Leakitherium hiwegi SAVAGE , 1965

Morales, Jorge & Pickford, Martin, 2017, New Hyaenodonts (Ferae, Mammalia) From The Early Miocene Of Napak (Uganda), Koru (Kenya) And Grillental (Namibia), Fossil Imprint 73 (3 - 4), pp. 332-359 : 336

Leakitherium hiwegi SAVAGE, 1965

Text-fig. 1

H o l o t y p e. Left maxillary fragment with M1 – M2

(NHMUK M 19083) ( Text-fig. 1 ).

T y p e l o c a l i t y. Rusinga, Kenya.

A g e. Early Miocene.

D i a g n o s i s. See Lewis and Morlo (2010).

D i s c u s s i o n. As for Dissopsalis pyroclasticus ,

Borths et al. (2016: supplementary tab. 2) cited the existence of additional unpublished teeth, comprising both

M1/M2 occlusal shape: quadrangular (0), isosceles

1

triangle (1), rectangle (2), linear (3)

2 M1/M2 protocone size: large (0), medium (1), reduced (2) M1/M2 protocone isthmus: wide (0), narrow (1),

3

reduced (2)

M2 L/W ratio: <0.85 (0), between 0.86 – 1.15 (1),

4

between 1.16 – 1.35 (2),>1.35 (3)

M1 L/W ratio: <0.85 (0), between 0.86 – 1.15 (1),

5

between 1.16 – 1.35 (2),>1.35 (3)

M1/M2 protocone position: in front of parastyle/

6

paracone (0), anterior position to parastyle/paracone (1)

M2 metacone/paracone: partially separated (0), fused with

7 vertical separation groove (1), fused without separation groove (2)

M1 metacone/paracone: partially separated (0), fused with

8 vertical separation groove (1), fused without separation groove (2)

9 M2 metastyle: small (0), short (1), long (2), very long (3) M1/M2 paracone/metacone morphology: coniform (0),

10

sectorial (1)

11 M1/M2 parastyle: present (0), reduced or absent (1) M1/M2 buccal cingulum: present (0), reduced or

12

absent (1)

13 M1/M2 buccal stylar area: present (0), reduced or absent (1) M1/M2 paracone/metacone relative size: paracone

14 larger than metacone (0), paracone somewhat larger than metacone (1), metacone larger and taller than paracone (2)

15 M1/M2 trigon valley: wide (0), narrow (1)

16 P4 L/W ratio: <1.1 (0),>1.1 (1)

17 P3 W/L ratio:>0.55 (0), <0.55 (1)

18 m 3 metaconid: present (0), absent (1)

19 m 3 W/L ratio:>0.60 (0), <0.60 (1)

20 m 2 metaconid: present or residual (0), absent (1)

m2 talonid morphology: basined with hypoconid,

21 hypoconulid and entoconid (0), narrow with hypoconid in central position (1)

22 m 2 talonid size: well-developed (0), reduced (1)

p4 talonid morphology: basined (0), narrow, hypoconid in

23

central position (1)

24 p3 W/L ratio: <0.65 (0),>0.65 (1)

25 p4 W/L ratio: <0.57 (0),>0.57 (1)

p2/p3 orientation with respect to axis of mandible:

26

linear (0), transversal (1)

upper and lower dentitions. The lingual wall of the M 2 in the holotype maxilla of the species is heavily worn, which partly obscures proper assessement of its characters, just as in a second individual, attributed to this species but which shows important differences from the holotype, rendering its identification doubtful. Therefore, it is not strange to find that its systematic position is erratic. It is possibly related to Isohyaenodon andrewsi (van Valen 1967, Dashzeveg 1985) or to Hyainailouros napakensis ( Morales et al. 1998a) or to the more hypercarnivorous species of the subfamily Hyainailourinae ( Solé et al. 2014, Borths et al. 2016).

Another possible correlation for Leakitherium hiwegi , not only morphological, but also dimensional, could apply to Dissopsalis pyroclasticus , which has a robust lower dentition. The two forms also share the presence of wrinkled enamel and in addition have posterior molars (M2 – M1 and m3 – m2) which are similar in length. This is highly divergent from the interdental proportions in Dissopsalis carnifex , in which the M2 and the m3 are noticeably larger than the M1 and m2. In fact, Morlo et al. (2007) indirectly suggested the possible generic separation of these taxa in their interpretation of Buhakia from Wadi Moghara, a new genus proposed by the authors, which they considered to be closer to D. carnifex than to D. pyroclasticus , but the separation was not formally proposed ( Lewis and Morlo 2010). In their supplementary table 2, Borths et al. (2016) pointed out that the protocones in the holotype of Leakitherium hiwegi “suggest larger talonid basins are expected on the lower dentition….”. This is possible as indicated above. Even though the holotype of Leakitherium hiwegi has a heavily worn lingual wall of the M2, the impression is that the protocone would have been at least as well-developed as in the M1. Another important feature is the strong groove between the paracone and metacone visible in the buccal side of the two cusps. The metacone is much better developed than the paracone in both molars, a condition also found in other taxa such as Dissopsalis carnifex . An analogous morphology, even though the teeth are more robust, occurs in the maxilla from Karungu described by Savage (1965) as Metapterodon kaiseri , which we here interpret as an indeterminate species of Buhakia , and therefore relatively close to Dissopsalis .

Figures

Text-fig. 1. Leakitherium hiwegi SAVAGE, 1965 from Rusinga, Kenya. NHMUK M 19083 (holotype), left maxilla with M2 – M1. a: occlusal view, b: lingual view, c: buccal view (stereo pairs).