When people ask me why I moved from central New Jersey to Salt Lake City, Utah, I always give the same response: “For the fossils.” The Beehive State is home to an exceptional array of fossil sites, and is quite simply a gorgeous place to do fieldwork in. Most friends and acquaintances get this immediately and don’t ask any follow-up questions. But one friend of mine was confused by my motivation. “Haven’t paleontologists already found all the dinosaurs?”, he asked.
Paleontologists have been scouring North America’s western deserts for fossils since the late 19th century. The most famous dinosaurs of all – Tyrannosaurus, Triceratops, Stegosaurus, Diplodocus, and the like – were all found over a century ago in the Mesozoic rock scattered through the basin and range. That might give the impression that paleontologists have only been retracing their own tracks for the last 100 years. Yet these dinosaurs come from relatively thin slices of prehistoric time, and the rock record of the west is far richer, expansive, and mysterious than most people know.
A few months before I moved to Utah, for example, paleontologists described eight new dinosaur species from various sites in the state, and there are even more that are still on their way to publication. (Not to mention those that still hide in the rocks.) Most of the major dinosaur discoveries in the west have yet to be made, and that’s true of Mexico as well as the United States. Among the latest finds that hints how much there is yet to be uncovered is Velafrons coahuilensis, a 73.5 million year old hadrosaur found near Coahuila, Mexico.
As described by paleontologist Terry Gates and colleagues in the 2007 description of the dinosaur, getting Velafrons out of the ground was a decade-long endeavor. Field crews from the “Dinamation International Society” uncovered most of the hadrosaur’s body in excavations between 1992 and 2001. But it wasn’t until a joint effort by multiple museums returned to the quarry in 2002 that paleontologists finally got the disarticulated skull bones that allowed them to gauge just how different the Cretaceous dinosaur was from similar species.
The skeletal chassis of hadrosaurs are frustratingly similar to each other. So much so that hadrosaurs without heads are often difficult to positively identify. With the preserved skull bones, though, Gates and coauthors were able to pin Velafrons as a lamebosaur – a member of a specific hadrosaur subgroup that also contains the famous tube-crested Parasaurolophus and dome-crested Corythosaurus. Indeed, these hadrosaurs are well known for showing off rather flashy skull ornamentation.
When pieced together, the skull of Velafrons looked quite similar to that of Corythosaurus and Hypacrosaurus. In these hadrosaurs, the nasal bones rose up to create a domed, compressed helmet. Even though the Velafrons individual that Gates and collaborators studied was a juvenile, and its crest would probably have continued to change as it grew, the overall shape was similar. Details of the Velafrons skull were enough to distinguish the dinosaur from these similar forms, but, not surprisingly, the newly-named species came out as a close relative to Corythosaurus and Hypacrosaurus.
Yet Velafrons lived far south from its kin. Velafrons was part of what appears to have been a distinct radiation of southern dinosaurs during the late Campanian – between about 75 and 72 million years ago. The dinosaurs that lived in southern Utah, Texas, and Mexico during this time belonged to the same lineages as the ones found in Montana and Canada, but were different genera and species.
Judged through the bird’s eye view paleontology provides, there seems to have been some kind of barrier that isolated these Cretaceous communities into northern and southern parts, spurring dinosaur populations to diverge in distinct ways. No one yet knows what this barrier might have been. Paleontologists are still assembling this puzzle. We’re only just starting to understand the outline of dinosaur evolution during this one narrow span of time, not to mention the story of the global Cretaceous. Some of the greatest stories in dinosaur history are still waiting to be discovered.
Previous entries in the Dinosaur Alphabet series:
U is for Uteodon
T is for Torvosaurus
S is for Segisaurus
R is for Rapetosaurus
Q is for Qiaowanlong
P is for Pelecanimimus
O is for Ojoceratops
N is for Nqwebasaurus
M is for Montanoceratops
L is for Leaellynasaura
K is for Kileskus
J is for Juravenator
A-I at Dinosaur Tracking.
Gates, T., Sampson, S., Delgado de Jesús, C., Zanno, L., Eberth, D., Hernandez-Rivera, R., Aguillón Martínez, M., Kirkland, J. 2007. Velafrons coahuilensis, a new lambeosaurine hadrosaurid (Dinosauria: Ornithopoda) from the Late Campanian Cerro del Pueblo Formation, Coahuila, Mexico. Journal of Vertebrate Paleontology 27, 4: 917–930.