Titlebook: Biology of the Cyclostomes; M. W. Hardisty Book 1979 M. W. Hardisty 1979 Agnatha.biology.development.ecology.evolution.genetics.morphology

做事過(guò)頭

Reproduction and development,of their unpaired gonad indicates that the sexual differentiation of these animals is in a curious transitional state between gonochorism and hermaphroditism. Whether the myxinoids have a determinate life span is unknown, but they certainly produce a succession of eggs; each ovulation being followed

CESS

鍍金

Conclusions and evolutionary perspectives,tic system has a corresponding twin or sister group and that both are derived from a common ancestor (Fig. 14.la). In this dichotomy, one of the sister groups retains to a greater extent the characters of the ancestral group (m.) and is referred to as plesiomorphic (or in L?vtrup’s terminology, ples

Reverie

CRUMB

Zielspezifizierung: LehrzielbestimmungThe Cyclostomes, comprising the lampreys and the hagfishes or myxinoids, are a group of eel-like aquatic vertebrates, not widely known outside zoological circles, for whom they have a special interest as the sole survivors of an extinct, but once flourishing, group of jawless or agnathan Palaeozoic ‘fishes’ known as the Ostracoderms.

不來(lái)

斜

漂泊

鐵砧

Kompendium multimediales Lernen in the Silurian then decreasing in numbers, finally to disappear from the fossil record at the close of the Devonian. Since the first jawed vertebrates, the acanthodians were not to be found earlier than the upper Silurian, it is hardly surprising that the agnathans and gnathostomes should have bee

喚起

Kompendium multimediales Lernen distinct species differences, particularly in the depths to which they penetrate. . normally occurs between 50–100 m, but has been recorded down to 1100 m off the Norwegian coast and in Japanese waters . is found between 400–800 m. In some inner fiords, . may occur in much shallower water at about