A new genus and species of small-bodied ornithopod dinosaur has been described from a partial jawbone unearthed in Texas, the United States.
Model of the ornithopod dinosaur Qantassaurus intrepidus, a distant relative of Ampelognathus coheni. Image credit: Paleocolour.
Ampelognathus coheni lived during the mid-Cretaceous period, around 96 million years ago, along the shore of a shallow seaway that divided North America into east and west landmasses at the time.
“The ‘mid’ Cretaceous marked a time of great change in North American terrestrial ecosystems,” said University of Wisconsin-Parkside paleontologist Christopher Noto and his colleagues.
“Vertebrate species with Asian origins began traversing the newly established connection of Beringia and appear in the North American fossil record, angiosperms were on their rise to dominance in terrestrial floras, and previously diverse North American groups declined or disappeared from the fossil record.”
“The intrusion of the Western Interior Seaway during the Cenomanian (100.5-93.9 million years ago) divided the continent into the landmasses of Appalachia to the east and Laramidia to the west, creating the conditions for independent evolution of the terrestrial biota on each side of the Western Interior Seaway until its large-scale regression in Maastrichtian time (72.1-66 million years ago).”
Ampelognathus coheni was a member of the dinosaur clade Ornithopoda and was the sister species to the group of ornithopods consisting of Thescelosaurus and Iguanodontia.
A mostly complete left jawbone of the new species was collected from exposures of the Lewisville Formation (Woodbine Group) along the Grapevine Lake emergency spillway, in northern Tarrant County, Texas.
“Sediments of the Woodbine Group exposed in northeastern Texas were deposited along the southwestern margin of Appalachia as a series of near-shore, shoreline, distal lowland swamp, lake, and fluvial deposits during a regression of the Western Interior Seaway in early and middle Cenomanian time,” the paleontologists said.
“The Lewisville Formation (upper Woodbine Group) preserves the most diverse terrestrial fossil assemblage known from Appalachia, but remains of small ornithischian dinosaurs had been conspicuously absent from it.”
According to the team, Ampelognathus coheni is the first small-bodied ornithopod dinosaur discovered from the Lewisville Formation.
“The significance of this discovery is that it provides a previously missing but predicted element of that ancient ecosystem,” Dr. Noto said.
“Naming a new species is always exciting, because it means we’re adding new information to science.”
“Ampelognathus coheni is important because it represents the first small-bodied plant-eater to be identified from the Woodbine Group.”
“Up until this point we had very few herbivores and only one of them was a dinosaur, so it presented something of a mystery.”
“This fossil helps fill in that gap and furthers our understanding of how the terrestrial ecosystem in the Woodbine was structured over 95 million years ago.”
The discovery is described in a paper published October 13, 2023 in the Journal of Vertebrate Paleontology.
Ronald S. Tykoski et al. The first small-bodied ornithopod dinosaur from the Lewisville Formation (middle Cenomanian) of Texas. Journal of Vertebrate Paleontology, published online October 13, 2023; doi: 10.1080/02724634.2023.2257238
Source : Breaking Science News