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Timothy J Gaudin - One of the best experts on this subject based on the ideXlab platform.
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Digital Cranial Endocasts of the Extinct Sloth Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina: Description and Comparison with the Extant Sloths
Journal of Mammalian Evolution, 2020Co-Authors: Alberto Boscaini, Timothy J Gaudin, Dawid A. Iurino, Raffaele Sardella, German Tirao, Francois PujosAbstract:The internal cranial morphology of the terrestrial sloth Glossotherium robustum is described here based on a neurocranium from the late Pleistocene of the Pampean region of Buenos Aires, northeastern Argentina. The first published data on the morphology of the brain cavity of this species date back to the latest nineteenth century. The novel techniques of CT scanning and digital reconstructions enable non-destructive access to the internal cranial features of both extinct and extant vertebrates, and thus improve our knowledge of anatomical features that had previously remained obscure. Therefore, we performed CT scans on the posterior half of a skull of G. robustum and created digital models of the endocasts and internal structures. The results reveal the morphology of the brain cavity itself, as well as the paranasal sinuses and the trajectory of several cranial nerves and blood vessels. These features have been compared with the two extant folivoran genera, the two-toed sloth Choloepus and the three-toed sloth Bradypus . For many characteristics, especially those related to the paranasal pneumaticity and the brain cavity, a closer similarity between Glossotherium and Choloepus is observed, in accordance with the most widely accepted phylogenetic scenarios. However, other features are only shared by the two extant genera, but are probably related to allometric effects and the convergence that affected the two modern lineages. This study, which represents the first exhaustive analysis of digital endocasts of a fossil sloth, reveals the importance of the application of new methodologies, such as CT scans, for elucidating the evolutionary history of this peculiar mammalian clade.
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epaxial musculature in armadillos sloths and opossums functional significance and implications for the evolution of back muscles in the xenarthra
Journal of Mammalian Evolution, 2018Co-Authors: Timothy J Gaudin, John A. NyakaturaAbstract:To investigate the evolution of xenarthran epaxial muscles, fresh specimens of the North American Common long-nosed armadillo Dasypus novemcinctus and of a marsupial, the Virginia opossum Didelphis virginiana, were dissected. Data from one fixed specimen of a two-toed sloth Choloepus didactylus were also used for comparison, because it is a xenarthran exhibiting a highly derived locomotor mode. The opossum was used to represent a more generalized mammalian condition. Each of the three mammalian epaxial muscle groups, the iliocostalis, longissimus dorsi, and transversospinalis, was removed and its mass was determined. All data were corrected for body mass and length. Unpaired, one-tailed t-tests showed the average mass of the iliocostalis and transversospinalis of Dasypus to be significantly larger than the mass of the same muscles in Didelphis, whereas the average mass of the longissimus dorsi was not statistically different between the two species. In agreement with pronounced lateral bending and de-emphasized dorso-ventral flexion and extension, Choloepus also had a relatively large iliocostalis and small longissimus. Our limited data suggest that this condition was inherited from non-arboreal and probably digging early xenarthrans. We believe the relatively larger iliocostalis and transversospinalis muscles in Dasypus can be attributed to the need to provide vertical stabilization of the trunk and resist lateral reaction forces generated by digging. Thus, for Xenarthra it represents a synapomorphy linked to adaptations for fossoriality.
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the basicranium and orbital region of the early miocene eucholoeops ingens ameghino xenarthra pilosa megalonychidae
Ameghiniana, 2015Co-Authors: Timothy J Gaudin, Gerardo De Iuliis, Nestor Toledo, Francois PujosAbstract:Abstract. New, exceptionally well preserved skulls of the basal megalonychid ground sloth Eucholoeops ingens Ameghino have been recovered through recent field work in the late early Miocene Santa Cruz Formation of southern Argentina (Patagonia, Santacrucian SALMA). These specimens have permitted detailed description of the anatomy of the basicranium, endocranium, and orbital wall, including descriptions of the morphology and sutural relationships of the bones from this portion of the skull, and their associated cranial foramina. Comparisons are made to other megalonychid and megatherioid sloths, including the extant two-toed sloth Choloepus Illiger (Megalonychidae). As the descriptions are based on multiple specimens of E. ingens, we have been able to examine intraspecific variation in the features described, and have found marked differences among individual specimens in sutural patterns (e.g., the bones that surround the foramen ovale aperture), cranial foramina (e.g., the presence/absence of a postglen...
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phylogenetic relationships among sloths mammalia xenarthra tardigrada the craniodental evidence
Zoological Journal of the Linnean Society, 2004Co-Authors: Timothy J GaudinAbstract:This study is undertaken in order to evaluate specific hypotheses of relationship among extant and extinct sloths (Mammalia, Xenarthra, Tardigrada). Questions of particular interest include the relationship among the three traditional family groupings of extinct ground sloths and the monophyletic or diphyletic origin of the two genera of extant tree sloths. A computer-based cladistic investigation of the phylogenetic relationships among 33 sloth genera is performed based upon 286 osteological characteristics of the skull, lower jaw, dentition and hyoid arch. Characters are polarized via comparisons with the following successive outgroups, all members of the supraordinal grouping Edentata: the Vermilingua, or anteaters; the Cingulata, or armadillos and glyptodonts; the Palaeanodonta; and the Pholidota, or pangolins. The results of the analysis strongly corroborate the diphyly of living tree sloths, with the three-toed sloth Bradypus positioned as the sister-taxon to all other sloths, and the two-toed sloth Choloepus allied with extinct members of the family Megalonychidae. These results imply that the split between the two extant sloth genera is ancient, dating back perhaps as much as 40 Myr, and that the similarities between the two taxa, including their suspensory locomotor habits, present one of the most dramatic examples of convergent evolution known among mammals. The monophyly of the three traditional ground sloth families Megatheriidae, Megalonychidae and Mylodontidae is confirmed in the present study, and the late Miocene–Pleistocene nothrotheres are shown to form a clade. It is suggested that this latter clade merits recognition as a distinct family-level grouping, the family Nothrotheriidae. The monophyly of the Megatherioidea, a clade including members of the families Megatheriidae, Megalonychidae and Nothrotheriidae, is also supported. Within Megatherioidea, the families Nothrotheriidae and Megatheriidae form a monophyletic group called the Megatheria. The relationships within the families Megatheriidae and Mylodontidae are fully and consistently resolved, although the hypothesized scheme of relationships among the late Miocene to Pleistocene members of the mylodontid subfamily Mylodontinae differ strongly from any proposed by previous authors. Within the family Megalonychidae, Choloepus is allied to a monophyletic grouping of West Indian sloths, although the relationships within this clade are not fully resolved. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140, 255–305.
Francois Pujos - One of the best experts on this subject based on the ideXlab platform.
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Digital Cranial Endocasts of the Extinct Sloth Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina: Description and Comparison with the Extant Sloths
Journal of Mammalian Evolution, 2020Co-Authors: Alberto Boscaini, Timothy J Gaudin, Dawid A. Iurino, Raffaele Sardella, German Tirao, Francois PujosAbstract:The internal cranial morphology of the terrestrial sloth Glossotherium robustum is described here based on a neurocranium from the late Pleistocene of the Pampean region of Buenos Aires, northeastern Argentina. The first published data on the morphology of the brain cavity of this species date back to the latest nineteenth century. The novel techniques of CT scanning and digital reconstructions enable non-destructive access to the internal cranial features of both extinct and extant vertebrates, and thus improve our knowledge of anatomical features that had previously remained obscure. Therefore, we performed CT scans on the posterior half of a skull of G. robustum and created digital models of the endocasts and internal structures. The results reveal the morphology of the brain cavity itself, as well as the paranasal sinuses and the trajectory of several cranial nerves and blood vessels. These features have been compared with the two extant folivoran genera, the two-toed sloth Choloepus and the three-toed sloth Bradypus . For many characteristics, especially those related to the paranasal pneumaticity and the brain cavity, a closer similarity between Glossotherium and Choloepus is observed, in accordance with the most widely accepted phylogenetic scenarios. However, other features are only shared by the two extant genera, but are probably related to allometric effects and the convergence that affected the two modern lineages. This study, which represents the first exhaustive analysis of digital endocasts of a fossil sloth, reveals the importance of the application of new methodologies, such as CT scans, for elucidating the evolutionary history of this peculiar mammalian clade.
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Palaeoproteomics resolves sloth relationships
Nature Ecology & Evolution, 2019Co-Authors: Samantha Presslee, Francois Pujos, Graham Slater, Analía Forasiepi, Roman Fischer, Kelly Molloy, Meaghan Mackie, Jesper Olsen, Alejandro Kramarz, Matías TagliorettiAbstract:The living tree sloths Choloepus and Bradypus are the only remaining members of Folivora, a major xenarthran radiation that occupied a wide range of habitats in many parts of the western hemisphere during the Cenozoic, including both continents and the West Indies. Ancient DNA evidence has played only a minor role in folivoran systematics, as most sloths lived in places not conducive to genomic preservation. Here we utilize collagen sequence information, both separately and in combination with published mitochondrial DNA evidence, to assess the relationships of tree sloths and their extinct relatives. Results from phylogenetic analysis of these datasets differ substantially from morphology-based concepts: Choloepus groups with Mylodontidae, not Megalonychidae; Bradypus and Megalonyx pair together as megatherioids, while monophyletic Antillean sloths may be sister to all other folivorans. Divergence estimates are consistent with fossil evidence for mid-Cenozoic presence of sloths in the West Indies and an early Miocene radiation in South America.
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the basicranium and orbital region of the early miocene eucholoeops ingens ameghino xenarthra pilosa megalonychidae
Ameghiniana, 2015Co-Authors: Timothy J Gaudin, Gerardo De Iuliis, Nestor Toledo, Francois PujosAbstract:Abstract. New, exceptionally well preserved skulls of the basal megalonychid ground sloth Eucholoeops ingens Ameghino have been recovered through recent field work in the late early Miocene Santa Cruz Formation of southern Argentina (Patagonia, Santacrucian SALMA). These specimens have permitted detailed description of the anatomy of the basicranium, endocranium, and orbital wall, including descriptions of the morphology and sutural relationships of the bones from this portion of the skull, and their associated cranial foramina. Comparisons are made to other megalonychid and megatherioid sloths, including the extant two-toed sloth Choloepus Illiger (Megalonychidae). As the descriptions are based on multiple specimens of E. ingens, we have been able to examine intraspecific variation in the features described, and have found marked differences among individual specimens in sutural patterns (e.g., the bones that surround the foramen ovale aperture), cranial foramina (e.g., the presence/absence of a postglen...
Tinka Plese - One of the best experts on this subject based on the ideXlab platform.
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mitogenomics phylogenetic relationships of the current sloth s genera and species bradypodidae and megalonychidae
Mitochondrial DNA, 2018Co-Authors: Manuel Ruizgarcia, Diego Chacón, Tinka Plese, Ingrid Schuler, Joseph Mark ShostellAbstract: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) indica...
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informacion demografica de bradypus variegatus Choloepus hoffmanni y cyclopes didactylus xenarthra pilosa en un bosque humedo tropical secundario de santander colombia
Mastozoología neotropical, 2015Co-Authors: Nicolas Reyesamaya, Diego Rolando Gutierrezsanabria, Yeimy Castillonavarro, Raul A Rodriguez, Tinka PleseAbstract:Demographic information on Bradypus variegatus, Choloepus hoffmanni, and Cyclopes didactylus (Xenarthra: Pilosa) in a secondary wet tropical forest of Santan...
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abundancia y preferencia de habitat de bradypus variegatus y Choloepus hoffmanni durante la epoca seca en dos fragmentos de bosque seco en arboletes antioquia colombia
Edentata, 2011Co-Authors: Juan Fernando Acevedoquintero, Diana Sanchez Granada, Tinka PleseAbstract:Abstract To assess some of the habitat characteristics that are important for the survival of two- and three-toed sloths (Choloepus hoffmanni and Bradypus variegatus), a floristic characterization was done in two fragments of the tropical dry forest in Arboletes, Antioquia, Colombia. The study was performed during the dry season of February – March 2007 in an area intervened by cattle farming activity An index of population abundance of each species was calculated using a method of simple transects. The study about habitat use and preference took into account the following parameters: height, diameter at chest height, exposition of the canopy to the sun, abundance of lianas, and proportions of use and availability of the used plant species. Both species of sloths were more abundant in the forest fragment called El Refugio (1.66 and 0.83 individuals/km, respectively) than in the forest fragment La Quebrada (0.62 and 0.2 individuals/km, respectively). Both species of sloths showed preference for Brownea ari...
Marta Svartman - One of the best experts on this subject based on the ideXlab platform.
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Identification and characterization of satellite DNAs in two-toed sloths of the genus Choloepus (Megalonychidae, Xenarthra).
Scientific reports, 2020Co-Authors: Radarane Santos Sena, Pedro Heringer, Mirela Pelizaro Valeri, Valéria Do Socorro Pereira, Gustavo C. S. Kuhn, Marta SvartmanAbstract:Choloepus, the only extant genus of the Megalonychidae family, is composed of two living species of two-toed sloths: Choloepus didactylus and C. hoffmanni. In this work, we identified and characterized the main satellite DNAs (satDNAs) in the sequenced genomes of these two species. SATCHO1, the most abundant satDNA in both species, is composed of 117 bp tandem repeat sequences. The second most abundant satDNA, SATCHO2, is composed of ~ 2292 bp tandem repeats. Fluorescence in situ hybridization in C. hoffmanni revealed that both satDNAs are located in the centromeric regions of all chromosomes, except the X. In fact, these satDNAs present some centromeric characteristics in their sequences, such as dyad symmetries predicted to form secondary structures. PCR experiments indicated the presence of SATCHO1 sequences in two other Xenarthra species: the tree-toed sloth Bradypus variegatus and the anteater Myrmecophaga tridactyla. Nevertheless, SATCHO1 is present as large tandem arrays only in Choloepus species, thus likely representing a satDNA exclusively in this genus. Our results reveal interesting features of the satDNA landscape in Choloepus species with the potential to aid future phylogenetic studies in Xenarthra and mammalian genomes in general.
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A new karyotype for the two-toed sloth Choloepus didactylus (Magalonychidae, Xenarthra)
Semina-ciencias Agrarias, 2017Co-Authors: Alice Alves Do Espírito Santo, Roscoe Stanyon, Radarane Santos Sena, Mirela Pelizaro Valeri, Valéria Do Socorro Pereira, Marta SvartmanAbstract:Xenarthra, one of the four mammalian superorders, is exclusively found in Central and South America and is possibly positioned at the base of the Eutherian phylogenetic tree. Cytogenetic studies of this group are very few and mainly restricted to the description of the karyotypes after conventional staining, with just a few reported banding patterns. We analyzed the chromosomes of a male Choloepus didactylus (Linnaeus’s two-toed sloth) from Rondonia after GTG- and CBG-banding and silver staining of the nucleolus organizer regions(Ag-NOR). Our specimen presented a karyotype with 2n=51, NF=60, which has not been reported yet for this species. The GTG-banding allowed us to establish the correspondence among all chromosome pairs and was also important to verify a Y/18 autosome translocation, which seems to be characteristic of Choloepus . CBG-banding revealed pericentromeric heterochromatin in all chromosomes, except for the X. Four medium acrocentric autosomes presented Ag-NORs in their short arms. Until now the diploid numbers described for the few individuals of C. didactylus analyzed range from 2n=52-65. The finding of a new karyotype with 2n=51 in our specimen reinforces the need of further studies of this species, which is also taxonomically poorly understood and probably contains several still unidentified taxa. In addition, chromosome studies in Xenarthra are very likely to yield important insights into mammalian genome evolution.
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The Ancestral Eutherian Karyotype Is Present in Xenarthra
PLoS genetics, 2006Co-Authors: Marta Svartman, Gary Stone, Roscoe StanyonAbstract:Molecular studies have led recently to the proposal of a new super-ordinal arrangement of the 18 extant Eutherian orders. From the four proposed super-orders, Afrotheria and Xenarthra were considered the most basal. Chromosome-painting studies with human probes in these two mammalian groups are thus key in the quest to establish the ancestral Eutherian karyotype. Although a reasonable amount of chromosome-painting data with human probes have already been obtained for Afrotheria, no Xenarthra species has been thoroughly analyzed with this approach. We hybridized human chromosome probes to metaphases of species (Dasypus novemcinctus, Tamandua tetradactyla, and Choloepus hoffmanii) representing three of the four Xenarthra families. Our data allowed us to review the current hypotheses for the ancestral Eutherian karyotype, which range from 2n = 44 to 2n = 48. One of the species studied, the two-toed sloth C. hoffmanii (2n = 50), showed a chromosome complement strikingly similar to the proposed 2n = 48 ancestral Eutherian karyotype, strongly reinforcing it.
Alberto Boscaini - One of the best experts on this subject based on the ideXlab platform.
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Digital Cranial Endocasts of the Extinct Sloth Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina: Description and Comparison with the Extant Sloths
Journal of Mammalian Evolution, 2020Co-Authors: Alberto Boscaini, Timothy J Gaudin, Dawid A. Iurino, Raffaele Sardella, German Tirao, Francois PujosAbstract:The internal cranial morphology of the terrestrial sloth Glossotherium robustum is described here based on a neurocranium from the late Pleistocene of the Pampean region of Buenos Aires, northeastern Argentina. The first published data on the morphology of the brain cavity of this species date back to the latest nineteenth century. The novel techniques of CT scanning and digital reconstructions enable non-destructive access to the internal cranial features of both extinct and extant vertebrates, and thus improve our knowledge of anatomical features that had previously remained obscure. Therefore, we performed CT scans on the posterior half of a skull of G. robustum and created digital models of the endocasts and internal structures. The results reveal the morphology of the brain cavity itself, as well as the paranasal sinuses and the trajectory of several cranial nerves and blood vessels. These features have been compared with the two extant folivoran genera, the two-toed sloth Choloepus and the three-toed sloth Bradypus . For many characteristics, especially those related to the paranasal pneumaticity and the brain cavity, a closer similarity between Glossotherium and Choloepus is observed, in accordance with the most widely accepted phylogenetic scenarios. However, other features are only shared by the two extant genera, but are probably related to allometric effects and the convergence that affected the two modern lineages. This study, which represents the first exhaustive analysis of digital endocasts of a fossil sloth, reveals the importance of the application of new methodologies, such as CT scans, for elucidating the evolutionary history of this peculiar mammalian clade.