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New material of Alierasaurus ronchii (Synapsida, Caseidae) from the Permian of Sardinia (Italy), and its phylogenetic affinities

Marco Romano, Ausonio Ronchi, Simone Maganuco, and Umberto Nicosia

Plain Language Abstract

Caseids constitute a crucial group of basal synapsids, among the first vertebrates to fully exploit herbivory. Remains of caseids in Europe are very few and historically rare, with Alierasaurus ronchii from the Permian of Sardinia, representing the only non-therapsid synpasids found to date in Italy. The new discovered diagnostic material allowed for the first time to understand the possible evolutionary position of the Sardinian caseid within the phylogenetic tree of the family, throwing further light on the general evolution of Caseasauria. In addition, the very large size of the material suggests that Alierasaurus might actually be the largest caseid, larger than the giant North American taxon Cotylorhynchus hancocki, as well as one of the biggest non-therapsid synapsids so far known. Such a giant body size must have been selected during evolution of caseids, leading to advantages in terms of fitness, and is probably closely related to their herbivorous lifestyle.

Resumen en Español

Nuevo material de Alierasaurus ronchii (Synapsida, Caseidae) del Pérmico de Cerdeña (Italia), y sus afinidades filogenéticas

Se describen aquí nuevos caracteres del Caseidae gigante Alierasaurus ronchii basados en el material recuperado de la localidad tipo en los depósitos del Pérmico de la Formación Cala del Vino (Cerdeña NW) y la preparación adicional del material previamente obtenido. Todos los nuevos elementos osteológicos descritos se caracterizan por el mismo estado de conservación y, dada la ausencia de elementos dobles y la compatibilidad total en tamaño absoluto, el nuevo material puede atribuirse sin duda al individuo holotipo de A. ronchii. El material altamente diagnóstico incluye una espina neural caudal con una terminación distal bífida amplia. Esto representa una sinapomorfía que caracteriza a los Caseidae más derivados, confirmando así plenamente la atribución del espécimen de Cerdeña a esta familia. También el otro material vertebral y las costillas recientemente obtenidas del yacimiento muestran una estructura típica de Caseidae, lo cual es completamente consistente con el material previamente publicado. A pesar de la naturaleza incompleta de Alierasaurus, el taxón se incluyó en un reciente análisis filogenético de los Caseidae para investigar su posición filogenética dentro del grupo monofilético Caseasauria. Alierasaurus se muestra como el taxón hermano de Cotylorhynchus, y es autapomórfico en la construcción general de MT-IV y la falange proximal IV-I. El tamaño absoluto del material recientemente recuperado confirma un tamaño corporal gigantesco para Alierasaurus, comparable, si no es mayor, al de la especie norteamericana Cotylorhynchus hancocki (de hasta 6 m de longitud). Tal tamaño de cuerpo gigantesco para el adulto, estrechamente relacionado con su estilo de vida herbívoro, debe haber estado bajo presión de selección durante la evolución de los Caseidae, dando lugar a importantes ventajas en términos de eficiencia.

Palabras clave: Sinápsidos no-terápsidos; Caseasauria; Caseidae; Pérmico; Italia; Filogenia

Traducción: Enrique Peñalver (Sociedad Española de Paleontología)

Résumé en Français

text

Translator: Antoine Souron

Deutsche Zusammenfassung

Neues Material von Alierasaurus ronchii (Synapsida, Caseidae) aus dem Perm von Sardinien (Italien) und die phylogenetischen Beziehungen

Es werden neue Merkmale des großen caseiden Alierasaurus ronchii beschrieben, basierend auf Material aus der Typlokalität in den permischen Ablagerungen der Cala del Vino Formation (Nordwestsardinien) und auf neu präpariertes Material der zuvor gesammelten Stücke. Alle neuen osteologischen Elemente haben den gleichen Präparationszustand und da keine doppelten Elemente vorkommen und durch die vollständige Komptabilität der absoluten Größe, kann das neue Material ohne Zweifel dem Holotyp-Individuum von A. ronchii zugeschrieben werden. Caudale Neuralbögen mit einem breiten zweigeteilten Ende gehören zum hochdiagnostischen Material. Dies stellt eine Synapomorphie der höher abgeleiteten Caseiden dar und bestätigt so die Zuordnung des Sardinien-Fundstücks zu den Caseiden. Auch die anderen Wirbel und die neu gesammelten Rippen zeigen die typische Caseiden-Struktur und stimmen vollständig mit dem vorher beschriebenen Material überein. Trotz seiner Unvollständigkeit wurde Alierasaurus kürzlich in einer Studie über Caseiden und seine phylogenetische Position innerhalb der monophyletischen Caseasauria platziert. Alierasaurus wird als Schwestertaxon von Cotylorhynchus angesehen und weist Autaopmorphien bei der allgemeinen Konstruktion von MT-IV und den proximalen Phalangen IV-I auf. Die absolute Größe des neu gefundenen Materials bestätigt eine enorme Körpergröße für Alierasaurus, vergleichbar mit der großen nordamerikanischen Art Cotylorhynchus hancocki (bis zu 6 m Länge), wenn nicht sogar größer. Eine derartige Körpergröße, die eng mit der herbivoren Lebensweise zusammenhängt, muss während der Caseiden-Evolution entstanden sein und zu wesentlichen Vorteilen in Bezug auf die Fitness geführt haben.

Schlüsselwörter: nicht-therapside Synapsiden; Caseasauria; Caseidae; Perm; Italien; Phylogenie

Translator: Eva Gebauer

Arabic

in progress

Translator: Ashraf M.T. Elewa

 

 

FIGURE 1. Discovery location and stratigraphic position of Alierasaurus ronchii in the frame of the Permian and Triassic succession of Nurra (NW Sardinia, Italy).

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FIGURE 2. New recovered vertebral material of Alierasaurus ronchii in lateral (1, 2, 5-8, 9, 10, 15, 16, 21, 22, 27, 28), anterior and posterior (3, 4, 11, 12, 17, 18, 23, 24, 29, 30), dorsal (13, 19, 25, 31), and ventral (14, 20 26) views. NS151/10 (1-4); NS151/12 (5-6); NS151/11 (7-8); NS151/7 (9-14); NS151/8 (15-20); NS151/9 (21-26); NS151/33 (27-31). Scale bar equal to 5 cm.

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FIGURE 3. New prepared and recovered pre- and postzygapophyses of Alierasaurus ronchii in lateral (1, 4, 5, 6, 9, 10, 13, 14, 17, 18, 20), medial (2, 7), posterior (11, 15, 19, 21), dorsal (3, 8, 12) and ventral (16) views. NS151/16a-b (1-3); NS151/17 (4-5); NS151/30 (6-8); NS151/15 (9-12); NS151/16 (13-16); NS151/19 (17-19); NS151/29 (20-21). Scale bar equal to 5 cm.

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FIGURE 4. Neural spines and proximal portions of haemal arches of Alierasaurus ronchii in lateral (1, 2, 7, 11, 12, 15, 16), dorsal (5, 9, 13, 17), ventral (6, 14), anterior/posterior (3, 4, 8, 10) views. NS151/74 (1-5); NS151/48 (6-10); NS151/59 (11-14); NS151/72 (15-17). Scale bar equal to 5 cm.

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FIGURE 5. Fragmentary recovered ribs of Alierasaurus ronchii in anterior (1, 3, 5, 7, 9) and posterior (2, 4, 6, 8, 10) views. NS151/39 (1-2); NS151/40 (3-4); NS151/42 (5-6); NS151/54 (7-8); NS151/55 (9-10). Scale bar equal to 5 cm.

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FIGURE 6. Mostly complete dorsal rib NS151/75 of Alierasaurus ronchii. Anterior view (1); posterior view (2). Scale bar equal to 5 cm.

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FIGURE 7. Largest dorsal rib found to date for Alierasaurus ronchii (NS151/76). Anterior view (1); posterior view (2). Scale bar equal to 5 cm.

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FIGURE 8. Photogrammetric models of the dorsal rib of Alierasaurus ronchii (NS151/76) lying in anterior view in its original position. Meshed models in greyscale (1, 3, 5); Realistic model with textures provided by the original pictures (2, 4, 6).

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FIGURE 9. Topology obtained including Alierasaurus in a new cladistics analysis of Caseidae. Obtained cladogram showing the Bremer support (1); Result of the bootstrap analysis (2); Result of the jackknife analysis (3). Caseasauria reported in blue.

figure9 

FIGURE 10. Cladograms obtained by including the basal caseid Eocasea martini (in green) in the cladistic analysis. Strict reduced consensus of three equally parsimonious trees with basal Caseasauria (in blue) not resolved (1); E. martini falling more basal then Eothyris could be external to Caseidae (2); E. martini as sister taxon of Eothyris, thus representing an eothyridid (3); E. martini represents the most basal caseid as suggested by Reisz and Fröbisch (2014) (4).

figure10 

FIGURE 11. In vivo reconstruction of Alierasaurus ronchii by the Italian artist Emiliano Troco (oil on canvas). The reconstruction has been obtained taking as reference for comparison the mounted skeletons of Cotylorhynchus romeri OMNH 655, OMNH 1673 and the cast on slab MSNM V7161.

figure11

 

 

author1Marco Romano. Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, Berlin, Germany; Dipartimento di Scienze della Terra, “Sapienza” Universita` di Roma, P.le A. Moro 5, 00185 Rome, Italy. This email address is being protected from spambots. You need JavaScript enabled to view it.

Marco Romano received his PhD in Earth Science (vertebrate paleontology) from the Sapienza, University of Rome Italy, working on the phylogeny of basal synapsids (Family Caseidae, Casesauria, Synapsida). From 2012 he is Research Associate in Vertebrate Paleontology at the Sam Noble Museum (Norman, Oklahoma). From 2015 is a post-doc researcher in vertebrate paleontology in the framework of the Sofja Kovalevskaja-Project "Early Evolution and Diversification of Synapsida" of the German Federal Ministry of Education and Research from the Alexander von Humboldt-Foundation at the Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung. He has a very broad research interest in evolutionary biology and vertebrate paleontology, combining several modern and quantitative approaches (osteology, functional morphology, morphometry, ichnology, biomechanics, ethology, myology, "in vivo" restoration and body mass estimate) in order to obtain a better, and as much as possible multidisciplinary and holistic knowledge of some key points in the evolution of terrestrial tetrapods. He also conduct research in philosophy and history of science (especially in the early development of paleontology and geology) analyzing the onset, and evolution in time, of fundamental concepts for Earth Sciences. In this framework is an active member of the "Geoitaliani Project", a section of the Italian Geological Society whose mission is to analyze and disseminate the great contribution of Italian scientists to the early advancement of knowledge in geology and paleontology.

https://www.researchgate.net/profile/Marco_Romano4

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author2Ausonio Ronchi. Dipartimento di Scienze della Terra, Università di Pavia, v. Ferrata 1, 27100 Pavia, Italy. This email address is being protected from spambots. You need JavaScript enabled to view it.

Ausonio Ronchi works as associate professor in Stratigraphy at the Dipartimento di Scienze della Terra e dell'Ambiente, Università di Pavia. He graduated at the Università degli Studi di Milano and obtained his Ph.D. c/o Università degli Studi di Parma; Thesis title: "Stratigraphy and basin reconstruction of the Escalaplano and Perdasdefogu Permian basins, SE Sardinia, Italy". His primary research interests lie in the areas of stratigraphy and siliciclastic sedimentology, facies and basin analysis onto the Permo-Carboniferous to Early Triassic continental sequences of Sardinia, the Southern Alps, Bulgaria, Southern France, Spain and Cretaceous to Pleistocene of Patagonia Argentina (Neuquén Basin). Terrestrial biostratigraphy and palaeogeographic reconstructions are also among his fields of interest.
During the years he analyzed different intramontane basins with fluvial-alluvial depositional facies. From a detailed analysis of the single succession he moved to an interregional correlation between areas currently separated, aiming at the reconstruction of the paleogeography at the W Mediterranean sector scale up to inner Europe areas in the late Paleozoic to early Mesozoic interval.
He is Voting Member in the IUGS Subcommission on Permian Stratigraphy (SPS) and is author or co-author of several peer-reviewed papers or contributions in volumes, geological maps, guide-books. https://www.researchgate.net/profile/Ausonio_Ronchi

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author3Simone Maganuco. Museo di Storia Naturale di Milano, Corso Venezia 55, 20121 Milano, Italy. This email address is being protected from spambots. You need JavaScript enabled to view it.

Simone Maganuco is a vertebrate paleontologist who has collaborated with the Museo di Storia Naturale di Milano (Italy) since 2003. He has studied fossils of several Mesozoic vertebrates from Madagascar and Africa, including stereospondyl amphibians and the enigmatic giant predator Spinosaurus, as well as the Italian baby dinosaur Scipionyx. As a collaborator with GeoModel and member of "Prehistoric Minds", Maganuco designs and supervises the making of hyper-realistic models of dinosaurs and prehistoric animals, as well as temporary and permanent exhibitions. He is the creator and curator of the travelling exhibition "Dinosauri in Carne e Ossa / Dinosaurs in the Flesh".


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author4Umberto Nicosia. Dipartimento di Scienze della Terra, “Sapienza” Universita` di Roma, P.le A. Moro 5, 00185 Rome, Italy. This email address is being protected from spambots. You need JavaScript enabled to view it.

Umberto Nicosia works as professor of Paleontology at the Department of Earth Sciences and he was the Director of the Paleontological Museum of the Sapienza Università di Roma and of the Earth Sciences Department. His scientific activity covers several fields of Mesozoic geology and paleontology. Since 1975 he has been studying Jurassic successions in Italy, Albania, Turkey, England, Germany and France. Its main research field concerns systematics and palaeobiogeography of dinosaurs and of Paleozoic and Mesozoic tetrapod footprints. He is also especially interested in evolution of articulate crinoids. The number of his publications in these topics exceeds 70. 

 

APPENDIX 1.

Composition of bony tubercles

After a careful analysis all the tubercles result made of bone and are not constituted by metallic incrustations. As first element, it is possible to check the histological section of a rib of Alierasaurus, presented and described by Lambertz et al. (2016, figure 5, p. 11); in the section also the raised portions, forming the typical tubercles, are entirely made of bony cortex.

To be sure, a phalanx and a rib rich in surface tubercles have been scanned at micro CT-scan. The specimens were scanned at the Museum für Naturkunde Berlin using x-ray computed tomography (phoenix|x-ray nanotom s) at 110kV, 190µA for 1400 / 360° projections / segment of the multiscan, and an exposition timing of 750 ms / projection. The specimen was scanned at a magnification ratio of x 1.54100859, and an effective voxel size of 0.03244628 mm as well as an additional calibration value of 1.313.

The smaller rib fragment was scanned using x-ray computed tomography at 120kV, 200µA for 1400 / 360° projections / segment of the multiscan, and an exposition timing of 750 ms / projection. The specimen was scanned at the same settings for magnification and effective voxel size, with an additional calibration value of 0.795. No filter was used. Cone beam reconstruction for all specimenswas performed using datos|x-reconstruction software (GE Sensing & Inspection Technologies GmbH phoenix|x-ray) The volume was reconstructed out of 1400 saved 16bit - tagged image files (TIF) for each scan.

With this method, metal crusts are clearly identifiable, being represented by a shiny silver patina. As shown in Appendix 1.1 some tubercles (in the bottom right of the phalanx) have a thin metal coating that superficially covers the raised structure. However, the tubercle is composed entirely of bone, without any contrast or composition change compared with the rest of the phalanx (and of the rib). In addition, in Appendix 1.2 is shown how the bones are characterized by transverse fractures, where a metallic coating is precipitated during diagenesis. Even at the macroscopic level, in two broken tubercles of the same phalanx the cortex bony tissue is very well visible.

APPENDIX 1.1. Micro CT-scan of Alierasaurus phalanx (in the right foreground) and rib (background on the left). Silver color indicates the thin metal plates.

appendix1

APPENDIX 1.2. Micro CT-scan of Alierasaurus phalanx (on the left) and rib (on the right); gray-light portions indicating the transverse fractures with a diagenetic metallic coating.

 

appendix2

APPENDIX 2.

New morphometric characters considered in the analysis including Alierasaurus ronchii

Specimens directly analyzed: Alierasaurus ronchii (MPUR NS 151), Casea broilii (FMNH UC 656), ‘Casea’ nicholsi (FMNH UR 86), Cotylorhynchus bransoni (FMNH UR 988), Cotylorhynchus romeri (OMNH 605).

Specimens taken from literature: Angelosaurus dolani (Olson, 1968, p. 262, fig. 18), Captorhinus aguti (Holmes, 2003, p. 520, fig. 7), Diadectes (Berman and Henrici, 2003, p. 178, fig. 3), Dimetrodon milleri (Reisz, 1986, p. 55, fig. 33), Ennatosaurus tecton (Olson, 1968, p. 262, fig. 18), Euromycter rutenus (Sigogneau-Russell and Russell, 1974, p. 189, fig. 18), Ophiacodon retroversus (Reisz, 1986, p. 55, fig. 33) Sphenacodon ferox (Henrici et al., 2005, p. 108, fig. 2), Varanops brevirostris (Reisz, 1986, p. 55, fig. 33), Limnoscelis paludis (Williston, 1911, p.43, fig. 16),

In the case of Euromycter rutenus the foot is not preserved in the holotype, then the hand was used for the construction of ratios. This under the assumption that there are no major differences in metapodials and proximal phalanges between front and hind autopods in non-therapsid synapsids.

Character 478: Ratio MT-IV proximal width/MT-IV distal width

append478

Character 479: Ratio phalanx IV-I proximal width/MT-IV proximal width

append479

Character 480: Ratio MT-shaft narrowing/MT-IV proximal width

append480

Character 481: Ratio phalanx IV-I total length/MT-IV total length

append481

Character 482: Ratio MT-shaft narrowing/phalanx IV-I proximal width

append482

 

APPENDIX 3.

Matrix including Alierasaurus ronchii. See for zipped file holding NEX file.

APPENDIX 4.

Matrix including Alierasaurus ronchii and Eocasea martiniSee for zipped file holding NEX file.