Sci-Day 4: The Foundations of Science

Hello, everyone! I hope you've been having a great week!

Today, I'd like to write about something that is a bit broader than any of the previous Sci-Day posts - specifically, some very important core concepts in science. I will be talking about the overall scientific approach that is taken in science as a field, why it is so important, and how effective it is.

The scientific approach is one of, if not the most important thing(s) to science. It is used in any field of genuine science - physics, biology, paleontology, chemistry, etc. Science is more than just a field - it is a way of thinking.

Science aims to explain observations using recorded data, and to help us learn more about the natural world. Different fields are dedicated to different topics, but they all share several things in common. They all use the scientific method - they thoroughly test their hypotheses, gathering relevant data (depending on the subject the methods will obviously differ), and these findings are submitted for peer review.

This idea of using evidence that is quantifiable, and methods that can be replicated, is absolutely key to science. If the evidence and data gathered does not support the hypothesis, it is either discarded or revised to fit the new findings. This means it is important for a scientist to never get too attached to a hypothesis - if new evidence contradicts the hypothesis, one needs to be able to accept the fact that the original hypothesis needs to be discarded or revised.

However, that open-mindedness must be moderated with a level of healthy skepticism. One of the biggest problems in modern society is that the average person is not well-educated in subjects that are extremely important to issues we currently face. Thus they are not very likely to get their information from a peer-reviewed scientific journal, or other reliable source with verified data, and simply believe what they read from less-than-trustworthy sources. Those sources often provide questionable evidence at best, rarely cite reliable sources, and often are not written by someone with an extensive background in that subject. Even if one is not a scientist with years of research experience under their belt, one can still have a level of scientific skepticism. Carl Sagan wrote a wonderful article called "The Fine Art of Baloney Detection", where he addresses this issue and outlines a few important core questions to ask yourself when you read some article, book, or the like that makes a claim. If you do this, you are far less likely to be led astray by pseudoscience.

Another thing I'd like to talk about is the definition of the word 'theory'. There is a significant difference between the scientific and colloquial definitions of the word, and this can lead to significant misunderstandings. In everyday use, 'theory' is used to mean an 'educated guess'. In science, a theory is much more than simply a 'shot in the dark', or even a hypothesis. Essentially, a theory is an explanation for some aspect of the natural world that is supported by large amounts of data, observations, experimentation, and has been repeatedly tested.

The repeated testing element is extremely important - results must not just be taken from a single piece of research. To better understand this importance, let's try a thought experiment: you are a scientist, and you conduct some experiment to investigate Hypothesis 1 [for this experiment it does not need to be anything specific]. For data, let's say you get 5 values, or whatever quantity/quality it is you're measuring: let's call these A, B, C, and D (can be anything that is quantifiable/measurable). However, some months/years later, a different scientist conducts the exact same experiment under the exact same conditions, but gets completely different results. What do you do? Do you simply assume that you were right all along, or do you go back and reinvestigate the experiment to see why two identical replications of the same experiment got drastically different results? If you are a good scientist, you will go with the latter - if results or observations are indicative of some natural process going on, then anyone should be able to replicate the procedure under identical conditions and get the same results.

Theories are extremely useful, as they are able to make falsifiable predictions - in order for something to be considered a scientific theory, it must consistently be able to make consistently accurate predictions across the range of phenomena it aims to describe. Unlike a hypothesis, a theory must be supported by multiple, independent observations and experiments - in some sense, a theory is the eventual result of a series of thoroughly tested hypotheses. However, it is similar to a hypothesis and pretty much any other scientific principle in that it must be subject to minor revisions and refinements as necessary to fit any new findings and data - this will obviously increase the accuracy of its predictions.

One example of the successful predicting power of a scientific theory is the very discovery of both Uranus and Neptune. Both were predicted to exist (using Newton's Theory of Gravity) before they were directly observed. I won't get into the details as it is not closely related to Dinosaur Battlegrounds, but if you would like to know more there are lots of sources you can find to read more about it.

Another example hails back to Charles Darwin, as he was doing research on insect pollination of orchids. Upon examining the specimens he received, he noticed that one species had an extremely peculiar flower, and subsequently predicted that there must be some species of moth with an extremely long proboscis living in that region (Darwin, 1862). This was based in part on the ideas that he outlined in his ever-famous work, On the Origin of Species, published in 1859. Many years later, a species of Hawkmoth (Xanthopan morganii) was found from that region, with an extremely long proboscis, just as Darwin predicted (though it was Alfred Wallace who predicted that the species would specifically be a hawkmoth).

Lastly, another example of the scientific approach to understanding the natural world is directly relevant to Dinosaur Battlegrounds - specifically, the discovery of the dromaeosaur Dakotaraptor steini. According to paleontologist Robert Gay, dromaeosaur teeth had been found many years before they found the actual partial skeleton, and it was hypothesized based on several characteristics of those isolated teeth that there was a large dromaeosaur living in the Hell Creek formation. This is a perfect example of how science works - evidence was taken and interpreted in a wider context, and it led us to a new discovery.

In closing, the scientific mindset, the scientific method, and the overall process by which it operates are pivotal to all of the discoveries we have made about how the universe works - from clusters of galaxies to the smallest subatomic particles... Without the use of thorough observation, experimentation, and refining ideas, we would know almost nothing of the magnificent beauty of our wonderful universe.

I hope that this post has given you a bit more information on the core principles of science, and perhaps that you will take this message to heart, asking for evidence, and craving discovery. After all, Dinosaur Battlegrounds, ultimately, is a mission of discovery that relies on people with this very mindset. Without those people, this game would not be possible.
 
Acknowledgements:
Gay, Robert J. Personal Communication. 2016
Darwin, Charles. 1862. Fertilisation of Orchids.

Special Thanks to Robert Gay for providing the example regarding Dakotaraptor, and for reviewing this post to ensure it is accurate. He's done some great work with early Jurassic theropods such as Dilophosaurus - I'd encourage you to read some of his papers, they're very fascinating and informative!

Creature Feature 4

This week I wanted to look at a less famous dinosaur from Hell Creek - the ornithopod Thescelosaurus.

There are actually three separate species of Thescelosaurus that are currently accepted as valid - the type species (I can explain what this means later if anyone is interested) T. neglectus, as well as T. garbanii and T. assiniboiensis. Of these three, remains of the former two have been found in the Hell Creek formation.

Thescelosaurus was a robust, bipedal dinosaur that was most likely herbivorous (Norman et al., 2004). The position of the teeth in the skull (very far from the external surface) as well as a distinct ridge on both dentaries (lower jaw bone) is believed to indicate the presence of muscular cheeks (Morris, 1976). The forelimbs had 5 fingers, and each hindlimb had four toes ending in hoof-like claws. There were also a series of ossified tendons bracing the tail from the middle to the tip, which would reduce its flexbility (Gilmore, 1915).

It was small compared to some of the other non-avian dinosaurs from the Hell Creek formation - for various specimens the length has been estimated to be between 2.5 and 4 meters (8.2 to 13.1 feet) (Galton, 1974) and a weight of approximately 200-300 kilograms (450-660 pounds) (Erickson, 2003). The type specimen of T. garbanii was estimated to be between 4 and 4.5 meters (13.1 to 14.8 feet) long (Morris, 1976).

The relative completeness of known Thescelosaurus specimens has been interpreted as evidence of a preference for channel and floodplain habitats (Lyson and Longrich, 2011). It was most likely a browser, selectively feeding on vegetation in the first meter or so up from the ground (Norman et al., 2004). Its hindlimb anatomy combined with its robust build indicates it probably was not a swift runner - the femur was longer than the tibia, unlike what is observed in fast-moving animals (Sternberg, 1940).

I hope this has given you some new information about the interesting Thescelosaurus!

Acknowledgements:
Norman, David B.; Sues, Hans-Dieter; Witmer, Larry M.; Coria, Rodolfo A. 2004. Basal Ornithopoda. In Wieshampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 393-412.

Morris, William J. 1976. Hypsilophodont dinosaurs: a new species and comments on their systematics. In Churcher, C.S. (ed.). Athlon. Toronto: Royal Ontario Museum. pp 93-113.

Gilmore, Charles W. 1915. Osteology of Thescelosaurus, an ornithopodus dinosaur from the Lance Formation of Wyoming (pdf). Proceedings of the U.S. National Museum 49 (2127): 591-616.

Galton, Peter M. 1974. Notes on Thescelosaurus, a conservative ornithopod dinosaur from the Upper Cretaceous of North America, with comments on ornithopod classification. Journal of Paleontology 48 (5): 1048-1067.

Erickson, Bruce R. 2003. Dinosaurs of the Science Museum of Minnesota. St. Paul, Minnesota: The Science Museum of Minnesota. p. 31.


Lyson, Tyler R.; Longrich, Nicholas R. 2011. Spatial niche partitioning in dinosaurs from the latest Cretaceous (Maastrichtian) of North America. Proceedings of the Royal Society B 278 (1709):
1158-1164.

Sternberg, Charles M. 1940. Thescelosaurus edmontonensis, n. sp., and classification of the Hypsilophodontidae. Journal of Paleontology 14 (5): 481-494.

Sci-Day 3: Population Ecology

Happy Sci-Day, everyone! Today I'll be covering a topic that will be extremely important for Dinosaur Battlegrounds - namely, the dynamics and ecology of populations.

By 'population', I mean the entire count of individuals of some given species. For example, all Tyrannosaurus rex could be a population. There are a lot of important factors that we need to figure out, that are not necessarily answered just by looking at the fossil record.

Perhaps the most intuitive example is distribution. How large is the natural range for the species? While we can get good estimates for this based on the fossil record and knowledge of potential barriers to migration at the time, it is by no means a complete picture. There may be areas where they existed, but we don't know due to a lack of rocks from that specific place/time, or perhaps the preservation conditions were poor in the region and as such they did not leave fossils. There is also always the simple possibility that there are fossils of that species there, but we simply have not found them yet.

Natural range is not the only aspect of distribution that is incredibly important. There is also the issue of how that population is spread throughout that range. Is it a relatively even distribution, or is it more clumped? This too cannot be completely answered by looking at fossils alone. With animals that live in herds, the population will be more clumped, as there will be multiple herds of many individuals across their range - the opposite is true for a primarily solitary species. If we only have fossils, we don't know if that animal was living alone (and died alone), or if it was part of some group where the rest of the individuals did not die (and thus were not fossilized).

The reason this distribution is important is because it will help us better understand the ecosystem. We may notice that previously unconsidered factors end up affecting distribution - for example, perhaps the presence of nest raiders alters the distribution of dinosaur species, or the density of Tyrannosaurus rex in a given area tends to be no higher than some fixed number.  The latter example relates somewhat to the concept of competition. If there are too many animals trying to make use of a limited resource, there is going to be competition. This competition (and resource availability) limits the population size of any species, along with other factors.

Another key factor of interest is population stability. In Dinosaur Battlegrounds, we need to create a stable ecosystem. In order to do so, we need to figure out how to distribute the many species across the map, and how many of each to put, as well as a general age distribution. If we just do this without any careful thought, it is highly likely that many populations will not be stable, and may go extinct (or drive others to extinction). To help ensure population stability, we have to take at least two variables into account - survival curve/rate and fecundity. Survival curves tell us approximately how the survival rate of that species changes with age, and fecundity tells us how many offspring that species yields in a given breeding. Since this obviously can vary with age (and the value is zero prior to sexual maturity), ecologists may use a projection matrix with the survival rates and fecundity of all 'life stages' (ie 1 year old, 2 year old, etc.), and then multiply that by a matrix with a hypothesized age distribution (ie 100 1 year olds, 75 2 year olds, etc.). The resulting matrix can then be multiplied by the original projection matrix, and this can be repeated as many times as is desired. The results will give an idea as to whether or not the population is stable - if it continues to increase exponentially, that is a problem - it also is a problem if it continues to steadily decrease. However, if it remains at more or less the same total value, you should be good. It will also let you know the hypothetical age distribution of such a population.

Well, I hope this Sci-Day has taught you a little more about population ecology!

Creature Feature 3

Today's creature feature will look at the famous armored ornithischian Ankylosaurus magniventris.

 Ankylosaurus was one of the last ankylosaurs, and is the largest known. One source estimates an adult size of approximately 7m (23 feet), and a weight of approximately 7 tonnes (or 13,000 pounds) (Paul, 2010). Unfortunately, despite its fame, much of its skeleton is actually unknown. This includes much of the pelvis, tail, and feet (Carpenter, 2004). Thus, any reconstruction of this species must use inferences based on relatives with more complete remains known.

The skull of Ankylosaurus was low and somewhat triangular, narrowing from the base up to the snout. Crests above the eye sockets merged into a pair of upper squamosal horns, and below these there were a pair of jugal horns that pointed down and to the sides.

As in other ankylosaurids, this species has been found with large osteoderms or scutes that would have been imbedded in its skin. However, these scutes have never been found in articulation, so their arrangement on its body can only be inferred based on the arrangement in similar related species. The walls of Ankylosaurus osteoderms were relatively thin, and the underside was hollow. Additionally, those thought to cover the body were relatively flat, though they had a small keel at the margin. Ankylosaurus also had small armor plates on its neck, though the remains of these pieces are fragmentary so their exact positioning is similarly uncertain.

The tail of Ankylosaurus ended in a large club, though unfortunately this is only known from a single specimen. It is known that in other ankylosaurs there was a degree of individual variation in club shape, so this is likely the case with Ankylosaurus as well. The 'handle' of the club was formed by the posterior seven caudal vertebrae, which were in direct contact with each other. These were sometimes coossified, making them completely immobile. There were also ossified tendons that attached to the vertebrae in front of the club, and these combined features added further strength (Arbour and Currie, 2015).

As with other ornithischian dinosaurs, Ankylosaurus was an herbivore. Its wide muzzle and relatively short stature made it well-adapted for non-selective browsing of low vegetation. One relative of Ankylosaurus was found with large preserved paraglossalia (cartilages or triangular bones found within the tongue), and these showed signs of significant muscular stress - this feature is thought to be common in all ankylosaurs, including Ankylosaurus. Some have suggested that the low replacement rate and size of ankylosaur teeth relied primarily on muscular tongues and hyobranchia (tongue bones) when feeding. Some extant salamanders have tongue bones similar to those found in ankylosaurs, and these species use their prehensile tongues to acquire their food (Hill et al., 2015). This research has suggested a varied diet for Ankylosaurus and its relatives that would have consisted of tough leaves and pulp-filled fruits. Personally, I can imagine the actual feeding mechanic working similar to that of a modern herbivorous turtle - the tongue could be extended as the mouth opened to "hold" the food steady just long enough for the animal to close its mouth and start orally processing the food. It's a bit hard to explain verbally, but you will see what I mean if you watch tortoises feeding in a video.

Well, I hope this gives you a bit more knowledge about the fascinating dinosaur that is Ankylosaurus!

Acknowledgements:
Paul, Gregory S. 2010. The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 234.
Carpenter, K. 2004. Redescription of Ankylosaurus magniventris Brown 1908 (Ankylosauridae) from the Upper Cretaceous of the Western Interior of North America. Canadian Journal of Earth Sciences 41 (8): 961-86.
Arbour, V.C.; Currie, P.J. 2015. Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs. Journal of Systematic Palaeontology. 1-60.
Hill, R. V.; D'Emic, M.D.; Bever, G.S.; Norell, M.A. 2015. A complex hyobranchial apparatus in a Cretaceous dinosaur and the antiquity of avian paraglossalia. Zoological Journal of the Linnean Society 175 (4).

Sci-Day 2: Ecology - Trophic Interactions

TGIS - Thank Goodness It's Sci-Day!

Today's post will cover a very important concept in ecology - trophic interactions.

By 'trophic interactions', I am referring to what may be colloquially called the 'food chain'. However, the latter term is a lot less descriptive and often makes people think of an almost linear dynamic, with one species eating another species eating another species up to the top species in whatever ecosystem that is. The problem is, as with many things in science, the real story is far more complex than what the common person might think. In any given ecosystem, species that eat one species may have multiple predators, and even a top predator may have creatures that prey on its young. Additionally, there are scavengers, which do not fit well into a simple linear model.


Trophic interaction is referring to any interaction that involves one organism getting energy from another. This ranges from Tyrannosaurus rex preying on a Triceratops, to Triceratops grazing on ferns, to scavengers that consume a dead Ankylosaurus and even the bacteria, fungi, etc. that work to decay the body and recycle the elements and biomass back into the ecosystem.

One way to visualize this is what is known as a 'food web'. A food web looks at an ecosystem and tries to visually depict all the trophic interactions between the species present. These are extremely useful, as it can reveal the roles that a species plays in that environment, and it can simply help understand the dynamics of the system in question. I actually created a rough draft of a food web for the Hell Creek ecosystem, in order to better understand the interactions between the species present, which will also allow us to create a more accurate simulation than we might be able to otherwise:

Note: Light blue arrows represent fresh water 'food chain', dark blue represent marine 'food chain', green represents terrestrial 'food chain'. Red arrows represent connections of relative uncertainty. Orange represents energy flow only from juveniles/hatchlings of the species the arrow is coming from.

As can be seen simply from looking at the web, there is an incredibly complex flow of energy in the ecosystem. Certain species/groups of species [not all species are represented by their own label, as all species within that category would have identical arrows and it would take up far more space] provide resources for a wide variety of other species. For example, it can be seen that freshwater pelecypods are very important in the freshwater part of the ecosystem - considering this label includes multiple different species, the cumulative abundance would likely be high enough to sustain the creatures that feed upon them - it may also be that these species avoided competition by specifically targeting a particular pelecypod species, though if so it would be very hard to prove with any great certainty. 

For the terrestrial part of the food chain, terrestrial invertebrates serve as a key food source - considering how large of a category that is, it is hardly surprising. However, there are no body fossils of such invertebrates from Hell Creek [though it's possible that I simply have not heard of them] - the only evidence I am aware of is an ichnotaxa ('trace fossil') of a leaf beetle, and marks on fossil leaves that appear to be made by insects. This can be explained by the fact that invertebrates, especially those that are soft-bodied, are far less likely to fossilize than an animal with solid bones. Despite this, the abundance of species with dentition implying a diet primarily or at least partially composed of insects and other invertebrates is strong support for a diverse and abundant population of such creatures.

The last thing I will cover will be some of the terms that are used to describe the type of role a species plays in the trophic interactions or energy flow in the ecosystem. They are the following:

Primary producers: A primary producer is an autotroph that gets its energy from the sun (or, in some cases, chemical energy from sources such as hydrothermal vents). This may also include 'seston', which is small particles of organic matter that are the remains of dead organisms - this may also be called 'marine snow'. Examples of primary producers include plants, phytoplankton, and algae.
Primary consumers: These are heterotrophs that get their energy by eating primary producers. Examples of primary consumers include Triceratops and the freshwater pelecypods.
Secondary consumers: As one might infer, secondary consumers are the animals that eat the primary consumers. For example, Tyrannosaurus rex would be a secondary consumer, as it eats Triceratops, and the extremely common bowfin-like fish Kindleia fragosa eats freshwater pelecypods and would also fit in this category.
Tertiary consumers: These creatures eat secondary consumers. Note that not all ecosystems include animals in this category, and that the categories of consumers are not mutually exclusive. For example, Tyrannosaurus rex is both a secondary and tertiary consumer, as it eats Chirostenotes and Triceratops.
Decomposers: This is an extremely important role in any ecosystem - it includes the scavengers that prey on carcasses, the bacteria that work to decay leaf litter and dead creatures (in addition to scavengers), and more. In doing so, these creatures take the elements in the bodies of those dead creatures and recycle it back into the food web. Without decomposers, nutrients would remain locked up in bodies of dead creatures, and the ecosystem would slowly run out of nutrients and would die off.

In terms of relative abundance in a terrestrial ecosystem, this value decreases from top to bottom in the above list (with the exception of decomposers). This is because at higher levels in the chain, there is less biomass available to use - it is being taken up by the organisms lower in that chain. Additionally, there can only be so many consumers - if there are too many, they could eat themselves to extinction.

I hope this post has been informative, and has given you a bit more knowledge about how energy and nutrients move through an ecosystem. It's not just a dino-eat-dino world out there!

Creature Feature #2

For this week's Creature Feature, we'll be looking at one of the most well-known herbivores from Hell Creek: the three-horned Triceratops.

Triceratops horridus model - model on the left is the "relaxed" texture; model on the right is the "blush" texture.

Triceratops was a large Ornithischian dinosaur in the family Ceratopsidae - its distinctive frill and three-horned face are easily recognized by both seasoned paleontologists and casual dinosaur enthusiasts. The actual function of the frill and horns has been a subject of debate for many years. The initial belief was that they served as defensive structures to protect against predators such as Tyrannosaurus rex, but more recent theories suggest that they may also have been used for display purposes. This is supported by the fact that frill shape and size as well as horn structure differ greatly between different ceratopsians, as well as the fact that modern animals with similar structures use them to intimidate rivals, attract mates, or otherwise communicate with other members of their species (Farlow and Dodson, 1975). In fact, the horns may have been used in non-fatal intraspecific combat, involving males competing for mates or simply disputes over dominance (Martin, 2006). This hypothesized function is manifested in the form of an optional "blush" mechanic. If enabled, you will be able to press a button to "blush", which causes your character to change from the "relaxed" to the "blush" texture. This can be used to intimidate rivals, attract mates, or other types of communication/signaling.

The overall anatomy of Triceratops suggests that it primarily consumed low growing vegetation, though its sheer size, along with its horn and hard beak, could have allowed it to topple larger trees in a manner similar to modern elephants (Dodson and Sampson, 2004). The deep, narrow beak at the end of their snout implies that they fed by plucking and grasping plants rather than biting as some modern grazers do (Ostrom, 1966).

Like some other herbivorous dinosaurs, Triceratops had a large number of teeth. These were arranged in groups known as 'batteries' - the number of vertical columns ranged between 36 and 40, and between 3 and 5 teeth were stacked in each column. These teeth wore down continuously, and only a fraction of the total teeth were in use at a given time (Dodson et al., 2004). The massive size and number of teeth in Triceratops suggests that it ate massive amounts of very tough plant material - suggestions range from palms and cycads (Weishampel, 1984) to ferns, which grew in prairies analogous to modern grasslands (Coe et al., 1987).

Well, I hope that gives you a little bit more knowledge about Triceratops! Tune in next week for the next Creature Feature!

Acknowledgements

Farlow, J.O. and Dodson, P. 1975. The behavioral significance of frill and horn morphology in ceratopsian dinosaurs. Evolution 29 (2): 353.
Martin, A.J. 2006. Introduction to the Study of Dinosaurs. Second Edition. Oxford, Blackwell Publishing. pg. 299-300.
Dodson, P.; Forster, C.A.; and Sampson, S.D. 2004. Ceratopsidae. In: Weishampel, D. B.; Dodson, P.; and Osmólska, H. (eds.), The Dinosauria (second edition). University of California Press, Berkeley, pp. 494–513.
Ostrom, J. H. 1966. Functional morphology and evolution of the ceratopsian dinosaurs. Evolution 20 (3): 290-308. 
Weishampel, D.B. 1984. Evolution of jaw mechanisms in ornithopod dinosaurs. Advances in Anatomy, Embryology, and Cell Biology. 87: 1-110.
Coe, M. J.; Dilcher, D. L.; Farlow, J. O.; Jarzen, D. M.; and Russell, D. A. 1987. Dinosaurs and land plants. In: Friis, E. M.; Chaloner, W. G.; and Crane, P. R. (eds.) The Origins of Angiosperms and their Biological Consequences. Cambridge University Press, pp. 225-258. 

Sci-Day 1: Cladistics and Phylogenetics

For the first Sci-Day post, I'd like to cover a very important topic that is relied upon heavily in our representations of prehistoric creatures in Dinosaur Battlegrounds.

Cladistics and phylogenetics are critical tools for portraying prehistoric creatures in the most accurate possible way. These two tools allow us to figure out what a prehistoric animal's closest relatives are, and using that information we can have a more informed idea as to what its soft tissue anatomy may have been like, despite the original tissue being lost to the processes of geologic time.

This is also very important if a species is based on very fragmentary or incomplete remains. If there is enough material to determine the species' relationship(s), it is possible to make an accurate skeletal restoration despite not having complete remains of that species.

Cladistics is a relatively new branch of a field known as "Systematics" - this field is dedicated to classifying and better understanding the evolutionary interrelationships and diversification of life on our planet. Cladistics, in particular, is a method of classification that places taxa based on their hypothesized ancestry. Various characteristics are quantifiably measured in each of the species - these may be as simple as the presence or absence of some specific feature (a "binary character"), or it may be something such as the number of vertebrae in the tail, where there may be a range of values. Using this information, a cladogram is then created, utilizing the "principle of parsimony" - the tree with the fewest character state changes is usually considered to be the best.

For example, let's say we have species A, B, C, and D. We have classified them on the basis of 4 binary characters (1, 2, 3, and 4). For these characters, a value of "0" means the character is absent, and a value of "1" indicates that character is present. Species A has a character state of 1/0/0/0, Species B has a character state of 1/1/0/0, species C has a character state of 1/1/1/0,  and species D has a character state of 1/1/1/1. In this example, the best possible tree places C and D closest together, followed by B, with taxon A as the "outgroup". Alternatively, you could place B and D closest together, but this would add more character state changes to the tree that can be avoided and thus the first tree is preferable.

Keep in mind, however, that most cladograms are not nearly that simple, and there may not be a single clear tree that stands out, and certain characters may evolve or be lost multiple times in a lineage. For example, snakes lost the limbs that their lizard ancestors evolved, and human beings lost much of the fur that is observed in our closest relatives. This phenomenon is known as "secondary loss". There is also the phenomenon of "convergence", where two taxa evolve the same or very similar features independently - an example of this would be the evolution of venom, as it has evolved in multiple unrelated lineages.

A great example of the application of cladistics and phylogenetics in Dinosaur Battlegrounds is the skin covering of Tyrannosaurus rex. Due to the technique known as phylogenetic bracketing, where a well-supported cladogram is used to infer character states in some taxa in the tree based on the principle of parsimony and the known states of that character in other taxa in the tree. This method predicts that Tyrannosaurus rex did have at least some degree of feathery covering.

However, it is important to keep in mind that it is possible that Tyrannosaurus rex lost its ancestral feathers, in the same way that large mammals lost most of their fur; until direct evidence of preserved feathers is found associated with a T rex specimen, it is impossible to say with complete certainty that it did or did not have feathers. With the current evidence, though, it appears likely that Tyrannosaurus was at least partially feathered.

Well, I hope this post taught you something new about the science of Dinosaur Battlegrounds!