Víctor Fondevilla, Jaume Dinarès-Turell & Oriol Oms (2016)
The chronostratigraphic framework of the South-Pyrenean Maastrichtian succession reappraised: Implications for basin development and end-Cretaceous dinosaur faunal turnover.
Sedimentary Geology (advance online publication)
A new paleomagnetic study in Orcau (Isona, southern Pyrenees, Spain) is performed
The chronostratigraphy for the Maastrichtian South-Pyrenean Basin is challenged
Most of the end-Cretaceous in that area belongs to the early Maastrichtian
A significant sedimentary hiatus of about 3 My is proposed
The new temporal framework is instrumental for tectonosedimentary basin analysis
The evolution of the end-Cretaceous terrestrial ecosystems and faunas outside of North America is largely restricted to the European Archipelago. The information scattered in this last area can only be integrated in a chronostratigraphic framework on the basis of robust age constraints and stratigraphy. Therefore, we revisited the puzzling age calibration of the sedimentary infilling from the Isona sector in the Tremp syncline (South Central Pyrenees), a renowned area for its rich Maastrichtian dinosaur fossil record. Aiming to shed light to existing controversial age determinations, we carried out a new magnetostratigraphic study along the ~ 420 m long Orcau and Nerets sections of that area. Our results reveal that most of the succession correlates to the early Maastrichtian (mostly chron C31r) in accordance to ages proposed by recent planktonic foraminifera biostratigraphy. The resulting chronostratigraphic framework of the entire Maastrichtian basin recorded in the Tremp syncline shows that a significant sedimentary hiatus of about 3 My encompasses most of the late Maastrichtian in the study area. This feature, related to an abrupt migrating of the basin depocenter, is temporarily close to similar hiatuses, sedimentary rate downfalls and facies shifts recorded in other south-western European areas. The actual chronologic framework sets the basis for thorough assessment of end-Cretaceous terrestrial faunal turnover, demise and extinction patterns and more rigorous Pyrenean basin evolution analysis to be established.
Julien Benoit, Fernando Abdala, Paul R. Manger, and Bruce S. Rubidge (2016)
The sixth sense in mammalians forerunners: Variability of the parietal foramen and the evolution of the pineal eye in South African Permo-Triassic eutheriodont therapsids.
Acta Palaeontologica Polonica (in press)
doi: http: // dx.doi.org/10.4202/app.00219.2015
In some extant ectotherms, the third eye (or pineal eye) is a
photosensitive organ located in the parietal foramen on the midline of the
skull roof. The pineal eye sends information regarding exposure to sunlight to
the pineal complex, a region of the brain devoted to the regulation of body
temperature, reproductive synchrony, and biological rhythms. The parietal
foramen is absent in mammals but present in most of the closest extinct
relatives of mammals, the Therapsida. A broad ranging survey of the occurrence
and size of the parietal foramen in different South African therapsid taxa
demonstrates that through time the parietal foramen tends, in a convergent
manner, to become smaller and is absent more frequently in eutherocephalians
(Akidnognathiidae, Whaitsiidae, and Baurioidea) and nonmammaliaform
eucynodonts. Among the latter, the Probainognathia, the lineage leading to
mammaliaforms, are the only one to achieve the complete loss of the parietal
foramen. These results suggest a gradual and convergent loss of the
photoreceptive function of the pineal organ and degeneration of the third eye.
Given the role of the pineal organ to achieve fine-tuned thermoregulation in
ectotherms (i.e., “cold-blooded” vertebrates),
the gradual loss of the parietal foramen through time in the Karoo
stratigraphic succession may be correlated with the transition from a
mesothermic metabolism to a high metabolic rate (endothermy) in mammalian
ancestry. The appearance in the eye of melanopsin-containing retinal ganglion
cells replacing the photoreceptive role of the pineal eye could also have
accompanied its loss
Free pdf--in French with English abridged version
Arnaud Brignon (2016)
L’abbé Bacheley et la découverte des premiers dinosaures et crocodiliens marins dans le Jurassique des Vaches Noires (Callovien/Oxfordien, Normandie) [Abbé Bacheley and the discovery of the first dinosaurs and marine crocodilians from the Jurassic of the Vaches Noires (Callovian/Oxfordian, Normandy, France)]
Comptes Rendus Palevol (advance online publication)
Georges Cuvier published in 1808 the first scientific descriptions of dinosaur and marine crocodilian (Thalattosuchia) remains from the collection of a certain “Abbé Bachelet [sic]”, a naturalist in Rouen (Normandy, France). According to Cuvier, “Bachelet” never published any papers about the circumstances of the discovery of these fossils. Since then, there has been some doubt about their precise geographic and stratigraphic origin. This article reveals for the first time the identity of Charles Bacheley (1716–1795) and presents the biography of this pioneer in Norman palaeontology. He is the author of a note published in 1778 on the petrifactions found on the coast of Pays d’Auge (Calvados) between the Vaches Noires and Trouville-sur-Mer. This study has gone completely unnoticed and reveals that the specimens from the Bacheley collection studied by Cuvier come from the “Marnes de Dives” (Upper Callovian) or the “Marnes de Villers” (Lower Oxfordian) of the Vaches Noires cliffs. Bacheley identified these dinosaurs and marine crocodilian remains as belonging to “fishes,” which at that time also included cetaceans according to popular usage. Interestingly, Bacheley did not exclude the possibility that these petrified bones could belong to animals distinct from living forms.
Mark N. Puttick, Gavin H. Thomas and Michael J. Benton (2016)
Dating Placentalia: Morphological clocks fail to close the molecular-fossil gap.
Evolution (advance online publication)
Dating the origin of Placentalia has been a contentious issue for biologists and paleontologists. While it is likely that crown-group placentals originated in the Late Cretaceous, nearly all molecular clock estimates point to a deeper Cretaceous origin. An approach with the potential to reconcile this discrepancy could be the application of a morphological clock. This would permit the direct incorporation of fossil data in node dating, and would break long internal branches of the tree, so leading to improved estimates of node ages. Here, we use a large morphological dataset and the tip-calibration approach of MrBayes. We find that the estimated date for the origin of crown mammals is much older (~130–145 Ma) than fossil and molecular clock data (~80–90 Ma). Our results suggest that tip-calibration may result in estimated dates that are more ancient than those obtained from other sources of data. This can be partially overcome by constraining the ages of internal nodes on the tree; however, when this was applied to our dataset, the estimated dates were still substantially more ancient than expected. We recommend that results obtained using tip-calibration, and possibly morphological dating more generally, should be treated with caution.