Porambonitidae DAVIDSON , 1853

Mergl, Michal, 2013, Porambonites Havliceki Sp. Nov., A New Brachiopod From The Šárka Formation (Darriwilian) From Bohemia And Its Contribution To Early History Of The Porambonitidae, Acta Musei Nationalis Pragae Series B 69 (1 - 2), pp. 87-92 : 88

Family Porambonitidae DAVIDSON, 1853

R e m a r k s. Radial rows of minute pits (fenestrate microornament) is not confined only the stratigraphically later species of Porambonites ( Popov et al. 2005) . Orthid-like genus Poramborthis HAVLÍČEK, 1949 , recently referred to tetralobulids ( Mergl 2011), also has a multicostellate ornament with rows of minute pits, long dental plates, sessile ventral muscle field, weakly impressed muscle scars and digitate mantle canal system. The main difference between Porambonites and Poramborthis is the strophic shell, short notothyrial platform with the cardinal process, and very short brachiophore plates of the latter genus. These features likely disappeared in the early evolution of Porambonites , which took place in the Late Tremadocian or Floian. The loss of the cardinal process, an anterior extension of brachial plates, a reduction of interareas up to astrophic shell, and the development of uniplicate commissure became an autapomorphy of Porambonites .

There are few reports of assumed porambonitids in West Gondwana. Small shell fragments with multicostellate ornaments are known from the Klabava Formation (Dapingian) of the Prague Basin ( Mergl 1991), but their fragmental state of preservation and lack of any data about shell internal structures make these occurrences greatly useless for a porambonitid phylogeny. However, rows of circular pits (fenestrae) are discernible in shell fragments (Pl. 1, Fig. 11; see also Mergl 1991, pl. 4, fig. 1) and firmly assigned these fragments among the porambonitids.