Dinofelis cf. aronoki, Werdelin & Lewis, 2001

O’Regan, Hannah J. & Steininger, Christine, 2017, Felidae from Cooper’s Cave, South Africa (Mammalia: Carnivora), Geodiversitas 39 (2), pp. 315-332 : 316-321

Dinofelis cf. aronoki

( Figs 1 , 2 ; Tables 1, 2, 3)

Dinofelis sp. – Lacruz et al. 2006: 94-96.

Dinofelis aff. piveteaui – O’Regan & Menter 2009: 331-340.

MATERIAL EXAMINED. — Craniodental from Coopers D (all described in Lacruz et al. (2006), with the exception of CD 15696 and CD 19265): CD 16765a+b, right premaxilla fragment with I1-I3 ( Fig. 1G ); CD 16769a+b, left Cs ( Fig. 1H ; Table 1); CD 15696, left P3 ( Fig. 1I, J ; Table 1); CD 7323a-d, right premaxilla with P3 ( Fig. 1D, E ) and partial P4 ( Fig. 1F ; Table 1); CD 19961, complete P4 ( Fig. 1 A-C; Table 1); CD 18836, rear portion of right mandible with P 4 and partial M 1 ( Fig.1K, L ; Table 2); CD 19265, left M 1 in mandible fragment ( Fig.1M, N ; Table 2). Craniodental from Drimolen, all described and figured inO’Regan & Menter (2009): DN 1012, a right maxillary fragment with complete P4 and M1, plus partial Cs and complete P3 alveoli; DN 780, right P3; DN 986, right P 4; DN 1020, posterior portion of premolar, probably right P3. Postcranial material. CD 19953, a right MT 3 ( Fig. 2A, B ; Table 3); CD 3233, a left proximal tibia ( Fig. 2 C-E; Table 3); CD 7359, a right proximal ulna ( Fig. 2F, G ); CD 038, a left ulna notch fragment. Postcrania from Drimolen described in O’Regan & Menter (2009):

B

C

H

DN 15, left distal ulna; DN 720, left distal radius; DN 86, left distal radius; DN 772, left proximal second metacarpal; DN 2149a-c, associated right tibia, astragalus and calcaneum; DN 2092, left calcaneum; DN 2571, right navicular; DN 12, left second metatarsal; DN 17, left third metatarsal; DN 14, left fourth metatarsal; DN 18, left fifth metatarsal, lacking proximal articulation.

DESCRIPTION

Craniodental material

CD 19961 ( Fig. 1 A-C). Complete P4 that has been glued across the paracone-metastyle border. It is a good fix, with no misalignment, making measurements possible ( Table 1). CD 19961 has a much reduced protocone, and a small ectoparastyle that is in line with the parastyle. The metastyle is not elongated, and has a small rounded area of enamel on its tip. The enamel is rugose.

CD 7323a, b, c, d ( Fig. 1 D-F). Series of associated right maxillary specimens. The dental specimens of a complete P3 and two fragments of a P4 were published by Lacruz et al. (2006), but their association with the maxillary fragment (CD 7323d) was not noticed at this time ( Fig. 1D, E ). Starting with CD 7323a+b (the P4) the central portion of the tooth is missing, leaving only the parastyle and metastyle. There is a large ectoparastyle with the cusp tip in line with the parastyle ( Fig. 1D ), and the metastyle is not elongated ( Fig. 1F ). In comparison with CD 19961, the ectoparastyle is larger in CD 7323 and although the end of the metastyle is curved, it is not as pronounced as CD 19961. CD 7323c is an isolated right P3shown refitted into the maxilla in Fig. 1D, E . It is shown in Fig. 3 in Lacruz et al. (2006), but note that their caption is incorrect, as it says that it shows CD 3835, another isolated P3 from the site. The anterior accessory cusps of CD 7323c are unusual, as it has two, both in line with the protocone and curving slightly lingually. They are both smaller than the posterior accessory cusp. A tiny cusplet is also present on the anterior buccal surface, and there is a small cusp present on the tip of the posterior cingulum. The maxillary fragment (CD 7323d) comprises the anterior portion of the P4 alveolus, the full P3 alveolus (into which CD 7323c refits) and the edge of the canine alveolus. The edges of the diastema are worn, but it must have been very small ( Fig. 1E ). It is not possible to see if a P2 was present. The pinch point of the maxilla is at the posterior root of the P3.

CD 16765a+b, CD 16769a+b, CD 15696, CD 18836, CD 19265 ( Fig. 1G, H ). These five craniodental specimens may be associated, based on their proximity to one another when recovered. CD 16765a+b is a right premaxilla with the roots of the I 1, I 2 and I 3 ( Fig. 1G ). All incisors would have been large; the I3 is in two pieces, but was almost the size of a small leopard canine. The I1 has a small accessory cusp on the medial lingual surface, but the rest of the crown is broken. CD 16769a+b is the central portion, including the enamel margin, of a large mediolaterally flattened canine with very strong keels on its labial and lingual surfaces ( Fig. 1H ). The keels clearly show that it is Dinofelis , and it is from a young animal, as the root was still open.

CD 15696 ( Fig. 1 I-L). Left P3, which, like CD 7323c, has an extra anterior accessory cusp, and a buccal cusplet. The anterior cusps are very low, and the cusps are slightly lingually set ( Fig. 1I, J ). There is a strong posterior cingulum. The similarity of features between CD 7323c and CD 15696 suggest that they may be antimeres.

CD 18836 ( Fig. 1K, L ; Table 2). Lower left mandible broken vertically immediately prior to the P 4, and just after the posterior portion of the M 1. The P 4 is complete, with large accessory cusps, plus a small cusp on same orientation on the tip of the posterior cingulum. The protocone has two pinched grooves on the buccal surface effectively making the edges of the cusp more blade-like ( Fig. 1K ). The paraconid of the M 1 is damaged, but it can be seen that the tooth is deeply scooped out on the lingual surface ( Fig. 1L ). There is no talonid on the protoconid. The masseteric fossa is deep and ends just below the posterior of the M 1, only the edge of the mental foramen can be seen, and it would have been under the posterior root of P 3. The inferior lingual surface of the mandible is ridged.

CD 19265 ( Fig. 1M, N ; Table 2). Very slightly worn left M 1 fitting into a buccal fragment of ramus ( Fig. 1M ). There is a small bladelet on the anterior surface of the paraconid, and a slight curve on the posterior edge of the protoconid, but no evidence of a talonid. The lingual surface of the tooth is deeply scooped ( Fig. 1N ), in the classic Dinofelis pattern. The very shallow edge of the masseteric fossa is just visible, ending just below the back of the protoconid. If this series of specimens are associated, then CD 19265 is the antimere of the broken M 1 of CD 18836, however it is slightly larger than this specimen.

Postcranial material

CD 19953 ( Fig. 2A ; Table 3). Complete right 3rd metatarsal that closely matches DN 17, an MT3 identified as Dinofelis from Drimolen ( O’Regan & Menter 2009). The only differences between the two specimens are that in CD 19953 the proximal facet curves a little more onto the anterior surface ( Fig. 2A ) and the epicondyles are larger. It also appears similar to KNM-ER 722T (identified as D. piveteaui ( Ewer, 1955) in Werdelin & Lewis 2001: fig. 20) except that the anterior is curved in CD 19953, while it appears straight in the Kenyan specimen.

CD 3233 ( Fig. 2 C-E; Table 3). Left proximal tibia with 1/3 of the shaft. There is a large protuberance on the lateral surface of the proximal articulation ( Fig. 2E ), and a deep fossa below the facets on the posterior surface. The fibular facet is large ( Fig. 2C ). Overall it looks very like DN 2149a ( Dinofelis ), except that this is from a smaller individual, and the muscle markings on the rear of the shaft are even more pronounced in CD 3233.

CD 7359 ( Fig. 2G ). Right proximal ulna fragment that is broken across the notch.It is broadened posteriorly and there is a deep fossa proximal to the notch on the medial surface ( Fig. 2G ), noted by Werdelin & Lewis (2001) as a characteristic Dinofelis trait. CD 038 is a left ulna notch fragment, which is also posteriorly broad with a fossa on the medial surface. It is from a slightly larger individual than CD 7359, but is otherwise a good match and has been assigned to Dinofelis cf. aronoki .

COMPARISONS

Craniodental comparisons are undertaken on a tooth-by-tooth basis, starting with the upper dentition.

Incisors

There is little morphology left on the premaxilla with damaged incisors (CD 16765a+b), however, it can be seen that there was a small medial accessory cusp on the I1, and that the I 3 was very large. Overall, it is slightly smaller than the holotype of D. piveteaui (KA 61).

Canines

The upper canine is very mediolaterally flattened, and very slightly (1 mm) larger than that of KA 61.

Upper P3

CD 7323c and CD 15696 are both shorter with more reduced and slightly more lingually placed anterior accessory cusps than P 3s of Dinofelis piveteaui (KA 61 and MT 06/07). In this way they are more similar to DN 780 from Drimolen. It is possible that the two Cooper’s specimens are antimeres, but they were found 10 metres apart in the deposit. The lingual bulge finishes at the junction between the protocone and anterior accessory cusp in CD 7323c and CD 15696, while in KA 61 and MT 06/07 it finishes about halfway along the protocone. In both CD 7323c and CD 15696 there is an extra, very low, anterior accessory cusp, so there are two before the protocone in both specimens. There is also an extra anterior accessory cusp visible in Motsetse specimen MT 06/07, but in this case it is a small and very sharp cusp in line with the others. Both CD 7323c and CD 15696 have tiny extra cusplets on the buccal surface, a feature that is also seen in Dinofelis piveteaui from Kromdraai (KA61) and Motsetse (MT 06/07), but not in D. barlowi ( Broom, 1937) (BF 55-23). The anterior accessory cusps of KNM ER 2612 ( D. petteri Werdelin & Lewis, 2001 ) and KNM ER 3880 ( D. aronoki ) are also small and lingually placed, but they do not have any additional cusps or cusplets (J. Kibii pers. comm.). The posterior cingulum is present but small with a cusp on the tip in CD 7323c and CD 15696. The posterior cingulum with small cusp is also present in D. petteri specimens (KNM-ER 2612 and KNM-ZP 444) and the D. aronoki type specimen (KNM-ER 3880) but is almost absent in MT 06/07 ( D. piveteaui ).

Upper P4

The two Cooper’s D upper P 4 s differ slightly. CD 19961 has a tiny protocone and all the cusps are aligned in a row like D. piveteaui , yet the metastyle is not elongated. The ectoparastyle is present and distinct, but not as clear as that of CD 7323a+b which is much larger. The type specimen of D. aronoki (ER-3880) lacks an ectoparastyle, while in D. petteri it appears variable (ER 2612 lacks an ectoparastyle, and KNM-ZP 444 has a small, centrally placed cusp in line with the parastyle [J. Kibii pers. comm.]). The lack of an ectoparastyle in D. aronoki marks a difference between this species and the southern African specimens and D. piveteaui , but it is a variable trait. O’Regan (2002) found that in a sample of 30 modern jaguars ( Panthera onca ), 25 had an ectoparastyle but it was only present in one out of 20 leopards. The metastyle is not elongated in CD 7323a+b, DN 1012 nor in D. aronoki (ER 3880) or D. petteri (ZP 444). The protocone is missing from CD 7323a+b, is small in CD 19961, and slightly larger in DN 1012. Unfortunately the protocone is broken in D. aronoki (KNM-ER 3880), and both D. petteri specimens (ER 2612, ZP 444) have a larger protocone than CD 19961. Turner (1987a) highlights the double ogival curve of the anterior edge of the paracone in Dinofelis barlowi and its absence in D. piveteaui . This feature is not present in CD 19961, DN 1012 or D. aronoki . The comparative metrics of African Dinofelis P4s are shown in Figures 3 and 4 . Fig. 3 demonstrates that metrically the Cooper’s D tooth is narrower across the protocone than all other recorded specimens, while Fig. 4 shows that the metastyle is not elongated like that of D. piveteaui , falling instead with D. barlowi and D. aronoki .

Maxilla

The postcanine diastema is short in both CD 7323d and DN 1012, making them most similar to D. piveteaui and D. petteri . Both Cooper’s D and Drimolen specimens are slightly damaged, but their diastemas would have been no more than c. 5 mm, while that of Dinofelis aronoki (KNM-ER 3880) appears to have been at least 1 cm (based on photographs although the specimen is distorted) and D. barlowi (BF 55-22) approximately 11 mm ( O’Regan & Menter 2009). The maxilla of CD 7323d is pinched at the posterior root of the P3, while in D. aronoki (KNM-ER 3880) it appears to be pinched prior to the P3 (although it is heavily reconstructed), and in DN 1012 and KA 61 it is pinched at the anterior root of the P3 ( O’Regan & Menter 2009).

Lower P 4

There is one P 4 from Cooper’s D, in the partial mandible CD 18836. In comparison with KA 62 and MT 03 (both Dinofelis piveteaui ), the Cooper’s D specimen is intermediate in size between the two. KA 62 is more robust and the cusps are clearer and larger, while in MT 03 they are lower and more rounded. They also lean slightly lingually, while those of CD 18836 are more upright, but the protocone and anterior accessory cusp are slightly backwards sloping. In KA 62 the anterior cusp is almost directly at the edge of the tooth, while in CD 18836 it is set very slightly back.The anterior portion of CD 18836 is much narrower than the posterior portion, this is also seen in MT 03 ( D. piveteaui ), KNM-ER 3880 and ER1549 (both D. aronoki ), but not in the other specimens available for study ( Dinofelis barlowi [BF 55-23], D. piveteaui (KA 62) and D. darti ( Toerien, 1955) [M 607]). The P 4 of CD 18836 has a very strong posterior cingulum, which is also seen in KA 62 and MT 03, and ER 1549 (a mandible identified as D. aronoki [ Werdelin & Lewis 2001]), but not in the other specimens.

Lower M 1

Two lower M 1 s have been recovered from Cooper’s D, both contained in ramus fragments – CD 19265 and CD 18836. These M 1 s are deeply scooped out, making the cusps appear concave on the lingual surface. They closely match the D. piveteaui lower M 1 in mandible KA 63 in size and morphology, the only slight difference is that the talonid bulge is slightly more obvious in KA 63 than in CD 19265, and no talonid is visible in CD 18836. We have observed that the protoconid is considerably longer than the paraconid in the Cooper’s D specimens, but there are few comparable specimens complete enough to metrically test this feature against other taxa. This elongation of the protoconid is also seen in ER 1549 ( D. aronoki ), but not in D. petteri (KNM-KP 30397) or ER 3880 ( D. aronoki ).

Ramus morphology

In CD 18836 the masseteric fossa is deep and ends just below the posterior of the M 1. The broken edge of a mental foramen can be seen, and would have been under the posterior root of P 3. The lingual inferior surface is ridged, a feature that is not seen in SK 335 (identified as Dinofelis sp. ), or KNM-KP 30397 ( D. petteri ), but is present in ER 3880, and may have been present in ER 1549, but this area is damaged.

DISCUSSION OF DINOFELIS REMAINS

Overall, the material from Cooper’s D is similar to both Dinofelis piveteaui and Dinofelis aronoki . The specimens from Cooper’s D and Drimolen have a clear ectoparastyle on the P4, and an elongated protoconid on the M 1. Both these features differentiate this material from the type of D. aronoki (ER 3880). On the other hand the material differs from D. piveteaui as the metastyle of the P4 is not elongated, although the protocone is greatly reduced. Overall, the similarities of the Cooper’s D and Dimolen specimens are to D. aronoki rather than D. piveteaui and have here been referred to that species. However, we note that the mandible ER 1549 from the Upper Burgi member, Koobi Fora, referred to D. aronoki by Werdelin & Lewis (2001), appears to be more similar to the Cooper’s material than it does to the type specimen of D. aronoki (ER 3880). The possibility that the variability seen in the Upper Burgi material might represent two species was noted by Werdelin & Lewis (2001: 234), but the material was not sufficient to make a distinction at the time. While we cannot be certain of intra-specific variability within Dinofelis species , owing to an overall paucity of material at any one site, these differences in the carnassials between the type material of D. aronoki and the material referred here to D. cf. aronoki , may be significant, and it is possible that the new South African material represents a new species which cannot be diagnosed on the available material. We therefore refer it to D. cf. aronoki , pending the discovery of further material, when further work may shed light on the evolution of these late machairodont species in Africa.

Figures

FIG. 1. — Craniodental specimens of Dinofelis cf. aronoki: A-C, CD 19961 in buccal (A), lingual (B) and occlusal (C) views; D, maxillary fragment CD 7323b,c, d in buccal view; E, CD 7323b, c, d in occlusal view; F, buccal view of P4 fragment CD 7323a, associated with 7323b, c, d; G, CD 16765a+b, right premaxilla fragment with roots of I1-I3; H, upper canine fragment CD 16769a+b; I, J, CD 15696, an isolated P3, in lingual (I) and buccal (J) views; K, L, CD 18836, right mandible with P4 and M1 in buccal (K) and occlusal (L) views; M, N, CD 19265, left M1 in mandible fragment in buccal (M) and occlusal (N) views. Scale bars: 1 cm.

FIG. 2. — Postcranial specimens of Dinofelis cf. aronoki: A, B, right third metatarsal (CD 19953) in medial (A) and lateral (B) views;C-E, CD 3233,left tibia in lateral (C), medial (D) and superior views (E); F, G, CD 7359 right ulna fragment in lateral (F) and medial (G) views. Scale bars: 1 cm.

FIG. 3. — Log10 total length of P4 plotted against anterior breadth at the protocone of the P4 for six African Dinofelis Zdansky, 1924 species.Data from Werdelin & Lewis (2001), Lacruz et al. (2006) and this study.

FIG. 4. — Log10 total length of P4 plotted against metastyle length of the P4 for six African Dinofelis Zdansky, 1924 species. Data from Werdelin & Lewis (2001), Lacruz et al. (2006) and this study.