Pappotherium pattersoni Slaughter, 1965

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 : 448-450

Pappotherium pattersoni Slaughter, 1965

Fig. 5, Table 5.

Holotype: SMP−SMU 71725 , a right maxillary fragment preserving the M3 and M4.

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

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

Referred material.—PM 999, RM1 (missing protoconal region); PM 1749, LM2 (missing metastylar lobe and protoconal region); PM 1325, LM2 (protoconal region only); OMNH 61185, RM3 (missing metastylar lobe); PM 1015, LM3 (missing metastylar lobe and protoconal region); OMNH 61219, Lmx (trigonid only); OMNH 63729, Rmx (trigonid only); PM 930, Rmx (trigonid only); PM 1119, Rmx (trigonid only); PM 1249, Lmx (trigonid only).

Emended diagnosis.—Putative metatherian differing from other basal metatherians (such as Kokopellia ) in lack of twinning between hypoconid and hypoconulid, absence of buccal postcingulid, and presence of distal metacristid on lower molars; differs from deltatheroidans in subequal paraconid and metaconid on lower molars; differs from Holoclemensia in inferred presence of four molars, larger

DAVIS AND CIFELLI—REAPPRAISAL OF THE EARLY CRETACEOUS TRINITY “THERIANS” 449

1 mm

stylocone, absence of mesostyle, deeper ectoflexus, closer approximation of paracone and metacone, mesiodistally longer trigonid, subequal paraconid and metaconid, and presence of distal metacristid; differs from Slaughteria in larger size, inferred presence of four molars, and weaker paracristid.

Description

Upper molars: The M1 of Pappotherium pattersoni is represented by a single worn and broken specimen (PM 999; Fig. 5A). The width of the parastylar lobe and the position of the parastyle support the locus assignment of this molar. The paracone is much taller and slightly broader than the metacone. The paracone is closely approximated with and connected to the large stylocone by a strong and slightly notched preparacrista. The parastyle is low and situated between the other two cusps. Though the metastylar lobe is wide, the ectoflexus is shallow. There is a weak ectocingulum but no evidence of any other stylar cusps. The postmetacrista is strong and notched, but less so than in deltatheroidans. The crown is broken lingual to the paracone and metacone. The preprotocrista is wide and continuous to the parastyle, but the postprotocrista ends at the base of the metacone.

The M2 ( Fig. 5B) is less worn than the M1 but also less complete. The paracone and metacone are both large and strong, but the paracone is again taller and broader. The stylocone is a large cusp, but the parastylar lobe is much wider than on the M1. The parastyle is more prominent and positioned more directly mesial to the stylocone. A broken chip of enamel indicates the presence of a small cuspule distal to the stylocone, and connected to it by a weak crest. The remainder of the stylar shelf is missing (beyond the deepest point of the ectoflexus), and it appears that the stylar shelf was quite wide on this specimen. The postmetacrista was likely strong. The tip of the protocone is broken from the second referred M2 ( Fig. 5C), but it does preserve distinct conules positioned relatively close to the protocone. No internal cristae are present, and it appears that the postprotocrista ended at the base of the metacone. The preprotocrista is very wide, becoming more of a shelf.

doi:10.4202/app.2011.0037

The M 3 is represented by three specimens, all in differing states of preservation ( Fig. 5D–F). All are smaller than the M2. The holotype bears a complete M3, but the specimen is heavily coated in glue and appears to have lost much of its enamel. In all three specimens, the parastylar lobe is very wide, and the metacone is much smaller than the paracone. The stylocone is large but relatively smaller than on the M1–2. The parastyle is also large and is well−separated from the stylocone. The preparacrista is strong. There is some evidence of a small cuspule similar to that on the M2. The ectoflexus is much deeper than on the mesial molars, and where preserved (the holotype only), the metastylar lobe is slightly narrower than the parastylar lobe. The protoconal region on OMNH 61185 is heavier than on SMP−SMU 61725 , and while this is not likely due to preservation, there are some possible geographic differences (relating mostly to size) among the Trinity Group samples (see Discussion). The conules are distinct and positioned close to the protocone (the metaconule appears to be absent from the holotype M3, but there is breakage in that region) .

A single M4 is known, preserved along with an M3 as part of the holotype ( SMP−SMU 61725 ; Fig. 5D). The metacone and metastylar lobe are strongly reduced relative to the M3, while the paracone and parastylar lobe are wide and very prominent. The preparacrista runs to the stylocone. The protoconal region is missing from this specimen, so no other information is available .

Lower molars: Only trigonids are preserved of all lower molars referred to P. pattersoni ( Fig. 5). While there is some variation in size, none of the differences typically attributable to position are evident. The trigonid is roughly equilateral in occlusal view, with a prominent protoconid and subequal paraconid and metaconid. The paracristid is somewhat stronger and more heavily notched than the protocristid, but not to the degree seen in deltatheroidans. Cusp f is prominent and nearly vertical, while cusp e is much smaller though still distinct. From what is preserved, the cristid obliqua appears to have met the trigonid beneath the protocristid notch, and a distal metacristid is present.

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