Univ.-Prof. Dr. Jürgen Kriwet Evolutionary History of Sharks, Rays and Skates (Chondrichthyes, Elasmobranchii) The fundamental goal of this research topic is to gain new and deeper insights into macroevolutionary patterns and processes of neoselachians such as their origin, diversity fluctuations, early evolution and mechanisms underlying evolutionary processes and novelties. The emphasis of this research lies on post-Jurassic forms, because the pre-Jurassic record of neoselachians comprises only a single identified group of stem-line representatives according to our current knowledge. It turned out very early during this project that the taxonomy and systematic position of most extinct neoselachians are in urgent need of revision before general patterns can be analysed. Therefore, most of the research is dedicated to identifying extinct neoselachian taxa and characters that can be used for taxonomic and systematic purposes. This information forms the basis for drawing general patterns of their early evolution, especially during the Jurassic. The Jurassic undoubtedly represents one of the most crucial periods in the evolution of neoselachians, because it was then when most modern clades had their first appearance in the fossil record. The ultimate objective of this long-term project is to reconstruct and understand the mechanisms underlying evolutionary processes, the importance of plesiomorphic characters in the evolution of neoselachians, to reconstruct diversity fluctuations and analyse (adaptive) radiation events. It is obvious from our current research that the taxonomy, systematics and evolutionary topics of fossil (and even extant) neoselachians remain incompletely known and understood despite all progress that has been accomplished in the last decades. This is mainly due to the lack of comprehensive morphological studies of fossil specimens including teeth, cranial and postcranial characters. Generally, fossil neoselachians are only known from their teeth, placoid scales and isolated fin spines. In some localities, however, articulated skeletal remains and even holomorphic specimens occur that contribute largely to our knowledge of past neoselachian anatomies and that might help, for instance, to infer character changes during their evolution. The limited data sets and inaccurate faunal descriptions continue to form a serious problem in analysing past diversity and related evolutionary patterns. Some of the problems could be corrected in the studies presented here by employing different phylogenetic methods such as cladistic principles and supertree approaches but also statistical procedures. It is also possible to infer distributional and diversity patterns from the data available and to interpret this in a non-phylogenetic framework. Thus, the papers summarized in this thesis provide new insights into a variety of topics related to the evolutionary history of neoselachians, but simultaneously pose many new questions that cannot be resolved momentarily. This thesis can provide only a first glimpse into the mechanism underlying the evolutionary history and success of this group. More research is necessary to understand their interrelationships, radiations and mechanisms determining their evolutionary success. 1 Univ.-Prof. Dr. Jürgen Kriwet According to the results obtained up to now, neoselachians first appeared in the Late Permian, some 250 Ma ago (if the fossil record of stem-group representatives is considered), but they already might have originated in the Devonian. After a prolonged period of taxonomic stasis (a single identified stem-group representative with a restricted number of genera and species) a first major radiation occurred in the Toarcian resulting in a significant increase in taxonomic diversity. Origination of new taxa was the predominant factor for taxonomic diversity increase during the following 115 Ma; extinction was at normal background extinction levels. It is well established that every new higher rank clade starts with a new species (that cannot be found in the fossil record according to the cladistic philosophy). The evolution of clade- founding species is assumed to depend strongly on ecological parameters and results in remodelling of previous bauplans. Obviously, an evolutionary burst in disparity might have occurred in the earliest Jurassic as indicated by the presence of several major neoselachian clades (Heterodontiformes, Orectolobiformes, Hexanchiformes, Batoidea) that displayed most probably a similar range in morphotypes as today preceding the taxonomic diversification at the end of the Early Jurassic. However, no detailed analyses have been conducted to verify this hypothesis to date. The Early Cretaceous obviously was an important time, because it was then that several neoselachian groups finally adapted to live permanently in the deep-sea and the open oceans. This might be considered a second major radiation event, although its amplitude certainly was less that the late Early Jurassic one. Then, ca. 65 Ma ago, a heavy biotic crisis also affected neoselachians at the K/T boundary. The reasons for this crisis are still discussed but obviously real. It took neoselachians 11–15 Ma to gain their pre-Cenozoic taxonomic diversity. The survivors of the K/T boundary event were mostly small and opportunistic sharks and very few batoids. They were the foundation for the last major diversification event in the evolutionary history of neoselachians that probably occurred in the Eocene leading towards contemporary diversity patterns. Today, one-quarter of all known sharks, rays and skates (total of 1,041 species) are threatened with extinction due to human activities (overfishing) (Dulvy et al. 2014: Extinction risk and conservation of the world’s sharks and rays. eLIFE;3:e00590). Other factors such as habitat degradation and loss also are considerable threats particular for freshwater elasmobranchs. Related Publications Scientific publications 1. KRIWET, J. 1995. Beitrag zur Kenntnis der Fisch-Fauna des Ober-Jura (unteres Kimmeridge) der Kohlengrube Guimarota bei Leiria, Mittel-Portugal: 1. Asteracanthus biformatus n. sp. (Chondrichthyes: Hybodontoidea). – Berliner geowissenschaftliche Abhandlungen, E 16: 683–691.* 2 Univ.-Prof. Dr. Jürgen Kriwet 2. KRIWET, J., RAUHUT, O.W.M. & GLOY, U. 1997. Microvertebrate remains (Pisces, Archosauria) from the Middle Jurassic (Bathonian) of southern France. – Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 206(1): 1–28. 3. KRIWET, J. 1997. Beitrag zur Kenntnis der Fischfauna des Oberjura (unteres Kimmeridgium) der Kohlengrube Guimarota bei Leiria, Mittel-Portugal: 2. Neoselachii (Pisces, Elasmobranchii). – Berliner geowissenschaftliche Abhandlungen, E 25: 293– 301.* 4. KRIWET, J. 1998. Late Jurassic elasmobranch and actinopterygian fishes from Portugal and Spain. – Cuadernos de Geología Ibérica, 24: 241–260. 5. KRIWET, J. 1999a. Neoselachier (Pisces, Elasmobranchii) aus der Unterkreide (unteres Barremium) von Galve und Alcaine (Spanien, Provinz Teruel). – Palaeo Ichthyologica, 9: 113–142. 6. KRIWET, J. 1999b. Ptychotrygon geyeri n.sp. (Chondrichthyes, Rajiformes) from the Utrillas Formation (upper Albian) of the central Iberian Ranges (East-Spain). – Profil, 16: 337–346.* 7. SCHULTZE, H.-P. & KRIWET, J. 1999. Die Fische der Germanischen Trias. – In: HAUSCHKE, N. & WILDE, V. (eds.): Trias. Eine ganz andere Welt. Mitteleuropa im frühen Erdmittelalter: 239–250; Verlag Dr. Friedrich Pfeil, München. 8. KRIWET, J. & KUSSIUS, K. 2001. Paleobiology and Paleobiogeography of slerorhynchid sawfishes (Chondrichthyes, Batomorphii). – Revista española de Paleontología, nº extraordinario: 35–46. 9. ARRATIA, G., KRIWET, J. & HEINRICH, W.-D. 2002. Selachians and actinopterygians from the Upper Jurassic of Tendaguru, Tanzania. – Mitteilungen aus dem Museum für Naturkunde zu Berlin, Geowissenschaftliche Reihe, 5: 207–230. 10. ABERHAN, M., BUSSERT, R., HEINRICH, W.-D., SCHRANK, E., SCHULTKA, S., SAMES, B., KRIWET, J. & KAPILIMA, S. 2002. Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania). – Mitteilungen aus dem Museum für Naturkunde Berlins, Geowissenschaftliche Reihe, 5: 19–44. 11. KRIWET, J. 2003a. First record of Early Cretaceous shark (Chondrichthyes, Neoselachii) from Antarctica. – Antarctic Science, 15: 519–523. 12. KRIWET, J. 2003b. Neoselachian remains (Chondrichthyes, Elasmobranchii) from the Middle Jurassic of SW Germany and NW Poland. – Acta Palaeontologica Polonica, 48(4): 587–598. 13. KRIWET, J. 2004a. Late Jurassic selachians (Chondrichthyes: Hybodontiformes, Neoselachii) from Central-Portugal. – Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 4: 233–256. 14. KRIWET, J. 2004b. The systematic position of the Cretaceous sclerorhynchid sawfishes (Elasmobranchii, Pristiorajea). – In: G. ARRATIA & TINTORI, A. (eds.): Mesozoic Fishes 3 – Systematics, Paleoenvironment and Biodiversity: 57–74; Verlag Dr. Friedrich Pfeil, München. 15. KRIWET, J. & BENTON, M. 2004. Neoselachian (Chondrichthyes, Elasmobranchii) diversity across the K/T boundary. – Palaeogeography, Palaeoclimatology, Palaeoecology, 214: 181–194. 16. KRIWET, J. & KLUG, S. 2004. Late Jurassic selachians (Chondrichthyes, Elasmobranchii) from southern Germany: Re-evaluation on taxonomy and diversity. – Zitteliana, A44: 67–95. 17. KRIWET, J. 2005. Additions to the Eocene selachian fauna of Antarctica with comments on Antarctic selachian diversity. – Journal of Vertebrate Paleontology, 25: 1–7. 3 Univ.-Prof. Dr. Jürgen