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Lionel Hautier - 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, Lionel Hautier, Raffaele Sardella, Guillaume Billet, 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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patterns of morphological variation of extant Sloth skulls and their implication for future conservation efforts
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2014Co-Authors: Lionel Hautier, Guillaume Billet, Bethany Eastwood, Jemima LaneAbstract:Several studies have shown an increased morphological variability of Sloths from mammalian norms, affecting varied phenotypic traits from skeletal parts to soft tissues. We present here the first descriptive comparison of the whole skull morphology within the two extant Sloth genera, combining geometric morphometric approaches with comparative anatomy. We used these methods to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as phylogeny, geography, allometry, or sexual dimorphism. Our study first revealed strong phylogenetic and geographical imprints on the cranial and mandibular morphological traits. This result demonstrates the importance of accurate knowledge of species and their geographical distributions; here we show from an example pertaining to Bradypus variegatus populations the implications this has on conservation management. Moreover, in order to control the amount of this detected variation, we tentatively compared Sloths to a wide range of mammalian species. Our analysis found no significant increase in the average deviation of skull shape within each investigated Sloth species compared to other mammals. This suggests that the intraspecific cranial variation in Sloths does not depart significantly from the variation observed in other mammals. This result has positive implications for the demarcation of anatomical regions that maintain high levels of morphological variation in Sloths. Anat Rec, 297:979–1008, 2014. © 2014 Wiley Periodicals, Inc.
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the inner ear of megatherium and the evolution of the vestibular system in Sloths
Journal of Anatomy, 2013Co-Authors: Guillaume Billet, Lionel Hautier, Damien Germain, Irina Ruf, C De MuizonAbstract:Extant tree Sloths are uniquely slow mammals with a very specialized suspensory behavior. To improve our understanding of their peculiar evolution, we investigated the inner ear morphology of one of the largest and most popular fossil ground Sloths, Megatherium americanum. We first address the predicted agility of this animal from the scaling of its semicircular canals (SC) relative to body mass, based on recent work that provided evidence that the size of the SC in mammals correlates with body mass and levels of agility. Our analyses predict intermediate levels of agility for Megatherium, contrasting with the extreme slowness of extant Sloths. Secondly, we focus on the morphology of the SC at the inner ear scale and investigate the shape and proportions of these structures in Megatherium and in a large diversity of extant xenarthrans represented in our database. Our morphometric analyses demonstrate that the giant ground Sloth clearly departs from the SC morphology of both extant Sloth genera (Choloepus, Bradypus) and is in some aspects closer to that of armadillos and anteaters. Given the close phylogenetic relationships of Megatherium with the extant genus Choloepus, these results are evidence of substantial homoplasy of the SC anatomy in Sloths. This homoplasy most likely corresponds to an outstanding convergent evolution between extant suspensory Sloth genera.
Timothy J Gaudin - One of the best experts on this subject based on the ideXlab platform.
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cranial anatomy and paleoneurology of the extinct Sloth catonyx tarijensis xenarthra mylodontidae from the late pleistocene of oruro southwestern bolivia
Frontiers in Ecology and Evolution, 2020Co-Authors: Alberto Boscaini, Dawid A Iurino, François Pujos, Raffaele Sardella, Bernardino Mamani Quispe, Ruben Andrade Flores, Timothy J GaudinAbstract:Extinct scelidotheriine Sloths are among the most peculiar fossil mammals from South America. In recent decades, the external cranial anatomy of Pleistocene scelidotheres such as Scelidotherium, Catonyx and Valgipes has been the subject of numerous studies, but their endocranial anatomy remains almost completely unknown. Today, computed tomographic (CT) scanning methodologies permit the exploration of previously inaccessible anatomical areas through a completely non-destructive process. For this reason, we undertook an analysis of the external and internal cranial anatomy of Catonyx tarijensis from the late Pleistocene of the Department of Oruro, in southwestern Bolivia. One particularly well preserved specimen allowed detailed observation of all the main cranial osteological features, including the ear region and an almost complete hyoid apparatus, previously unknown for this taxon. Moreover, CT-scanning and subsequent elaboration of digital models of this specimen allowed observation of the brain cavity and cranial sinuses, and reconstruction of the trajectory of the main cranial nerves for the first time in an extinct scelidotheriine Sloth. Additionally, we recovered the first three-dimensional reconstructions of the nasal cavity and the turbinates of an extinct Sloth. In contrast to the usual depiction, the combined information from the external and internal anatomy suggests reduced lingual protrusion in Catonyx tarijensis, or at least a consistently more limited protrusion of the tongue in comparison with other mylodontid Sloths such as Glossotherium robustum. The new morphological information recovered from this extinct Sloth is compared with the available information for both extant and extinct forms, providing insights in the paleobiology of the extinct species. The present study reveals the importance of applying these novel non-destructive techniques to elucidate the evolutionary history of Sloths. The new morphological information recovered from this extinct Sloth is compared with the available information for both extant and extinct forms, providing insights in the paleobiology of the extinct species. The present study reveals the importance of applying these novel non-destructive techniques our efforts to elucidate the evolutionary history of Sloths.
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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, Lionel Hautier, Raffaele Sardella, Guillaume Billet, 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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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.
Yanming Liu - One of the best experts on this subject based on the ideXlab platform.
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design of a low sll siw slot array antenna with a large declination in ka band
IEEE Access, 2019Co-Authors: Chengwei Zhao, Chao Sun, He Huang, Yanming LiuAbstract:A small-size large-declination longitudinal slot array antenna based on substrate integrated waveguide (SIW) technology was proposed. Compared with the conventional SIW slot array, the proposed antenna achieves a larger declination and a lower SLL. The antenna is mainly composed of three parts, a dielectric substrate, a coaxial port, and a matched load. The antenna contains 13 radiation slots, and the adjacent slot spacing is greater than half of the waveguide wavelength, so the main beam is biased towards the load. To achieve low sidelobe levels (SLL), the amplitude distribution of the 13 slots is based on Taylor synthesis of SLL = -25 dB. The antenna was processed and measured. From the measured results, the antenna achieved a beam declination of 26° and a SLL below -20 dB from 35.2 to 35.8 GHz. With the same number of slots, the length of the slot array of the SIW structure is only 44.8% of the length of the standard metal hollow waveguide. Based on the performance achieved, the SIW slot antenna is an excellent candidate for carrier conformal and large declination applications.
H. Gregory Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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Ancient Mitogenomes Reveal the Evolutionary History and Biogeography of Sloths
Current Biology - CB, 2019Co-Authors: Frédéric Delsuc, H. Gregory Mcdonald, Melanie Kuch, Gillian C. Gibb, Emil Karpinski, Dirk Hackenberger, Paul Szpak, Jorge G. Martínez, Jim I. Mead, Ross D. E. MacpheeAbstract:Living Sloths represent two distinct lineages of small-sized mammals that independently evolved arboreality from terrestrial ancestors. The six extant species are the survivors of an evolutionary radiation marked by the extinction of large terrestrial forms at the end of the Quaternary. Until now, Sloth evolutionary history has mainly been reconstructed from phylogenetic analyses of morphological characters. Here, we used ancient DNA methods to successfully sequence 10 extinct Sloth mitogenomes encompassing all major lineages. This includes the iconic continental ground Sloths Megatherium, Megalonyx, Mylodon, and Nothrotheriops and the smaller endemic Caribbean Sloths Parocnus and Acratocnus. Phylogenetic analyses identify eight distinct lineages grouped in three well-supported clades, whose interrelationships are markedly incongruent with the currently accepted morphological topology. We show that recently extinct Caribbean Sloths have a single origin but comprise two highly divergent lineages that are not directly related to living two-fingered Sloths, which instead group with Mylodon. Moreover, living three-fingered Sloths do not represent the sister group to all other Sloths but are nested within a clade of extinct ground Sloths including Megatherium, Megalonyx, and Nothrotheriops. Molecular dating also reveals that the eight newly recognized Sloth families all originated between 36 and 28 million years ago (mya). The early divergence of recently extinct Caribbean Sloths around 35 mya is consistent with the debated GAARlandia hypothesis postulating the existence at that time of a biogeographic connection between northern South America and the Greater Antilles. This new molecular phylogeny has major implications for reinterpreting Sloth morphological evolution, biogeography, and diversification history.
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An Overview of the Presence of Osteoderms in Sloths: Implications for Osteoderms as a Plesiomorphic Character of the Xenarthra
Journal of Mammalian Evolution, 2018Co-Authors: H. Gregory McdonaldAbstract:The presence of osteoderms in the skin of some extinct Sloths and in cingulates (armadillos, pampatheres, and glyptodonts) has often been considered a pleisomorphic character of the Xenarthra. While osteoderms are known from the earliest cingulates, they are absent in most Sloths including the two extant taxa and only appear late in their fossil record. Osteoderms are currently only reported from five genera of mylodonts and two megatheres, out of the over 100 currently recognized genera of Sloths. Consequently, rather than a plesiomorphic character of the Xenarthra, which has been secondarily lost in Sloths, it is more likely that osteoderms in Sloths are the result of parallel evolution to the cingulates that independently evolved in one, possibly two different Sloth clades.
Guillaume Billet - 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, Lionel Hautier, Raffaele Sardella, Guillaume Billet, 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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patterns of morphological variation of extant Sloth skulls and their implication for future conservation efforts
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2014Co-Authors: Lionel Hautier, Guillaume Billet, Bethany Eastwood, Jemima LaneAbstract:Several studies have shown an increased morphological variability of Sloths from mammalian norms, affecting varied phenotypic traits from skeletal parts to soft tissues. We present here the first descriptive comparison of the whole skull morphology within the two extant Sloth genera, combining geometric morphometric approaches with comparative anatomy. We used these methods to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as phylogeny, geography, allometry, or sexual dimorphism. Our study first revealed strong phylogenetic and geographical imprints on the cranial and mandibular morphological traits. This result demonstrates the importance of accurate knowledge of species and their geographical distributions; here we show from an example pertaining to Bradypus variegatus populations the implications this has on conservation management. Moreover, in order to control the amount of this detected variation, we tentatively compared Sloths to a wide range of mammalian species. Our analysis found no significant increase in the average deviation of skull shape within each investigated Sloth species compared to other mammals. This suggests that the intraspecific cranial variation in Sloths does not depart significantly from the variation observed in other mammals. This result has positive implications for the demarcation of anatomical regions that maintain high levels of morphological variation in Sloths. Anat Rec, 297:979–1008, 2014. © 2014 Wiley Periodicals, Inc.
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the inner ear of megatherium and the evolution of the vestibular system in Sloths
Journal of Anatomy, 2013Co-Authors: Guillaume Billet, Lionel Hautier, Damien Germain, Irina Ruf, C De MuizonAbstract:Extant tree Sloths are uniquely slow mammals with a very specialized suspensory behavior. To improve our understanding of their peculiar evolution, we investigated the inner ear morphology of one of the largest and most popular fossil ground Sloths, Megatherium americanum. We first address the predicted agility of this animal from the scaling of its semicircular canals (SC) relative to body mass, based on recent work that provided evidence that the size of the SC in mammals correlates with body mass and levels of agility. Our analyses predict intermediate levels of agility for Megatherium, contrasting with the extreme slowness of extant Sloths. Secondly, we focus on the morphology of the SC at the inner ear scale and investigate the shape and proportions of these structures in Megatherium and in a large diversity of extant xenarthrans represented in our database. Our morphometric analyses demonstrate that the giant ground Sloth clearly departs from the SC morphology of both extant Sloth genera (Choloepus, Bradypus) and is in some aspects closer to that of armadillos and anteaters. Given the close phylogenetic relationships of Megatherium with the extant genus Choloepus, these results are evidence of substantial homoplasy of the SC anatomy in Sloths. This homoplasy most likely corresponds to an outstanding convergent evolution between extant suspensory Sloth genera.
