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pre·so·mite .prē-'sō-.mīt adj occurring in, being in, or being the period of embryonic development prior to the formation of somites <a \presomite human embryo>
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pre·so·mite (pre-soґmīt) [pre- + somite] referring to embryos before the appearance of somites; in the human, before 19 days postfertilization.Medical dictionary. 2011.