Dissopsalis pyroclasticus Savage, 1965

Werdelin, Lars, 2019, Middle Miocene Carnivora and Hyaenodonta from Fort Ternan, western Kenya, Geodiversitas 41 (6), pp. 267-283 : 278-280

Dissopsalis pyroclasticus Savage, 1965

Dissopsalis pyroclasticus – Savage 1965: 265.

TYPE SPECIMEN. — NHMUK M19082, Mandible corpus with p4-m3.

TYPE LOCALITY. — Kaboor (= Maboko, cf. Morales & Pickford 2017), Kenya.

MATERIAL EXAMINED. — KNM-FT 3357, left maxilla fragment with alveoli for dP1-dP2, complete dP3-dP4, alveolus for M1; KNM-FT 3375c, right P2; KNM-FT 3375f, right dP4; KNM-FT 3562b, left p3-p4; KNM-FT 3562e, left m2-m3; KNM-FT 13770, right m3; KNM-FT 13771, right m2; KNM-FT 13772, left m2; KNM-FT 14125, left m3; KNM-FT 15092, left M1. Tentatively referred specimen: KNM-FT 14217, left?dP2 .

DESCRIPTION

KNM-FT 3357

This specimen was fully described by Borths & Stevens (2017) and need not be redescribed here.

Measurements. LdP3 15.6; WdP3 9.5; LdP4 15.8; WadP4 13.0.

KNM-FT 3375c

A small, slender P2. There is no mesial accessory cusp, but a small bump on the mesial end of the cingulum. The main cusp is low but robust. The distal accessory cusp is prominent and separated from the main cusp by a wide notch. It is a little less than half the height of the main cusp. Most characteristic of the tooth is the prominent cingulum that encircles the entire crown.

Measurements. LP2 12.0; WP2 7.6.

KNM-FT 3375f

To all intents and purposes this tooth is identical in morphology to the dP4 of KNM-FT 3357 and I therefore refer to the description of the latter by Borths & Stevens (2017).

Measurements. LdP4 16.1; WadP4 14.1

KNM-FT 3562b

A corpus fragment with damaged p3-p4. The p3 has broken off and is glued in a position that is dorsal to its position in life. The p2 is short and broad. There is no mesial accessory cusp in evidence although a very small one may have been present in the unworn tooth. The main cusp is nearly round in occlusal view. It has a short distal shelf and would have had a low distal accessory cusp that is now almost completely worn down. The p4 is more elongated than p3 but is still broad and robust. The mesial end rises straight to the main cusp without a mesial accessory cusp. The main cusp is oval in occlusal view. There is no distal accessory cusp preserved although there may have been a low one in the unworn tooth.

Measurements. Lp3 14.0; Wp3 9.5; Lp4 17.4; Wp4 10.6.

KNM-FT 3562e

This corpus fragment includes heavily worn m2-m3. The m2 is short and robust. The paraconid is heavily worn, with a wear facet that includes the apex of the cusp and continues mesially to the mesial end of the tooth. The apex of the protoconid is also worn and broken, making it impossible to adequately compare the proportions of paraconid and protoconid. No metaconid is in evidence. The talonid is long and includes a ridge-like hypoconid, as well as entoconid and entoconulid. The m3 is tall and short. The paraconid and protoconid are about equal in length but the protoconid is the taller cusp. There is a distinct cingulum cusp on the mesiobuccal side of the paraconid. There is no metaconid and the talonid is reduced and ‘V’-shaped.

Measurements. Lm2 15.6; Wm2 9.3; Ltm2 11.9; Lm3 19.3; Wm3 10.1; Ltm3 16.8.

KNM-FT 13770 ( Fig. 5 G-I)

This tooth is identical in morphology to the m3 of KNM- FT 3562e except that the paraconid of KNM-FT 13770 is distinctly longer than the protoconid.

Measurements. Lm3 20.2; Wm3 9.5; Ltm3 15.5.

KNM-FT 13771 ( Fig. 5 D-F)

This tooth is identical in morphology to the m2 of KNM- FT 3562e but has a very interesting wear pattern on the

buccal side of the protoconid and talonid that may be due to a specific hard foot item in the diet or to chipping and subsequent wear, possibly caused by some pathology to the occluding upper tooth.

Measurements. Lm2 14.8; Wm2 8.1; Ltm2 10.5.

KNM-FT 13772

Another specimen that is identical in morphology to the m2s KNM-FT 3562e and KNM-FT 13771. Interestingly, it has a distobuccal wear pattern that is identical to that of KNM- FT 13771, which may suggest that the wear is due to some specific food item and that these two teeth belonged to the same individual.

Measurements. Lm2 14.6; Wm2 7.8; Ltm2 10.4.

KNM-FT 14135

Another m3 that is practically identical in morphology to the m3s KNM-FT 3562e and KNM-FT 13770. Like the latter it has a longer paraconid than protoconid.

Measurements. Lm3 19.4; Wm3 9.0; Ltm3 16.4.

KNM-FT 15092 ( Fig. 5 A-C)

This M1 has a protocone shelf that is set at about a 45° angle to the buccal edge of the tooth. The protocone is large but not tall, being significantly lower than the other cusps of the tooth, including the metastyle. The protocone is bordered lingually by a stout basal bulge. The paracone is smaller and lower than the metacone and is round in occlusal view. The metacone is the largest cusp and set closely distal to the paracone. The metacrista is notched and curved. The distal end of the tooth is broken.

Measurements. LM1 (buccal) 16.9; WM1 (at paracone) 8.9.

KNM-FT 14217

The dP2 of Dissopsalis is not previously known, so the identification of this specimen as that tooth position is tentative, as is its referral to Dissopsalis . The tooth is morphologically very similar to the P2 KNM-FT 3375c described above but is slenderer and has an overall less developed cingulum. It is the right size to match the alveoli for dP 2 in KNM-FT 3357.

Measurements. LdP2 11.6; WdP2 5.4.

DISCUSSION

The type species of Dissopsalis , D. carnifex, is a fairly well known hyaenodont from the Siwaliks of Pakistan and India ( Pilgrim 1910, 1913, 1914; Colbert 1933; Barry 1988). African material of Dissopsalis has been referred to the species D. pyroclasticus , first described on the basis of a mandibular ramus from Maboko, Kenya ( Savage 1965; Morales & Pickford 2017) and later listed in faunal lists from a number of sites in Kenya and Uganda (see references in Barry [1988]), but these materials have never been studied in detail (but see Borths & Stevens [2017]) and doubts have been raised concerning their taxonomic attribution ( Barry 1988). The most complete, as well as the youngest, material assigned to the species is that from Fort Ternan (e.g., Shipman et al. [1981]). Referral of the Fort Ternan material described above to Dissopsalis seems unproblematic in view of the many similarities between the type specimen and KNM-FT 3562, as well as similarities of the upper dentition material to that of D. carnifex ( Colbert 1933). However, there are also some differences. The type specimen shows m3 to be shorter than m2, which the reverse of the condition in KNM-FT 3562. In KNM-FT 3562 (as well as KNM-FT 13370 and KNM-FT 14135), the m3 talonid is, judging from figures in Savage (1965) somewhat longer than that of the type specimen. Finally, the type specimen of D. pyroclasticus is smaller overall than the Fort Ternan specimens. These differences suggest, but do not clearly demonstrate, a difference at the species level between D. pyroclasticus from Maboko and the Fort Ternan material. Therefore, I here leave this material in open nomenclature.

Figures

FIG. 5. — Hyaenodonta from Fort Ternan: A-I, Dissopsalis cf. pyroclasticus; A-C, KNM-FT 15092, left M1 in buccal (A), lingual (B), occlusal (C) views; D, E, KNM-FT 13771,right m2 in buccal (D), lingual (E), and occlusal (F) views; G-I, KNM-FT 13770, right m3 in buccal (G), lingual (H), and occlusal (I) views; J, Hyainailourinae gen.et sp. indet., KNM-FT 3359,left upper canine in medial view. Scale bars: A-I, 20 mm; J, 100 mm.