PALEOBIOLOGY and INTERRELATIONSHIPS of PERMIAN–TRIASSIC ACTINOPTERYGIANS Dissertation Zur Erlangung Der Naturwissenschaftliche
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Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2018 Paleobiology and Interrelationships of Permian-Triassic actinopterygians Argyriou, Thodoris Abstract: Dissertation zur Erlangung der naturwissenschaftlichen Doktorwürde (Dr. sc. nat.) vorgelegt der Mathematisch-naturwissenschaftlichen Fakultät der Universität Zürich von Thodoris Argyriou aus Griechenland Promotionskommission Prof. Dr. Marcelo R. Sánchez-Villagra (Vorsitz und Leitung der Dissertation) PD Dr. Torsten Scheyer Prof. Dr. Marcus Clauss Prof. Dr. Olga Otero Zürich, 2018 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-169660 Dissertation Published Version Originally published at: Argyriou, Thodoris. Paleobiology and Interrelationships of Permian-Triassic actinopterygians. 2018, University of Zurich, Faculty of Science. PALEOBIOLOGY AND INTERRELATIONSHIPS OF PERMIAN–TRIASSIC ACTINOPTERYGIANS Dissertation zur Erlangung der naturwissenschaftlichen Doktorwürde (Dr. sc. nat.) vorgelegt der Mathematisch-naturwissenschaftlichen Fakultät der Universität Zürich von Thodoris Argyriou aus Griechenland Promotionskommission Prof. Dr. Marcelo R. Sánchez-Villagra (Vorsitz und Leitung der Dissertation) PD Dr. Torsten Scheyer Prof. Dr. Marcus Clauss Prof. Dr. Olga Otero Zürich, 2018 “There’s no easy way out, there’s no shortcut home...” Robert Tepper, 1985 ABSTRACT .....................................................................................................................................................2 ZUSAMMENFASSUNG .......................................................................................................................................4 CONTRIBUTION OF EACH COLLABORATOR ........................................................................................................6 INTRODUCTION ...............................................................................................................................................7 CHAPTER I Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes .........................................................................................21 CHAPTER II Re-evaluation of the ontogeny and reproductive biology of the Triassic fishSaurichthys (Actinopterygii, Saurichthyidae) .................................................................................41 CHAPTER III Internal cranial anatomy of Early Triassic species of †Saurichthys (Actinopterygii: †Saurichthyiformes): implications for the phylogenetic placement of †saurichthyiforms........................................................................................................59 CHAPTER IV The endoskeleton of †Brachydegma caelatum (Cisuralian) implies earlier evolution of the sophisticated neopterygian jaw suspension ....................................169 CONCLUSIONS AND FUTURE DIRECTIONS ......................................................................................................217 APPENDIX Appendix A A new early Miocene (Aquitanian) Elasmobranchii assemblege from the La Guajira Peninsula, Colombia .................................................................................................223 Appendix B The oldest record of gnathostome fossils from Greece: Chondrichthyes from the Lopingian of Hydra Island ........................................................................................249 ACKNOWLEDGEMENTS ................................................................................................................................259 CURRICULUM VITAE ..................................................................................................................................260 Abstract Actinopterygians (ray-finned fishes) were not as severely affected by the ‘End Permian Mass Extinction’ event as were many groups of marine organisms, and diversified subsequently during the Triassic, establishing themselves as the most successful and species-rich clade of vertebrate animals. Despite a growing number of taxonomic works for Permian–Triassic forms, their paleobiology and interrelationships remain poorly understood. This Ph.D. thesis is aimed at documenting and analyzing novel anatomical information from exceptionally preserved actinopterygians from this time interval, in order to paint a more vivid picture of the biology of these long extinct animals, while tying them to a broader evolutionary context. Many of the contained works focus on the latest Permian–Middle Jurassic †saurichthyiforms. Their salient representative, †Saurichthys, is a particularly important component of many early Mesozoic assemblages across the globe, and its rich fossil record helps establish it as an important model for comparison between fossil and recent ray-fins. Exceptionally preserved fossils from the Middle Triassic of Switzerland preserve casts of the gastrointestinal tract (GIT) ofSaurichthys † , fossilized in situ. These faithfully depict the surrounding soft tissues, allowing for a deep-time perspective into the evolution of the GIT of fishes. The GIT ofSaurichthys † shows differences from that of extant actinopterygians. The most conspicuous one lies in the well-developed spiral intestine, the high turn count of which resembles that of some modern sharks. Anatomical comparisons and a phylogenetically informed statistical analysis of the distribution of spiral valve turn counts across fishes were performed. The high number of turns in the gutSaurichthys of † and some recent chondrichthyans reflect both energetically demanding lifestyles and the evolutionary histories of these groups. Middle Triassic deposits from Switzerland have produced almost complete ontogenetic series of two viviparous species of †Saurichthys, ranging from embryos to juveniles and adults. The study of these fossils adds to our understanding of the reproductive biology and early life history of those fishes. Topological criteria are established to distinguish embryos from cannibalized prey. Small juveniles exhibit well-formed crania and dentitions, suggesting they were born capable of exogenous feeding. However, a series of osteological criteria, such as the delayed ossifications of the parietals, the presence of open sensory grooves on the dermatocranium , and the delayed formation of the mid-lateral scale row, allow for distinguishing juveniles from adults. Viviparity and internal fertilization appear as specializations of Middle Triassic †Saurichthys. Despite previous works, the phylogenetic position of †saurichthyiforms remained contested, and needed to be revisited in light of new data. An µCT investigation of some of the earliest representatives of the clade, preserved in three dimensions, resulted in the discovery of several anatomical features. These were either undetected or misidentified by previous workers. Key amongst them is the presence of nasobasal canals in the rostrum, a fused dermohyal on the hyomandibula, and the reconsideration of the homology of the opercular series of †saurichthyiforms. New anatomical information was incorporated in a large-scale morphological phylogeny of Osteichthyes. The recovered phylogenetic hypothesis does not support the historical affiliation of †saurichthyiforms with chondrosteans, but recovers them, along with †Birgeria, 2 Abstract as the immediate sister group to crown actinopterygians. Yet the recovered topology is weakly supported, highlighting the need for similar studies to those conducted here in other extinct taxa. The early Permian actinopterygian †Brachydegma caelatum has had a central role in recent discussions on actinopterygian systematics, being often considered as an early neopterygian. However, previous phylogenies relied on interpretations of its external anatomy. The last chapter explores, for the first time, the endoskeletal anatomy of this key taxon, as revealed by µCT. †Brachydegma exhibits a mosaic of endoskeletal characters, such as the presence of only four gill arches, or the presence of a double jaw-joint that involves a true symplectic. These are nowadays encountered in distantly related actinopterygian lineages. New data from this and other actinopterygians suggest that the symplectic is not a neopterygian neomorph, and its involvement in the jaw joint is primitive for crown actinopterygians, or osteichthyans. The new phylogenetical hypothesis provided herein suggests that †Brachydegma is an early member of the actinopterygian crown group, the membership of which is now slightly expanded. 3 Zusammenfassung Actinopterygii (Strahlenflosser) wurden weniger schwer als viele andere Gruppen von marinen Organismen vom Massenaussterben an der Perm-Trias Grenze betroffen und konnten sich anschliessend in der Trias diversifizieren, was sie als erfolgreichste und artenreichste Gruppe innerhalb der Vertebraten etablierte. Abgesehen von der wachsenden Anzahl taxonomischer Arbeiten über die Perm und Trias Formen, bleiben ihre Paläobiologie und ihre Verwandtschaftsverhältnisse nur wenig verstanden. Diese Dissertation hat sich zum Ziel gesetzt neuartige anatomische Informationen von aussergewöhnlich gut erhaltenen Actinopterygiern aus dieser Zeit zu dokumentieren und zu analysieren, um ein lebhafteres Bild der Biologie dieser lang ausgestorbenen Lebewesen zu erschaffen. Die Ergebnisse werden in einem übergreifenden evolutionsbiologischen Kontext diskutiert. Viele der enthaltenen Arbeiten fokussieren sich auf die späten permischen