Ammagnostidae, a family of trilobites in the suborder Agnostina, were small, eyeless, and isopygous, with a thorax consisting of two segments.
The family has four genera:
Ammagnostus Öpik, 1967 Ammagnostus psammius Öpik, 1967 (Type) Ammagnostus bassus (Öpik, 1967) Ammagnostus bella Guo & Luo, 1996 Ammagnostus beltensis (Lochman, 1944) Ammagnostus cryptus Ammagnostus cylindratus Guo & Luo, 1996 Ammagnostus duibianensis Lu & Lin, 1989 Ammagnostus histus Ammagnostus hunanensis Ammagnostus integriceps Öpik, 1967 Ammagnostus laiwuensis (Lorenz, 1906) Ammagnostus mitis Öpik, 1967 Ammagnostus sinensis Peng, 1987 Ammagnostus wangcunensis Peng & Robison Hadragnostus Öpik, 1967 Hadragnostus las Öpik, 1967 (Type) Hadragnostus edax Fortey & Rushton, 1976 Hadragnostus helixensis Jago & Cooper, 2005 Hadragnostus modestus (Lochman, 1944) Kormagnostus Resser, 1938 Kormagnostus simplex Resser, 1938 (Type) Kormagnostus boltoni Westrop et al., 1996 Kormagnostus copelandi Westrop et al., 1996 Kormagnostus flati Pratt, 1992 Kormagnostus inventus Shergold, 1982 Kormagnostus minutus (Schrank, 1975) Kormagnostus seclusus (Walcott, 1884) Proagnostus Butts, 1926 Proagnostus bulbus Butts, 1926 (Type) Proagnostus centerensis Resser, 1938 Proagnostus maryvillensis Resser
These trilobites lived during the late Cambrian and Ordovician periods.
References https://www.biolib.cz/en/taxon/id456979/ http://www.trilobites.info/ordagnostida.htm