develops_from somite (...) cephalocordates and craniates belong to a group known as Somitichordata. Somitichordate synapomorphies include (1) somites (...) (reference 1); The idea that the last common ancestor of bilaterian animals (Urbilateria) was segmented has been raised recently on evidence coming from comparative molecular embryology (reference 2).[well established][VHOG] AAO:0010569 AEO:0001015 BTO:0001558 EHDAA2:0003436 EHDAA:366 EHDAA:699 EMAPA:31169 FMA:85522 GAID:1306 MAT:0000068 MESH:A16.254.425.660.750 MIAA:0000068 Post-cranial axial segments which form sclerotome and dermomyotome.[AAO] Somites are spheres of epithelial cells that form sequentially along the anterior-posterior axis of the embryo through mesenchymal to epithelial transition of the presomitic mesoderm. TAO:0000155 UBERON:0002329 UMLS:C0376449 Undifferentiated mesodermal components of early trunk or tail segments or metameres, derived from paraxial mesoderm; forms myotomes, sclerotomes and perhaps dermatomes. Kimmel et al, 1995.[TAO] VHOG:0000191 When the somite becomes segmented from the segmental plate, it is composed of an epithelial sac enclosing mesenchymal somitocoel cells. Thereafter the somite differentiates into two parts, the ventro-medial mesenchymal sclerotome and the dorso-lateral epithelial dermomyotome. This change in the epithelial somite depends on surrounding tissue [PMID:15906248] XAO:0000058 ZFA:0000155 currently classified as an epithelial vesicle, consistent with EHDAA2 and https://github.com/obophenotype/uberon/wiki/The-neural-crest. Consider making 'somitic mesoderm' a separate term and correlate with regionalization processes. Consider moving ZFA term to 'trunk somite' as it is part of the trunk epimere epimere mesoderm epithelial somite mesodermal cluster relationship loss: develops_from paraxial mesenchyme (TAO:0000942)[TAO] relationship type change: OBO_REL:part_of trunk (TAO:0001115) CHANGED TO: develops_from trunk (UBERON:0002100)[TAO] relationship type change: part_of paraxial mesoderm (AAO:0010568) CHANGED TO: develops_from paraxial mesoderm (UBERON:0003077)[AAO] somites somitic somitic mesoderm somitus uberon presomitic mesoderm developing anatomical structure epithelial vesicle meso-epithelium