Prolouisina atavella, (RUSSELL, 1964), 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.5479828 |
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persistent identifier |
https://treatment.plazi.org/id/03DE8792-FFB9-6560-FC9C-F944FA09FBCB |
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treatment provided by |
Marcus |
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scientific name |
Prolouisina atavella |
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PROLOUISINA ATAVELLA ( RUSSELL, 1964)
COMB. NOV. ( FIGS 21 View Figure 21 , 33A View Figure 33 )
Holotype: R dentary with P 4 –M 3 and alveoli for P 2–3, MLU.Wa/356, Walbeck.
Paratypes: See list of referred material, Walbeck ( Russell, 1964: 245).
New material: Composite upper dentition ( LP 4 –M 2, two RP 4, RM 1–3), MLU.Wa/418; composite lower dentition ( LP 4, two LM 3, RP 3, P 4, M 3), MLU.Wa/419; L dentary with P 4 –M 3, MLU.Wa103.2011; all Walbeck.
Age and distribution: Known only from the late Selandian, Middle Palaeocene fissure fillings of Walbeck, Germany.
Diagnosis: As for genus, monotypic.
Description
P 4: The five teeth show an outline subdivided into a larger buccal and a smaller lingual lobe, with a ‘waist’ in between ( Fig. 21A View Figure 21 2, B2 View Figure 2 ). The paracone is larger than the metacone ( Fig. 21A View Figure 21 1, B1 View Figure 1 ). There is a trigon basin but without intermediate conules and the postprotocrista ends at the foot of the metacone. There is a distal cingulum with a small hypocone at its lingual end. In four of the five specimens, there is no contact between the postprotocrista and the hypocone and, like Louisina , there is no preparacrista. The remaining specimen has a crest linking the postprotocrista to the hypocone, as in L. marci and Te. brisswalteri , and a preparacrista as in the latter ( Fig. 21A View Figure 21 2 View Figure 2 ).
M 1–2: These teeth are very similar in structure to those of L. marci and Te. brisswalteri (q.v.), but they are less exodaenodont and the parastyle is lower; there is a protostyle at the lingual end of the mesial cingulum of M 1, but not of M 2 ( Fig. 21B View Figure 21 ). There may be a large metastyle on M 1 ( Fig. 21B View Figure 21 2 View Figure 2 ).
M 3: This tooth is also very similar to those of L. marci and Te. brisswalteri , but relatively shorter ( Fig. 21B View Figure 21 ).
P 3: The single specimen is simple with a short distal crest from the protoconid representing the metaconid and a single cusped transversely elongate, scarcely basined talonid ( Fig. 21D View Figure 21 ). It is similar to most L. marci , but less exodaenodont and with a lower paraconid.
P 4: The pattern of similarity to L. marci is repeated here but less exodaenodont and with a distinct but tiny paraconid, which is lower on the crown ( Fig. 21C, E View Figure 21 ). The metaconid is consistently present and smaller than the protoconid. The talonid bears a hypoconid and is basined and variable in length.
Lower molars: These teeth are very similar in morphology to those of Te. brisswalteri and L. marci (q.v.) and in size to the former. They appear slightly less exodaenodont, but the difference is subtle. The main difference from Louisina is the small but distinctly cuspate paraconid, which is most obvious on the nearly unworn composite dentition MLU.Wa/415 ( Fig. 21E View Figure 21 ). The paraconid is indistinct in Louisina . There is also a slightly stronger precingulid ( Fig. 21C, E View Figure 21 1 View Figure 1 , E 2 View Figure 2 ), which is almost missing in the other two genera. There is variation for relative width of the M 2–3 trigonid, which is nevertheless always wider than the talonid. Although difficult to judge on the worn teeth, an entoconulid appears to be missing from all specimens.
Dentary: On two observed dentaries (including the holotype), the posterior mental foramen is below the M 1 trigonid ( Russell, 1964: pl. 15, fig. 6). The horizontal ramus deepens posteriorly like L. mirabilis and Te. reisi , the deepest part being below M 3.
Discussion
As with W. krumbiegeli , coefficients of variation for some molar size dimensions are rather high for a single species ( Table 8). It is possible that as in W. krumbiegeli , this represents time averaging of populations represented by the reworked Walbeck fauna.
| R |
Departamento de Geologia, Universidad de Chile |
| LP |
Laboratory of Palaeontology |
| RM |
McGill University, Redpath Museum |
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