A new Arctic hadrosaurid (Dinosauria: Hadrosauridae) from the Prince Creek Formation (lower Maastrichtian) of northern Alaska

Abstract

The Liscomb bonebed in the Price Creek Formation of northern Alaska has produced thousands of individual bones of a saurolophine hadrosaurid similar to

A new saurolophine hadrosaurid (Dinosauria: Ornithopoda) from the Upper Cretaceous of Shandong, China

“…The ventral margin of the dorsal process forms the anterodorsal border of the posterior circumnarial depression, while the medial surface of this process is a flat articular face connected with the other side of premaxilla. In dorsal view, the vestibular promontory of the premaxilla expands anteroposteriorly and forms a fan-shape, as in Edmontosaurus annectens (Prieto-Márquez 2014, Mori et al 2015. This vestibular promontory separates the anterior and posterior circumnarial depression, but the lateral circumnarial depression is covered.…”

“…During hadrosaurid ontogeny, the skull becomes relatively more elongate anteroposteriorly, implying that a similar pattern took place in maxillary development (Mori et al 2015). The height (the distant from the apex of the dorsal process to the margin of tooth battery) to length (the distant from the anterior apex of the anteroventral process to the end of the ectopterygoid shelf) ratio of the maxilla is also reduced as the animal grows (Mori et al 2015). Data show that the ratio of the big maxilla of Laiyangosaurus (IVPP V 23401.1) is 0.29, while the ratio of other three small maxillae (IVPP V 23405.1, IVPP V 23403.1, IVPP V 23402.1) fall between 0.35 and 0.38, indicative of ontogeny.…”

“…The maxilla of Shantungosaurus is distinctly larger than Laiyangosaurus, and the latter also has a very shallow and anteroposteriorly expanded palatine process of the maxilla; this process is deeper and hook-like in Shantungosaurus (Hu et al 2001). During hadrosaurid ontogeny, the skull becomes relatively more elongate anteroposteriorly, implying that a similar pattern took place in maxillary development (Mori et al 2015). The height (the distant from the apex of the dorsal process to the margin of tooth battery) to length (the distant from the anterior apex of the anteroventral process to the end of the ectopterygoid shelf) ratio of the maxilla is also reduced as the animal grows (Mori et al 2015).…”

“…Laiyangosaurus has a prominent and narrow ridge on the lateral side of the nasal that borders posterodorsally and posteriorly the circumnasal depression, while the other flat-headed saurolophines, Edmontosaurus, Shantungosaurus, Kerberosaurus, and Kundurosaurus, also have a wide and flat ridge (Godefroit et al 2012, Xing et al 2014b. Ugrunaaluk (Mori et al 2015) is a new flat-headed hadrosaurid from the Price Creek Formation, northern Alaska, U.S.A. The nasal of size class 1 Ugrunaaluk and the small nasal of Laiyangosaurus are equal in size, while this element in the former also has a wide and flat lateral ridge (Mori et al 2015).…”

Preservation of Arctic dinosaur remains from the Prince Creek Formation (Alaska, USA): A reply to Fiorillo (2016)

“…We thank Anthony Fiorillo (2016) for the concerns he raised regarding our characterizations of the Liscomb bonebed fossils in our paper describing Ugrunaaluk kuukpikenis from the Prince Creek Formation of Alaska, USA (Mori et al 2016). We did not imply that the bones are not "fossilized".…”