Astrapotherium

MacPhee, R. D. E., Del Pino, Santiago Hernández, Kramarz, Alejandro, Forasiepi, Analía M., Bond, Mariano & Sulser, R. Benjamin, 2021, Cranial Morphology And Phylogenetic Relationships Of Trigonostylops Wortmani, An Eocene South American Native Ungulate, Bulletin of the American Museum of Natural History 2021 (449), pp. 1-185 : 15

ASTRAPOTHERIID SPECIMENS. Astrapotherium magnum AMNH VP-9278. Although the morphological gap between Middle Eocene Trigonostylops and Early-Middle Miocene Astrapotherium is wide indeed, it is important to be able to compare similarities and differences visually. To enhance our descriptions we include illustrations of the complete, but partially reconstructed, skull of Astrapotherium magnum AMNH VP-9278 (figs. 4, 27A) that Simpson (1933a) used in making his comparisons (see also Scott, 1928). Many of the areas of greatest morphological interest on this specimen are either not intact or have been heavily reconstructed (e.g., most large processes, palatal area, auditory region). Fortunately, some of these regions are adequately preserved on specimens in the MACN collection (see below).

Astrapotherium magnum MACN A 8580. This is the only specimen of Astrapotherium for which cranial CT scans are currently available (figs. 13–15). It consists of a partial adult skull lacking the entire rostrum, the right zygomatic arch, and most of the occipital condyles (last named reconstructed in plaster). The auditory region is fairly well preserved on both sides.

Astrapotherium magnum MACN A 3208. This specimen is a markedly distorted skull of a subadult. The basicranium, nearly complete on discovery, was later dissected to enable better exploration of areas of interest. The left petrosal (fig. 27B) contains the stapes (fig. 33A–D), dislodged into the labyrinth (figs. 31, 33E) and reconstructed via CT segmental data.