Pseudotachidiidae is a family of marine benthic copepods in the order Harpacticoida. Members of this family are small, typically ranging from about 0.2 to 1.5 mm in length, and are adapted to living in marine sediments, including both shallow coastal and deep-sea environments. Pseudotachidiidae are primarily deposit feeders in sedimentary habitats and form an important component of meiofaunal communities, particularly in deep-sea settings where they can be among the dominant harpacticoid families. == Morphology == Pseudotachidiidae exhibit typical harpacticoid body form: elongate, dorsoventral
FAMILY
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Pseudotachidiidae is a family of marine benthic copepods in the order Harpacticoida. Members of this family are small, typically ranging from about 0.2 to 1.5 mm in length, and are adapted to living in marine sediments, including both shallow coastal and deep-sea environments. Pseudotachidiidae are primarily deposit feeders in sedimentary habitats and form an important component of meiofaunal communities, particularly in deep-sea settings where they can be among the dominant harpacticoid families. == Morphology == Pseudotachidiidae exhibit typical harpacticoid body form: elongate, dorsoventrally flattened, with a cephalothorax and slender urosome ending in caudal rami. Diagnostic characters include antennule segmentation, setation patterns on thoracic legs P1–P4, caudal ramus morphology, and pronounced sexual dimorphism in males (especially antennules and fifth legs). Female antennules are usually 6–8 segmented; male antennules are often geniculate. Antennae have 1–2 exopodal segments with genus-specific setation. Swimming legs are biramous; deep-sea species frequently show reductions in inner setae on P2–P4 exopods. Caudal rami vary in shape and armature (typically seven setae, sometimes reduced). Mouthparts are adapted for detritivory. == Distribution and habitat == The family has a cosmopolitan distribution in marine environments, recorded from intertidal and subtidal sediments to abyssal depths exceeding 5,000 m. Species occur in diverse habitats including coastal muds, continental slopes, submarine canyons, abyssal plains, and structured deep-sea substrates. They are particularly diverse and abundant in deep-sea harpacticoid assemblages, often ranking among the most species-rich families alongside Ameiridae, Argestidae, and Ectinosomatidae. Records include the Angola Basin, Weddell Sea, northwestern Pacific abyssal plains, Kara and East Siberian Seas, and coastal waters of South Korea. == Taxonomy == The family Pseudotachidiidae was established by Lang in 1936. It currently includes four subfamilies: Danielsseniinae, Donsiellinae, Pseudomesochrinae, and Pseudotachidiinae. === Genera ===
Selected genera include:
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