Postcranial skeleton of the Miocene marsupial Palaeothentes (Paucituberculata, Palaeothentidae): paleobiology and phylogeny

M. A. ABELLO Y A. M. CANDELA

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Año: 2010 p. 1515 - 1527

0272-4634

This contribution presents a morphofunctional analysis of the previously unknown apendicular skeleton of the Paucituberculata Palaeothentes minutus and Palaeothentes lemonei coming from the Santa Cruz Formation (late early Miocene, Santa Cruz province, Argentina), performed in order to infer their locomotor behavior. In addition, to explore the phylogenetic information of postcranial features of Palaeothentes in the context of Marsupialia a cladistic analysis was conducted. Our results indicate that, as living Paucituberculata Caenolestes fuliginosus and the Didelphidae Metachirus nudicaudatus, Palaeothentes would have been an agile cursorial dweller, with leaping ability. This mode of locomotion is evidenced mainly by the following features: proximal location of the deltopectoral crest and bicipital tuberosity, expressing fast flexions at gleno-humeral and elbow joints respectively; shape of the humero-ulnar and humero-radial joints (deep and high humeral trochlea, deep olecranon fossa, deep trochlear notch, mediolaterally spread proximal trochlear crest), denoting a marked stability for flexion and extension; restrictive acetabulum, showing emphasized congruence at the hip joint; lengthened ischium, prominent femoral tubercule and ischiatic tuberosity, representing an elevated mechanical advantage of the rectus femoris and hamstring muscles; proximally projected greater trochanter, demonstrating a relatively great mechanical advantage of the glutei muscles, and configuration of the upper ankle, lower ankle and transverse tarsal joints, indicative of restrictive rotational movements (right angle between the medial and lateral astragalotibial facets, distal and proximal calcaneo-cuboid facet halves forming a right angle). Cladistic analysis shows that Palaeothentes is phylogenetically close to living Caenolestes, demonstrating that postcranial features are informative in supporting the monophyly of the Paucituberculata clade.