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Timothy J Gaudin - One of the best experts on this subject based on the ideXlab platform.
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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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Phylogenetic and functional implications of the ear region anatomy of Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina.
Die Naturwissenschaften, 2018Co-Authors: Alberto Boscaini, Dawid A Iurino, German Tirao, Timothy J Gaudin, Guillaume Billet, Lionel Hautier, Raffaele Sardella, François PujosAbstract:Several detailed studies of the external morphology of the ear region in extinct sloths have been published in the past few decades, and this anatomical region has proved extremely helpful in elucidating the phylogenetic relationships among the members of this mammalian clade. Few studies of the inner ear anatomy in these peculiar animals were conducted historically, but these are increasing in number in recent years, in both the extinct and extant representatives, due to wider access to CT-scanning facilities, which allow non-destructive access to internal morphologies. In the present study, we analyze the extinct ground sloth Glossotherium robustum and provide a description of the external features of the ear region and the endocranial side of the petrosal bone, coupled with the first data on the anatomy of the bony labyrinth. Some features observable in the ear region of G. robustum (e.g., the shape and size of the entotympanic bone and the morphology of the posteromedial surface of the petrosal) are highly variable, both intraspecifically and intraindividually. The form of the bony labyrinth of G. robustum is also described, providing the first data from this anatomical region for the family Mylodontidae. The anatomy of the bony labyrinth of the genus Glossotherium is here compared at the level of the superorder Xenarthra, including all available extant and extinct representatives, using geometric morphometric methods. In light of the new data, we discuss the evolution of inner ear anatomy in the Xenarthran clade, and most particularly in sloths, considering the influence of phylogeny, allometry, and physiology on the shape of this highly informative region of the skull. These analyses show that the inner ear of Glossotherium more closely resembles that of the extant anteaters, and to a lesser extent those of the giant ground sloth Megatherium and euphractine armadillos, than those of the extant sloths Bradypus and Choloepus, further demonstrating the striking morphological convergence between the two extant sloth genera.
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paleogene Xenarthra and the evolution of south american mammals
Journal of Mammalogy, 2015Co-Authors: Timothy J Gaudin, Darin A CroftAbstract:Recent studies show Xenarthra to be even more isolated systematically from other placental mammals than traditionally thought. The group not only represents 1 of 4 primary placental clades, but proposed links to other fossorial mammal taxa (e.g., Pholidota, Palaeanodonta) have been contradicted. No unambiguous Paleocene fossil Xenarthran remains are known, and Eocene remains consist almost exclusively of isolated cingulate osteoderms and isolated postcrania of uncertain systematic provenance. Cingulate skulls are unknown until the late middle Eocene, and the oldest sloth and anteater skulls are early Oligocene and early Miocene age, respectively; there are no nearly complete Xenarthran skeletons until the early Miocene. Ecological reconstructions of early Xenarthrans based on extant species and the paleobiology of extinct Neogene taxa suggest the group's progenitors were myrmecophagous with digging and perhaps some climbing adaptations. The earliest cingulates were terrestrial diggers and likely myrmecoph...
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Form and Function in the Xenarthra–an Introduction to the Symposium Proceedings Volume
Journal of Mammalian Evolution, 2012Co-Authors: Timothy J Gaudin, François PujosAbstract:This special issue of the Journal of Mammalian Evolution represents the proceedings from a symposium held in conjunction with the 9th International Congress of Vertebrate Morphology (ICVM IX, Punta del Este, Uruguay, July 29, 2010), and entitled “Form and Function in the Xenarthra.” This symposium was the third on Xenarthran biology to be presented in association with the ICVM meetings. In this brief introduction to the symposium proceedings, we plan to discuss the justification for the symposium, to provide a brief history of previous symposia and their results, and to introduce the contents of the present volume.
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Nouveaux paresseux terrestres (Mammalia, Xenarthra, Mylodontidae) du Néogène de l'Altiplano bolivien
Geodiversitas, 2010Co-Authors: Pierre-antoine Saint-andre, Timothy J Gaudin, François Pujos, Gerardo De Iuliis, H. Gregory Mcdonald, Cástor Cartelle, Bernardino Mamani QuispeAbstract:ABSTRACT New ground sloths (Mammalia, Xenarthra, Mylodontidae) from the Neogene of the Bolivian Altiplano. Two new Mylodontinae (Xenarthra, Tardigrada, Mylodontoidea) from the Bolivian Altiplano are described. One of them, Pleurolestodon dalenzae n. sp., was discovered a few meters below a volcanic tuff, Toba 76, that may be used as a reference stratigraphic level and is dated at 5.4 Ma; it could be Huayquerian (late Miocene) or at the Huayquerian-Montehermosan boundary in age. The other taxon, Simomylodon uccasamamensis n. gen., n. sp., was recovered from many localities of a horizon bounded below by Toba 76 and above by another volcanic level, the 2.8 Ma Ayo Ayo tuff; its age is Montehermosan-Chapadmalalan (early and middle Pliocene). Analysis of these taxa indicates that they are Mylodontidae more closely related to Glossotherium, Glossotheridium, Kiyumylodon and Paramylodon than to Lestodon or Thinobadistes.
Frédéric Delsuc - One of the best experts on this subject based on the ideXlab platform.
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Resolving the phylogenetic position of Darwin's extinct ground sloth (Mylodon darwinii) using mitogenomic and nuclear exon data
Proceedings of the Royal Society B: Biological Sciences, 2018Co-Authors: Frédéric Delsuc, Gillian Gibb, Melanie Kuch, Jacob Enk, Jonathan Hughes, Paul Szpak, John Southon, Ana Duggan, Hendrik PoinarAbstract:Mylodon darwinii is the extinct giant ground sloth named after Charles Darwin, who first collected its remains in South America. We have successfully obtained a high-quality mitochondrial genome at 99-fold coverage using an Illumina shotgun sequencing of a 12 880-year-old bone fragment from Mylodon Cave in Chile. Low level of DNA damage showed that this sample was exceptionally well preserved for an ancient subfossil, probably the result of the dry and cold conditions prevailing within the cave. Accordingly, taxonomic assessment of our shotgun metagenomic data showed a very high percentage of endogenous DNA with 22% of the assembled metagenomic contigs assigned to Xenarthra. Additionally, we enriched over 15 kb of sequence data from seven nuclear exons, using target sequence capture designed against a wide Xenarthran dataset. Phylogenetic and dating analyses of the mitogenomic dataset including all extant species of Xenarthrans and the assembled nuclear supermatrix unambiguously place Mylodon darwinii as the sister-group of modern two-fingered sloths, from which it diverged around 22 million years ago. These congruent results from both the mitochondrial and nuclear data support the diphyly of the two modern sloth lineages, implying the convergent evolution of their unique suspensory behaviour as an adaption to arboreality. Our results offer promising perspectives for whole-genome sequencing of this emblematic extinct taxon.
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Shotgun Mitogenomics Provides a Reference Phylogenetic Framework and Timescale for Living Xenarthrans
Molecular Biology and Evolution, 2016Co-Authors: Gillian Gibb, Mariella Superina, Nádia De Moraes-barros, Fabien Condamine, Melanie Kuch, Jacob Enk, Hendrik Poinar, Frédéric DelsucAbstract:Xenarthra (armadillos, sloths, and anteaters) constitutes one of the four major clades of placental mammals. Despite their phylogenetic distinctiveness in mammals, a reference phylogeny is still lacking for the 31 described species. Here we used Illumina shotgun sequencing to assemble 33 new complete mitochondrial genomes, establishing Xenarthra as the first major placental clade to be fully sequenced at the species level for mitogenomes. The resulting data set allowed the reconstruction of a robust phylogenetic framework and timescale that are consistent with previous studies conducted at the genus level using nuclear genes. Incorporating the full species diversity of extant Xenarthrans points to a number of inconsistencies in Xenarthran systematics and species definition. We propose to split armadillos into two distinct families Dasypodidae (dasypodines) and Chlamyphoridae (euphractines, chlamyphorines, and tolypeutines) to better reflect their ancient divergence, estimated around 42 Ma. Species delimitation within long-nosed armadillos (genus Dasypus) appeared more complex than anticipated, with the discovery of a divergent lineage in French Guiana. Diversification analyses showed Xenarthra to be an ancient clade with a constant diversification rate through time with a species turnover driven by high but constant extinction. We also detected a significant negative correlation between speciation rate and past temperature fluctuations with an increase in speciation rate corresponding to the general cooling observed during the last 15 My. Biogeographic reconstructions identified the tropical rainforest biome of Amazonia and the Guiana Shield as the cradle of Xenarthran evolutionary history with subsequent dispersions into more open and dry habitats.
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Retroposed elements and their flanking regions resolve the evolutionary history of Xenarthran mammals (armadillos, anteaters, and sloths).
Molecular Biology and Evolution, 2007Co-Authors: Maren Möller-krull, Mariella Superina, Frédéric Delsuc, Emmanuel Douzery, Gennady Churakov, Claudia Marker, Jürgen Brosius, Jürgen SchmitzAbstract:Armadillos, anteaters, and sloths (Order Xenarthra) comprise 1 of the 4 major clades of placental mammals. Isolated in South America from the other continental landmasses, Xenarthrans diverged over a period of about 65 Myr, leaving more than 200 extinct genera and only 31 living species. The presence of both ancestral and highly derived anatomical features has made morphoanatomical analyses of the Xenarthran evolutionary history difficult, and previous molecular analyses failed to resolve the relationships within armadillo subfamilies. We investigated the presence/absence patterns of retroposons from approximately 7,400 genomic loci, identifying 35 phylogenetically informative elements and an additional 39 informative rare genomic changes (RGCs). DAS-short interspersed elements (SINEs), previously described only in the Dasypus novemcinctus genome, were found in all living armadillo genera, including the previously unsampled Chlamyphorus, but were noticeably absent in sloths. The presence/absence patterns of the phylogenetically informative retroposed elements and other RGCs were then compared with data from the DNA sequences of the more than 12-kb flanking regions of these retroposons. Together, these data provide the first fully resolved genus tree of Xenarthrans. Interestingly, multiple evidence supports the grouping of Chaetophractus and Zaedyus as a sister group to Euphractus within Euphractinae, an association that was not previously demonstrated. Also, flanking sequence analyses favor a close phylogenetic relationship between Cabassous and Tolypeutes within Tolypeutinae. Finally, the phylogenetic position of the subfamily Chlamyphorinae is resolved by the noncoding sequence data set as the sister group of Tolypeutinae. The data provide a stable phylogenetic framework for further evolutionary investigations of Xenarthrans and important information for defining conservation priorities to save the diversity of one of the most curious groups of mammals.
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Molecular systematics of armadillos (Xenarthra, Dasypodidae): contribution of maximum likelihood and Bayesian analyses of mitochondrial and nuclear genes.
Molecular Phylogenetics and Evolution, 2003Co-Authors: Frédéric Delsuc, Michael J. Stanhope, Emmanuel DouzeryAbstract:The 30 living species of armadillos, anteaters, and sloths (Mammalia: Xenarthra) represent one of the three major clades of placentals. Armadillos (Cingulata: Dasypodidae) are the earliest and most speciose Xenarthran lineage with 21 described species. The question of their tricky phylogeny was here studied by adding two mitochondrial genes (NADH dehydrogenase subunit 1 [ND1] and 12S ribosomal RNA [12S rRNA]) to the three protein-coding nuclear genes (alpha2B adrenergic receptor [ADRA2B], breast cancer susceptibility exon 11 [BRCA1], and von Willebrand factor exon 28 [VWF]) yielding a total of 6869 aligned nucleotide sites for thirteen Xenarthran species. The two mitochondrial genes were characterized by marked excesses of transitions over transversions-with a strong bias toward CT transitions for the 12S rRNA-and exhibited two- to fivefold faster evolutionary rates than the fastest nuclear gene (ADRA2B). Maximum likelihood and Bayesian phylogenetic analyses supported the monophyly of Dasypodinae, Tolypeutinae, and Euphractinae, with the latter two armadillo subfamilies strongly clustering together. Conflicting branching points between individual genes involved relationships within the subfamilies Tolypeutinae and Euphractinae. Owing to a greater number of informative sites, the overall concatenation favored the mitochondrial topology with the classical grouping of Cabassous and Priodontes within Tolypeutinae, and a close relationship between Euphractus and Chaetophractus within Euphractinae. However, low statistical support values associated with almost equal distributions of apomorphies among alternatives suggested that two parallel events of rapid speciation occurred within these two armadillo subfamilies.
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Molecular phylogeny of living Xenarthrans and the impact of character and taxon sampling on the placental tree rooting.
Molecular Biology and Evolution, 2002Co-Authors: Frédéric Delsuc, Wilfried W. De Jong, Mark S Springer, François Catzeflis, Michael J. Stanhope, Ole Madsen, Mark Scally, Emmanuel DouzeryAbstract:Extant Xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, Xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living Xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling.
Wilfried W. De Jong - One of the best experts on this subject based on the ideXlab platform.
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Indels in protein-coding sequences of Euarchontoglires constrain the rooting of the eutherian tree.
Molecular phylogenetics and evolution, 2003Co-Authors: Wilfried W. De Jong, Marjon A.m. Van Dijk, Céline Poux, Guido Kappé, Teun Van Rheede, Ole MadsenAbstract:Abstract Despite the availability of large molecular data sets, the position of the root of the eutherian tree remains a controversial issue. Depending on source data, taxon sampling and analytical approach, the root can be placed at either Afrotheria, Xenarthra, Afrotheria + Xenarthra, or murid rodents. We explored the phylogenetic potential of indels in four nuclear protein-coding genes (SCA1, PRNP, TNFα, and HspB3) with regard to a possible rooting at the murid branch. According to parsimony principles, five indels were interpreted to contradict such a rooting, and one indel to support it. The results illustrate that indels, despite the occurrence of homoplasy, can be convincing sources of independent molecular evidence to distinguish between alternative phylogenetic hypotheses.
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Molecular phylogeny of living Xenarthrans and the impact of character and taxon sampling on the placental tree rooting.
Molecular Biology and Evolution, 2002Co-Authors: Frédéric Delsuc, Wilfried W. De Jong, Mark S Springer, François Catzeflis, Michael J. Stanhope, Ole Madsen, Mark Scally, Emmanuel DouzeryAbstract:Extant Xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, Xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living Xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling.
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The Virtues of Gaps: Xenarthran (Edentate) Monophyly Supported by a Unique Deletion in αA-Crystallin
Systematic Biology, 1999Co-Authors: Marjon A.m. Van Dijk, François Catzeflis, Emmanuel Paradis, Wilfried W. De JongAbstract:Shared insertions or deletions (indels) in protein-coding DNA can be strong indicators of the monophyly of a taxon. A three-amino acid deletion had previously been noted in the eye lens protein a A-crystallin of two species of sloths and two species of anteaters, which represent the Pilosa, one of the twoinfraorders of Xenarthra(Edentata). This deletion has notbeen observed in 55 species from 16 other eutherian orders, or in 2 species of marsupials, or in 34 nonmammalian verte- brates, from birds to shark. At thegenomic level, we havenow detected this deletion in two species of armadillos of the second Xenarthran infraorder, Cingulata, as well as in an additional species of anteater. Phylogenetic trees were constructed from a 145-bp sequence of the a A-crystallin gene of 39 tetrapod species, supporting Xenarthran monophyly with values from 76% to 90%. To quantify the additional support for Xenarthran monophyly, as given by the three-residue deletion, we com- puted the probabilities for the occurrence of this deletion per evolutionary time unit for alternative hypothetical tree topologies. In the estimates obtained, the six trees in which the Xenarthran sub- groups are unresolved or paraphyletic give an increasingly lower likelihood than do the two trees that assume Xenarthran monophyly. For the monophyletic trees, the probability that the deletion observed in the Xenarthrans is due to a single event is > 0.99. Thus, this deletion in a A-crystallin gives strong molecular support for the monophyly of this old and diverse order. (Edentata; indels; molecular phylogeny; Xenarthra.)
Emmanuel Douzery - One of the best experts on this subject based on the ideXlab platform.
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Retroposed elements and their flanking regions resolve the evolutionary history of Xenarthran mammals (armadillos, anteaters, and sloths).
Molecular Biology and Evolution, 2007Co-Authors: Maren Möller-krull, Mariella Superina, Frédéric Delsuc, Emmanuel Douzery, Gennady Churakov, Claudia Marker, Jürgen Brosius, Jürgen SchmitzAbstract:Armadillos, anteaters, and sloths (Order Xenarthra) comprise 1 of the 4 major clades of placental mammals. Isolated in South America from the other continental landmasses, Xenarthrans diverged over a period of about 65 Myr, leaving more than 200 extinct genera and only 31 living species. The presence of both ancestral and highly derived anatomical features has made morphoanatomical analyses of the Xenarthran evolutionary history difficult, and previous molecular analyses failed to resolve the relationships within armadillo subfamilies. We investigated the presence/absence patterns of retroposons from approximately 7,400 genomic loci, identifying 35 phylogenetically informative elements and an additional 39 informative rare genomic changes (RGCs). DAS-short interspersed elements (SINEs), previously described only in the Dasypus novemcinctus genome, were found in all living armadillo genera, including the previously unsampled Chlamyphorus, but were noticeably absent in sloths. The presence/absence patterns of the phylogenetically informative retroposed elements and other RGCs were then compared with data from the DNA sequences of the more than 12-kb flanking regions of these retroposons. Together, these data provide the first fully resolved genus tree of Xenarthrans. Interestingly, multiple evidence supports the grouping of Chaetophractus and Zaedyus as a sister group to Euphractus within Euphractinae, an association that was not previously demonstrated. Also, flanking sequence analyses favor a close phylogenetic relationship between Cabassous and Tolypeutes within Tolypeutinae. Finally, the phylogenetic position of the subfamily Chlamyphorinae is resolved by the noncoding sequence data set as the sister group of Tolypeutinae. The data provide a stable phylogenetic framework for further evolutionary investigations of Xenarthrans and important information for defining conservation priorities to save the diversity of one of the most curious groups of mammals.
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Molecular systematics of armadillos (Xenarthra, Dasypodidae): contribution of maximum likelihood and Bayesian analyses of mitochondrial and nuclear genes.
Molecular Phylogenetics and Evolution, 2003Co-Authors: Frédéric Delsuc, Michael J. Stanhope, Emmanuel DouzeryAbstract:The 30 living species of armadillos, anteaters, and sloths (Mammalia: Xenarthra) represent one of the three major clades of placentals. Armadillos (Cingulata: Dasypodidae) are the earliest and most speciose Xenarthran lineage with 21 described species. The question of their tricky phylogeny was here studied by adding two mitochondrial genes (NADH dehydrogenase subunit 1 [ND1] and 12S ribosomal RNA [12S rRNA]) to the three protein-coding nuclear genes (alpha2B adrenergic receptor [ADRA2B], breast cancer susceptibility exon 11 [BRCA1], and von Willebrand factor exon 28 [VWF]) yielding a total of 6869 aligned nucleotide sites for thirteen Xenarthran species. The two mitochondrial genes were characterized by marked excesses of transitions over transversions-with a strong bias toward CT transitions for the 12S rRNA-and exhibited two- to fivefold faster evolutionary rates than the fastest nuclear gene (ADRA2B). Maximum likelihood and Bayesian phylogenetic analyses supported the monophyly of Dasypodinae, Tolypeutinae, and Euphractinae, with the latter two armadillo subfamilies strongly clustering together. Conflicting branching points between individual genes involved relationships within the subfamilies Tolypeutinae and Euphractinae. Owing to a greater number of informative sites, the overall concatenation favored the mitochondrial topology with the classical grouping of Cabassous and Priodontes within Tolypeutinae, and a close relationship between Euphractus and Chaetophractus within Euphractinae. However, low statistical support values associated with almost equal distributions of apomorphies among alternatives suggested that two parallel events of rapid speciation occurred within these two armadillo subfamilies.
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Molecular phylogeny of living Xenarthrans and the impact of character and taxon sampling on the placental tree rooting.
Molecular Biology and Evolution, 2002Co-Authors: Frédéric Delsuc, Wilfried W. De Jong, Mark S Springer, François Catzeflis, Michael J. Stanhope, Ole Madsen, Mark Scally, Emmanuel DouzeryAbstract:Extant Xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, Xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living Xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling.
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The evolution of armadillos, anteaters and sloths depicted by nuclear and mitochondrial phylogenies: implications for the status of the enigmatic fossil Eurotamandua.
Proceedings of the Royal Society B: Biological Sciences, 2001Co-Authors: Frédéric Delsuc, François Catzeflis, Michael Stanhope, Emmanuel DouzeryAbstract:The mammalian order Xenarthra (armadillos, anteaters and sloths) is one of the four major clades of placentals, but it remains poorly studied from the molecular phylogenetics perspective. We present here a study encompassing most of the order's diversity in order to establish Xenarthrans' intra-ordinal relationships, discuss the evolution of their morphological characters, search for their extant sister group and specify the timing of their radiation with special emphasis on the status of the controversial fossil Eurotamandua. Sequences of three genes (nuclear exon 28 of the Von Willebrand factor and mitochondrial 12S and 16S rRNAs) are compared for eight of the 13 living genera. Phylogenetic analyses confirm the order's monophyly and that of its three major lineages: armadillos (Cingulata), anteaters (Vermilingua) and sloths ('Tardigrada', renamed in 'Folivora'), and our results strongly support the grouping of hairy Xenarthrans (anteaters and sloths) into Pilosa. Within placentals, Afrotheria might be the first lineage to branch off, followed by Xenarthra. The morphological adaptative convergence between New World Xenarthrans and Old World pangolins is confirmed. Molecular datings place the early emergence of armadillos around the Cretaceous/Tertiary boundary, followed by the divergence between anteaters and sloths in the Early Eocene era. These Tertiary dates contradict the concept of a very ancient origin of modern Xenarthran lineages. They also question the placement of the purported fossil anteater (Eurotamandua) from the Middle Eocene period of Europe with the Vermilingua and instead suggest the independent and convergent evolution of this enigmatic taxon.
François Pujos - One of the best experts on this subject based on the ideXlab platform.
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Phylogenetic and functional implications of the ear region anatomy of Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina.
Die Naturwissenschaften, 2018Co-Authors: Alberto Boscaini, Dawid A Iurino, German Tirao, Timothy J Gaudin, Guillaume Billet, Lionel Hautier, Raffaele Sardella, François PujosAbstract:Several detailed studies of the external morphology of the ear region in extinct sloths have been published in the past few decades, and this anatomical region has proved extremely helpful in elucidating the phylogenetic relationships among the members of this mammalian clade. Few studies of the inner ear anatomy in these peculiar animals were conducted historically, but these are increasing in number in recent years, in both the extinct and extant representatives, due to wider access to CT-scanning facilities, which allow non-destructive access to internal morphologies. In the present study, we analyze the extinct ground sloth Glossotherium robustum and provide a description of the external features of the ear region and the endocranial side of the petrosal bone, coupled with the first data on the anatomy of the bony labyrinth. Some features observable in the ear region of G. robustum (e.g., the shape and size of the entotympanic bone and the morphology of the posteromedial surface of the petrosal) are highly variable, both intraspecifically and intraindividually. The form of the bony labyrinth of G. robustum is also described, providing the first data from this anatomical region for the family Mylodontidae. The anatomy of the bony labyrinth of the genus Glossotherium is here compared at the level of the superorder Xenarthra, including all available extant and extinct representatives, using geometric morphometric methods. In light of the new data, we discuss the evolution of inner ear anatomy in the Xenarthran clade, and most particularly in sloths, considering the influence of phylogeny, allometry, and physiology on the shape of this highly informative region of the skull. These analyses show that the inner ear of Glossotherium more closely resembles that of the extant anteaters, and to a lesser extent those of the giant ground sloth Megatherium and euphractine armadillos, than those of the extant sloths Bradypus and Choloepus, further demonstrating the striking morphological convergence between the two extant sloth genera.
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Lakukullus anatisrostratus, gen. et sp. nov., a new massive nothrotheriid sloth (Xenarthra, Pilosa) from the middle Miocene of Bolivia
Journal of Vertebrate Paleontology, 2014Co-Authors: François Pujos, Gerardo De Iuliis, Bernardo Mamani Quispe, Ruben Andrade FloresAbstract:Xenarthra constitute one of the most representative groups of South American endemic mammals. The armored Cingulata is recorded beginning in the Itaboraian SALMA (lower Eocene; Pujos et al., 2012)....
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Form and Function in the Xenarthra–an Introduction to the Symposium Proceedings Volume
Journal of Mammalian Evolution, 2012Co-Authors: Timothy J Gaudin, François PujosAbstract:This special issue of the Journal of Mammalian Evolution represents the proceedings from a symposium held in conjunction with the 9th International Congress of Vertebrate Morphology (ICVM IX, Punta del Este, Uruguay, July 29, 2010), and entitled “Form and Function in the Xenarthra.” This symposium was the third on Xenarthran biology to be presented in association with the ICVM meetings. In this brief introduction to the symposium proceedings, we plan to discuss the justification for the symposium, to provide a brief history of previous symposia and their results, and to introduce the contents of the present volume.
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Nouveaux paresseux terrestres (Mammalia, Xenarthra, Mylodontidae) du Néogène de l'Altiplano bolivien
Geodiversitas, 2010Co-Authors: Pierre-antoine Saint-andre, Timothy J Gaudin, François Pujos, Gerardo De Iuliis, H. Gregory Mcdonald, Cástor Cartelle, Bernardino Mamani QuispeAbstract:ABSTRACT New ground sloths (Mammalia, Xenarthra, Mylodontidae) from the Neogene of the Bolivian Altiplano. Two new Mylodontinae (Xenarthra, Tardigrada, Mylodontoidea) from the Bolivian Altiplano are described. One of them, Pleurolestodon dalenzae n. sp., was discovered a few meters below a volcanic tuff, Toba 76, that may be used as a reference stratigraphic level and is dated at 5.4 Ma; it could be Huayquerian (late Miocene) or at the Huayquerian-Montehermosan boundary in age. The other taxon, Simomylodon uccasamamensis n. gen., n. sp., was recovered from many localities of a horizon bounded below by Toba 76 and above by another volcanic level, the 2.8 Ma Ayo Ayo tuff; its age is Montehermosan-Chapadmalalan (early and middle Pliocene). Analysis of these taxa indicates that they are Mylodontidae more closely related to Glossotherium, Glossotheridium, Kiyumylodon and Paramylodon than to Lestodon or Thinobadistes.
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A systematic reassessment and paleogeographic review of fossil Xenarthra from Peru
Bulletin de l’Institut français d’études andines, 2004Co-Authors: François Pujos, Rodolfo SalasAbstract:A revision of Peruvian Xenarthra and the discovery of new specimens have increased our knowledge of the Order in this country. About thirty sites from three geographic regions, Amazonian Forest, the Andes, and the coast have yielded Xenarthra in Peru. The only well known Pre-Pleistocene Xenarthra is Thalassocnus from the Mio-Pliocene of the Pisco Formation. Pleistocene Phyllophaga (Megatheriidae, Nothrotheriidae, Mylodontidae, and Megalonychidae) and Cingulata (Pampatheriidae and Glyptodontidae) are rare in the Amazonian forest region, abundant in the coastal region and are particularly frequent in the Andes (between 2 500 and 4 500 meters). Cingulata are not as diverse and are represented only by Holmesina cf. paulacoutoi along the coast and Glyptodon clavipes in the Andes. The mylodontid Glossotherium sp. is recognized in the entire Peruvian coast and the scelidothere Scelidodon chiliensis is abundant in both the Andes and northern coast region. Pleistocene nothrotheres are found only in the Amazonian forest region (Nothropus priscus in Rio Acre). Megatheriidae are well diversified and have an extended geographic range. The tropical genus Eremotherium (E. laurillardi) is present on the northern coast and is possibly represented in Amazonia by a gigantic form. The temperate genus Megatherium is represented in Peru by a small-sized, quadrupedal, and browser of the Andean linage of the subgenus M. (Pseudomegatherium), which includes M. (P.) tarijense, M. (P.) elenense, M. (P.) urbinai, and new species from the northern Andes. Large species of sloths such as Megatherium (Megatherium) americanum, Lestodon sp., and Scelidotherium leptocephalum that are typical of the Argentinian Pampas are absent in Peru. A peculiar new megalonychid was discovered in the north coast region (Cupisnique desert) and in the Andes near Lake Titicaca at Casa del Diablo cave. 14C dating indicates that most of fossil mammals in Peru are Lujanian in age. Along the coast and probably in Amazonia, Xenarthra are found in open localities, in contrast to the Andean region in which most specimens are preserved in caves. In Peru, and all over South America, large Xenarthra did not survive beyond the beginning of the Holocene.
