Trionyx vagans Cope 1874
Creators: name: Lambe L., M.
Publisher: name: Zenodo
Year: 1902
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Testudines
Trionychidae
Trionyx
Trionyx vagans

description: Plate I, figs. 3 and 4. <i>Trionyx vagans</i>, Cope. 1874. Bull., <i>U</i>. S. <i>Geol</i>. <i>Surv</i>. <i>Terrs</i>., No. 2, <i>p</i>. 27: and 1875, Vertebrata <i>of</i> Cretaceous <i>Formations</i> of the <i>West</i>, p. 96, pi. vi, figs. 13 and 14. <i>Trionyx vagans</i>, Lambe. 1902. <i>Geol</i>. <i>Survey</i> of Canada, Summary <i>Report</i> for 1901, p. 8], pis. iii and iv. This species was first described from " a ntimber of fragments <i>of</i> costal boues and perhaps of sternals also from the " Lignite Cretaceous of <i>Colorado</i>; near the mouth of the Big Horn river, Montana; Long lake, Nebraska; found at the <i>last</i> two localities by <i>Dr</i>. Hayden." Later, in 18 <i>Y</i> 5,in "TheVertebrata of the Cretaceous Formations of the West" thesamedescription appears; this time with figures of two fragments of costal bones. <i>A</i> carapace (fig. 3) referable to this species, was obtained in 1901, from the Belly River series of Red Deer river below Berry creek. It is broader than <i>long</i>, the breadth <i>exceeding</i> the <i>length</i> by more than one-sixth, and is only moderately convex. In outline, as seen from above, <i>it</i> is flat behind with the sides curving broadly <i>to</i> the front margin, at the centre of which there is a shallow concavity. <i>The</i> shell protrudes where the ribs pass outward from beneath, causing the lateral margin to be sinuous, the sinuosity being most marked toward the front in the <i>first</i>, second and third pairs of costal plates. Of the eight pairs of costals, the first costals are the broadest at the inner ends, whilst the <i>fifth</i> are the broadest <i>distally</i>. The seventh costals are extremely narrow throughout their <i>length</i> and the eighth pair is w^ <i>ell</i> developed. The first costals increase in breadth rather suddenly at their outer ends and are separated by a divided <i>first</i> neural plate. <i>The</i> neurals gradually decrease in breadth to the fifth^ their sides being not so nearly parallel to each other as those of the corresponding plates in T.foveatus. The sixth and last neural is very much reduced in size and is irregularly oval m outline. Of the protruding rib-ends, all the six of the <i>left</i> side were secured, in a fair state of preservation, except the one belonging <i>to</i> the <i>first</i> costal and <i>it</i> was obtained in part. The rib-heads are well developed. In the figure, the nuchal plate is represented as entire. <i>Of</i> the carapace under consideration, the central part only of the nuchal plate, extending from the margin in front to the suture behind, was found, but fortunately the <i>left</i> end of a nuchal, of another individual of similar size, showing the <i>left</i> front margin and the suture between the plate and the <i>first</i> costal with part of the latter adherent, supplied the deficiency. The sculpture consists <i>of</i> a network of narrow ridges, ramifying and <i>inosculating</i> so as to enclose small, sunken areae of <i>irregular</i> shape and size, the arese being generally wider than the ridges are broad. The frequent confluence of a varying number of arete results in a more open pattern, the ridges at times showing a tendency to run in parallel lines. The sculpture is not so distinctly defined near the sides of the carapace as <i>it</i> is toward and at the centre and anteriorly, but in the hinder part <i>it</i> is more decidedly rugose, the ridges being here higher and the enclosed areae <i>larger</i>. Near the intercostal.sutures, more particularly in the inner halves of the costal bones, the scrrlpture is partially effaced and consists of <i>low</i>, poorly defined parallel ridges at right angles to the sutures, forming a distinct border, with a maximum breadth of about 5 mm. <i>A</i> smooth border. broadest at the sides of the carapace aud narrowest in front, extends along the whole of the peripheral edge. As regards a divided first neural in species of this genus, it is interesting to note that Lydekker, in describing T. melttensis, from the Miocene of Malta, in 1891 ^Quarterly- Journal of the G-eological Society, voL xlvii, p. 37, iig. 1), mentions the occurrence in the Miocene species of a divided first neural, and remarks 37) that " all the fossil species (p. hitherto described, of which the entire carapace is known, agree with the normal type in having but a single long neural between the first pair of costals." [table omitted] Belly River series, Eed Deer River, 1897, 1898 and 1901; besides the carapace above described, separate costals and neurals, and parts of the endoskeleton. Also in 1880, Professor John Macoun, neurals and fragments of coatals, from Mackay creek, near Walsh, a station on the C. P. R., about twenty-eight miles east of Medicine Hat; aud in 1881, Dr. G-. M. Duwsou, from Belly river, N. W.T. (No. 41), fragments of costal bones.
description: Published as part of <i>Lambe L. M., 1902, New genera and species from the Belly River Series (mid-Cretaceous), pp. 25-81 in Geological Survey of Canada Contributions to Canadian Palaeontology 3</i> on pages 36-38, DOI: 10.5281/zenodo.3233762