Protocetid cetaceans (Mammalia) from the Eocene of India
Cetacea; India; hearing; Paleontology; morphology; origin; pakistan; Eocene; locomotor evolution; Mammalia; middle eocene; earliest cetaceans; ambulocetidae; early whales; kutch; New genus; New species
Protocetid cetaceans were first described from the Eocene of India in 1975, but many more specimens have been discovered since then and are described here. All specimens are from District Kutch in the State of Gujarat and were recovered in deposits approximately 42 million years old. Valid species described in the past include Indocetus ramani, Babiacetus indicus and B. mishrai. We here describe new material for Indocetus, including lower teeth and deciduous premolars. We also describe two new genera and species: Kharodacetus sahnii and Dhedacetus hyaeni. Kharodacetus is mostly based on a very well preserved rostrum and mandibles with teeth, and Dhedacetus is based on a partial skull with vertebral column. The Kutch protocetid fauna differs from the protocetid fauna of the Pakistani Sulaiman Range, possibly because the latter is partly older, and/or because it samples a different environment, being located on the trailing edge of the Indian Plate, directly exposed to the Indian Ocean.
Bajpai S; Thewissen J G M
Palaeontologia Electronica
2014
2014
Journal Article or Conference Abstract Publication
n/a
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
The early radiations of cetacea (Mammalia): Evolutionary pattern and developmental correlations
archaeocete; artiodactyls; development; Environmental Sciences & Ecology; evolution; Evolutionary Biology; feet; fossil record; India; locomotor evolution; marine mammal; middle eocene; origin; pakistan; Stenella attenuata; time; whales
The origin and early evolution of Cetacea (whales, dolphins, and porpoises) is one of the best examples of macroevolution as documented by fossils. Early whales are divided into six families that differ greatly in their habitats, which varied from land to freshwater, coastal waters, and fully marine. Early cetaceans lived in the Eocene (55-37 million years ago), and they show an enormous morphological diversity. Toward the end of the Eocene the modem cetacean body plan originated, and this body plan remained more or less the same in the subsequent evolution. It is possible that some aspects of this body plan are rooted in constraints that are dictated by cetacean embryologic development and controlled by genes that affect many organ systems at once. It may be possible to use a study of patterns of correlations among morphological traits to test hypotheses of developmental links among organ systems.
Thewissen J G M; Williams E M
Annual Review of Ecology and Systematics
2002
2002
Journal Article
<a href="http://doi.org/10.1146/annurev.ecolysis.33.020602.095426" target="_blank" rel="noreferrer noopener">10.1146/annurev.ecolysis.33.020602.095426</a>