hypural
Laterally flattened haemal spine of an ural vertebra that lacks its arch and supports a few principal caudal lepidotrichia distally. A hypural may articulate or fuse with its ural centrum proximally or may lie ventral to the notochord. A hypural is an unpaired median bone that ossifies perichondrally. (Modified from Monod, 1968 and Arratia and Schultze, 1992).