EEMB 136L Lecture Notes - Lecture 12: Cephalon, Trilobite, Refractive Index
15 Nov 2017
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Calcitic exoskeleton divided into cephalon, thorax and pygidium. Most are bottom-dwellers, crawling on the sea floor, or within reefs, acting as scavengers, deposit feeders, and predators. Facial suture where the trilobite"s exoskeleton broke open during molting to allow the animal to escape. Line between the eye/ palpebral lobe and the cheek on the cephalon. Raised central hump on the dorsal side of the cephalon. Divided into parallel thoracic segments that are hinged to one another. Center of each segment is humped up into an axial ring which aligns with the glabella. Each segment of the pleural lobes are called pleura. Doublure: each pleuron is curved inward at extremity. During enrollment when under attack, the doubleure would seal all the way around and enclose the soft parts of the trilobite. Tend to have a large, semicircular cephalon with strong genal spines. Natant (aka floating) hypostomes (not attached to the cephalic doublure)
