Amphicyonidae TROUESSART , 1885

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 : 127

Family Amphicyonidae TROUESSART, 1885

Subfamily Amphicyoninae TROUESSART, 1885

E m e n d e d d i a g n o s i s. Amphicyonidae with robust carnassials (m1/P4), P4 tends to have a reduced protocone and crushing molars (m2, M1 and M2) with a highly developed occlusal surface.

I n c l u d e d t r i b e s. Amphicyonini , Pseudarctini n. tribe, Magericyonini n. tribe.

R e m a r k s. The taxonomy and systematics of the Miocene Amphicyonidae is highly complex (e.g., Kuss 1965, Viranta 1996, Hunt 1998, Ginsburg 1999, Peigné et al. 2008, Morales et al. 2016), and the reasons for this are well known: 1) proliferation of taxa, often with descriptions and definitions based on scarce and sometimes uncharacteristic fossils; 2) a dental morphology displaying very limited variability, associated with a wide size range and the presence of different species in the same locality.

According to Ginsburg (1999), the subfamily Amphicyoninae is represented by 6 genera in Europe: Amphicyon LARTET, 1836 , Cynelos JOURDAN, 1862 , Pseudocyon LARTET, 1851 , Ysengrinia GINSBURG, 1966 , Pseudarctos SCHLOSSER, 1899 and Ictiocyon CRUSAFONT, VILLALTA et TRUYOLS, 1955 . Moreover, he recognized three additional subgenera for Amphicyon : Megamphicyon KUSS, 1965 , Euroamphicyon VIRANTA, 1996 and Heizmannocyon GINSBURG, 1999. These subgenera are considered to have been included in a generic rank in the present research. With the exception of Ysengrinia , which has been transferred to the Thaumastocyoninae ( Heizmann and Kordikova 2000, Morales et al. 2019), the remaining genera of the subfamily, with the addition of the two new genera defined herein, can be classified into three groups, for which we propose the taxonomic rank of a tribe.

Amphicyonini TROUESSART, 1885 , comprising Amphicyon , Cynelos, Paludocyon n. gen., Heizmannocyon, Megamphicyon and Euroamphicyon . This group included the most typical Amphicyoninae ; its molar dentition tends to present an increased surface area, the carnassials are robust and the premolar dentition progressively decreases in size and complexity.

Pseudarctini tribe nov. comprising the genera Pseudarctos and Ictiocyon . As in the previous group, the molars tend to present a larger crushing surface, albeit displaying a different pattern with a greater mesiodistal length in the upper molars and buccolingual length in the lower molars. This is associated with a significant reduction of the carnassial teeth, and loss of the p4 distal accessory cuspid. Dehmicyon n. gen. is provisionally included as a basal form of this tribe.

Magericyonini tribe nov. comprising genus Magericyon and with some doubt also Pseudcyon. Magericyonini represents a new attempt to develop an advanced hypercarnivore adaptation in the Amphicyonidae , while remaining closely related to the amphicyonines, but differing from the Thaumastocyoninae in the slightly reduced crushing dentition and in the morphology of the upper and lower carnassials, which retain an Amphicyonini pattern.