Abstract
Trilobites, extinct arthropods that dominated the faunas of the Palaeozoic, since their appearance c 523 million years ago, were equipped with elaborate compound eyes. While most of them possessed apposition compound eyes (in trilobites called holochroal eyes), comparable to the compound eyes of many diurnal crustaceans and insects living today, trilobites of the suborder Phacopina developed atypical large eyes with wide lenses and wide interspaces in between (schizochroal eyes). Here, we show that these compound eyes are highly sophisticated systems—hyper-compound eyes hiding an individual compound eye below each of the big lenses. Thus, each of the phacopid compound eyes comprises several tens, in cases even hundreds of small compound eye systems composing a single visual surface. We discuss their development, phylogenetic position of this hyper-compound eye, and its neuronal infrastructure. A hyper-compound eye in this form is unique in the animal realm.
Highlights
Trilobites, extinct arthropods that dominated the faunas of the Palaeozoic, since their appearance c 523 million years ago, were equipped with elaborate compound eyes
Trilobites are extinct arthropods that dominated the faunas of the Palaeozoic
Proper apposition compound eyes were confirmed in the Silurian trilobite Aulacopleura koninckii (Barrande, 1846)[25]
Summary
Trilobites, extinct arthropods that dominated the faunas of the Palaeozoic, since their appearance c 523 million years ago, were equipped with elaborate compound eyes. He found the relevant evidence, hitherto open-ended, and resolved in this study In this form the hyper-compound eye of phacopid trilobites is probably unique in the animal realm, though similar if more complex, to the system of certain amphipod crustaceans. This ~ 400 million-year-old system suggests capacities of complex neuronal interconnections and processing, such as sharing of functions, perhaps colour perception, or neuronal superposition. Produced magnificent radiographs, not just of shells, and of soft tissues, which in those times was a new dimension in p alaeontology[2,3]
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