Minimovellentodon russelli, Solé & Falconnet & Yves, 2014

Solé, Floréal, Falconnet, Jocelyn & Yves, Laurent, 2014, New proviverrines (Hyaenodontida) from the early Eocene of Europe; phylogeny and ecological evolution of the Proviverrinae, Zoological Journal of the Linnean Society 171 (4), pp. 878-917 : 896-899

MINIMOVELLENTODON RUSSELLI SP. NOV. ( FIG. 8 )

Diagnosis

Minimovellentodon differs from Eoproviverra and Parvagula in its larger size, deeper mandible, a metaconid that is lower than the paraconid (apomorphic feature), and in some primitive features such as a paraconid that is less projected mesially or the transverse alignment of the metaconid with the protoconid. It differs from Morlodon and Boritia in its smaller size, longer and narrower talonid, and larger metaconid on molars.

Etymology

Dedicated to Dr Donald Russell who has greatly contributed to our knowledge of Palaeocene and Eocene mammals.

Holotype

MHNL 20269998 , right mandible bearing P 3 −M 3, and roots of P 2.

Type locality

MP8 + 9, Mutigny ( France).

Measurements

See Table 6.

Description

Two mental foramina are present: between P 1 and P 2, and below P 3. The P 1, P 2, and P 3 are separated by diastemata. The anterior margin of the coronoid crest rises at an angle close to 70°. The mandible is deep under the molars but narrows anteriorly.

The preserved teeth are all worn. The premolars are all transversally compressed (mesiodistally elongated).

The P 2 is two-rooted and shorter than the P 3. There is a small, low, and short paraconid on P 3. The P 4 is *Estimated on the basis of the roots.

†Weight estimated after Morlo (1999).

N, number of specimens; OR, observed range.

the longest premolar. It bears a paraconid, which is more developed than in the P 3 but nevertheless remains low. The tooth is almost as long as the M 1.

The M 1 is noticeably shorter than the M 2 and M 3. Their morphology is similar. The trigonid is compressed mesiodistally. The paracristid is short, and the paraconid is shifted mesially. The metaconid is aligned transversally with the protoconid. There is a wide contact between the paraconid and the metaconid. The protoconid is high and pointed. The talonid is oblique (distally shifted labially) and is elongated mesiodistally so that it appears narrower than the trigonid. The postfossid is narrow. The developed entoconid area indicates that this cusp was not crestiform as observed in sinopines, but was more cuspidate. The entocristid and cristid obliqua are oblique as the postfossid. The hypoconulid is projected distally. Only a short precingulid can be observed. The M 3 differs in its a narrower talonid. The talonid is more elongated mesiodistally than on M 1 and M 2. Its paracristid is also longer and the paraconid is more mesially located.

Discussion

The mandible MHNL 20269998 displays features that are reminiscent of the oldest hyaenodontidans, such as the presence of three molars – the M 3 being the largest, the second foramen located below P 3, the deep mandible, the large paraconid on P 4 and especially on the molars, and the presence of an important wear facet 2 on the molars – this latter feature indicates that the shearing function of the dentition was prominent. These features clearly allow referral of MHNL 20269998 to hyaenodontidans.

The position of the mental foramina, the close P 3 and P 4, the less asymmetrical premolars, the more developed paraconid on P 4, and the shorter talonid on the molars of Minimovellentodon show that it differs significantly from the Palaeocene Tinerhodon , but agrees well with Eoproviverra and Parvagula .

Minimovellentodon russelli has a plesiomorphic trigonid compared to Eoproviverra eisenmanni : the paraconid is not projected mesially and the metaconid is not distally located as in the latter species. The morphology of the trigonid of Minimovellentodon is close to that of Tinerhodon ; it is clearly less sectorial than that of Eo. eisenmanni . The talonid of MHNL 20269998 is worn, but was apparently narrow and shorter than the trigonid. This plesiomorphic morphology was also retained by Eoproviverra . By contrast, Mi. russelli differs from Parvagula and Prototomus minimus (Dormaal) in its deeper mandible. Finally, the strong development of the paraconid on P 3 and P 4 also distinguishes Mi. russelli from the Dormaal Prototomus spp. , Eoproviverra , and Parvagula .

The distinctive morphology of Mi. russelli , which is a combination of plesiomorphic and apomorphic features when compared with Eoproviverra and Parvagula , justifies the erection of a new genus and species for the taxon of Mutigny.

In conclusion, it is worth remembering that Minimovellentodon , Eoproviverra , and Parvagula have several apomorphic characters in common. However, the presence of a mesially located metaconid and weakly projected paraconid, as in the plesiomorphic Tinerhodon , indicates that Minimovellentodon is not directly related to Eoproviverra . Besides, in spite of its greater age, Eo. eisenmanni has a more sectorial dentition than Minimovellentodon .

By contrast, the increase in the depth of the mandible of MHNL 20269998 suggests that Minimovellentodon is more closely related to Morlodon . Both these species have a deep mandible [(mandibular depth/M 1 length)> 2; see Table 7]. Nevertheless, Minimovellentodon differs from Morlodon in having narrower premolars, a distinctly less mesially located paraconid (which results in a closed prefossid) on the molars, a narrower talonid and a more developed entoconid on the molars, and a longer talonid, notably on M 3. All these features are plesiomorphic amongst Hyaenodontida and support the generic distinction.

The proviverrine Minimovellentodon from Mutigny represents the oldest record of this subfamily in the Northern Province [sensu Marandat, (1997)]. It implies that the Proviverrinae were present in the Paris Basin since biozone PE IV of Hooker (1998) ( Fig. 11 ; Table 8).

ELMA, European Land Mammal Ages; MP, mammal palaeogene; PE, Palaeocene-Eocene.

Figures

Figure 8. Minimovellentodon russelli gen. et sp. nov. A−C, MHNL 20269998 (holotype), right dentary with P3−M3 roots of P2. A, occlusal view; B, labial view; C, lingual view. Scale bar = 10 mm.

Figure 11. Comparison of the European biogeography of placental carnivorous mammals during the earliest Eocene: A, between the MP7 and MP8 + 9 levels and B, during the MP8 + 9 level. A, the Northern Province is characterized by the presence of the hyaenodontidan Sinopinae and Oxyaenodonta, whereas the Mesogean Province is characterized by the presence of the hyaenodontidan Sinopinae and Proviverrinae. Proviverrinae occurred in Rians and Palette (France) and Silveirinha (Portugal). Sinopinae are identified at Dormaal (Belgium), Le Quesnoy, Pourcy, Soissons (France), and Abbey Wood (England). Oxyaenodonta are identified in Dormaal, Houdancourt (Belgium), Meudon, Sinceny, Muirancourt, Le Quesnoy (France), and Abbey Wood (England) (Hooker, 2010; Solé et al., 2011). Above the line: Northern Province; below the line: Mesogean Province. B, the provinces have been homogenized because of disappearances (e.g. Sinopinae and Oxyaenodonta) and faunal dispersals (e.g. Proviverrinae; see Table 8). The arrow symbolizes the dispersal of the Proviverrinae from the Mesogean to the Northern Province. Redrawn from Marandat et al. (2012: fig. 1).