heterocercal

This so called heterocercal tail is only known to exist, as a permanent adult feature, in the sturgeons of to-day.

Louis Agassiz His Life and Correspondence Agassiz, Louis 1885

This so called heterocercal tail is only known to exist, as a permanent adult feature, in the sturgeons of to-day.

Louis Agassiz: His Life and Correspondence Louis Agassiz 1840

Paddlefish are not closely related to sharks, but they do share some common characteristics including a skeleton primarily composed of cartilage, and a deeply forked, abbreviate heterocercal tail fin (the top fin lobe is slightly larger than the lower fin lobe).

Archive 2007-01-01 2007

These are the even-lobed, or homocercal (Fig. 68), and the uneven-lobed, or heterocercal (Fig. 69).

Darwin, and After Darwin (Vol. 1 and 3, of 3) An Exposition of the Darwinian Theory and a Discussion of Post-Darwinian Questions George John Romanes 1871

Now, in the development of a teleost fish (Fig. 68), as has been shown by Alexander Agassiz, the tail-fin is first like Fig. 70; then becomes heterocercal, like Fig. 69; and, finally, becomes homocercal like Fig. 68.

Darwin, and After Darwin (Vol. 1 and 3, of 3) An Exposition of the Darwinian Theory and a Discussion of Post-Darwinian Questions George John Romanes 1871

The lecturer dwelt chiefly on the argument of Agassiz, which he summarises as follows: "Homocercal fishes have in their embryonic state heterocercal tails; therefore heterocercality is, so far, a mark of an embryonic state as compared with homocercality, and the earlier heterocercal fish are embryonic as compared with the later homocercal."

More Letters of Charles Darwin — Volume 1 Charles Darwin 1845

Their tails, too, though both heterocercal, were diverse in their type.

The Cruise of the Betsey or, A Summer Ramble Among the Fossiliferous Deposits of the Hebrides. With Rambles of a Geologist or, Ten Thousand Miles Over the Fossiliferous Deposits of Scotland Hugh Miller 1829

Then with all his force the captain drove the pole down; the aim was good, for the next instant there was a tremendous swirl in the water, the long, heterocercal tail, through which the creature's spine was continued to the end of the upper lobe, rose above the surface, and was brought down with a tremendous blow which raised a shower, and at the same time Captain Bradleigh's arms were dragged lower and lower, till he loosened his hold, and the pole of the boat-hook disappeared.

Jack at Sea All Work and no Play made him a Dull Boy George Manville Fenn 1870