Thryptodon brailloni, Hooker & Russell, 2012
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2011.00787.x |
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DOI |
https://doi.org/10.5281/zenodo.10544464 |
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persistent identifier |
https://treatment.plazi.org/id/03DE8792-FFBB-6566-FF31-FB71FC0BFC07 |
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treatment provided by |
Marcus |
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scientific name |
Thryptodon brailloni |
| status |
gen. et sp. nov. |
THRYPTODON BRAILLONI SP. NOV. ( FIG. 20 View Figure 20 )
vp 1964 Hyopsodontidé?; Russell, pp. 247–248, pl. 16,
fig. 6b. vp 1967 Hyopsodontidé, genre indéterminé; Russell,
Louis & Poirier, p. 853, pl. 21, fig. 4 (right).
Etymology: After the late Dr Jean Braillon, for finding key specimens of the species.
Holotype: LM 2, MNHN.F.CR-1268, Cernay.
Paratypes: RM 2 , MNHN.F.CR-311-L; RM 1 , MNHN. F.CR-55-Bn; LM 2, MNHN.F.CR-317-L; two RM 2 s, MNHN.F.CR-90-Bn, CR-63-V; all Cernay.
Right M 1, MNHN.F.I-681; RM 2, MNHN.F.I-685; bed 5, Berru.
Tentatively referred specimens: LP 3, MNHN.F.CR-170- Ph; Cernay. RP 3, MNHN.F.I-691; bed 5, Berru.
Cast in MNHN.F: RP 3, CR-64-Ro; Cernay.
Age and distribution: Sables de Châlons-sur-Vesle supérieurs, late Thanetian, Late Paleocene, Cernay and Berru (bed 5), France.
Diagnosis: As for genus, monotypic.
Description
M 1–2: What are interpreted here as M 1 and M 2 are similar in morphology ( Fig. 20A–C View Figure 20 ). Both tooth types are wider than long ( Table 7) and basically tribosphenic, with a moderate-sized hypocone that is smaller than the protocone. There is thus a welldeveloped trigon and no sign of any crest joining it to the hypocone. Main crests, except preparacrista, are present but weak and there is overall moderate bunodonty. The preparaconule crista almost reaches the lingual end of the paracingulum, which is confluent with the precingulum, ectocingulum, metacingulum, and postcingulum, which embrace the tooth uninterrupted on three sides, but not lingually. The paraconule is present but a little variable in size and position. The metaconule is also consistently present. Cristae are essentially absent from the metaconule, but there is a very thin low postparaconule crista on all three teeth. Also consistent are the relative sizes of the paracone and metacone, the latter being smaller than the former, although the degree of difference varies. Representation of a parastyle is negligible. The smallest bears an entostyle ( Fig. 20A View Figure 20 1 View Figure 1 ).
The smallest tooth ( Fig. 20A View Figure 20 ) has less difference in size between the paracone and metacone and these cusps are also better separated than on the other two teeth. There is a slight mesial parastylar bulge in the outline, the precingulum ends lingually in a small protostyle, and there is a small cusp on the postcingulum just buccal of the hypocone, all features lacking in the two larger teeth. The two larger teeth ( Fig. 20B, C View Figure 20 ) are slightly shorter and broader and their buccal and lingual cusps are more occlusally convergent. The smallest tooth is interpreted as M 1, the larger two as M 2.
M 1–2: These four teeth are moderately bunodont like the uppers and display slight exodaenodonty as separate lobate bases to the trigonid and talonid ( Fig. 20E, F View Figure 20 ). The protoconid and metaconid are larger than the hypoconid and entoconid, but the difference varies in degree. The trigonid is longer and wider than the talonid, but this difference also varies in degree ( Table 7). There is a distinct, small hypoconulid, but the paraconid is very small to absent. The protocristid is moderately notched. The protoconid bulges lingually, almost filling the trigonid basin. There is a blunt premetacristid that does not join the paraconid or its position at the end of the paracristid. The cristid obliqua is fairly strong, dipping steeply mesially at
OR, observed range.
first then, after a notch, rises some way up the back of the trigonid; the attachment position is slightly buccal of the midline. There is a pre-entocristid that dips down to a shallow talonid notch. A faint entoconulid is sometimes present. The precingulid is sharp but short.
Three of the four teeth have a talonid basin about one third of the length of the trigonid and the hypoconid and entoconid are about half the height of the protoconid and metaconid ( Fig. 20F View Figure 20 ). The level of the talonid notch is about half the height of the metaconid in the least worn of these three. The fourth tooth has moderate tip wear, but all the main cusps are distinctly separated ( Fig. 20E View Figure 20 ). The talonid is nearly half as long as the trigonid and nearly as wide. There is less difference in height between the protoconid and metaconid on the one hand and the hypoconid and entoconid on the other. There is a tiny paraconid, lacking from the only other tooth with sufficiently light wear to have left the area unscathed. The talonid notch is also at a lower level. This tooth occludes well with the M 1 and is interpreted as M 1. The other three, of which the least worn (MNHN.F.CR-90-Bn: Fig. 20F View Figure 20 ) occludes well with the M 2 s (because of the shorter proportions and greater buccal and lingual cusp convergence, which reduces the width of the trigon), are interpreted as M 2.
P 3?: Three simple premolars may represent this locus. MNHN.F.I-691 is from the right side and is 3.43 mm long by 1.85 mm wide ( Fig. 20D View Figure 20 ). Another right (CR- 64-Ro) is 3.32 mm long by 2.04 mm wide. The protoconid is dominant, with a fairly low, lingually positioned paraconid and a small, scarcely basined talonid with a single cusp that is not transversely elongate. Weak crests descend the protoconid mesially and distally, the former steeper than the latter. Two exodaenodont lobes protrude over the anterior and posterior roots, but to a lesser extent than in P 3 of L. marci . The broad pattern is similar to P 3 s of the latter species, but the paraconid is much lower, like Prolouisina atavella , and overall crown height is less. The left tooth (MNHN.F.CR-170-Ph) is more worn than MNHN.F.I-691, with slightly greater relative width (3.44 mm long by 2.05 mm wide) and a distally procumbent talonid ( Fig. 20G View Figure 20 ), but is otherwise very similar. The large size and weak exodaenodonty, but otherwise similar structure to L. marci and Pr. atavella suggests that these teeth may belong to Th. brailloni .
Discussion: This monotypic genus is clearly distinct from Prolouisina , Louisina , and Teilhardimys , but more closely related to these genera than to other louisinids, sharing with them exodaenodonty and a lower molar precingulid that is short and rises mesially.
| MNHN |
Museum National d'Histoire Naturelle |
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