pyrenees): Insights in palaeogeographic reconstructions. Palaeogeography, Palaeoclimatology, Palaeoecology 288 (1-4): 82-92.
Le Loeuff, J. 2012. Paleobiogeography and biodiversity of Late Maastrichtian dinosaurs: how many dinosaur species went extinct at the Cretaceous-Tertiary boundary? Bulletin de la Société Géologique de France 183 (6): 547-559.
Ryan, M. J.; Russell, A. P.; Eberth, D. A.; Currie, P. J.. 2001. The taphonomy of a Centrosaurus (Ornithischia: Ceratopsidae) bone bed from the Dinosaur Park Formation (Upper Campanian), Alberta, Canada, with comments on cranial ontogeny. PALAIOS 16 (5): 482-506.
Longrich, Nicholas R.; Bhullar, Bhart-Anjan S.; Gauthier, Jacques A. 2012. Mass extinction of lizards and snakes at the Cretaceous-Paleogene boundary. Proceedings of the National Academy of Sciences of the United States of America 109 (52): 21396-21401.
Chatterjee, S.; Small, B. J. 1989. New plesiosaurs from the Upper Cretaceous of Antarctica. Geological Society, London, Special Publications 47 (1): 197-215.
Barrett, P. M.; Butler, R. J.; Edwards, N. P.; Milner, A. R. 2008. Pterosaur distribution in time and space: an atlas. Zitteliana 28: 61-107.
Robertson, D. S.; McKenna, M. C.; Toon, O. B.; Lillegraven, J. A. 2004. Survival in the first hours of the Cenozoic. GSA Bulletin 116 (5-6): 760-768.
Butler, Richard J.; Barrett, Paul M.; Nowbath, Stephen; Upchurch, Paul. 2009. Estimating the effects of sampling biases on pterosaur diversity patterns: implications for hypotheses of bird/pterosaur competitive replacement. Paleobiology 35 (3): 432-446.
Prondvai, E.; Bodor, E. R.; Ősi, A. 2014. Does morphology reflect osteohistology-based ontogeny? A case study of Late Cretaceous pterosaur jaw symphyses from Hungary reveals hidden taxonomic diversity. Paleobiology 40: 288-321.
The K-T extinction event marks the end of the Cretaceous period and the close of the Mesozoic Era. It also marks the beginning of the Paleocene period and Cenozoic Era, the latter of which continues today. While older estimates date this event at 65 million years ago, more recent estimates have revised this to around 66 million years (Renne et al., 2013).
One of the most common hypotheses for the cause of the K-T extinction is that it was triggered by a large comet or asteroid impact. Such an impact would have caused devastation on a global scale - the effect would be like nuclear winter on steroids. With all the debris and dust from the collision blocking out much of the sun's light and warmth, plants and phytoplankton would find it all but impossible to undergo photosynthesis (Alvarez et al., 1980), leading to widespread plant death and subsequent food chain collapse. In the 1990s, this hypothesis was further supported by the discovery of a 180-km wide impact crater (dubbed the Chicxulub crater) in the Yucatan peninsula (Hildebrand et al., 1991). Additionally, there is a thin layer of sediment marking the KT event (known as the 'KT boundary) present in all sedimentary rocks of the relevant age. This sediment shows high concentrations of iridium - this metal is rare in the Earth's crust, but is common in asteroids. This fact could mean that the KT boundary layer represents deposit of debris from the impact (Schulte et al., 2010). Furthermore, the fact that there is the fact that the extinctions seem to have happened around the same time as the impact, which is interpreted by some as strong situational evidence for this hypothesis.
While this hypothesis is generally accepted as the event that caused the demise of the non-avian dinosaurs [as well as many other groups of organisms], it is still a somewhat controversial issue. Some have actually argued that the extinction of non-avian dinosaurs was more gradual than some might claim, and both sides of the debate have support from the fossil record. A study of 29 fossil sites in Europe revealed that dinosaurs had significant diversity up until the KT event, with over 100 species present across the sampled sites (Riera et al., 2010) - this appears to support the hypothesis of a sudden extinction. Additionally, further research suggested that global non-Avian dinosaur diversity was significantly higher, with somewhere between 678 and 1078 species existing up until the event (Le Loeuff, 2012). However, there is evidence of a gradual decrease in non-avian dinosaur species richness at some fossil sites - a study of fossil-bearing rocks along the Red Deer River in Alberta shows that the number of species declined from roughly 45 to around 12 over the course of 10 million years (Ryan et al., 2001). If this is indeed true and is not due to differing preservation potentials of the sediment with age, it seems to support the gradual extinction hypothesis of non-avian dinosaurs. One possibility is that dinosaurs were gradually on the decline in some parts of the world, while they continued to thrive in other regions. However, without more data/evidence, we will not know for sure.
Dinosaurs were not the only group affected by the KT event. Many groups of squamates such as monstersaurs and polyglyphanodonts were nearly wiped out by the event, taking 10 million years to recover (Longrich et al., 2012). Additionally, both mosasaurs and plesiosaurs died out (Chattergee and Small, 1989). Mosasaurs and plesiosaurs were the apex marine predators of their time, growing to truly immense proportions. It is truly a pity that they are no longer with us.
The K-T extinction also spelled the end for the last pterosaurs. By the end of the Cretaceous, the only family definitely present was the Azhdarchidae; while there is some evidence of other families, the remains are far too fragmentary to assign them to any specific groups (Barrett et al., 2008). Evidence seems to suggest that pterosaurs were on the decline at the time, while modern families of birds were simultaneously increasing in diversity. While it was originally thought that this increase was indicative of birds 'replacing' pterosaurs due to interspecific competition or by filling niches left empty by the disappearance of pterosaur species (Robertson et al., 2004), the correlation between pterosaur diversity decline and bird diversity increase is simply not conclusive to the competition hypothesis (Butler et al., 2009). Additionally, there were small pterosaurs during the Late Cretaceous (Prondvai et al., 2014), further disputing the idea of direct competition.
I hope that this has given you a bit of a better understanding of the K-T extinction! While many groups of taxa were devastated in addition to the non-avian dinosaurs, it would take far too much time and space for me to go into any great depth on all of them. If you are interested in learning more, I encourage you to find resources online such as Google Scholar to read more about this subject!
Acknowledgements:
Renne, Paul R.; Deino, Alan L.; Hilgen, Frederik J.; Kuiper, Klaudia F.; Mark, Darren F.; Mitchell, William S.; Morgan, Leah E.; Mundil, Roland; Smit, Jan. 7 February, 2013. Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary. Science 339 (6120): 684-687.
Alvarez, Luis. W.; Alvarez, Walter; Asaro, Frank; Michel, Helen V. 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208 (4448): 1095-1108.
Schulte, Peter. March 5, 2010. The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science (American Association for the Advancement of Science) 327 (5970): 1214-1218.
Riera, V.; Marmi, J.; Oms, O.; Gomez, B. March 2010. Orientated plant fragments revealing tidal palaeocurrents in the Fumanya mudflat (Maastrichtian, southern Pyrenees): Insights in palaeogeographic reconstructions. Palaeogeography, Palaeoclimatology, Palaeoecology 288 (1-4): 82-92.
Le Loeuff, J. 2012. Paleobiogeography and biodiversity of Late Maastrichtian dinosaurs: how many dinosaur species went extinct at the Cretaceous-Tertiary boundary? Bulletin de la Société Géologique de France 183 (6): 547-559.
Ryan, M. J.; Russell, A. P.; Eberth, D. A.; Currie, P. J.. 2001. The taphonomy of a Centrosaurus (Ornithischia: Ceratopsidae) bone bed from the Dinosaur Park Formation (Upper Campanian), Alberta, Canada, with comments on cranial ontogeny. PALAIOS 16 (5): 482-506.
Longrich, Nicholas R.; Bhullar, Bhart-Anjan S.; Gauthier, Jacques A. 2012. Mass extinction of lizards and snakes at the Cretaceous-Paleogene boundary. Proceedings of the National Academy of Sciences of the United States of America 109 (52): 21396-21401.
Chatterjee, S.; Small, B. J. 1989. New plesiosaurs from the Upper Cretaceous of Antarctica. Geological Society, London, Special Publications 47 (1): 197-215.
Barrett, P. M.; Butler, R. J.; Edwards, N. P.; Milner, A. R. 2008. Pterosaur distribution in time and space: an atlas. Zitteliana 28: 61-107.
Robertson, D. S.; McKenna, M. C.; Toon, O. B.; Lillegraven, J. A. 2004. Survival in the first hours of the Cenozoic. GSA Bulletin 116 (5-6): 760-768.
Butler, Richard J.; Barrett, Paul M.; Nowbath, Stephen; Upchurch, Paul. 2009. Estimating the effects of sampling biases on pterosaur diversity patterns: implications for hypotheses of bird/pterosaur competitive replacement. Paleobiology 35 (3): 432-446.
Prondvai, E.; Bodor, E. R.; Ősi, A. 2014. Does morphology reflect osteohistology-based ontogeny? A case study of Late Cretaceous pterosaur jaw symphyses from Hungary reveals hidden taxonomic diversity. Paleobiology 40: 288-321.
Friday, April 1, 2016
Sci-Day 11: The Scientific Core of Dinosaur Battlegrounds
Happy Sci-Day, fans! I'm sorry for missing two weeks of Sci-Day posts, but my schedule was unable to fit them in unless I tried to rush it, and I will not sacrifice the quality of what I write for the sake of a deadline. This post is based on the presentation I made at the KU Herpetology division last Friday, and in this I have attempted to explain how and why Dinosaur Battlegrounds utilizes science and could be a valuable tool to anyone wishing to better understand the prehistoric world. I hope you all enjoy, and I hope it will give you a deeper insight into what makes our vision so special.
As has been said before, Dinosaur Battlegrounds will simulate a dynamic, living environment. There will be day/night cycle, natural disasters such as flash floods, and aging flora and fauna. These effects simulate the natural processes that occur in any living system, and with enough trials and running time this allows one to observe trends in populations of different species while still accounting for stochastic processes that could otherwise undermine the validity of the data. This, however, relies on our ability to accurately reconstruct the flora and fauna of the paleoecosystem as accurately as possible. To do this, we must carefully examine all of the current scientific evidence. It also means that when there are two or more conflicting but equally plausible hypotheses for a certain aspect of the ecosystem or the biota residing within it, we must represent both in the game and allow the player to decide which they want to go by. This also provides a possible way for testing the validity of these hypotheses in an actual living environment, which may give new insights into the issue that had not been accounted for previously.
However, Dinosaur Battlegrounds involves other fields in addition to paleontology. We must actively consult with herpetologists, ichthyologists, ornithologists, and other scientists who study living taxa due to the fact that we are attempting to restore not only the living tissues of the animals, but also their behavior. One of the best way to infer possible behaviors or to infer the overall anatomy of fragmentary specimens is to look at their closest extant relatives, and make inferences using comparative anatomy. There are many other types of information that are not fossilized, such as diet (though this can be somewhat inferred from dentition), ecological niche, etc. Perhaps most importantly, there are many species of animal from the Hell Creek formation that are known only from extremely fragmentary remains - far too fragmentary to restore the rest of the anatomy by itself. In such cases, it is very useful to look at inferred relations to extant taxa, and to use those to attempt a restoration. One example of this is Palaeosaniwa - the missing parts were restored based on its closest modern relatives (Heloderma, according to Balsai, 2001), and in-game, its behavior will largely use knowledge of Heloderma and other related Platynotans.
In fact, almost all of the Polyglyphanodonts from Hell Creek are based on very small fragments of the dentary, making it impossible to make a full restoration based exclusively on fossil remains. In such cases, we use what I call "placeholder models" - these are models meant to represent the actual creatures, since they obviously played a role in the ecosystem, but are based mostly on modern taxa in terms of appearance. This allows us to still have the species present even though we cannot have a fully fossil-based restoration. They are called "placeholders" because as soon as there is sufficient remains of such species to make a fossil-based reconstruction, new models will be made and will subsequently replace the originals. We also use similar models to represent types of creatures that we can reasonably infer to have been present, but are not known from any body fossils. These are things such as various invertebrates (both terrestrial and aquatic) - these can be inferred based on the dentition of many Hell Creek animals supporting a diet comprised of such creatures, and various things such as molecular evolution data from those taxa supporting an evolutionary history implying their presence in certain regions at certain times.
Another example of where science fits in has been mentioned in a previous Sci-Day post, so I will not go into too much detail. We are basing the dynamics of our feeding system on the inferred metabolic rates and relative energy content per unit mass of different types of food. This further ensures the accuracy of our simulation, and also requires involvement of scientists studying living taxa since it is not possible to directly measure metabolic rates from fossils.
Perhaps one of the most important reasons why Dinosaur Battlegrounds is so amazing and important is the ideas for potential research. One idea was mentioned in the Dinosaur Metabolism Sci-Day post, and I have actually been discussing the possibility of doing that project with a professor here at my university. A related project relates to getting FEE values to use for non-dinosaur taxa, such as the reptiles, amphibians, and fish that lived in Hell Creek. These could be estimated based on data from their closest living relatives (ie for Amia fragosa and Melvius thomasi the FEE values would be based on modern Amiid fish). This gives scientists the opportunity to gather data on these species that could also be useful to studies that are not directly related to Dinosaur Battlegrounds, further increasing our positive impact on the scientific community.
Additionally, as has been mentioned many times before, Dinosaur Battlegrounds is not just a game - it can act as a simulation software that could be used to test hypotheses about many different aspects of a paleoecosystem. In many ways, it functions like any other model or simulation - if, for example, a hypothesized species distribution is unstable, the population might die off entirely, or simply settle into a completely different distribution that allows for a stable population. This is due to the integration of naturally occurring stochastic processes that are very hard to fully account for in current models/software used for this purpose. Such aspects of a paleoecosystem are extremely difficult to examine, as things such as fecundity and average population size in a given region cannot be measured in the same way as with extant flora and fauna.
Lastly, there are also many secondary benefits that contribute to the massive impact Dinosaur Battlegrounds will have:
References:
Balsai, Michael Joseph. 2001. The phylogenetic position of Palaeosaniwa and the early evolution of the Platynotan (Varanoid) anguimorphs (January 1, 2001). Dissertations available from ProQuest. Paper AAI3031637. http://repository.upenn.edu/dissertations/AAI3031637
As has been said before, Dinosaur Battlegrounds will simulate a dynamic, living environment. There will be day/night cycle, natural disasters such as flash floods, and aging flora and fauna. These effects simulate the natural processes that occur in any living system, and with enough trials and running time this allows one to observe trends in populations of different species while still accounting for stochastic processes that could otherwise undermine the validity of the data. This, however, relies on our ability to accurately reconstruct the flora and fauna of the paleoecosystem as accurately as possible. To do this, we must carefully examine all of the current scientific evidence. It also means that when there are two or more conflicting but equally plausible hypotheses for a certain aspect of the ecosystem or the biota residing within it, we must represent both in the game and allow the player to decide which they want to go by. This also provides a possible way for testing the validity of these hypotheses in an actual living environment, which may give new insights into the issue that had not been accounted for previously.
However, Dinosaur Battlegrounds involves other fields in addition to paleontology. We must actively consult with herpetologists, ichthyologists, ornithologists, and other scientists who study living taxa due to the fact that we are attempting to restore not only the living tissues of the animals, but also their behavior. One of the best way to infer possible behaviors or to infer the overall anatomy of fragmentary specimens is to look at their closest extant relatives, and make inferences using comparative anatomy. There are many other types of information that are not fossilized, such as diet (though this can be somewhat inferred from dentition), ecological niche, etc. Perhaps most importantly, there are many species of animal from the Hell Creek formation that are known only from extremely fragmentary remains - far too fragmentary to restore the rest of the anatomy by itself. In such cases, it is very useful to look at inferred relations to extant taxa, and to use those to attempt a restoration. One example of this is Palaeosaniwa - the missing parts were restored based on its closest modern relatives (Heloderma, according to Balsai, 2001), and in-game, its behavior will largely use knowledge of Heloderma and other related Platynotans.
In fact, almost all of the Polyglyphanodonts from Hell Creek are based on very small fragments of the dentary, making it impossible to make a full restoration based exclusively on fossil remains. In such cases, we use what I call "placeholder models" - these are models meant to represent the actual creatures, since they obviously played a role in the ecosystem, but are based mostly on modern taxa in terms of appearance. This allows us to still have the species present even though we cannot have a fully fossil-based restoration. They are called "placeholders" because as soon as there is sufficient remains of such species to make a fossil-based reconstruction, new models will be made and will subsequently replace the originals. We also use similar models to represent types of creatures that we can reasonably infer to have been present, but are not known from any body fossils. These are things such as various invertebrates (both terrestrial and aquatic) - these can be inferred based on the dentition of many Hell Creek animals supporting a diet comprised of such creatures, and various things such as molecular evolution data from those taxa supporting an evolutionary history implying their presence in certain regions at certain times.
Another example of where science fits in has been mentioned in a previous Sci-Day post, so I will not go into too much detail. We are basing the dynamics of our feeding system on the inferred metabolic rates and relative energy content per unit mass of different types of food. This further ensures the accuracy of our simulation, and also requires involvement of scientists studying living taxa since it is not possible to directly measure metabolic rates from fossils.
Perhaps one of the most important reasons why Dinosaur Battlegrounds is so amazing and important is the ideas for potential research. One idea was mentioned in the Dinosaur Metabolism Sci-Day post, and I have actually been discussing the possibility of doing that project with a professor here at my university. A related project relates to getting FEE values to use for non-dinosaur taxa, such as the reptiles, amphibians, and fish that lived in Hell Creek. These could be estimated based on data from their closest living relatives (ie for Amia fragosa and Melvius thomasi the FEE values would be based on modern Amiid fish). This gives scientists the opportunity to gather data on these species that could also be useful to studies that are not directly related to Dinosaur Battlegrounds, further increasing our positive impact on the scientific community.
Additionally, as has been mentioned many times before, Dinosaur Battlegrounds is not just a game - it can act as a simulation software that could be used to test hypotheses about many different aspects of a paleoecosystem. In many ways, it functions like any other model or simulation - if, for example, a hypothesized species distribution is unstable, the population might die off entirely, or simply settle into a completely different distribution that allows for a stable population. This is due to the integration of naturally occurring stochastic processes that are very hard to fully account for in current models/software used for this purpose. Such aspects of a paleoecosystem are extremely difficult to examine, as things such as fecundity and average population size in a given region cannot be measured in the same way as with extant flora and fauna.
Lastly, there are also many secondary benefits that contribute to the massive impact Dinosaur Battlegrounds will have:
- As a video game, Dinosaur Battlegrounds also provides a fun experience for non-scientists, while also teaching them about the prehistoric earth. In this way, it helps getting accurate information out to the public, and feeds an interest in paleontology and other life sciences.
- By allowing the player to choose between conflicting theories when applicable, it can help develop a capacity for analyzing evidence for contrasting ideas, which is an important skill for any scientist and for a healthy and happy populace.
- Perhaps most crucially, in order to ensure accuracy, we plan to use a portion of the profits we make to fund further research in Paleontology and other sciences in order to ensure that Dinosaur Battlegrounds continues to be the most accurate experience possible.
- Dinosaur Battlegrounds requires science to be applied in a new way. It requires us to figure out how to manifest various traits of the actual animals into the gameplay itself. For example, T. Rex had a visual overlap of 55°, whereas most herbivores had much smaller overlap (if any). While we understand the effects from an "outside" perspective, we have to actually put ourselves in the animals' shoes and figure out how to represent such differences. This can lead to a deeper understanding of their biology because of this.
References:
Balsai, Michael Joseph. 2001. The phylogenetic position of Palaeosaniwa and the early evolution of the Platynotan (Varanoid) anguimorphs (January 1, 2001). Dissertations available from ProQuest. Paper AAI3031637. http://repository.upenn.edu/dissertations/AAI3031637
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