(of a fish's tail) approximately symmetrical and with the vertebral column continuing to the tip, as in lampreys.
- ‘The symmetrical, diphycercal tail, not perfected by gnathostomes until the Cretaceous, was standard equipment on heterostracans in the Silurian.’
- ‘In Strepsodus the tail was diamond shaped and diphycercal; in Gooloogongia loomesi it was nearly so.’
- ‘The Heterostracan head is covered with several armoured plates, the body with large scales and the tail is most often diphycercal.’
- ‘Bodies are long and slender, somewhat like salamanders, with a diphycercal tail.’
- ‘Sharks, and similar chondrichthyes, have heterocercal tails; the diphycercal tails are found in lungfish and their relatives; and the homocercal tail is characteristic of bony fish.’
Mid 19th century: from Greek diphu- of double form + kerkos tail + -al.