Moreover, the
cartilaginous fish have five to seven pairs of gills, and primitive jawless fish have seven pairs of gills (Romer, 1949).
This study concluded that the lipid levels and the amount of EPA and DHA in the liver oil of all the
cartilaginous fish are sufficient to be used as commercial raw materials for the manufacturing of pharmaceutical and cosmetic products.
Roberts, The Central Nervous System of
Cartilaginous Fishes: Structure and Functional Correlations, Springer, 1983.
Thus, this would put the explanation of the
cartilaginous fish before both the birds and the four-footed egg-laying animals in so far as the
cartilaginous fish bear live young and are more perfect than the others which generate perfect eggs.
For most salmonids,
cartilaginous fishes, three-spine stickleback, Irish lords (Hemilepidotus spp.), and Pacific mackerel (Scomber japonicus), no otoliths were recovered; therefore other skeletal elements had to be used for identification (Table 2).
It has been suggested that few managers worldwide are willing to constrain economically or socially important fisheries for the benefit of
cartilaginous fish like sharks and rays.
First, Kirsten explains that fish fall into three categories: primitive fish such as lampreys and hagfish,
cartilaginous fish such as sharks and rays, and bony fish which are all of those with bony skeletons.
This is an important topic, if we take into account that skates and rays are the most vulnerable group among
cartilaginous fish, to overexploitation (Duvly & Reynolds, 2002).
Researchers have also debated whether Helicoprion was more like a modern shark or another ancient group of
cartilaginous fish, the chimaera.
Skate fall into the class known as
cartilaginous fish which also include sharks and rays.