Styracosaurus: Beast of the Week

This week we will be checking out Styracosaurus albertensis, the spike-frilled dinosaur!  Styracosaurus lived in what is now Alberta, Canada, during the late Cretaceous period, between 75.5 and 75.2 million years ago.  From beak to tail it measured about eighteen feet long and was a plant-eater when alive.  The genus name, Styracosaurus, translates to "Spike Reptile" in reference to the eight long spikes growing from the sides of its frill.  When alive, Styracosaurus would have shared its habitat with other dinosaurs like Parasaurolophus, Lambeosaurus, and Gorgosaurus.

Life reconstruction in watercolors by Christopher DiPiazza of two adult Styracosaurus working out a territory dispute. 

After Triceratops, Styracosaurus is possibly the most recognized member of the ceratopsian group of dinosaurs by image if not by name.  As far as dinosaur toys go, if any ceratopsian is going to show up in addition to Triceratops in a package, its almost always Styracosaurus.  (I'm actually genuinely surprised that out of the four ceratopsians that ultimately showed, it never appeared in a Jurassic Park/World movie). It's popularity is probably due to the fact that it has been known about for a lot longer than the majority of ceratopsians, formerly described over 100 years ago, so it's had time to make appearances in books and other popular media.  The other reason is Styracosaurus is just so striking to look at, even among currently known ceratopsian diversity.  Like its genus name suggests, adult Styracosaurus had a series of several extremely long spikes growing from the top edge of the frill.  In addition to these, it also had shorter spikes lining the lower edges of the frill, as well as a long horn growing out of the top of the snout.  We now know that Styracosaurus was capable of exhibiting a decent degree of variation among adults, with the number of long frill spikes ranging between four and eight depending on the individual.  There is even one specimen with seven frill spikes, showing that they were capable of expressing asymmetry in their head ornamentation.  

Front view of the Styracosaurus' skull on display at the American Museum of Natural History in New York.

The evolutionary purpose of Styracosaurus' head ornamentation, like those of most ceratopsians, is somewhat debated.  There's always the likelihood they were for display within the species, but there's also a strong chance they were additionally used as actual weapons, whether for fighting members of its own species for dominance, or against potential predators.  The sideways-facing frill spikes particularly seem like they would be effective at deterring the hungry jaws of tyrannosaurs away from the neck.  A Styracosaurus skeleton described in 2020, possesses proportionally much shorter frill spikes, a shorter nose horn, and an overall smaller body size than most other known Styracosaurus specimens on the fossil record, and is therefore thought to be of a juvenile individual.  Shorter horns in immature animals suggests they had some sort of sexual or social display purpose.  

Photograph of what is thought to be a juvenile Styracosaurus skull from the 2020 paper by Caleb Brown et al. Note the shorter frill horns and nose horn. 

The beak of Styracosaurus was narrow, and the lower beak tip was extremely long and curved upwards.  This would be a good adaptation for clipping specific plants to eat, much like a giant pair of rose trimmers.  Because of this it is likely that Styracosaurus and its relatives were more selective feeders rather than generalists, which are more adept at sucking up any plant material that's infront of them.   In the back of Styracosaurus' mouth were hundreds of small teeth packed together, forming what are called dental batteries.  These structures were good for finely slicing tough plant material, rather than grinding it.

Side view of the same Styracosaurus specimen as above at the American Museum of Natural History.

There have been bone beds comprised of multiple Styracosaurus skeletons discovered, but it is still unclear as to if they were actually herding animals.  The reason for this is because the area in which the dinosaurs seemed to have died was a riverbed at the time of their death.  Frequently, animals, herding or not, will congregate at water sources like this hoping to drink and then drown in flash floods all at once.  Therefore it could be possible Styracosaurus may have still preferred the more solitary lifestyle.  It would be difficult to cuddle with those big spikes anyway.

That is all for this week!  As always feel free to comment below or on our facebook page!

References

Brown, C.; Holmes, R.; Currie, P. (2020). "A subadult individual of Styracosaurus albertensis (Ornithischia: Ceratopsidae) with comments on ontogeny and intraspecific variation in Styracosaurus and Centrosaurus". Vertebrate Anatomy Morphology Palaeontology. 8 (1): 67–95.

Eberth, David A.; Getty, Michael A. (2005). "Ceratopsian bonebeds: occurrence, origins, and significance". In Currie, Phillip J., and Koppelhus, Eva. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Bloomington: Indiana University Press. pp. 501–536.

Holmes, R.B.; Persons, W.S.; Singh Rupal, B.; Jawad Qureshi, A.; Currie, P.J. (2020). "Morphological variation and asymmetrical development in the skull of Styracosaurus albertensis". Cretaceous Research. 107: 104308.
Lambe, L.M. (1913). "A new genus and species from the Belly River Formation of Alberta". Ottawa Naturalist 27: 109–116.

Ostrom, J. H. (1966). "Functional morphology and evolution of the ceratopsian dinosaurs". Evolution 20 (3): 290–308.

Tait, J.; Brown, B. (1928). "How the Ceratopsia carried and used their head". Transactions of the Royal Society of Canada 22: 13–23.

Tanke, D. H, and Farke, A. A. (2006). Bone resorption, bone lesions, and extracranial fenestrae in ceratopsid dinosaurs: a preliminary assessment. in: Carpenter, K. (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs Indiana University Press: Bloomington. pp. 319–347.

Moros: Beast of the Week

 This week we'll be looking at an important little dinosaur that helps us understand the backstory of the most famous dinosaur ever known.  Check out Moros intrepidus!

Moros was a relatively small meat-eating dinosaur that lived in what is now Utah, USA, during the Cretaceous period, between 97 and 96 million years ago.  From snout to tail Moros is estimated to have measured about 10 feet (3 meters) long based on fragmented remains.  The genus name is after the deity from Greek Mythology, Moros, who was the personification of impeding doom, appearing to those who were about to die. The reasoning for this name is because Moros is thought to be the ancestor of later apex predators, like Tyrannosaurus rex.

Watercolor reconstruction by Christopher DiPiazza of a trio of Moros.

Even though Moros is only known from an incomplete skeleton, paleontologists can deduct that it was indeed a member of the tyrannosaur group based on the leg and foot bones, and the teeth that were uncovered.  They were also able to identify the individual as an almost fully grown adult based on growth rings in the leg bone.  

It may seem odd to associate such a relatively small, lanky dinosaur like Moros, with giant monsters like Tyrannosaurus or Gorgosaurus, but when looking at the fossil record this actually makes sense.  The fossil record actually has many smaller species of tyrannosaurs found in North America, Europe, and Asia, ranging in age from 160 to 96 million years old.  The larger trannosaurids don't start showing up until millions of years later.  Different large-bodied meat-eaters, called the carnosaurs (like Sinraptor in Asia), existed alongside the smaller, earlier tyrannosaurs, and went extinct before the large, two-fingered tyranosaurids appeared in the same places.  It is thought that the smaller, more adaptable, early tyrannosaurs were able to survive whatever  wiped out the carnosaurs in the northern hemisphere, and then went on to occupy their niche as giant predators in the form of the two-fingered tyrannosaurids.  To put it into perspective, Tyrannosaurus is more closely related to birds than to dinosaurs like Allosaurus, and fossils like those of Moros help fill in the gaps that prove it.

Different views of the femur of Moros featured in the 2019 paper by Zano et al., including cross section and growth rings.

Moros had proportionally long, slender legs, which suggest it was a fast runner when alive, and possibly could have hunted smaller prey.  Since paleontologists have found feathers in other tyrannosauroid fossils, it is likely Moros had some sort of feathers in life too.  

References

Zanno, Lindsay E.; Tucker, Ryan T.; Canoville, Aurore; Avrahami, Haviv M.; Gates, Terry A.; Makovicky, Peter J. (February 2019). "Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record". Communications Biology.

Meraxes: Beast of the Week

 Today we'll be checking out a recently described dinosaur that was a giant meat-eater!  Make way for Meraxes gigas!

Meraxes was a large theropod that lived in what is now Argentina during the late Cretaceous period, between 95 and 94 million years ago.  From snout to tail it would have measured about 36 feet (almost 11 meters) long.  The genus name is actually after a dragon from the popular A Song of Ice and Fire fantasy novels. (what the show, Game of Thrones is based on.)  The species name, gigas, translates to "giant" because...this dinosaur was big.  

Watercolor life reconstruction of Meraxes gigas by Christopher DiPiazza.  Note the proportionally small arms and long claw on the second toes.

Meraxes was a member of the family of theropods called carcharodontosaurids, which are characterized by having large, narrow skulls lined with serrated blade-like teeth. (hence the family name which translates to "shark tooth reptiles") Other examples of carcharodontosaurids were the earlier Acrocanthosaurus and Concavenator, and the more famous and slightly larger Giganotosaurus. Meraxus is particularly important because it is the most complete skeleton known of a large charcharodontosaurid, which helps us understand more about their anatomy as a group.  

Like most of its kin, Meraxus had a long, tall skull, filled with blade-like serrated teeth, ideal for slashing and cutting huge chunks of flesh off bone. It also possessed ridges of rough-textured bone on the top of the snout and over the eyes, suggesting it had horn-like crests growing there in life.  These bony crests are actually common in various forms among many kinds of large theropods and may have been for some kind of intraspecies communication or even combat.  

Photoraph of recovered skull material from Meraxus from the 2022 paper by Canale.

Meraxus had three fingers with sharp claws on each hand, but extremely short arms proportional to the body.  Scientists note that despite how Tyrannosaurus is so famous for having tiny arms, this feature is actually not that rare among different kinds of theropods.  In fact, it was noted that proportionally small arms must have evolved at least four different times in theropods, present in tyrannosaurs, abelisaurs (like Carnotaurus), carcharodontosaurs, and the smaller bird-like alvarezsaurs.  If you count modern birds with tiny wings, like Kiwis, it's evolved even more times!  

Possibly the most unique feature about this dinosaur is the fact that it had an elongated claw on the second toe of each foot.  Unlike the specialized toes of dromaeosaurs and troodontids, these claws weren't retractable, so it seems they may have been more similar to the elongated claws on some modern bird feet, like cassowaries.  What purpose these claws served is currently a mystery, but they could have been to help Meraxus pin down a carcass or struggling prey as it tore chunks off with its jaws. (similar to what many modern predatory birds do today with their toe claws) It also could very well have been another instrument in fighting members of its own species. 

Photograph of the foot of Meraxus.  Note the long second toe claw.

Feet of the living Cassowary(bird).  Note the enlarged second claw convergently similar to that of Meraxus.  Unlike Meraxus, Cassowaries eat fruit and seeds, and mostly use their claws for defense.

Lastly before we go, scientists were able to examine certain bones from Meraxes and determine roughly how old it was when it died.  Turns out that individual was over 50 years old at the time of its death!  That makes it the oldest recorded fossil dinosaur known to science! They also were able to determine that like many modern reptiles, even though this Meraxes was an adult, it was still growing at a slow pace right up until it died.  This is a process called indeterminate growth, and it's been observed in a number of fossil dinosaurs, many modern reptiles, but not in modern birds.  

That is all for this week!  As always feel free to comment below!

References

Canale, J.I.; Apesteguía, S.; Gallina, P.A.; Mitchell, J.; Smith, N.D.; Cullen, T.M.; Shinya, A.; Haluza, A.; Gianechini, F.A.; Makovicky, P.J. (7 July 2022). "New giant carnivorous dinosaur reveals convergent evolutionary trends in theropod arm reduction". Current Biology.

Cullen, Thomas M.; Canale, Juan I.; Apesteguía, Sebastián; Smith, Nathan D.; Hu, Dongyu; Makovicky, Peter J. (25 November 2020). "Osteohistological analyses reveal diverse strategies of theropod dinosaur body-size evolution". Proceedings of the Royal Society B: Biological Sciences. 287

Gorgosaurus: Beast of the Week

Today we will look at a famous meat-eater known from lots of well-preserved fossils that has helped us understand a lot about tyranosaurs over the years.  Check out Gorgosaurus libratus!

Gorgosaurus was a meat-eating dinosaur that lived in what is now Alberta, Canada, and Montana, USA, during the late Cretaceous period, between 76.6 and 75.1 million years ago.  From snout to tail adults could grow up to 30 feet (9 meters) long.  The genus name translates to "Dreadful Reptile".  The species name, libratus, translates to "balanced".

Life reconstruction in watercolors by Christopher DiPiazza of a pair of Gorgosaurus libratus.

Gorgosaurus was a member of the tyrannosaurid family, often described as a slightly smaller, more gracile relative of Tyrannosaurus.  Like all tyrannosaurids, Gorgosaurus had a series of chisel-like teeth in the frontmost portion of its jaws that are rounded in the front, but flat in the back, giving them a D-shaped cross section.  These could have been an adaptation for scraping meat off bones.  The rest of Gorgosaurus' teeth were curved, thick in cross section, and serrated for cutting flesh.  Gorgosaurus possessed large, round eye sockets and likely had good vision in life.  It also had rough textured bone running down the top of its snout and a small, forward-facing, horn over each eye.  There was likely keratin growing over these parts of the skull in life, giving the dinosaur a more ornamented look than the skull shows.  The presence of horns on the snout and over the eyes is actually a trait common to many tyrannosaurs.  We don't know exactly what these structures were for in life, but they very well may have been for some kind of interaction within the species, either for display only or perhaps some sort of physical combat for dominance between rivals.  

Gorgosaurus skeleton on display at the Royal Tyrell Museum in Alberta, Canada.

Like all tyrannosaurids, Gorgosaurus had proportionally short arms and only two functional fingers on each hand.  It's legs, however were proportionally long and powerful, implying it was a strong distance walker and probably a fast runner in life.  Since we also have juvenile Gorgosaurus specimens on the fossil record, we know that when younger, the legs were even longer, proportional to the body, implying the younger individuals were even faster.  Because there are relatively numerous Gorgosaurus specimens in the fossil record of varying life stages, scientists were able to figure out just how fast this dinosaur grew.  It turns out that tyrannosaurids, like Gorgosaurus, continued to grow their entire lives, but went through extremely rapid growth spurts during certain parts and slowed down once reaching mature adult sizes, the fastest of these spurts they would have gained about 110 pounds in a single year!  It was also found out that Gorgosaurus spent about half of its life at juvenile size.  This has supported the idea that tyrannosaurids specialized in hunting smaller faster prey when young, and then moved on to slower, but tougher, prey when fully mature.  This also helps explain the lack of small-medium sized predators in communities where tyrannosaurids are found, because it was likely the tyrannosaurids were filling more than one predator niche depending on their maturity. 

Skeleton of a juvenile Gorgosaurus on display at the American Museum of Natural History in New York.  Note the long, slender legs.

Gorgosaurus is one of the few fossil dinosaurs scientists have been able to recover skin impressions from.  The patch of skin from Gorgosaurus would have been on the tail and shows fine, slightly raised bumps.  There is no way to tell if Gorgosaurus also had feathers or not in life since different forms of body covering can exist on different parts of an animal's body and also preserve under different conditions (for instance we have numerous dinosaur fossils that preserve feathers but no scales, yet we can infer they also had scales on certain parts of the body), but given that it is from the branch of dinosaurs that includes birds, called coelurosaurs, it very well could have.  

Photograph of Gorgosaurus skin impressions from Bell's 2017 paper.

Throughout the course of it's living on earth, Gorgosaurus would have coexisted with, and probably hunted, lots of other dinosaurs, including, but not limited to hadrosaurs, like Parasaurolophus, Lambeosaurus, and Corythosaurus, ankylosaurs, like Eouplocephalus and Anodontosaurus, and ceratopsians, like Chasmosaurus and Styracosaurus.

That is all for this week!  Feel free to leave a comment below!

References

Bell, Phil R., et al. “Tyrannosauroid Integument Reveals Conflicting Patterns of Gigantism and Feather Evolution.” Biology Letters, vol. 13, no. 6, 2017, p. 20170092., https://doi.org/10.1098/rsbl.2017.0092.

Erickson, Gregory M., GM; Makovicky, Peter J.; Currie, Philip J.; Norell, Mark A.; Yerby, Scott A.; Brochu, Christopher A. (2004). "Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs". Nature. 430 (7001): 772–775.

Lambe, Lawrence M. (1914). "On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of Stephanosaurus marginatus from the same horizon". Ottawa Naturalist. 28: 13–20.

Holtz, Thomas R. (2004). "Tyrannosauroidea". In Weishampel, David B.; Dodson, Peter; Osmólska Halszka (eds.). The Dinosauria (Second ed.). Berkeley: University of California Press. pp. 111–136.

Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology. 1: 1–34.

Voris, Jared T., Zelenitsky, Darla K., Therrien, Francois, Ridgely, Ryan C., Currie, Phillip J., Witmer, Lawrence M. Two exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids. Jou Ver Pal (2022).

Amargasaurus: Beast of the Week

This week we will be checking out a sauropod with a truly striking style!  Introducing Amargasaurus cazaui! 

Amargasaurus was a plant-eating dinosaur that lived in what is now Argentina during the early Cretaceous period, roughly 130 million years ago.  It measured about 33 feet (10 meters) long from snout to tail.  It's name translates to "Amarga reptile" in reference to La Amarga, the geological formation as well as the town near where this dinosaur's bones were discovered in Argentina.  "Amarga" in Spanish means "bitter". 

Watercolor reconstruction of Amargasaurus by Christopher DiPiazza

The most unique and striking feature about Amargasaurus is the fact that it had two rows of upward-facing spines down its neck and part of its back.  These spines were actually part of the animal's vertebrae!  The spines growing out of this dinosaur's neck were pointed and spike-like, but as they go further down the back, they become blunter and flatter.  Nobody is exactly sure what purpose these structures would have served in life.  However, many think they were most likely some sort of display adaptation within the species.  Reconstructions of these spines have varied over the years as scientists studied the fossils and came up with more updated ideas.  The oldest versions had skin connecting the spines, like a pair of fins running down the back.  Then it was argued they were more likely not covered in skin, but individually covered in keratin, forming a series of spikes.  The latest study from 2022 examined the spines more closely, finding that their texture and the growth rings in their cross section suggests that there were fibers connecting them in life, and they were likely covered in some sort of soft tissue, forming a sail-like structure.    

Amargasaurus skeletal mount.

Other interesting features about Amargasaurus is that it actually had a relatively shorter neck proportionally when compared to other sauropod dinosaurs.  Like its relatives, however, it likely possessed a set of teeth concentrated at the front of the mouth that were peg-shaped.  This is a good mechanism for raking leaves and other foliage off of branches while feeding. Only part of the skull was found, unfortunately.  This is common for sauropods with their big, bulky bodies and tiny, delicate heads that are easily destroyed during fossilization.

In 2014, a team of paleontologists actually scanned the inside of the part of Amargasaurus' skull that was found, which included the braincase.  They were able to see the space that would have held the dinosaur's inner ear canals, which would control the sense of balance.  The shape of the inner ears plus how the vertebra fit together suggest that Amargasaurus actually would have held its neck horizontally out in front, rather than upright, as sauropods are often imagined.  The head also would have also been oriented with the snout facing directly downwards.  This doesn't mean that Amargasaurus wasn't capable of moving its head and neck around in different poses depending on its behavior, of course, but rather a suggestion on its most comfortable default resting position.  

That's it for this week!  As always feel free to comment below!

References

Cerda, Ignacio A.; Novas, Fernando E.; Carballido, José Luis; Salgado, Leonardo (March 24, 2022). "Osteohistology of the hyperelongate hemispinous processes of Amargasaurus cazaui (Dinosauria: Sauropoda): Implications for soft tissue reconstruction and functional significance". Journal of Anatomy: joa.13659.

Novas, Fernando E. (2009). The age of dinosaurs in South America. Bloomington: Indiana University Press. ISBN 978-0-253-35289-7.

Paulina Carabajal, A.; Carballido, J.L.; Currie, P.J. (2014). "Braincase, neuroanatomy, and neck posture of Amargasaurus cazaui (Sauropoda, Dicraeosauridae) and its implications for understanding head posture in sauropods". Journal of Vertebrate Paleontology. 34 (4): 870–882.

Upchurch, P., Barrett, P.M, & Dodson, P. 2004. Sauropoda. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 259–322.

Lystrosaurus: Beast of the Week

This week we'll be checking out a wildly successful animal who's lineage managed to make it through the most powerful mass extinction in earth's history.  Say hello to Lystrosaurus!

Lystrosaurus was a plant-eating synapsid (group of animals that includes, but isn't limited to modern mammals) that lived during the late Permian era and the early Triassic period, between 255 and 250 million years ago.  Several species within the genus have been identified and their fossils have been found in Antarctica, China, India, Russia, and South Africa.  Among the species known, their sizes range from less than a meter (about 2 feet) up to 2.5 meters (about 8 feet) long from beak to tail.  The genus name translates to "Shovel Reptile" in reference to the wide, flat beaks they possessed.  

Lystrosaurus murrayi lived during the early Triassic in what is now South Africa.  Watercolor reconstruction by Christopher DiPiazza.

Lystrosaurus was a member of the dicynodont group of synapsids.  Dicynodonts walked on all fours and are notable for having squat robust bodies, broad short beaks, and two downward facing tusks that grew from either side of their upper beak.  Other than these tusks, they had no other teeth in their short jaws.  Lystrosaurus had thick limb bones and would have stood and walked with a semi-sprawling gait, similar to some reptiles today.  It is thought that at least some species of Lystrosaurus were strong diggers and may have lived in burrows.  

You may have noticed that the areas Lystrosaurus have been discovered spans a wide range.  Keep in mind that during the time Lystrosaurus was alive, the continents we now today were actually attached in one "supercontinent", called Pangea.  In fact, it the existence of Pangea and the concept of the continents moving over millions of years, called plate tectonics, was proven partially thanks to the same species of Lystrosaurus fossils all of the same age being discovered in Africa, India, and China, which would have been connected at the time it was alive. (either that or a short-limbed creature adapted to digging swam across oceans...which definitely didn't happen.)

Lystrosaurus georgi lived during the early Triassic in what is now Russia.  Skeletal mount on display at Museums Victoria in Australia.

Perhaps most impressive about Lystrosaurus, was the fact that it was just so abundant in the ecosystems that it lived. Even more impressive, some species, like Lystrosaurus curvatus, from Africa, managed to survive though the mass extinction event at the end of the Permian Era, into the Triassic, 251 million years ago.  Considered the most powerful extinction in earth's history, this event resulted in over 70% of land vertebrates being wiped out.  It included largest volcanic eruptions in earth's history, with 2 million square km (770 square miles) of earth's surface being covered in lava, and tons of carbon dioxide released in the atmosphere, choking out any animals that weren't outright incinerated.  Once into the Triassic, the surviving Lystrosaurus kept flourishing, becoming some of the most common and widespread land vertebrates in the fossil record.  In some fossil sites from the early Triassic, Lystrosaurus bones make up 95% of all the vertebrate fossils present.

So how did this little synapsid manage to survive the nastiest extinction event in earth's history? Scientists have a few ideas.  One of which is Lystrosaurus' burrowing lifestyle, and how hiding underground may have allowed it to avoid being choked out by all the extra carbon dioxide released that killed other land animals.  Another clue is that by looking at growth rings in cross sections of Lystrosaurus tusks, paleontologists can tell that Lystrosaurus could go into a torpor state, like hibernation, possibly allowing them to literally sleep through the global catastrophe while other animals starved to death. 

When alive, Lystrosaurus, would have probably relied on hiding underground or in the underbrush to avoid predators.  It also may have been able to use its tusks to defend itself if it needed to.  The late Permian Lystrosaurus would have watched out for sabre-toothed gorgonopsids.  The Triassic species were probably preyed on by the crocodile-like rauisuchians, and even some of the first dinosaurs.

That's all for this week! Feel free to leave a question or comment below!

References

Botha, J. & Smith, R.M.H. (2005). "Lystrosaurus species composition across the Permo–Triassic boundary in the Karoo Basin of South Africa". Lethaia. 40 (2): 125–137.

Cluver, Michael Albert (1978). Fossil reptiles of the South African Karoo. The South African Museum.

Damiani, R. J.; Neveling, J.; Modesto, S.P. & Yates, A.M. (2004). "Barendskraal, a diverse amniote locality from the Lystrosaurus assemblage zone, Early Triassic of South Africa". Palaeontologia Africana. 39: 53–62.

Surkov, M.V.; Kalandadze, N.N. Of & Benton, M.J. (June 2005). "Lystrosaurus georgi, a dicynodont from the Lower Triassic of Russia" (PDF). Journal of Vertebrate Paleontology. 25 (2): 402–413.

Trewick, Steve (2016). "Plate Tectonics in Biogeography". International Encyclopedia of Geography: People, the Earth, Environment and Technology. John Wiley & Sons, Ltd. pp. 1–9.

Whitney, Megan R.; Sidor, Christian A. (27 August 2020). "Evidence of torpor in the tusks of Lystrosaurus from the Early Triassic of Antarctica". Communications Biology. 3 (1): 471.

Pyroraptor: Beast of the Week

 This week we'll be checking out a mysterious little predator.  Say hello to Pyroraptor olympius!

Pyroraptor was a meat-eating dinosaur that lived in what is now Southern France and possibly other parts of Europe, including Northern Spain, during the late Cretaceous period, about 70.6 million years ago.  When alive it would have measured roughly 5 feet (1.5m) long from snout to tail.  The genus name translates to "Fire Thief" because its bones were discovered shortly after a forest fire it the area.  The species name is in reference to the mountain, Monte Olympe, near where it was found.  

Watercolor life reconstruction of Pyroraptor olympius by Christopher DiPiazza.

Pyroraptor is unfortunately only known from scant fossil material, including a few limb bones, a few teeth, and the second toe claw.  The teeth were curved, blade-like, and had serrations on both edges, an adaptation for slicing meat.  The second toe claw is was long and hook-shaped, probably for pinning down prey.  Despite not being much, this is still enough material to deduct that Pyroraptor was likely a kind of dromaeosaur, the bird-like predatory dinosaurs famous for having enlarged, retractable "killer claws" on the second digit of each foot. (Velociraptor and Deinonychus are the most famous examples of this family.)  Based on other, better-preserved dromaeosaur specimens, we can also deduct that Pyroraptor would have almost certainly been covered in feathers in life, including long wing feathers on the hands and arms.  

Photos of teeth assigned to Pyroraptor discovered in Spain from the 2015 paper by Angelica Torices et al.

The part of Europe that included Pyroraptor's habitat would have been a series of islands during the late Cretaceous.  The dinosaurs and other land animals that lived there likely would have been under different environmental pressures from those on the mainland, and therefore may have evolved differently.  Pyroraptor's smaller size may have been an adaptation for surviving on small islands since prey may have been have been more limited.  It also may have behaved differently, possibly using different hunting styles and exploiting different food sources compared to dromaeosaurs on the mainland.  We can only guess, but it's fun to think about!

References

Allain, R., and Taquet, P. (2000). "A new genus of Dromaeosauridae (Dinosauria, Theropoda) from the Upper Cretaceous of France." Journal of Vertebrate Paleontology, 20: 404-407. [June 27, 2000]

Csiki-Sava, Z.; Buffetaut, E.; Ősi, A.; Pereda-Suberbiola, X.; Brusatte, S.L. (2015). "Island life in the Cretaceous-faunal composition, biostratigraphy, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago". ZooKeys (469): 1–161.

Pei, Rui; Li, Quanguo; Meng, Qingjin; Gao, Ke-Qin; Norell, Mark A. (2014-12-22). "A New Specimen of Microraptor (Theropoda: Dromaeosauridae) from the Lower Cretaceous of Western Liaoning, China". American Museum Novitates (3821): 1–28.

Torices, Angelica. “Theropod Dinosaurs from the Upper Cretaceous of the South Pyrenees Basin of Spain.” Acta Palaeontologica Polonica, 2013, https://doi.org/10.4202/app.2012.0121.