A new paper:
Highlights
New remains hadrosaurid ornithopods from the Latest Cretaceous of the Lago Colhuà Huapi Formation (Chubut Group, Golfo San Jorge Basin) are reported.
The distribution of Late Cretaceous ornithopods in southern South America was directly related to paleoenvironmental conditions.
The proximity of the paleoshoreline, could have favored hadrosaurids over earlier-diverging ornithopods such as elasmarians.
The Atlantic marine transgression may have played an important role in the distribution of hadrosaurids.
Abstract
We describe and incorporate fragmentary new cranial and postcranial materials of hadrosaurid ornithopods into the non-avian dinosaur assemblage of the Upper Cretaceous (ConiacianâMaastrichtian) Lago Colhuà Huapi Formation of central Patagonia, south-central Chubut Province, Argentina. The fossils come from the upper part of the formation, probably from a stratigraphic interval close to the Cretaceous/Paleogene boundary. The materials belong to at least two ontogenetically distinct individuals that are assigned to Hadrosauridae due to their possession of anatomical features that characterize this derived ornithopod group. Sedimentological inferences reveal that the paleoenvironment of these hadrosaurids was characterized by high-sinuosity, meandering-type fluvial channels, whereas palynological data suggest the existence of low-energy freshwater bodies in the floodplains of these rivers and a warm and humid paleoclimate. The deposition of the upper part of the Lago Colhuà Huapi Formation was probably influenced by the Patagonian Atlantic marine transgression, which may have played an important role in the distribution of this sedimentary unit. The new Lago Colhuà Huapi Formation hadrosaurid specimens constitute the most stratigraphically recent records of this clade from Argentina. The materials contribute to the interpretation of Upper Cretaceous hadrosaurid paleobiogeography in Patagonian basins; moreover, sedimentological and palynological data suggest that paleoenvironmental conditions may have exerted an important influence on South American hadrosaur distribution, supporting hypotheses of ornithopod faunal turnover during the Late Cretaceous of central Patagonia. Finally, the new remains add to the generally depauperate record of Late Cretaceous ornithopods in the Southern Hemisphere.
====