Trocholites Conrad, 1838 (Nautiloidea, Tarphycerida) in the Middle Ordovician of the Prague Basin and its palaeobiogeographical significance

Abstract

in the Middle Ordovician of the Prague Basin and its palaeobiogeographical significance TÌPÁN MANDANautiloids of the order Tarphycerida are a characteristic component of warm-water Ordovician faunas of Baltica and Laurentia but are usually absent from the cooler high latitude marine environments. The presence of the tarphycerid Trocholites, reported from the Middle Ordovician, Dobrotivian (late Darriwilian) strata of the Iberian Chain and Armorican Massif (peri-Gondwanan Europe), provide an exception. Lituites primulus Barrande, 1865, represented by a single poorly-preserved individual was reported from coeval strata in the Prague Basin (Perunica) and doubtfully assigned to Curtoceras or Trocholites. New biostratigraphicaly well-constrained specimens of Trocholites described and discussed from the early Dobrotivian of the Prague Basin, are conspecific with Trocholites fugax previously described from the Iberian Chain and Armorican Massif. The contemporaneous presence of Trocholites fugax in Perunica and peri-Gondwanan terranes is additional evidence for faunal connections between these microcontinents during the Dobrotivian. By comparison with the preceding Llanvirnian (early Darriwilian) fauna, the low diversity Dobrotivian cephalopod fauna of the Prague Basin suggests an increasing faunal separation between Perunica and Baltica. The occurrence of Trocholites in early Dobrotivian strata of Perunica, the Iberian Chain and Armorican Massif reflects an unusual dispersion event of tarphycerids into lower latitude seas coinciding with a distinct climate perturbation during the Ordovician.•

A revision of the Ordovician cephalopod Bactrites sandbergeri Barrande: Systematic position and palaeobiogeography of Bactroceras

“…The Šá rka Formation contains the most diversified cephalopod fauna in the whole Ordovician of the Prague Basin (Marek, 1999). The fossil record includes endocerids, actinocerids (''Orthoceras'' bonum) and ellesmerocerids (Bathmoceras complexum), but the most common elements are pseudorthocerids and orthocerids (Mergl, 1978;Manda, 2008). The occurrence of ellesmerocerids, actinocerids and endocerids suggests enhanced faunal exchange between Perunica and Baltica (Marek, 1999).…”

Bivalves from the Middle Ordovician Šárka Formation (Prague Basin, Czech Republic)

“…Highly diversified echinoderm fauna includes fourteen species, of which stylophoran taxa are dominant. Cephalopods represent mainly demersal predators (ellesmerocerids, endocerids, pseudoortocerids) and planktic orthocerids (Manda 2008a). Phyllocarids are widespread, but monotonous Caryocaris.…”

Two more Bohemian trilobites from the Ordovician of Portugal and Morocco

“…In addition to the present form, the group also includes the benthic trilobites Placoparia (Coplacoparia) borni Hammann, 1971 [= P. (C.) antiopa Moravec, 1990 according to Havlíček & Vanek 1996] and Eccoptochile mariana Verneuil & Barrande, 1855[= E. vipera Moravec, 1986 according to Havlíček &Vanek 1996 andVanek &Valíček 2001], both recorded from the late Dobrotivian; the nektobenthic Parabarrandia crassa (Barrande, 1872), sporadically represented in some late early Dobrotivian localities of Ibero-Armorica; the diploporid Calix purkynei (Klouček, 1917), which occurs in the earliest Dobrotivian of Spain and at a single Bohemian locality, and the cephalopod Trocholites fugax (Babin & Gutiérrez-Marco, 1992). The latter is linked to a common episode of climatic disturbance in northern Gondwana (Babin & Gutiérrez-Marco 1992, Manda 2008. Similarly, the discovery of Ectillaenus benignensis (Novák, 1918) in the Dobrotivian of Morocco represents the first fully benthic trilobite apparently coeval in North Africa and Bohemia during the late Darriwilian, apart from some of the nekto-benthic species of Selenopeltis reported by Bruton (2008).…”