Paleoneuroanatomy of the European lambeosaurine dinosaurArenysaurus ardevoli

Abstract

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.

Paleoneuroanatomy of the aetosaur Neoaetosauroides engaeus (Archosauria: Pseudosuchia) and its paleobiological implications among archosauriforms

“…These aetosaurs share the condition of a single exit for the CN XII with the archosauriforms Euparkeria capensis ( Sobral et al, 2016 ) and E. africanus ( Gower & Sennikov, 1996 ), phytosaurs ( E. neukami , P. angustifrons : Lautenschlager & Butler, 2016 ) pterosaurs ( Allkaruen koi : Codorniú et al, 2016 ) and theropods ( Tyrannosaurus rex : Witmer & Ridgely, 2008 ; G. carolinii : Paulina-Carabajal & Canale, 2010 ). This pattern differs from that of the archosauriform T. primus ( Stocker et al, 2016 ), crocodylomorphs ( S. icaeorhinus : Hopson, 1979 ; Simosuchus clarki : Kley et al, 2010 ; C. yacare : MACN-HE 43694; A. mississippiensis : OUVC 9761; G. gangeticus : Bona, Paulina-Carabajal & Gasparini, 2017 ), ornithischians A. ardevoli : Cruzado-Caballero et al, 2015 ; Anchiceratops ornatus: ( Hopson, 1979 ); T. plicatospineus : Paulina-Carabajal et al, 2017 ), and sauropodomorphs ( Diplodocus longus : Witmer et al, 2008 ; S. tupiniquim : Bronzati et al, 2017 ) in which the hypoglossal nerve exits through multiple foramina.…”

“…The olfactory tracts of N. engaeus (PVL 5698, PULR 108) are narrow being half the width of the cerebral hemispheres, whereas the olfactory tracts of D. spurensis (UMMP 7476; Hopson, 1979 ) are about the same width of the cerebral hemispheres as it also happens in the erpetosuchid Parringtonia gracilis ( Nesbitt et al, 2018 ). This condition of narrow olfactory tracts seen in N. engaeus resembles more that of archosauriforms ( Tropidosuchus romeri : Trotteyn & Paulina-Carabajal, 2016 ; Triopticus primus : Stocker et al, 2016 ), phytosaurs ( Ebrachosuchus neukami, Parasuchus angustifrons : Lautenschlager & Butler, 2016 ; Wannia scurriensis : Lessner & Stocker, 2017 , ornithosuchids ( Riojasuchus tenuisceps : Baczko, Taborda & Desojo, 2012 ), and crocodylomorphs ( Sebecus icaeorhinus : Hopson, 1979 ; Simosuchus clarki : Kley et al, 2010 ; Caiman yacare, Alligator mississippiensis, and Gavialis gangeticus : Bona, Paulina-Carabajal & Gasparini, 2017 ), theropods ( Giganotosaurus carolinii : Paulina-Carabajal & Canale, 2010 ; Sinraptor dongi : Paulina-Carabajal & Currie, 2012 ), ornithischians (e.g., Corythosaurus sp., Hypacrosaurus altispinus : Evans, Ridgely & Witmer, 2009 ; Arenysaurus ardevoli : Cruzado-Caballero et al, 2015 ; Euoplocephalus tutus : Miyashita et al, 2011 ; Pachycephalosaurus wyomingensis : Giffin, 1989 , Stegoceras validum : Stocker et al, 2016 ), and sauropods ( Amargasaurus cazaui : Paulina-Carabajal, Carballido & Currie, 2014 ; Diplodocus longus : Witmer & Ridgely, 2008 ).…”

Morphological innovation and the evolution of hadrosaurid dinosaurs

“…6). Tethyshadros and Arenysaurus are smaller-bodied species and have been identified as insular dwarfs (Dalla Vecchia 2009; Cruzado-Caballero et al 2015). Shantungosaurus is a gigantic saurolophine (body mass estimated at 17,400 kg), and one of the largest ornithischians known (Benson et al 2018).…”

First nearly complete skull of Gallotia auaritae (lower-middle Pleistocene, Squamata, Gallotiinae) and a morphological phylogenetic analysis of the genus Gallotia

“…33 ) and to deep in the neuroanatomy of the fossil specimen (in similar manner to Cruzado-Caballero et al . 34 ). Images of the 3D surface in Figs 1–6 were acquired via the screenshot option in Avizo 7.0.…”