Regaliceratops: Beast of the Week

 This week we will be checking out a ceratopsian with unique and beautiful ornamentation.  Make way for Regaliceratops peterhewsi!

Regaliceratops was a ceratopsian dinosaur that lived in what is now Alberta, Canada, during the late Cretaceous period between 69 and 67 million years ago.  It is estimated to have measured about 16 feet (5 m) long and would have eaten plants when alive.  The genus name translates to "Regal Horned Face" because of the arrangement of horns around the edge of its frill resembles a crown.  The species name, peterhewsi, honors the geologist, Peter Hews, who initially discovered its remains.  Before it was officially named, Regaliceratops was casually nicknamed "Hellboy" by the paleontologists excavating and prepping its fossils because it was a particularly difficult job due to the unfavorable geology and intricate details of the skull they had to work around without damaging the specimen.  (not necessarily after the comic book character, Hellboy, even though the dinosaur and the character both have horns...which don't actually resemble each other anyway.)

Regaliceratops reconstruction in watercolor by Christopher DiPiazza.

Regaliceratops had a circular frill which was adorned with a row of flat, almond-shaped horns growing from its perimeter, including one in the middle, which is unusual since most ceratopsian frill ornamentation is paired on either side of the frill.  The center horn also is keeled down its midline, another unusual trait for ceratopsian ornamentation.  Regaliceratops had a relatively long horn growing from the top of its snout, and a small, narrow, forward-curving horns over its eyes.  As is the case with most ceratospians, experts think this elaborate headgear was connected to some kind of communication within the species, and possibly for combat within the species.  This doesn't mean a ceratopsian wouldn't have used its horns to defend itself against predators, but the drastic diversity from species to species over time in ceratopsian headgear suggests they were being selected for something more display-related.  If they were primarily for defense it would be more expected for them to be more similar to each other. (like ankylosaur armor or stegosaur tail spikes)

Skull of Regaliceratops on display at the Royal Tyrrell Museum in Alberta, Canada. Photo credit Sue Sabrowski.

 

Regaliceratops is considered part of the chasmosaurine line of ceratopsians, which typically had longer frills, longer brow horns, and shorter nose horns.  Regaliceratops mostly goes against this trend having a long nose horn and short brow horns with a relatively shorter frill.  Similarities in other parts of the skull, however, to chasmosaurines, especially Triceratops, confirms Regaliceratops was indeed most closely related to them.  

When alive, Regaliceratops would have shared its habitat with other dinosaurs, like the ankylosaur Anodontosaurus, fellow ceratopsian, Pachyrhinosaurus, and the small predator, Atrociraptor.  It also would have needed to look out for the largest known predator of the area, the tyrannosaurid, Albertosaurus. 

References

Brown, Caleb M.; Henderson, Donald M. (June 4, 2015). "A new horned dinosaur reveals convergent evolution in cranial ornamentation in Ceratopsidae". Current Biology. 25 (12): 1641–8.

B. Weishampel, David; M. Barrett, Paul; A. Coria, Rodolfo; Le Loeuff, Jean; Xing, Xu; Xijin, Zhao; Sahni, Ashok; P. Gomani, Elizabeth M.; R. Noto, Christopher (2004). "Dinosaur Distribution". In Weishampel, D.B.; Dodson, P.; Osmolska, H. (eds.). The Dinosauria 2nd edition. pp. 517–606.

Thescelosaurus: Beast of the Week

 This week we will be looking at a little dinosaur that definitely deserves more attention.  Check out Thescelosaurus!

Thescelosaurus was a relatively small plant-eating dinosaur that lived in what is now North America, during the latest part of the Cretaceous period, between 68 and 66 million years ago.  From beak to tail the largest specimens were almost 15 feet (4.5 meters) long.  The genus name translates to "godlike lizard/reptile" in reference to how surprised scientists were at how well preserved and complete the first studied specimen's bones were.  Thescelosaurus and its closest relatives were long thought to be part of the ornithopod group of dinosaurs. (includes more famous members like Iguanodon) More recently, however, paleontologists have found that Thescelosaurus' lineage branched off earlier than the oldest true ornithopods, despite being physically similar in appearance to them. (that being said as more information is learned about dinosaurs, this part of the family tree could change again for all we know.)

Watercolor reconstruction of Thescelosaurus neglectus by Christopher DiPiazza.

Thescelosaurus is currently known from three species, Thescelosaurus neglectus, which was the first named and lived in the United States, named after the fact that the specimen was kept in a box for years until it was formerly examined for the first time. Thescelosaurus garbanii was also from the United States but was slightly larger and more robust.  Thescelosaurus assiniboiensis was the smallest of the three species and lived in what is now Western Canada.  When alive, Thescelosaurus would have shared its environment with famous dinosaurs, like Tyrannosaurus, Triceratops, Pachycephalosaurus, Acheroraptor, and Edmontosaurus.

In general Thescelosaurus is characterized by being a pretty robust dinosaur, despite the fact that it wasn't overall a very large.  It would have walked on its hind legs, but some suggest it could have possibly moved or rested on all fours at least some of the time.  Its front limbs were relatively long and strong, and tipped with five fingers on each hand.  It had a flexible neck and a proportionally small skull with a narrow beak in the front of its jaws and teeth lining the sides ideal for shredding plants once inside the mouth. This dinosaur also had teeth at the tip of its snout, where the beak was, which may have helped it strip leaves off of stems and shoots as it ate.

Thescelosaurus skeleton on display at the Canadian Museum of Nature in Ottowa, Ontario, Canada.

Some Thescelosaurus also had overlapping bony plate-like structures on their ribs.  At first some believed these were to aid in breathing but they lack the sort of surface texture that normally would imply there were muscles attached in life.  Thanks to specimens of Thescelosaurus that weren't quite mature when they died, we know these plates may have started as cartilage and would have solidified into bone as the animal aged.  Perhaps they provided extra protection in some sort of intraspecies combat only mature individuals engaged in?  

Thescelosaurus skeletal mount on display at the Smithsonian National Museum of Natural History.  Note the bony rib plates. 

Most recently, research led by paleontologist, Clint Boyd, uncovers more than one Thescelosaurus specimens had a pair of bony, knob-like spurs growing out of each of their forearms.  These features have only been found in mature individuals so far, and therefore imply they may have been used in some sort of display or combat between rivals within a species.  This connects really nicely with the rib plates previously mentioned and it is easy to imagine two rival males squaring up and using their arms like studded maces to smash each other in the flanks, or even bear-hugging each other, over territory or mating rights.  

Watercolor reconstruction of two rival Thescelosaurus using arm spurs in combat by Christopher DiPiazza.

We also have Thescelosaurus specimens that preserved skin patches thanks to being naturally mummified after death.  Thanks to this find we know that Thescelosaurus had scaly skin on at least some of its body!  

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

References

Boyd, Clint A.; Cleland, Timothy P. (2008). "The morphology and histology of thoracic plates on neornithischian dinosaurs". Abstract with Programs - Geological Society of America; Southeast Section, 57th Annual Meeting. 40 (2): 2.Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke, Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology. 29 (3): 758–770. 

Brown; Caleb M.; Boyd, Clint A.; and Russell, Anthony P. (2011). "A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America". Zoological Journal of the Linnean Society. 163 (4): 1157–1198. 

Brown, Caleb Marshall; Evans, David C.; Ryan, Michael J.; Russell, Anthony P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology. 33 (3): 495–520. 

Galton, Peter M. (1995). "The species of the basal hypsilophodontid dinosaur Thescelosaurus Gilmore (Ornithischia: Ornithopoda) from the Late Cretaceous of North America". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 198 (3): 297–311. 

Galton, Peter M. (1997). "Cranial anatomy of the basal hypsilophodontid dinosaur Thescelosaurus neglectus Gilmore (Ornithischia; Ornithopoda) from the Upper Cretaceous of North America". Revue Paléobiologie, Genève. 16 (1): 231–258.

Stein, Walter W. “The Paleontology, Geology and Taphonomy of the Tooth Draw Deposit; Hell Creek Formation (Maastrictian), Butte County, South Dakota. .” The Journal of Paleontological Sciences, Apr. 2021, pp. 1–108.