Some Upper Jurassic ammonites of the genus Ringsteadia Salfeld, 1913, from Central Poland

Abstract

A few species of ammonites of the genus Ringsteadia Salfeld, 1913, from the Uppermost Oxfordian (Idoceras planula zone) and Lowermost Kimmeridgian (Sutneria platynota zone) of the northern part of the Cracow-Częstochowa Jurassic Chain, Central Poland, are described. The species presented, known from Southern Germany, are of the “submediterranean” type and markedly differ from the “boreal” species from England and Normandy. This fact, as well as the other observations, enable setting forth the hypothesis on two ammonite lineages of the genus Ringsteadia which occurred at the turn of the Oxfonian to the Kimmeridgian, that is, (1) the “boreal” lineage in England and Normandy from which the ammonites of the genus Pictonia originated (cf. Morris 1968) and (2) the “submediterranean” lineage in Southern Germany, Southern France and Poland, which probably gave rise to various ammonites of the genera Rasenia (Eurasenia, Involuticeras) and Pomerania (Pachypictonia).