María Alejandra Abello

Postcranial Skeleton of the Miocene Marsupial Palaeothentes (Paucituberculata, Palaeothentidae): Paleobiology and Phylogeny

ABSTRACT This contribution presents a morphofunctional analysis of the previously unknown appendicular skeleton of the paucituberculatans Palaeothentes minutus and Palaeothentes lemoinei from the Santa Cruz Formation (late early Miocene, Santa Cruz province, Argentina), performed in order to infer their locomotor behavior. In addition, a cladistic analysis was conducted to explore the phylogenetic information of postcranial features of Palaeothentes in the context of Marsupialia. The results indicate that Palaeothentes would have been an agile cursorial dweller, with leaping ability, similar to the extant paucituberculatan Caenolestes fuliginosus and the didelphid Metachirus nudicaudatus. This mode of locomotion is evidenced mainly by the following features: proximal location of the deltopectoral crest and bicipital tuberosity, reflecting rapid flexion at the 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 broad proximal trochlear crest), denoting a marked stability for flexion and extension; restrictive acetabulum, showing emphasized congruence at the hip joint; lengthened ischium and prominent femoral tubercle and ischial tuberosity, indicating an increased mechanical advantage of the rectus femoris and hamstring muscles; proximally projected greater trochanter, demonstrating a relatively great mechanical advantage of the gluteal 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). A cladistic analysis positions Palaeothentes as the sister taxon to the extant Caenolestes, demonstrating that postcranial features support the monophyly of Paucituberculata.

LOS METATHERIA SUDAMERICANOS DE COMIENZOS DEL NEÓGENO (MIOCENO TEMPRANO, EDAD MAMÍFERO COLHUEHUAPENSE): MICROBIOTHERIA Y POLYDOLOPIMORPHIA

Abstract. SOUTH AMERICAN METATHERIANS FROM THE BEGINING OF THE NEOGENE (EARLY MIOCENE, COLHUEHUAPIAN LAND-MAMMAL AGE). MICROBIOTHERIA AND POLYDOLOPIMORPHIA. We review the taxonomy of two South American orders of Metatheria (Mammalia) of Colhuehuapian age (early Miocene): Microbiotheria and Polydolopimorphia. First, we comment and discuss on the cusp homologies of the upper and lower molars of the Argyrolagoidea (Polydolopimorphia). Second, we offer results of a phylogenetic analysis of the Microbiotheriidae (Microbiotheria). Third, we analyze all Colhuehuapian Microbiotheria and Polydolopimorphia known up to date: Order Microbiotheria, Family Microbiotheriidae: Pachybiotherium acclinum Ameghino, Pachybiotherium sp., Clenia minuscula Ameghino, Oligobiotherium divisum Ameghino, Eomicrobiotherium mykerum sp. nov., Microbiotherium sp., and Microbiotheriidae indet.; Order Polydolopimorphia, Suborder Bonapartheriiformes, Superfamily Argyrolagoidea, Family Argyrolagidae: Proargyrolagus argentinus sp. nov. and Anargyrolagus primus Carlini, Pascual and Goin; Family Patagoniidae: Patagonia peregrina Pascual and Carlini; Argyrolagoidea indet. Finally, we add knowledge on the Colhuehuapian Didelphoidea, describing an indeterminate species referable to this superfamily, and comment on the identity of “ Micro biotherium” gutierrezi Simpson, recognizing the new combination Coona gutierrezi.

The Scelidotheriine Proscelidodon (Xenarthra: Mylodontidae) from the Late Miocene of Maimará (Northwestern Argentina, Jujuy Province)

1Dpto. de Paleontología, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CCT–CONICET–Mendoza, Avda.Ruiz Leal s/n, Parque Gral. San Martín, 5500 Mendoza, Argentina. fpujos@mendoza-conicet.gov.ar 2Institut Français d’Etudes Andines, Casilla 18-1217, Av. Arequipa 4500, Lima 18, Peru. fpujos@yahoo.fr 3CONICET, División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina. acandela@fcnym.unlp.edu.ar, regui@fcnym.unlp.edu.ar 4Facultad de Ingeniería, Universidad Nacional de Salta, Salta, Argentina. claudiagalli@fibertel.com.ar 5CONICET, Instituto de Geología y Minería, Universidad Nacional de Jujuy, 4600 San Salvador de Jujuy, Argentina. bcoira2004@yahoo.com.ar 6Facultad de Ciencias Naturales y Museo de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina. delossreyes@yahoo.com.ar 7Laboratorio de Sistemática y Biología Evolutiva (LASBE), Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, La Plata, Argentina. mabello@ fcnym.unlp.edu.ar AMEGHINIANA 2012 Tomo 00 (0): xxx – xxx ISSN 0002-7014

Evolution of South American Paucituberculata (Metatheria: Marsupialia): adaptive radiation and climate changes at the Eocene- Oligocene boundary

ABSTRACT The Eocene-Oligocene boundary (EOB) marks a period of remodeling in the metatherian faunas of South America. Paucituberculata was one of the groups that successfully diversified as the climate and environment conditions changed, and they became, during the first part of the Neogene, an important component of micromammal assemblages. Among paucituberculatans, the non-pichipilid palaeothentoids (NPP) has been recognized as the clade that diversified most widely in post-EOB times. Here we explore the evolutionary response of the NPP to the climatic-environmental changes around the EOB, by analysing the temporal patterns of disparity, taxonomic diversity and body mass in a phylogenetic context. To asses the magnitude of the NPP radiation comparisons based on these macroevolutionary parameters were done with its sister-group Pichipilidae, and its next closest relative, the Caenolestidae. In all considered parameters, NPP reached values significantly higher than the remaining paucituberculatans clades. From its initial diversification in the middle Eocene, taxonomic diversity increased through time, but it was decoupled from disparity across the EOB, and from the late Oligocene to early Miocene. The Oligocene emerges as the key period in NPP evolution, which is evidenced by a significant and concordant expansion of disparity and taxonomic diversity, suggesting evolution into empty ecospace.

Dracolestes Goin, Candela, Abello, and Oliveira, 2009, is a nomen nudum

FRANCISCO J. GOIN,1 ADRIANA M. CANDELA,1 MARÍA A. ABELLO,2 EDISON V. OLIVEIRA,3 and EDGARDO ORTIZ-JAUREGUIZAR*,2; 1División Paleontologı́a Vertebrados, Facultad de Ciencias Naturales y Museo (UNLP), Paseo del Bosque S/N, B1900FWA La Plata, Argentina, fgoin@fcnym.unlp.edu.ar; acandela@fcnym.unlp.edu.ar; 2LASBE (Laboratorio de Sistemática y Biologı́a Evolutiva), Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque S/N, B1900FWA La Plata, Argentina, mabello@fcnym.unlp.edu.ar; eortiz@fcnym.unlp.edu.ar; 3Laboratório de Paleontologia, Departamento de Geologia, CTG, UFPE, Av. Acadêmico Hélio Ramos s/n, 50740-530, Recife, Brazil, edison.vicente@ufpe.br