Vision in fossilised eyes

Abstract

This paper presents a review of recent developments in the study of vision in fossil arthropods, beginning with a discussion of the origin of visual systems. A report of the eyes of Cambrian arthropods from different Lagerstätten, especially the compound and median arthropod eyes from the Chengjiang fauna of China, is given. Reference is made also to compound eyes from the lower Cambrian Emu Bay Shale fauna of Australia and the Sirius Passet fauna of Greenland; also to the three-dimensionally preserved 'Orsten' fauna of Sweden. An understanding of how these eyes functioned is possible by reference to living arthropods and by using physical tools developed by physiologists. The eyes of trilobites (lower Cambrian to Upper Permian) are often very well preserved, and the structure and physiology of their calcite lenses, and the eye as a whole, are summarised here, based upon recent literature. Two main kinds of trilobite eyes have been long known. Firstly, there is the holochroal type, in which the lenses are usually numerous, small and closely packed together; this represents the ancestral kind, first found in lowermost Cambrian trilobites. The second type is the schizochroal eye, in which the lenses are relatively much larger and each is separated from its neighbours. Such eyes are confined to the single suborder Phacopina (Lower Ordovician to Upper Devonian). This visual system has no real equivalents in the animal kingdom. In this present paper, the origin of schizochroal eyes, by paedomorphosis from holochroal precursors, is reviewed, together with subsequent evolutionary transitions in the Early Ordovician. A summary of new work on the structure and mineralogy of phacopid lenses is presented, as is a discussion of the recent discovery of sublensar sensory structures in Devonian phacopids, which has opened up new dimensions in the study of trilobite vision.

Disparate compound eyes of Cambrian radiodonts reveal their developmental growth mode and diverse visual ecology

“…canadensis with more than 24,000 lenses is rivaled only by certain predatory insects such as dragonflies ( Fig. 3A ) ( 39 , 40 ), and the enormous lens diameters of ‘ A.’ briggsi (up to 335 μm) are matched only by select marine euarthropods, such as some phacopine trilobites ( 21 , 41 ), Siluro-Devonian pterygotid eurypterids ( 35 ), and some modern deep-sea amphipod crustaceans ( Fig. 3B ) ( 42 ).…”

“…3A) (39,40), and the enormous lens diameters of 'A.' briggsi (up to 335 m) are matched only by select marine euarthropods, such as some phacopine trilobites (21,41), Siluro-Devonian pterygotid eurypterids (35), and some modern deep-sea amphipod crustaceans (Fig. 3B) (42).…”

Comparative experimental taphonomy of eight marine arthropods indicates distinct differences in preservation potential

“…Ample research on the vision of other arthropods such as trilobites has been performed (e.g. Clarkson ; Schoenemann & Clarkson , ; Tanaka et al . ) due to the calcified lenses of their compound eyes.…”

The Phanerozoic aftermath of the Cambrian information revolution: sensory and cognitive complexity in marine faunas

“…Evidence of sophisticated information collection and processing comes from multiple studies of exquisite preservation in Cambrian fossils of complex eyes, other sensory organs, nervous systems, and brains (e.g., Chen et al 1999; Shu et al 2003; Paterson et al 2011; Ma et al 2012; Schoenemann and Clarkson 2013, 2017; Tanaka et al 2013; Cong et al 2014; Strausfeld 2015). Panarthropods (arthropods and their relatives), possessing a diversity of eyes and antennae and with brains resembling those of their modern counterparts (Ma et al 2012; Tanaka et al 2013; Cong et al 2014; Strausfeld 2015), were particularly dominant among the active and visually oriented fauna during this period (Zhao et al 2013).…”