My Oldest Sister Is a Sea Walnut?

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Science  13 Dec 2013:
Vol. 342, Issue 6164, pp. 1327-1329
DOI: 10.1126/science.1248424

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With common names such as “sea walnut,” “sea gooseberry,” and “Venus' girdle” that reflect their morphological diversity, the jelly-like creatures belonging to the phylum Ctenophora that bear distinctive “combs” of cilia are not only breathtakingly beautiful (1) but are also key to understanding early animal evolution. On page 1336 of this issue, Ryan et al. (2) decode the genome of the sea walnut Mnemiopsis leidyi, the first member of this phylum to be sequenced, and propose that ctenophores might be the earliest branch of the animal tree and the sister lineage to that of all other animals. This paints a picture of early animal evolution full of cell type complexity, as well as its loss.