sdsnl Posted October 15, 2015 Share Posted October 15, 2015 I am reading about trilobite eyes and am curious about the following: Are stalk eyes simple or compound eyes? If compound, are they holochroal or schizochroal? Where on the stalk are the eyes located? On the front, on the sides, or 360° view? There doesn't seem to be any closeup photos of stalk eyes around? What are primary & secondary blindness? I see websites listing which trilobites are primarily blind and which are secondarily blind, but there doesn't seem to be explanation about what they mean? Is it different degrees of blindness like being able to sense light and no sight at all? Link to comment Share on other sites More sharing options...
piranha Posted October 15, 2015 Share Posted October 15, 2015 Trilobite eyes are not referred to as simple, all trilobite eyes are compound. The stalked eyes of Asaphus kowalewskii are holochroal, the Phacopidae are the only trilobites with schizochroal eyes. Attached are some figures with the shaded areas showing the range of the visual surface of A. kowalewskii. Trilobites that are secondarily blind possessed eyes earlier in a lineage but evolved to lose vision as unnecessary to the changing environment. Proof of this is vestigial eye ridges in certain genera without eyes. Ivantsov, A.Y. (2004) Determining Ordovician Asaphid trilobite species by shape in the vicinity of Saint Petersburg. Paleontological Institute of the Russian Academy of Sciences, 60 pp. 4 Link to comment Share on other sites More sharing options...
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