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Antaganides n. gen., a new genus of Middle Jurassic nautiloid, ancestor of Pseudaganides Spath, 1927, with discussion on the phyletic origin of the family Pseudonautilidae

Patrick BRANGER

en Geodiversitas 46 (14) - Pages 471-493

Published on 03 October 2024

An important collection of nautiloids from the Middle Jurassic of western France has enabled a revised understanding of the origin and evolutionary progression of the genus Pseudaganides Spath, 1927, a genus characterised by a particularly sinuous suture line. This study describes and introduces a new genus, Antaganides n. gen. at the origin of the family Pseudonautilidae. Progressive deepening of the lateral lobe and appearance of a laterodorsal saddle are the major elements of the evolutionary mode within this family. Of the species described herein, six are new. Three are related to Antaganides n. gen.: A. sauvageti n. gen., n. sp., A. fournieri n. gen., n. sp. and A. grulkei n. gen., n. sp. Three further specimens are related to Pseudaganides: P. aquitanense n. sp., P. buffeventi n. sp. and P. crechensis. Results confirm the absence of a relationship with older folded-wall nautiloids such as the genus Belmonticeras Rulleau, 2008. The stratigraphical position of Pseudaganides subbiangulatus (d’Orbigny, 1850) is questioned and for this species, a case of sexual dimorphism is considered with P. dimidiatus (Marchand & Tintant 1971). From a palaeobiogeographic viewpoint, it appears that the Antaganides n. gen.-Pseudaganides lineage first evolved on the north-western margin of the Tethyan Ocean before migration into the Indo-Malagasy domain at the beginning of the Callovian.


Keywords:

Jurassic, Bajocian, Bathonian, Callovian, Nautilida, biostratigraphy, cephalopods, evolution, new combination, new genus, new species

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