Walbeckodon krumbiegeli, Hooker & Russell, 2012
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2011.00787.x |
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persistent identifier |
https://treatment.plazi.org/id/03DE8792-FF91-654A-FC82-FD4DFC3AFBF3 |
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treatment provided by |
Marcus |
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scientific name |
Walbeckodon krumbiegeli |
| status |
sp. nov. |
WALBECKODON KRUMBIEGELI SP. NOV.
( FIGS 2 View Figure 2 , 3 View Figure 3 , 4A, B View Figure 4 )
vp 1964 Adunator lehmani Russell ; Russell, pp. 48– 50, pl. 3, figs 4, 5b-c.
? 1964 Adapisorex abundans Russell ; Russell, pl. 5, fig. 1c (P 3).
vp 1985 Adunator lehmani Russell ; Storch & Lister, pp. 29, 33–34, figs 33–37, 39–43.
Etymology: Named after Dr Günter Krumbiegel, for his courtesy and aid to the authors during their visits to the Geiseltalmuseum, Halle.
Holotype: L dentary with P 4 –M 3, MLU. Wa 104.2011, late Selandian, Walbeck, Germany.
Paratypes: L maxillary fragment with P 3 and alveoli of P 4, MLU.Wa/363; L maxillary fragment with P 4, MLU.Wa/364; L upper composite DP 4 –M 1, MLU.Wa/ 362; L DP 4, MLU.Wa/416; L upper composite P 4 –M 3, MLU.Wa/386; L dentary with P 3–4, MLU.Wa/417; L dentary with P 4 –M 2, MLU.Wa/387; L dentary with M 1–3, MLU.Wa/365; L dentary with M 2–3, alveoli for P 3 –M 1, MLU. WB25 ; L dentary with P 4 –M 3 (M 2 with broken crown) and alveoli for P 3, MLU. WB28 ; R dentary with P 4 and alveoli for I 2 –P 3, MLU.Wa/ AC; R dentary with M 2–3 and ascending ramus, MLU.Wa/Aa; R dentary with M 3, alveoli for M 2 and part of M 1, MLU. WB26 ; composite RM 1–3 , MLU.Wa/420 .
Age and distribution: Known only from the late Selandian, Middle Palaeocene fissure fillings of Walbeck, Germany.
Diagnosis: P 4 and upper molars with distinct postparaconule crista. P 4 and M 1–2 metacone slightly lower than paracone. P 4 lacks postmetaconule crista. P 4 paraconid large, usually basined lingually and confluent with paracristid. M 1 postcingulum not joining confluent postmetaconule crista and metacingulum. M 3 lacks hypocone. M 1–2 pre-entocristid gently dipping with entoconulid. M 1 buccal crown base dipping distally (shared with Adapisorex , but unique in Louisinidae ).
Description
P 3: MLU.Wa/363 consists of a maxillary fragment with P 3 ( Fig. 2A View Figure 2 ) and the alveoli of P 4. The latter fit the roots of P 4 of the composite dentition (MLU.386: Fig. 2B View Figure 2 ). P 3 in this composite dentition, which may be the one figured by Storch & Lister (1985: fig. 38) as Adunator lehmani Russell, 1964 , the name commonly given to specimens of W. krumbiegeli , is larger and fits better with the morphology of contemporaneous Adapisorex abundans . MLU.Wa/363 has well-spaced paracone and smaller metacone, prominent parastyle, short protocone lobe, and deep pre- and postflexi that produce a waisted neck between the lobe and the rest of the tooth. In these respects the tooth is quite like P 3 of Paschatherium (e.g. Teilhard de Chardin, 1927: pl. 1, fig. 20).
P 4: The tooth is nearly molariform ( Fig. 2B View Figure 2 ). The paracone is substantially taller than the metacone and the postcingulum joins the metacingulum and bears a hypocone about half the height of the protocone. A relatively strong paraconule has welldeveloped pre- and postparaconule cristae. The postprotocrista bears a metaconule, which, however, has only a weak premetaconule crista and no postmetaconule crista. In this way it differs from the similar W. girardi , which has a strong postmetaconule crista that joins the postcingulum– metacingulum. The precingulum is short and weak.
M 1–2: On these teeth the metacone is slightly lower than the paracone ( Fig. 2B View Figure 2 ), but less marked than in W. girardi . There is a large hypocone on a postcingulum that does not join the metacingulum. The paraconule is closer to the protocone than is the metaconule. Both have pre- and postcristae, although the strengths vary a little between the two specimens studied ( MLU.Wa/362 and MLU.Wa/386). The postmetaconule crista joins the metacingulum. The precingulum is weak to missing. Parastyles are relatively weak. The postmetacrista on M 1 is relatively long .
M 3: This is a small triangular tooth, slightly wider than long, with a weak parastyle ( Fig. 2B View Figure 2 ). The metacone is much smaller than the paracone and there is only a weak postcingulum that lacks a hypocone. Unlike Paschatherium species , the paraconule and metaconule bear pre- and postcristae like M 1–2.
DP 4: The two specimens are like relatively elongate M 1 s, with a deeper postflexus, a smaller hypocone, a larger parastyle, and are more flared distobuccally ( Storch & Lister, 1985: fig. 39). There is some variation, however, in size of the parastyle and whether the ectocingulum is complete or interrupted at the paracone.
P 3: This is a simple tooth with a main protoconid, small paraconid, and very low, slightly basined bicuspid talonid ( Fig. 3B View Figure 3 ). There are mesial and distal crests from the protoconid, the former being the stronger.
P 4: This tooth is semimolariform. It is more or less wedge-shaped in outline, widening distally ( Fig. 2C View Figure 2 1 View Figure 1 ). The talonid is relatively large. In the least worn specimen, the hypoconid is slightly more than half the height of the protoconid ( Fig. 3A View Figure 3 1 View Figure 1 ). The distobuccal edge of the protoconid sweeps obliquely down the crown to near the distobuccal corner ( Fig. 3A View Figure 3 1, B1 View Figure 1 ). There is variation: in size of the entoconid, although it is always smaller than the hypoconid ( Figs 2C View Figure 2 3, 3B3 View Figure 3 ); in the angle of slope of the paracristid from relatively steep to relatively gentle ( Figs 2C2 View Figure 2 , 3A View Figure 3 1, B1 View Figure 1 ); and in the paraconid, which, although always large (more so than in any Paschatherium ), may or may not have a small lingual basin ( Figs 2C View Figure 2 , 3A, B View Figure 3 ).
Lower molars: M 1 has a paraconid nearly as large as the metaconid ( Figs 2C View Figure 2 3, 3A View Figure 3 ). This becomes progressively lower on M 2 and M 3, so that on M 3 it is only about half the height of the metaconid ( Fig. 2C View Figure 2 3 View Figure 3 ). The trigonid shortens from M 1–3. The talonid is slightly wider than the trigonid on M 1, slightly narrower on M 2, and much narrower on M 3. There may be a marked ectoflexid, especially on M 2–3. On M 3 the entoconid lies distinctly more distally than the hypoconid. The pre-entocristid dips at about 50 ° and bears an entoconulid ( Fig. 3A View Figure 3 1 View Figure 1 ). Additionally, unlike either W. girardi or any other louisinid, the crown base of M 1–2 when viewed buccally dips distally and appears slightly procumbent; the talonid overhangs slightly distally, with protruding hypoconulids ( Figs 2C2 View Figure 2 , 3A View Figure 3 1 View Figure 1 ). This is a pattern also encountered in Adapisorex and primitive Cretaceous eutherians like Ukhaatherium and Daulestes and may be primitive for the Louisinidae .
Dentary: Wa/AC shows P 4 and at least seven more mesial alveoli ( Fig. 4A View Figure 4 ). Of these, the distal-most four housed two-rooted P 2–3. The next most mesial is large, circular, and procumbent. It must represent the canine as the next two in front are much smaller and should represent I 2–3. This still leaves room for an I 1, where its alveolus has been broken away. This means that this specimen lacks P 1. However, another dentary with P 3–4 has three equal-sized, relatively small alveoli situated more anteriorly, with the more posterior two close together and the more anterior two further apart ( Fig. 3B View Figure 3 2 View Figure 2 ). This situation is best interpreted as two-rooted P 2 and probably singlerooted P 1. A third dentary (MLU. WB25) has left M 2–3 and alveoli for M 1, and two-rooted P 4 and P 3. A more anterior alveolus is only exposed basally because of breakage, so it is uncertain what tooth locus it represents. Therefore, W. krumbiegeli varies in whether P 1 is present or not. An anterior mental foramen lies below the alveoli of P 2 in the first two of these dentaries. The posterior mental foramen is below the trigonid of M 1. The angular process is slightly abraded at its tip, but would probably have extended posteriorly as far as the articular condyle as in its contemporary Adapisorex abundans . It differs significantly, however, in that the condyle is situated much further dorsally ( Fig. 4A, B View Figure 4 ). The horizontal ramus does not deepen posteriorly.
Discussion
Most specimens from Walbeck were originally attributed to Adunator lehmani , but differ significantly from the holotype dentary, which is not a louisinid (see Krishtalka, 1976; Secord, 2008). The upper molars originally attributed to Adu. lehmani by Russell (1964) and whose attribution were doubted by Krishtalka (1976), when he recognized the generic identity of North American ‘ Diacodon ’ (later Diacocherus Gingerich, 1983 ) minutus Jepsen, 1930 with Adu. lehmani , are the ones here referred to W. krumbiegeli . Upper molars of Adu. lehmani remain elusive. Specimens from Cernay attributed to Adu. lehmani do not belong to either Adu. lehmani or to W. krumbiegeli and are described here as Walbeckodon girardi sp. nov. (q.v.). Some tooth dimensions of W. krumbiegeli have unusually high coefficients of variation, whereas others are typically low ( Table 1). This may partly result from low sample numbers, but might also reflect some time averaging, as the Walbeck fauna is reworked. The high level position of the dentary condyle is similar to modern macroscelideans.
| R |
Departamento de Geologia, Universidad de Chile |
| AC |
Amherst College, Beneski Museum of Natural History |
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