Taxonomic revision of the rudist bivalve genus Joufia Boehm (Hippuritida, Radiolitidae), Upper Cretaceous, Mediterranean Tethys

Abstract

The rudist genus Joufia Boehm is characterized by radially oriented canals within the calcitic outer shell layer of the left valve. The type species, J. reticulata, has multiple rings of canals. However, a single ring of such canals is observed in the left valves of some other nominal radiolitid genera. One such is Kuehnia serbica Milovanović, recognized herein as a species of Joufia, to which we also re-assign Parasauvagesia cappadociensis Cox.

Pseudokuehnia Slišković and other material historically attributed to Kuehnia share with J. serbica: (i) the single ring of radial canals in the left valve; (ii) similar right valve ornamentation; (iii) identical celluloprismatic mesostructure and pseudopillar-like structures in the right valve; plus pallial canals in the left valve, as seen in Joufia reticulata. Additionally, the left valve of Pseudokuehnia has a postero-ventral pair of tubular structures; and the same characters are also seen in Kurtinia Karacabey-Öztemür, herein regarded as synonymous with the latter taxon.

Hence, we recognize three Joufia species: (1) J. reticulata Boehm, with multiple canal rings in the left valve; (2) J. serbica (Milovanović), with a single ring of such canals; and (3) J. milovanovici Slišković, also with a single ring of canals, but additionally with paired tubular structures in the left valve. The same tripartite division exists among specimens from latest Campanian-Maastrichtian deposits in Turkey.

Thus revised, Joufia ranged across the Mediterranean Tethys from Turkey via the Balkans to Italy and SE Spain, and as far south as central Tunisia and SE Turkey.

Introduction

The family Radiolitidae d’Orbigny (1847) is mainly characterized by a myocardinal apparatus consisting of two sub-equal to equal, prong-like teeth, flanked by outwardly-facing myophores in the left valve (LV), together forming a crescentic array that projects into the right valve (RV), in which the central tooth is reduced to a salient ridge between the tooth sockets (or is even secondarily lost) and the adductor muscle scars are situated on the inner surface of the valve's general cavity; moreover, the LV is generally operculiform to capuloid in form and the RV conical to cylindroconical, with two distinctly ornamented radial bands (infolded in some genera to form pseudopillars) on the postero-ventral flank. The diagnostic rudist outer shell layer of fibillar calcite (Skelton, 2018) is usually thickened, with a finely layered cellular (‘celluloprismatic’) mesostructure developed in most genera (Dechaseaux and Coogan, 1969; Steuber, 1999; Pons and Vicens, 2008; Skelton, 2013a). The original calcite of the outer shell layer is commonly well-preserved, while the original aragonite of the inner shell is usually recrystallized or dissolved away (Skelton, 1974, 1978).

Based on published descriptions there are many radiolitid genera that additionally possess canals penetrating the interior of the LV, described mainly from the Upper Cretaceous of the Old World (e.g. Milovanović, 1956; Polšak, 1965; Slišković, 1968; Pejovıć, 1968, Pejović, 1984; Karacabey, 1969, Karacabey, 1972, Karacabey, 1974; Karacabey-Öztemür, 1980; Campobasso and Morolla, 1975; Sladić-Trifunović, 1981a; Slišković, 1986/1987; Özer, 1988, Özer, 1992a; Özer and Fenerci, 1993; Sarı and Özer, 2009) though some also evolved independently in the New World (Alencáster and Pons, 1992). In such radiolitids canals are present in either or both of the calcitic outer shell layer and/or the aragonitic inner shell. Although these canaliculate genera include approximately one third of the family, their taxonomic status and determinations are much debated, with controversial synonymies proposed in numerous studies (e. g. Karacabey, 1969; Pejović and Sladić-Trifunović, 1977; Karacabey-Öztemür, 1980; Karacabey-Öztemür and Selçuk, 1981; Sladić-Trifunović, 1981a, b; Pejović, 1984; Slišković, 1986/1987; Özer, 1988, Özer, 1992a; Alencáster and Pons, 1992; Morris and Skelton, 1995; Steuber, 1999; Skelton, 2003; Mitchell and Ramsook, 2009; Skelton, 2013a, b).

The aim of the present study is to revise some radiolitid genera in which radial canals are developed in the calcitic outer shell layer of the left valve in a single, or multiple ring(s), namely Kuehnia Milovanović, 1956, Pseudokuehnia Slišković, 1968 and Kurtinia Karacabey-Öztemür, 1980 and to propose their synonymy with the genus Joufia Boehm, 1897.