Cartilaginous fishes

Devonian 400 Myr Continents collide at end of period. Asteroid probably collides with Earth. Diversification of bony and cartilaginous fishes trilobites diversify origin of ammonoids, amphibians, insects first forests. Mass extinction at end of period (ca. 75% of species disappear)... 

In the OE of jawed fish only cellular, and little if any, tissue specialisation is achieved. During metamorphosis from tadpole to adult in amphibia, a developmental parallel of water-to-land transition includes the timing of maturation of the AOS. The system as it appears in living amphibians, is already a more or less discrete entity (Fig. 4.3) with its own sub-set of receptors. A process of regionalisation within the bulb, already underway even at the level of organisation in cartilaginous fishes, shows parallel adjustments (Dryer and Graziadei, 1993). 

Luther et al. (1996) conducted a systematic study of the occurrence of the simple lattice and superlattice across the vertebrate kingdom. Superlattices are present in the muscles of all the higher vertebrates, namely, in mammals (including humans), in amphibians, in birds, in reptiles, and in some muscles of cartilaginous fish. Simple lattices occur in all the teleost (bony fish) muscles so far studied, in some muscles of cartilaginous fish, and also in some primitive fish such as sturgeons and bowfin. 

In bony and cartilaginous fish, there is compelling evidence for an AHR-CYP1A pathway that functions like that in mammals. In contrast, the situation in jawless... 

Gangliosides with short carbohydrate chains have been isolated from brain tissue of eight species of cartilaginous fish. Sequential enzymatic hydrolysis showed that the structure (16) was the major elasmobranch brain ganglioside. 

R. Acher, J. Chauvet, M.T. Chauvet, D. Crepy, Phylogeny of neurohypophyseal peptides isolation of a new hormone, glumitodn, (4-serine-8-glutamine oxytocin), present in cartilaginous fish, the ray (Raja clavata). Biochim. Biophys. Acta 107 393-396 (1965)... 

---