A revision of Philander (Marsupialia, Didelphidae).

Abstract

Newly available molecular sequences and morphological data suggest that Philander nigratus Thomas, 1923, is a valid species. Currently known from just eight specimens collected in the Peruvian departments of Junin and Ayacucho, P. nigratus does not appear to be closely related to either of the congeneric taxa with which it was previously synonymized.

Cranial anatomy of Andinodelphys cochabambensis, a stem metatherian from the early Palaeocene of Bolivia

“…They are longer and wider in Metachirus, Chironectes, Didelphis, Gracilinanus than in Andinodelphys. In Andinodelphys the elongated major palatine foramina are the only small palatal vacuities observed in our sample, whereas in some extant didelphids additional vacuities are present on the palatine or lateral to the major palatine foramina (e.g., Didelphis, Philander, Thylamys, Lutreolina, Tlacuatzin, Cryptonanus, Gracilinanus) (Voss & Jansa 2009). It is noteworthy that small elongated palatal vacuities, similar to those of Andinodelphys are present in Sparassocynus derivatus (Beck & Taglioretti 2019).…”

“…Palatal vacuities are absent in very few metatherian taxa. Among didelphids, they are totally missing in Caluromys and Caluromysiops, whereas they are present in all the other members of the family (Voss & Jansa 2009). They are poorly developed in Marmosa and Micoureus, in which they have the size observed in Andinodelphys.…”

“…It very slightly increases in height posteriorly, the bone having its greatest depth just anterior to the jugal-squamosal suture. However, in this region of the jugal of Andinodelphys there is no conspicuous frontal process of the jugal as is observed in Recent didelphids and dasyurids, in which it marks the posterior limit of the orbit (Wible 2003;Voss & Jansa 2009). However, a very small elevation of the dorsal edge of the jugal, posterior to the concave anterior part, demarcates the posterior limit of the orbit and could be regarded as an incipient frontal process.…”

“…Therefore, the condition of Andinodelphys differs from that in most extant didelphids (e.g. Didelphis, Metachirus, Marmosa, Philander, Thylamys), in which the supraoccipital-interparietal suture fuses very early in ontogeny (Clark & Smith 1993;Nesslinger 1956, Voss & Jansa 2009, whereas the interparietal-parietal suture remains unfused in adults. The condition is reversed in Andinodelphys.…”

“…In fact, the condition observed in Andinodelphys is reminiscent of the condition observed in some extant didelphids. However, it is noteworthy that the presence and morphology of the palatal vacuities are extremely variable in extant didelphids (Voss & Jansa 2009). They are generally absent in Caluromys and Caluromysiops (but see Voss & Jansa 2009: 94).…”