Trionyx foveatus

Leidy, J., 1860, Extinct vertebrata from the Judith River and Great Lignite formations of Nebraska., Transactions of the American Philosophical Society 11, pp. 139-154 : 148-149

Trionyx foveatus .

Among the fossils of Dr. Hayden’s Judith River Collection, there are a number of small fragments of costal and sternal plates , having much resemblance to the corresponding parts of our living soft-shelled Turtles, forming the genus Trionyx .

The exterior surface of the fragments of costal plates, ( figure 2, plate 11 ,) is impressed with shallow pits, except near the borders of the plates. The pits are smaller and rounded at the vertebral extremities of the latter, and become larger outwardly, assuming a polyhedral, often oblong and reniform outline. The fragments of the sternal plates, ( figure 1, plate 11 ,) have their exterior surface covered with short vermicular ridges, which recall a remote appearance to Arabic letters. One of the fragments of a costal plate, apparently the third or fourth, represented in figure 2 , is almost 11 lines wide, and 2 lines thick. Two fragments of a hyposternal plate, ( figure 1 ,) are 3 lines in thickness.

In association with the remains of several other genera of Turtles, and of some other animals in the Great Lignite Tertiary Basin, near Long Lake, below Fort Clark, Nebraska, Dr. Hayden obtained small fragments of the carapace or osseous shell of a Turtle, not distinguishable from those referred to, Trionyx foveatus . The specimens are too imperfect positively to determine whether they actually belong to the same species. Fragments of a last costal plate, represented in figure 3, plate 11 , measures 4 lines in thickness, and are closely foveated on the exterior surface, in the manner described in the account of the corresponding plates of Trionyx foveatus from the Judith River Explanation of Figures, Plate 11.

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Figures 1—3. Fragments of the carapace and sternum of Trionyx foveatus , of the natural size.

Figure 1. Two fragments of a hyposternal plate; an ideal outline given in the restored condition.

Figure 2. Fragment of a left costal plate.

Figure 3. Fragment of the last right costal plate, supposed to belong to the same species as the preceding

Figures

1-3. Trionyx foveatus 4.Emys obscurus 5-7. Compsemys victus. 9-19 Crocodilus humilis. 20-23. Lepidotus occidentalis. 24-30 Mylognathus priscus