Mayulestes

Ladevèze, Sandrine, 2007, Petrosal bones of metatherian mammals from the Late Palaeocene of Itaboraí (Brazil), and a cladistic analysis of petrosal features in metatherians, Zoological Journal of the Linnean Society 150 (1), pp. 85-115 : 105

( MAYULESTES (TYPE II

(PUCADELPHYS, ANDINODELPHYS)))

This clade is supported by four unambiguous synapomorphies.

The internal carotid artery groove is deep and excavated on the anterior pole of the promontorium (10 0> 1, RI = 0.600). This well-developed sulcus for the internal carotid artery was described by de Muizon et al. (1997) in Pucadelphys , Andinodelphys , and Mayulestes . Moreover, such a sulcus was reported in borhyaenids ( Rougier et al., 1998), Type-I petrosals ( Ladevèze, 2004), and Type-III petrosals.

A deep fossa on the lateral expansion of the pars canalicularis (‘lateral trough’) was observed exclusively in these metatherians (15 0> 1, RI = 1.000).

The squamosal develops a medial process in the tympanic cavity (52 0> 1, RI = 1.000). As this feature is not available in most of the considered taxa, it is an autapomorphy of this clade.

The jugular foramen is markedly larger than the fenestra cochleae (53 0> 1, RI = 0.600) in Pucadelphys , Andinodelphys , Mayulestes , and borhyaenids ( Rougier et al., 1998), this feature being convergent with Didelphis , Perameles , and Echymipera .