Aquatic adaptations in desmostylians

Inuzuka, Norihisa

doi:10.1080/10292380009380558

Cited by 11 publications

(21 citation statements)

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“…They notably suggested that all desmostylians show some degree of aquatic adaptation in their morphology, and that Desmostylus is much more aquatic than the other desmostylians ([16], [63] contra [60]). …”

Section: Discussionmentioning

confidence: 99%

Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)

et al. 2013

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BackgroundThe 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 FindingsWe 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/SignificanceIn 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.

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Section: Discussionmentioning

confidence: 99%

Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)

et al. 2013

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“…2), but large semiaquatic herbivores (LSH) are presently limited to the Hippopotamidae. By contrast, in the past this niche of ecosystem engineers has included representatives of mammalian groups as disparate as pantodonts (Clementz, Holroyd & Koch, 2008), anthracotheriids (Lihoreau & Ducrocq, 2007), sirenians (Domning, 2001), proboscideans (Liu, Seiffert & Simons, 2008), desmostylians (Inuzuka, 2000), xenarthrans (Muizon & McDonald, 1995), rhinocerotoids (Wall & Heinbaugh, 1999), and putatively dinomyid rodents (Sánchez‐Villagra, Aguilera & Horovitz, 2003) and extinct South American ungulates (Weston, Madden & Sánchez‐Villagra, 2004; MacFadden, 2005). LSH ecomorphs were thus found in palaeoecosystems of Eurasia, Africa, and the Americas throughout the Cenozoic.…”

Section: The Hippopotamidae a Tool To Investigate The Evolution mentioning

confidence: 99%

Evolving between land and water: key questions on the emergence and history of the Hippopotamidae (Hippopotamoidea, Cetancodonta, Cetartiodactyla)

et al. 2010

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The fossil record of the Hippopotamidae can shed light on three major issues in mammalian evolution. First, as the Hippopotamidae are the extant sister group of Cetacea, gaining a better understanding of the origin of the Hippopotamidae and of their Paleogene ancestors will be instrumental in clarifying phylogenetic relationships within Cetartiodactyla. Unfortunately, the data relevant to hippopotamid origins have generally been ignored in phylogenetic analyses of cetartiodactyls. In order to obtain better resolution, future analyses should consider hypotheses of hippopotamid Paleogene relationships. Notably, an emergence of the Hippopotamidae from within anthracotheriids has received growing support, leading to reconciliation between genetic and morphological evidence for the clade Cetancodonta (Hippopotamidae + Cetacea). Secondly, full account needs to be taken of the Hippopotamidae when studying the impact of environmental change on faunal evolution. This group of semi-aquatic large herbivores has a clear and distinct ecological role and a diverse and abundant fossil record, particularly in the African Neogene. We examine three major phases of hippopotamid evolution, namely the sudden appearance of hippopotamines in the late Miocene (the "Hippopotamine Event"), the subsequent rampant endemism in African basins, and the Pleistocene expansion of Hippopotamus. Each may have been influenced by multiple factors, including: late Miocene grass expansion, African hydrographical network disruption, and a unique set of adaptations that allowed Hippopotamus to respond efficiently to early Pleistocene environmental change. Thirdly, the fossil record of the Hippopotamidae documents the independent emergence of adaptive character complexes in relation to semiaquatic habits and in response to insular isolation. The semiaquatic specializations of fossil hippopotamids are particularly useful in interpreting the functional morphology and ecology of other, extinct groups of large semiaquatic herbivores. Hippopotamids can also serve as models to elucidate the evolutionary dynamics of island mammals.

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“…Their feet are not modified enough for swimming (Howell ; Fish ; Eltringham ; Coughlin & Fish ). They were seldom observed losing contact with river and lake bottoms; instead, they preferentially walk underwater rather than swim (Klingel ; Eltringham ; Nowak ; Inuzuka ; Fisher et al . ; Coughlin & Fish ).…”

Section: Hippopotamuses’ Aquatic Locomotion and Life Habitsmentioning

confidence: 99%

“…Their feet are not modified enough for swimming (Howell 1930;Fish 1993;Eltringham 1999;Coughlin & Fish 2009). They were seldom observed losing contact with river and lake bottoms; instead, they preferentially walk underwater rather than swim (Klingel 1991;Eltringham 1999;Nowak 1999;Inuzuka 2000;Fisher et al 2007;Coughlin & Fish 2009). When they lose contact with the bottom, they actually gallop short distances with brief unsupported intervals (they 'walk on the bottom.…”

Section: Hippopotamuses' Aquatic Locomotion and Life Habitsmentioning

confidence: 99%

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If hippopotamuses cannot swim, how did they colonize islands?

Mazza

2014

LET

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. 2014: If Hippopotamuses cannot swim, how did they colonize islands?. Lethaia, Vol. 47, Owing to their aquatic lifestyle, hippopotamuses are normally believed to have reached islands by swimming. Yet, some studies suggest they cannot swim due to their relatively high density. If so, this raises the question of how hippopotamuses would have reached some islands. Their immigration into the British Isles, Sicily, Malta, Zanzibar and Mafia can be accounted for, because these islands sit on continental shelves and were often linked to the mainland during the Pleistocene glacio-eustatic sea-level falls. In contrast, their occurrence in Crete, Cyprus and Madagascar would be more difficult to explain. Available geological evidence does not seem to rule out that the latter islands might have been connected with the nearest mainland areas in very recent times. This study intends to consider possibilities about how hippopotamuses reached islands and to show that more effective collaboration is required among specialists involved with the study of insular evolution, colonization and speciation. □ Dispersal events, extra-Mediterranean islands, glacio-eustatic sea-level excursions, Mediterranean islands, Pleistocene.

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Aquatic adaptations in desmostylians

Cited by 11 publications

References 5 publications

Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)

Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)

Evolving between land and water: key questions on the emergence and history of the Hippopotamidae (Hippopotamoidea, Cetancodonta, Cetartiodactyla)

If hippopotamuses cannot swim, how did they colonize islands?

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