Systematic revision and redefinition of the genus Scirrotherium Edmund and Theodor, 1997 (Cingulata, Pampatheriidae): Implications for the origin of pampatheriids and the evolution of the South American lineage including Holmesina

Abstract

The intrageneric relationships of the pampatheriid genus Scirrotherium and its affinities with supposedly related genera, i.e., Kraglievichia and Holmesina, are revised through new comparative morphological descriptions and parsimony phylogenetic analyses. For this work, unpublished material of pampatheriids (numerous osteoderms, one partial skull and a few postcranial bones) from Neogene formations of Colombia was analyzed. The results show that Scirrotherium is paraphyletic if we include all its referred species, i.e., Scirrotherium hondaensis, S. carinatum and S. antelucanus. The species S. carinatum is closer to Kraglievichia paranensis than to S. hondaensis or S. antelucanus, therefore the new name K. carinatum nov. comb. is proposed. The relationship among S. hondaensis and S. antelucanus could not be resolved, so these species should be designated in aphyly. In spite of failing to recover S. hondaensis and S. antelucanus as one single clade, here is preferred to maintain the generic name Scirrotherium in both species based on diagnostic evidence. New emended diagnoses for Scirrotherium, S. hondaensis and Kraglievichia are provided. The genus Holmesina was found to be monophyletic and positioned as the sister clade of Scirrotherium + Kraglievichia. The evolutionary and biogeographic implications of the taxonomic re-arrangements and the new phylogeny are discussed. A possible geographic origin of the family Pampatheriidae and Scirrotherium in low latitudes of South America as early as Early Miocene times is claimed. The immediate South American sister taxon of Holmesina is predicted to be morphologically more similar to Scirrotherium than to Kraglievichia.