Doolysaurus

MEANING: Dooly lizard

PERIOD: Early - Late Cretaceous

CONTINENT: Asia

Doolysaurus is a thescelosaurine dinosaur that lived around the middle of the Cretaceous Period in what is now South Korea.

Abstract from paper: The Korean dinosaur fossil record is exceptionally rich in trackways and eggs, yet skeletal remains are exceedingly rare. Two species have been described based on postcranial elements, and a taxon known from cranial materials has not yet been reported. Here, we report a new early-diverging neornithischian species, known from a small, partially articulated skeleton comprising cranial and postcranial elements as well as gastroliths. The specimen is from the mid-Cretaceous Ilseongsan Formation of Aphae Island (Aphaedo). X-ray micro-computed tomography (micro-CT) revealed the anatomy of the new species, including the first studied cranial remains of a dinosaur from Korea. The size and anatomical features of the specimen, along with histological analysis, indicate that it is not a fully grown individual, probably 0–2 years old. Gastroliths are present, with morphologies and a relative mass proposed to be consistent with a more omnivorous diet. Phylogenetic analyses recover the new species, Doolysaurus huhmini gen. et sp. nov., as a thescelosaurid. The recovery of Doolysaurus with most other Asian thescelosaurids near the base of this clade provides further evidence for its origin and early biogeography. The new discovery suggests that other small dinosaur fossils may be found at Aphaedo or at sites with similar taphonomic conditions in Korea; Doolysaurus is consistent with richer dinosaurian diversity in the Cretaceous of Korea than is represented in its rich trace fossil record.

Doolysaurus is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.

The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.

Doolysaurus is a basal ornithischian. Ornithischia is one of the two major clades of dinosaurs, sister to the saurischia, which includes theropods and sauropods. Basal ornithischians were small, lightly built herbivores or omnivores and were typically bipedal, with long hind limbs and relatively short forelimbs, well-suited for swift movement. Their body plans were often simple, lacking the extreme specializations seen in later ornithischians like ceratopsians or hadrosaurs. Many had simple, triangular skulls with leaf-shaped teeth, suitable for cropping low vegetation, and some evidence suggests they may have lived in groups. Though they form the base of the ornithischian family tree, they do not belong to any of the more derived subgroups and instead exhibit a mix of ancestral traits.

Basal ornithischians are mostly known from the Jurassic. The absence of definitively known ornithischians from the Triassic has puzzled paleontologists, though some propose that certain Triassic animals, like the silesaurs, may fill this gap. However, these relationships remain debated. As the Jurassic progressed, basal forms gave rise to a wide array of more specialized ornithischians, but these early dinosaurs remain a crucial and still somewhat mysterious chapter in the evolutionary history of the group.