FIG. 21. Trigonostylops wortmani MLP 52-X-5-98, partial rostrum with C and P1 in Cranial Morphology And Phylogenetic Relationships Of Trigonostylops Wortmani, An Eocene South American Native Ungulate

FIG. 21. Trigonostylops wortmani MLP 52-X-5-98, partial rostrum with C and P1 (roots only) and P2-4, M1, and M2 (crowns bilaterally present) in A, ventral; B, rostral; C, oblique dorsal; and D, left lateral views. In A, appearance of rostral end of palate implies but does not prove that it naturally furcated into relatively large canine-bearing processes, separated by an intervening cleft (arrow). A separate premaxillary element cannot be detected within this cleft, but specimen is distorted and actual appearance in life remains uncertain. In B, nasal aperture is dorsally damaged on both sides, but on specimen's left side its margin or sill seems to be essentially intact, especially ventrally. External wall of canine alveolus is smooth, with no evidence of a complex sutural surface for lateral maxillopremaxillary suture. Trigonostylops possessed nasals of normal proportionate length that extended to end of rostrum (B, C). In C, nasals and maxillae are not in contact along their shared borders (arrow), but this seems to be a consequence of postmortem separation of nasomaxillary sutures, not presence of intervening process of premaxilla. In D, note presence of 3–4 infraorbital foramina in a nearly linear arrangement.