Upper Tithonian Himalayitidae Spath, 1925 (Perisphinctoidea, Ammonitina) from Le Chouet (Drôme, France): implications for the systematics

Abstract

This contribution focuses on the late Tithonian ammonite faunas belonging to the Family Himalayitidae Spath in the key-section of Le Chouet (Drôme, France). The great majority of specimens from the Mediterranean Tethys, previously referred to Durangites Burckhardt, are now interpreted as juveniles and/or microconchs of the highly variable species Protacanthodiscus andreaei (Kilian). Moreover, comparison between specimens from France, Spain and Bulgaria formerly assigned to Durangites astillerensis Imlay and the type material of this species, supports the introduction of Boughdiriella chouetensis gen. nov. et sp. nov. Further, the revision of the type specimens of D. astillerensis and Durangites of the D. vulgaris group shows that the former species deserves a new generic status, for which Parrasiella gen. nov. is erected. Toucasiella, previously only known from Spain and Tunisia, is also reported for the first time from south east France. The revision of the "Mediterranean Durangites" supports the rejection of a Durangites spp. Zone as part of the standard zonation for the upper Tithonian, and its replacement by the P. andreaei Zone ( = D. vulgaris Zone sensu Sarti, 1988).

Systematic palaeontology of the Perisphinctoidea in the Jurassic/Cretaceous boundary interval at Le Chouet (Drôme, France), and its implications for biostratigraphy

“…The distinction of two morphological groups, based on the ontogenetic sequence, strongly suggests intraspecific dimorphism, as already documented in Protacanthodiscus andreaei by Frau et al (2015). However, none of the specimens at our disposal, or illustrated in the literature, show the structure of the peristome.…”

“…Malbosiceras malbosi (Pictet, 1867) and Mazenoticeras broussei (Mazenot, 1939). The same is true for Protacanthodiscus and its type species Protacanthodiscus andreaei (Kilian, 1889), recently revised by Frau et al (2015).…”

“…12), several changes have been made by Bulot et al (2014) and Frau et al (2015), to which the reader is referred. It should be noted that the previous report of Dalmasiceras cf.…”

“…Previous articles (Bulot et al 2014;Frau et al 2015) concentrated on the families Ataxioceratidae Buckman, 1921, Himalayitidae Spath, 1925 and the first representatives of the Neocomitidae Salfeld, 1921 from the upper Tithonian. Herein we focus on the Perisphinctoidea taxa that were originally reported by Wimbledon et al (2013) from the Jacobi Zone auctorum.…”

“…The diachronism between the base of the Jacobi Zone auctorum and those of the Calpionella Zone notably alters the definition of the base of the Berriasian in the sense of the 1975 colloquium on Jurassic/Cretaceous boundary based on the view of Enay and Geyssant (1975). Bulot et al (2014) and Frau et al (2015) described and illustrated Perisphinctoidea taxa from the Microcanthum and Andreaei zones at Le Chouet. The present contribution ends the systematic description by the revision of the rest of the taxa of the Jacobi Zone auctorum.…”