Hadrosauroid eggs and embryos from the Upper Cretaceous (Maastrichtian) of Jiangxi Province, China

Abstract

Background Dinosaur eggs containing embryos are rare, limiting our understanding of dinosaur development. Recently, a clutch of subspherical dinosaur eggs was discovered while blasting for a construction project in the Upper Cretaceous red beds (Hekou Formation) of the Ganzhou Basin, Jiangxi Province, China. At least two of the eggs contain identifiable hadrosauroid embryos, described here for the first time. Results The eggs, attributable to Spheroolithidae indet., are thin-walled and small (~ 660 mL) compared to those of Lambeosaurinae. The shape of the embryonic squamosal is reminiscent of that seen in the Late Cretaceous hadrosauroids Levnesovia transoxiana, Tanius sinensis, and Nanningosaurus dashiensis, suggestive of possible affinities. Conclusion The small size of the eggs and embryos, similar to those of Hadrosaurinae, indicates that the larger eggs and hatchlings typical of Lambeosaurinae are evolutionarily derived.

Calvarial suture interdigitation in hadrosaurids (Ornithischia: Ornithopoda): Perspectives through ontogeny and evolution

“…The following clade definitions are used when discussing phylogenetic positions of taxa in this study: Iguanodontia, all ornithopods more closely related to Parasaurolophus walkeri than to Hypsilophodon foxii or Thescelosaurus neglectus (Sereno, 2005); Hadrosauridae, the most recent common ancestor of Saurolophus osborni and P. walkeri and all descendants (Sereno, 1998); Hadrosaurinae, all hadrosaurids more closely related to S. osborni than to P. walker (Sereno, 1998); Lambeosaurinae, all hadrosaurids more closely related to P. walkeri than to S. osborni (Sereno, 1998). We follow Xing et al (2022) in using the term Hadrosaurinae over Saurolophinae given that these clades are functionally the same except for the inclusion of Hadrosaurus in Hadrosaurinae.…”

Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile

“…The niches of hadrosaurids likely overlapped onto those of non-hadrosaurids, while non-hadrosaurids like CPAP 3054 were often smaller-sized, and had smaller tooth plates with fewer tooth positions, taking up a smaller proportion of the jaw (39,40,47,48). Given the importance of the tooth-jaw apparatus, this could explain why in the Maastrichtian non-hadrosaurids had disappeared in North America (41, 88), while a single species is known from Asia (89, 90). Non-hadrosaurids like Telmatosaurus persisted into the Maastrichtian of Europe, but this is argued to have resulted from their geographic isolation in islands (35, 50).…”