Arkansas’s state dinosaur officially named

What’s more, they note that it’s most similar to early ornithomimosaurs or ostrich-mimics, a group of fast-running omnivorous theropods. Ostrich-mimics looked remarkably similar to ostriches but retained long tails and clawed fingers. Like other early ornithomimosaurs, Arkansaurus has spreading toes and a narrow central metatarsal. In later ornithomimosaurs, the foot becomes extremely narrow and the central metatarsal is pinched at its upper end by the inner and outer metatarsals.

Arkansaurus was about the same size as a living ostrich but had differences in addition to the long tail and clawed fingers. For instance, the later ostrich-mimics were all toothless, but Arkansaurus may have retained teeth like other early members of the lineage whose foot bones it most resembles. Fossils of other ostrich-mimics show that they were covered in shaggy hair-like feathers, and also had larger pennaceous feathers on their arms.

The Trinity Formation was deposited in the Early Cretaceous Period, approximately 110 million years ago. At the time, sea level was higher and this part of Arkansas was a forested plain crossed by large rivers just north of the Gulf of Mexico. No other dinosaurs have been named from the Trinity Formation in Arkansas, but rocks of a similar age in nearby parts of Texas and Oklahoma have produced fossils of the large raptor Deinonychus and burly iguanodont Tenontosaurus, found throughout most of North America. They also preserve the large carnivore Acrocanthosaurus and the long-necked Pleurocoelus.

Even though Arkansaurus was only recently named, it wasn’t unknown to the scientific community and the public. In fact, Arkansaurus was declared the state dinosaur in 2017, before Hunt-Foster and Quinn’s publication. Hunt-Foster and colleagues hope to publish more research on North American ornithomimosaurs, including possible close relations of Arkansaurus.

Read the original research in the Journal of Vertebrate Paleontology.

Pete
Buchholz

Senior Writer

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