Abstract

GALLIARI, Fernando Carlos. Secuencias de osificación y heterocronía en los miembros de los armadillos Dasypus y Chaetophractus (Mammalia, Xenarthra, Cingulata). Rev. Mus. Argent. Cienc. Nat. [online]. 2018, vol.20, n.1, pp.91-107. ISSN 1853-0400.

Here we described the ossification sequences of the limbs of Dasypus and Chaetophractus, analyzed them in a phylogenetic framework in order to identify heterochronic events. We used 58 specimens of D. hybridus, C. vellerosus, and C. villosus, and recorded ossification centers of the fore and hind limbs. In addition, we performed a phylogenetic mapping using event-pair cracking to identify sinapomorphic events (movements of ossification events in a sequence along each branch of a phylogeny). To perform this analysis, we included several non-xenarthran extant mammal taxa. The Cingulata clade is characterized by one delayed event (unciform ossification), and three events that moved to earlier positions (calcaneus, ectocuneiform, and cuboid). In Dasypus, 14 autapomorphic events were recorded, standing out the earlier ossification of the distal phalanges. In Chaetophractus six autapomorphic events are recorded, and the distal phalanges also ossified in earlier stages. In the carpal region the largest elements would ossify earlier, while smaller ones would do so in later stages (e.g., pisiform and magnum in Chaetophractus). The pattern is similar in the tarsal and phalangeal regions. In Dasypus the fifth manual digit is highly reduced and ossifies rather late in the ontogeny. Some events in other taxa follow the same pattern (e.g., the fibula of Equus). The autopodium of mammals could be divided in compartments, and the ossification sequence would correlate with size within each compartment, starting the ossification in larger elements.

Keywords : Ossification centers; Skeletogenesis; Event-pair cracking; Xenarthran mammals.