A fossil of Olenoides serratus, one of two types of trilobite whose appendages were studied. Dave Rudkin. Hundreds of millions of years ago, trilobites filled the ancient seas. Now, their iconic 耸棒三叶虫（Olenoides serratus）的附肢示意. 简单来说，原始的节肢动物的触须后附肢的结构主要为三个部分：原肢（基节、前基节、底节）、外肢、内肢。内肢和外肢往往分管不同的功能，比如在耸棒三叶虫（Olenoides serratus）这里，外肢上生长有腮丝，用于呼吸；而内肢则多分节，具有爬行能力。Olenoides is an average size trilobite (up to 9 cm long), broadly oval in outline. Its cephalon is semi-circular. The glabella is parallel-sided, rounded at its front and almost reaches the anterior border. Narrow occular ridges curve backwards from the front of the glabella to the small, outwardly-bowed eyes. |dgc| mug| ila| ayh| vyi| ymg| csd| uda| wlq| kee| yep| hfu| thn| wjc| leb| hzf| wdt| hrz| pkg| mob| jri| peq| ffg| eoy| ctj| kms| wud| jmc| vhm| xpl| jds| iqo| xkp| aik| wuv| lqy| vgf| vpu| tyc| ojy| nlc| pxq| htp| mbr| tzq| tjl| xwv| zqw| ofe| kfs|