Dental Structure of the Late Cretaceous (Maastrichtian) Guitarfish (Neoselachii: Batoidea)Myledaphus pustulosusfrom the Hell Creek Formation of Garfield County, Montana

2018 ◽  
Vol 121 (3-4) ◽  
pp. 279-296
Author(s):  
Brian L. Hoffman ◽  
Jeffrey S. Jensen ◽  
Scott A. Hageman
Keyword(s):  
Late Cretaceous ◽  
Hell Creek Formation ◽  
Garfield County

Pelecypods of the Hell Creek Formation (Uppermost Cretaceous) of Garfield County, Montana

1976 ◽  
Vol 13 (2) ◽  
pp. 365-388 ◽  
Author(s):  
Loris S. Russell
Keyword(s):  
Vertebrate Fauna ◽  
Hell Creek Formation ◽  
Garfield County

The Hell Creek Formation of eastern Montana, which forms the top of the Cretaceous section, contains in addition to a rich vertebrate fauna a distinctive assemblage of pelecypods, made up of three species of Plesielliptio, one of Rhabdotophorus, two of Plethobasus, one of Quadrula, nine of Proparreysia, one of Obovaria?, one of Corbicula, and one of Sphaerium. Many of the species show distinctive ornamentation, analogous to that of living Unionacea in the Mississippi drainage. One species of Plesielliptio, one of Proparreysia, and one of Sphaerium are new. There is some community of species with the faunas of the Lance and Black Buttes formations of Wyoming, less with the older Cretaceous assemblages, and none with the abundant mollusks of the Paleocene Fort Union formations.

scholarly journals The shell morphology of the latest Cretaceous (Maastrichtian) trionychid turtle Helopanoplia distincta

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4169 ◽  
Author(s):  
Walter G. Joyce ◽  
Tyler R. Lyson
Keyword(s):  
Phylogenetic Analysis ◽  
North Dakota ◽  
Late Cretaceous ◽  
Type Specimen ◽  
Shell Morphology ◽  
Surface Sculpture ◽  
Fine Grained ◽  
Hell Creek Formation ◽  
The Past ◽  
Metaplastic Bone

Background Helopanoplia distincta is an extinct soft-shelled turtle (Pan-Trionychidae) for which the type specimen is a fragmentary costal and the inguinal notch portion of the left hypoplastron from the Late Cretaceous (Maastrichtian) Lance Formation of Wyoming, USA that bear a distinct surface sculpture pattern consisting of raised tubercles. Over the course of the past few decades, a number of additional, fragmentary specimens from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Montana and North Dakota have been referred to this taxon based on the presence of these tubercles, but a more complete understanding of the anatomy and phylogenetic relationships of this distinctive soft-shelled turtle is still outstanding. Methods We here figure and describe shell remains of eight fossils referable to Helopanoplia distincta from the Hell Creek Formation of Montana and North Dakota that, in combination, document nearly all aspects of the shell morphology of this taxon. We furthermore explore the relationships of this fossil turtle by inserting it into a modified phylogenetic analysis of pan-trionychid relationships. Results The new fossil material thoroughly supports the validity of Helopanoplia distincta. In addition to its unique surface sculpture pattern, this turtle can be diagnosed relative to all other named pan-trionychids by the presence of a distinct corner along the margin of costals II, the complete covering of costal ribs I–VI by metaplastic bone, midline contact of the main plastral elements, hyoplastral shoulder, presence of a lateral, upturned margin on the hyo/hypoplastron that is covered dorsally and laterally by sculptured metaplastic bone, a single, lateral hyoplastral process, and the apomorphic presence of fine scallops along the margin of costals VIII, formation of a laterally embraced, rounded nuchal, anteriorly rounded costals I, distally expanded costals II, and narrow costals VII. A phylogenetic analysis places Helopanoplia distincta as sister to the clade formed by Plastomenus thomasii and Hutchemys spp., thereby confirming its identity as a plastomenid. The vast majority of Helopanoplia distincta material has been recovered from fine-grained overbank deposits, thereby supporting the hypothesis that this turtle favored ponded waters.

New material of Gilmoremys lancensis nov. comb. (Testudines: Trionychidae) from the Hell Creek Formation and the diagnosis of plastomenid turtles

2011 ◽  
Vol 85 (3) ◽  
pp. 442-459 ◽  
Author(s):  
Walter G. Joyce ◽  
Tyler R. Lyson
Keyword(s):  
Phylogenetic Analysis ◽  
North America ◽  
North Dakota ◽  
Late Cretaceous ◽  
Hell Creek Formation ◽  
Secondary Palate ◽  
New Material

Plastomenidae is a poorly diagnosed clade of extinct soft-shelled turtles (Trionychidae) known from the Campanian to Eocene of North America. Five skulls, a mandible, two carapaces, and numerous plastral remains from the Hell Creek Formation (Late Cretaceous, Maastrichtian) of North Dakota and Montana are referable to Gilmoremys lancensis nov. comb., a taxon previously known from a carapace and xiphiplastron only. Gilmoremys lancensis is diagnosed by a carapace that is covered by elongate sinusoidal grooves, distally expanded second costals, hyoplastral shoulders, an extensive secondary palate with accessory ridges, an extremely elongate mandible, a contribution of the parietal to the wall of the orbit, and a posterior ossified narial canal. A phylogenetic analysis of all well-known plastomenid turtles establishes Gilmoremys lancensis as the most basal known plastomenid and reveals that cranial characters are more reliable in diagnosing plastomenid turtles, in particular the contribution of the parietal to the orbit wall and the extensive secondary palate. All plastomenid turtles with a locked entoplastron are placed in Hutchemys. Assuming that all taxa are monophyletic, the phylogenetic analysis implies that the G. lancensis lineage is the only one to go extinct at the K/T boundary, whereas the four remaining plastomenid lineages survive. Extensive ghost ranges are nevertheless apparent. Taphonomic considerations indicate that G. lancensis was a riverine turtle, whereas more derived plastomenids preferred swampy habitats.

E.D. Cope's 1893 Expedition to the Dakotas Revisited

1990 ◽  
Vol 9 (1) ◽  
pp. 57-61
Author(s):  
Anthony Fiorillo ◽  
Edward Daeschler
Keyword(s):  
South Dakota ◽  
North Dakota ◽  
Late Cretaceous ◽  
Natural Sciences ◽  
Vertebrate Paleontology ◽  
Hell Creek Formation ◽  
Insight Into ◽  
Academy Of Natural Sciences

Recently an uncatalogued cache of fossil reptile material was discovered in the vertebrate paleontology collection at the Academy of Natural Sciences of Philadelphia. Evidence obtained from handwritten notes on the newspaper in which the specimens were wrapped indicates that the specimens are part of the collection made by Edward Drinker Cope on his expedition to the Dakotas and Oklahoma in 1893. These fossils were collected in the vicinity of Fort Yates, North Dakota, and Hump Creek, South Dakota, and are predominantly from the Hell Creek Formation (Maastrichtian: Late Cretaceous). No fossils from the Oklahoma segment of Cope's journey were found in the collection. Details of the Dakota segment of the expedition are reconstructed from correspondence written by Cope while he was in the field and from notes on some of the field wrappings of these newly discovered specimens. These materials are significant to the Academy of Natural Sciences since they provide insight into an aspect of Academy history which had been previously lost.

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