Neosclerocalyptus sp.

Neosclerocalyptus sp.

Referred material: One tooth: PIMUZ A/ V 440; one tooth: PIMUZ A/ V 441; incomplete hemimandible and one osteoderm: PIMUZ A/ V 442; one tooth: PIMUZ A/ V 443; one phalanx: PIMUZ A/ V 445; one phalanx: PIMUZ A/ V 446; one plate of osteoderms from the carapace: PIMUZ A/ V 448; one isolated osteoderm: PIMUZ A/ V 449; caudal tube, two annular rings, 12 plates of osteoderms from the carapace, 47 isolated or fragmented osteoderms: PIMUZ A/ V 450 ( Fig. 9 View Fig ); large plate of osteoderms from the carapace: PIMUZ A/ V 451; fragmented caudal tube: PIMUZ A/ V 452; six plates of osteoderms from the carapace and five isolated osteoderms: PIMUZ A/ V 453; fragmented caudal tube: PIMUZ A/ V 454 ( Fig. 9 View Fig ); one plate of osteoderms from the carapace: PIMUZ A/ V 455 ( Fig. 3 View Fig ); one plate of osteoderms from the carapace: PIMUZ A/ V 456; one isolated osteoderm: PIMUZ A/ V 457; navicular: PIMUZ A/ V 474; navicular: PIMUZ A/ V 475; three plates of osteoderms from the carapace and 37 isolated osteoderms: PIMUZ A/ V 476; 13 plates of osteoderms from the carapace: PIMUZ A/ V 4124; 22 plates of osteoderms from the carapace and 150 isolated osteoderms: PIMUZ A/ V 4135; two plates of osteoderms from the carapace: PIMUZ A/ V 4141; 13 plates of osteoderms from the carapace: PIMUZ A/ V 4251.

Comment: For all specimens of this section, there is no associated complete cranium or carapace. As the diagnoses of each species of Neosclerocalyptus focus mainly on cranial characters or overall carapace characters (Zurita et al., 2009b), it is impossible to distinguish some species on the basis of fragmentary material. Tis is particularly the case for the two oldest species from the Ensenadan, N. pseudornatus and N. ornatus . On the postcranial material, I can add that the differences between N. gouldi , the species presents at the end of the Ensenadan and the Bonaerian, and the two older species, N. pseudornatus and N. ornatus , are particularly weak (Zurita et al., 2008). However, identification at the genus level is consistent and can be supported by the osteoderm pattern. Te set of osteoderms in the remaining specimens follows the genus diagnosis, with dorsal carapace osteoderms exhibiting relatively ‘primitive’ ornamentation close to Propalaehoplophorinae (Zurita et al., 2009b), i.e., the osteoderms are thin and large with a flat central figure always wider than the peripheral figures of the surrounding line, the demarcation between the figures are well delineated by deep sulci (Zurita et al., 2009b). Quantification of the proportions of central and peripheral figures might be useful in the search for diagnostic elements to recognize Neosclerocalyptus species regardless of the cranial remains and the general profile of the dorsal carapace. Specimen PIMUZ A/V 450 also consists of a well-preserved caudal tube. Te latter shows six oval figures on the lateral margins that progressively increase in size toward the most distal part. Te apex of the caudal tube ends in two large terminal dorsolateral figures. Tis general osteoderm organization of the caudal tube is a characteristic of the genus Neosclerocalyptus (Zurita et al., 2009b) , but it does not carry enough differences to distinguish the species. On this basis, also PIMUZ A/V 452 and PIMUZ A/V 454 can be assigned to Neosclerocalyptus . Since the taxonomical revision implies a reassignment at the level of the genus from the initial assignments (Schulthess, 1920; see Additional file 1: Table S1), and because there are no major differences with the osteoderms of the well-identified specimens (i.e., PIMUZ A/V 447), I propose to reassign all specimens from this section including osteoderms or caudal tube to Neosclerocalyptus sp. , pending potential new postcranial diagnostic elements to differentiate the species of Neosclerocalyptus . PIMUZ A/V 440, PIMUZ A/V 441, PIMUZ A/V 443, PIMUZ A/V 445, PIMUZ A/V 446, PIMUZ A/V 474, and PIMUZ A/V 475 correspond to either an isolated tooth or an isolated postcranial bone, preventing a clear taxonomic identification. Tese seven specimens were initially assigned to the species Hoplophorus ornatus , with the exception of PIMUZ A/V 474 which was assigned to Hoplophorus sp. (Schulthess, 1920). However, Hoplophorus ornatus is no longer a valid species and was defined as a synonym of N. ornatus (see Porpino et al., 2010). Terefore, I propose only to follow synonimization at the generic level and maintain an open taxonomy by assigning these seven specimens to Neosclerocalyptus sp. It is noteworthy that all specimens seem to be adults with the exception of PIMUZ A/V 442, which appears to be a young or a newborn specimen. Te incomplete hemimandible bears three incompletely erupted teeth, including mf4, the first tooth to erupt in the lower dentition in glyptodont ( González Ruiz et al., 2020). Te teeth have a conical appearance with a less marked trilobulation than in the adult stage. Te shape of the teeth at such a young ontogenetic stage is reminiscent of the recently published juvenile specimen of an Early Miocene glyptodont ( González Ruiz et al., 2020) and is of particular interest for the study of glyptodont dentition development and the evolution of hypso/hypselodonty within the clade.