1. Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)
- Author
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Hiroshi Sawamura, Naotomo Kaneko, Tomohiro Osaki, Shoji Hayashi, Alexandra Houssaye, Kentaro Chiba, Yasuhisa Nakajima, Tatsuro Ando, Norihisa Inuzuka, Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Osaka Museum of Natural History, Centre de Recherche en Paléontologie - Paris (CR2P), Muséum national d'Histoire naturelle (MNHN)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), The University of Tokyo (UTokyo), Hokkaido University [Sapporo, Japan], Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), and Tottori University
- Subjects
0106 biological sciences ,010506 paleontology ,Anatomy and Physiology ,Science ,Animal Types ,Vertebrate Paleontology ,010603 evolutionary biology ,01 natural sciences ,Bone and Bones ,Desmostylia ,Paleontology ,Animals ,14. Life underwater ,Vertebrate paleontology ,Bone ,Biology ,Musculoskeletal System ,Phylogeny ,0105 earth and related environmental sciences ,Mammals ,Evolutionary Biology ,Principal Component Analysis ,Multidisciplinary ,biology ,biology.organism_classification ,Adaptation, Physiological ,Evolutionary biology ,Paleoecology ,Earth Sciences ,Medicine ,Veterinary Science ,Adaptation ,Paleobiology ,[SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology ,Afrotheria ,Research Article ,Aquatic Animals - Abstract
International audience; Background: The paleoecology of desmostylians has been discussed controversially with a general consensus that desmostylians were aquatic or semi-aquatic to some extent. Bone microanatomy can be used as a powerful tool to infer habitat preference of extinct animals. However, bone microanatomical studies of desmostylians are extremely scarce.Methodology/Principal Findings: We analyzed the histology and microanatomy of several desmostylians using thin-sections and CT scans of ribs, humeri, femora and vertebrae. Comparisons with extant mammals allowed us to better understand the mode of life and evolutionary history of these taxa. Desmostylian ribs and long bones generally lack a medullary cavity. This trait has been interpreted as an aquatic adaptation among amniotes. Behemotops and Paleoparadoxia show osteosclerosis (i.e. increase in bone compactness), and Ashoroa pachyosteosclerosis (i.e. combined increase in bone volume and compactness). Conversely, Desmostylus differs from these desmostylians in displaying an osteoporotic-like pattern.Conclusions/Significance: In living taxa, bone mass increase provides hydrostatic buoyancy and body trim control suitable for poorly efficient swimmers, while wholly spongy bones are associated with hydrodynamic buoyancy control in active swimmers. Our study suggests that all desmostylians had achieved an essentially, if not exclusively, aquatic lifestyle. Behemotops, Paleoparadoxia and Ashoroa are interpreted as shallow water swimmers, either hovering slowly at a preferred depth, or walking on the bottom, and Desmostylus as a more active swimmer with a peculiar habitat and feeding strategy within Desmostylia. Therefore, desmostylians are, with cetaceans, the second mammal group showing a shift from bone mass increase to a spongy inner organization of bones in their evolutionary history.
- Published
- 2013