Tithonia oxfordiana, a new irregular echinoid associated with Jurassic seep deposits in south‐east France

Abstract

Abstract:The infaunal irregular echinoid, Tithonia oxfordiana, is described and compared to congeneric species previously described from Upper Jurassic and lowermost Cretaceous strata. This new species characterizes a monospecific echinoid assemblage, which occurs only in some places where deep-marine middle Oxfordian deposits are exposed in south-east France. Specimens are closely packed and clearly concentrated at the top of small carbonate chemoherms; a close connection of the echinoids with the emission of reduced chemicals, which were oxidized by chemoautotrophic bacteria, is highly probable. Based on general test shape and plate architecture, T. oxfordiana probably was a deposit feeder on chemosynthetic organic matter produced by such bacteria. In view of the fact that T. oxfordiana is the sole species of the Jurassic genus Tithonia known from Oxfordian strata, it is postulated that chemoherms possibly acted as refugia for these peculiar echinoids, which have an episodic record between the Callovian and Valanginian.

Oxfordian neptunian dykes with brachiopods from the southern part of the Kraków-Częstochowa Upland (southern Poland) and their links to hydrothermal vents

“…The source of nourishment for echinoids may also have been free-living bacteria settled in the neighborhood of fractures or microbial mats flourishing close to seep deposits during the activity of hydrothermal vents or during the final phase of chemoherms in the basin (cf. Gaillard et al 2011).…”

Experimentally observed soft‐tissue preservation near a marine brine seep

“…In addition, echinoids naturally occur near seeps and in some instances can occur in large monospecific assemblages near seeps (Gaillard et al . ), such that there is a possibility of the preservation noted in this study to occur naturally.…”

Absurdaster, a new genus of basal atelostomate from the Early Cretaceous of Europe and its phylogenetic position

“…It does, however, include a number of characters not employed by Barras (2007) which may help to better resolve the divergence of ‘disasteroids’ and stem-group members of the holasteroid and spatangoid clades. Moreover, additional data on some of the taxa included in these two analyses have become available, mainly on Cyclolampas ( Saucède et al., 2013 ) and Tithonia ( Gaillard et al., 2011 ). To better resolve the relationship of Absurdater the taxon set was restricted to forms found to be stem-group atelostomates in the previous analyses.…”