Penélope Cruzado-Caballero

A New Crocodylian from the Late Maastrichtian of Spain: Implications for the Initial Radiation of Crocodyloids

Background The earliest crocodylians are known primarily from the Late Cretaceous of North America and Europe. The representatives of Gavialoidea and Alligatoroidea are known in the Late Cretaceous of both continents, yet the biogeographic origins of Crocodyloidea are poorly understood. Up to now, only one representative of this clade has been known from the Late Cretaceous, the basal crocodyloid Prodiplocynodon from the Maastrichtian of North America. Methodology/Principal Findings The fossil studied is a skull collected from sandstones in the lower part of the Tremp Formation, in Chron C30n, dated at −67.6 to 65.5 Ma (late Maastrichtian), in Arén (Huesca, Spain). It is located in a continuous section that contains the K/P boundary, in which the dinosaur faunas closest to the K/P boundary in Europe have been described, including Arenysaurus ardevoli and Blasisaurus canudoi. Phylogenetic analysis places the new taxon, Arenysuchus gascabadiolorum, at the base of Crocodyloidea. Conclusions/Significance The new taxon is the oldest crocodyloid representative in Eurasia. Crocodyloidea had previously only been known from the Palaeogene onwards in this part of Laurasia. Phylogenetically, Arenysuchus gascabadiolorum is situated at the base of the first radiation of crocodyloids that occurred in the late Maastrichtian, shedding light on this part of the cladogram. The presence of basal crocodyloids at the end of the Cretaceous both in North America and Europe provides new evidence of the faunal exchange via the Thulean Land Bridge during the Maastrichtian.

Hadrosauroid Dinosaurs from the Latest Cretaceous of the Iberian Peninsula

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Vertebrate Paleontology on 2009, available online: https://doi.org/10.1671/039.029.0317

Evidencias de la coexistencia de dinosaurios hadrosaurinos y lambeosaurinos en el Maastrichtiano superior de la Península Ibérica (Arén, Huesca, España)

Abstract n Evidence of the coexistence of hadrosaurine and lambeosaurine dinosaurs in the upper Maastrichtian of the Iberian Peninsula (Arén, Huesca, Spain). Many cranial and postcranial remains of hadrosaurid ornithopods from the upper Maastrichtian have been recovered in Arén (Huesca, Spain) in the sites Blasi 1–5. Three of these cranial remains, found at Blasi 1 (Arén Formation), and Blasi 4 and 5 (Conques Formation) are jugals and are the only jugals described from Western Europe. The jugals from Arén differ from those of Telmatosaurus transsylvanicus (Nopcsa, 1900) by being these more slender and presenting an anterior process isosceles-triangle-like. The jugals found at Arén are assigned provisionally to the subfamilies Hadrosaurinae (Blasi 5) and Lambeosaurinae (Blasi 1 and 4). The hadrosaurine jugal presents an asymmetrical anterior process along the maxilla-lacrimal contact and a wide jugal neck, while the jugals of lambeosaurines have an anterior process very wide dorsoventrally and symmetric, narrow jugal neck and maxillary process perpendicular to the antero-posterior axis of the jugal. The hadrosaurine from Arén represents the first mention of the subfamily in Europe and, together with the remains of lambeosaurines found in Europe, shows an active interaction with the migratory route existing then between Asia and North America. Remains found in Arén are essential in the knowledge of the phylogenetic relationships and the biogeography of this clade in Europe.

New Material and Phylogenetic Position of Arenysaurus ardevoli, a Lambeosaurine Dinosaur from the Late Maastrichtian of Arén (Northern Spain)

ABSTRACT n Arenysaurus ardevoli is a lambeosaurine hadrosaurid from the late Maastrichtian of Arén (Huesca, northern Spain) that has recently been described. The holotype is the first and the most complete lambeosaurine with a braincase from Europe. In this paper, we present a complete description of the postcranial skeleton, which was poorly described when the taxon was named because it was partially unprepared, and new information on several cranial bones (jugal, maxilla, and dentition). A new phylogenetic analysis of Arenysaurus and the closely related Blasisaurus canudoi, also from the late Maastrichtian of Arén, places them inside the Parasaurolophini in a dichotomy with Parasaurolophus spp. Paleobiogeographically, the presence of Arenysaurus and its relationships with other lambeosaurines suggest at least one geodispersal event from Asia to Europe no later than the middle—late Campanian.

A new hadrosaurid dentary from the latest Maastrichtian of the Pyrenees (north Spain) and the high diversity of the duck-billed dinosaurs of the Ibero-Armorican Realm at the very end of the Cretaceous

In the latest Maastrichtian, the European hadrosauroid fauna was more diverse than those of North America and Asia. The European record of hadrosaurid dentaries is an example of this diversity, and most of the sites with mandibular remains are located in the Ibero-Armorican Realm. Within the Iberian Peninsula, most of the remains are located in the Tremp Basin (South Central Pyrenees). Two of the three valid hadrosaurid taxa defined in this basin are from the Blasi sites (Arén, Huesca province): Arenysaurus ardevoli (Blasi-3) and Blasisaurus canudoi (Blasi-1). A new locality in Blasi (Blasi 3.4) has provided a new dentary from an indeterminate euhadrosaurid. This dentary presents some characters intermediate between Arenysaurus and Blasisaurus, some characters similar to Pararhabdodon isonensis (from the nearby province of Lleida), and some characters of its own. Nevertheless, due to its fragmentary character, without dentition or its edentulous anterior part, it cannot be determined above the level of Euhadrosauria. It thus represents a fourth Iberian euhadrosaurian taxon in the Ibero-Armorican Realm, different from Arenysaurus, Blasisaurus and Pararhabdodon, increasing the diversity of hadrosauroids in this realm at the very end of the Cretaceous.

Paleoneuroanatomy of the European lambeosaurine dinosaur Arenysaurus ardevoli

The neuroanatomy of hadrosaurid dinosaurs is well known from North America and Asia. In Europe only a few cranial remains have been recovered that include the braincase. Arenysaurus is the first European endocast for which the paleoneuroanatomy has been studied. The resulting data have enabled us to draw ontogenetic, phylogenetic and functional inferences. Arenysaurus preserves the endocast and the inner ear. This cranial material was CT scanned, and a 3D-model was generated. The endocast morphology supports a general pattern for hadrosaurids with some characters that distinguish it to a subfamily level, such as a brain cavity that is anteroposteriorly shorter or the angle of the major axis of the cerebral hemisphere to the horizontal in lambeosaurines. Both these characters are present in the endocast of Arenysaurus. Osteological features indicate an adult ontogenetic stage, while some paleoneuroanatomical features are indicative of a subadult ontogenetic stage. It is hypothesized that the presence of puzzling mixture of characters that suggest different ontogenetic stages for this specimen may reflect some degree of dwarfism in Arenysaurus. Regarding the inner ear, its structure shows differences from the ornithopod clade with respect to the height of the semicircular canals. These differences could lead to a decrease in the compensatory movements of eyes and head, with important implications for the paleobiology and behavior of hadrosaurid taxa such as Edmontosaurus, Parasaurolophus and Arenysaurus. The endocranial morphology of European hadrosaurids sheds new light on the evolution of this group and may reflect the conditions in the archipelago where these animals lived during the Late Cretaceous.