Description of the axial skeleton of three genera of sigmontines: Eligmodontia, Phyllotis and Andinomys (Rodentia: Cricetidae: Sigmodontinae).

CARRIZO, L. V.; DÍAZ. M. M.

Mendoza

Jornada; IMC 10th International Mammalogical Congress; 2009

Institute for Aridlands Research IADIZA; Biodiversity Research Group - GIB;Center for Science & Technology Mendoza – CCT, Sociedad Argentina para el Estudio de los Mamíferos – SAREM, National Council of Science and Technology – CONICET.

Most of the investigations about sigmodontine rodents, whose objectives were the resolution of systematic and phylogenetic problems, have included only cranial and dental morphology, without considering postcranial information in their analyses. For this reason, we have started the study of postcranial skeleton, mainly in species of filotines, a tribe that is quite well studied but that still needs revisions since several phylogenetic relationships are still conflictive. Here we present a detailed description of the axial skeleton of three genera of sigmodontine, from different habitats and body size. These are Eligmodontia, Phyllotis and Andinomys (the last considered a filotine by some authors as well as inserta sedis by others). We established differences and similarities in appearance, size, surface, and orientation of the skeletal structures. Andinomys showed the greatest differences both in the degree of development as in variation of the vertebral structures. We mention the characters with most morphological variability in Andinomys: dorsal tubercle of atlas well developed (less developed in Phyllotis, absent in Eligmodontia); spinous process of axis posteriorly extended (no extended in Phyllotis and Eligmodontia); spinous processes of the cervical vertebrae well developed (less developed in Phyllotis, absent in Eligmodontia); cranio-caudal length of hemal arch of thoracic vertebrae proportionally larger than in Phyllotis and Eligmodontia; transverse processes of lumbar vertebrae cranio-caudally expanded (less expanded in Phyllotis and Eligmodontia). These differences reflect possible functional implications associated to diet and postural patterns, since the more evident variations were observed in those skeletal structures where muscles involved in head and flexion movements of the body, are originated and/or inserted.