Derivation The Posttornoceratidae are derived from the
Falcitornoceratidae through
Exotornocers (Saunders et al. 2004)
Taxonomic divisions Subfamilies The family has been split into two subfamilies each containing two genera. Slightly older are the lower to middle Famennian Posttornoceratinae, followed by the later Famennian Discoclymeniinae. The Posttornoceratinae contains
Exotornocers and
Posttornoceras, the Discoclymeniinae,
Discoclymenia and
Alpinites.
Genera Posttornoceras, type genus of the Posttornoceratinae was named by Wedekind in 1910.
Posttornocerashas a subglobular to discoidal shell with a small, closed umbilicus and biconvex growth lines (Miller et al. 1964). Sutural lobes next to the ventral lobe are formed adventitiously in the first latera saddles.
Posttornoceras is derived from
Exotornoceras (Saunders et al. 2004) and has been found in Upper Devonian sediments in Germany and Poland (Miller et al. ibid)
Exotornoceras is the ancestral tornoceratid, named by Becker in 1993.
Exotornoceras is derived from
Gundolficeras( Falcitornoceratinae)
Discoclymenia is the type of the Discoclylemniinae, named by Hyatt in 1844. Discoclymenia has a subglobular to discoidal shell with a small, closed umbilicus, like
Sporadoceras but with additional adventitious lobes in the 1st lateral saddles.
Discoclymenia" and "Sporadoceras are included in the subfamily Sporadoceratinae of Miller and Furnish (1964) along with
Praeglyphioceras according to Miller et at (1964) .
Discoclymenia comes from the Upper Devonian of Europe and North Africa.
Alpinites was named by Bogolsovsky in 1971 and is derived from Discoclymenia (Saunders et al. 2004). ==References==