Creature Feature 21

Hello, everyone! Sorry about the delay, there were some issues that prevented me from getting something out yesterday.

Today, we're going talk about another crocodylian from Hell Creek - Borealosuchus sternbergii!

Borealosuchus sternbergii model, WIP.

Borealosuchus sternbergii was originally assigned to the genus Leidyosuchus, but a reevaluation of that genus led to the formation of the new genus Borealosuchus, to which B. sternbergii was assigned - it is now the type species for the genus Borealosuchus (Brochu, 1997).

A paper in 2012 placed Borealosuchus as the most basal member of the genus. The exact relationships between Borealosuchus and the rest of crocodylia is not fully resolved - many phylogenic analyses placed the genus closer to Brevirostres (alligators and crocodiles) than to Gavialoidea (gharials) (Brochu et al., 2012), several placed it closer to Gavialoidea than to Brevirostres (Puértolas et al., 2011), and a few placed it outside of Crocodylia entirely (Pol et al., 2009). However, the authors note that all three are equally parsimonious (Brochu et al., 2012), so only further research will be able to resolve this issue.

Unfortunately, there is not much for me to write about Borealosuchus paleobiology or paleoecology, as most of the research that involves the genus is about its relationships to other crocodylians rather than the actual lifestyle of the animal. However, based on my own knowledge of crocodylians and modern ecosystems I have a few ideas about how it may have lived. Keep in mind that this is purely speculative and should be taken with a grain of salt.

While Borealosuchus does not have resolved relationships to other crocodylians, its cranial anatomy appears similar to that of modern crocodiles. This, combined with the fact that the Hell Creek formation was bordered by the shrinking Western Interior Seaway, makes me think that it may have lived similarly to the modern American crocodile (Crocodylius acutus). In the Everglades, American crocodiles and American alligators are separated for the most part by habitat preference - they tend to be closer to the coast, in more salty bodies of water such as brackish lakes, mangroves, lagoons, etc. Alligators, on the other hand, prefer more inland, fresh water. It could be that Borealosuchus shared this preference, with Brachychampsa dominating in the more inland bodies of water. In fact, the original material from which B. sternbergii was described came from the Lance formation (Gilmore, 1910), which was a coastal floodplain environment - this may be supportive of my hypothesis.

Well, I hope this has given you a bit more information about Borealosuchus sternbergii! I know it was a bit short, but I did what I could with what I could find.

Acknowledgements:

Brochu, C. A. 1997. A review of "Leidyosuchus" (Crocodyliformes, Eusuchia) from the Cretaceous through Eocene of North America. Journal of Vertebrate Paleontology 17 (4): 679-697.

Brochu, C. A.; Parris, D. C.; Grandstaff, B. S.; Denton, R. K. Jr.; Gallagher, W. B. 2012. A new species of Borealosuchus (Crocodyliformes, Eusuchia) from the Late Cretaceous-early Paleogene of New Jersey. Journal of Vertebrate Paleontology 32 (1): 105-116.

Puértolas, Eduardo; Canudo, José I.; Cruzado-Caballero, Penélope. 2011. A New Crocodylian from the Late Maastrichtian of Spain: Implications for the Initial Radiation of Crocodyloids. PLoS ONE 6 (6) e20011.

Pol, Diego; Turner, Alan H.; Norell, Mark A. 2009. Morphology of the late Cretaceous crocodylomorph Shamosuchus djadochtaensis and a discussion of neosuchian phylogeny as related to the origin of Eusuchia. Bulletin of the American Museum of Natural History 324: 1-103.

Gilmore, C. W. 1910. Leidyosuchus sternbergii, a new species of crocodile from the Cretaceous Beds of Wyoming. Proceedings of the United States National Museum 38(1762): 485-502.

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.

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

Creature Feature 20

Well, now that we've covered all of the dinosaur species from Hell Creek, it's time to start getting in to the other types of vertebrates! This week, we're going to look at the stagodont metatherian genus, Didelphodon!

Didelphodon template model, WIP. Texture variants will be used to represent the different species.

Didelphodon was a genus of metatherian mammals - this group includes the marsupials. There are two confirmed species that have been found in Hell Creek - D. vorax (the type species) as well as D. padanicus. There are other remains that may represent new species, but these are either too fragmentary to identify or have not been fully described yet (Kielan-Jaworowska et al., 2004). Didelphodon was a rather large mammal by Mesozoic standards, around the size of a small domestic cat (Fox and Naylor, 2006). Its dentition is indicative of a predatory lifestyle, with distinct bladelike cusps and carnassial notches. In addition, the short, massive jaws bear huge premolar teeth which appear to be well-suited for crushing (Kielan-Jaworowska et al., 2004).

While most mammals are only known from isolated teeth and occasional jaw fragments (such as Alphadon), Didelphodon skeletal material has been found. Its skull is similar to that of the modern Tasmanian devil (Sarcophilus harrisii), while the postcranial anatomy resembles that of a modern otter. It is suggested that it was semiaquatic (Fox and Naylor, 2006; Kielan-Jaworowska et al., 2004), possibly making its home by burrowing into the riverbanks. The diet for Didelphodon may have consisted of crawfish, mollusks, small lizards, plants, and even dinosaur eggs. Given that the skeletal material was found in sediment attributed to a riverbed, it is thought that the reason for the unusual preservation of the fossil (roughly 30% complete) was that it died in its burrow. In addition, a fossil water stain surrounded the specimen, suggesting that its remains were quickly buried by fluctuations in the water table (Rocky Mountain Dinosaur Research Center, 2010). Unfortunately, the paper that will formally describe the new specimen has not been published as of yet, but at some point in the future I hope to get in contact with the authors to see if they can help make sure our model is as accurate as possible.

The mollusk-heavy diet of Didelphodon certainly makes sense, as there was a great diversity of freshwater mollusks - in fact, at my count there are at least 7 genera known from Hell Creek. While as far as I know there are no remains of crawfish, it is not unreasonable to suspect they would have been present. In addition, it may have been preyed upon by Borealosuchus and Brachychampsa, though this relationship could be complicated by the possibility that Didelphodon may have opportunistically preyed upon very young hatchlings as many small opportunistic predators do today (raccoons, for example). Keep in mind that these are just hypotheses that I am proposing based on my own personal knowledge, and should not be taken as fact.

Well, I hope this post has taught you a little bit more about Didelphodon! We're gonna start showing more love to a lot of the lesser-known vertebrates from Hell Creek, so stay tuned!

Acknowledgements:

Kielan-Jaworowska, Z.; Cifelli, R. L.; Cifelli, R.; Luo, Z. X. 2004. Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure. New York: Columbia University Press. pp. 441-462.

Fox, R. C.; Naylor, B. G. 2006. Stagodontid marsupials from the Late Cretaceous of Canada and their systematic and functional implications. Acta Palaeontologica Polonica 51 (6): 13-36.

Didelphodon vorax. Rocky Mountain Dinosaur Resource Center. 2010-12-07. Retrieved 2016-5-17.

Sci-Day 17: T Rex expedition details

Hello again, everyone! This post is a followup to the one from earlier this morning - in this post I will try to give a bit more information about the individual T. Rex in question, and any other information about the locality itself.

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.

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!

Creature Feature 19

Hello, fans! This week will be the last dinosaur Creature Feature... For those of you who have been paying close attention, you know what species that is. It is the recently described, massive dromaeosaur Dakotaraptor steini!

 Dakotaraptor steini model, WIP.

Dakotaraptor steini was a truly gigantic dromaeosaur, only exceeded by Utahraptor ostrommaysorum in size. However, Dakotaraptor does not share the proportions or adaptations found in Utahraptor - its proportions more closely resemble those of smaller dromaeosaurids such as Deinonychus (DePalma et al., 2015). The total estimated length of Dakotaraptor is approximately 5.5 meters.

The remains of Dakotaraptor were found in Harding County, South Dakota by Robert DePalma in 2005, and the species description was published 5 years later. The holotype (PBMNH.P.10.113.T), consists of a partial skeleton (lacking the skull) of an adult animal, consisting mainly of forelimb and hindlimb elements, though a single fragmentary dorsal centrum, furcula, and 20 caudal vertebrae were also preserved. The description also included 9 paratype specimens from the same site, though these seem to represent a more gracile morphotype. These paratype specimens consist of hindlimb elements, several furculae, and isolated teeth (DePalma et al., 2015).

One particularly fascinating aspect of the Dakotaraptor remains is that the left ulna clearly shows the ulnar papilli, or quill knobs, like those found in some other dinosaurs as well as in modern birds. Based on the spacing of the knobs, it is estimated that there were 15 secondary wing feathers branching off the ulnar part of the forelimb (DePalma et al., 2015). Unfortunately, remains of the phalanges and other forelimb elements are not well enough preserved to determine the number/arrangement of feathers across the entire wing.

When a phylogenetic analysis of the Dromaeosauridae was conducted, it was found that Dakotaraptor steini was sister to Dromaeosaurus albertensis, and these two taxa in turn were sister to Utahraptor ostommaysorum (DePalma et al., 2015).

Dakotaraptor represents a significant leap in our understanding of the paleoecology of the Hell Creek Formation. Prior to its discovery and subsequent description, there was a strange dichotomy of carnivorous dinosaurs - small maniraptorans, and Tyrannosaurus. However, Dakotaraptor represents a transitional size form between these two groups, and as such requires us to reanalyze our views of the ecological and trophic interactions among dinosaurs and other taxa from Hell Creek. Additionally, the presence of two distinct morphotypes adds to our knowledge of the dynamics of body size in dromaeosaurids (DePalma et al., 2015). In fact, it may actually be evidence for sexual dimorphism - though if this is the case we do not know which morph represents males and which represents females.

Another interesting possibility is that Dakotaraptor may have competed with immature T. Rex (or mature Nanotyrannus lancensis, if it is indeed a distinct species), partially due to the possibility that it hunted in packs (DePalma et al., 2015). If this is the case, it would certainly be an amazing sight to behold!

Well, I hope you all enjoyed the very last dinosaur Creature Feature! Next week we will start to get into the less well-known vertebrates from Hell Creek!

Acknowledgements:
DePalma, Robert A.. Burnham, David A, Martin, Larry D, Larson, Peter L, & Bakker, Robert T. 2015. The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions (14).

Creature Feature 18

Greetings, fans! Today we go over the second to last dinosaur from Hell Creek - the somewhat controversial ceratopsid, Torosaurus latus!

Torosaurus latus model, WIP.

Torosaurus latus was an herbivorous ceratopsid, with a massive, 2.77 metre long frill. In life, it is thought to have reached approximately 7.6 to 9 meters in length, and weighed in at approximately 4 to 6 tons (Holtz, 2011). Torosaurus had two large fenestrae in its frill, long, dorsally concave squamosals, and ten or more epiparietals (small horns on the edges of the frill). Additionally, the nasal horn was rather short (Longrich and Field, 2012). While there is a second species of Torosaurus, though this species is slightly older and is not from Hell Creek - as such, it will not be featured.

Recently, the validity of Torosaurus latus has been disputed. Some authors have argued that Torosaurus latus is actually synonymous with Triceratops, representing the mature growth stage of the latter. Currently, no Torosaurus juveniles have been found, whereas a considerable number of juveniles have been uncovered for Triceratops. Additionally, one distinguishing trait of Triceratops is its short squamosals - these are absent in adult forms of other Chasmosaurines, making this a case of paedomorphosis. Some have argued that this fact is best explained by Triceratops and Torosaurus representing growth stages in the same species (Scanella, 2009). 

A followup analysis of 38 skull specimens from Hell Creek (29 Triceratops, 9 Torosaurus) supported this hypothesis (Scanella and Horner, 2010). The authors placed particular emphasis on the fact that Ceratopsian frills are composed of metaplastic bone, which can lengthen and shorten with time, lengthening and resorbing to form new shapes. They also noted that there is already known to be considerable ontogenetic changes in the skull and frill morphology of Triceratops, with horn orientation changing from backward to forward-facing with age. Furthermore, approximately half of the Triceratops skulls had two thin areas in the frill that corresponded to the placement of the fenestrae in Torosaurus, which were surrounded by mature granular bone. They asserted that this change would help to reduce the weight of the frill as it continued to grow ever larger.

However, this synonymy is not without its problems. In their paper suggesting synonymy, Scanella and Horner also acknowledged that there is data that is not easily explained by the synonymy of the two genera. One such issue is the rarity of Torosaurus remains - if it does indeed represent the mature form of Triceratops, it would be expected to be far more common. However, they also noted that this could be due to higher mortality in subadults, as well as potential preservation biases - it may have been that the older animals preferred to live at higher elevations, where fossilization would be far less common due to erosion. Additionally, some analysis did seem to show the existence of authentic subadult specimens of Torosaurus, though they believed this was actually indicative of individual variation. They also noted the apparent lack of transitional forms showing the formation of the large fenestrae. To address this, they cited the contentious holotype of Nedoceratops as such a transitional form, explaining the problematic traits of the genus as being due to its transitional state. They also cited the variability in position and number of episquamosals within Triceratops as possibly being indicative of an increase in number with age, explaining the higher count found in Torosaurus.

Since the 2010 publication, other paleontologists have expressed their doubts as well. A 2011 paper noted that the characters in Nedoceratops that were originally interpreted as being indicative of a transitional form are actually pathological in nature (Farke, 2011), also noting that while there is individual variation in the number of episquamosals in many Ceratopsids, there are no known species in which this number changes with age. Furthermore, it was noted that in other Ceratopsids that possess large fenestrae, these holes are present even in very young juveniles, suggesting that formation of fenestrae is not related to ontogeny. Further issues were also addressed, such as the possibility that the areas on the frill of Triceratops actually were indicative of fenestrae formation, but I will not get into the nitty-gritty details here. For those who are interested in learning more, I would suggest reading the original source material.

Several more papers have also raised issues with this idea. One of these used morphometric analysis to examine the various ages of Torosaurus and Triceratops specimens, and while it did find a general trend of Triceratops juveniles and Torosaurus adults, there were several notable exceptions. Two specimens of Torosaurus appeared to be quite young, somewhere approaching the age of some known Triceratops individuals. Conversely, it was also found that ten of the Triceratops skulls had reached a level of maturation equal to that of most aged specimens of Torosaurus (Longrich and Field, 2012). This paper also raised further objections, but due to time and space constraints I cannot get into all of them here.

A third paper published in 2013 used a statistical morphospace analysis (actually something I described in the Sci-Day discussing Species Concepts) to describe the variation of Torosaurus, both species of Triceratops, and Nedoceratops correlated with maturation. They found that Torosaurus specimens still retained a distinct anatomy from that of both Triceratops species, even when frill shape isn't included. While they admitted that the low number of Torosaurus specimens makes the analysis a bit less reliable than it otherwise might be, it still seems sufficient to refute the synonymy of the two genera (Maiorino et al., 2013).

In Dinosaur Battlegrounds, we may try to make it a player choice as to whether or not Torosaurus will be a distinct population of its own, or will simply represent an adult growth form of Triceratops. This would be something that would take a while to implement, as there is a lot of work that would have to go into the population ecology and whatnot, but it could help us understand the issue better.

Well, I hope you have enjoyed this somewhat controversial Creature Feature! We do not want to take sides here at Dinosaur Battlegrounds - our goal is to simply give our fans the evidence, and let you practice your critical thinking skills so you can make your own informed decisions!

Acknowledgements:

Holtz, Thomas R. Jr. 2011. Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.

Longrich, N. R.; Field, D. J. 2012. Torosaurus is not Triceratops: Ontogeny in chasmosaurine ceratopsids as a case study in dinosaur taxonomy. PLoS ONE 7 (2): e32623.

Scanella, J. 2009. And then there was one: synonymy consequences of Triceratops cranial ontogeny. Journal of Vertebrate Paleontology 29: 177A

Scannella, J.; Horner, J.R. 2010. Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30(4): 1157 - 1168.

Farke, A. A. 2011. Anatomy and taxonomic status of the chasmosaurine ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A. PLoS ONE 6 (1): e16196.

Maiorino, L.; Farke, A. A.; Kotsakis, T.; Piras, P. 2013. Is Torosaurus Triceratops? Geometric Morphometric Evidence of Late Maastrichtian Ceratopsid Dinosaurs. PLoS ONE 8(11): e81608.