Pliopetaurista pliocaenica Depéret, 1897

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 : 236-238

Pliopetaurista pliocaenica Depéret, 1897 ( Fig. 8 )

MATERIAL EXAMINED. — Right m1/2 ( IPB-HaR-5614 and IPB- HaR-5627 ), left m1/2 ( IPB-HaR-5625 ), left m3 ( IPB-HaR-5628 ), right P4 ( IPB-HaR-5629 ), left P4 ( IPB-HaR-5631 ), left M1/2 ( IPB-HaR-5632 , IPB-HaR-5634 and IPB-HaR-5635 ) , right M1/2 ( IPB-HaR-5633 ).

MEASUREMENTS. — see Table 3.

DESCRIPTIONS

m1/2 – HaR-5614, HaR-5625 and HaR-5627

( Fig. 8 B-D)

Outline almost square but the anterior side is slightly less wide than the posterior side. The enamel is smooth. On HaR-5614 ( Fig. 8B ), the labial side is also longer than the lingual side and there is a contact facet on the anterior side. This specimen also shows a wear facet on top of the protoconid and the mesostylid also shows signs of wear. HaR-5627 ( Fig. 8D ) is more worn with the anterior and posterior side showing contact facets. The metaconid, protoconid, and hypoconid exhibit wear facets. The facet on the hypoconid is smaller than the other two. The mesoconid of HaR-5627 as well as the postero-lingual side of the hypoconid and the protoconid seem quite worn. The metalophid is very low on all specimens although less in HaR-5614. The anterolophid is low. The talonid basin is large and deep, and the trigonid basin is also quite large although on HaR-5625 ( Fig. 8C ), the metalophid is so faint that it does not close the trigonid basin. On this specimen, there is also a small basin delimited at the posterior part by the posterolophid and the entolophid. On HaR-5614, a small lophid is erupting towards the talonid basin from the lophid between the hypoconid and mesoconid. The protoconid and hypoconid are high and dominate the lower mesostylid, mesoconid and entoconid. There is no anteroconid. The syncline between the mesostylid and entoconid is quite wide, deep and its walls are steep. The mesostylid is linked to a high metaconid by a pronounced lophid. No roots are preserved on HaR-5614 and 5625. On HaR-5627 however, four roots are preserved. The one on the labial side is the most prominent. The anterior roots go straight down and are quite round whereas the posterior ones are dipping posteriorly. The lingual root is more oval. The posterior roots are fused at the crown base (at least 1/3rd of their length). The anterior roots are completely separated and more broken off.

m3 – HaR-5628 ( Fig. 8E )

The surface of the enamel is smooth. This specimen is broken mid protoconid. The anterior arc, including the metaconid, is missing. The anterior wall of the protoconid is preserved as well as the hypoconid, entoconid, and mesostylid. The lophid between metaconid and hypoconid is quite worn as well as the syncline between the entoconid and the mesostylid. The anterior part of the entoconid is also worn and the labial side of the mesostylid shows a small wear facet. The protoconid is high, dominating the three remaining cusps and has a wear facet on its top. The lophid going from the mesostylid to the labial side creates a basin. No roots are preserved.

P4 – HaR-5629 and HaR-5631 ( Fig. 8F, G )

The outline is triangular and the enamel smooth. The hypocone is very weak. The protocone and the paracone are high although the highest is the protocone. On HaR-5629 ( Fig. 8F ), the paracone exhibits a wear facet on its anterior side and so does the parastyle, which also bears scratches, although on its posterior side. There is also a big wear facet on the lingual side of the protocone of this specimen. On this specimen, the metaconule and protoconule also appear worn. The mesostyle is well defined and on HaR-5631 ( Fig. 8G ), linked to the metacone by a very small loph. The mesostyle appears worn on HaR-5629. The metaconule is well delimited and is separated by a syncline from the protocone on HaR-5631. The trigon basin is deep but narrow. There is a deep valley between the paracone and the parastyle.The small protoconule is separated from the paracone by a small syncline. A posterior lophule erupts from the metacone and almost reaches the low posteroloph forming depressions and there is a depression on the posterior side of the metacone. No roots are preserved.

M1/2 – HaR-5632, HaR-5633, HaR-5634 and HaR-5635 ( Fig. 8 H-K)

The specimens have a square/rhomb shape, the enamel is smooth, and the posterior side is slightly less wide than the anterior one. This difference is more marked on HaR-5635 ( Fig. 8K ). On HaR-5632 ( Fig. 8H ), small wear facets are visible on the anterior side of the paracone and the metacone. Moreover, the protoloph shows signs of wear. The presence of a wear facet is observed on the anterior side of the paracone on HaR-5633 ( Fig. 8I ). On HaR-5634 ( Fig. 8J ), there are wear facets on the paracone (posterior side), the metacone (anterior side) and two small ones on the parastyle as well as on the metaconule. On HaR-5635, there is a big wear facet visible on the parastyle and one postero-lingually on the paracone and the metacone seems worn. The anterior sides of HaR-5634 and 5635 appear more worn than on the other two specimens. The anteroloph is very faintly crenulated on HaR-5633. The protocone is the highest cusp. The protoconule is, when present, very faint and the protoloph is slightly curving posteriorly on HaR-5632. A deep and wide valley separates the paracone and parastyle. The latter is higher and more developed on HaR-5634 and 5635 than on HaR-5632 and 5633. The mesostyle is less expressed than on the P4s and most visible on HaR-5634. It is separated from the metacone on HaR- 5632 and 5634, by a medium syncline. The hypocone is present. The posteroloph is very low. A posterior lophule erupts from the metaconule and reaches the posteroloph forming depressions on both sides. A small depression is visible on the posterior side of the metacone. No roots are preserved, except in HaR-5633 where a small part of three roots is present.

REMARKS

The relatively large size coupled with the complex morphology of our specimens are fitting into the Pliopetaurista genus ( Mörs et al. 1998). Moreover, the smooth enamel differs from Miopetaurista where it is wrinkled or “chagriné” ( Mein 1970) and the convergent protoloph and metaloph on the upper molars further confirm this identification ( Mein 1970; Qiu & Li 2016). The dimensions of our specimens fit into the range of Pliopetaurista pliocaenica ( Fig. 9 ) and are bigger than other species such as Pliopetaurista dehneli Sulimski, 1964 ( Mein 1970) as confirmed by Fig. 9 . This species is the closest in size and morphology to P. pliocaenica ( Mörs et al. 1998; Gárcia-Alix et al. 2007; Mansino et al. 2018). Moreover, we observe the presence of a faint but present mesostyle or bulged mesostylar crests that is absent in P. dehneli ( Gárcia-Alix et al. 2007) . The low metalophids and the presence of hypocones on the molars also point in the direction of P. pliocaenica . It is not attributed to Pliopetaurista cf. pliocaenica sensu de Bruijn (1995) and Gárcia-Alix et al. (2007) because our specimens are not large enough ( Fig. 9A ). All these observations allow us to attribute the specimens to P. pliocaenica . This species ranges from the latest Miocene to the Plio-Pleistocene ( Colombero & Carnevale 2016) which is coherent with the age of our locality. There are only four previous records of Pliopetaurista in the Pliocene of Germany, from three different localities. Mein (1970) and Dahlmann (2001) both described specimens from Wölfersheim, Fejfar & Storch (1990) reported an isolated molar from Gundersheim and Mörs et al. (1998) reported several specimens from Hambach. Most of these reports are of P. pliocaenica , with the exception of the specimens of P. raui Dahlmann, 2001 in Dahlmann (2001).

Figures

FIG. 8. — A, Blackia miocaenica Mein, 1970 from Hambach 11C, IPB-HaR-5636, left M3; B-K, Pliopetaurista pliocenica from Hambach 11C: B, IPB- HaR-5614, right m1/2; C, IPB- HaR-5625 left m1/2; D, IPB- HaR-5627, right m1/2; E, left m3; F, IPB-HaR-5629, right P4; G, IPB- HaR-5631, left P4; H, IPB- HaR-5632, left M1/2; I, IPB- HaR-5634, right M1/2; J, IPB- HaR-5633, left M1/2; K, IPB- HaR-5635, left M1/2. All the teeth are shown as left teeth, the teeth that have been mirrored are indicated by underlined letters. Scale bar: 1 mm.

FIG. 9. — A, Size comparison of Pliopetaurista pliocaenica (Depéret, 1897) M1/2 from Hambach 11C with other published specimens. Black & Kowalski (1974): Pliopetaurista dehneli Sulimski, 1964, Pliopetaurista meini Black & Kowalski 1974, Pliopetaurista cf. pliocaenica (Depéret, 1897); Daxner-HÖck (1975): Pliopetaurista bressana Mein, 1970; Dahlmann (2001): P. pliocaenica, Pliopetaurista raui Dahlmann, 2001; Daxner-HÖck (2004): P. bressana, Pliopetaurista kollmanni Daxner-HÖck, 2004; de Bruijn (1995): P. dehneli Sulimski, 1964; Fejfar & Storch (1990): P. pliocaenica; Gárcia-Alix et al. (2007): P. pliocaenica, P. cf. pliocaenica; Vasileiadou et al.(2012): P. dehneli. In red are our specimens from Hambach 11C, in green the P. pliocaenica specimens and in blue the P. cf. pliocaenica. B, Size comparison of Pliopetaurista pliocaenica m1/2 from Hambach 11C with other published specimens. Black & Kowalski (1974): Pliopetaurista meini; Dahlmann (2001): P. pliocaenica; Daxner-HÖck (1975): Pliopetaurista bressana; Daxner-HÖck (2004): P. bressana, Pliopetaurista kollmanni; de Bruijn (1995): P. dehneli; Colombero & Carnevale (2016): P. pliocaenica; Mansino et al. (2018): P. pliocaenica; MÖrs et al. (1998): P. pliocaenica. In red are our specimens from Hambach 11C, in green the P. pliocaenica specimens and in blue the Pliopetaurista cf. pliocaenica.