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Gaudin TJ, Scaife T. Cranial osteology of a juvenile specimen of Acratocnus ye (Mammalia, Xenarthra, Folivora) and its ontogenetic and phylogenetic implications. Anat Rec (Hoboken) 2023; 306:607-637. [PMID: 36054593 DOI: 10.1002/ar.25062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/18/2022] [Accepted: 08/18/2022] [Indexed: 11/09/2022]
Abstract
The present study comprises a description of the skull and jaw anatomy of a juvenile specimen of the Antillean sloth Acratocnus ye, from the Holocene of Haiti. Detailed descriptions and illustrations are provided of the skull bones and their sutural connections, which normally fuse in adults. Descriptions are also provided for the mandible and ear ossicles, as well as endocranial surfaces and sinuses exposed by breaks. The anatomy of our juvenile A. ye is compared to that of adult A. ye to assess ontogenetic changes in the skull. Several of these ontogenetic features are significant new observations that impact the relationships within Xenarthra as a whole, or between Xenarthrans and other placental mammals, most notably, the presence of a separate mesethmoid element, the presence of alveoli for a lower deciduous canine and anterior incisor, and the presence of separate rostral and caudal entotympanic elements. A full list of such changes are provided. In addition, the specimen provides information on phylogenetically relevant characters, including features unique to the genus Acratocnus, and features of the clade Choloepodini, including Acratocnus, the smaller extinct Antillean sloth Neocnus, and the extant two-toed sloth Choloepus. Contrary to previous studies, Acratocnus shares as many features with Choloepus as it does with its fellow Antillean form Neocnus in the present study, which is consistent with current morphology-based phylogenetic hypotheses regarding the relationships within Choloepodini. The current study highlights the need for further anatomical and phylogenetic investigations of Antillean sloths (Megalocnidae/Megalonychidae), and juvenile sloths in general.
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Affiliation(s)
- Timothy J Gaudin
- Department of Biology, Geology & Environmental Science, University of Tennessee at Chattanooga, Chattanooga, Tennessee, USA
| | - Thomas Scaife
- Department of Geosciences, East Tennessee State University, Johnson City, Tennessee, USA
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3
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Toledo N, Boscaini A, Pérez LM. The dermal armor of mylodontid sloths (Mammalia, Xenarthra) from Cueva del Milodón (Última Esperanza, Chile). J Morphol 2021; 282:612-627. [PMID: 33569815 DOI: 10.1002/jmor.21333] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/30/2021] [Accepted: 02/07/2021] [Indexed: 11/08/2022]
Abstract
Dermal ossifications (osteoderms, dermal ossicles, osteoscutes) appear independently in various tetrapod lineages. In mammals, however, dermal ossifications are only present in some members of Xenarthra. This clade includes Cingulata (armadillos and their relatives), and Pilosa, including Vermilingua (anteaters) and Folivora (sloths). In extant xenarthrans, osteoderms are invariably present in cingulates whereas they are absent in pilosans. Among extinct sloths, however, a limited number of taxa possessed dermal ossifications. Records of mummified skins of ground sloths bearing osteoderms found in Cueva del Milodón (Southern Chile), with a late Pleistocene age, allowed us to analyze their micro- and macroscopic morphology. The main goal of this study is to closely examine a portion of a mylodontid skin portion using radiography. The arrangement, morphology and internal structure of the ossicles are analyzed and the results are discussed in the context of previous research. The results we obtained indicate that ossicles vary in shape and size, and the integument has four different patterns of arrangement of the ossicles: that is, areas without ossicles, disorganized ossicles, rows, and mosaic areas. The latter has two variants, with clusters of ossicles forming rosettes or stars. Thin sections of the ossicles allowed us to recognize and describe anatomical features of the bone and its mode of growth. Finally, paleobiological and functional considerations of the dermal armor are discussed along with its phylogenetic and chronological implications.
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Affiliation(s)
- Néstor Toledo
- División Paleontología Vertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata (UNLP), Av. 60 and 122, La Plata, Buenos Aires, B1900FWA, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas - CONICET, Ciudad Autónoma de Buenos Aires, Argentina
| | - Alberto Boscaini
- Consejo Nacional de Investigaciones Científicas y Técnicas - CONICET, Ciudad Autónoma de Buenos Aires, Argentina.,Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA-CONICET), DEGE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (UBA), Int. Guiraldes 2160, Ciudad Autónoma de Buenos Aires, C1428EGA, Argentina
| | - Leandro Martín Pérez
- Consejo Nacional de Investigaciones Científicas y Técnicas - CONICET, Ciudad Autónoma de Buenos Aires, Argentina.,División Paleozoología Invertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata (UNLP), Av. 60 and 122, La Plata, Buenos Aires, B1900FWA, Argentina
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Presslee S, Slater GJ, Pujos F, Forasiepi AM, Fischer R, Molloy K, Mackie M, Olsen JV, Kramarz A, Taglioretti M, Scaglia F, Lezcano M, Lanata JL, Southon J, Feranec R, Bloch J, Hajduk A, Martin FM, Salas Gismondi R, Reguero M, de Muizon C, Greenwood A, Chait BT, Penkman K, Collins M, MacPhee RDE. Palaeoproteomics resolves sloth relationships. Nat Ecol Evol 2019; 3:1121-1130. [PMID: 31171860 DOI: 10.1038/s41559-019-0909-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 04/28/2019] [Indexed: 01/16/2023]
Abstract
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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Affiliation(s)
- Samantha Presslee
- Department of Archaeology and BioArCh, University of York, Heslington, UK.,Department of Mammalogy, American Museum of Natural History, New York, NY, USA.,Paleoproteomics Group, Natural History Museum of Denmark and University of Copenhagen, Copenhagen, Denmark
| | - Graham J Slater
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
| | - François Pujos
- Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CCT-CONICET-Mendoza, Mendoza, Argentina
| | - Analía M Forasiepi
- Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CCT-CONICET-Mendoza, Mendoza, Argentina
| | - Roman Fischer
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Kelly Molloy
- Chait Laboratory and National Resource for the Mass Spectrometric Analysis of Biological Macromolecules, The Rockefeller University, New York, NY, USA
| | - Meaghan Mackie
- Paleoproteomics Group, Natural History Museum of Denmark and University of Copenhagen, Copenhagen, Denmark.,Novo Nordisk Foundation Center for Protein Research, Copenhagen, Denmark
| | - Jesper V Olsen
- Novo Nordisk Foundation Center for Protein Research, Copenhagen, Denmark
| | - Alejandro Kramarz
- Sección Paleovertebrados, Museo Argentino de Ciencias Naturales 'Bernardino Rivadavia', Buenos Aires, Argentina
| | - Matías Taglioretti
- Museo Municipal de Ciencias Naturales 'Lorenzo Scaglia', Mar del Plata, Argentina
| | - Fernando Scaglia
- Museo Municipal de Ciencias Naturales 'Lorenzo Scaglia', Mar del Plata, Argentina
| | - Maximiliano Lezcano
- Instituto de Investigaciones en Diversidad Cultural y Procesos de Cambio, CONICET and Universidad Nacional de Río Negro, Bariloche, Argentina
| | - José Luis Lanata
- Instituto de Investigaciones en Diversidad Cultural y Procesos de Cambio, CONICET and Universidad Nacional de Río Negro, Bariloche, Argentina
| | - John Southon
- Keck-CCAMS Group, Earth System Science Department, University of California, Irvine, Irvine, CA, USA
| | | | - Jonathan Bloch
- Florida Museum of Natural History, University of Florida, Gainesville, FL, USA
| | - Adam Hajduk
- Museo de la Patagonia 'F. P. Moreno', Bariloche, Argentina
| | - Fabiana M Martin
- Centro de Estudios del Hombre Austral, Instituto de la Patagonia, Universidad de Magallanes, Punta Arenas, Chile
| | - Rodolfo Salas Gismondi
- BioGeoCiencias Lab, Facultad de Ciencias y Filosofía/CIDIS, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Marcelo Reguero
- CONICET and División Paleontología de Vertebrados, Museo de La Plata. Facultad de Ciencias Naturales, Universidad Nacional de La Plata, La Plata, Argentina
| | - Christian de Muizon
- Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, Muséum national d'Histoire naturelle, Paris, France
| | - Alex Greenwood
- Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany.,Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Brian T Chait
- Chait Laboratory and National Resource for the Mass Spectrometric Analysis of Biological Macromolecules, The Rockefeller University, New York, NY, USA
| | - Kirsty Penkman
- Department of Chemistry, University of York, Heslington, UK
| | - Matthew Collins
- Paleoproteomics Group, Natural History Museum of Denmark and University of Copenhagen, Copenhagen, Denmark.,McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK
| | - Ross D E MacPhee
- Department of Mammalogy, American Museum of Natural History, New York, NY, USA.
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Boscaini A, Gaudin TJ, Toledo N, Quispe BM, Antoine PO, Pujos F. The earliest well-documented occurrence of sexual dimorphism in extinct sloths: evolutionary and palaeoecological insights. Zool J Linn Soc 2019. [DOI: 10.1093/zoolinnean/zlz011] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Sexual 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.
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Affiliation(s)
- Alberto Boscaini
- Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CCT-CONICET-Mendoza, Parque Gral. San Martín, Mendoza, Argentina
| | - Timothy J Gaudin
- Department of Biology, Geology, and Environmental Science, University of Tennessee at Chattanooga, Chattanooga TN, USA
| | - Néstor Toledo
- División Paleontología Vertebrados, Museo de La Plata, Unidades de Investigación Anexo Museo, La Plata, Argentina
| | - Bernardino Mamani Quispe
- Departamento de Paleontología, Museo Nacional de Historia Natural de Bolivia, Cota Cota, La Paz, Bolivia
| | - Pierre-Olivier Antoine
- Institut des Sciences de l’Évolution de Montpellier, cc64, CNRS, Univ. Montpellier, IRD, EPHE, Montpellier, France
| | - François Pujos
- Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CCT-CONICET-Mendoza, Parque Gral. San Martín, Mendoza, Argentina
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