Sloth Species Research Articles

Molecular Phylogenetics of Bradypus (Three-Toed Sloth, Pilosa: Bradypodidae, Mammalia) and Phylogeography of Bradypus variegatus (Brown-Throated Three-Toed Sloth) with Mitochondrial Gene Sequences

Xenarthra (sloths, anteaters, and armadillos) are the quintessential South American mammals. Among the xenarthrans, sloths constitute the most diverse paleontologically with almost 100 fossil genera recorded. However, this abundant sloth fauna in the Americas became extinct around 10,000 years ago. Only six species belonging to two genera, Bradypus (four three-toed sloth species) and Choloepus (two two-toed sloth species) are alive today in Central and South America. Bradypus variegatus is the sloth species with the widest geographical distribution in the Neotropics. Some regional population genetics have been reported, especially in Brazil, but with limited sample sizes. Herein, we sequenced 77 samples of Bradypys variegatus (Panama, Colombia, Venezuela, Peru, Bolivia, and Brazil; 65 new samples and 12 from GenBank), plus one B. tridactylus, one B. pygmaeus, and five B. torquatus (one new and four from GenBank) at the mitochondrial (mt) control region. Additionally, 25 of these samples, representing the four species, were sequenced for the entire mitochondrial genome. Our results indicate that there are at least six main genetically different haplogroups of B. variegatus. They are the trans-Andean, western Amazon (with some other internal groups), Tapajos River, Tocantins River, Negro River, and the Brazilian eastern Atlantic forest (with two recognizable sub-groups in northern and southern areas) ones, with the ancestor of the trans-Andean haplogroup the first to diverge. A very strong genetic heterogeneity and a striking spatial pattern were detected among these different geographical areas, with the trans-Andean, western Amazon, and Tocantins populations showing the highest levels of genetic diversity, meanwhile the Tapajos and the Brazilian eastern populations yielding lower levels of genetic diversity. The following conclusions were as follows: 1) B. torquatus should be considered as a different genus (Scaeopus) because of its extreme genetic differences from other Bradypus taxa as was previously claimed by other authors; 2) B. pygmaeus is not a recent species adapted to Holocene island environments from the Central America B. variegatus group; and 3) if we adopt a strict version of the Phylogenetic Species Concept (PSC), the highly significant monophyletic clade of the trans-Andean B. variegatus population should be defined as a valid and differentiated species of three-toed sloth. However, we are reluctant to define this population as a new species until new data shows possible strong karyotype differences and/or pre- or post-zygote reproductive barriers (Biological Species Concept, BSC) between the trans and the cis-Andean populations of the three-toed brown-throated sloth.

The earliest well-documented occurrence of sexual dimorphism in extinct sloths: evolutionary and palaeoecological insights

AbstractSexual dimorphism (SD) is extremely common in species that have reproductive roles segregated into separate sexes, and it has been recognized in several mammalian lineages, both extant and extinct. Sexual dimorphism is low to moderate in living sloths, but it had a more important role for extinct sloth taxa. The presence of SD in extinct sloths was first suggested at the end of the 19th century and it is now commonly advocated as a possible explanation of high intraspecific variation in many extinct sloth species. In this paper, we report the presence of SD in Simomylodon uccasamamensis, a Late Miocene to Late Pliocene sloth from the Bolivian Altiplano. We present evidence of SD in the morphology of cranial and postcranial remains, representing the earliest unequivocal occurrence of size-based SD in an extinct sloth species. Differences between sexes are mainly observed in the morphology of the feeding apparatus and general body size. Comparisons with extant large mammals allow us to hypothesize different food selection between the two sexes, with probable divergent habitat use and concomitant niche separation. This, in turn, could have represented an important selective factor for adaptation to environmental changes experienced by the Bolivian Altiplano in Late Neogene times.

The role of sloths and anteaters as Leishmania spp. reservoirs: a review and a newly described natural infection of Leishmania mexicana in the northern anteater.

For years, mammals of the order Pilosa have been considered Leishmania reservoirs. But while most studies have focused on sloth species, anteaters have been overlooked, and in many Leishmania endemic countries like Mexico, no studies have been carried out. The aims of this work were to identify the presence of Leishmania spp. in tissue samples from road-killed northern tamanduas (Tamandua mexicana), using PCR amplification and sequencing of ITS1 DNA, and to discuss the role of Pilosa mammals as reservoirs of Leishmania based on available scientific records. This is the first study that identifies Leishmania in T. mexicana, from 1 of 16 individuals analyzed, so the estimated prevalence (CI 95%) of infection was 6.3% (0.3-27.2). Amplified sequence exhibited a 98.9% (727/735) similarity with L. mexicana, and phylogenetic analysis grouped the species in the L. mexicana-amazonensis cluster. The literature review revealed 241 cases of Leishmania spp. infection among 1219 Pilosa mammals evaluated, with prevalence between studies ranging from 3.5% in the brown-throated three-toed sloth (Bradypus variegatus) to 78% in the Hoffman's two-toed sloth (Choloepus hoffmanni). Current scientific information indicates that C. hoffmanni sloths are reservoirs of Leishmania, and further studies are needed in order to clarify if other Pilosa species play a role in Leishmania transmission.

Homeotic transformations reflect departure from the mammalian \u2018rule of seven\u2019 cervical vertebrae in sloths: inferences on the Hox code and morphological modularity of the mammalian neck

BackgroundSloths are one of only two exceptions to the mammalian ‘rule of seven’ vertebrae in the neck. As a striking case of breaking the evolutionary constraint, the explanation for the exceptional number of cervical vertebrae in sloths is still under debate. Two diverging hypotheses, both ultimately linked to the low metabolic rate of sloths, have been proposed: hypothesis 1 involves morphological transformation of vertebrae due to changes in the Hox gene expression pattern and hypothesis 2 assumes that the Hox gene expression pattern is not altered and the identity of the vertebrae is not changed. Direct evidence supporting either hypothesis would involve knowledge of the vertebral Hox code in sloths, but the realization of such studies is extremely limited. Here, on the basis of the previously established correlation between anterior Hox gene expression and the quantifiable vertebral shape, we present the morphological regionalization of the neck in three different species of sloths with aberrant cervical count providing indirect insight into the vertebral Hox code.ResultsShape differences within the cervical vertebral column suggest a mouse-like Hox code in the neck of sloths. We infer an anterior shift of HoxC-6 expression in association with the first thoracic vertebra in short-necked sloths with decreased cervical count, and a posterior shift of HoxC-5 and HoxC-6 expression in long-necked sloths with increased cervical count.ConclusionAlthough only future developmental analyses in non-model organisms, such as sloths, will yield direct evidence for the evolutionary mechanism responsible for the aberrant number of cervical vertebrae, our observations lend support to hypothesis 1 indicating that the number of modules is retained but their boundaries are displaced. Our approach based on quantified morphological differences also provides a reliable basis for further research including fossil taxa such as extinct ‘ground sloths’ in order to trace the pattern and the underlying genetic mechanisms in the evolution of the vertebral column in mammals.

Interações entre Humanos Pré-Históricos e a Megafauna Quaternária na América do Sul: Aspectos Zooarqueológicos e Paleoecológicos

Human groups spread out over the Asia toward the eastern Siberia until to reach the Americas crossing the Bering Strait. From then on, humans began to coexist with the American Quaternary Megafauna. All researches performed involving human-megafauna interactions so far are parochial and have only revealed punctual occurrences. Compilations and discussions of the incidence of interactions between pre-historic humans and Quaternary megamammals have not been conducted for South America. This paper presents a compilation of paleontological-archeological sites with evidence of pre-historic human-megafauna interaction in South America and discusses their general characteristics in order to generate an overview of these cases and develop a mapping of already acquired information. In addition, we standardize the types of marks found in the previously studied materials, but which did not present a formal description using zooarchaeological terminologies. Human-megafauna interactions are reported in Argentina, Brazil, Venezuela and Uruguay. In South America, species of giant sloths and mastodons seem to have been preferred by humans. Four major types of anthropogenic modifications are observed (sawing and slicing, scraping, chopping and dynamic percussion), however, there is no predominance of a specific type of alteration. These marks are well distributed geographically, as well as in relation to mammalian taxa. Thus, it is not possible to determine a pattern between the types of anthropogenic modifications, geographic location, and taxa. This may indicate that the type of butchering and the damages are independent attributes, and it is likely that different motions would be used for different purposes, depending on the species. The scarcity of butchering cases suggests that megafauna hunting was an opportunistic event, a hypothesis that contrasts with the idea of overkill. The dates obtained are not consistent with the classical model of human arrival in South America – which would have occurred by a single migratory pulse across the Bering Strait –, but corroborate the hypothesis of more complex migration pathways. They also corroborate the hypothesis that the human being cohabited with the Quaternary megafauna for millennia prior to the Late Pleistocene-early Holocene megafaunal extinction.

Nuevos registros fósiles de vertebrados terrestres para Las Llanadas, Sancti Spíritus, Cuba

El depósito paleontológico Las Llanadas es un manantial con sedimento rico en materia orgánica. Estudios del sitio a principios del siglo XX, dieron a conocer materiales fósiles de perezosos, cocodrilos, tortugas terrestres, y jutías. Dos especies de perezosos, Acratocnus antillensis y Neocnus gliriformis, fueron nuevas para la ciencia. En el presente trabajo se dan a conocer nuevos registros fósiles de anuros, un reptil y aves para el depósito: Peltophryne empusus, Osteopilus septentrionalis, Cyclura nubila, Tyto alba, Buteogallus borrasi y Boromys ofella. Huesos recientes de Lithobates catesbeianus y Capromys pilorides se encontraron entre los materiales, lo que indica que el depósito se mantiene activo en la recepción de especímenes. De un total de 2030 piezas solo 3% pudo ser identificado taxonómicamente, debido al alto nivel de fragmentación.

Articular and vertebral lesions in the Pleistocene sloths (Xenarthra, Folivora) from the Brazilian Intertropical Region

We performed a macroscopic study on six species of Pleistocene sloths from the Brazilian Intertropical Region (BIR) including Valgipes bucklandi, Catonyx cuvieri, Mylodonopsis ibseni, Glossotherium sp., Ocnotherium giganteum and Eremotherium laurillardi and compared the results with a previous investigation of Nothrotherium maquinense and Ahytherium aureum. Differential diagnostic analysis revealed six varieties of musculoskeletal diseases: Calcium Pyrosphosphate Deposition Disease (CPPD), Spondyloarthropathy (SpA), Osteoarthritis (OA), Osteochondritis Dessicans (OD), Schmorl’s Node (SN) and Spondylosis Deformans (SD). We also carried out multivariate statistical analyses on all Pleistocene sloths to verify the similarity between taxa based on diagnosed diseases.

Increased xenarthran diversity of the Great American Biotic Interchange: a new genus and species of ground sloth (Mammalia, Xenarthra, Megalonychidae) from the Hemphillian (late Miocene) of Jalisco, Mexico

AbstractA new genus and species of megalonychid sloth,Zacatzontli tecolotlanensisn. gen. n. sp., is described from the late Hemphillian of Jalisco, Mexico. Comparison and analysis of the type specimen, a mandible, with other megalonychid sloths shows a closer relationship to South American taxa than those from North America or the Caribbean. This suggests that during the early stages of the Great American Biotic Interchange there were two separate dispersal events of megalonychid sloths—an earlier one represented byPliometanastesand the later one byZacatzontlin. gen. While the morphology of the spout ofZacatzontlimore closely resembles that ofMegalonyx, based on the current record,Zacatzontlidoes does not enter North America until after the evolution ofMegalonyxfromPliometanastes. The role of the northern neotropics in South America as a staging area for South American taxa that entered North America is discussed.

FIRST RECORD OF HEMATOLOGIC VALUES IN FREE-LIVING AND CAPTIVE MANED SLOTHS (BRADYPUS TORQUATUS; XENARTHA, BRADYPODIDAE).

Bradypus torquatus is a rare and endemic sloth species from the Atlantic Forest, Brazil. Due to a lack of medical information including hematologic reference parameters for the species, hematologic baseline values were determined using samples from 14 clinically healthy B. torquatus , under captive (n = 7) and free-living (n = 7) conditions in Bahia State, Brazil. Additionally, the morphology of the blood cells is presented, with a demonstration that the Barr body chromosome may assist with sex determination of the species. The Barr body chromosome was present in all seven females and absent in all males. Many erythrocytes were approximately the size of small lymphocytes, with red blood cells exhibiting anisocystosis, normochromia, and apparent macrocytosis, compared with domestic animals. This study provides the first published hematologic values and cell morphology for B. torquatus . However, further studies are suggested using an automated hematology analyzer with larger sample sizes so that reference intervals may be established and hematologic values better understood for sex, habitat type, and age cohorts.

Xibalbaonyx oviceps, a new megalonychid ground sloth (Folivora, Xenarthra) from the Late Pleistocene of the Yucatán Peninsula, Mexico, and its paleobiogeographic significance

Here we describe a new genus and species of giant ground sloth, Xibalbaonyx oviceps (Megalonychidae, Xenarthra), from the drowned cave system of the northeastern Yucatan Peninsula. The specimen is Late Pleistocene in age and was discovered in the Zapote sinkhole (cenote) near Puerto Morelos in the Mexican state of Quintana Roo. Xibalbaonyx oviceps differs significantly from all hitherto known Megalonychidae including those from the Greater Antilles and South America. The new taxon suggests a local Caribbean radiation of ground sloths during the Late Pleistocene, which is consistent with the dispersal of the group along a Mexican corridor.

A new genus of megalonychid ground sloth (Mammalia, Xenarthra) from the late Pleistocene of Quintana Roo, Mexico

ABSTRACTA new genus and species of late Pleistocene megalonychid sloth, Nohochichak xibalbahkah, gen. et sp. nov., is described from Hoyo Negro, a chamber in the Sac Actun cave system, Quintana Roo, Mexico. Phylogenetic analysis indicates that this new sloth is most closely related to Meizonyx salvadorensis from the middle Pleistocene of El Salvador, and that these two genera in turn are the sister clade to Megistonyx and Ahytherium in South America and not the other North American megalonychids, Pliometanastes and Megalonyx. This new sloth indicates that the number of sloth taxa involved in the Great American Biotic Interchange is greater than previously understood, and that a significant part of the Interchange biodiversity, as represented by taxa confined to the semitropical and tropical portions of Central and North America, remains to be discovered.Citation for this article: McDonald, H. G., J. C. Chatters, and T. J. Gaudin. 2017. A new genus of megalonychid ground sloth (Mammalia, Xenarthra) from the late Pleistocene of Quintana Roo, Mexico. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1307206.

Mitogenomics phylogenetic relationships of the current sloth’s genera and species (Bradypodidae and Megalonychidae)

We sequenced the complete mitogenome of 39 sloths (19 Bradypus variegatus, 4 B. tridactylus, 1 B. pygmaeus, 1 B. torquatus, 4 Choloepus didactylus, and 10 C. hoffmanni). A Bayesian tree (BI) indicated a temporal split between Bradypus and Choloepus around 31 million years ago (MYA, Oligocene) and the other major splits within each genera during the Miocene and Pliocene. A haplotype network (MJN) estimated a lower temporal split between the sloth genera (around 23.5 MYA). Both methods detected the ancestor of B. torquatus as the first to diverge within Bradypus (21 for BI and 19 MJN), followed by that of the ancestor of B. tridactylus. The split of B. pygmaeus from the common ancestor with B. variegatus was around 12 MYA (BI) or 4.3 MYA (MJN). The splits among the previous populations of B. variegatus began around 8 MYA (BI) or 3.6 MYA (MJN). The trans-Andean population was the first to diverge from the remaining cis-Andean populations of B. variegatus. The genetic differentiation of the trans-Andean B. variegatus population relative to the cis-Andean B. variegatus is similar to that found for different species of sloths. The mitogenomic analysis resolved the differentiation of C. hoffmanni from the C. didactylus individuals of the Guiana Shield. However, one C. didactylus from the Colombian Amazon specimen was inside the C. hoffmanni clade. This could be the first example of possible natural hybridization in the Amazon of both Choloepus taxa or the existence of un-differentiable phenotypes of these two species in some Amazonian areas.

Distribution and current state of knowledge of Hoffmann’s two-toed sloth (Choloepus hoffmanni) in Colombia, with comments on the variations of its external morphological traits

Hoffmann's two-toed sloth ( Choloepus hoffmanni ) has been extensively studied since the 1940s in some countries across its distribution range. However, several aspects of its biology remain unexplored or have only been described superficially. This study updated the geographic distribution of this sloth species in Colombia, describing external features of specimens that inhabit different areas of the country. Additionally, a revision of the current state of knowledge of this species in Colombia was conducted, with a focus on the identification of information gaps and the major threats affecting this species. An updated map of the distribution of C. hoffmanni in Colombia was elaborated, including the distribution reported by IUCN, the records of specimens received in the Xenarthra center for rescue and rehabilitation (CRRX, for its acronym in Spanish; primary information), the wildlife care centers of the Autonomous Regional Corporations (CARs, for its acronym in Spanish), and records of biological collections available online (secondary information). CRRX specimens were examined externally, and the external morphological characteristics (skull and body shape; pelage color, length and density) were described. A comprehensive literature review was performed, compiling studies conducted over the last two decades on this species in Colombia, analyzing their respective contributions to its knowledge. The records obtained provide localities of occurrence for the species not previously recognized by IUCN, in 54 municipalities of 12 departments of Colombia. There are external morphological patterns defining lowland (interandean valleys and Caribbean region), highland (Colombian Andes) and Colombian Pacific populations. The biggest information gaps regard demography, distribution and genetics. The main threats identified are habitat loss (infrastructure construction, forest clearance) and specimen collection (illegal trade). The localities of occurrence obtained confirm the distribution of this species in areas previously reported at the north and center of the Cordillera Occidental, Cordillera Central and Cauca River valley, besides the north, center and south of the Cordillera Oriental, Piedemonte Llanero, and the southern Magdalena River valley. The external review of specimens by CRRX shows that although it is impossible to derive clear taxonomic inferences from the evidence collected, pelage color, length and density are the most representative external traits that differentiate lowland, highland and Pacific Colombian populations. The prioritization of issues such as the conservation status and threats in the investigation of this species in Colombia during the last twenty years have relegated key aspects such as demography, distribution, taxonomy and genetics, a fact that poses a challenge for the execution of proper management actions in the country.

Morphological analysis of teeth in Bradypus variegatus Schinz, 1825 (Mammalia, Bradypodidae)

http://dx.doi.org/10.5007/2175-7925.2016v29n3p35Dentre os bichos-preguiça, pode-se destacar a espécie Bradypus variegatus, encontrada especialmente no Nordeste brasileiro. Diante da importância e escassez de informações acerca do sistema digestório de animais silvestres, o objetivo deste artigo é descrever a morfologia dos dentes dessa espécie de preguiça. Para tal, foram utilizados quatro animais adultos, pertencentes ao acervo de anatomia do Centro Acadêmico de Vitória de Santo Antão da Universidade Federal de Pernambuco (UFPE). Os dentes das preguiças foram analisados, retirados das arcadas e, em seguida, submetidos a duas técnicas de preparação histológica de tecido duro, desgaste e descalcificação. As lâminas obtidas foram analisadas em microscópio óptico. As preguiças têm 18 dentes molariformes, com cúspides e espaços interdentais. De acordo com a análise histológica, percebeu-se que os dentes não possuem esmalte, sendo compostos por 1 camada espessa de cemento e 2 camadas de dentina, uma externa e outra interna. A polpa apresenta um aspecto semelhante à humana. Pôde-se constatar, ainda, a presença de ligamento periodontal espesso e vascularizado entre o dente e o osso alveolar, este último com ósteons facilmente identificados.

A reappraisal of the phylogeny of the Megatheria (Mammalia: Tardigrada), with an emphasis on the relationships of the Thalassocninae, the marine sloths

The Thalassocninae is a monogeneric subfamily of five species of Neogene sloths. Until now, Thalassocnus has been considered as belonging to the Nothrotheriidae, a family of megatherian ‘ground sloths’ of intermediate body size. However, no previous phylogenetic analysis has questioned such a familial attribution. Here we performed an extensive analysis including the required taxonomic sampling for such an attribution and characters from the whole skeleton. We found that Thalassocnus indeed belongs to Megatheria, but is clustered amongst Megatheriidae, the family that includes the large-size Megatherium. Moreover, the relationships amongst the five species of Thalassocnus are congruent with their respective stratigraphical positions, which allows the recognition of numerous morphoclines that document the adaptation of these sloths to the marine environment.

A Paleogeographic Overview of Tropical Fossil Sloths: Towards an Understanding of the Origin of Extant Suspensory Sloths?

Modern sloths are among the more characteristic mammals of South and Central American faunas. Recent discovery in four Paleogene, 22 Neogene, and dozens of Pleistocene fossiliferous localities in the tropics has revealed an unexpected paleobioversity constituted by some 81 fossil sloth species. Probably originating in southern South America near the Eocene/Oligocene transition, sloths were represented in the tropics during the late Oligocene by Pseudoglyptodon, Mylodontidae, and Megalonychidae. The latter occupied the West Indies between at least the late early Miocene and late Pleistocene, and two mylodontid clades, Octodontobradyinae and Urumacotheriinae, were characteristic of Amazonian localities from the Colhuehuapian and the Laventan periods, respectively, until the end of the Miocene. Megatheriinae and Nothrotheriidae appeared during the middle Miocene, colonizing the tropics and then North America, where Mylodontidae and Megalonychidae had already been present since the early late Miocene. Nothrotheriids are more abundant and diversified during the late Miocene in the tropics than in southern South America. Remains closely related to either of the modern sloths are absent from the fossil record, including those in the tropics. The characteristic suspensory posture of Bradypus and Choloepus appeared independently and likely after the Miocene epoch, and thus well after the hypothesized split suggested by molecular studies of the respective clades of these genera. Given their current widespread distribution in and reliance on the tropics, prospecting efforts for the direct fossil kin of suspensory sloths should concentrate on deposits in the Amazonian region, as this area has shown promise in producing fossil sloths.

Baraguatherium takumara, Gen. et Sp. Nov., the Earliest Mylodontoid Sloth (Early Miocene) from Northern South America

We report a new genus and species of sloth, based on a partial mandible and associated femur, from the early Miocene of Venezuela. Baraguatherium takumara, gen. et sp. nov., represents the earliest member of the Mylodontoidea recognized from northern South America. Phylogenetically and morphologically, Baraguatherium possesses some plesiomorphic characters: a vasodentine layer in the core of the tooth similar to Octodontotherium, Paroctodontotherium, and Orophodon; molariforms parallel to the long axis of the toothrow; teeth with a very thin layer of cementum; mf1-mf3 series of similar size and bilobate; mf3 conspicuously piriform; and occlusal surface of tooth beveled, which places it at the base of the Mylodontidae clade. Baraguatherium was found in continental deposits that also preserve abundant wood and leaves associated with a near shore marine complex, indicating that Baraguatherium lived in a coastal tropical forest in the early Miocene in northern South America. The presence of a vasodentine layer in the core of the tooth is quite similar to Octodontotherium, Paroctodontotherium, and Orophodon and allows assignment of this new taxon to the Mylodontoidea.

Evolutionary Relationships among Extinct and Extant Sloths: The Evidence of Mitogenomes and Retroviruses.

Macroevolutionary trends exhibited by retroviruses are complex and not entirely understood. The sloth endogenized foamy-like retrovirus (SloEFV), which demonstrates incongruence in virus–host evolution among extant sloths (Order Folivora), has not been investigated heretofore in any extinct sloth lineages and its premodern history within folivorans is therefore unknown. Determining retroviral coevolutionary trends requires a robust phylogeny of the viral host, but the highly reduced modern sloth fauna (6 species in 2 genera) does not adequately represent what was once a highly diversified clade (∼100 genera) of placental mammals. At present, the amount of molecular data available for extinct sloth taxa is limited, and analytical results based on these data tend to conflict with phylogenetic inferences made on the basis of morphological studies. To augment the molecular data set, we applied hybridization capture and next-generation Illumina sequencing to two extinct and three extant sloth species to retrieve full mitochondrial genomes (mitogenomes) from the hosts and the polymerase gene of SloEFV. The results produced a fully resolved and well-supported phylogeny that supports dividing crown families into two major clades: 1) The three-toed sloth, Bradypus, and Nothrotheriidae and 2) Megalonychidae, including the two-toed sloth, Choloepus, and Mylodontidae. Our calibrated time tree indicates that the Miocene epoch (23.5 Ma), particularly its earlier part, was an important interval for folivoran diversification. Both extant and extinct sloths demonstrate multiple complex invasions of SloEFV into the ancestral sloth germline followed by subsequent introgressions across different sloth lineages. Thus, sloth mitogenome and SloEFV evolution occurred separately and in parallel among sloths.

Additions to the knowledge of the ground sloth Catonyx tarijensis (Xenarthra, Pilosa) in the Pleistocene of Argentina

Quaternary Scelidotheriinae (Mammalia, Xenarthra, Mylodontidae) are represented by three genera: Scelidotherium Owen, Valgipes Gervais, and Catonyx Ameghino. The genus Catonyx includes three species of ground sloths: C. cuvieri (Lund), C. tarijensis (Gervais and Ameghino), and C. chiliensis (Lydekker). Catonyx tarijensis and C. chiliensis were present during the Quaternary of Argentina. The aim of this contribution is to improve the knowledge of C. tarijensis of Argentina from a morphological, systematic, and biostratigraphic point of view. The presence of C. tarijensis is recorded in the Ensenadan–Lujanian South American Land Mammal Ages (SALMAs) (Early Pleistocene–Late Pleistocene) of Buenos Aires Province, in the Lujanian SALMA (Late Pleistocene) of Corrientes Province, and in the Pleistocene of Cordoba and Salta Provinces. Outside Argentina, this species is recorded in the Late Pleistocene of Bolivia and Uruguay.

Underground chamber systems excavated by cenozoic ground sloths in the state of Rio Grande do Sul, Brazil

A regional survey of the caves of the state of Rio Grande do Sul, Brazil, listed hundreds of caves with varied origins. Among these, we identified two large caves with special characteristics, one located in the city of Santa Cruz do Sul and the other in the municipality of Vale Real. Both evolve in an approximately horizontal plane, extend tens of meters into the interior of the respective elevations, and do not show any signs of present or past underground drainage. Concave surfaces on the walls stand out in their morphologies, which suggest that the caves originally constituted a system of ellipsoidal chambers, each chamber with original height of approximately 1.5 m and diameter between 3.5 and 7 m. The individual chambers were connected by relatively short tunnels.These chambers are best preserved in the cave of Santa Cruz do Sul; the cave of Vale Real appears to have been much disfigured, both because of inorganic processes and anthropogenic action. The general characteristics of these two caves enable us to propose that they originated from the activity of digging ground sloths of the South American Megafauna. Their dimensions suggest that they were excavated and inhabited not by individual animals, but by groups of sloths. The original polished walls suggest that the caves were used for extended periods, possibly in the order of centuries. Their morphology is so different from other tunnel systems that were excavated by the Megafauna and found in southern Brazil, that we suggest that this morphology of chamber systems is associated with a specific species of ground sloth, whose identification will be very difficult.