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The Caudofoveata or Chaetodermomorpha are small, worm-like aberrant , ranging in length from 2 mm - 14 cm. They construct burrows in soft marine sediments which they inhabit head downwards. They ingest sediment, or may be selective carnivores or scavengers. Many typical molluscan characteristics are either absent or reduced. There is no shell, no foot, and the covers the entire body. Lacking a foot, they move by (like other primitive burrowing ). They are (male and female reproductive organs in separate individuals). The posterior body cavity (believed to represent the ) houses a pair of gills (). The (skin) contains layers of embedded calcareous . Most specimens have been collected by dredging, and relatively little is known about them. About 70 described living species of this class.
The Caudofoveata and are generally combined to form the class , although this practice is becoming discontinued as the differences between these two small primitive groups become known. For example, unlike Solenogastres, chaetoderms lack a .
Like the Solenogastres, Caudofoveata are of great phylogenetic interest, and their precise evolutionary relationships are still unclear. Salvini-Plawen (1980) sees them as the sister group to all other molluscs, being little changed from the first "Scutopoda" (original burrowing forms). Bergström suggests that they may be surviving members of the , the ancestral -bearing early Metazoa. However, work by Haszprunar (2000) indicates that Solenogastres are the most underived forms, with chaetoderms derived from them and higher (shell-bearing) molluscs next.
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