Boritia duffaudi, Solé & Falconnet & Yves, 2014
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publication ID |
https://doi.org/ 10.1111/zoj.12155 |
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persistent identifier |
https://treatment.plazi.org/id/03B0878A-D16E-A638-FC63-F905C284FAA6 |
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treatment provided by |
Marcus |
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scientific name |
Boritia duffaudi |
| status |
sp. nov. |
BORITIA DUFFAUDI SP. NOV. ( FIG. 7 View Figure 7 )
Diagnosis
The proviverrine genus Boritia is characterized by the presence of mental foramina located below the P 1 and P 3, a reduced P 1, premolars with a wide talonid and a paraconid developed on P 4, a poorly sectorial trigonid (paraconid poorly projected mesially, metaconid aligned
894 F. SOLÉ ET AL .
transversally with the protoconid), and a short and narrow talonid on the molars. Boritia differs from the contemporaneous Morlodon by having a less reduced P 1, more separated premolars, less robust premolars, less oblique cristid obliqua, and longer talonid on the molars.
Etymology
Dedicated to Dr Sylvain Duffaud, who discovered the holotype.
Holotype
MHNT.PAL.2010.19.1, right dentary bearing P 3, P 4, M 1, M 2, and M 3 and alveoli of C 1 −P 2.
Type locality
MP8 + 9, La Borie ( France).
Measurements
See Table 5.
*Estimated on the basis of the roots.
†Weight estimated after Morlo (1999)
N, number of specimens; OR, observed range.
Description
Two large foramina are present below the distal roots of P 1 and P 3, respectively. Very small foramina are also present below the mesial root of P 2, and below the distal root of P 2. The ventral margin of the dentary is slightly slanted posteriorly, which results in a posterior deepening of the mandible along the tooth row. The symphysis is shallow and extends below the distal root of P 2. The beginning of the coronoid crest is vertical. The dorsal part of the coronoid crest is more oblique. The condyle is robust, but has a weak transverse extension. Although the P 1, P 2, and P 3 are separated by diastemata, there are none between the P 3 and the P 4. The premolars increase in size anteroposteriorly. According to the alveoli, the P 1 and the P 2 are tworooted, but the first differs in the partial fusion of the roots. There are also two roots for the P 3 and the P 4. The P 2 seems longer than the P 3, but its length is probably overestimated because of the reconstruction. The P 3 is lower crowned than the P 4. It is elongated mesiodistally and is slightly asymmetrical in lateral view. A slightly developed and high paraconid is present, although weakly individualized. The talonid is elongated distally, and larger than the protoconid. The little cusp that is present lingually may represent the entoconid. The P 4 differs from the P 3 in having a less asymmetrical morphology, a taller talonid, and a paraconid that is lower but more elongated mesially and individualized. The lingual cusp (entoconid) is present and is more developed than on P 3. The talonid is wider than the protoconid. The talonid crest is labially located as on P 3. The two cusps that are on the labial crest of the talonid are either the hypoconid and the protostylid or the hypoconid and the hypoconulid.
The M 2 is the largest molar, M 1 the smallest one. The M 3 represents the lower carnassial tooth (= most sectorial tooth) as usually observed in specialized Hyaenodontida. In all molars, the protoconid is distinctly sharper and taller than the other cusps of the trigonid. The paraconid is a bit smaller than the metaconid. It is slightly projected mesially. Moreover, the paracristid is elongated. The metaconid is located mesially (aligned with the protoconid). From M 1 to M 3 the metaconid becomes more reduced, is shifted more distally, and the paracristid becomes narrower transversally. The distal segment of the paracristid is aligned mesiodistally, whereas the protocristid crest is transverse. The base of the paraconid expands slightly lingually, but is less developed than the base of the metaconid. Although the contact between the metaconid and paraconid is large at the base, their apices are divergent. The metaconid is also slightly fused to the protoconid. Its apex is straight instead of being projected lingually as in Eoproviverra . In all molars, the talonid is shorter and only slightly narrower than the trigonid. The postfossid is closed lingually by the entocristid. On M 1 and M 2, the hypoconid, hypoconulid, and entoconid are clearly separated by notches, even if their apices are poorly developed. The hypoconid is slightly taller than the entoconid and hypoconulid. The entoconid is reduced and fuses partially with the hypoconulid. The entocristid forms a sectorial crest. The cristid obliqua is slightly oblique (distally shifted labially). The hypoconulid is narrow and projected distally. The M 3 differs in having a narrower, shorter talonid and postfossid, and a lower talonid. The apices of the hypoconulid and hypoconid are worn, but they were probably poorly developed. The entoconid has no real apex. The entocristid and cristid obliqua are nearly aligned mesiodistally and are only slightly oblique, as on M 1 and M 2. Shallow notches separate the three cusps. The molars exhibit only the precingulids, which are short and vertical. The hypoflexid is deep, but not very pronounced on M 1 and M 2.
Discussion
MHNT.PAL.2010.19.1 is one of the best-preserved hyaenodontidan mandibles from the Early Eocene of Europe. The coronoid crest of the earliest members of this group is poorly known. We therefore compared this structure with that of the better-known hyaenodontidan from the Geiseltal Formation ( Lange-Badré & Haubold, 1990). The coronoid crest is more vertical in Boritia than in the genera Oxyaenoides and Matthodon . The condyle is robust and bulbous, but with a weak transverse expansion as in the oldest hyaenodontidans. Jaw movement in Boritia thus appears to have been less restricted transversally than in the Middle Eocene Oxyaenoides and Matthodon .
The presence of an entoconid on the molars, a tworooted P 1, and an entoconid on P 4 allows us to refer MHNT.PAL.2010.19.1 to the Proviverrinae as recently redefined by Solé (2013).
The earliest proviverrines and the sister taxa of all other proviverrines are from southern France: Eoproviverra eisenmanni (Rians, MP7) and Parvagula palulae (Palette, MP7). Boritia shares several plesiomorphic features with Pa. palulae and Eo. eisenmanni , such as an oblique talonid (which is distally shifted labially) and diastemata between P 1, P 2, and P 3. Pa. palulae and Eo. eisenmanni retained plesiomorphic proviverrine characters such as small size, and an M 1 and M 2 with narrower talonids bearing well-developed entoconids. MHNT.PAL.2010.19.1 has a less specialized trigonid than Eo. eisenmanni : the paraconid is less projected mesially and the metaconid is more mesially located. However, the smaller lingual projection of the apex of the metaconid of Boritia compared with Eo. eisenmanni is an apomorphic feature. In contrast to the trigonid, the talonids of the molars on MHNT.PAL.2010.19.1 differ from those of Eo. eisenmanni in their more derived morphology: talonid shorter and wider, and entoconid less bulbous and individualized (more crestiform and less pronounced apex). MHNT.PAL.2010.19.1 is more plesiomorphic than Pa. palulae in the narrowing of the anterior part of the mandible.
The resemblance of MHNT.PAL.2010.19.1 to European hypercarnivorous proviverrine Oxyaenoides also necessitates a few comments. The premolars of Boritia are similar in the following traits: (1) mesiodistally elongated occlusal outline; (2) P 3 and P 4 that are symmetrical in lateral view; (3) P 3 and P 4 with a small paraconid; (4) P 3 distinctly lower than the P 4; (5) P 4 with a high, distally elongated talonid, a labially located hypoconid, and an entoconid. This morphology corresponds to a mosaic of characters that are either plesiomorphic (4, 5) or apomorphic (1, 2, 3) amongst the Proviverrinae . The P 3 and P 4 of MHNT.PAL.2010.19.1 nevertheless differ from those of Oxyaenoides in the stronger development of the paraconid and talonid (which underlines the proviverrine trend towards a more robust dentition), a more developed paraconid, and a wider talonid.
The lower molars of Boritia also differ from Oxyaenoides in retaining the plesiomorphic configuration of the postfossid, which is closed lingually by the entocristid. In Oxyaenoides , the postfossid is fully opened lingually, which is a common characteristic of hypercarnivorous hyaenodontidans. MHNT.PAL.2010.19.1 also differs from Oxyaenoides in displaying a larger metaconid and a shorter paracristid (plesiomorphic features). Thus, the less sectorial, plesiomorphic lower molars and the robust, derived premolars are distinctive features of MHNT.PAL.2010.19.1 with respect to Oxyaenoides .
The morphology of MHNT.PAL.2010.19.1 is similar to that of the recently described Morlodon vellerei (Avenay, Condé-en-Brie, MP8 + 9; Solé, 2013). In particular, they share apomorphic features related to the acquisition of a robust dentition such as the reduced P 1, the wide premolar talonid, the developed paraconid on P 3 and P 4, and the reduction of the entoconid. By contrast, they also share plesiomorphic features that allow us to distinguish them from the older Eo. eisenmanni and Pa. palulae . The peculiar shape of the dentary is also unique to MHNT.PAL.2010.19.1 and Mo. vellerei in becoming anteriorly shallow, in contrast to what can be seen in the two species of Oxyaenoides .
MHNT.PAL.2010.19.1 differs from Mo. vellerei in retaining numerous plesiomorphic features: clearly tworooted P 1, narrower and less tightly packed premolars, less developed paraconid on P 4, narrower postfossid, and longer and more oblique talonid. It thus appears that MHNT.PAL.2010.19.1 and Mo. vellerei represent two distinct species. We propose to refer
MHNT.PAL.2010.19.1 to Boritia duffaudi sp. nov.
The fossil locality of ‘La Borie’ has revealed a unique fauna from the Early Eocene of southern France ( Laurent et al., 2010). Based on the presence of the mammals Lophiaspis , Dissacus , Plesiesthonyx , and of the groundbird Diatryma , an age close to the MP 8 + 9 reference level has been proposed. This age has been confirmed by the study of the Pachynolophus sp. from La Borie ( Danilo et al., 2013). It is important to note that this is the first mammal locality known from southern France for this period. Indeed, the other French localities are located in the Paris Basin (e.g. Mutigny, Avenay).
| ET |
East Texas State University |
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