Mid-Jurassic Ammonitina from the Central Ranges of Irian Jaya and the origin of stephanoceratids

Westermann, Gerd E. G. (1995) Mid-Jurassic Ammonitina from the Central Ranges of Irian Jaya and the origin of stephanoceratids. Hantkeniana, 1. pp. 105-118. ISSN 1219-3933

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Abstract

Selected specimens from the Seo and Suzuki ex-situ collections of mainly Bajocian Ammonitina from the Central Ranges of Irian Jaya are described and their phylogeny and/or paleobiogcography discussed. Riccardiceras gen. nov., type species Coeloceras longalvum Vacek from (late) Aalenian-Early Bajocian of the Alps, is named to distinguish serpenticone “Docidoceras ” (lately placed in Stephanoceras) from the sub-spherocone Docidoceras s. str. Riccardiceras is the phylogenetic link between the Erycites gr. gonionotus-Abbasitoides [Erycitidae], and Stephanoceras s. 1. [Stephanoceratidae], i.e. in parallel to the lineagc Erycites(?) gr.fallifax - Docidoceras - Emileia etc. [Otoitidae], Macroconch shape and sculpture of Riccardiceras resemble early Stephanoceras, but also intergrade with contemporary Docidoceras-, septum/suture and the microconch morphology are close to Docidoceras. Riccardiceras suzukinense sp. nov. is most closely allied to G. limatum (Pompeckj).

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