Boulenger draws a distinction between the protocercal tail, the one primitively straight, and the diphycercal tail modified, like the homocercal tail, from an heterocercal ancestry.
It is known as heterocercal, and finally in ordinary fishes the tail becomes homocercal or fan-shaped, although usually some trace of the heterocercal condition is traceable, gradually growing less with the process of development.
The homocercal tail is the fan-shaped or symmetrical tail common among the Teleosts, or bony fishes.
This form differs little from diphycercal, except in its supposed derivation from the homocercal type.
It characterises the earlier periods of the earth's history, whereas in the secondary strata, or those newer than the Permian, the homocercal tail predominates.
Thus fin spines, ctenoid scales, and the homocercal tail are lost in the codfishes, the connection of ventrals with shoulder-girdle fails in the Percesoces, etc.
Thus as time advanced the heterocercal tail was gradually evolved from the diphycercal, and the homocercal from the heterocercal.
In the Triassic and Jurassic its lobes in many cases became nearly equal, approaching the homocercal tail.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "homocercal" in a variety of sentences. We hope that you will now be able to make sentences using this word.
