title: Microlens arrays in the complex visual system of Cretaceous echinoderms.
abstract: It has long been assumed that photosensitivity in echinoderms is mainly related to diffuse photoreception mediated by photosensitive regions embedded within the dermis. Recent studies, however, have shown that some extant echinoderms may also display modified ossicles with microlenses acting as sophisticated photosensory organs. Thanks to their remarkable properties, these calcitic microlenses serve as an inspiration for scientists across various disciplines among which bio-inspired engineering. However, the evolutionary origins of these microlenses remain obscure. Here we provide microstructural evidence showing that analogous spherical calcitic lenses had been acquired in some brittle stars and starfish of Poland by the Late Cretaceous (Campanian, ~79 Ma). Specimens from Poland described here had a highly developed visual system similar to that of modern forms. We suggest that such an optimization of echinoderm skeletons for both mechanical and optical purposes reflects escalation-related adaptation to increased predation pressure during the so-called Mesozoic Marine Revolution.
authors.affiliation: Department of Biogeology, Institute of Paleobiology, Polish Academy of Sciences, Twarda Street 51/55, 00-818 Warsaw, Poland.
authors.forename: Przemysław
authors.initials: P
authors.lastname: Gorzelak
authors.affiliation: Department of Palaeontology and Biostratigraphy, Faculty of Earth Sciences, University of Silesia, Będzińska Street 60, 41-200 Sosnowiec, Poland.
authors.forename: Mariusz A
authors.initials: MA
authors.lastname: Salamon
authors.affiliation: Department of Palaeontology and Biostratigraphy, Faculty of Earth Sciences, University of Silesia, Będzińska Street 60, 41-200 Sosnowiec, Poland.
authors.forename: Rafał
authors.initials: R
authors.lastname: Lach
authors.affiliation: Faculty of Geology, University of Warsaw, Żwirki i Wigury 93, 02-089 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Loba
authors.affiliation: Dame du Lac 213, 3 rue Henri Barbusse, F-76300 Sotteville-lès-Rouen, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Ferré
mesh_terms: D000818:Animals; D004447:Echinodermata / Q000033:anatomy & histology / Q000502:physiology* / Q000648:ultrastructure*; D005580:Fossils; D007908:Lens, Crystalline / Q000033:anatomy & histology / Q000502:physiology / Q000648:ultrastructure; D011044:Poland; D014785:Vision, Ocular