Neuroanatomy of the crocodylomorph Portugalosuchus azenhae from the late cretaceous of Portugal

Abstract

We present the first detailed braincase anatomical description and neuroanatomical study of Portugalosuchus azenhae, from the Cenomanian (Late Cretaceous) of Portugal. This eusuchian crocodylomorph was originally described as a putative Crocodylia and one of the oldest representatives of this clade; however, its phylogenetic position remains controversial. Based on new data obtained from high resolution Computed Tomography images (by micro-CT scan), this study aims to improve the original description of this taxon and also update the scarce neuroanatomical knowledge of Eusuchia and Crocodylia from this time interval, a key period to understand the origin and evolution of these clades. The resulting three-dimensional models from the CT data allowed a detailed description of its well-preserved neurocranium and internal cavities. Therefore, it was possible to reconstruct the cavities of the olfactory region, nasopharyngeal ducts, brain, nerves, carotid arteries, blood vessels, paratympanic sinus system and inner ear, which allowed to estimate some neurosensorial capabilities. By comparison with other crocodylomorphs, these analyses showed that Portugalosuchus, back in the Cenomanian, already displayed an olfactive acuity, sight, hearing and cognitive skills within the range of that observed in other basal eusuchians and crocodylians, including extant species. In addition, and in order to test its disputed phylogenetic position, these new anatomical data, which helped to correct and complete some of the original observations, were included in one of the most recent morphologybased phylogenies. The position of Portugalosuchus differs slightly from the original publication since it is now located as a "thoracosaurid" within Gavialoidea, but still as a crocodylian. Despite all this, to better contrast these results, additional phylogenetic analyses including this new morphological character coding together with DNA data should be performed.

The neuroanatomy and pneumaticity of Hamadasuchus (Crocodylomorpha, Peirosauridae) from the Cretaceous of Morocco and its paleoecological significance for altirostral forms

“…The pneumaticity of the skull of Hamadasuchus seems to be very expanded, as in Zulmasuchus and Campinasuchus (Fonseca et al, 2020 ; Pochat‐Cottilloux et al, 2021 ). However, these structures are less expanded in extant crocodylians, allodaposuchids, Portugalosuchus , and Trilophosuchus (Bona et al, 2017 ; Puértolas‐Pascual et al, 2022 , 2023 ; Ristevski, 2022 ; Serrano‐Martínez et al, 2021 ; Serrano‐Martínez, Knoll, Narváez, Lautenschlager, & Ortega, 2019 ; Serrano‐Martínez, Knoll, Narváez, & Ortega, 2019 ; Witmer et al, 2008 ). In fossils that show adaptations to the aquatic environment, some of those structures are even absent: for example, the intertympanic diverticulum and parietal diverticulum are missing in thalattosuchians (Brusatte et al, 2016 ; Herrera et al, 2018 ; Pierce et al, 2017 ; Schwab et al, 2021 ; Wilberg et al, 2021 ).…”

“…To keep the description free of constant repetitions of references, we summarize the data on extinct and extant crocodylomorph taxa used for comparison in Table 1 . In an effort to standardize descriptive studies in paleoneuroanatomy, we follow the anatomical nomenclature published by Colbert ( 1946a , 1946b ), Kley et al ( 2010 ), Sertich and O'Connor ( 2014 ), Dufeau and Witmer ( 2015 ), Brusatte et al ( 2016 ), Bona et al ( 2017 ), Pierce et al ( 2017 ), Herrera et al ( 2018 ), Serrano‐Martínez, Knoll, Narváez, & Ortega, ( 2019 ), Serrano‐Martínez, Knoll, Narváez, Lautenschlager, & Ortega, ( 2019 ), Serrano‐Martínez et al, ( 2021 ), Leardi et al ( 2020 ), Lessner and Holliday ( 2020 ), Fonseca et al ( 2020 ), Dumont Jr et al ( 2020 ), Erb and Turner ( 2021 ), Kuzmin et al ( 2021 ), Ruebenstahl et al ( 2022 ), Schwab et al ( 2021 ), Wilberg et al ( 2021 ), Melstrom et al ( 2022 ), Pochat‐Cottilloux et al ( 2022 ), Puértolas‐Pascual et al ( 2022 , 2023 ), Ristevski ( 2022 ), Burke and Mannion ( 2023 ) and Perrichon et al ( 2023 ) concerning the endocranial structures (and references therein). Table 2 compiles several important measurements following Pierce et al ( 2017 , figure 2).…”

“…In the last decade, numerous studies using computed tomography (CT) data have been published (see Barrios et al, 2022 for a complete review) on eusuchians (Blanco et al, 2015 ; Bona et al, 2013 ; Burke & Mannion, 2023 ; Erb & Turner, 2021 ; Holliday & Gardner, 2012 ; Puértolas‐Pascual et al, 2022 , 2023 ; Serrano‐Martínez et al, 2021 ; Serrano‐Martínez, Knoll, Narváez, Lautenschlager, & Ortega, 2019 ; Serrano‐Martínez, Knoll, Narváez, & Ortega, 2019 ), thalattosuchians (Brusatte et al, 2016 ; Fernández et al, 2011 ; Herrera et al, 2018 ; Pierce et al, 2017 ; Schwab et al, 2021 ; Wilberg et al, 2021 ), early crocodylomorphs (Leardi et al, 2020 ; Melstrom et al, 2022 ; Ruebenstahl et al, 2022 ) and some notosuchians (Dumont Jr et al, 2020 ; Fonseca et al, 2020 ; Kley et al, 2010 ; Pochat‐Cottilloux et al, 2021 ; Sereno & Larsson, 2009 ). Those studies are based on extant crocodylian databases for comparison (Bona et al, 2017 ; Witmer et al, 2008 ), as well as detailed studies focusing on certain parts of the braincase (Dufeau, 2011 ; Dufeau & Witmer, 2015 ; George & Holliday, 2013 ; Hu et al, 2021 ; Jirak & Janacek, 2017 ; Klembara, 2005 ; Kuzmin et al, 2021 ; Lessner et al, 2022 ; Lessner & Holliday, 2020 ; Montefeltro et al, 2016 ; Perrichon et al, 2023 ; Porter et al, 2016 ; Schwab et al, 2021 ).…”