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

2008; Linguagem: Inglês

10.3140/bull.geosci.2008.03.327

1802-8225

Štěpán Manda,

Geology and Paleoclimatology Research

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