A reassessment of the genus Groeberia Patterson, 1952 (Mammalia, Metatheria): functional and phylogenetic implications

ZIMICZ AM; GOIN FJ

JOURNAL OF SYSTEMATIC PALAEONTOLOGY

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2020

1477-2019

With two recognized species, the extinct (Late Eocene) Groeberia is periodically at the centre of systematic disputes. On basis of its best-preserved specimen, we describe in detail the dental and functional morphology of the masticatory apparatus of Groeberia minoprioi, contributing with new anatomical information. The review of its dental anatomy indicates that Groeberia has a tribosphenic molar pattern which confirms its therian affinities.In addition, molars are brachyodont with a slight difference in height between the lingual and labial sides. The dental formula of I2/1; C1/1; P3/1; M4/4 is compatible with the usual metatherian set of three premolars and four molars in the upper dentition, and with the common 'pseudodiprotodont' lower postcanine formula of one premolar (p3) and four molars. The functional morphology of the masticatory apparatus suggests a distinctive incision and chewing phases. The incisive stroke involved the crushing complex of the dentition and contributed to the initial reduction of the food. It was followed by a power stroke with a combination of proal and ectental motion of the jaw. The cladistic analysis resulted in the inclusion of Groeberia among australidelphian metatherians. Groeberia clustered with vombatiform diprotodontians in the consensus tree; however, these affinities requires further testing. Integrating the results on masticatory movements, occlusal tooth wear, infraorbital foramen size, and body mass estimations (90.2 g for G. pattersoni and 216.3 g for G. minoprioi) we suggest an omnivorous diet with a preference for plant material, like that characterizing living potoroids.