Tchadailurus adei, Bonis & Peigné & Mackaye & Likius & Vignaud & Brunet, 2018

Bonis, Louis de, Peigné, Stéphane, Mackaye, Hassane Taisso, Likius, Andossa, Vignaud, Patrick & Brunet, Michel, 2018, New sabre toothed Felidae (Carnivora, Mammalia) in the hominid-bearing sites of Toros Menalla (late Miocene, Chad), Geodiversitas 40 (3), pp. 67-86 : 71

Tchadailurus adei n. sp.

( Figs 1-5 ; Tables 1-7)

HOLOTYPE AND SINGLE SPECIMEN. — TM 112 -00-99: elements of a skull and partial skeleton including a left isolated I3, a left maxilla with canine, P3-M1 and a part of the zygomatic arch; right I2-I 3 in a piece of premaxilla, a fragment of right maxilla with P3-P4, and an isolated left M1. A piece of left hemi-mandible with p3-m1, a fragment of the top of the left coronoid process, a left lower canine whose crown is partly broken off; a right hemi-mandible with c-m1, and quite complete ascending ramus. There are also one piece of periotic bone and small fragments of skull including a fragment of basioccipital and the right occipital condyle. This material is somewhat fragmentary but very well preserved without any distortion and it belongs certainly to a single individual. Postcranial remains comprise: proximal fragment of left scapula; distal two-thirds of left humerus and distal fragment of right humerus; subcomplete left radius and epiphyses of right and left radius; subcomplete right ulna and fragment of diaphysis of left ulna; left scapholunar; left hamatum; right trapezium; right and left pisiforms; left Mc I to V, right Mc I, fragmentary Mc II, IV and V, Ph I; fragmentary left and right pelvis; diaphysis of right femur, distal fragment of diaphysis and distal epiphysis of left femur, left and right greater trochanters; left and right patellae; fragmentary proximal epiphysis of left and right tibias, distal fragment of diaphysis and distal epiphysis of right tibia and distal epiphysis of left tibia; fragmentary distal epiphysis of right fibula; right and left calcanei; right astragalus; subcomplete left and right cuboids; left lateral cuneiform; left intermediate cuneiform; right Mt II and Mt III, left Mt II (subcomplete), Mt IV and Mt V (subcomplete); left and right proximal phalanx of the first digit, 9 additional proximal phalanges, 6 middle phalanges of the manus, 5 middle phalanges of the pes, 7 distal phalanges; fragments of ribs; subcomplete atlas; subcomplete cervical vertebra; fragment of lumbar vertebrae; and numerous fragments of undetermined cervical/thoracic/lumbar vertebrae; 10 more or less complete caudal vertebrae.

ETYMOLOGY. — Derived from “adei”, meaning small in Goran (local language) and stressing the size difference between this species and the other machairodonts from Toros Menalla.

TYPE AND ONLY LOCALITY. — TM 112, Toros Menalla, Chad.

GEOLOGICAL AGE. — Late Miocene c. 7 Ma.

DIAGNOSIS. — Dental formula: 3/3? I, 1/1 C, 2/2 P, 1/ 1 M. Felidae characterized by a tall, flattened upper canine with mesial and distal keels, the latter with striations; absence of P2/p2; reduced p3; P4 with small pre-parastyle (ectostyle) and relatively long metastyle; mandible with reduced symphyseal angle and lowly situated mandibular condyle; extremely short and wide Mc I, with an articular surface for the trapezium that extends along half of the Mc I length; Mc I associated to a particularly robust proximal phalanx that reach up to 90% of the Mc I length.

DIFFERENTIAL DIAGNOSIS. — Differs from all the extant felids by the double keeled upper canine with striations in the distal keel; the relatively low dentary symphyseal angle (except for Neofelis ); the low position of the mandibular condyle; the short and wide Mc I; and by a first phalanx of digit I more robust (except in Prionailurus viverrinus and Leopardus pardalis ) and much longer relative to the Mc I length. Differs from Dinofelis Zdansky, 1924 species in its smaller size, a less robust upper canine and the absence of p2. Differs from the Eumachairodontia (sensu Christiansen 2013) in the absence of scimitar or large dirk upper canine and the more developed protocone of P4.

DESCRIPTION

Maxilla ( Fig. 1A )

Visible in the left part, the lateral side of the maxilla is almost flat with two small depressions above P3 and P4 respectively. The infraorbital foramen is situated 14 mm above P3 but, the higher part being broken off, we cannot indicate its precise size. The lower rim of the orbit is 24 mm above P4. The zygomatic arch is high, relatively to the size of the maxilla, and the suture between maxilla and jugal bones is totally fused although, based on tooth wear, the specimen belongs to a young adult. The diastema between the canine and P3 is 9.3 mm long.

Figures

FIG. 1. — Tchadailurus adei n. gen., n. sp., TM 112-00-99, from Toros Menalla. Left maxilla with C-M1 in labial (A1), lingual (A2), and occlusal (A3) views; right hemimandible with c-m1 in lingual (B1), labial (B2), and occlusal (B3) views; fragmentary atlas in dorsal (D1) and ventral (D2) views. Scale bar: 10 mm.

FIG. 2. — Tchadailurus adei n. gen., n. sp., TM 112-00-99, from Toros Menalla. Fragment of left humerus in anterio view (A); subcomplete right ulna in lateral (B1), medial (B2), and anterior (B3) views; subcomplete left radius in medial view (C); proximal fragment of left scapula in lateral (D1) and proximal (D2) views; left scapholunar in proximal (E1), distal (E2), and posterior (E3) views; right pisiform in lateral view (F); articulated right Mc I and first phalanx of digit I in anterior view (G). Scale bar: 10 mm.