Deccanolestes, Prasad and Sahni, 1988

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 : 337-338

Deccanolestes ? sp.

Table 2, Fig. 5 .

Material.—ITV/ R /Mm−9, left m1 or m2; ITV/ R /Mm−8, right m1 or m2.

Distribution.—Late Cretaceous (Maastrichtian) Intertrappean beds of Rangapur, Andhra Pradesh, India. Description.—ITV/ R /Mm−9 is identified as a left lower molar, either m1 or m2 ( Fig. 5A ). The specimen is well−preserved, except that the anterior root is broken. Paraconid and metaconid are nearly equal in height and slightly shorter than the protoconid. The paraconid is positioned slightly labial relative to the metaconid but does not project anteriorly. The metaconid is robust and positioned slightly posterior relative to the protoconid. The trigonid is anteroposteriorly compressed, but a broad U−shaped notch separates the paraconid and metaconid. A protocristid connects the protoconid and metaconid, and a taller, transverse paracristid connects the protoconid and paraconid. A strong wear facet is visible on the anterior face of the trigonid. In lingual view, the base of the trigonid is level, rather than rising anteriorly ( Fig. 5A 3). The trigonid is not tipped forward relative to the talonid. The contact between the posterior face of the trigonid and the talonid is slightly oblique. A distinct cuspule is present low on the anterior face of the trigonid.

The cristid obliqua is strong and contacts the trigonid below the protocristid notch. A distal metacristid is not evident. The entoconid and hypoconulid are nearly equal in height and more developed than the hypoconid. Because the hypoconid is not very anterolabially shifted, the hypoflexid is not deep. In lingual view, the talonid notch is broad and U−shaped, rather than deep and V−shaped ( Fig. 5A 3). In occlusal view, the posthypocristid and postentocristid appear sharp ( Fig. 5A 1, A 2). The hypoconulid is slightly closer to the entoconid than to the hypoconid. The entocristid and cristid obliqua enclose the deep talonid basin. The basin is a deep circular bowl rather than an anterolingual slope. In posterior view, the labial margin of the protoconid is convex. A postcingulid is absent.

ITV/ R /Mm−8 is identified as an isolated right lower molar, either m1 or m2 ( Fig. 5B ). The specimen is not as well preserved as the other lower molar ( ITV / R /Mm−9). Both roots are missing and the apices of the metaconid and the hypoconulid are chipped. Although the tip of the metaconid is missing, it is clear that the protoconid is the tallest cusp, followed by the metaconid, and a somewhat smaller paraconid. The paraconid is anteriorly projecting and is positioned directly anterior to the metaconid. The metaconid is posterior relative to the protoconid. The trigonid is not anteroposteriorly compressed. The paracristid is a high, sharp, V−shaped crest. A strong wear facet is present on the anterior face of the trigonid. The protocristid is very high and sharp. A deep, broad, V−shaped notch separates the paraconid and metaconid. In labial view, the trigonid is tipped forward relative to the talonid ( Fig. 5B 4 ). In occlusal view, the contact between the posterior face of the trigonid and the talonid is oblique ( Fig. 5B 1, B 2). A small cuspule is present on the anterior face of the trigonid.

The low cristid obliqua contacts the posterior face of the trigonid below the metaconid. The hypoflexid is very deep. A distal metacristid is present. Although the tip of the hypoconulid is broken, it appears that the hypoconid and hypoconulid were nearly equal in height. The entoconid is slightly shorter. The hypoconid is anterolabially shifted, and the entoconid is anteriorly shifted. The hypoconulid is equidistant from the hypoconid and entoconid. The posthypocristid and postentocristid are low, but the entocristid is rather high. The latter forms the lingual wall for the talonid basin, and consequently, there is no talonid notch. The talonid basin is shallow and slopes lingually and slightly anteriorly. A postcingulid is absent.

Discussion.—Both specimens ( ITV / R /Mm−9, ITV/ R /Mm−8) are similar in size and somewhat similar in morphology to the lower molars of Deccanolestes hislopi . However, distinct differences prevent us from confidently placing the specimens in that genus. ITV/ R /Mm−9 differs from Deccanolestes lower molars in that the paraconid is tall, paracristid is high, hypoconid is low and more posteriorly positioned, and the trigonid and its cusps are more erect. ITV/ R /Mm−8 differs from Deccanolestes lower molars in fewer ways than ITV/ R /Mm−9 does. The paracristid and protocristid are both tall and sharp, the height difference between the trigonid and talonid is small, the hypoflexid is very well excavated, and in general, the crown edges and crests are sharp rather than rounded. We feel that these morphological differences may represent species or even generic variation, but we defer any formal taxonomic assignment until more evidence is available.

Figures

Fig. 5. Deccanolestes? sp. A. Left m1 or m2 (ITV/R/Mm−9) in occlusal (A1, A2), lingual (A3), and labial (A4) views. B. Right m1 or m2 (ITV/R/Mm−8) in occlusal (B1, B2), lingual (B3), and labial (B4) views. Hatched areas indicate breakage. Scale bar 0.5 mm.

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.