CHAPTER XIV
Edentata
The scarcity of edentates in the Deseado beds is in striking contrast to their abundance in the Santa Cruz formation. Whereas in this latter horizon over half of the finds are edentates, in the Deseado only eight per cent. of the total collection belong to this group, and this is doubtless a larger proportion than these animals represented in the fauna; for the hundreds of small plates in a carapace, when scattered greatly, increase the chance that some part of an individual will be found, and most of the eight per cent. of finds are single plates. Most of the plates found represent armadilloes, our collection containing but one plate of a glyptodont, and no gravigrades. Ameghino’s collections present about the same relations, but in the repeated trips he found a few more traces of glyptodons and a very few gravigrades.
This scarcity of edentates can not be taken to mean that they were not developed, for they are a peculiarly South American group, and as they were developing somewhere into their great complexity, I take it to mean that the climatic conditions were unfavorable in this particular section.
As noted above, all previous finds have been isolated plates. We were fortunate enough to find one specimen consisting of a carapace with ten rows of movable plates in place, and parts of four rows of the pelvic buckler together with over fifty isolated plates. A second specimen had some fifty associated plates which were mostly from the pelvic buckler.
Dasypoda
The representatives of this group are so poorly known in the Deseado beds that Ameghino has, in general, used the generic names of the Santa Cruz for their description, and, so far as known, they are little differentiated from those genera. There is as yet no material which shows the association of skeletal parts with the carapaces. Therefore, in this paper, comparisons are made wholly on the carapace, with the expectation that the skeleton, when found, will correspond.
The Deseado species are but little less specialized than the Santa Cruz, the carapace consisting of movable overlapping bands of plates both in the anterior and body portions, while over the pelvic region the plates are fixed, do not overlap, and form a pelvic buckler.
Ameghino has described a considerable number of genera based on isolated plates, to which I refer later. The chief genera which occur in these beds are also found in the Santa Cruz, and the distinguishing features are as follows:
| Cephalic Shield | Movable Plates | Pelvic Buckler | Ornamentation | |
|---|---|---|---|---|
| Proeutatus | Plates thin, | Plates thick, | 8 + probably | “Flask” figure |
| coarsely pitted | ⅓ overlapped | 10 rows | ||
| Prozaedius | Plates thin, | 4 bands, thin | 8 rows | 3 long ridges, |
| finely pitted | ¼ overlapped | median ridge | ||
| narrow | ||||
| Stenotatus | Plates thick, | Plates thick, | 11 rows | 3 long ridges, |
| coarsely pitted | and wide | all subequal | ||
| Proeuphractus | ¼ overlapped | No buckler | ||
| Peltephilus | 19 or 21 Plates | Wide and thin | Buckler | Large shallow |
| 2 or 4horns | 2-4 wide | pits | ||