acrania defined in 1951 year

acrania - acrania (cephaloghordata);
acrania - Sub-phylum of Ghordata containing only species of amphioxus, all marine. Unlike Vertebrata they have no brain, skull, or cartilaginous or bony skeleton; but they have typical chordate dorsal tubular nerve-cord with double nerve roots, notochord, gill-slits, muscle blocks (myotomes); and they have an unexpected feature, found in no other chordate though in many invertebrates - nephridia as excretory organs. They may be closely related to early ancestors of fish and other vertebrate groups. A very early fossil probably belonging to the group has been discovered (Jaymoytius from the Silurian).

near acrania in Knolik

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