Percrocuta tobieni Crusafont & Aguirre, 1971

Werdelin, Lars, 2019, Middle Miocene Carnivora and Hyaenodonta from Fort Ternan, western Kenya, Geodiversitas 41 (6), pp. 267-283 : 270-274

Percrocuta tobieni Crusafont & Aguirre, 1971

Percrocuta tobieni Crusafont & Aguirre, 1971: 55 .

TYPE SPECIMEN. — KNM-BN 1469, right mandible corpus with c, p2-m1.

TYPE LOCALITY. — Kabarsero, Ngorora Formation, Kenya.

MATERIAL EXAMINED. — KNM-FT 3362, right dp4; KNM-FT 3364, right dP3; KNM-FT 3375a, right m1; KNM-FT 3375e, left P2; KNM-FT 3408, right dP2; KNM-FT 3610, left P3; KNM-FT 3614a, right maxilla with P1 (emerging) and dP2-dP4; KNM-FT 3614b, right maxilla fragment with P3-P 4 in crypt; KNM-FT 3614c, right M1; KNM-FT 12693, left p3; KNM-FT 12694, broken left p4; KNM-FT 12695, left mandible corpus with alveolus for dp2, complete dp3-dp4, emerging m1; KNM-FT 14140, right p3.

DESCRIPTION

KNM-FT 3362 ( Fig. 3E, F )

A long, slender deciduous carnassial in which the paraconid is longer and lower than the protoconid. The metaconid is well developed and set distal to, and well separate from, the protoconid. The talonid bears small, crestiform entoconid and hypoconid. The position of the metaconid and development of the talonid identify the specimen as Percrocutidae .

Measurements. Ldp4 16.6; Wdp4 6.2.

KNM-FT 3364 ( Fig. 3 G-H)

A dP4 that is broken anteriorly. The extent of the preparastyle is not clear, but it appears to have formed a distinct cusp. The parastyle cusp is large and triangular. It is located mesiolingual to the paracone. The protocone is reduced to a low lingual bump. The paracone is the tallest cusp and is rhomboid in occlusal view. The preparacrista is strong. The metastyle is long, straight and low. There are no distinct cingula.

Measurements. LdP4 18.3+; WadP4 7.3; WbldP4 5.7; LpdP4 5.6; LmdP4 6.4.

KNM-FT 3375a

A trenchant carnassial with paraconid and protoconid that are subequal in length, with the latter being the taller of the two. The metaconid is absent. The talonid is very reduced and shows evidence of only a very small and weak hypoconid. The mesial root is large and the distal root is small.

Measurements. Lm1 22.4; Wm1 11.3; Ltm1 18.9.

KNM-FT 3375e

A small, robust P2 with prominently wrinkled enamel. The mesial accessory cusp is small and low, set mesiolingually and appressed to the main cusp. The latter is pyramidal, with strong mesiolingual and distal crests. The distal accessory cusp is low but sharp and is less appressed to the main cusp than is the mesial accessory cusp.

Measurements. LP2 12.0; WP2 7.8.

KNM-FT 3408

A long, relatively slender dP2. The mesial accessory cusp is very low and set mesiolingual to the main cusp. In occlusal view the mesial shelf of the tooth is longer than the distal shelf. The main cusp is tall and ovoid in occlusal outline. The distal accessory cusp is more distinct than the mesial accessory cusp but set in a truncated shelf. There is a lingual root that in occlusal view forms a bulge near the base of the enamel on the lingual side.

Measurements. LdP2 11.6; WdP2 6.4.

KNM-FT 3610

A tall, pyramidal P3. The mesial accessory cusp is low but distinct, set mesiolingual to the main cusp and only somewhat appressed to it. The main cusp is tall and nearly round in occlusal outline. It has strongly wrinkled enamel. The distal accessory cusp is strong, somewhat trenchant and set away from the main cusp in a short shelf.

Measurements. LP3 17.8; WP3 12.0.

KNM-FT 3614a ( Fig. 3C, D )

This maxilla includes three deciduous teeth in position. The DP2 is in every respect similar to KNM-FT 3408 described above, except for being nearly unworn. An occlusal view clearly shows the slight lingual bulge of the lingual root. The DP3 is complete and shows the anteriormost cusp to be large, with transverse shear. The preparastyle is identical to that of KNM- FT 3375a. The protocone shelf is more distinct than in that tooth, but is still very low, with an almost obliterated cusp. The paracone is relatively shorter than in KNM-FT 3375a and the metastyle appears slightly less straight than in that tooth. The DP4 is large and subtriangular, with a distinct, though worn paracone bordered buccally by a cingulum. There is also a low, very worn metacone, and a large, crescentic protocone. The remarkable length of the root under the paracone can be seen in buccal view.

Measurements. LdP2 10.9; WdP2 6.6; LdP3 19.1; WadP311.2; WbldP3 5.3; LpdP3 6.9M LmdP3 7.2; LdP4 7.2; WdP3 13.0.

KNM-FT 3614b ( Fig. 3A, B )

This is not the same individual as KNM-FT 3614a. The P3 was clearly a large, robust tooth suitable for bone-cracking and had a low mesiolingually set accessory cusp. The P4 is long and comparatively slender. It has a small cingulum mesial to the parastyle. There is a distinct, sharp parastyle and a large, sharp paracone. The metastyle is low and lingually convex. It gradually becomes lower distally. The protocone is set lingual to the parastyle with an embayment of the mesial part of the tooth between them. There are weak cingula mesiobuccally and lingually along the mesial half of the metastyle.

The P4 of this specimen is practically indistinguishable from that of late Miocene hyaenids of the genus Hyaenictitherium and related forms. The only middle Miocene hyaenid that approaches this morphology is Thalassictis montadai ( Villalta Comella & Crusafont Pairó 1943). The P4 of this species ( Crusafont Pairó & Petter, 1969) appears more robust, lacks the anterior cingulum and has a straighter mesial face. These differences are small and I cannot exclude the possibility that this specimen represents a hyaenid. However, this would make it the oldest hyaenid specimen in Africa and in view of the demonstrated presence of Percrocuta at Fort Ternan I tentatively refer it to P. tobieni .

Measurements. LP4 31.0; WblP4 10.3; LpP4 10.1; LmP4 12.1.

KNM-FT 3614c

A small, dumbbell-shaped M1 with a large, blunt paracone and somewhat smaller protocone. The metastyle shelf is almost entirely reduced and can be seen only as a very small widening of the distal border of the tooth just distolingual to the protocone.

Measurements. LM1 7.4; WM1 20.9

KNM-FT 12693

This p3 forms a rounded rectangle in occlusal view. There is no distinct mesial accessory cusp, just a small swelling at the center of the mesial cingulum. The main cusp is worn. It is ovoid in occlusal outline and would have been pyramidal if unworn. The distal shelf is worn down and broken, so the presence and size of the distal accessory cusp cannot be determined. The distolingual shelf is large.

Measurements. Lp3 14.0+; Wp3 9.3.

KNM-FT 12694

A severely damaged tooth that can be identified as a p4 by the development of the distal shelf of the crown, which is clearly longer and better developed than the distal shelf of the p3

described above. Very little else can be said concerning the morphology of the tooth.

Measurements. Lp4 16.2+; Wp4 9.8+.

KNM-FT 12695 ( Fig. 3 I-K).

A mandibular corpus with dp3 and dp4 and an emerging m1. It also has alveoli for dp2, showing it to be two-rooted. No dp1 appears to have been present. The dp3 is a slender tooth with well developed mesial and distal accessory cusps and a sharply upturned distal cingulum cusp. The main cusp is short and has a sharp tip. The dp4 is morphologically very similar to KNM-FT 3362, described above, but the metaconid is relatively slightly smaller.

Measurements. Ldp3 13.5; Wdp3 5.7; Ldp4 15.8; Wdp4 6.3.

KNM-FT 14140

This p3 is broken mesially and distally, so the development of the accessory cusps is not clear, although the mesial one must have been quite small and the distal one situated in a short shelf. The main cusp is pyramidal.

Measurements. Lp3 14.7+; Wp3 9.5.

DISCUSSION

This material can be assigned to Percrocutidae on the basis of several features, most important of which is the morphology of the deciduous fourth premolar (dp4). This tooth was shown by Chen & Schmidt-Kittler (1983) to differ from the homologous tooth of Hyaenidae in the following: The metaconid is set distal to and well separate from the protoconid; the talonid is very short; and the talonid cusps are restricted to small buds at the distal end of the tooth. In Hyaenidae , on the other hand, the metaconid is set only slightly distal to the protoconid and appressed to it (in derived Hyaenidae such as Crocuta the dp4 metaconid is lost); the talonid is long; in primitive Hyaenidae (e.g., Hyaenictitherium), there are distinct entoconid and hypoconid and commonly a third cusp that may be an entoconulid; and in derived Hyaenidae only the entoconid is distinct. The Fort Ternan material includes two dp4 that both match the morphology of dp 4 in Percrocutidae . In addition to these features, all of the Fort Ternan percrocutid specimens are considerably more derived than contemporaneous Eurasian Hyaenidae , which at that time (ca MN 6 or early MN 7/8 depending on opinion in the European mammal zonation) were confined to small, omnivorous forms such as Protictitherium and Plioviverrops ( Turner et al. 2008): type 2 hyenas in the classification of Werdelin & Solounias (1996).

Percrocuta tobieni was described from the middle Miocene of the Ngorora Formation ( Crusafont Pairó & Aguirre 1971). Finds from this formation are dated to approximately 12.5-11 Ma ( Morales & Pickford 2005), i.e., somewhat younger than Fort Ternan. To the extent that they overlap, the Fort Ternan material does not differ in any substantial way from the Ngorora Formation material. Therefore, despite some minor differences, e.g., in the relative length of the m1 talonid, assigning the Fort Ternan material to P. tobieni appears justified. This is in agreement with, e.g., Morales & Pickford (2006), in which the faunal list for Fort Ternan includes P. tobieni as one of a number of taxa shared with the Ngorora Formation. This makes the Fort Ternan record the oldest of this species.

Thus, the taxonomic home of the Fort Ternan percrocutid is clear. However, the material is of considerable interest because it includes both lower and upper dentitions, including lower and upper deciduous teeth. This not only is the first instance of associated upper and lower deciduous teeth in Percrocutidae , but these upper deciduous teeth are the first known for Percrocutidae and allow for a consideration of the full percrocutid dentition.

The following is a comparison of the deciduous upper dentition with that of Hyaena hyaena , discussed and illustrated in Baryshnikov & Averianov (1995). Percrocuta tobieni and H. hyaena share a similar overall structure of the deciduous dentition, so the differences are all in the details, none of which are as revealing as the dp4. All the observations made are confirmed by the deciduous upper dentition of C. crocuta although the latter is more reduced and hypercarnivorous than that of either P. tobieni or H. hyaena .

dP2

This tooth is relatively larger and more robust in P. tobieni . In particular, the mesial end is broader and has a more distinct mesial accessory cusp in P. tobieni . In both taxa the tooth has a marked lingual bulge, however, this bulge is set further mesially in P. tobieni , in which the maximum width is attained directly lingual to the apex of the main cusp, whereas in H. hyaena it is set lingual to the notch between the main cusp and the distal accessory cusp. In contrast to the mesial accessory cusp, the distal one is more developed in H. hyaena than in P. tobieni .

dP3

The preparastyle is of similar size relative to the whole tooth in the two taxa but the cusp of the preparastyle in P. tobieni is distinctly transversely extended. In P. tobieni the parastyle is more prominent, triangular, and set distinctly lingual to the long axis of the paracone. In H. hyaena this cusp is less developed, round and set closer to the paracone. The paracone and metastyle are similar in the two taxa, but they differ in the position of the protocone. In P. tobieni the protocone is centered lingual to the notch between parastyle and paracone, whereas in H. hyaena the protocone is set lingual to the apex of the paracone. This obviously reflects a difference in the position of the lingual root of the dP3.

dP4

The dP4 of P. tobieni is more buccolingually extended than the dP4 of H. hyaena This means that the dP4 of the extant species is more triangular in occlusal outline that it is in P. tobieni . The dP4 of P. tobieni has a larger protocone and a more bowed distal edge than dP4 of H. hyaena .

Upper dentition

The permanent upper dentition of P. tobieni , previously unknown, presents no remarkable features, except one: that it is practically indistinguishable from that of late Miocene Hyaenidae such as Hyaenictitherium or Lycyaena. In particular, it does not share with other, more derived Percrocutidae the reduced and distally shifted protocone of P4, an observation that has consequences for our understanding of the evolution of the family.

Figures

FIG. 3. — Percrocuta tobieni from Fort Ternan: A, B, KNM-FT 3614A, right maxilla with P4 in lingual (A) and occlusal (B) views; C, D, KNM-FT 3614B, right maxilla with dP2-dP4 in lingual (C) and occlusal (D) views; E, F, KNM-FT 3362, right dp4 in occlusal (E) and lingual (F) views; G, H, KNM-FT 3364, right dP3 in occlusal (G) and lingual (H) views; I, J, left mandibular corpus with dp3-dp4 in occlusal (I), buccal (J), and lingual (K) views. Scale bar: A-D, I-K, 50 mm; E-H, 10 mm.