Evolution of dental wear and diet during the origin of whales
artiodactyls; Biodiversity & Conservation; carbon-isotope discrimination; cetaceans; Environmental Sciences & Ecology; Evolutionary Biology; mammalia; middle eocene; pakistan; Paleontology; photosynthesis; seagrasses; tooth enamel; transitions
Dental morphology changes dramatically across the artiodactyl-cetacean transition, and it is generally assumed that this reflects the evolutionary change from herbivory and omnivory to carnivory. To test hypotheses regarding tooth function and diet, we studied size and position of wear facets on the lower molars and the stable isotopes of enamel samples. We found that nearly all investigated Eocene cetaceans had dental wear different from typical wear in ungulates and isotope values indicating that they hunted similar prey and processed it similarly. The only exception is the protocetid Babiacetus, which probably ate larger prey with harder skeletons. The closest relative of cetaceans, the raoellid artiodactyl Indohyus, had wear facets that resemble those of Eocene cetaceans more than they do facets of basal artiodactyls. This is in spite of Indohyus's tooth crown morphology, which is unlike that of cetaceans, and its herbivorous diet, as indicated by stable isotopes. This implies that the evolution of masticatory function preceded that of crown morphology and diet at the origin of cetaceans.
Thewissen J G M; Sensor J D; Clementz M T; Bajpai S
Paleobiology
2011
2011
Journal Article
n/a
Locomotor evolution in the earliest cetaceans: functional model, modern analogues, and paleontological evidence
aquatic locomotion; Biodiversity & Conservation; efficiency; Environmental Sciences & Ecology; eocene; Evolutionary Biology; origin; otters; Paleontology; power output
We discuss a model for the origin of cetacean swimming that is based on hydrodynamic and kinematic data of modern mammalian swimmers. The model suggests that modern otters (Mustelidae: Lutrinae) display several of the locomotor modes that early cetaceans used at different stages in the transition from land to water. We use mustelids and other amphibious mammals to analyze the morphology of the Eocene cetacean Ambulocetus natans, and we conclude that Ambulocetus may have locomoted by a combination of pelvic paddling and dorsoventral undulations of the tail, and that its locomotor mode in water resembled that of the modern otter Lutra most closely. We also suggest that cetacean locomotion may have resembled that of the freshwater otter Pteronura at a stage beyond Ambulocetus.
Thewissen J G M; Fish F E
Paleobiology
1997
1997
Journal Article
<a href="http://doi.org/10.1017/s0094837300019850" target="_blank" rel="noreferrer noopener">10.1017/s0094837300019850</a>