IMAGES: How the Dolphin Got His Flippers

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Science  20 Aug 2004:
Vol. 305, Issue 5687, pp. 1085
DOI: 10.1126/science.305.5687.1085b

Embryonic development in dolphins retrofits a land-adapted body for life in the sea. But the rarity of preserved specimens stymies students and researchers who want to study, say, how the forelimbs morph into flippers. Aimed at filling this gap is the newborn site Digital Library of Dolphin Development, created by anatomist Hans Thewissen of the Northeastern Ohio Universities College of Medicine in Rootstown and colleagues.

The atlas's images of whole and sectioned spotted dolphins (Stenella attenuata) span the formative period from about 3 weeks to 4 months after conception. (Total gestation time is 11 months.) Photo sequences show, for example, how tiny rear limbs sprout but then regress and how the long, tapered tail widens and flattens at the tip to form a fluke. You can also probe the gory details of internal anatomy with sectioned embryos representing three developmental stages.

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