Nomenclatural confusion has existed within the Mylodontinae for several genera, and has resulted in the supposition that Paramylodon of North America is synonymous with Glossotherium of South America. A taxonomic revision of crania for Glossotherium and Paramylodon upholds their separation as distinct genera and provides a list of diagnostic characters that have been lacking. Assessment was made using principal components analysis for suites of cranial and mandibular measurements, evaluation of ratios and measurement distribution, and by examining qualitative characters. Results show the greatest characterization for the skull comes from differences relating to cranial length versus width, whereas the mandible is predominantly distinguished by qualitative characters of the predental spout. Examination of the Pliocene species Glossotherium chapadmalense from South America shows a combination of characters indicative of each genus, but exhibits more with Glossotherium and is tentatively retained under that genus. The mix of characters indicates that G. chapadmalense is the likely ancestor to Paramylodon, although when and where the transition took place is still unclear. During the evolutionary transition, Paramylodon crania emphasized an increase in length of the palate, whereas those of Glossotherium emphasized an increase in cranial width.

Recent discovery of a supernumerary dental anomaly in two‐toed sloths led to an extensive review of extant sloth specimens to look for additional anomalies. In total, 881 museum specimens were examined. These revealed two primary types of anomalies, hyperdontia (extra teeth) and anodontia (loss of teeth), occurring at a rate of 2.4% (n = 21). Two‐toed sloths, Choloepus, were more likely to have hyperdontia in the anterior dentition, whereas three‐toed sloths, Bradypus, experienced anodontia more frequently with the upper caniniforms. Both genera experienced both anomalies. The majority affected the upper dentition, with only three specimens exhibiting mandibular anomalies. Beyond the patterns of tooth positioning, all anomalies were random with respect to age, sex and geography. A few specimens not counted in the initial assessment expressed incomplete anodontia, indicating that the loss occurred postnatally and was not an embryological anomaly. For Bradypus, the findings provide new support for the hypothesis that the taxon represents a neotenic lineage and opens new possibilities about its relationship to the extinct ground sloths with a suggested rooting above that of the basal position it typically occupies for Folivora.

Haitian species of the extinct ground sloth genus Neocnus (Mammalia: Pilosa: Megalonychidae) have previously been hypothesized to have a much reduced jugal bone and a correspondingly reduced masseter musculature but a paucity of specimens has prevented further investigation of this hypothesis. Recent discovery of jugal bones belonging to Haitian specimens of Neocnus within the University of Florida Museum collections enables the element to be more accurately described. The discovery also makes it possible to explore mastication in these sloths. Osteological characters related to feeding were examined, along with comparative estimations of bite force with the extant tree sloths, Bradypus and Choloepus, and their known dietary habits as a means to infer aspects of the paleodiet of Neocnus. There is a significant difference in moment arm calculations for m. masseter between predicted and actual jugals, but the overall significance for bite force is lost and hampered by small sample size. Neocnus demonstrates a variety of characters that are similar to those of Bradypus and not to Choloepus, which is a close phylogenetic relative. The masticatory musculature of Neocnus enabled a chewing cycle emphasizing a grinding combination of mesiodistal and linguobuccal movements of the molariform dentition. The orientations of m. masseter and m. temporalis are estimated to produce relatively high bite force ratios that imply a masticatory system with stronger versus faster components. Because of the similarity of bite forces and jaw mechanics to those of Bradypus, in addition to a number of osteological adaptations indicative of herbivorous grazers (elevated mandibular condyle, large and complex masseter, and robust angular process), the Haitian forms of Neocnus are considered to have been selective feeders with a folivorous diet.

The late Pleistocene mylodontine sloth Glossotherium wegneri (Spillmann, 1931) (Interandean ­region, Ecuador) has been assigned to Glossotherium Owen, 1839 and Oreomylodon Hoffstetter, 1949 (the latter ranked as a subgenus or genus), and synonymized with G. robustum (Owen, 1842). However, the phylogenetic and comparative analyses conducted here, which include previously undescribed remains, strongly suggest specific distinction for G. wegneri and that there is little, if any, support for generic or subgeneric distinction for Oreomylodon. Among the notable features of this species are the ­presence of an internasal element, marked expansion of the rostrum anteriorly, and dorsoventrally and the palatal region transversely, increased separation of the caniniform tooth from the anterior edge of maxilla, increased relative braincase width, relatively enlarged hypoglossal foramen, and greatly elongated zygomatic process of the squamosal. The resulting single MPT recovered a monophyletic Glossotherium, with the following phylogenetic arrangement of the species of this genus (G. robustum + ((G. wegneri + G. tropicorum Hoffstetter, 1952) + (G. phoenesis Cartelle, De Iuliis, Boscaini & Pujos, 2019 + G. tarijense Ameghino, 1902))).

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