| 释义 |
agnathan, n. and a. Ichthyol.|ægˈneɪθən|
Also Agnathan.
[f. mod.L. Agnatha (E. D. Cope 1889, in Amer. Naturalist XXIII. 852), f. Gr. ἀ- a- 14 + γνάθ-ος jaw + -a 2: see -an.]
A. n. A member of the class or superclass Agnatha of jawless fishes, which comprises hagfish, lampreys, and many extinct forms, including the earliest vertebrates.
1939J. A. Moy-Thomas Palaeozoic Fishes i. 2 The head of a hypothetical primitive Agnathan must have had a terminal mouth and been segmented in a manner similar to the rest of the body. 1978Sci. Amer. Sept. 111/1 The early jawless fishes, the agnathans, are first known from late Cambrian fossils. 1984J. S. Nelson Fishes of World (ed. 2) 29 The interrelationships of the agnathans have been subject to many differences of opinion.
B. adj. Of, pertaining to, or being an agnathan.
1974D. & M. Webster Compar. Vertebr. Morphol. iv. 64 Since the agnathan head skeleton lacks jaws, only the cartilages of the tongue and the lamprey's annular cartilage are involved in food gathering. 1979Nature 20 Dec. 831/2 We have united the galeaspids and polybranchiaspids..and grouped them within the same major agnathan division as the anaspids and lampreys—the Cephalaspidomorphi. 1985A. Wheeler World Encycl. Fishes (ed. 2) p. vii/2 The 32 known species of lamprey and the related hagfishes are the sole survivors of the agnathan fishes, a group of great diversity in the fossil record. |