Zverkov NG, Fischer V, Madzia D & Benson RBJB. 2018 Increased pliosaurid dental disparity across the Jurassic–Cretaceous transition. Palaeontology doi: 10.1111/pala.12367.
Pliosaurid marine reptiles played important roles in marine food chains from the Middle Jurassic to the ‘middle’ Cretaceous, frequently as apex predators. The evolution of pliosaurids during the later parts of the Early Cretaceous has recently been illuminated by discoveries from Russia (Hauterivian) and Colombia (Barremian). However, knowledge of pliosaurids representing the Jurassic–Cretaceous transition (late Tithonian–Valanginian), is still largely incomplete, especially during the earliest Cretaceous. As such, the effect on pliosaurids of hypothesized faunal turnover during the Jurassic–Cretaceous boundary interval is poorly understood. We report pliosaurid teeth from theupper Volgian (Tithonian, Upper Jurassic) of the Kheta river basin (Eastern Siberia, Russia), to the Berriasian and Valanginian (Lower Cretaceous) of the Volga region (European Russia). These assemblages yielded a series of distinct tooth morphotypes, including the first reports of conical-toothed pliosaurids from the latest Jurassic–earliest Cretaceous.This challenges the hypothesis that only one lineage of pliosaurids crossed the Jurassic–Cretaceous boundary. It appears that conical-toothed pliosaurids co-existed with their trihedral-toothed relatives for at least 25 million years during the latest Jurassic and earliest Cretaceous. In fact, our quantitative analyses indicate that pliosaurids reached their maximal dental disparity during this interval, showing little evidence of turnover associated with the Jurassic–Cretaceous transition. Instead, disparity decreased later in the Early Cretaceous, with the disappearance of trihedral-toothed forms in the Barremian.
The very first paper of Isaure!
Rhinochelys amaberti Moret (1935), a protostegid turtle from the Early Cretaceous of France
Scavezzoni I & Fischer V. PeerJ 6:e4594; DOI 10.7717/peerj.4594 Freely available here
Modern marine turtles (chelonioids) are the remnants of an ancient radiation that roots in the Cretaceous. The oldest members of that radiation are first recorded from the Early Cretaceous and a series of species are known from the Albian- Cenomanian interval, many of which have been allocated to the widespread but poorly defined genus Rhinochelys, possibly concealing the diversity and the evolution of early marine turtles. In order to better understand the radiation of chelonioids, we redescribe the holotype and assess the taxonomy of Rhinochelys amaberti Moret (1935)(UJF-ID.11167) from the Late Albian (Stoliczkaia dispar Zone) of the Vallon de la Fauge (Isère, France). We also make preliminary assessments of the phylogenetic relationships of Chelonioidea using two updated datasets that widely sample Cretaceous taxa, especially Rhinochelys. Rhinochelys amaberti is a valid taxon that is supported by eight autapomorphies; an emended diagnosisis proposed. Our phylogenetic analyses suggest that Rhinochelys could be polyphyletic, but constraining it as a monophyletic entity does not produce trees that are significantly less parsimonious. Moreover, support values and stratigraphic congruence indexes are fairly low for the recovered typologies, suggesting that missing data still strongly affect our understanding of the Cretaceous diversification of sea turtles.
Isaure's drawing on Rhinochelys amaberti
The evolutionary history of polycotylid plesiosaurians
Fischer V., Benson R.B.J., Druckenmiller P.S., Ketchum H.F.& Bardet N.
VF and RBJB are co-first authors
Royal Society Open Science 5: 172177. http://dx.doi.org/10.1098/rsos.172177. Freely available here
Polycotylidae is a clade of plesiosaurians that appeared during the Early Cretaceous and became speciose and abundant early in the Late Cretaceous. However, this radiation is poorly understood. Thililua longicollisfrom the Middle Turonian of Morocco is an enigmatic taxon possessing an atypically long-neck and, as originally reported, a series of unusual cranial features that cause unstable phylogenetic relationships for polycotylids. We reinterpret the holotype specimen of Thililua longicollisand clarify its cranial anatomy. Thililua longicollispossesses an extensive, foramina-bearing jugal, a premaxilla-parietal contact, and carinated teeth. Phylogenetic analyses of a new cladistic dataset based on first hand observation of most polycotylids, recovers Thililua and Mauriciosaurusas successive lineages at the base of the earliest Late Cretaceous polycotyline radiation. A new dataset summarizing the Bauplan of polycotylids reveal that their radiation produced an early burst of disparity during the Cenomanian-Turonian interval, with marked plasticity in relative neck length, but this did not arise as an ecological release following the extinction of ichthyosaurs and pliosaurids. This disparity vanished during and after the Turonian, which is consistent with a model of ‘early experimentation/late constraint’. Two polycotylid clades, Occultonectia clade nov. and Polycotylinae, survived up to the Maastrichtian, but with low diversity.
Our interpretation of the skull of Thililua longicollis, an early Late Cretaceous polycotylid from Morocco
Our Ph.D. student Ulysse just published by French and Belgian colleagues a new rhabdodontid dinosaur with shearing dentition. The new critter is called Matheronodon provincialis. Link to the press release text by The Royal Belgian Institute of Natural Sciences.
Here the abstract of the paper:
Godefroit, Garcia, Gomez, Stein, Cincotta, Lefèvre & Valentin. 2017. Extreme tooth enlargement in a new Late Cretaceous rhabdodontid dinosaur from Southern France. Scientific Reports 7: 13098. doi:10.1038/s41598-017-13160-2
Rhabdodontidae is a successful clade of ornithopod dinosaurs, characteristic of Late Cretaceous continental faunas in Europe. A new rhabdodontid from the late Campanian, of southern France, Matheronodon provincialis gen. et sp. nov., is characterized by the extreme enlargement of both its maxillary and dentary teeth, correlated to a drastic reduction in the number of maxillary teeth (4 per generation in MMS/VBN-02-102). The interalveolar septa on the maxilla are alternately present or resorbed ventrally so as to be able to lodge such enlarged teeth. The rhabdodontid dentition and masticatory apparatus were adapted for producing a strict and powerful shearing action, resembling a pair of scissors. With their relatively simple dentition, contrasting with the sophisticated dental batteries in contemporary hadrosaurids, Matheronodon and other rhabdodontids are tentatively interpreted as specialized consumers of tough plant parts rich in sclerenchyma bers, such as Sabalites and Pandanites.
The "Teaching" section has been updated. Check there regularly to get the slides, syllabus, and data for practicals!
We have been modifying our "Publications" section, adding several links to open access versions of our papers as well as links to freely accessible datasets and supplementary information. Check it out!
Interview de Jean-Marc Marion concernant la nouvelle carte géologique de Malmedy qu'il a réalisé, contenant, peut-être, les plus anciennes roches affleurant en Belgique!
We have a new paper just published in Current Biology, dealing with a new pliosaur from the Late Hauterivian of Russia, Luskhan itilensis, and analyzing the ecomorphological convergences among short-necked plesiosaurs.
Quite an important press coverage (see icon below) and some videos interviews as well: www.rtl.be/info/Video/629641.aspx www.rtc.be/video/info/edition-du-26-05-2017_1495279_307.html
Fischer V, Benson RBJ, Zverkov NG, Soul LC, Arkhangelsky MS, Lambert O, Stenshin IM, Uspensky GN, Druckenmiller PS. 2017. Plasticity and convergence in the evolution of short-necked plesiosaurs. Current Biology 27 doi:10.1016/j.cub.2017.04.052.
Plesiosaurs were the longest-surviving group of secondarily marine tetrapods, comparable in diversity to today’s cetaceans. During their long evolutionary history, which spanned the Jurassic and the Cretaceous (201 to 66 Ma), plesiosaurs repeatedly evolved long- and short-necked body plans. Despite this postcranial plasticity, short-necked plesiosaur clades have traditionally been regarded as being highly constrained to persistent and clearly distinct ecological niches: advanced members of Pliosauridae (ranging from the Middle Jurassic to the early Late Cretaceous) have been characterised as apex predators, whereas members of the distantly related clade Polycotylidae (middle–Late Cretaceous) were thought to have been fast-swimming piscivores. We report a new, highly unusual pliosaurid from the Early Cretaceous of Russia that shows close convergence with the cranial structure of polycotylids: Luskhan itilensis gen. et sp. nov. Using novel cladistic and ecomorphological data, we show that pliosaurids iteratively evolved polycotylid-like cranial morphologies from the Early Jurassic until the Early Cretaceous. This underscores the ecological diversity of derived pliosaurids and reveals a more complex evolutionary history than their iconic representation as gigantic apex predators of Mesozoic marine ecosystems suggests. Collectively, these data demonstrate an even higher degree of morphological plasticity and convergence in the evolution of plesiosaurs than previously thought, and suggest the existence of an optimal ecomorphology for short-necked piscivorous plesiosaurs through time and across phylogeny.
Fischer 2016. Taxonomy of Platypterygius campylodon and the diversity of the last ichthyosaurs. PeerJ 4:e2604; DOI 10.7717/peerj.2604. Freely available here: peerj.com/articles/2604/?td=bl
A complex and confusing taxonomy has concealed the diversity dynamics of Cretaceous ichthyosaurs (Reptilia) for decades. The near totality of Albian-Cenomanian remains from Eurasia has been assigned, by default, to the loosely defined entity Platypterygius campylodon, whose holotype was supposed to be lost. By thoroughly examining the Cenomanian ichthyosaur collections from the UK, I redescribe the syntypic series of Platypterygius campylodon. This material, along with a handful of other coeval remains, is diagnostic and seemingly differs from the vast majority of Cretaceous remains previously assigned to this taxon. A lectotype for Platypterygius campylodon is designated and I reassign this species to Pervushovisaurus campylodon nov. comb. The feeding ecology of this species is assessed and conforms to the scenario of an early Cenomanian diversity drop prior to the latest Cenomanian final extinction.
Figure 3 Rostra referred to Pervushovisaurus campylodon (Carter, 1846a). (AD) CAMSM TN282, a partial rostrum possibly from a juvenile specimen. (A) Ventrolateral view. (BC) Details of the teeth. (D) Detail of the premaxillary overbite. (EF) CAMSM B20671a, a partial rostrum of a large specimen. (E) Lateral view. (F) detail of the mid-snout teeth. (G) Detail of the premaxillary overbite. Fischer 2016 PeerJ
Our former PhD student Sébastien Olive just published novel tetrapod remains from the Famenian of Belgium! The publication Olive & al 2016 Palaeontology can be accessed here!