Castor fiber Linnaeus, 1758

Laere, Gaëlle Van & Mörs, Thomas, 2023, Beavers and flying squirrels (Rodentia: Castoridae, Pteromyini) from the Late Pliocene of Hambach 11 C, Germany, Geodiversitas 45 (7), pp. 223-241 : 226

Castor fiber Linnaeus, 1758

( Fig. 3 )

MATERIAL EXAMINED. — Left m1/2 ( IPB-HaR-5641 ), left P4 ( IPB- HaR-5637 and IPB-HaR-5640 ), left M1/2 ( IPB-HaR-5638 and IPB-HaR-5639 ), incisor fragment ( IPB-HaR-5653 ).

MEASUREMENTS. — See Table 1.

DESCRIPTIONS

I – HaR-5653 ( Fig. 3A ).

A fragment of an incisor exhibits the smooth enamel and a rather flattened surface with both lateral edges curved. N

m1/2 – HaR-5641 ( Fig. 3B )

Unworn tooth germ showing the original cusp configuration. Rectangular shape, the labial side is slightly shorter than the lingual side. There is a small cusplet on the labial side of the protoconid, below the occlusal surface ( Fig. 3B 2 ). All the striids reach the base of the tooth. There is some cement in the striids. The metaconid is the highest cusp, followed by the paraconid. The hypoflexid and metaflexid are “face to face”. The hypoflexid is oriented posteriorly. The paraflexid and mesoflexid are oriented anteriorly. No roots are developed.

P4 – HaR-5637 and HaR-5640 ( Fig. 3C, D )

HaR-5637 ( Fig. 3C ) is slightly worn and preserved in a maxillary fragment with no other tooth in situ whereas HaR-5640 ( Fig. 3D ) has an occlusal surface too damaged to determine a wear stage. There is clearly cement in the striae. On HaR- 5637, they all seem to run through the entire height of the tooth. This is not the case on HaR-5640 where the end of the parastria is visible and the mesostria seems to be closing. The anterior and posterior sides are slightly rounded. The lingual side is shorter than the labial. Although on HaR-5640, the outer wall is damaged, it seems that its posterior side was flatter than that of HaR-5637. The hypoflexus and the paraflexus are “face to face”. On HaR-5637, the hypoflexus is curving anteriorly. The mesoflexus and paraflexus are curving anteriorly, then posteriorly and are parallel to each other. The mesoflexus and metaflexus almost reach the posterior wall. On HaR-5640, the mesoflexus is broken but seems to be curving posteriorly and the metaflexus is not preserved. HaR-5637 does not have formed roots, the base is still open. On HaR-5640, this part is not preserved.

M1/2 – HaR-5638 and HaR-5639 ( Fig. 3E, F )

Both teeth are slightly worn. The shape is square with the anterior side slightly rounded and the lingual side slightly smaller than the labial side. Both characteristics are less marked than on the P4. The hypostria runs through the entire height of the tooth. On the labial side, the parastria is the shortest on HaR-5638 and the mesostria the longest almost reaching the end of the tooth crown. On HaR-5639 the metastria is the shortest and the parastria and mesostria are about the same length. There is clearly cement in the striae. The paraflexus and hypoflexus are “face to face”. On HaR-5638, they are both oriented towards the anterior side and on HaR-5639, the hypoflexus is going anteriorly and the paraflexus is rather straight and horizontal. The mesoflexus changes orientation mid-way to go toward the posterior side and almost reaches the posterior wall, the angle of the curve is close to 90° on HaR-5639. On this tooth, the metaflexus is dipping anteriorly at its mid-point whereas on HaR-5638, the metaflexus is going slightly posteriorly but is relatively straight and reaches the end of the mesoflexus. The enamel of the hypoflexus is thickened on its anterior side and so is the enamel of the mesoflexus. Both do not have roots.

REMARKS

The attribution to Castor fiber was made based on the observation of several characters. Firstly, the smooth enamel of the incisor and its almost flat face ( Newton 1902; Fostowicz-Frelik 2008; Cuenca-Bescós et al. 2015) but also the presence of cement ( Mayhew 1978) and the lack of roots ( Rekovets et al. 2009) as well as the fact that the hypostria runs down the entire height of the tooth, unlike in Trogontherium ( Fostowicz-Frelik 2008) . Moreover, the size and morphology of the specimens are coherent with other finds, for example from Early Pleistocene sites in Romania and Spain (Olteţ River Valley, Gran Dolina and Sima del Elefante) and from the Middle Pleistocene of Portugal (Gruta da Aroeira) ( Cuenca-Bescós et al. 2015; 2021; Terhune et al. 2020) and with recent specimens (personal observations in the collections of the NRM). Castor fiber has previously been reported from the Late Pliocene of Hambach 11 (MN16a) by Mörs et al. (1998). It was also found in the Late Pliocene (MN16a) Slovakian locality of Hajnačka I ( Sabol et al. 2006). Castor fiber is one of two species of Castor still present today ( Stefen 2011). The genus Castor appears in the European fossil record during the Late Miocene ( Hugueney 1999), and is already present in Germany at this time ( Cuenca-Bescós et al. 2015). The species Castor fiber appears in the middle Villafranchian ( Barisone et al. 2006). The quasi absence of wear on HaR-5641 indicates that it belonged to a really young individual, less than five months old according to the tooth pattern ( Stefen 2009).

Figures

FIG. 3. — Castor fiber Linnaeus, 1758 from Hambach 11C: A, IPB-HaR-5653, incisor fragment labial view and section; B, IPB-HaR-5641, left m1/2 labial,occlusal and lingual views;C, IPB-HaR-5637,left P4 in maxillary fragment, labial, occlusal, and lingual views; D, IPB-HaR-5640, left, P4 labial, occlusal, and lingual views; E, IPB-HaR-5639, left M1/2, labial, occlusal, and lingual views; F, IPB-HaR-5638, left M1/2 labial, occlusal, and lingual views. Scale bar: 2 mm.

FIG. 2. — Stratigraphic column of the section.