Louisina marci, Hooker & Russell, 2012

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 : 909-912

LOUISINA MARCI SP. NOV.

( FIGS 23 , 24 , 25A–K, 26J, 33B )

v. 1891 Orthaspidotherium ?; Lemoine, p. 285, pl. 11, figs 105–106.

vp 1964 Louisina mirabilis Russell ; Russell, pl. 15, figs 1c–d, 2b (right P 4, left M 1).

Etymology: After Monsieur Marc Duchamplecheval for finding key specimens of the species.

Holotype: Left M 1, MNHN.F.CR-235, Cernay.

Paratypes: RP 4, MNHN.F.CR-77- MD; four LM 1 s, MNHN.F.CR-4325, CR-11907, CR-571-Ph, UCMP. 62021(CR-4321); three RM 1 s, MNHN.F.CR-240, CR-54-Bn, CR-1140-Pn; five LM 2 s, MNHN.F.CR-247, CR-32- MD, UCMP.62015(CR-248), 62010(CR-1242), SLP.CR-315; 5 RM 2 s, MNHN.F.CR-216, CR-625, CR-951, CR-15929, UCMP.62013(CR-244); 3 LM 3 s, MNHN.F.CR-4336, CR-323-L, CR-324-L; seven RM 3 s, MNHN.F.CR-1143, CR-4323, CR-11904, CR-187-Ph, CR-572-Ph, CR-68-Bn, CR-322-L; LDP 4 , MNHN.F.CR- 4397; two RP 3 s, MNHN.F.CR-312-L, UCMP.62018(CR- 308); two LP 4 s, MNHN.F.CR-76- MD, SLP.CR-1-De; two RP 4, MNHN.F.CR-233, CR-1117; LM 1, FSL.1. 882; three RM 1 s, MNHN.F.CR-1-F, CR-25- MD, UCMP.62014(CR-949); four RM 2 s, MNHN.F.CRL-568, CRL-569, CR-17- MD, UCMP.62008(CR-4330); LM 3, MNHN.F.CR-1704-Pn; two RM 3 s, MNHN.F.CR-773- Ph, CR-327-L; all Cernay .

LM 1, MNHN.F.BRL-16-G; RM 2, MNHN.F.BRL-14- Pn; LM 3, MNHN.F.BRL-126; RM 3, MNHN.F.BRL-2-G; RM 1, MNHN.F.BRL-29-G; LM 2, MNHN.F.BRL-16-Pn; RM 2, MNHN.F.BRL-25; all bed 4, Berru.

Two RM 1, MNHN.F.BR-13-Pn, I-683; five LM 2 s, MNHN.F.I-583, I-709, I-714, I-718, BR-12-Bn; RM 2, MNHN.F.I-707, LM 3, IRSNB.CR-48-B-Wouters; RP 3, MNHN.F.I-686; LP 4, IRSNB.CR-34-B-Wouters; LM 1, MNHN.F.I-721; two RM 2 s, MNHN.F.I-705, IRSNB. CR-42-B-Wouters; all bed 5, Berru.

Referred material: Two LM 3, MNHN.F.CR-1272, CR-337-L; LM 1, MNHN.F.CR-15936(Collier835); LM 2, UCMP.62020(CR-233); all Cernay. LM 2, IRSNB.Wouters (unnumbered), bed 5, Berru?

Casts in MNHN.F: Two LP 4 s, CR-59-Rob, CR-115-Lx; LM 1, CR-1106-Pn; two RM 1, CR-7-Rob, CR-71-Ro; two LM 2, CR-17-Mar, CR-66-Mar; two RM 3, CR-51-Mar, CR-1064-Pn; all Cernay.

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

Diagnosis: P 4 with distally positioned postprotocrista. P 4 metacone slightly smaller than paracone. P 4 protocone recurvature minor. P 4 with metaconid and short talonid basin. P 4 and molar exodaenodonty moderate. Buccal cusps of molars not high crowned, so buccal and lingual cusps are widely spaced. Entoconulid strong on M 1, weak to absent on M 2 (shared with Te. brisswalteri ).

Description

P 4: Although slightly shorter (mesiodistally) lingually than buccally, the outline is not constricted or ‘waisted’ as in Pr. atavella ( Fig. 25A 2 ). Length ranges from 2.81–2.86 mm (mean 2.84) and width from 3.73– 4.09 mm (mean 3.90). Two of the three specimens are lightly worn. They have the metacone smaller than the paracone ( Fig. 25A 1 ), the latter lacking a preparacrista, with a protocone that is scarcely recurved and a distally extending postprotocrista ( Fig. 25A 2 ). The latter is at first orientated mesiodistally, bending sharply to a buccolingual orientation. At the bend, a short crest joins it to a tiny hypocone. In CR-59-Rob, the postprotocrista dies out at the foot of the metacone, whereas in MNHN.F.CR-77- MD ( Fig. 25A 2 ), it curves mesiobuccally to rise up the lingual valley between the paracone and metacone. The preprotocrista in CR-59-Rob leaves the protocone mesiobuccally to join the paracingulum, whereas in MNHN.F.CR-77- MD, its direction is nearly mesial, joining the paracingulum more lingually. The precingulum is very short, almost meeting the preprotocrista in MNHN.F.CR-77- MD. The parastyle is very low and small in both. A third specimen (CR-115-Lx) is damaged distolingually and is more worn, but the hypocone is larger and closer to the protocone. The buccolingual branch of the postprotocrista is very faint .

M 1: The squared outline is a consistent feature of this tooth type ( Fig. 25B, J). There is variation in cingulum development. The ectocingulum may be complete [ UCMP.62021(CR-4521)] or entirely missing, but is weak and interrupted in most. The premetaconule crista may be present or absent, but is absent or negligible in most. The crest that joins the metaconule and hypocone is present in most specimens observed ( Fig. 25B 2 ) but two ( MNHN.F.BR-13-Pn, MNHN.F.CR-240: Fig. 25J), although it is very variable in strength. The wider spacing of the buccal and lingual cusps distinguishing this species from L. mirabilis is best seen in distal view ( Fig. 25B 3 , L) .

M 2: The trapeziform outline is a consistent feature of this tooth type, with an oblique buccal margin and large size difference between the paracone and metacone ( Fig. 25C, K). However, the difference in cusp size is not quite as great as in L. mirabilis . The variation in the premetaconule crista is as on M 1. However, the ectocingulum varies from weak and interrupted to absent. Like M 1, the metaconule– hypocone crest is variable in strength and is missing on three (MNHN.F.CR-625, MNHN.F.I-718, MNHN. F.CR-247: Fig. 25K), but in several (e.g. MNHN.F.I- 714) it forms more of an incipient metaloph than on M 1. In only two (UCMP.62010, UCMP.62015) of the 16 observed specimens is there a high parastyle like Teilhardimys . They are not in the apparent size overlap zone with Te. brisswalteri , so are unlikely to belong to this species.

M 3: The outline is always triangular ( Fig. 25D). The structure is that of a simple trigon, but beyond that, the morphology is very variable. The metacone may be lingual of the midline or near the buccal margin (MNHN.F.BRL-2-G). The parastyle is variable in size. The pre- and postcingula may be present or absent. On some there is a large metastyle (e.g. MNHN.F.BRL-126-L). In most the paracone is much larger than the metacone, but in one there is much less difference (MNHN.F.BRL-2-G). MNHN.F.CR- 68-Bn has a strong postparaconule crista, whereas two others have faint ones. Paracone crown height is less than in L. mirabilis , the best means of differentiation between the two species. Length ranges from 1.98–2.36 mm (mean 2.14) and width from 2.41– 2.75 mm (mean 2.56).

P 3: All three specimens are similar, but only one ( MNHN.F.CR-312-L) is sufficiently complete basally for a complete description ( Fig. 25E). The paraconid and talonid are high and overhang the mesial and distal margins, respectively. The talonid is very short and unbasined, the single cusp being transversely elongate and bluntly crested buccally and lingually. Exodaenodonty is strong, affecting the entire buccal margin, not divided into mesial and distal lobes. A faint cristid obliqua lies slightly buccal of a distal protoconid crest that dies out before reaching the talonid and represents an incipient or vestigial metaconid. Length ranges from 2.91–3.10 mm (mean 3.00) and width from 2.09–2.30 mm (mean 2.20) .

P 4: The paracristid is mesiodistally orientated and dips gently mesially to a raised mesial edge, but with scarcely any representation of a differentiated paraconid ( Fig. 25F). The talonid is short, but basined and with a distinct hypoconid, unlike L. mirabilis . Exodaenodonty is strong, but less than in L. mirabilis . In most specimens the metaconid is distinct but variable in size, although always smaller than the protoconid. In SLP.CR-1-De, however, although worn, the metaconid seems to be represented by little more than a short distal protoconid crest as on P 3. The tooth is, however, too large to be a P 3. Length ranges from 2.92–3.49 mm (mean 3.12) and width from 1.97– 2.48 mm (mean 2.22).

M 1: The talonid is either slightly wider than the trigonid ( Fig. 25G 1 ) or the two are approximately equal in width. The talonid is also slightly shorter than the trigonid, but almost as high ( Fig. 25G 2 , G 3 ). The premetacristid is consistently present and joins or almost joins the tiny paraconid, which is lower on the crown than in L. mirabilis . An entoconulid of variable size is present on most specimens. The paracristid slopes mesially more steeply than in L. mirabilis , consistent with the lack of a shearing P 4 –M 1 complex in L. marci . In three out of eight specimens the precingulid joins the paracristid. MNHN.F.BRL-29-G is unusual in having a sharp bulge projecting buccally from the base of the hypoconid. It is preceded by a weak ectostylid and lacks an entoconulid. Although appearing pathological, another M 1 from the same side of the jaw, therefore belonging to another individual (CR-71-Ro), is very similar.

M 2: MNHN.F.CRL-569 from Lemoine’s collection is the best preserved and least worn ( Fig. 25H). M 2 s are larger than M 1 s and with a talonid that is distinctly narrower, shorter, and lower than the trigonid, although the difference is somewhat variable. In three out of 11 specimens the precingulid joins the paracristid. Unlike M 1, all M 2 s observed lack an entoconulid. They also differ in this way from the three M 2 s of L. mirabilis .

M 3: All specimens observed are similar in crown height to the lower crowned variants of L. mirabilis , although they differ in having slightly more steeply mesially sloping paracristids, a normal notched protocristid, and no precingulid ( Fig. 25I). There is slight variation in the relative sizes of trigonid and talonid, but this is less marked than in L. mirabilis . Length ranges from 2.59–3.11 mm (mean 2.95) and trigonid width from 2.15–2.56 mm (mean 2.38).

DP 4: The tooth is 3.17 mm long by 3.00 mm wide and trapeziform in outline ( Fig. 26J). It is smaller, relatively narrower, and lower crowned than M 1 and with a larger parastyle, as expected of a DP 4. The base of the paracone is broken but the metacone shows an exodaenodont lobe like M 1. The hypocone is slightly smaller than the protocone and is joined by a crest to the postprotocrista as on many M 1 s. The metaconule has no crests. There is a postparaconule crista but no preparaconule crista. The precingulum ends lingually with a protostyle. The paracone and metacone are closer together than on M 1. DP 4 of Te. musculus differs in having more widely separated paracone and metacone, less trapeziform outline, a larger hypocone, and a complete metaloph.

Figures

Figure 1. Dental terminology. A, B, upper molar; C, D, lower molar, all shown as from left side in occlusal view. Mesial is to left; distal is to right; buccal in uppers is above and in lowers below; lingual in uppers is below and in lowers above. A, C, primitive morphotype; B, D, derived morphotype. Some cusps and crests shown in A and C are assumed for B and D, respectively. Some taxa combine some features of the different morphotypes. Abbreviations: co, cristid obliqua; dclm, distal cingulum; ecf, ectoflexus; ecfd, ectoflexid; eclm, ectocingulum; ectsd, ectostylid; entd, entoconid; entf, entoflexus; entld, entoconulid; ents, entostyle; hyd, hypoconid; hyfd, hypoflexid; hyld, hypoconulid; hyp, hypocone; hyphd, hypolophid; mbstd, mesiobuccal stylid; mclm, mesial cingulum; mes, mesostyle; mesd, mesoconid; mestd, mesostylid; met, metacone; metclm, metacingulum; metd, metaconid; metle, metaconule; metph, metaloph; mets, metastyle; pacd, paracristid; paclm, paracingulum; pad, paraconid; par, paracone; parle, paraconule; pas, parastyle; pocld, postcingulid; poclm, postcingulum; pof, postflexus; poentcd, postentocristid; pohycd, posthypocristid; pomec, postmetacrista; pometcd, postmetacristid; pometlc, postmetaconule crista; popac, postparacrista; poparlc, postparaconule crista; poprc, postprotocrista; precld, precingulid; preclm, precingulum; preentcd, pre-entocristid; pref, preflexus; premec, premetacrista; premetcd, premetacristid; premetlc, premetaconule crista; prepac, preparacrista; preparlc, preparaconule crista; preprc, preprotocrista; procd, protocristid; prot, protocone; protd, protoconid; prs, protostyle; prtph, protoloph; prtphd, protolophid; tb, trigon basin; tgb, trigonid basin; tlb, talonid basin. Tooth abbreviations in text: I, incisor; C, canine; P, premolar; M, molar; DP, deciduous premolar.

Figure 2. Scanning electron micrographs of gold-palladium coated epoxy casts of teeth and jaw of Walbeckodon krumbiegeli gen. et sp. nov., Palaeocene, Walbeck, Germany. A, paratype LP3 (MLU.Wa/363). B, paratype composite dentition, LP4, LM1, LM2, LM3 (MLU.Wa/386). C, holotype left dentary with P –M (MLU.Wa104.2011). Views are: buccal 4 3 (A1, B1, C2), occlusal (A2, B2, C1), and lingual (C3). Scale bar = 2 mm.

Figure 3. Scanning electron micrographs of gold-palladium coated epoxy casts of jaws of Walbeckodon krumbiegeli gen. et sp. nov., Palaeocene, Walbeck, Germany. A, paratype left dentary with P4–M2 (MLU.Wa/387). B, paratype left dentary with P3–4 (MLU.Wa/417). Views are: buccal (A1, B1), occlusal (A2, B2), and lingual (B3). Scale bar = 2 mm.

Figure 23. Scatter diagrams of Ln length vs. Ln width in millimetres of molars of Louisina spp. and Teilhardimys brisswalteri sp. nov. For explanation of symbols see Figure 8. A, M1; B, M2; C, M; D, M.

Figure 24. Histograms of Ln length ¥ width in millimetres (A) and the distance between M1 paracone and protocone and between M1 hypoconid and entoconid, each as a percentage of tooth width (B), of Louisina spp. and Teilhardimys brisswalteri sp. nov. Lined boxes in A indicate Louisina mirabilis. Arrowed names indicate holotypes of species. See text for further explanation.

Figure 33. Occlusal diagrams of P4, P, and (except Teilhardimys musculus) M trigonid of Prolouisina atavella (A), 4 1 Louisina marci (B), Louisina mirabilis (C), Teilhardimys brisswalteri (D), and Te. musculus (E). Facets are numbered following Butler (1952a, b). Uppers are shown as from left side, lowers from right side. Diagrams are partly schematic, drawn from the maximum number of informative specimens. C is based on MNHN.F.CR-248-Bn, MNHN.F.BRL-3-Pn, and MNHN.F.BR-143. E is based mainly on NHMUK.M29708 and M50379. Taxa not shown to scale.