Insights to eyes of Phacopid trilobites
2012
Schoenemann, B., Universität Bonn (Germany). Steinmann-Inst. für Geologie, Mineralogie und Paläontologie | Clarkson, E.N.K., University of Edinburgh (United Kingdom). Grant Inst. School of Geosciences
Trilobites are the dominating form of arthropods during the Palaeozoic. They appear in the Cambrian with well developed compound eyes in many different well adapted forms. By the fossil record three main types were evolved: the holochroal, the schizochroal and the abathochroal type. The latter derived from the basal holochroal eyes by paedomorphosis. While as normal in fossils, just the outer structure is preserved in these compound eyes, nothing is known about the internal sensory systems so far. However, by computer tomography it was possible to show, that these sensory structures left traces during the fossilisation process in certain schizochroal eyes of phacopid trilobites. The analysis reveals that these eye systems worked as apposition eyes, a common system in recent diurnal arthropods. This implicates that the trilobites had a mosaic-like vision, as today living organisms, which still possess such compound eyes.
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