This research topic focuses on the relations between the evolution of organisms through time and extrinsic factors such as geological crises or climatic perturbations leading ultimately to modern biodiversity patterns. The fundamental goals thus are to gain new and deeper insights into macroevolutionary patterns and processes of vertebrates related to their origin, early evolution, diversity fluctuations, mechanisms of underlying evolutionary processes and novelties, bodyplan evolution, and timing of diversification events. The emphasis of this research lies on post-Palaeozoic groups, because during this time most living clades evolved. Nevertheless, Palaeozoic sister groups of other more basal positioned taxa will be included when necessary. Much of research conducted here is dedicated to identifying extinct taxa and morphological characters through analysis of living forms that can be used for taxonomic, systematic, and analytical purposes related to fossils and macroevolutionary events in deep-time. This information forms the basis for analysing trait changes and correlated dynamics in deep time and through time. Trait changes through time and adaptive processes will be analysed in a strict phylogenetic framework, which is dated using fossil record and molecular clock approaches and employing sophisticated analytical procedures for better understanding how diversity changed through time, external (abiotic) and internal (biotic) factors influence character transformations and thus bodyplans, what roles internal and external influences play in the establishment and subsequent evolution of modern vertebrate biotas, how fast evolution happens at both the morphological and molecular levels (Tempo: traditional interface between palaeontology and molecular genetics), and whether evolution at morphological and molecular levels is a continuous or divergent process (Mode: one of the current major controversies in palaeobiology). Research topics focus on (but are not restricted to):
Evolutionary History of Elasmobranchs (Sharks, Rays, and Skates)
It is obvious that the taxonomy, systematics and evolutionary topics of fossil (and even extant) neoselachians (sharks, rays, and skates), which represent crown chondrichthyans 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 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. 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, mechanisms underlying evolutionary processes and novelties, and timing of diversification events. The emphasis of this research lies on post-Triassic forms, because the pre-Jurassic record of neoselachians comprises only a single identified group of stem-line representatives according to our current knowledge. Nevertheless, sister groups to neoselachians, such as the hybodontiforms and other more basal positioned taxa will be included in this research topic. 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 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.
Triassic Recovery of Fishes
Recovery from extinctions and ecosystem building are key themes in conservation biology, but also in Earth sciences. Extinctions of species are important in maintaining and changing the Earth´s biodiversity. Extinction events result in a drastic reduction in the quantity of life on Earth and affect biodiversity directly. Five mass extinctions spanning the Phanerozoic have been identified up to now, each resulting in a loss of ca. 50% of all known species at the time. The end-Permian mass extinction 252 million years ago was the most severe and wiped out some 90% of marine species, and ecosystems were globally devastated. It is evident that the world after the end-Permian events remained largely devastated for the next 5 million years during the Early Triassic, causing delayed recoveries of life and normal ecosystem functioning at least until the Middle Triassic. However, recovery patterns of life during the Triassic still are incompletely known and understood despite all progress that has been accomplished in recent years, due to imprecise dating of fossil-bearing strata, uncertainties about the quality of the fossil record, and the lack of sound phylogenetic analyses of Triassic forms. This project aims at understanding mass extinctions and recoveries in deep time, macoevolutionary trait evolution, the complex interplay of increasing species richness and morphological disparity, and fine-tuning of ecosystems during diversification. Here, rigorous numerical studies of ecology and evolution such as connectivity between ecosystem balance and recovery, trait evolution (e.g. body size, feeding apparatus, locomotory appendages), and disparity of fishes will be employed. The ultimate goal of this project is to reveal (with ghost lineages) the timing, tempo and ecological nature of the recovery from the Permian-Triassic extinction event, and to test macroecological hypotheses. The integrated goals are to (1) complete documentation of Permian and Early and Middle Triassic marine fishes; (2) perform cladistic and composite phylogenies of relevant fish clades; (3) date these faunas accurately and integrate with the global-scale database on fish diversity through the Triassic; (4) analyse the evolution of different traits; (5) to explore disparity patterns; (6) establish local and global faunal relationships and endemism patterns of Triassic South China fishes; (7) analyse diversity and diversification patterns, and ecosystem dynamics, and, finally, (8) to integrate all results in a generalized model.
Evolutionary History of Pycnodontiform Fishes
Pycnodontiform fishes, which represent an extinct group of ray-finned fishes including more than 1000 nominal species are characterised by a deep, rounded, and laterally compressed body, a frontal flexure and prognathous snout, elongated dorsal and anal fins, which form together with the caudal fin an effective ruder, and distinct dentitions with teeth being mainly restricted to the prearticulars and the vomer. The dentition is assumed by most authors to be indicative for durophageous feeding habits. They resemble superficially in their body-shape extant coral reef fishes like the butterflyfishes (Chaetodontidae), doctor fishes (Acanthuridae), and parrotfishes (Balistidae). Their characteristic highly developed and specialised crushing heterodont dentition has long been a leading character in taxonomy and systematics for the last 170 years. Most pycnodontiform taxa are based entirely on characteristics of their prearticular or vomerine dentitions. The squamation pattern of pycnodontiforms fishes ranges from complete (covering the body from the posterior margin of the skull to the beginning of the caudal fin) to completely reduced with different intermediate stages. The scales of pycnodontiforms are rhombic and resemble the lepidosteoid scale type. However, the surfaces of the scales lack the ganoin layer, which is characteristic for this type and the term modified lepidosteoid scale type was introduced for pycnodont scales. The dermal skull bones also lack the ganoin layer. Additionally, these fishes are characterized by the lack of ossified vertebral centra, the significance of which still is not unambiguously established. The monophyly of pycnodontiforms fishes is well supported. The relationships among these fishes and of pycnodontiforms to other actinopterygians, however, have been discussed controversial for a long time and no general agreement has been achieved up to now. This project focuses on the (1) morphology, (2) taxonomy and systematics, (3) evolution, (4) functional aspects of the feeding apparatus, (5) ecology, and (6) palaeobiogeography of pycnodontiform fishes (Neopterygii, Pycnodontomorpha).
Evolution and Diversity Patterns of Southern Ocean Fishes
The extant fish fauna of the Southern Ocean surrounding the Antarctic continent is striking in its low taxonomic diversity and high number of endemic taxa with fishes that evolved special morphological and physiological traits to cope with the extreme low sea temperatures being dominant. This very restricted modern fish fauna with just 322 described species seemingly replaced a diverse and cosmopolitan Eocene fish fauna. Today, about 90% of the teleosts are endemic to the Antarctic Ocean and the fauna is dominated by notothenioid teleosts (ca. 45% of benthic Antarctic fishes). The origin and evolution of these perfectly adapted fishes to the sub-zero temperatures of the Southern Ocean still are disputed despite some putative fossil records (isolated skull, jaw fragments) from the Eocene of Seymour Island. It is assumed that cold adapted notothenioids evolved by directional selection and geographic isolation of Antarctica prior to 24 Ma based on molecular clock approaches using a putative notothenioid fossil from Seymour Island. Evolution of the very distinct modern Antarctic fish fauna also is considered being related to low temperatures, isolation of the Southern Ocean due to the break-up of Gondwana and continuous opening and deepening of the Tasman and Drake passages, habitat loss, and climatic cycles by others. Chondrichthyans (chimaeroids, sharks, rays, skates) seemingly were major faunal contents of pre-Oligocene Antarctic fish faunas. Today, the chondrichthyan fauna within the Southern Ocean surrounding Antarctica, however, is extremely impoverished. Up to now, only three sharks were reported from few specimens mostly off the Kerguelen Plateau and it still is not established whether these sharks enter the Antarctic Convergence only sporadically or represent permanent residents. Batoid diversity, conversely, is slightly higher with eight resident species having been described. Holocephalans have not been recorded from Antarctic waters so far. Eocene strata of Seymour Island (Antarctic Peninsula) yielded the most diverse Palaeogene ichthyofauna from the Southern Hemisphere known to date. Additional, rare material comes from Eocene deposits of Mount Discovery in East Antarctica. These fishes are of utmost importance for understanding evolutionary and adaptive processes in marine vertebrates related to plate-tectonic and climatic processes and thus are important for subsequent work in evolutionary (palaeo)biology, ecology, zoogeography, and conservation. See also www.univie.ac.at/Palaeontologie/Kriwet.html.
Diversity Patterns of Neogene Chondrichthyan and Actinopterygian Fishes
A large, epicontinental sea, the Paratethys, covered wide areas of Europe and western Asia during the Miocene. It is known that the rising sea levels during the early Middle Miocene (followed by a sharp decline in sea levels at the Burdigalian/Langhian transition) and the associated climatic optimum had major impacts on molluscs and echinoderms at the Early/Middle Miocene transition.>br>While the Mediterranean Sea was part of the Tethys and connected to the Atlantic as well as the Indo-Pacific in the Cretaceous (145-65 Mya), it subsequently became isolated from the Indo-Pacific and Atlantic by Miocene times due to sea level changes, tectonic activities and erosion and deposition events. These events also resulted in the differentiation of the former Tethys in central Europe into different basins including the Paratethys. This epicontinental sea extended from the northern margin of the Mediterranean Sea, from which it was separated by the Alps, Dinarids, Hellenids and the Anatolian Massif in the Miocene from the Oligo- to Miocene. However, marine connections between the Paratethys and the Mediterranean Sea existed during the Early/Middle Miocene transition enabling faunal exchanges. Fossil fish remains are very abundant at the Early/Middle Miocene transition in the Paratethys transition. Preservation varies and includes isolated skeletal remains (bones, teeth, otoliths) and holomorphic (complete) specimens. The Miocene fish faunas of the southern German Molasse and the Austrian Vienna basins probably are the most diverse Miocene bony fish assemblages and were the focus of several studies in the last 150 years. However, the focus of most if not all of these studies was on the taxonomic description of single assemblages. No detailed analyses of diversity changes throughout the Miocene of the central Paratethys and faunal relationships with western and eastern Paratethys faunas have been carried out up to date. The goals of this project are to (1) revise fossil fish remains from the Miocene of the Molasse and Vienna basins, (2) establish biogeographic relationships between central Paratethyan and Mediterranean fish assemblages, (3) reconstruct diversity and diversification patterns across the Early/Middle Miocene transition using all available fish records and employing robust resampling and rarefaction approaches, (4) reconstruct the anatomical diversity of fishes at this transition using morphometric methodologies to (1) identify endemism patterns and native and/or immigrant taxa of Miocene Paratethyan fishes, (2) identify major shifts in taxonomical and morphological diversity of bony fishes across this transition, (3) to test whether the climatic change at the transition shaped trajectories of fish diversification and (4) identify speciation and evolutionary processes based on diversification analyses.
Functional morphology generally assumes a direct link between morphology and performance or function. Thus, behaviour supposedly influences the relationship between morphology and performance and therefore, morphological characteristics predict performance and/or behaviour. Functional analyses commonly use approaches of correlating skeletal structures with performance and eco-morphological studies. Seemingly, however, these approaches and the analyses employed have reached their limits. The important question here is not only how a structure works, but why did it evolve this way and what are the consequences? Research projects include inter alia:
Evolution of Adaptive Traits in Fishes
Revision of the concept of complex, intermediate, and open habitat fishes and correlated evolutionary adaptive events. In this emerging research area, we intend to combine relationships between morphology and performance in extinct organisms with soft-part structures and will employ modern analytical approaches, which are generally used only in living organisms. The strength of analysing functional morphology and functional ecology based on soft-part and related skeletal structures (e.g., attachment points) in living and extinct organisms within an evolutionary framework is to facilitate understanding the mechanisms underlying adaptive processes and adaptive patterns.
Evolution and Adaptation of Fishes to the Deep-Sea
The adaptation of fishes to deep-sea conditions is another emerging topic. Generally, it is assumed that the modern deep-sea benthic fish fauna originated in shallow waters and subsequently replaced ancient deep-sea assemblages, which became eliminated by mass extinction events. This indicates that extinction events are the main trigger for deep-sea colonization of fishes. It also is generally assumed that plesiomorphic ray-finned fish groups have more deep-sea representatives than derived ones. This study, however, is based on maximum depth occurrence data of living forms, which might be prone to error as these authors indicate. The timing and underlying processes / reasons remain ambiguous. Moreover, no definition for deep-sea fishes currently exists. Here, we intend to identify key innovations in the musculoskeletal system and to establish morphological traits for identifying deep-sea fishes. This is essential for reconstructing evolutionary traits and pathways of modern deep-sea fishes. Additionally, reliable fossil record analyses for dating such adaptive events but also diversifications in the deep will be developed and employed for providing alternative hypotheses to those currently based on molecular clocks.
Phylogenetic and Functional Traits of the Vertebrate Inner Ear
Locomotion in tetrapods generally is inferred from the morphology of the postcranial skeleton. Conversely, the anatomy of the inner ear as the organ of equilibrium can also be used for predicting locomotion types of investigated species, e.g. rodents. Enclosed by bony elements of the skull, this sense organ can be investigated non-invasively by using micro-CT scanning (SkyScan 1173) and reconstructed virtually as a 3D modell. The shape of the three semicircular canals (ASC, PSC, LSC) is analysed with 3D measurements but also 3D geometric morphometrics for reconstructing chronophylomorphospaces in time and space. This is a new approach for identifying evolutionary trait changes in ear structures related to locomotion and to distinguish phylogenetic and functional signals in the ear in a temporal and spatial framework.
Evolution of the Vertebrate Middle Ear
Phylogenetic investigations of the ear region are mainly focussing on the anatomy of the middle ear cavities and auditory ossicles.
Septal compass and septal formula
In the last century, the bony septa in the recessus epitympanicus and the cavum tympani and the pneumatization of the tympanic and mastoid region were described, but their phylogenetic value was not recognized. Comparative investigations of different species of squirrels show remarkable differences in the distribution of the bony septa. For a better visualization and phylogenetic investigation, the septal compass for illustrating the characteristic internal anatomy of the ear region and the ´septal formula´ as a numeric description of this anatomy were developed. This phylogenetic approach will be continued in other groups of mammals.
Since Doran 1873, anatomical investigations of the auditory ossicles are of minor interest. However, this part of the middle ear is highly conservative within different groups of mammals and enables phylogenetic assumptions. With the benefits of non-invasive micro-CT scanning, the middle ear of different groups of mammals is under consideration.