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[dinosaur] ?Gryposaurus alsatei, new species of hadrosaur from Texas + hadrosaur gut parasites

Ben Creisler

New papers:

Thomas M. Lehman, Steven L. Wick and Jonathan R. Wagner (2016)
Hadrosaurian dinosaurs from the Maastrichtian Javelina Formation, Big Bend National Park, Texas.  
Journal of Paleontology  (advance online publication)
DOI: http://dx.doi.org/10.1017/jpa.2016.48 

Rare remains of hadrosaurian dinosaurs previously reported from the Maastrichtian Javelina Formation of West Texas had been attributed tentatively to either Edmontosaurus or Kritosaurus. Three recently recovered specimens include substantial skull parts and postcranial skeletal elements sufficient to recognize three distinct hadrosaurs. Two species are found in the lower part of the Javelina Formation; one of these is identified as Kritosaurus sp., confirming the earlier referral of specimens to this taxon. The most complete of these specimens combines features thought to be diagnostic of both K. navajovius Brown, 1910 and 'Naashoibitosaurus' ostromi Hunt and Lucas, 1993 and exhibits some unique attributes such that its specific identity remains uncertain. A second species, documented by a single specimen found near the base of the Javelina Formation, is inadequate to confidently identify but appears to represent a 'solid-crested' saurolophine with frontals having upturned processes along the midline, similar to those that brace the posterior side of the narial crest in Saurolophus. A third hadrosaur is represented at a bonebed in the uppermost part of the Javelina Formation. Its remains are sufficient to justify designation as a new species ?Gryposaurus alsatei. The skull roof elements are similar to those in species of Gryposaurus, and although no parts of the narial crest are preserved, the bordering elements indicate that ?G. alsatei was a 'flat-headed' saurolophine. Referral of ?G. alsatei to Gryposaurus would constitute a significant temporal range extension for the genus into late Maastrichtian time, and if correct, this long-lived lineage of hadrosaurs persisted nearly to the end of Cretaceous time in West Texas. ?G. alsatei was a contemporary of Edmontosaurus, the sole terminal Cretaceous hadrosaur in the northern Great Plains region, and neither possessed the ornate narial crest that characterized many earlier hadrosaurs.


Justin Tweet, Karen Chin and A. A. Ekdale (2016)
Trace fossils of possible parasites inside the gut contents of a hadrosaurid dinosaur, Upper Cretaceous Judith River Formation, Montana.
Journal of Paleontology (advance online publication)
DOI: http://dx.doi.org/10.1017/jpa.2016.43 

Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur, Brachylophosaurus canadensis, from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are about 0.3 mm across. Many have thin calcareous linings or layers, and some exhibit fine surficial striae. At least two dozen of these trace fossils share walls with adjacent tubular traces, and this association can extend for several millimeters. While the trace fossils share some characteristics with fine rhizoliths, these features are most consistent with tiny burrows, or possibly body impressions, of worms (vermiform organisms) of uncertain biologic affinity. Such trace fossils have not been reported previously, and herein described as Parvitubulites striatus n. gen. n. sp. Either autochthonous (parasites) or allochthonous (scavengers) worms may have created the trace fossils, but taphonomic factors suggest that autochthonous burrowers are more likely. Several lines of evidence, such as constant diameters and matching directional changes, suggest that the paired trace fossils were made by two individuals moving at the same time, which implies sustained intraspecific contact. Parvitubulites striatus provides a rare record of interactions between terrestrial, meiofaunal-sized, soft-bodied invertebrates and a dinosaur carcass. The evidence that the worms may have parasitized a living hadrosaur and subsequently left traces of intraspecific behavior between individual worms adds unique information to our understanding of Mesozoic trophic interactions.