in taxon develops from develops from immediate transformation of Chordata tissue embryo hypochord UBERON:0003058 XAO:0000056 In other words, we identified variations in gene expression patterns that may contribute to a molecular basis of evolutionary variation of axial structures between Teleostei and Mammalia in the determination of body axis. As already mentioned, one such difference is illustrated by the hypochord present in lower vertebrates but absent in higher animals. Perhaps, Tbx-b and Tbx-c are involved in the mechanisms underlying the formation of this organ that were lost during later evolution leading to the disappearance of the hypochord itself, similarly to other organs, such as the lateral line.[uncertain][VHOG] The hypochord is a transient rod-like structure in the embryos of fish, lampreys and amphibians that is located immediately ventral to the notochord. The hypochord may play a role in positioning the dorsal aorta[GO]. A transient rod-like structure which is endodermally derived and located immediately ventral to the notochord. The hypochord is thought to play a role in positioning the dorsal aorta. Eriksson and Lofberg, 2000.[TAO] TAO:0000031 ZFA:0000031 ipochord EFO:0003475 subnotochordal rod VHOG:0000081 AAO:0000733 Unsegmented ventral structure in the caudal region of anuran larvae; near metamorphosis the hypochord fuses to the coccyx, thereby forming the urostyle.[AAO] Unlike in frogs and axolotl, the hypochord does not appear to be endodermally derived[ZFA]. near metamorphosis the hypochord fuses to the coccyx, thereby forming the urostyle[AAO] presumptive hypochord