VIII.—On the Schizochroal Eyes of Three Species of Reedops (Trilobita: Phacopidae) from the Lower Devonian of Bohemia

E. Clarkson
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引用次数: 28

Abstract

Synopsis Bohemian specimens of the phacopacean trilobites Reedops cephalotes (Hawle and Corda,) R. sternbergi (Hawle and Corda) and R. bronni (Barrande) have very well preserved schizochroal eyes. The sizes and distribution patterns of the eye lenses were studied and in R. sternbergi and R. bronni the angular bearings of all the lenses were measured, giving the visual range of the whole eye. The internal anatomy of the eyes was also investigated, mainly from cut and polished sections. In many respects their morphology was comparable with that described previously in the Silurian and Devonian phacopaceans Phacops latifrons (Bronn) and Ananaspis communis (Barrande). The intralensar structures, however, are unlike those of P. latifrons and A. communis but bear a strong resemblance to the intralensar bowls of the Ordovician Zeliszkellinae, an early group believed to have been ancestral both to dalmanitaccan and post-Ordovician phacopacean stocks. A brief history of the evolution of schizochroal eyes is given, some distinctive evolutionary trends are noted and the relationship of the structural pattern in Reedops is discussed with reference to that in other Phacopina.
8波希米亚下泥盆世三种芦苇(三叶虫:芦苇科)的裂眼研究
波西米亚的棘足纲三叶虫Reedops cephalotes (Hawle和Corda), R. sternbergi (Hawle和Corda)和R. bronni (Barrande)的标本保存完好。研究了眼晶状体的大小和分布模式,并测量了sternbergi和R. bronni的所有晶状体的角方位,给出了整个眼睛的视觉范围。眼睛的内部解剖结构也进行了研究,主要是通过切割和抛光的部分。在许多方面,它们的形态与先前在志留纪和泥盆纪phacopacean (Bronn)和Ananaspis communis (Barrande)中描述的Phacops latifrons和Ananaspis communis相似。然而,囊内结构与P. latifrons和a . communis不同,但与奥陶系Zeliszkellinae的囊内碗非常相似,后者是一个早期群体,被认为是dalmanitaccan和后奥陶系phacopacean种群的祖先。本文简要介绍了分裂眼的进化历史,指出了一些独特的进化趋势,并讨论了芦苇的结构模式与其他植物的结构模式的关系。
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