Dehmicyon, Morales & Fejfar & Heizmann & Wagner & Valenciano & Abella, 2021

Morales, Jorge, Fejfar, Oldřich, Heizmann, Elmar, Wagner, Jan, Valenciano, Alberto & Abella, Juan, 2021, The Amphicyoninae (Amphicyonidae, Carnivora, Mammalia) Of The Early Miocene From Tuchořice, The Czech Republic, Fossil Imprint 77 (1), pp. 126-144 : 138-141

Genus Dehmicyon n. gen.

T y p e s p e c i e s. Amphicyon schlosseri DEHM, 1950

(Wintershof- West, Germany; early Miocene, MN 3).

E t y m o l o g y. In honour of Dr. Richard Dehm.

D i a g n o s i s. Pseudarctini with robust mandible, small mesial premolars (p1–p3), p4 unicuspidated. High m1 trigonid with strong metaconid; short and narrow talonid. m2 remaining long compared with m1. P4 robust with strong protocone. Slender M1 with subtriangular occlusal shape. M2 small compared to M1.

Dehmicyon schlosseri ( DEHM, 1950)

Text-figs 7 , 8

1950 Amphicyon schlosseri n. sp.; Dehm, p. 20, figs 9–17.

1965 Cynelos rugosidens schlosseri (DEHM) 1950 ; Kuss, p. 63– 66.

1981? Cynelos schlosseri (Dehm), 1951 ; Ginsburg et al., p. 185, fig. 2.

1989 Cynelos schlosseri ; Ginsburg, p. 107.

1996 Cynelos schlosseri ( Dehm, 1950) ; Viranta, p. 22, fig. 7.

1999 Cynelos schlosseri ( DEHM, 1950) ; Ginsburg, p. 116.

2003 Cynelos schlosseri ; Peigné and Heizmann, p. 14.

2008 C [ynelos] schlosseri ; Peigné et al., p. 954.

2015 Cynelos schlosseri ; Hunt and Stepleton, p. 4

H o l o t y p e. BSP 1937 II 13562, mandible and maxilla

( Dehm 1950: figs 9–11). See Kuss (1965: 63).

T y p e l o c a l i t y. Wintershof-West, Germany.

A g e. Early Miocene, MN 3.

E m e n d e d d i a g n o s i s. Same as genus.

R e m a r k s. Dehmicyon schlosseri presents an interesting combination of morphological features, which enable it to be differentiated from Cynelos lemanensis ( POMEL, 1846) and from the Ictiocyon - Pseudarctos group. Their separation from C. lemanensis and related species is unequivocal, as evidenced by Peigné and Heizmann (2003), in particular due to the poor development of the crushing molars, which suggests a more primitive morphological stage than the Cynelos - Amphicyon group species, typical representatives of the Amphicyoninae clade. Together with the Ictiocyon - Pseudarctos group, it shares the robustness of the jaw and the morphology of the lower p4 lacking a distal accessory cuspid (residual in some specimens). Other morphological characters that it shares, in particular with Ictiocyon , involve the strong development of the buccal wall of the M 1 in relation to the lingual area, the large size of the buccal cingulum and the robust development of the styles. However, in Ictiocyon the M1 is wide, especially on its occlusal surface, similar to that of the other molars ( Crusafont et al. 1955). This tendency towards a larger crushing surface in the molar dentition is shared with the Cynelos - Amphicyon group, but in the Ictiocyon - Pseudarctos group the carnassials are significantly reduced (P4/m1), whereas in Cynelos and Amphicyon they tend to show an increase in size. In the latter genus, the upper molars maintain a strong buccal-lingual development, while in Ictiocyon they tend to present a sub-square occlusal shape.

Ginsburg (1992) reviewed the species included in Pseudarctos , rejecting the proposal of Kuss (1965) that supported the existence of an anagenetic line formed by a single species Pseudarctos bavaricus with different temporal subespecies. The French author, proposing the existence of two genera; Ictiocyon CRUSAFONT, VILLALTA et TRUYOLS, 1955 new rank and Pseudarctos SCHLOSSER, 1899 , but without accepting the validity of Ictiocyon dehmi the type species of Ictiocyon , which he considered as synonymous with Ictiocyon socialis. However, Ictiocyon dehmi shows more derived characteristics than Ictiocyon socialis. This is seen especially in the greater robustness of the premolars and the morphology of the m1–m2 talonid, which are wider and more developed than the trigonid. This tendency to increase the surface of the talonid relative to the trigonid became a significant feature in Pseudarctos . The morphology of m1 suggest that the mandible of Wintersoft-West BSP 1937 II 12301 determined as Ictiocyon socialis by Dehm (1950) could be closer to Ictiocyon dehmi than to I. socialis, so we suggest it be reclassified as Ictiocyon cf. dehmi.

Dehmicyon can be interpreted as a similar form to Ictiocyon genus with which it appears to share derived characters such as mandibular robustness and loss of the posterior accessory cuspid on the p4; other features shared by both groups can be considered as primitive; e.g., the strong development of the styles and the buccal cingulum and the narrow morphology of the lingual area of the M1 or the small size of the second and third molars. Unfortunately, the absence of upper dentition in Ictiocyon socialis prevents direct comparison with the new genus. However, the morphology of the lower dentition supports the proposal that D. schlosseri is closer to I. socialis than I. dehmi.

D. schlosseri has simultaneously a less specialized dental morphology than I. socialis (in particular seen in the reduced robustness of the m1) and greater size of the m2 with compared to the m1 ( Text-fig. 8 ). These differences are sufficiently important to separate both species at a generic level. Dehmicyon schlosseri can be interpreted as a basal form of Pseudarctini , already far removed from the primitive Amphicyonini represented by Cynelos species.

Figures

Text-fig. 7. Dehmicyon n. gen. schlosseri (DEHM, 1950), from Wintershof-West, Germany. a: BSP 13562, mandible (holotype), a1 – right hemimandible in buccal view, a2 – occlusal view, a3 – left p4–m2 in occlusal view; b: BSP 12365, left maxilla fragment with M1 in occlusal view; c: BSP 13562, left maxilla fragment with P3 broken, P4–M2 and M3 alveolus (holotype) in occlusal view; d: BSP 12343 left maxilla fragment with P4, alveolus for M1, M2 and M3 alveolus in occlusal view.

Text-fig. 8. Bivariate diagram of length and width of the lower dentition (m1 and m2) of Pseudarctos, Ictiocyon and Dehmicyon species. a: m2; b: m1; c: length m1 and m2. Data from Schlosser (1904), Helbing (1937), Thenius (1949), Dehm (1950), Crusafont et al. (1950), Ginsburg (1992). Abbreviations: L – length; W – width; Ba – Baigneaux; LRM – Pellecahus.