The middle germ layer of the embryo, between the endoderm and ectoderm.
Comment:
[homology-note] "The Bilateria are triploblastic (with true endoderm, mesoderm, and ectoderm) (...).[well established][VHOG]" xsd:string {date_retrieved="2012-09-17", external_class="VHOG:0000152", ontology="VHOG", source="ISBN:978-0878932504 Gilbert SF, Developmental Biology (2006) Limb development and evolution, p.722", source="http://bgee.unil.ch/"}; [taxon-note] "sponges do not seem to have a mesoderm and accordingly Amphimedon lacks transcription factors involved in mesoderm development (Fkh, Gsc, Twist, Snail)[http://www.nature.com/nature/journal/v466/n7307/full/nature09201.html]. Mesoderm may not be homologous across verteberates" xsd:string {source="https://github.com/obophenotype/uberon/wiki/The-neural-crest"}