Evolution and development of cetacean appendages

[sarlo518]

EVOLUTION AND DEVELOPMENT OF CETACEAN APPENDAGES

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INTRODUCTION Over the past decade, the origin of cetaceans (whales, dolphins, and porpoises) has become an excellent case study in mammalian evolution (Thewissen and Bajpai, 2001, Uhen 2007, Thewissen et al., 2009). A rich collection of fossil cetaceans, mostly from Asia, Africa and North America, provides an ancient record of the cetacean transition from a terrestrial to a completely aquatic environment (e.g., Gingerich et al., 1994, 2001; Thewissen et al., 1994, 2001a,b; Hulbert, 1998; Hulbert et al., 1998; Bajpai and Thewissen 2000; Geisler, 2001; Uhen, 2004, 2007; Thewissen et al., 2009). Cetaceans initially took to the seas about 50 million years ago in an ancient shallow seaway, the Tethys Sea, that laid between the Indian subcontinent and Asia (e.g. Thewissen and Bajpai, 2001). Within about 10 million years in the aquatic environment, cetaceans evolved specialized ears for hearing underwater, reduced the size of the hindlimbs, and developed tail flukes for propulsion. The cetacean body plan had so radically evolved from terrestrial artiodactyls (even-toed hoofed mammals) that modern cetaceans are no longer able to bear their weight on land and are obligatorily aquatic (Thewissen and Fish, 1997; Buccholtz, 1998; Bajpai and Thewissen, 2000; Madar et al., 2002; Gingerich et al., 2001; Gingerich, 2003).

 

[dolfy31]

Dead link lease:
Could u reupload please ?
Many thanks