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Hypostome (trilobite)
The hypostome is the hard mouthpart of trilobites found on the ventral side of the cephalon (head). The hypostome can be classified into three types based on whether they are permanently attached to the rostrum or not and whether they are aligned to the anterior dorsal tip of the glabella.
== Morphology ==
The center of the hypostome is an ovoid, typically convex part called the median body, often divided into an anterior lobe and a posterior lobe. Either side of the median body is a border with various extensions, including anterior and posterior wings, sometimes bearing knob-like processes. The hypostome is hollow, and encloses the mouthparts, the anterior digestive tract, and the bases of the antennae. Trilobite antennae pass through notches between the anterior and posterior wings, then forward. The anterior wings are designed to rest firmly against internal structures (ventral apodemes) on the glabella.〔
Variation in trilobite hypostome morphology is crucial in modern discussions of trilobite phylogeny. Functional interpretations of hypostome shape also allow for reasonable speculation on the feeding habits of trilobite species.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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