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

ZIMICZ, ANA NATALIA; GOIN, FRANCISCO JAVIER

JOURNAL OF SYSTEMATIC PALAEONTOLOGY

CAMBRIDGE UNIV PRESS

Año: 2020 p. 1 - 18

1477-2019

With two recognized species, the extinct (late Eocene) Groeberia is periodically at the centre of systematic disputes. Onthe basis of its best-preserved specimen, we describe in detail the dental and functional morphology of the masticatoryapparatus of Groeberia minoprioi. A review of its dental anatomy indicates that Groeberia has a tribosphenic molarpattern which confirms its therian affinities. Its dental formula of I2/1; C1/1; P3/1; M4/4 is compatible with the usualmetatherian 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. A cladistic analysis resulted in the inclusion ofGroeberia among australidelphian metatherians, clustering with vombatiform diprotodontians in the strict consensus tree;however, these affinities require further testing. The functional morphology of the masticatory apparatus suggestsdistinct incisive and chewing phases. The incisive stroke was followed by a power stroke with a combination of proaland ectental motion of the jaw. Integrating the results of masticatory movements, occlusal tooth wear, infraorbitalforamen size, and body mass estimations (90.2 g for G. pattersoni and 216.3 g for G. minoprioi), we suggest anomnivorous diet with a preference for plant material, like that characterizing living potoroids.