part of part of has potential to develop into immediate transformation of somite presomitic mesoderm AAO:0011086 EFO:0001982 EMAPA:16189 EMAPA:16752 It is reasonable to assume that the proximate invertebrate ancestor of the vertebrates had an amphioxus-like tail bud in its larval stage. This archetypal tail bud would have (...) (3) lacked any component of mesenchyme cells, (4) budded off new mesodermal segments directly, without any intervening zone of presomitic mesoderm (...). Then, early in vertebrate evolution, epithelium-to-mesenchyme interconversions (and the gene networks for effecting them) became prominent features of development. (...) In any case, conspicuous mesenchymal components tended to be added to the vertebrate tail bud itself. In addition, a mesenchymatous presomitic mesoderm (not a part of the tail bud proper) came to intervene between the tail bud and the forming somites.[well established][VHOG] PSM TAO:0000279 UBERON:0003059 Unsegmented field of paraxial mesoderm present posterior to the most recently formed somite pair, from which somites will form. Unsegmented field of paraxial mesoderm present posterior to the most recently formed somite pair, from which somites will form. Kimmel et al, 1995.[TAO] VHOG:0000559 XAO:0000057 ZFA:0000279 presumptive somite mesoderm segmental plate somitogenic mesoderm somitomeric mesoderm uberon unsegmented mesenchyme unsegmented paraxial mesoderm paraxial mesoderm developing anatomical structure presumptive structure presumptive segmental plate