Myacyon peignei, Werdelin, 2019

Werdelin, Lars, 2019, Middle Miocene Carnivora and Hyaenodonta from Fort Ternan, western Kenya, Geodiversitas 41 (6), pp. 267-283 : 268-269

? Myacyon peignei n. sp.

( Fig. 1 )

Small amphicyonid – Shipman et al. 1981: 64.

Agnotherium sp. – Morales & Pickford 2005: 276. — Werdelin & Simpson 2009: 782. — Werdelin & Peigné 2010: 605.

Myacyon sp. I – Morales et al. 2016: 145.

HOLOTYPE. — KNM-FT 3611, left P4 ( Fig. 1 A-C).

ETYMOLOGY. — Honoring the memory of Stéphane Peigné and his achievements in the field of carnivore paleontology.

LOCALITY. — Fort Ternan (type locality) only.

STRATIGRAPHIC RANGE. — Middle Miocene; upper Serravallian; 13.7-13.8 Ma ( Pickford et al. 2006).

MATERIAL EXAMINED. — KNM-FT 3379, left m1; KNM-FT 3399, right M1; KNM-FT 3611, left P4 .

Judging by size and morphology, all three specimens represent the same taxon, but not the same individual, given their differing states of wear. The identity of this taxon has been discussed several times in the past 15 years. In 2005 Morales & Pickford described the species Agnotherium kiptalami Morales & Pickford, 2005 based on a cranium from the Middle Miocene of Kabarsero, Ngorora Formation, Tugen Hills, Kenya. At the same time, they also discussed the Fort Ternan specimens, attributing them to Agnotherium, but without assigning them to species. The attribution to Agnotherium was followed by Werdelin & Simpson (2009) and Werdelin & Peigné (2010). More recently, Morales et al. (2016) revised the Amphicyonidae of Africa. In so doing they transferred A. kiptalami to Myacyon Sudre & Hartenberger, 1992 , tentatively suggesting that the Fort Ternan specimens might also belong in that genus.

DIAGNOSIS. — Amphicyonidae of moderate size. P4 short and broad with protocone shelf well developed and extended distally to the metastyle. M1 protocone shelf short mesiodistally. m1 hypercarnivorous with low paraconid and tall protoconid. Small metaconid present, appressed to distolingual part of protoconid and jutting out distally from it. Talonid short.

DESCRIPTION

KNM-FT 3379 ( Fig. 1 D-F).

This m1 is relatively tall for its length. The paraconid is low and short with robust and slightly worn pre- and postparacristids. The paraconid is much smaller than the protoconid

in all dimensions. The protoconid, which is nearly unworn, is tall and trenchant with salient pre- and postprotocristids and a sharp apex. The metaconid is small and located at the distal end of the protoconid, appressed to it and jutting out distally. The talonid is broken distally but has a substantial hypoconid and cristid obliqua and a very low but nevertheless distinct entoconid. In occlusal view the lingual side has a wavy outline, bulging out at the center of the trigonid and between the protoconid and talonid, whereas the lingual side is convex throughout. There is a weak lingual cingulum that runs from the protoconid to the mesial end of the metaconid.

Measurements. Lm1 c. 21; Wm1 10.2; Ltm1 14.0.

KNM-FT 3399 ( Fig. 1 G-H)

This M1 has large paracone and metacone and a mesiodistally shortened lingual shelf that is worn nearly flat. In occlusal view the paracone is slightly larger than the metacone and in distal view it can be seen to be considerably taller. Both cusps are broad and pyramidal. There is a very small cusp located at the base of the lingual side of the paracone. The lingual shelf shows a crest-like, low hypocone, but the protocone cannot be discerned at all. The tooth is too worn for the development of the cingula to be determined with certainty.

Measurements. LM1 16.8; WM1 c. 20.5.

KNM-FT 3611 (holotype, Fig. 1 A-C)

Like the m1 this P4 is relatively short and tall and nearly unworn. There is a low parastyle cusp that is closely appressed to the paracone. The paracone is tall and trenchant. The metastyle is of about the same length as the paracone, but considerably lower and lacks a distinct cusp. The protocone is very low and set in a large shelf that extends from the parastyle cusp to the mesial end of the metastyle, reminiscent of the morphology of some Lutrinae . This shelf continues as a lingual cingulum to the distal end of the metastyle.

Measurements. LP4 22.9; WaP4 15.1; WblP4 9.3; LpP4 9.2; LmP4 9.0.

DISCUSSION

The specimens described above cannot be attributed to any named species of Amphicyonidae . Therefore, a new species is indicated, a conclusion also reached by Morales et al. (2016). Generic attribution is, on the other hand, a very complicated and unresolved issue. The material was attributed to Agnotherium by Morales & Pickford (2005), Werdelin & Simpson (2009), and Werdelin & Peigné (2010). Agnotherium is, however, a poorly characterized genus, despite work by, e.g., Kuss (1962). Morales et al. (2016) present sound arguments why the Fort Ternan material cannot be attributed to that genus and they tentatively assign the material to Myacyon Sudre & Hartenberger, 1992 . This is not an implausible attribution, but the holotype (and only specimen) of the type species, Myacyon dojambir, is a severely damaged distal half of a mandible corpus with m1 and damaged m2. The illustrations of this material in Sudre & Hartenberger (1992) are, in addition, entirely inadequate and their published measurements confusing. The verbal description by Sudre & Hartenberger (1992: 554) fits the Fort Ternan m1 quite well but is fairly general and the only truly distinctive character is the distally positioned metaconid. A distinctive feature of the Fort Ternan P4 is the development of the protoconid shelf, but this feature is not known in Myacyon , including ‘ Agnotherium ’ kiptalami (also reassigned to Myacyon by Morales et al. [2016]). This protocone shape bears some resemblance to a specimen from Frohnstetten, Germany attributed by Kuss (1962: fig. 5c) to Agnotherium antiquum; however, that specimen is broken and its actual shape cannot be definitively determined. In summary, I here attribute the material to? Myacyon peignei n. sp. in anticipation of more material that can definitively clarify the generic attribution.

Figures

FIG. 1. —?Myacyon peignei n. sp. from Fort Ternan:A-C, KNM-FT 3611 (holotype),left P4 in buccal (A), lingual (B) and occlusal (C) views;D-F, KNM-FT 3379, left m1 in buccal (D), lingual (E), and occlusal (F) views; G, H, KNM-FT 3399, right M1 in occlusal (G), and distal (H) views. Scale bar: 20 mm.