Prosoma
The anterior body region of a chelicerate, bearing the eyes, mouthparts, and walking legs. In spiders it is also called the cephalothorax.
Chelicerata: An arthropod subphylum whose members bear chelicerae instead of antennae. The prosoma is the anterior body region shared across this group.
Spider: An arachnid in the order Araneae, with fangs, silk-producing organs, and two main body regions. Its prosoma is commonly called the cephalothorax and connects to the abdomen by a narrow pedicel.
Compound eye: An eye composed of repeated visual units called ommatidia. Compound eyes occur on the prosoma of horseshoe crabs and some other chelicerates.
Arachnid anatomy: The study of arachnid body structures, including their segments, appendages, and internal organs. The prosoma is a central region in descriptions of arachnid body plans.
Opisthosoma: The posterior body region of a chelicerate, behind the prosoma. It is the prosoma’s principal body-region counterpart.
Horseshoe crab: A marine chelicerate with a broad, horseshoe-shaped carapace and a long tail spine. Its large prosoma carries the eyes and most appendages.
Book lung: A respiratory organ made of stacked, leaflike tissue plates within a chamber. Unlike the eyes and legs, book lungs usually lie in the opisthosoma.
Arthropod segmentation: The organization of arthropod bodies into serially repeated segments and functional regions. Prosoma anatomy reflects the evolutionary grouping and specialization of anterior segments.
Chelicerae: The first pair of appendages in chelicerates, commonly modified into fangs or pincers. They are mouthparts attached to the prosoma.
Sea spider: A marine arthropod in the class Pycnogonida, with long legs and a reduced body. Its compact anterior trunk bears the proboscis and appendages, unlike the broad prosoma of many chelicerates.