Bone microstructure of Quilmesaurus curriei (Theropoda: Abelisauridae): aspecto paleobiológicos inferidos.

IGNACIO A. CERDA; MATHIA BAIANO

Jornada; Reunion Anual de Comunicaciones de la Asociación Paleontológica Argentina; 2017

Despite that paleohistology has proved to be useful to discern several paloebiological traits in non-avian dinosaurs, the bone microstructure of several groups (e.g. abelisaurid theropods) is still poorly documented. Here, we provide a microstructural description of the femur and tibia of the type specimen abelisaurid Quilmesaurus curriei (MPCA-Pv-100). The aim of this work is to determine the ontogenetic stage of the specimen and compare the growth with other abelisaurid theropods (Aucasaurus garridoi MCF-PVPH-236 and Abelisauridae indet. MMCh-PV-69). The compacta is mainly composed of well-vascularized primary bone tissue, which in general exhibits poor organization of the intrinsic fibers (i.e. woven fibered bone). Circumferential canals predominate, albeit longitudinal canals are observed as well. At least six growth marks (annuli and/or lines of arrested growth) are discernible in the tibia, indicating a minimum age of six years. The femur shows a gradual diminution of vascularization density towards the outer cortex, but a true Outer Circumferential Layer is absent on both tibia and femur, indicating that somatic maturity was not reached at time of death. The tibia shows an abrupt change of vascularization in the outermost part of compacta, probably as a result of pathology. The cyclical growth dynamic inferred for Q. curriei MPCA-Pv-100 has been also reported in A. garridoi MCF-PVPH-236 and Abelisauridae indet. MMCh-PV-69, indicating a common growth pattern in abelisaurid theropods. The growth rate of Q. curriei is similar to the reported for A. garridoi, but higher than Abelisauridae indet. MMCh-PV-69, which is congruent with the small size of the last.