For much of the Cretaceous the North American landmass was effectively divided into two, by a shallow sea (Western Interior Seaway). At its greatest extent it was around 1,000 kilometres (600 miles) wide, the long, narrow landmass that represented the western part of North America is known as Laramidia and palaeontologists have amassed a huge amount of data about the abundant dinosaurs that roamed these ancient shores. The eastern landmass, Appalachia, stretched from Newfoundland in the north, to the mid-west American states, but in comparison little is known about the Appalachian dinosaur fauna.
A new species of duck-billed dinosaur has been added to the Appalachian biota, named Parrosaurus missouriensis and as the species epithet suggests, this Late Cretaceous herbivore was found in Missouri.
Very Rare Dinosaur Discovery
In contrast to the extensive, rapidly eroding “Badlands” of Montana, Wyoming and North/South Dakota, rocks of Cretaceous age from the ancient landmass of Appalachia are not exposed to any great extent in eastern North America. Dinosaur fossil bearing units are not being eroded, they remain buried under other strata and to add to this dilemma, much of the eastern part of the USA is conurbation. However, there are bright spots for palaeontologists looking for dinosaur bones. Mines, eroding rivers and construction sites can all provide opportunities for fossil discoveries. Indeed, it was the digging of a well near to the village of Glen Allen in Bollinger County, south-eastern Missouri back in 1942 that led to the finding of several dinosaur bones, the first time such fossils had been reported from the “Show Me State”.
The caudal vertebrae that were excavated from the site were thought to represent a sauropod and it was scientifically described and named Neosaurus missouriensis in 1945 (Gilmore and Stewart). It was noted that the genus name was already occupied, Neosaurus having been erected in 1869 for a Palaeozoic synapsid from France, so the scientific name was changed to Parrosaurus missouriensis.
Ironically, duck-billed dinosaur fossils had been found in North Carolina and the species Hypsibema crassicauda was erected in 1869, a review of the Glen Allen material (Baird and Horner), led to the erection of the species Hypsibema missouriensis as the Missouri fossils were confirmed to be hadrosaurid and showed similarities with the fossils that had been found in North Carolina.
More recent excavations carried out at the Glen Allen site, led by fossil expert Guy Darrough and with the support of the Field Museum of Chicago has led to the discovery of at least four individual hadrosaur specimens. The fossils found in close association in black clay represent three adults and juvenile.
The site has yielded other fascinating fossils, providing a glimpse into the fauna of Appalachia. For example, a scute (dermal armour) from a giant crocodilian has been found, fossils of turtles discovered and even the tooth of a tyrannosaur has been uncovered.
The extensive fossil material found as led to the establishment of a new species Parrosaurus missouriensis. This very notable fossil location might just prove to be a headache for the State administration, as in 2004 these fossils had been declared Missouri’s official State dinosaur when they were assigned to Hypsibema missouriensis.
The story has been widely reported and team members at Everything Dinosaur are optimistic that once the fossil material has been studied in detail and more of the specimens cleaned and prepared, then new discoveries will be made.