Evolution of the rudist bivalve Agriopleura Kühn (Radiolitidae, Hippuritida) from the Mediterranean region

Abstract

The genus Agriopleura (Radiolitidae) is restricted to the Lower Cretaceous of the Mediterranean region, including the Middle East, and this rudist is apparently absent from the New World. Agriopleura underwent a size increase from late Hauterivian to mid‐late Barremian, matching Cope's rule, followed by a Lilliput phase in the early Aptian. The relative development of radial bands increased through time and represents a key evolutionary index. During its evolution, Agriopleura increased in species diversity and expanded geographically onto the European Mediterranean Tethyan margin from the late Hauterivian to Barremian, after which it disappeared from the region (pseudotermination). In the lower Aptian, after a Lazarus gap, the genus reappears in the southern Mediterranean Tethyan margin. Assuming that Archaeoradiolites is the direct descendant of Agriopleura, the disappearance of the genus in the mid‐Aptian was a pseudoextinction and this coincided with a major crisis of shallow carbonate settings and their associated biota. The definition of Agriopleura species is based on a set of qualitative and quantitative external and internal characters. Five species are recognized: three Barremian species, Agriopleura blumenbachi, the type species, A. marticensis and A. carinata; one lower Aptian species A. libanica; and a new species A. sequana restricted to the upper Hauterivian. Principal component analysis is used to test the distinctiveness of the species and the pattern of relationships of some of their key quantitative characters.

Mid‐Cretaceous rudists (Bivalvia: Hippuritida) from the Langshan Formation, Lhasa block, Tibet

“…The most primitive genus of the Radiolitidae is Hauterivian – lower Aptian Agriopleura (Sano and Masse ; Skelton ; Masse and Fenerci‐Masse ), and the compact nature of its outer shell layer makes it a natural candidate for the ancestry of Auroradiolites (see , above). Agriopleura is distributed in the Mediterranean and Middle East regions, but questionably also in Mexico (Masse and Fenerci‐Masse , ).…”

“…The Mediterranean to Middle Eastern lower Aptian species A. libanica (Astre, ), recently reviewed by Masse and Fenerci‐Masse (), is both stratigraphically and palaeobiogeographically closest to the south‐west Asian examples of Auroradiolites . It is characterized by a concave LV , a relatively thick, entirely compact outer shell layer, and the presence in the LV of downwardly projected myophoral bulges (distinct from true plates; Skelton and Masse ; Fenerci‐Masse et al .…”

“…It is characterized by a concave LV , a relatively thick, entirely compact outer shell layer, and the presence in the LV of downwardly projected myophoral bulges (distinct from true plates; Skelton and Masse ; Fenerci‐Masse et al . ; Masse and Fenerci‐Masse ). The differences between Auroradiolites and Agriopleura are as follows: (1) the LV of Auroradiolites is almost flat to strongly convex, contrasting with the concave, lid‐like LV of Agriopleura ; (2) the LV myophores of Auroradiolites are more robust, looking like protruding plates as in other radiolitids, while the LV myophores of Agriopleura project only as low buttresses; (3) the ligamentary infolding of Auroradiolites is more strongly developed, producing an elongate inward extension of the ol with a widely forked inner termination in the RV , whereas the ligamentary infolding of Agriopleura is much shorter and is triangular in transverse section.…”

Aptian–Albian rudist bivalves (Hippuritida) from the Chilean Central Andes: Their palaeoceanographic significance

“…The above descriptions show that Hippurites chilensis d'Orbigny lack the generic attributes of this genus: mainly the shell infoldings of the RV and the canaliculated and porous structure of the LV (Skelton, 2013a). Similarly it does not match the characters of Agriopleura: mainly the protruding myophores of the LV, usually depressed, and the salient bands, depressed interband and inconspicuous ligament groove of the RV (Masse and Fenerci-Masse, 2014).…”

New Insights into the Platform-to-basin Anatomy of the Urgonian Bas-Vivarais Domain (Lower Cretaceous; SE France)

“…The first event remains poorly investigated to date while the second one marks the supraregional extinction of the genusi.e., the 'Agriopleura Event'at the scale of the eastern European rudist province. This extinction is thought to have resulted from a combination of cooling, anoxia, platform exposure and change in the trophic factor, leading to the selective removal of these elevator rudists [35][36].…”