Résumé
Among glyptodont cingulates, two major clades are commonly accepted: i) glyptodontines, lacking a caudal tube and with low-latitude earliest records, and ii) hoplophorines, having a caudal tube and high-latitude earliest records in South America. Middle Miocene hoplophorine records, however, are scarce and fragmentary, limiting our understanding of the relationships between Early Miocene forms and their younger counterparts. Here, we describe the most complete Middle Miocene hoplophorine specimens, recovered from the classical locality of Quebrada Honda (ca. 13 Ma), southern Bolivia, and housed at the MNHN-Bol, La Paz. Contrary to previous interpretations suggesting higher diversity at this locality, the available material supports the existence of a single species. This taxon, originally described by Frailey (1986) as Propalaehoplophorus andinus, is here reassigned to Paraeucinepeltus, a previously poorly-known Middle Miocene genus from Patagonia. The study of several exceptionally well-preserved specimens, including MNHN-Bol-V-6480, a complete cranium with cephalic shield and associated postcranial elements (i.e., femur, humerus, and articulated manus), allowed a comprehensive anatomical characterization of the genus, the representatives of which exhibit very unusual and large horn-like structures on the cephalic shield. The inclusion of Pa. andinus in a new phylogenetic analysis highlights the relationships between Early and Late Neogene hoplophorines. Our results reveal a basal dichotomy between two clades, partly differing in the presence of diverging characters of the cephalic shield. The first clade, “horned” glyptodonts, is characterized by cephalic shields lacking ornamentation and bearing a main osteoderm with horn-like structures. These structures show a temporal trend over Neogene times: i) horny insertions in the Early Miocene (Eucinepeltus); ii) large bony protuberances in the Middle Miocene (Paraeucinepeltus); and iii) reduced bony protuberances in the Late Miocene and Pliocene (Eosclerocalyptus). The second clade, represented by cephalic shields composed of ornamented osteoderms and lacking horns, includes genera such as Propalaehoplophorus, Cochlops, and Neosclerocalyptus, among others.