When someone hears the word “ceratopsian” what usually come to mind is a horned giant
like Triceratops. However, it was mostly just one clade of ceratopsians, Ceratopsidae, along
with a few transitional species, that were large. Most of the other hornless ceratopsians
were actually rather small. This video is about an exception to the rule: Udanoceratops.
Udanoceratops was about four meters long, despite not being closely related to the horned
ceratopsids. Named in 1992, it was first found in the Mongolian Djadochta Formation, which
was formed between 75 to 71 million years ago. This is the same formation where such
famous species as Protoceratops, Velociraptor, and Oviraptor were found, which makes Udanoceratops’s
obscurity a bit perplexing. Fossils similar to Udanoceratops have also been found in the
Barun Goyot Formation. As mentioned earlier, Udanoceratops is estimated to have been about
four meters long. While smaller than most of the horned ceratopsids, Udanoceratops absolutely
dwarfed the other hornless ceratopsians. Udanoceratops appears to have been the size of a cow, while
most other were no larger than a sheep. Udanoceratops was also one of the larger herbivores in the
Djadochta Formation. It was only smaller than the ankylosaurs Pinacosaurus and Minotaurasaurus
and the hadrosauriod Plesiohadros. Not only did Udanoceratops lack the horns of its more
famous relatives, but its head frill was also much smaller. The skull was massive, with
a robust lower jaw that was much deeper than other ceratopsids, with a distinctly curved
shape. This would have provided attachment points for large jaw muscles, giving Udanoceratops’s
beak a powerful bite, allowing it to consume tougher vegetation than most other herbivores.
Its strong bite would have not just helped it to eat its food, but also prevent it from
becoming food. A spectacular fossil, named the Fighting Dinosaurs, preserves a Protoceratops,
Udanoceratops’s distant relative and contemporary, that died while fighting a Velociraptor. As
they died together, the Protoceratops was biting its foes arm, showing that ceratopsians
also used their beaks as weapons. With its larger size and proportionally larger jaws,
Udanoceratops’s bite would have been devastating. Even a pack of Velociraptor-sized predators
would have found it to be quiet the challenge. But that doesn’t mean Udanoceratops was
safe from predation. Fossils of a theropod similar to the medium sized tyrannosauroid
Alectrosaurus have been found in the Djadochta Formation. This predator would have been the
perfect size to threaten Udanoceratops. But while Udanoceratops would have a chance against
an Alectrosaurus-like predator, it had much worse to fear. Fossils of what seems to be
Zhuchengtyrannus, one of the largest tyrannosaurids after Tyrannosaurus rex itself, have also
been found in the Djadochta Formation. Against such a massive predator, Udanoceratops’s
only hope would to be to outrun it. Given Udanoceratops’s large nasal openings, it
likely had a good sense of smell, which would have helped it to avoid predators. This also
would have helped it to find the sparse vegetation in its desert home. It seems that other species
were not the only source of conflict for Udanoceratops. Healed injuries in an Udanoceratops skull
seems to indicate that they fought amongst each as well, likely over mates or territory.
To leave damage on the bones shows these battles were fierce. The evolution of horns and larger
frills in its relatives was likely driven by pressure to reduce such violent conflict,
replacing it with less risky displays that relied more on intimation. Despite its large
size, Udanoceratops was not part of the transition from small hornless species to the larger
horned ceratopsids. Instead, it belonged to the clade Leptoceratopsidae, who were more
distant relations of the ceratopsids than small species like Protoceratops were. Indeed,
besides Udanoceratops, other leptoceratopsids were small themselves. The majority of leptoceratopsids
were from Late Cretaceous North America. Udanoceratops was the first leptoceratopsid found outside
of the continent, though some other leptoceratopsids have since been found in Asia and even Europe.
It is thought that some leptoceratopsids were still capable of limited bipedal location,
an echo of their fully bipedal ancestors. Udanoceratops may lost this ability due to
its greater size and larger skull. However, the development of quadrupedalism in ceratopsians
is thought to be the result of needing balance their large head frills. Since Udanoceratops
had a much smaller frill, perhaps it still retained some form of bipedalism. While Udanoceratops
may have lacked the showier features of some of its relatives, it was certainly impressive
in its own right. It also showcases the diversity that existed even within the more obscure
dinosaur clades. Hopefully, the next documentary about Late Cretaceous Mongolia will remember
this unique ceratopsian. Thank you for watching. I hope you learned something interesting.
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