Acaste downingiae Trilobite BIRUG 60853D Model
Silurian fossil trilobite Acaste downingiae from the Wenlock Limestone of Dudley, UK (433–427 million years ago). The eyes of this and other closely related trilobite species are known as “schizochroal”, meaning they possess a compound eye formed of a relatively small number of larger lenses, each with its own corneal membrane. The large change in angle from lens to lens would have resulted in a strong degree of astigmatism in this type of trilobite, meaning the trilobite could detect directional movement and possibly size, but not form. Although the shape of the eyes would have given the trilobite 360° vision horizontally, its vertical range of vision was very limited – possibly only 10° (Clarkson, 1966). This specimen was purchased from Charles Ketley in 1880 and forms part of the Museum’s Ketley Collection. Digitisation was carried out using an Artec Spider 3D scanner by Amir Rahman.