Ptychoderidae

Ptychoderidae is a family of acorn worms.

Genera and species
The World Register of Marine Species lists the following:

Balanoglossus
Contains the following species:
 * Balanoglossus apertus (Spengel, 1893)
 * Balanoglossus aurantiacus (Girard, 1853)
 * Balanoglossus australiensis (Hill, 1894)
 * Balanoglossus borealis (Willey, 1899)
 * Balanoglossus capensis (Gilchrist, 1908)
 * Balanoglossus carnosus Müller in Spengel, 1893
 * Balanoglossus clavigerus delle Chiaje, 1829
 * Balanoglossus gigas Müller in Spengel, 1893
 * Balanoglossus hydrocephalus van der Horst
 * Balanoglossus misakiensis Kuwano, 1902
 * Balanoglossus natalensis (Gilchrist, 1908)
 * Balanoglossus occidentalis Ritter, 1902
 * Balanoglossus proterogonius Belichov, 1928
 * Balanoglossus robinii author unknown
 * Balanoglossus salmoneus Belichov, 1928
 * Balanoglossus stephensoni van der Horst, 1937
 * Balanoglossus studiosorum van der Horst

Glossobalanus
Contains the following species:
 * Glossobalanus alatus van der Horst
 * Glossobalanus barnharti Cameron & Ostiguy, 2013
 * Glossobalanus berkeleyi (Willey, 1931)
 * Glossobalanus crozieri van der Horst, 1924
 * Glossobalanus elongatus Spengel, 1904
 * Glossobalanus hartmanae Cameron & Ostiguy, 2013
 * Glossobalanus hedleyi (Hill, 1897)
 * Glossobalanus indicus Rao, 1955
 * Glossobalanus marginatus Meek, 1922
 * Glossobalanus minutus Kowalevsky, 1866
 * Glossobalanus mortenseni van der Horst, 1932
 * Glossobalanus parvulus (Punnett, 1906)
 * Glossobalanus ruficollis (Willey, 1899)
 * Glossobalanus sarniensis (Koehler, 1886)
 * Glossobalanus williami Cameron & Ostiguy, 2013

Ptychodera
Contains the following species:
 * Ptychodera bahamensis Spengel, 1893
 * Ptychodera ceylonica author unknown
 * Ptychodera erythrea Spengel
 * Ptychodera flava Eschscholtz, 1825
 * Ptychodera pelsarti Dakin, 1916