| 单词 |
prechordate |
| 释义 |
prechordate, n. and a. Zool.
Brit. |priːˈkɔːdeɪt|, U.S. |priˈkɔrˌdeɪt|, |priˈkɔrdət|
[‹ pre- prefix + chordate adj.]
A. n. An animal considered to represent an evolutionary stage ancestral to the chordates. Cf. protochordate n.
1929W. K. Gregory Our Face from Fish to Man 186 Studnicka..holds that originally there were two pairs of paired eyes in the pre-chordates, one pair dorsal,..the second pair low down on the sides of the head, the eyes of later vertebrates. 1953Q. Rev. Biol. 28 74/2 Two lines of ascent, the one comprising the echinoderms, prechordates, and chordates, and the other embracing all the remaining invertebrate phyla. 2006Clin. Anat. 19 71/1 The turbinates..are derived from the prechordal plate, which is part of the sensory capsules that protected the sense organs..of the ancestral prechordates.
B. adj. That is an evolutionary ancestor of the chordates; occurring or originating prior to the evolution of the chordates.
1933Trans. Amer. Philos. Soc. 23 85 Undiscovered and hypothetical prechordate stage, possibly resembling in fundamental characters the ‘Tornaria’ larva of Balanoglossus. 1993Proc. National Acad. Sci. U.S.A. 90 6304/1 Gans and Northcutt have argued that the vertebrate head is a recent innovation, since elements relevant to its formation are absent from prechordate and primitive chordate forms. 2006Molec. Biol. & Evol. 23 20/1 The growing notion that vertebrate genomes are the product of genome duplications of an ancestral prechordate genome. |
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