Intervertebral and Epiphyseal Fusion in the Postnatal Ontogeny of Cetaceans and Terrestrial Mammals

Moran, Meghan M.; Bajpai, Sunil; George, J. C.; Suydam, Robert; Usip, Sharon; Thewissen, J. G. M.

doi:10.1007/s10914-014-9256-7

Cited by 37 publications

(22 citation statements)

References 47 publications

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“…Its relatively large size (condylobasal length = 1180 mm; bizygomatic width = 460 mm) and firmly attached vertebral epiphyses identify the specimen as an adult (Moran et al. ).…”

Section: Resultsmentioning

confidence: 99%

How whales used to filter: exceptionally preserved baleen in a Miocene cetotheriid

et al. 2017

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Baleen is a comb‐like structure that enables mysticete whales to bulk feed on vast quantities of small prey, and ultimately allowed them to become the largest animals on Earth. Because baleen rarely fossilises, extremely little is known about its evolution, structure and function outside the living families. Here we describe, for the first time, the exceptionally preserved baleen apparatus of an entirely extinct mysticete morphotype: the Late Miocene cetotheriid, Piscobalaena nana, from the Pisco Formation of Peru. The baleen plates of P. nana are closely spaced and built around relatively dense, fine tubules, as in the enigmatic pygmy right whale, Caperea marginata. Phosphatisation of the intertubular horn, but not the tubules themselves, suggests in vivo intertubular calcification. The size of the rack matches the distribution of nutrient foramina on the palate, and implies the presence of an unusually large subrostral gap. Overall, the baleen morphology of Piscobalaena likely reflects the interacting effects of size, function and phylogeny, and reveals a previously unknown degree of complexity in modern mysticete feeding evolution.

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“…Its relatively large size (condylobasal length = 1180 mm; bizygomatic width = 460 mm) and firmly attached vertebral epiphyses identify the specimen as an adult (Moran et al. ).…”

Section: Resultsmentioning

confidence: 99%

How whales used to filter: exceptionally preserved baleen in a Miocene cetotheriid

et al. 2017

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“…Preliminary data were also collected on fetal centrum ossification size and density, based on the observation of Moran and Thewissen (2014) of enlarged ossifications at possible sacral locations. We found no consistent pattern of ossification in the limited number of fetal growth series that we were able to assemble.…”

Section: Sacral Locationmentioning

confidence: 99%

Finding sacral: Developmental evolution of the axial skeleton of odontocetes (Cetacea)

Buchholtz

Gee

2017

Evolution and Development

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Axial morphology was dramatically transformed during the transition from terrestrial to aquatic environments by archaeocete cetaceans, and again during the subsequent odontocete radiation. Here, we reconstruct the sequence of developmental events that underlie these phenotypic transitions. Archaeocete innovations include the loss of primaxial/abaxial interaction at the sacral/pelvic articulation and the modular dissociation of the fluke from the remainder of the tail. Odontocetes subsequently integrated lumbar, sacral, and anterior caudal vertebrae into a single torso module, and underwent multiple series-specific changes in vertebral count. The conservation of regional proportions despite regional fluctuations in count strongly argues that rates of somitogenesis can vary along the column and that segmentation was dissociated from regionalization during odontocete evolution. Conserved regional proportions also allow the prediction of the location and count of sacral homologs within the torso module. These predictions are tested with the analysis of comparative pudendal nerve root location and geometric morphometrics. We conclude that the proportion of the column represented by the sacral series has been conserved, and that its vertebrae have changed in count and relative centrum length in parallel with other torso vertebrae. Although the sacral series of odontocetes is de-differentiated, it is not de-regionalized.

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“…At this point, no further growth in length is possible. The fact that different epiphyses fuse at very different times, often multiple years apart in many species, [13][14][15] is not explained by basic physiology. 11,12 The reason why growth occurs at the ends of long bones is linked to the nature of the material.…”

Section: Why Stu D Y Ep I P H Yse Al F U Si On?mentioning

confidence: 99%

“…However, understanding the remaining factors of how this fits into a system of growth and remodeling in mammalian bone is more complex. The fact that different epiphyses fuse at very different times, often multiple years apart in many species, [13][14][15] is not explained by basic physiology. In fact, it would seem that there is no reason why these growth centers should not remain unfused until the end of growth, given that epiphyseal plates are thought to be an adaptation for joint stability.…”

Section: Why Stu D Y Ep I P H Yse Al F U Si On?mentioning

confidence: 99%

The enigmatic relationship between epiphyseal fusion and bone development in primates

Brimacombe

2017

Evolutionary Anthropology

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Epiphyseal fusion in primates is a process that occurs in a regular sequence spanning a period of years and thus provides biological anthropologists with a useful marker of maturity that can be used to assess age and stage of development. Despite the many studies that have catalogued fusion timing and sequence pattern, comparatively little research has been devoted to understanding why these sequences exist in the first place. Answering this question is not necessarily intuitive; indeed, given that neither taxonomic affinities nor recent adaptations have been clearly defined, it is a challenge to explain this process in evolutionary terms. In all mammals, there is a tendency for the fusion of epiphyses at joints to occur close in sequence, and this has been proposed to relate to locomotor adaptations. Further consideration of the evidence suggests that linking locomotor behavior to sequence data alone is difficult to prove and may require a different type of evidence. Epiphyseal fusion should be considered in the context of other parameters that affect the developing skeleton, including how joint morphology relates to growth in length, as well as other possible morphological constraints. In recent years, developmental biology has been providing a better understanding of the molecular regulators of epiphyseal fusion. At some point in the near future, we may be able to link our understanding of the genetics of fusion timing to the possible selective mechanisms that are responsible for these sequences.

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Intervertebral and Epiphyseal Fusion in the Postnatal Ontogeny of Cetaceans and Terrestrial Mammals

Cited by 37 publications

References 47 publications

How whales used to filter: exceptionally preserved baleen in a Miocene cetotheriid

How whales used to filter: exceptionally preserved baleen in a Miocene cetotheriid

Finding sacral: Developmental evolution of the axial skeleton of odontocetes (Cetacea)

The enigmatic relationship between epiphyseal fusion and bone development in primates

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