Glyptodonts were giant (some of them up to ~2400 kg), heavily armoured relatives of living armadillos, which became extinct during the Late Pleistocene/early Holocene alongside much of the South American megafauna. Although glyptodonts were an important component of Cenozoic South American faunas, their early evolution and phylogenetic affinities within the order Cingulata (armoured New World placental mammals) remain controversial. In this study, we used hybridization enrichment and high‐throughput sequencing to obtain a partial mitochondrial genome from Doedicurus sp., the largest (1.5 m tall, and 4 m long) and one of the last surviving glyptodonts. Our molecular phylogenetic analyses revealed that glyptodonts fall within the diversity of living armadillos. Reanalysis of morphological data using a molecular ‘backbone constraint’ revealed several morphological characters that supported a close relationship between glyptodonts and the tiny extant fairy armadillos (Chlamyphorinae). This is surprising as these taxa are among the most derived cingulates: glyptodonts were generally large‐bodied and heavily armoured, while the fairy armadillos are tiny (~9–17 cm) and adapted for burrowing. Calibration of our phylogeny with the first appearance of glyptodonts in the Eocene resulted in a more precise timeline for xenarthran evolution. The osteological novelties of glyptodonts and their specialization for grazing appear to have evolved rapidly during the Late Eocene to Early Miocene, coincident with global temperature decreases and a shift from wet closed forest towards drier open woodland and grassland across much of South America. This environmental change may have driven the evolution of glyptodonts, culminating in the bizarre giant forms of the Pleistocene.
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.
Most of the mammalian diversity is known only from fossils, and only a few of these fossils are well preserved or abundant. This undersampling poses serious problems for understanding mammalian phenotypic evolution under a quantitative genetics framework, since this framework requires estimation of a group's additive genetic variance-covariance matrix (G matrix), which is impossible, and estimating a phenotypic variance-covariance matrix (P matrix) requires larger sample sizes than what is often available for extinct species. One alternative is to use Gor P matrices from extant taxa as surrogates for the extinct ones. Although there are reasons to believe this approach is usually safe, it has not been fully explored. By thoroughly determining the extant and some extinct Xenarthra (Mammalia) cranium P matrices, this study aims to explore the feasibility of using extant G or P matrices as surrogates for the extinct ones and to provide guidelines regarding the reliability of this strategy and the necessary sample sizes. Variance-covariance and correlation P matrices for 35 cranium traits from 16 xenarthran genera (12 extant and 4 extinct) were estimated and compared between genera. Results show xenarthran P-matrix structures are usually very similar if sample sizes are reasonable. This study and others developed with extant therian mammals suggest, in general, that using extant G or P matrices as an approximation to extinct ones is a valid approach. Nevertheless, the accuracy of this approach depends on sample size, selected traits, and the type of matrix being considered.
A combination of historical, functional, and biomechanical constraints has shaped the masticatory apparatus of fossil and extant xenarthrans. Among the more notable features are the teeth: hypselodont; commonly reduced in size, complexity, and number; separated by short diastema; and composed of osteodentine. Enamel is absent, as are the cuspal patterns of other mammals. A comprehensive revision of teeth and other features of the masticatory apparatus of xenarthrans reveals that previous generalizations underestimate the morphological diversity and adaptive possibilities developed within the clade. The great diversity of forms suggests several such possibilities ranging from specialized myrmecophagous species to carrion feeders or predators among animalivores; selective browsers to bulk grazers among herbivores; and omnivores. In some cases xenarthrans represent less extreme versions of patterns developed in other major clades of mammals (marsupials, afrotheres, euarchontoglires, and laurasiatheres) clearly predetermined by a tribosphenic dental morphology, whereas in others they represent unique novelties indicative of particular biological roles. The combination of tooth features that characterize xenarthrans might be seen as the key innovation for the ecologic diversity developed at least since the Oligocene, breaking the mold of the tribosphenic condition that constrained the evolution of the other major clades of mammals.
Environmental temperature, rainfall, vegetation structure, soil composition and land use were recognized as relevant factors limiting the distribution of armadillos. The aim of this study was to identify environmental and spatial factors influencing the geographical distribution of the most widespread armadillos occurring in Argentina ( , and ), through the most simple and accurate explanatory modeling. General linear models (GLMs), partitioning analyses of variance and hierarchical partitioning analyses were applied to estimate the species-environment relationships. Climatic variables were recognized as the most relevant factors influencing the three species distribution, consistent with that expected from the hierarchical structure theory in ecological systems. Optimal conditions were mainly arranged in a longitudinal geographic gradient for species and in a latitudinal-longitudinal gradient for . The optimal habitat identified for , larger than previously documented, was characterized by warm, rainy summers and moderately cold, dry winters. The distribution of was mainly influenced by temperate conditions of temperature and isothermality, scarcity of rainfall with high seasonality and low aridity conditions, and prevalence of sandy soils. Optimal habitat of was affected by low temperatures with high seasonality, scarcity of rainfall with aridity conditions and sandy soils.
This report continues our monographic analysis of mammalian diversity and Matses ethnomammalogy in the Yavari-Ucayali interfluvial region of northeastern Peru. Based primarily on specimens collected in the region from 1926 to 2003, interviews with Matses hunters, and published sight surveys of large mammals, we document the local occurrence of 33 species of xenarthrans, carnivores, perissodactyls, artiodactyls (including cetaceans), and sirenians. All of the species in these groups, with the exception of the Amazonian manatee (Trichechus inunguis), are recognized and named by the Matses, from whom we recorded extensive accounts of mammalian natural history. The local xenarthran fauna consists of nine species (Cabassous unicinctus, Priodontes maximus, Dasypus novemcinctus, D. pastasae, Bradypus variegatus, Choloepus hoffmanni, Cyclopes didactylus, Myrmecophaga tridactyla, Tamandua tetradactyla), all of which are represented by examined specimens. Only two xenarthrans (D. pastasae and C. hoffmanni) are primary game species for the Matses, who are familiar with many aspects of their biology that were previously unrecorded in the scientific literature. However, Matses interviews also provide important new information about the behavior of D. novemcinctus (a secondary game species) and M. tridactyla, neither of which has previously been studied in rainforested environments. The local carnivore fauna consists of 16 species (Atelocynus microtis, Speothos venaticus, Leopardus pardalis, L. wiedii, Panthera onca, Puma concolor, Pu. yagouaroundi, Eira barbara, Galictis vittata, Mustela africana, Lontra longicaudis, Pteronura brasiliensis, Bassaricyon alleni, Nasua nasua, Potos flavus, Procyon cancrivorus), most of which are represented by examined specimens; six species without preserved voucher material are known from camera-trap photographs and/or unambiguous sightings by Matses hunters and field biologists. Although the coati (N. nasua) is the only carnivore occasionally hunted by the Matses for food, Matses interviews are richly informative about the natural history of other species, notably including S. venaticus, Leopardus spp., Pa. onca, Puma spp., and E. barbara. All of the local ungulates (Tapirus terrestris, Pecari tajacu, Tayassu pecari, Mazama americana, M. nemorivaga) are hunted by the Matses for food, and the hunters we interviewed are correspondingly well informed about the natural history of most of these species, with the exception of the seldom-encountered gray brocket (M. nemorivaga). Both species of local cetaceans (Inia geoffroyi, Sotalia fluviatilis) are familiar to the Matses, although neither is eaten. The xenarthrans, carnivores, ungulates, and aquatic mammals that inhabit the Yavari-Ucayali interfluve are all widespread species, so this component of the regional fauna, as currently understood, is not biogeographically distinctive, nor is it extraordinarily diverse (by western Amazonian standards). Although we discuss several noteworthy taxonomic and nomenclatural issues relevant to these taxa, the principal contribution of this report consists in the natural history information compiled from our Matses informants and the resulting overview of local community structure as defined by diurnal activity, locomotion, social behavior, and trophic relationships.
The xenarthrans are the only group of mammals that originated in South America; there are 31 living species: six sloths, four anteaters, and 21 armadillos. In Argentina, 18 species of xenarthrans were cited. The objectives of this study were to compile the existing information on the distribution of the xenarthrans of Argentina, to use species distribution models to map the potential distribution of these species, and to assess patterns of species richness of this important group of mammals. We obtained a total of 975 records corresponding to 706 different collecting localities from Argentina. We generated species distribution models for 15 of the 18 species present in the country. Virtually all of Argentina is occupied by xenarthrans. The highest richness of species is in the north and northeast of the country in the humid and arid Chaco, probably in relation with the mosaic of ecosystems recorded in these regions. These ecoregions have different degrees of habitat degradation and continues to be a major threat for the viability of the xenarthrans occurring there. The information given in this contribution is an input to clarify occurrence and distribution of this group of mammals.
BackgroundThe southern tamandua, Tamandua tetradactyla (Linnaeus, 1758), is the most common species of anteater. Even though much is known about its ecology, behavior, and parasites, there is very limited information about bone diseases in Tamandua and other anteaters. Here, we examined postcranial skeletons of 64T. tetradactyla museum specimens covering most of the material available in Brazilian collections.ResultsThe following bone diseases were identified for the first time in Tamandua and other extant and fossil vermilinguans: osteophytes, osteitis, osteoarthritis, periostitis, exostoses, enthesopathies, and a severe chronic pyogenic osteomyelitis associated with fistulae, cloacae (pus), bone loss, and neoformation processes. Musculoskeletal reconstruction revealed that an old specimen was restricted to terrestrial locomotion due to osteopathological processes that impaired its climbing.ConclusionsNew osteopathological informations are presented for T. tetradactyla, favoring a better understanding of the expression of some bone diseases in wild animals. In addition, the diagnosis of these bone diseases in living anteaters provides useful information for studies on animal health and welfare, as well as contributing to the more effective recognition of paleodiseases in fossil xenarthrans.
This contribution presents new data about the natural history of the screaming hairy armadillo Chaetophractus vellerosus (Mammalia: Xenarthra: Dasypodidae). A seasonal monitoring using the capture-recapture method was performed over the course of two years (2006-2008) in a 100 ha cattle farm in the locality of Magdalena, Buenos Aires province, Argentina. Data were collected on food habits, space and time use, behavior, thermoregulation, population data, and morphology. A total of 237 captures of 136 individuals were made. The main food items recorded were coleopterans, followed by plant matter and small mammals; a marked drop of coleopterans in the spring diet suggested seasonal differences in food habits. In the cold seasons, screaming hairy armadillos were mainly active at noon and during the first hours of the afternoon, while in warm seasons their activity period shifted to the afternoon and night. The armadillos selected sandy-calcareous soils and preferred grasslands with low vegetation and high vegetation cover. The average home range was 2670 m(2). Screaming hairy armadillos were asocial. Their behavior varied between seasons, and they selected the forest for refuge. Rectal temperature was positively correlated with ambient temperature and body mass. The sex proportion was near to one, and no sexual dimorphism was observed. In general, the results of this study are in agreement with previous observations of C. vellerosus populations inhabiting different environmental conditions in very distant areas from the one monitored here. This work provides new information about different aspects of an isolated population that is subjected to high pressure due to habitat modification and use, and is therefore facing a high extinction risk.
The diet of the pichi armadillo ( ) was determined based on analysis of stomach contents of 26 dead individuals confiscated from poachers near Cerro Nevado, Mendoza Province, Argentina. Sand accounted for 66 ± 24% of stomach contents' dry weight. Beetles were the predominant food item in 14 and ants in 5 stomachs, while 5 animals had mainly ingested plant material. The remainder had mostly fed on fly larvae and arachnids. Coleoptera (mainly adults and Scarabeidae larvae) and plant material (seeds, leaves, and roots) were found in all stomachs examined. All pichis had fed on ants of different species and stages, suggesting that pichis eat any ant species they can find and actively prey on nests. Scorpions and spiders were observed in over 60% of stomachs but represented a low aggregate percent weight. Vertebrates were rarely found. Based on these results, the pichi of Mendoza Province can be described as an opportunistic omnivore that mainly feeds on insects and seems to be the least carnivorous of all carnivore–omnivore armadillos.