Deccanolestes cf. robustus Prasad, Jaeger, Sahni, Gheerbrant, and Khajuria, 1994

Rana, Rajendra S. & Wilson, Gregory P., 2003, New Late Cretaceous mammals from the Intertrappean beds of Rangapur, India and paleobiogeographic framework, Acta Palaeontologica Polonica 48 (3), pp. 331-348 : 337

Deccanolestes cf. robustus Prasad, Jaeger, Sahni, Gheerbrant, and Khajuria, 1994

Table 2, Fig. 4 .

Material.—ITV/ R /Mm−6, right m1 or m2.

Distribution.—Late Cretaceous (Maastrichtian) Intertrappean beds of Naskal and Rangapur, Andhra Pradesh, India.

Description.—ITV/ R /Mm−6 is identified as a right lower molar, either m1 or m2. The roots are missing and a small portion of the lingual base of the crown is eroded. The crown is much larger than the other Rangapur specimens ( Table 2). The trigonid is just wider than and over one−and−a−half times taller than the talonid. Cusps on the trigonid are well spaced and somewhat inflated. The protoconid is the tallest cusp, but only slightly taller than the metaconid. The paraconid is small, labial, and slightly anteriorly projecting but not crest−like. The metaconid is more distally positioned than the protoconid, and its apex is somewhat lingually deflected. The protoconid is connected to the metaconid by a high protocristid, and to the paraconid by a very low paracristid. A broad notch separates the metaconid and paraconid. The anterolabial face of trigonid is slightly worn but preserves a faint anterior labial cingulid. It runs subvertically from the base of the crown below the protoconid, anterolingually toward the paraconid. It terminates below the notch formed by the paracristid. An anterior lingual cuspule is absent but the inflated base of the paraconid may have served the same function. In labial view, the trigonid appears tipped anteriorly ( Fig. 4D ).

In occlusal view, the posterior face of the trigonid contacts the talonid at an oblique angle ( Fig. 4A, B ). The talonid basin is wide but not very deep. It slopes downward in an anterolingual direction and is only weakly closed by a low entocristid on the lingual side. The talonid notch is deep. On the labial side, the cristid obliqua is higher than the entocristid and contacts the base of the trigonid just lingual to the protocristid notch below the base of the metaconid. A faint trace of a distal metacristid is present. The acute angle between the cristid obliqua and the posterior face of the trigonid forms a well−excavated hypoflexid. The hypoconid is more anterior than the entoconid and is labially shifted. The hypoconulid is closer to the entoconid than it is to the hypoconid. The hypoconid is the tallest of the talonid cusps, followed by the hypoconulid, and then the entoconid. In posterior view, the talonid is canted lingually with respect to the trigonid, and the labial margins of the talonid and protoconid are convex. A postcingulid is absent.

Discussion.—In most respects, ITV/ R /Mm−6 is very similar to the only known lower molar of D. robustus ( VPL /JU/ NKIM /14, m1). It differs from the latter in both size and in the arrangement of the talonid cusps. ITV/ R /Mm−6 is about 24% larger than VPL /JU/ NKIM /14 and has a hypoconulid that is closer to the entoconid than it is to the hypoconid ( VPL /JU/ NKIM /14 has the reverse arrangement). These differences may be due to preservational, intraspecific, or interspecific variation. Because sample sizes are still very small, we tentatively refer this specimen to D. robustus rather than to a new taxon.

Figures

Fig. 4. Deccanolestes cf. robustus. Right m1 or m2 (ITV/R/Mm−6) in occlusal (A, B), lingual (C), and labial (D) views. Scale bar 0.5 mm.