Diastylida

Diastylida is a suborder of crustaceans belonging to the order Cumacea. Cumaceans, commonly known as hooded shrimp or comma shrimp, are small, bottom-dwelling marine crustaceans. The suborder Diastylida encompasses a significant portion of cumacean diversity and is characterized by several morphological features. Members of Diastylida typically possess a carapace that is fused to the first thoracic segment, forming a distinct "hood." They have five pairs of thoracic appendages, with the first two pairs being chelipeds (pincer-like limbs) used for feeding and defense.

The pleopods, or abdominal appendages, are reduced in Diastylida. Males usually have two pairs of pleopods, while females often have only one pair or none at all. The telson, the posterior tip of the abdomen, is also a distinguishing feature, often being distinctly shaped and sometimes bearing spines. Diastylida are found in a wide range of marine environments, from shallow coastal waters to the deep sea, and inhabit various substrates including sand, mud, and gravel. They are deposit feeders, consuming organic matter from the sediment. The classification within Diastylida includes several families, such as Diastylidae, Gynodiastylidae, and Pseudocumidae, each with further distinctions in their anatomical features and ecological roles.