The relationship between humerus shape and the modes of exploring substrate among extinct and extant Pilosa (especially anteaters and ground sloths) were investigated here. We used geometric morphometrics and discriminant analyses to relate morphological patterns and their possible ecological categories. Our results suggest that plesiomorphic taxa such as Nothrotheriidae, most Megalonychidae and basal Megatheriidae tend to have more slender humerus, associated to generalist habitus (climbing, swimming and digging activities), and while Mylodontidae developed specialized digging habitus. Additionally, we inferred ground sloths which inhabited the Brazilian territory during the Quaternary likely occupied at least four different niches. Mammals display morphofunctional adaptations on the limbs which are reflected on their modes of substrate exploration. Herein, we analyzed the humerus morphology of ground sloths and anteaters. Our results suggest that most of the Pleistocene Mylodonts were fossorial taxa, while most of the Santacrucian sloths plus extant anteaters were semiarboreal or semiaquatic taxa. The Pleistocene Megatheriidae should be ambulatory. Mammals display morphofunctional adaptations on the limbs which are reflected on their modes of substrate exploration. Herein, we analyzed the humerus morphology of ground sloths and anteaters. Our results suggest that most of the Pleistocene Mylodonts were fossorial taxa, while most of the Santacrucian sloths plus extant anteaters were semi‐arboreal or semi‐aquatic taxa. The Pleistocene Megatheriidae should be ambulatory
Here, we review population genetic, phylogeographic, and phylogenetic studies on xenarthrans and show how this information fits in current discussions about patterns of diversification within the Neotropics. Specifically, we focus on how the genetic diversity of xenarthrans has been shaped by important historical processes such as Andean uplift, the Great American Biotic Interchange, and fluctuating linkages between the Amazon and Atlantic forests. We also describe latitudinal patterns of differentiation within the Atlantic forest and discuss how these might have been generated. Even with the modest amount of information currently available, our comparative analyses indicate 3 things: the Andes may have promoted events of intraspecific divergence for at least 2 xenarthran species; the biogeographic history of the Neotropical rain forests influenced the divergence of clades in sloths; and inter- and intra-specific genetic patterns reveal a very high diversity in xenarthrans, probably higher than currently recognized from morphological data. Finally, we highlight Xenarthra as an appropriate model for investigating biogeographic patterns in the Neotropics and also point to additional directions to be taken in future studies of this unique mammal group. Revisamos los estudios realizados sobre genética de poblaciones, filogeografía y filogenia de los Xenarthra y mostramos como la información generada se ajusta a la discusión actual acerca de los patrones de diversificación en el Neotrópico. Enfocamos nuestro análisis en la influencia de 4 eventos pasados importantes relacionados con la dinámica del paisaje Neotropical y la diversificación de la fauna, sobre la diversidad genética de los Xenarthra; estos son el levantamiento de los Andes, el gran intercambio de fauna del Pleistoceno, la relación entre el bosque Amazónico y el bosque Atlántico y los patrones latitudinales de diferenciación en el bosque Atlántico. Aunque la información disponible aún es escasa, nuestro análisis comparativo indica que los Andes pudieron haber promovido eventos de diversificación intraespecífica, al menos en 2 especies de Xenarthra; que la historia biogeográfica del bosque húmedo Neotropical tuvo influencia sobre la divergencia de linajes de perezosos; y que los patrones genéticos intra e interespecíficos revelan una gran diversidad en Xenarthra, probablemente mayor que la actualmente reconocida con datos morfológicos. Finalmente, resaltamos a los Xenarthra como un modelo apropiado para investigar patrones biogeográficos en el Neotrópico y sugerimos líneas adicionales a considerarse en futuros estudios sobre este grupo único de mamíferos.
The Mylodontidae Scelidotheriinae (Mammalia, Xenarthra, Tardigrada) are a diversified clade of South American fossil ground sloths, with a wide geographic distribution, especially in high and middle latitudes. According to the last revision, the Quaternary diversity includes the genera Scelidotherium, Catonyx, and Valgipes. The clade Scelidotheriinae is well represented in the Pleistocene of the Tarija-Padcaya basin, and the first mention of these ground sloths correspond to the middle of the XIX Century. Since then, several species (i.e., Scelidotherium tarijensis, Scelidodon tarijensis, Scelidotherium capellini) have been reported as inhabiting the Tarija-Padcaya basin during the Pleistocene. Despite the abundance of fossil records of Scelidotheriinae in this area, no modern taxonomic revisions are available. In consequence, in this contribution a revision of the remains assigned to Scelidotheriinae from the Tarija-Padcaya basin is accomplished, and some biostratigraphic and geographic implications are discussed. Our results show that one single species (Catonyx tarijensis) can be recognized in the studied area, whereas a supposed smaller one (Scelidotherium patrium) actually corresponds to juvenile specimens of C. tarijensis.
AbstractXenarthra is an endemic South American lineage of mammals, probably the sister clade of the other placental mammals. The oldest records of Xenarthra are from the latest Paleocene, although its current diversity is much lower than that recorded in some intervals of the Cenozoic Era. A new Neogene Xenarthra (Pilosa and Cingulata) assemblage from two localities of the Argentine Eastern Puna (Calahoyo and Casira) is described. The newly recorded taxa—Cingulata, Dasypodidae, Eutatini: Stenotatus sp. indet. and Eutatini indet., Euphractini: Macrochorobates scalabrinii (Moreno and Mercerat, 1891), and Tardigrada, Mylodontinae: cf. Simomylodon sp. indet. and Simomylodon cf. S. uccasamamensis Saint-André et al., 2010—and those already published from Calahoyo—Cingulata: Macrochorobates chapadmalensis (Ameghino, 1908), Eosclerocalyptus sp. indet., and Tardigrada, Megatheriidae: Pyramiodontherium bergi (Moreno and Mercerat, 1891)—suggest a middle–late Miocene age for the fossil-bearing levels. In Calahoyo, the presence of Stenotatus sp. indet., in addition to some rodents currently under study in the lower levels, suggest a closer similarity with the palaeofauna of Cerdas (southern Bolivia), probably involving the last part of the Miocene Climatic Optimum. The Xenarthra recorded in the middle and upper levels of Calahoyo and Casira suggest a late Miocene–Pliocene age. A comparative analysis between Calahoyo and Casira highlights the absence of Cingulata in the latter and a high diversity in the former. This situation probably indicates different paleoenvironmental conditions. Finally, we present the first certain record of the genus Simomylodon Saint-André et al., 2010 in Argentina, which includes the oldest record of dermal ossicles for sloths in South America.
ABSTRACT Increased field collecting over the last few years, combined with the examination of historical collections in Uruguay, has resulted in the discovery of a great number of specimens of the Scelidotheriinae, indicating that this subfamily is better represented in Uruguay's Pleistocene fauna than previously thought. Because much of this new material is diagnostic, in this work we provide a fuller description of some specimens (a skull with associated mandible and the manus, another almost-complete skull, and two partial dentaries) from the late Pleistocene of Uruguay for which only preliminary descriptions have been previously made, with tentatively assignments to Catonyx. A discriminant analysis was performed using 48 adult specimens including Scelidotherium, Catonyx, and Proscelidodon and supports the contention that Catonyx is a valid genus and the inclusion of these new specimens within this genus. This analysis also allows us to identify those cranial characters that better differentiate the ge...
The tongue of anteaters (Xenarthra, Pilosa, Vermilingua) is a highly specialized for myrmecophagy. Here, we describe the topography and histology of the tongue, and compare it to that of other xenarthrans and other myrmecophagous eutherian mammals. The tongue of Vermilingua is long and slender, with an apical protuberance, which differs between Myrmecophagidae and Cyclopes didactylus. In the former, the rostral region is conical, and in the latter, it is dorsoventrally compressed, as observed in sloths. The tongue of Vermilingua has filiform and circumvallate papillae on the surface; foliate and fungiform papillae are absent. The filiform papillae of Myrmecophaga tridactyla are simple all over the tongue, differing from Tamandua tetradactyla and Cyclopes didactylus, which present composed filiform papillae in the rostral and middle regions. Histologically, the tongue has a peculiar organization of muscular and neurovascular tissues, differing from the usual mammalian pattern. However, the tongue structure is less divergent in Cyclopes. The presence of two circumvallate papillae is common to the three major clades of Xenarthra (Cingulata, Folivora and Vermilingua). In each group, the tongue may reflect functional features related to myrmecophagous (anteaters and some armadillos), omnivorous (remaining armadillos) and folivorous (sloths) feeding habits. The similarities between the tongues of Vermiligua and other non‐xenarthran eutherian myrmecophagous mammals are somewhat general and, under close inspection, superficial, being an example of different lineages achieving the same morphofunctional adaptations through distinct evolutionary pathways. The peculiar tongue of anteaters was investigated with gross anatomical observations, scanning electron microscopy and histological techniques. The morphology observed in the tongues of anteaters reflects the adaptive specialization of the organ for myrmecophagy. Comparing it with that of other xenarthrans, it is possible to infer some aspects about the evolution of the organ in the group. Picture of Tamandua tetradactyla by Karina Molina.
Remains of peltephilid cingulates from the late Oligocene (Deseadan, South American Land Mammal Age) of Salla, Bolivia, are described and organized as two morphs, the larger referred to a new taxon, Ronwolffia pacifica, and the smaller as indeterminate. A fairly well-preserved cranium serves as the holotype for Ronwolffia pacifica, with referred material consisting of jaws, osteoderms, and a partial pelvis. Ronwolffia is recognized by a combination of characters, some of which are regarded as general placental traits compared to some distinctive features of the well-known Santacrucian species of Peltephilus. Such generalized traits in Ronwolffia include tendencies for eight (rather than seven) mandibular teeth, unfused mandibular symphysis, incompletely ossified auditory bulla, and a low occiput and cranial vault. Like those of other peltephilids, the temporomandibular joint (TMJ) is low, but, unlike typical armadillos and the genotypic Peltephilus strepens, the glenoid fossa forms part of the wall of the external acoustic porus. Similar crowding of the TMJ and porus is noted in Peltephilus pumilus and Peltephilus ferox. Terminology related to the classification of xenarthrans is considered. Dasypodoidea Gray, 1821 is herein used for the crown clade that includes armadillos and glyptodonts, with Cingulata designating the total clade (crown + stem); that is, taxa more closely related to Dasypus than to any pilosan taxon (sloth or anteater). It is also desirable to clearly discriminate between the crown and total clade Xenarthra; thus Xenarthra is herein used exclusively for the crown, with the biogeographically inspired name, Americatheria, being proposed for the total clade; that is, taxa more closely related to Dasypus than to any members of Afrotheria or Boreotheria.
A set of lesions are re-described and new pathological findings in foot bones of Panochthus sp. (Xenarthra, Cingulata) are presented. The material reexamined in fact presents enthesiophytes instead of osteoartrithis, as previously interpreted. Furthermore, Calcium Pyrophosphate Deposition Disease (CPPD) was observed, a lesion absent in previous report. CPPD also was found in another set of foot bones and it was associated with a congenital fusion of two sesamoids. The material studied were collected in two natural tank deposits, one in Paraiba (material reexamined) and other in Rio Grande do Norte (new pathological findings) State.
Arthritic lesions have been frequently diagnosed in the fossil record, with spondyloarthropathy (a type of erosive and panmammalian arthritis) being one of the most common types described to date for mammals, though not restricted to this group. Here, we identify spondyloarthropathy in fossil bones from the late Pleistocene in Brazil assignable to a large glyptodont individual. Bone erosions in the peripheral joints (viz., the ulna, radius, left femur and tibiae-fibulae) associated with osteosclerosis allow the diagnosis of spondyloarthropathy. The presence of osteophytes in seven bones of the forelimbs (viz., the ulna and radius) and hind limbs (viz., the tibiae-fibulae, left femur and patellae) and a subchondral cyst in one element (viz., the left femur) indicate secondary osteoarthritis. A calcified deposition on the articular surface of the left patella indicates the presence of calcium pyrophosphate deposition disease, which, like the observed osteoarthritic alterations, likely represents a complication of spondyloarthropathy. This is the first report of spondyloarthropathy for xenarthrans.