Louisina, RUSSELL, 1964

Hooker, Jerry J. & Russell, Donald E., 2012, Early Palaeogene Louisinidae (Macroscelidea, Mammalia), their relationships and north European diversity, Zoological Journal of the Linnean Society 164 (4), pp. 856-936 : 901-907

publication ID	https://doi.org/ 10.1111/j.1096-3642.2011.00787.x
DOI	https://doi.org/10.5281/zenodo.10544466
persistent identifier	https://treatment.plazi.org/id/03DE8792-FFBF-657E-FC6A-FB2AFA0DF8EF
treatment provided by	Marcus
scientific name	Louisina
status

Treatment

GENUS LOUISINA RUSSELL, 1964

Type species: Louisina mirabilis Russell, 1964 , late Thanetian, Cernaysian ELMA, Cernay, Berru.

Referred species: Louisina marci sp. nov., late Thanetian, Cernaysian ELMA, Cernay, Berru.

Diagnosis: Large louisinids. Cheek teeth bulbous with moderate to extreme exodaenodonty on both upper and lower molars. P 4 postprotocrista weak to absent. P 4 protocone buccally recurved and without preparacrista. P 4 talonid short to absent and mesial margin high. M 1 with: hypocone subequal to protocone (shared with Teilhardimys and Dipavali ); metacone slightly lower than paracone. Parastyle high on M 1, low on M 2–3. M 1–2 with postprotocrista, postparaconule crista, and usually metaconule–hypocone crest. M 1 paraconid indistinct, high. M 1 metaconid smaller than protoconid. M 1 with: hypoconid more than half height of protoconid; entoconid subequal to metaconid (shared with Teilhardimys ). M 1–2 precingulid strength: weak, short; position: high, joins paracristid OR, observed range; SD, standard deviation; V, coefficient of variation (SD as percentage of the mean).

to form mesiobuccal stylid in some individuals (shared with Te. brisswalteri ).

LOUISINA MIRABILIS RUSSELL, 1964

( FIGS 22–24 View Figure 22 View Figure 23 View Figure 24 , 25L, 33C View Figure 33 )

* v 1964 Louisina mirabilis Russell : pp. 243–245, pl. 15, fig. 2a, 2b (right M 2).

v. 2006 cf. Microhyus sp. ; Tabuce, Antunes, Smith & Smith, pp. 38–39, fig. 1A.

Holotype: L dentary with crowns of M 1–3 and alveoli of P 2–4, MNHN.F. BR143 ; bed 5, Berru.

Paratypes: R dentary fragment with M 2–3 (MNHN.F.BR-4406); bed 5, Berru. The remaining paratypes listed by Russell (1964: 305) are transferred here to L. marci sp. nov., Te. brisswalteri sp. nov., and B. poirieri gen. et sp. nov. (q.v.).

New material: LP 4, MNHN.F.CR-248-Bn; RM 1, UCMP.62011(CR-239); LM 3, MNHN.F.CR-4329; RM 3, MNHN.F.CR-1285; LM 3, MNHN.F.CR-1442-Pn; RM 3, MNHN.F.CR-75-MD; all Cernay.

LP 3, MNHN.F.BRL-5-G; RP 4, MNHN.F.BRL-3- Pn; two RM 1, MNHN.F.BRL-8-F, BRL-22-G; LM 2, MNHN.F.BRL-16-Pn; all bed 4, Berru.

R maxilla, M 1–2, MNHN.F.BR-7-Lass; RM 1, MNHN.F.BR-3-L; LM 1, MNHN.F.I-729; RM 3, MNHN. F.I-728; all bed 5, Berru.

L maxilla, M 2 (broken)–M 3, MNHN.F.R-243, Cernay or Berru (preservation suggests bed 5, Berru).

Casts in MNHN.F: LM 3, CR-499-C(Collier), Cernay. RM 1, BR-333-CGH, bed 5, Berru.

Age and distribution: Sables de Châlons-sur-Vesle supérieurs, late Thanetian, Late Palaeocene, Cernay and Berru (beds 4, 5), France.

Emended diagnosis: P 4 postprotocrista absent. P 4 metacone very small on distal crest of paracone. P 4 protocone recurvature major. P 4 blade-like, lacking metaconid and talonid. P 4 and molar exodaenodonty extreme. Buccal cusps of molars high crowned, leading to proximity of buccal and lingual cusps. Entoconulid strong on M 1–2.

Description

Premolars: The single P 3 is in a fragment of maxilla ( Fig. 22A View Figure 22 ). It is approximately 2.5 mm long by 2.9 mm wide. It is moderately worn and has suffered patchy erosion of enamel, particularly buccally and basally. Nevertheless, the main structure is clear. It has a single main buccal cusp, the paracone, with uncertain developments of parastyle and metastyle. There appear to be remnants, largely worn away, of a faint postprotocrista that passes up the middle of the postparacrista. The preprotocrista dips steeply at first then curves buccally to join the paracingulum, apparently without intervention of a paraconule. The protocone is pointed and slightly buccally recurved, with oblique wear distal of its tip and exposed dentine mesiobuccally.

1 2

The single P 4 is well preserved and lightly worn ( Fig. 22B View Figure 22 ). It is similar in structure to P 3, but larger, being 2.86 mm long by 3.66 mm wide. There is a tiny metacone half way down the postparacrista, which scarcely alters the symmetry. The protocone is strongly buccally recurved. Mesial and distal crests from the protocone dip first slightly lingually, then sweep in an arc basally to meet mesial and distal cingula, which respectively meet a weak parastyle and even weaker metastyle. The distal crest has the appearance of a postprotocingulum as occurs commonly in plesiadapiforms and primitive primates. There is no ectocingulum. There are also no intermediate conules or any trigon cristae.

The single P 4 is blade-like and exceptionally exodaenodont, with distinct mesial and distal lobes, the latter the deeper ( Fig. 22F View Figure 22 ). It is 2.82 mm long by 2.51 mm wide. There is a single main cusp, the protoconid, with strong mesial and distal crests dipping respectively to a tiny parastylid and a slightly larger distal cusp that represents a greatly reduced basinless talonid. Both mesial and distal cusps head blunt short cingula both buccally and lingually.

M 1: MNHN.F.BR-3-L is nearly unworn ( Figs 22C View Figure 22 , 25L). It shows closely spaced buccal and lingual cusps, a postprotocrista that is broken adjacent to the metaconule. The metaconule is close to the hypocone but not linked by a crest. Deep exodaenodont lobes extend the paracone and metacone basally. The paracone is larger than the metacone, but the protocone and hypocone are of essentially equal height. A similar pattern exists in UCMP.62011 (CR-239), despite moderate wear. Deep wear in MNHN.F.BR-7- Lass has removed most crown features, although it is still possible to pinpoint the centres of the four main cusps in the pattern of the dentine ( Fig. 22D View Figure 22 2 View Figure 2 ).

M 2: Only one tooth is sufficiently lightly worn to show any detail. This is MNHN.F.BR-7-Lass, which accompanies M 1 in a maxillary fragment, where part of the base of the orbit is preserved above the two molars ( Fig. 22D View Figure 22 ). The worn paracone is much larger than the metacone and the worn protocone is much larger than the unworn hypocone. The paracone alone has a long exodaenodont lobe, the outline of the tooth being much contracted distally. A short preprotocrista is fused to the protocone in one area of exposed dentine. A thin, low postprotocrista links the protocone to the metaconule, which is isolated from the adjacent hypocone as on M 1. The proximity of the buccal and lingual cusps leaves only a small shallow trigon basin.

M 3: CR-1285 is the only near complete tooth recognized (only the parastylar area is broken away). It is triangular and slightly wider than long, being c. 2.05 mm long by 2.75 mm wide. Although eroded basally,

it is still evident that the paracone is much larger than the metacone and is the dominant cusp ( Fig. 22E View Figure 22 ). There is a simple trigon with precingulum and no postcingulum, although these features may be variable if one considers the larger assemblage of L. marci (q.v.). There is a postparaconule crista unlike most L. marci M 3 s. There is no ectocingulum.

Only the buccal part of the M 3 is preserved in the fragmentary maxilla (MNHN.F.R-243). It is also very worn, but what is left of the paracone suggests original substantial crown height and supports referral of MNHN.F.CR-1285. MNHN.F.CR-4329 is complete but all crown features have been removed by wear. It appears also to have had relatively high cusps.

M 1: Subequal exodaenodont lobes extend deeply basally from trigonid and talonid ( Fig. 22G View Figure 22 2 View Figure 2 ). The cristid obliqua is strong, gently dipping to the back of the trigonid between the protoconid and metaconid. BR-333- CGH has a strong premetacristid that gently slopes to meet the small paraconid, completely enclosing a trigonid basin. The other three sufficiently complete M 1 s, including that of the holotype, lack a distinct premetacristid and thus have a trigonid basin that is open mesiolingually ( Fig. 20L, O View Figure 20 ). In all cases the paracristid slopes very gently mesially, forming a high shearing blade that participates in the lower P 3 to M 1 blade complex (see below). None of the three specimens has the precingulid joining the paracristid. All have an entoconulid on the pre-entocristid .

M 2: All three specimens have a strongly exodaenodont trigonid and a weakly exodaenodont talonid ( Fig. 22G View Figure 22 2 View Figure 2 ). The talonid is narrower, shorter, and much lower than the trigonid. The general pattern is as on M 1, including presence of an entoconulid ( Fig. 22G View Figure 22 1 View Figure 1 ). There is variation in relative width of the trigonid and talonid, with attendant slight differences in attachment position of the cristid obliqua, ranging between the middle to lingual parts of the protoconid. All three specimens have a weak premetacristid, which essentially encloses a shallow trigonid basin. In one out of three specimens the precingulid joins the paracristid.

M 3: There is a deep exodaenodont lobe from the trigonid only ( Fig. 22G View Figure 22 2 View Figure 2 ). On three specimens including the holotype, the protocristid is broken and a neoformed crest (incipient protolophid) crosses the trigonid basin directly between the protoconid and metaconid ( Fig. 22G View Figure 22 1 View Figure 1 ). On a fourth ( MNHN.F.CR- 1442-Pn), there is a normal notched protocristid. There is variation for relative lengths, widths, and heights of trigonid and talonid. Thus, MNHN.F.CR- 1442- Pn has a very tall protoconid and a small talonid, whereas in the holotype and MNHN.F.I-728 the talonid is more elongate and the protoconid lower. Unlike M 1–2, there is a distinct precingulid on all except MNHN.F.CR-1442- Pn .

Discussion

The original concept of L. mirabilis included what are here named as two other species, L. marci sp. nov. and Te. brisswalteri sp. nov. Despite this broad original view of L. mirabilis , some concern about the extent of variation in size and morphology was expressed ( Russell, 1964: 244). Scattergrams of Ln length and width of what are usually considered the least variable teeth, M 1, M 2, M 1, and M 2, show extended plots ( Fig. 23 View Figure 23 ). Histograms of Ln length ¥ width show bimodality ( Fig. 24A View Figure 24 ), suggesting two species based on size. Coefficients of variation for length and width covering all available specimens of these tooth types from Cernay and Berru that share the broad morphology of L. mirabilis are high ( Table 9), indicating more than one species. The smaller of these based on the scattergrams and bimodal histograms is the taxon described below as Te. brisswalteri sp. nov. As restricted, its coefficient of variation for length and width of preultimate molars is low, indicative of a single species.

Two factors, however, suggested the presence of more than one species within the grouping of larger teeth. Firstly, there are three different types of upper and lower fourth premolars that are uniquely contenders for association with this group, based on knowledge of Pr. atavella (q.v.), of which two are larger than the third. Secondly, variation in exodaenodonty and apparently in crown height of the molars was noted, which suggested a degree of variation