Biodiversity on Earth is shaped by abiotic perturbations and rapid diversifications. At the same time, there are arguments that biodiversity is bounded and regulated via biotic interactions. Evaluating the role and relative strength of diversity regulation is crucial for interpreting the ongoing biodiversity changes. We have analyzed Phanerozoic fossil record using public databases and new approaches for identifying the causal dependence of origination and extinction rates on environmental variables and standing diversity. While the effect of environmental factors on origination and extinction rates is variable and taxon specific, the diversity dependence of the rates is almost universal across the studied taxa. Origination rates are dependent on instantaneous diversity levels, while extinction rates reveal delayed diversity dependence. Although precise mechanisms of diversity dependence may be complex and difficult to recover, global regulation of diversity via negative diversity dependence of lineage diversification seems to be a common feature of the biosphere, with profound consequences for understanding current biodiversity crisis.

The phylogenetic history of rudist bivalves is reviewed using a cladistic analysis based on 41 morphological shell characters and a new topology is proposed. A novel approach to rudist comparative anatomy has enabled the mapping of homologous zones. We highlight that ‘pallial canals’ can be homologous to four specific cavities that have merged during rudist evolution. The characters of the myophores and muscle insertions have also been reappraised using a hierarchical scheme. We formalize, for the first time, the complex diversification of rudist myophores by constructing tree-like characters that can contain up to six informative states for each of the four myophores. All characters have been coded as independent features. This has enabled the identification of different evolutionary rates of change between left and right valves and allows the recognition of the various morphoanatomic responses of one valve to the structural changes of the other. All characters have been coded in hierarchies and analysed in three-taxon analysis. Taxonomic sampling composed of two species per family allows an exhaustive monophyly test of all families of the suborder Hippuritidina. Only the families Polyconitidae, Plagioptychidae, Radiolitidae and Hippuritidae are found to be monophyletic. The two superfamilies are both found to be polyphyletic. The Hippuritidae is found to be the sister group of the Radiolitidae. Pachytraga is found as the sister group of all the rudists with pallial canals except Sellaea. Two evolutionary radiations in rudists are dated, using the cladistic concept of temporal hierarchy, to the Hauterivian + and the Albian+.

A bstract: The three-taxon statement is the fundamental unit of rooted trees in Cladistics, stating that for three terminal taxa, two are more related to each other than to a third. Because of their fundamental role in phylogenetics, three-taxon statements are present in methodological research of various disciplines in evolutionary biology, as in consensus methods, supertree methods, species-tree methods, distance metrics, and even phylogenetic reconstruction. However, three-taxon statements methods are subject to important flaws related to information redundancy. We aim to study the behavior of three-taxon statements and the interactions among them in order to enhance their performance in evolutionary studies. We show here how specific interactions between three-taxon statements are responsible of the emergence of redundancy and dependency within trees, and how they can be used for the improvement of weighting procedures. Our proposal is subsequently empirically tested in the supertree framework using simulations. We show that three-taxon statements using fractional weights perform drastically better than classical methods such as MRP or methods using unweighted statements. Our study shows that appropriate fractional weighting of three taxon statements is of critical importance for removing redundancy in any method using three-taxon statements, as in consensus, supertrees, distance metrics, and phylogenetic or biogeographic analyses.

Upper Barremian-lower Aptian Urgonian-type platform carbonates from Ardèche yield a rich rudist fauna belonging to the families Requieniidae, Monopleuridae, Caprinidae, and Polyconitidae. The upper Barremian assemblage from the Ardèche river gorges consists of eighteen species, it conforms to the Rustrel fauna of the Monts-de-Vaucluse but contains a new genus Valclusella, and a new species of Bicornucopina, a genus unknown so far in Western Europe, whereas Mathesia darderi is identified for the first time in SE France. We define the "Saint-Montan limestones", of early Aptian age, as the uppermost member of the Urgonian Formation in this region. The corresponding Saint-Montan fauna is described for the first time: it contains twenty-five rudist species, of which eight are new and seventeen are inherited from the antecedent late Barremian Orgon and Rustrel fossil type localities. Of the eight new species, two are ascribed to earlier genera, i.e., Homopleura parva and Bicornucopina acuminata, three are assigned to a new genus, Myostyla ardescensis, while Valclusella valclusensis and Valclusella biconvexa preexisted in the late Barremian. Aside from inherited taxa, e.g., Pachytraga paradoxa, Praecaprina varians-gaudryi, Caprina douvillei, important novelties regard the Caprinidae, characterized by the appearance of probable new species of Pachytraga, P. aff. paradoxa, Offneria, O. aff. rhodanica, and three new species of Praecaprina: Pr. tubifera n. sp., Pr. paquieri n. sp., and Pr. vacua n. sp. The early Aptian p.p., therefore, coincides with the acme of the genus Praecaprina, SE France being unique in this respect. In the Saint-Montan fauna, up to about nine species from the Rustrel fauna are missing. The Saint-Montan rudist assemblage is unique, thus far, in SE France, even as the study of its composition is still in progress. It has a West European character, similar to that of its antecedent late Barremian one, and the succeeding late early Aptian Villaroya de los Pinares fauna from Spain, but the three have distinctive taxonomic compositions. The Saint-Montan stratigraphic succession is framed by two drowning boundary events. The taxonomic composition of its rudist assemblage fills a gap between the late Barremian and the late early Aptian faunas, and represents a distinctive episode in the Barremian-lower Aptian Urgonian-type rudist sequence of southern France and Spain, and possesses a significant biostratigraphic potential.