Holochroal eye

Holochroal eye

Holochroal eyes are compound eyes with a many (sometimes over 15,000) tiny lenses (30-100μm, rarely larger).Citation | last1 = Clarkson | first1 = E. N. K. | year=1979 | title =The Visual System of Trilobites.| journal =Palaeontology |volume= 22 |pages=1-22 ] They are the oldest and most widespread type of trilobite eye,citation
author = Schoenemann, B.
title = Trilobite Eyes and a New Type of Neural Superposition Eye in an Ancient System
year = 2007
month=October
journal = Palaeontographica Abt. A
volume = 281
issue = 1-3
pages = 63-91
publisher = Verlag] and found in all orders of trilobite from the Cambrian to the Permian periods. Lenses show hexagonal close packing, and a single corneal membrane covered all lenses.Citation | last = Clarkson | first = E.N. | contribution = The Eye, Morphology, Function and Evolution | editor-last = Kaesler | editor-first = R.L. (ed) | title = Treatise on Invertebrate Paleontology, Part O, Arthropoda 1, Trilobita, revised. Volume 1: Introduction, Order Agnostida, Order Redlichiida. | pages = 114-132 | publisher = The Geological Society of America, Inc. & The University of Kansas | place = Boulder, CO & Lawrence, KA | year = 1997 | isbn = 0-8137-3115-1 ] Unlike most modern arthropods, these eyes were not covered by the white layer known as the sclera.

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  • holochroal — adj. [Gr. holos, whole; chroa, body surface] (ARTHROPODA) Refers to a compound eye with narrow facets and polygonal lenses, as in most crustacean and insect eyes; see schizochroal …   Dictionary of invertebrate zoology

  • Arthropod eye — Anatomy of the compound eye of an insect The arthropods ancestrally possessed compound eyes, but the type and origin of this eye varies between groups, and some taxa have secondarily developed simple eyes. The organ s development through the… …   Wikipedia

  • Trilobite — ] Highly complex compound eyes are another obvious feature of the cephalon (see below). Figure 3 shows gross morphology of the cephalon. The cheeks (genae) are the pleural lobes on each side of the axial feature, the glabella. When trilobites… …   Wikipedia

  • Proetida — Taxobox name = Proetida fossil range = Ordovician Permian image width = 240px image caption = Devonian Cyphaspis tafilalet trilobites of the superfamily Aulacopleuroidea regnum = Animalia phylum = Arthropoda classis = Trilobita subclassis =… …   Wikipedia

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