Acta Palaeontologica Polonica

Some remarks on the origin of the subfamily Idoceratinae Spath, 1924 (Perisphinctidae, Ammonoidea)

Wojciech Brochwicz-Lewiński

Acta Palaeontologica Polonica 18 (3), 1973: 299-320

Simoceratids (Idoceratinae) represent a peculiar group of Upper Jurassic ammonites typical of the Tethyan province. The earliest Idoceratinae, the genera Idoceras and Nebrodites, were thought to appear not before the uppermost Oxfordian. However, in Mid-Oxfordian strata of the Polish Jura Chain there occur some ammonites closer to Kimmeridgian nebroditids than to co-occurring perisphinctids. These forms, separated here as the subgenus Passendorferia nov. of the genus Nebrodites, most probably evolved from some Kranaosphinctes and lead to Nebrodites proper. The nominal genus of this subfamily, Idoceras Burckhardt, 1906, presumably represents a side-branch of nebroditids.

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