Oxyaenoides aumelasiensis, Solé & Marandat & Lihoreau, 2020

Solé, Floréal, Marandat, Bernard & Lihoreau, Fabrice, 2020, The hyaenodonts (Mammalia) from the French locality of Aumelas (Hérault), with possible new representatives from the late Ypresian, Geodiversitas 42 (13), pp. 185-214 : 190-192

Oxyaenoides aumelasiensis n. sp. (Fig. 2)

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HOLOTYPE. — UM-AUM693 , left mandible bearing m3, the anterior root and talonid of the m1, the posterior alveolus of the p4, and the alveoli of m2.

ETYMOLOGY. — Latin, from Aumelas (type locality).

REFERRED SPECIMENS. — UM-AUM686, right M2; UM-AUM692, combination of a left maxillary fragment bearing the P2-M1, a right maxillary fragment bearing the P3-P4, the protocone of the M1 and the alveoli of the P2; UM-AUM695, labial part of a M1. HORIZON AND AGE. — Lacustrine limestone of Montpellier, proposed as Lutetian in age in previous study but here considered possibly late Ypresian/early Lutetian in age

TYPE LOCALITY. — Aumelas, Hérault, France.

DIAGNOSIS. — The species is 15% smaller than O. bicuspidens and 25% smaller than O. bicuspidens and O. schlosseri. It differs from O. lindgreni and O. bicuspidens by a more buccally aligned metastyle on molars. It differs from O. bicuspidens and O. schlosseri by a less retroflexed protoconid.

MEASUREMENTS. — Table 3.

DESCRIPTION

The P2 has a very small lingual fold that corresponds to an incipient parastyle. The metastyle is short and low ( Fig. 2D, E ). There is a small diastema between the P2 and P3 ( Fig. 2F, G ). The P3 and P4 are mesiodistally elongated. The P3 is characterized by the presence of a distinct parastyle and a strong metastyle. There is a large lingual bulge but no protocone. The P4 also displays a very large parastyle and metastyle; the latter is very tall. The protocone projects lingually and is mesiodistally narrow ( Fig. 2 D-G).

The two known molars have a very similar morphology ( Fig. 2D, E, H, I ). On M1, the parastyle is present and bulbous but is mesiodistally short and narrow. The metastyle is mesiodistally elongated. The paracone and metacone are partially fused; only the apexes are fully separated. The protocone is low. The protofossa is very mesiodistally short and narrow. The paraconule is present. The metaconule is absent. The M1 is morphologically identical to the M2 except that the parastyle is wider and the metastyle is less distally located.

The mandible is narrow. The masseteric fossa is deep. As in Matthodon , a deep fossa for insertion of the temporal muscle is present along the anterior margin of the coronoid crest. The latter is distally inclined and the angle between the coronoid crest and the body of the dentary is close to 120°.

UM/AUM693 is a fragment of a left mandible that bears the talonid of m1 and a complete m3 ( Fig. 2 A-C). The talonid of the m1 bears three distinct cusps (entoconid, hypoconid, and hypoconulid). The entoconid is lower than the hypoconulid, which is distally located, and lower than the hypoconid. Contrary to the m1, the m3 is complete. The paraconid is tall, long and well mesially located. There is no metaconid. The m3 is thus characterized by a cutting trigonid. The talonid is very mesiodistally short, low, and narrow with only one cusp (hypoconulid?) present. The precingulid is developed.

DISCUSSION

The fossils from Aumelas are characterized by a very cutting morphology (e.g., long metastyle on P4 and molars, absence of metaconid, long paracristid on m3). Only one hyaenodont genus known from the Ypresian and Lutetian of Europe has molars that are characterized by the absence of a metaconid, a hypercarnivorous feature: Oxyaenoides (MP10-?MP13) ( Matthes 1967; Lange-Badré & Haubold 1990; Solé et al. 2014a). The teeth found at Aumelas share with Oxyaenoides mesiodistally short and narrow talonids bearing crestiform entoconids on molars. This genus is known both in northwestern ( Matthes 1967; Lange-Badré & Haubold 1990; Solé et al. 2014a, 2015a) and southwestern Europe ( Crochet et al. 1976).

Three species of Oxyaenoides are presently known: Oxyaenoides lindgreni from MP10 ( Rich 1971; Solé et al. 2014a), Oxyaenoides bicuspidens from MP11 ( Matthes 1967; Crochet et al. 1976; Lange-Badré & Haubold 1990) and Oxyaenoides schlosseri from?MP13 ( Rütimeyer 1891; Lange-Badré 1972; Solé et al. 2015a). The syntypes of O. schlosseri are from Egerkingen γ (Lange-Badré 1972), but the MP reference-level of this site (possibly MP13) is uncertain ( BiochroM’97 1997), as is Aigues-Vives 2 where a mandible of O. schlosseri was discovered ( Solé et al. 2015a).

The most striking feature of the fossils from Aumelas is their small size compared to other Oxyaenoides material. The teeth are 15% smaller than those of O. lindgreni and 25% smaller than those of O. bicuspidens and O. schlosseri. The size of the new taxon is actually almost equivalent to that of Preregidens langebadrae (Saint-Papoul; c. MP8+9).

Oxyaenoides aumelasiensis n. sp. differs from those of O. lindgreni and O. bicuspidens by a more buccally aligned metastyle on upper molars. It also differs from O. bicuspidens and O. schlosseri by a mesially oriented protoconid – this feature accommodates an elongate preprotocristid, a structure found on cutting molars. Oxyaenoides aumelasiensis n. sp. appears more primitive than northwestern species by having a buccally aligned metastyle on upper molars and the less retroflexed protoconid on molars.

To conclude, the fossils of Oxyaenoides aumelasiensis n. sp. share with the other Oxyaenoides species several features including: a reduced metaconid and reduced talonid morphology. However, based on the small size and distinctive features, we distinguish O. aumelasiensis n. sp. from previously described species of Oxyaenoides .

The fossils from Aumelas are important because they are the first to provide so much information on the morphology of the upper premolars of the genus Oxyaenoides . The fossils from Aumelas represent the smallest hypercarnivorous hyaenodont ever discovered in the Ypresian and Lutetian.

Figures

FIG. 2. — Oxyaenoides aumelasiensis n. sp. from Aumelas (MP10-MP11?): A-C, UM-AUM693 (Holotype), left mandible bearing m3, the anterior root and talonid of the m1, and the posterior alveolus of the p4, and the alveoli of m2; A, occlusal view; B, lingual view; C, labial view; D-G, UM-AUM692, combination of a left maxillary fragment bearing the P2-M1, a right maxillary fragment bearing the P3-P4, the protocone of the M1 and the alveoli of the P2; D, occlusal view of left maxillary; E, labial view of the left maxillary; F, occlusal view of the right maxillary; G, labial view of the right maxillary (reversed view);H-I, UM-AUM686,right M2; H, occlusal view; I, labial view. Scale bars: A-G, 1 cm; H, I, 50 mm.