Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by a Large Macrophagous Dolphin from the Oligocene of South Carolina

Boessenecker, Robert W.; Churchill, Morgan; Buchholtz, Emily A.; Beatty, Brian L.; Geisler, Jonathan H.

doi:10.1016/j.cub.2020.06.012

Cited by 25 publications

(37 citation statements)

References 33 publications

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“…Raptorial feeding is one of the drivers for the independent evolution of large body sizes in different clades. This is further evidenced by the earliest inferred raptorial feeder, Ankylorhiza tiedemani , which is considered to be the largest Oligocene odontocete with an estimated body length of 4.8 m ( 57 ), and in the extant delphinid O. orca . The evolution of echolocation, which allowed odontocetes to forage at greater depths in search of cephalopods unavailable to early cetaceans lacking a biosonar, is not directly coupled with evolution of size.…”

Section: Implications For Body-size Evolution Of Marine Amniotesmentioning

confidence: 98%

Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans

Sander

Griebeler

Klein

et al. 2021

Science

416

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Early marine giant The largest animals to have ever lived occupied the marine environment. Modern cetaceans evolved their large size over tens of millions of years in response to the increased productivity of cold marine waters. However, whales were not the first marine giants to evolve. Sander et al . describe a 244-million-year-old fossil ichthyosaur that would have rivaled modern cetaceans in size (see the Perspective by Delsett and Pyenson). The animal existed at most 8 million years after the emergence of the first ichthyosaurs, suggesting a much more rapid size expansion that may have been fueled by processes after the Permian mass extinction. —SNV

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Section: Implications For Body-size Evolution Of Marine Amniotesmentioning

confidence: 98%

Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans

Sander

Griebeler

Klein

et al. 2021

Science

416

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“…Numerous morphological features related to raptorial feeding and hydrodynamic locomotion also appear to have evolved independently in the three extant families of Pinnipedia [101]. In Cetacea, multiple cranial and postcranial specializations for an aquatic lifestyle (e.g., shortened humerus, loss of radial tuberosity, reduction/loss of hindlimbs, posterior migration of the blowhole, cranial ‘telescoping’) evolved convergently in odontocetes and mysticetes [1,102,103]. Morphological characters preserved in fossils and pseudogenic remnants of formerly functional genes provide complementary sources of evidence for elucidating such cases of convergent or parallel evolution.…”

Section: Resultsmentioning

confidence: 99%

Genomic and anatomical comparisons of skin support independent adaptation to life in water by cetaceans and hippos

Springer¹,

Guerrero‐Juarez²,

Huelsmann

et al. 2020

Preprint

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SUMMARYThe macroevolutionary transition from terra firma to obligatory inhabitance of the marine hydrosphere has occurred twice in the history of Mammalia: Cetacea and Sirenia. In the case of Cetacea (whales, dolphins, porpoises), molecular phylogenies provide unambiguous evidence that fully aquatic cetaceans and semiaquatic hippopotamids (hippos) are each other’s closest living relatives. Ancestral reconstructions further suggest that some adaptations to the aquatic realm evolved in the common ancestor of Cetancodonta (Cetacea+Hippopotamidae). An alternative hypothesis is that these adaptations evolved independently in cetaceans and hippos. Here, we focus on the integumentary system and evaluate these hypotheses by integrating new histological data for cetaceans and hippos, the first genome-scale data for pygmy hippopotamus, and comprehensive genomic screens and molecular evolutionary analyses for protein-coding genes that have been inactivated in hippos and cetaceans. We identified ten skin-related genes that are inactivated in both cetaceans and hippos, including genes that are related to sebaceous glands, hair follicles, and epidermal differentiation. However, none of these genes exhibit inactivating mutations that are shared by cetaceans and hippos. Mean dates for the inactivation of skin genes in these two clades serve as proxies for phenotypic changes and suggest that hair reduction/loss, the loss of sebaceous glands, and changes to the keratinization program occurred ~16 million years earlier in cetaceans (~46.5 Ma) than in hippos (~30.5 Ma). These results, together with histological differences in the integument and prior analyses of oxygen isotopes from stem hippopotamids (“anthracotheres”), support the hypothesis that aquatic adaptations evolved independently in hippos and cetaceans.

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“…It depends on the type of movement the bones are subjected to and the intensity of physical exercise [ 28 , 35 , 36 , 41 , 42 , 78 , 79 , 80 , 81 ]. The Atlantic spotted dolphins have a high-energy swimming behaviour [ 53 , 55 ], with fast changes in directional swimming where the pectoral flippers play a steering role [ 61 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ] in contraposition to the pigmy sperm whale, which has a low-energy swimming behaviour [ 53 , 54 , 55 ] with less abrupt directionality changes in their swimming behaviour [ 61 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ]. As a result of this difference in swimming behaviour, the cortical radiodensity of the lateral humeral head was increased (as compared to the humeral medial aspect) in the Atlantic spotted dolphin but not in the pygmy sperm whale.…”

Section: Discussionmentioning

confidence: 99%

Cetaceans Humerus Radiodensity by CT: A Useful Technique Differentiating between Species, Ecophysiology, and Age

Consoli

Quirós

Hernández

et al. 2022

Animals

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Cetaceans are mammals that underwent a series of evolutionary adaptations to live in the aquatic environment, including morphological modifications of various anatomical structures of the skeleton and their bone mineral density (BMD); there are few studies on the latter. BMD is related to the radiodensity measured through computed tomography (CT) in Hounsfield units (HU). This work aimed to test and validate the usefulness of studying humeral bone radiodensity by CT of two cetacean species (the Atlantic spotted dolphin and the pygmy sperm whale) with different swimming and diving habits. The radiodensity was analysed at certain levels following a new protocol based on a review of previous studies. Humeral radiodensity values were related to four aspects: species, diving behaviour, swimming activity level, and age. We observed that the consistent differences in the radiodensity of the cortical bone of the distal epiphysis between animals of different life-history categories suggest that this bone portion could be particularly useful for future ontogenetic studies. Hence, this technique may be helpful in studying and comparing species with different ecophysiologies, particularly distinguishing between swimming and diving habits.

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Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by a Large Macrophagous Dolphin from the Oligocene of South Carolina

Cited by 25 publications

References 33 publications

Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans

Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans

Genomic and anatomical comparisons of skin support independent adaptation to life in water by cetaceans and hippos

Cetaceans Humerus Radiodensity by CT: A Useful Technique Differentiating between Species, Ecophysiology, and Age

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