Megantereon whitei (Broom, 1937)

O’Regan, Hannah J. & Steininger, Christine, 2017, Felidae from Cooper’s Cave, South Africa (Mammalia: Carnivora), Geodiversitas 39 (2), pp. 315-332 : 324-325

cf. Megantereon whitei

MATERIAL EXAMINED. — Craniodental. CD 10497, left I3 ( Fig. 5E ). Postcranial. CD 1415, right tibia ( Table 3); CD 1156, right 2nd Metatarsal, CD 3268, left 2 nd Metatarsal ( Table 3).

DESCRIPTION AND TAXONOMIC ASSIGNMENT

CD 10497 is a complete I3 that closely matches KA 64, a crushed Megantereon cranium from Kromdraai A. However, CD 10497 has two cusps on the medial surface ( Fig. 5E ) rather than the one seen in KA 64. It is most likely that this is simply an aberrant individual, but for this reason the specimen is assigned cf. Megantereon whitei . CD 1415 is the damaged distal portion of a tibia, with the epiphyseal fusion line still visible. The shaft is rounded in cross-section, like that of KB 5333T ( Megantereon whitei ), while those of Dinofelis (DN 2149a and 16201M) are much more triangular. The distal articulation is broad and there are two sections to the fibula facet, like that of KB 5333T. Overall it is most like KB 5333T and is therefore assigned to cf. Megantereon . CD 1156 is a right 2nd metatarsal, lacking the distal condyle and with some damage to the proximal articulation. The shaft is less rounded than that of a modern leopard (AZ 1063), but is similar to that of KB 5339A, and the position and shape of the MT3 facets match those of the Megantereon specimen. However, it is substantially smaller than KB 5339A, hence its referral as cf. Megantereon . CD 3268 is a proximal left 2nd metatarsal and half of the shaft. The proximal articulation is extended dorsally, behind the main facet. This extension is also seen in Megantereon (KB 5339A) but not in leopard or puma. It is therefore assigned to cf. Megantereon .

MACHAIRODONTINAE indet.

MATERIAL EXAMINED. — Cranial. CD 3835, right P3 ( Fig. 5 F-G; Table 1); CD 1514, left posterior mandible fragment with M 1 roots in alveoli (Figured in Lacruz et al. 2006: fig 5; Table 2).

Postcranial. CD 1368, right unciform; CD 7708, left unciform; CD 717, left proximal 2nd Metacarpal ( Table 3); CD 1500, right proximal 2 nd Metacarpal ( Table 3); CD 1524 right proximal 3 rd Metacarpal ( Table 3); CD 5703, left proximal 3rd Metacarpal ( Table 3); CD 7354, right proximal 4 th Metacarpal ( Table 3); CD 3271, complete right 5th Metacarpal ( Table 3); CD 682, left proximal 5th metacarpal ( Table 3); CD 1501, 1 st phalanx fragment.

DESCRIPTION AND TAXONOMIC ASSIGNMENT

CD 3835 ( Fig. 5F, G ) is a P3, published by Lacruz et al. (2006) as Dinofelis sp. , but note that this is not the tooth shown in their figure 3 (the specimen numbers were transposed and their figure 3 shows CD 7323c, a clear Dinofelis tooth). CD 3835 is highly likely to be from a machairodont, but the morphology differs from the other D. cf. aronoki specimens and the possibility that it is Megantereon cannot be excluded. CD 1514 is an edentulous mandible fragment, broken at the P 4 and lacking the mandibular angle and top portion of the ascending ramus. The M 1 alveolus is very large, longer than CD 18836 (a complete M 1), yet the ramus itself is very shallow. The edges of the alveolus are very sharp, perhaps suggesting some sort of infection, which may have increased the alveolar margins slightly. Alternatively, it may just be remodelling following the eruption of the tooth. The inferior margin of the ramus is curved, and there is no sign of the lingual ridge that is present in CD 18836 and M 607 ( D. darti from Makapansgat). It is apparent that the M 1 roots were not complete, indicating that this was a young animal at death. This specimen was published as Dinofelis sp. by Lacruz et al. (2006), but the shallow mandible in combination with the size of the carnassial makes this assignment doubtful. It is not Megantereon , as it is too large, and the inferior margin of the ramus is curved rather than straight. The alveolus would fit the Motsetse D. piveteaui carnassial, but is much longer than any other D. piveteaui or D. barlowi specimen. However, in KA 63, the inferior border of the ramus is straighter than CD 1514, and the shape of the masseteric fossa is very different. It is clearly from a young animal, which makes assignment to species difficult and the possibility that it is a young Homotherium cannot be excluded. It has therefore been referred to Machairodontinae indet.

Ten postcranial specimens are also assigned to Machairodontinae indet. Unciforms CD 1368 and CD 7708 appear to be antimeres and are smaller than a modern leopard, but are larger and different to caracal. An unnumbered Dinofelis unciform from Makapansgat is much squarer and slightly more twisted than the Cooper’s specimens. They are very similar to the inner view of the Senéze M. cultridens specimen figured in Christiansen & Adolfssen (2007: fig. 19M), but differ from the outer view of the same bone (2007: fig. 19N), for this reason they are assigned as Machairodontinae indet. Four right metacarpals CD 1500, CD 1524, CD 7354 and CD 3271 refit to form the proximal portion of a front foot, referred to here as ‘the paw’. All four specimens in the paw are slightly smaller and have proximal articulations that are narrower medio-laterally than is seen in the modern leopard, puma and cheetah. They are much more gracile than specimens assigned to Dinofelis and appear similar to the Senéze Megantereon cultridens material illustrated in Christiansen & Adolfssen (2007). They are also slightly more gracile than KB 5333U, the only metacarpal assigned to Megantereon that is available for comparison. As the craniodental Megantereon material from Coopers shows that it is a small cat, perhaps gracility in the postcrania is also to be expected, but in the absence of better comparative material they are here assigned to Machairodontinae indet., with the recognition that they may be Megantereon . CD 717 is a leopard-sized 2nd metacarpal that is slightly more robust than the ‘paw’ ( Table 3), but less robust than KB 5333U ( Megantereon ). There are minor differences in morphology between it and CD 1500, but they are much more similar to each other than to any other specimens. CD 5703 is a proximal 3rd metacarpal that is very similar to CD 1524 and is clearly not leopard or cheetah. CD 682 is a proximal left 5th metacarpal that is very similar to CD 3271, but also similar to Makapansgat specimen ‘14’ identified as Dinofelis . CD 1501 is the proximal part of a dew claw first phalanx. It has two clear proximal facets, while lion and leopard have only one. It is larger than the cheetah and is therefore most likely to be machairodont.

Subfamily PANTHERINAE Pocock, 1917

Figures

FIG. 5. — Craniodental felid specimens; A-D, Megantereon whitei (Broom, 1937); A, CD 5963, buccal view of right mandible; B, CD 5997, buccal view of left mandible; C, D, CD 10452 in buccal (C) and lingual (D) views of lower M; E, cf. Megantereon whitei, CD 10497, left upper I3 with two cusplets on medial surface; 1 F, G, Machairodontinae indet.,CD 3835,right upper P3 in lingual (F) and occlusal (G) views;Acinonyx jubatus(Schreber,1775),CD 3871, left upper P4 lacking protocone in occlusal (H) and lingual (I) views;J, K, Felis sp.: CD 675,right mandible with lower P3 and partial P4 in buccal (J) and lingual (K) views. Scale bars: 1 cm.