Maxillopoda Temporal range: Cambrian to Recent
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Cyclops (Copepoda: Cyclopoida) | |
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Class: | Maxillopoda Dahl, 1956 [1]
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Maxillopoda is a diverse class of crustaceans which includes the barnacles, copepods and a number of related animals.
It does not appear to be a monophyletic group, and no single character unites all the members.[2]
With the exception of some barnacles, maxillopodans are mostly small,[3] including the smallest known arthropod, Stygotantulus stocki.[2] They often have short bodies, with the abdomen reduced in size, and generally lacking any appendages [3] This may have arisen through paedomorphosis.[3]
Apart from barnacles, which use their legs for filter feeding, most maxillopodans feed with their maxillae. Their bodyplan has 5 head segments, 6 thoracic segments and 4 abdominal segments, followed by a telson (tailpiece).[4]
The fossil record of the group extends back into the Cambrian, with fossils of barnacles and tongue worms known from that period.[5][6]
Six subclasses are generally recognised, although many works have included the ostracods among the Maxillopoda.[2] Of the six groups, only Mystacocarida are entirely free-living; all the members of the Tantulocarida, Pentastomida and Branchiura are parasitic, and many of the Copepoda and Thecostraca are parasites.