Spengelidae

Spengelidae is a family of worms belonging to the class Enteropneusta, order unknown. The larvae of one of its species, Schizocardium californicum, are known for not expressing Hox genes.

Genera:
 * Glandiceps Spengel, 1891
 * Mazoglossus Bardack, 1997
 * Schizocardium Spengel, 1893
 * Spengelia Willey, 1898
 * Willeyia Punnett, 1903