Analysis of seventy published papers dealing with Mexican Upper Cretaceous rudists, together with consultation of the newest geological maps covering the areas with mentioned rudist fossil ...localities, evidenced that: a) several among the Turonian-Maastrichtian species mentioned are junior synonymies, nomen nudum, insufficiently described, or have untraceable types. According to modern standards, around sixty species seem acceptable, Antillocaprinidae (12), Hippuritidae (11), Plagioptychidae (9), and Radiolitidae (27). Only three species (Turonian) are common with Eurasia. All the Santonian-Maastrichtian rudists (54) are exclusively American species, either ascribed to Eurasian (9) or to American (21) genera. b) Research on rudists helped to improve the stratigraphy in some areas, and to point out or clear up some geological issues in others. c) The restudy of the geology in some areas, of some rudist collections in museums, and of some rudist groups, are much necessary and must be undertaken.
•Present knowledge of Mexican Upper Cretaceous rudists after analysis of seventy published papers.•Several mentioned species are junior synonymies,nomen nudum, insufficiently described, or have untraceable types. Sixty species seem acceptable.•Three Turonian species are common with Eurasia. All other species (54) are exclusively American.•Rudists helped to improve the stratigraphy and to point out or clear up geological issues in some areas.•The geology in some areas, some rudist collections in museums, and some rudist groups must be restudied.
A new species of the genus Pachytraga, P. carpathica sp. nov., is described from the Mediterranean Tethyan domain, identified in Barremian platform carbonates of Romania. The species was recorded in ...the Apuseni Mountains and the Carpatho-Balkan region in beds with a lower Barremian micropalaeontological assemblage. The evolutionary character of the new taxon is relatively primitive but represents a mosaic of the antecedent Pachytraga tubiconcha and succeeding Pachytraga paradoxa. This discovery potentially fills an evolutionary gap between the two former stratigraphically disjunct species, but the emergence of Pachytraga paradoxa remains problematic.
Multiple-fold hippuritid rudist bivalves –those having infolds of the outer shell layer into the inner shell layer (secondary pillars or rays) other than the three hippuritid pillars– from Eurasia ...have been referred to genus Pironaea Meneghini. The characters considered in taxonomy caused a somewhat confusing large number of Pironaea species in literature. The study of new material from SE Spain, E Serbia and E and SE Anatolia, stressing the taxonomic relevance of the ontogenetic and intraspecific variability, as well as published material from these or other areas, has resulted in reducing the number of species to three, besides P. milovanovici Kühn. Thus, a clearer and simpler taxonomic framework of Pironaea species, and their evolutionary relationship, is proposed. P. polystyla (Pirona) is recognized in N and S Italy, Slovenia, Croatia, E and W Serbia, W Bulgaria, Turkey, and UAE, including as junior synonyms P. anatolica Karacabey, P. buseri Pejović, P. dalmatinica Milovanović, P. dinarica Milovanović, P. fruscagorensis Milovanović, Sladić-Trifunović, Grubić, P. lisansis Pamouktchiev, P. machnitschi Wiontzek, P. praeslavonica Milovanović, Sladić-Trifunović, Grubić, P. sladici Pamouktchiev, and P. slavonica Hilber. P. corrugata (Woodward) is only recognized in E and SE Anatolia and not considered the primitive ancestor of the other species. P. transitoria Milovanović is recognized in SE Spain, N Italy, E and W Serbia, W Bulgaria, NW Turkey, and Tunisia and includes as junior synonyms P. branislavi Sladić-Trifunović, P. corrugata nicklesi Philip, P. garlensis Pamouktchiev, P. negrichorensis Pamouktchiev, P. pejovici Pamouktchiev, P. praeyaroslavensis Pamouktchiev, P. timacensis Milovanović, P. udinensis Pamouktchiev, and P. yaroslavensis Pamouktchiev.
•Thirty Pironaea species in literature are reduced to four:•P. corrugata, P. milovanovici, P. polystyla, and P. transitoria.•Different Pironaea species occur together at the same fossil locality.•Infolds are considered a convergent character.•Genus Pironaea appears to be polyphyletic.
The “Agriopleura event”, which expresses the regional extinction, in northwestern Europe, of the rudist genus Agriopleura, is associated with environmental and biological changes. This event marks ...the boundary between two distinctive late Barremian regional rudist assemblages, the pre-event Brouzet-les-Alès and post-event Orgon faunas. The succeeding Palorbitolina episode is coeval with a rudist eclipse. The ensuing Rustrel fauna identifies the phase of post-extinction recovery. The last occurrence of Agriopleura, the stem genus of the Radiolitidae, coincides with the extinction of 41% of the pre-event Requieniidae and Monopleuridae. The recovery phase is characterized by new species and a low extinction pattern. This phase is marked by a burst of speciation, in part indigenous and in part due to immigrants i.e. Caprinidae. The key morphotypes, clingers, elevators and recumbents record contrasting changes in specific diversity, clingers being dominant due to the substantial diversity of Requieniidae and Monopleuridae. During the extinction event elevators decrease and suffered a reduction in size, large size species being selectively eliminated. The entry of the Caprinidae identifies the recovery phase and accounts for size increase and an important contribution of recumbent. The main agent of the extinction, combines cooling, anoxia, platform exposure and a trophic factor assumed to account for the selective removal of the elevators. A dual partition in feeding behavior of clingers and elevators is suggested: elevators exploiting the phytoplankton flux and the re-suspended bottom biodeposits; and clingers feeding on the benthic boundary layer. Significant community changes are associated with Agriopleura extinction and its aftermath, which clearly respond to changes in taxonomic composition. Elevator dominated communities with the Agriopleura are replaced by polytaxic requieniid rich communities then by caprinids. The Palorbitolina episode, records a trophic peak, cooling and a deepening trend. The recovery phase mainly records an aragonitic pulse coupled with temperature increase.
•The “Agriopleura event” records a late Barremian regional extinction driven by cooling, trophic changes, and anoxia.•41% of pre-event Monopleuridae and Requieniidae species disappear.•The “Agriopleura event” is driven by cooling, trophic changes, and anoxia.•The recovery phase is characterized by 46% of new species and records an aragonite pulse and warming.
Variations in Aptian carbonate platform growth and associated turnover among rudists are reviewed and the results synthesized with evidence for climate change to yield an explanatory model. Extensive ...platform growth throughout the Atlantic/Tethys/low‐palaeolatitude Pacific seamount belt in the earliest Aptian was accompanied by prolific rudist diversification, especially among the predominantly aragonitic caprinids occupying platform margins. It was ubiquitously interrupted in the mid‐Early Aptian, in tandem with major perturbations of the global carbon cycle that culminated in Oceanic Anoxic Event 1a, although the causal linkages remain contentious. Platform growth terminated along most of the northern Tethyan margin and maybe also in the New World. Meanwhile, Lithocodium/Bacinella or similar microbial encrustations became widespread in lower palaeolatitudes. Recovery of Tethyan platforms in the late Early Aptian was limited to lower palaeolatitudes. Caprinid‐rich platform margin facies again prevailed in central and southern Tethyan areas, but gave way to those dominated by rudists with a thickened calcitic outer shell layer (polyconitids and requieniids) in marly successions around Iberia. The end of the Early Aptian saw the Lazarus‐style disappearance of caprinids, and renewed Tethyan platform growth in the Late Aptian was dominated by calcite‐rich rudists, although rudists remained scarce in the New World until the terminal Aptian. This study postulates that sea water acidification influenced both the mid‐Early Aptian platform debacle and the subsequent late Early Aptian geographical restriction of platform recovery, although in contrasting atmospheric regimes. At first, it was forced by the increasing atmospheric levels of volcanically derived CO2, with mitigation in low latitudes from thermal expulsion of aqueous CO2 (here termed the ‘kettle effect’) due to greenhouse warming. However, subsequent cooling due to drawdown of atmospheric CO2 by organic carbon burial could have sustained acidification of platform waters in higher latitudes, by reducing the protective kettle effect there. Caprinid susceptibility to such assaults may have been as much due to exposure on their preferred outer platform habitats as to their mineralogy. The increased calcite/aragonite ratio among rudists through the Aptian resulted largely from this taxonomic turnover.
A new species of Pachytraga (family Caprinidae) is described from the Forêt de Coulmes (Northern Vercors, Subalpine region of SE France) and dated from the Taveraidiscus hugii- Nicklesia nicklesi ...ammonite Zones (lowermost Barremian). Pachytraga gracilis sp. nov. has an undivided posterior myocardinal cavity on the left valve and an anterior myophore supported by a single row of rectangular canals. The right valve bears a row of anterior canals, a partitioned posterior perimyophoral cavity and a network of minute pallial canals on the dorsal side. The new species represents an evolutionary link in between the Hauterivian Pachytraga tubiconcha and the Late Barremian–early Aptian Pachytraga paradoxa, so shortening the West European Barremian Lazarus phase of the genus Pachytraga. The possibility of a Barremian p.p. ecological rather than geographical refuge is proposed. We consider the new species as a potential biostratigraphic marker of the West European lowermost Barremian. It is the oldest member of canaliculated Caprinidae. Number of traits of Pachytraga gracilis sp. nov. (shape, mode of canaliculation), are absent in its assumed descendant P. paradoxa, but present in other advanced taxa, Praecaprina, Caprina, hence the new taxon was a precursor in more ways than one.
The Gattar Member (upper part of the Zebbag Formation) is a prominent dolomitic limestone unit in Tunisia, the age of which was ascribed either to the Turonian, the Cenomanian, or the ...Cenomanian−Turonian. Here, we present the discovery of a Caprinulidae-Radiolitidae rudist asssemblage in the Gattar Member of Jebel el Kebar (central Tunisia). This consists of Caprinula cf. boissyi, Sauvagesia cf. sharpei, Durania arnaudi, Neocaprina sp. and Eoradiolites sp. The detailed description of two sections of the Gattar Member in Jebel el Kebar allows us to define the sedimentological and palaeoecological attributes of the rudist-bearing carbonates and their sequential relationships with the Zebbag and Rouana stratigraphical units respectively. The caprinulid-radiolitid assemblage is age-calibrated, based on the ammonite standard zonation of the Cenomanian stage from Portugal, South-Eastern France, and Oman, where rudist, benthic foraminifera and ammonite Zones have been correlated. Its age is late Cenomanian. The correlations of the Gattar Member between central Tunisia and the Gafsa-Chotts area are established on the base of ammonite and rudist biostratigraphical markers. The age of the Gattar Member of southern Tunisia and of its stratigraphical counterpart in western Libya is discussed. At last, we analyze the palaeobiogeographical distribution of the upper Cenomanian caprinulid-radiolitid assemblages from coeval carbonate platforms of the North African margin (Algeria, Morocco) and of the North Arabian margin (Levant region: Syria, Jordan, Lebanon, Israel, North Sinai).
•An upper Cenomanian caprinulid-radiolitid rudist assemblage is discovered in the Gattar Member of Jebel el Kebar (Tunisia).•The rudist markers assign the Gattar Member of Jebel el Kebar to the upper Cenomanian−lowermost (?) Turonian.•The stratigraphical correlations of the Gattar Member with the Gafsa-Chotts area and the southern Tunisia are discussed.•Palaeobiogeographical relationships are established with upper Cenomanian carbonate platforms of the southern Tethyan margin.•The rudist assemblage of the Gattar Member shows affinities with that of the upper Cenomanian carbonate platforms of Algeria.
The Coniacian carbonate sediments of the Iberian basin were deposited on a homoclinal ramp that grades upwards into a distally steepened ramp, with a major shoreline siliciclastic fringe. ...Twenty-three facies have been identified and grouped into three main depositional environments: outer, mid, and inner ramp. The last include barrier (shoal), lagoon, carbonate tidal-flat and shoreface sub-environments. The more prominent biogenic components show a mixture of sunlight-dependent phototrophic organisms (mainly large benthic foraminifera) and nutrient-dependent heterotrophic organisms (mainly rudists), with a remarkable rare occurrence of corals. Nutrients supplied from the emergent mainland probably promoted the development of heterozoan organisms. The vertical evolution of the ramp shows: a basal transgressive stage with facies retrogradation; a maximum flooding stage, and a regressive stage with aggradation and progradation of a distally steepened ramp. The presence and distribution of siliciclastics are problematic, since sands coming into the basin are likely to be rapidly and widely redistributed along the basin, taking into account the common storm, wave, and tidal processes preserved by the sedimentary facies. The presence of a clockwise NW-flowing longshore current is postulated to account for this distribution, which was likely induced by both dominant external currents around Iberia and wind-driven currents. These clockwise gyres facilitated the invertebrate dispersion into this enclosed basin and the local presence of upwelling. This could have been another source of episodic nutrient-rich waters from the deep ramp, which may have favored heterozoan development even in the more proximal and relatively shallower-water facies.
Lycian Nappes (in SW Turkey) lie between the Menderes Massif and Bey Dağları carbonates and comprise thrust sheets (nappes piles) of Paleozoic-Cenozoic rocks, ophiolitic and tectonic mélanges and ...serpentinized peridodites. This study focuses on identification of rudists and their palaeoenvironmental features observed within the Cretaceous low grade metamorphic successions (dominated by recrystallized limestones) from the Tavas and Bodrum nappes. The study is based on fifteen stratigraphic sections measured from Tavas, Fethiye, Köyceğiz, Bodrum, Ören and Bozburun areas. The Lower Cretaceous successions with rudists are very sparse in the Lycian Nappes and a unique locality including a Berriasian epidiceratid-requieniid assemblage is reported so far. A new requieniid-radiolitid assemblage was found within the pre-Turonian (?Albian-?Cenomanian) limestones. Four different Late Cretaceous rudist assemblages were firstly identified as well: 1) Caprinid-Ichthyosarcolitid assemblage (middle-late Cenomanian); 2) Distefanellid assemblage (late Turonian); 3) Hippuritid-Radiolitid assemblage (late Coniacian-Santonian-Campanian); 4) Radiolitid-Hippuritid assemblage (‘middle’-late Maastrichtian). Microfacies data and field observations indicate that the rudists lived in the inner and outer shelves of the Cretaceous carbonate platform(s) in this critical part of the Neotethys Ocean. Rudists formed isolated patchy aggregations in very shallow palaeoenvironments and deposited as shell fragments particularly on the outer shelf environment, which is characterized by higher energy and platform slope characteristics.
•Rudists come from the fifteen measured-stratigraphic sections of the Lycian Nappes.•Rudist associations are defined for the first time.•The identification of rudist associations allows for obtaining new stratigraphic data.•Depositional environments of rudists are presented.•All the data are compared to those of the Mediterranean Teyhys.
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