Slaughteria eruptens Butler, 1978

Davis, Brian M. & Cifelli, Richard L., 2011, Reappraisal of the tribosphenidan mammals from the Trinity Group (Aptian-Albian) of Texas and Oklahoma, Acta Palaeontologica Polonica 56 (3), pp. 441-462 : 455-456

Slaughteria eruptens Butler, 1978

Fig. 9 , Table 8.

Holotype: SMP−SMU 61192 , a left dentary fragment preserving the p2, p3, dp4 and dp5 (partially developed and unerupted replacement teeth at the p4–5 are visible in CT; Fig. 9E ).

Type locality: Butler Farm, north−central Texas, USA.

Type horizon: Upper Antlers Formation (Aptian–Albian).

Referred material.—PM 1098, Rp5 missing the mesial half of the protoconid; OMNH 63726, Rmx missing portions of the talonid, and OMNH 63721, Rmx (talonid only).

Emended diagnosis.—Very small tribosphenidan characterized by strongly molariform dp4 and dp5; permanent p5 premolariform but with an expanded talonid; differs from Pappotherium in smaller size, presumed presence of three molars, stronger paracristid; differs from Holoclemensia in absence of metaconid on p5, subequal paraconid and metaconid, presence of distal metacristid, and relatively smaller talonid; differs from Kermackia in absence of a metaconid on p5, subequal paraconid and metaconid, weaker distal metacristid, relatively taller trigonid, and relatively mesiodistally shorter talonid; differs from deltatheridiids in presence of five lower premolars and three molars, subequal paraconid and metaconid, and possession of entoconid.

doi:10.4202/app.2011.0037

Description

Detailed descriptions of the holotype and referred molar material of Slaughteria eruptens can be found in Davis (in press), and will not be repeated here. However, an additional premolar is herein referred, and the morphology of the rest of the hypodigm is summarized to facilitate comparisons between the various tribosphenidan taxa described in this paper.

Lower premolars: The holotype of S. eruptens (SMP−SMU 61192; Fig. 9D–E ) was interpreted by Davis (in press) to preserve the p2, p3, dp4, and dp5. Both deciduous premolars are strongly molariform but have low trigonids bearing a small, procumbent, and buccally positioned paraconid as well as a relatively broad, well developed talonid. CT data revealed the presence of two permanent premolars developing within the jaw ( Kobayashi et al. 2002; Davis [in press]. The permanent p4 is large and trenchant with a single small heel cusp, while only the tip of the principal cusp of the p5 is calcified. PM 1098 ( Fig. 9A ) is an ultimate lower premolar missing the mesial half of the principal cusp. This cusp was tall and conical; because of damage the presence or absence of a metaconid or paraconid cannot be ascertained. A crest descends the main cusp to meet a small but prominent heel cusp. This cusp is situated on the buccal side of the talonid, and is connected by a weak crest to an additional, distolingually positioned cusp. A faint ridge encloses the lingual margin of the talonid. This specimen agrees well in size with S. eruptens , and is most likely a p5 based on its semi−molariform morphology (the p4 should have a much taller, trenchant principal cusp).

Lower molars: OMNH 63726 ( Fig. 9B ) is a mostly complete lower molar, missing only portions of the talonid. The trigonid is tall and equilateral, with subequal paraconid and metaconid. The paracristid is high and strongly notched, and a distal metacristid is present. The talonid was somewhat narrower than the trigonid, is well basined, and bears a distinct entoconid.

Stratigraphic and geographic range.— Greenwood Canyon (Triconodont Gully), upper Antlers Formation (Aptian– Albian), north−central Texas, USA ; Tomato Hill ( OMNH V706 ), middle Antlers Formation (Aptian–Albian), southeastern Oklahoma, USA .

Figures

Fig. 9. The tribosphenidan Slaughteria eruptens Butler, 1978 from the Early Cretaceous of Oklahoma and Texas. A. PM 1098, Rp5 in in occlusal (A1) and lingual (A2) views. B. OMNH 63726, Rmx in occlusal (B1) and lingual (B2) views. C. OMNH 63721, Rmx in occlusal (C1) and lingual (C2) views. D. SMP−SMU 61992, left dentary fragment with p2, p3, dp4, and dp5 (holotype) in occlusal (D1) and lingual (D2) views. E. 3−D reconstruction of SMP−SMU 61992 from CT data (in lingual view, bone removed), with developing p4 and p5 indicated (modified from Davis 2011).