Jürgen Kriwet

University of Vienna | UniWien · Institut für Paläontologie

The fossil fish Ptychodus Agassiz, 1834, characterized by a highly distinctive grinding dentition and an estimated gigantic body size (up to around 10 m), has remained one of the most enigmatic extinct elasmobranchs (i.e. sharks, skates and rays) for nearly two centuries. This widespread Cretaceous taxon is common in Albian to Campanian deposits fr...

Batoids (skates and rays) are the most speciose group of cartilaginous fishes. Their body plan represents diverse ecologies and swimming modes. Early skeletal fossil remains, and recent phylogenetic analyses suggest that convergence has occurred within the batoids several times independently. The drivers for such disparity patterns and possible ass...

Study of the relationships of fossil and living billfishes is crucial for understanding the ecological drivers that control their biodiversity through time and how distributional patterns of extant populations may be affected by current abiotic events. Here we describe six istiophorid species that lived sympatrically in the central Mediterranean Se...

Abundant shark and rare actinopterygian teeth are reported from a locality within the early Eocene (Ypresian) lower part of the Crescent Formation exposed in the Hamma Hamma River valley on the eastern Olympic Peninsula, Washington State, USA. This part of the Crescent Formation is predominantly submarine volcanic basalt with some sedimentary inter...

Eocene climate cooling, driven by the falling pCO2 and tectonic changes in the Southern Ocean, impacted marine ecosystems. Sharks in high‐latitude oceans, sensitive to these changes, offer insights into both environmental shifts and biological responses, yet few paleoecological studies exist. The Middle‐to‐Late Eocene units on Seymour Island, Antar...

The biotic recovery and turnover following the Permian–Triassic mass extinction (PTME; ~252 mya) marks a key episode in the history of life on Earth, ultimately leading to the rise of modern marine faunas. Chondrichthyans (cartilaginous fishes) also were affected by the PTME, and only two lineages of non-holocephalan chondrichthyans, the hybodontif...

Hybodontiforms are among the most iconic groups of extinct chondrichthyan fishes to have ever existed and are the putative sister group to the elasmobranch crown group (i.e., modern sharks, rays and skates, plus their immediate fossil relatives). Appearing probably as early as the Late Devonian, hybodontiforms are characterized by a robust, shark-l...

Recognized as a UNESCO world heritage site, the Early Jurassic (Hettangian–Pliensbachian) mudstone- dominated succession, known as the “Lower Lias”, accessible along the coast at Lyme Regis in Dorset, UK, is famous for its rich fossil content, which has attracted considerable research interest since the beginning of the 19th century. The “Lower Lia...

The Pliocene is considered a natural climatic analog of the future climatic conditions of on planet. Thus, studying the geographical distribution of species during the Pliocene could provide clues about how current species might modify their distribution ranges over the coming decades. One of the most emblematic predators that has been present on o...

The Jurassic represents one of the main transitional periods for life. Recent studies unveiled a complex scenario in which abiotic and biotic factors, and drivers on regional and global scales due to the fragmentation of Pangaea, resulted in dramatic faunal and ecological turnovers, in terrestrial and marine environments. However, elasmobranch faun...

The time draws closer to the PalGes Meeting 2024 in Warsaw, and we are very excited to host you! We are honored to welcome you-over 160 participants based in 17 countries-to our conference meeting, integrated workshops, and our post-conference field trips. The PalGes meetings represent excellent opportunities for scientists working in these fields...

The KPg boundary event triggered a decline in post-Mesozoic neoselachian (sharks, rays, skates, and their closest relatives) diversity, followed by a 20 Ma-long recovery peaking in the Late Eocene. This diversity peak was then followed by a long-term decline until the present day, with only minor fluctuations slowing this process. However, the chan...

Squaliformes is the most specious group within the superorder Squalomorphii, consisting of six families: Squalidae, Centrophoridae, Etmopteridae, Somniosidae, Oxynotidae, and Dalatiidae. Their highly derived dentition, strong phenotypic plasticity, and ability to generate bioluminescence have made them very successful and enabled them to adapt to d...

Tectonic changes in the Southern Ocean likely triggered global cooling across the Eocene, yet the evidence for when the Drake Passage opened remains ambiguous. This climatic-tectonic change likely impacted marine ecosystems, including sharks that inhabited high-latitude regions. The fossil record could provide insights into sharks' response to glob...

The systematic position of the Jurassic shark, Phorcynis catulina Thiollière, 1852 is re-assessed using cladistic principles.

In this study, we are aiming to provide a deeper understanding of the factors that may play a significant role in driving and maintaining neoselachian diversity.

L’intervalle Jurassique supérieur–Crétacé inférieur représente l’une des phases de transition majeure de l’histoire du vivant. De part la fragmentation de la Pangée, une reconfiguration importante des paysages, suivie d’une phase d’océanisation, mena à l’apparition de nouvelles mers épicontinentales et peu profondes. Au cours du Jurassique supérieu...

Pycnodont fishes were a successful clade of neopterygian fishes that are predominantly found in shallow marine deposits. However, throughout their long 180 million year reign (Late Triassic-end Eocene), they made multiple incursions into both brackish and freshwater environments. This fossil record mostly consists of fragmentary dental material, bu...

The fossil record of chondrichthyans (chimaeras, sharks, rays and skates) consists largely of isolated teeth, with holomorphic specimens being extraordinary exceptions. However , numerous of these more or less completely preserved specimens are known from several Upper Jurassic deposits of Europe, enabling detailed analysis of their morphology. Bat...

Here we reviewed the fossil record of pycnodontiform fish remains from continental (freshwater) deposits to identify possible migration and invasion patterns. The main conclusions are that there is a huge spike in non-marine occurrences during the Cretaceous and that the most occurrences in non-marine localities occurred at the latest Cretaceous, t...

The megatooth shark, †Otodus megalodon, which likely reached at least 15 m in total length, is an iconic extinct shark represented primarily by its gigantic teeth in the Neogene fossil record. As one of the largest marine carnivores to ever exist, under�standing the biology, evolution, and extinction of †O. megalodon is important because it had a s...

(1) Background: Labial cartilages (LCs), as their name suggests, lie in the folds of the connective tissue, the lips, framing the gape of elasmobranch chondrichthyans. As such, these cartilages lie laterally to the jaws and marginal teeth. They are considered to influence the ability of creating suction during the feeding process. As past studies h...

Upper Cretaceous coastal marine deposits are widespread in the Southern Urals with a number of marine vertebrates previously reported from this region. However, previous studies on the vertebrate faunas in this region often lack detailed taxonomic descriptions and illustrations, rendering comparisons to other faunal assemblages difficult. A new di...

Struthiosaurus is a widespread European Late Cretaceous ankylosaur, with a stratigraphic range extending from the Campanian to the Maastrichtian. Traditionally included in the family Nodosauridae, Struthiosaurus is considered an example of insular dwarfism and is predicted to have reached a maximum body length of up to three meters. As currently ac...

Elasmobranchii are a relatively well-studied group. However, numerous phylogenetic uncertainties about their relationships remain un-answered. Recently, molecular analyses have shifted long-standing conceptions regarding their taxonomic and phylogenetic relationships. Here, we revisit the phylogenetic evidence based on a detailed morphological re-e...

We present preliminary results of a study focusing on Jurassic neoselachians based on a reassessment of the known skeletal remains of †Palidiplospinax and other Jurassic cartilaginous fishes employing cladistic and parsimony principles. Nineteen fossil genera and forty-one living ones were considered and a phylogenetic matrix with 160 characters wa...

Elasmobranchs (sharks, rays, skates) are a very successful group of cartilaginous fishes that have originated more than 400 million of years ago, survived almost all major extinction events and constantly occupied higher positions in past environments. It is possible to quantify their obvious evolutionary success using their long evolutionary persi...

Neoselachians (sharks, rays, skates and their closest relatives; aka Elasmobranchii) are one of the most successful groups of marine vertebrates. Phylogenetic hyp otheses commonly place the first diversification of modern forms (crown group) into the Early Jurassic. Representatives of both stem and crown neoselachian groups were present during this...

Phylogenetic, skeletal remains, Synechodontiformes, sharks Elasmobranchs (sharks, rays, skates) represent one of the most successful vertebrate groups, spanning a long geological time and continuously occupying essential roles in the food chain as predators and regulators of other groups. Notwithstanding recent attempts to improve our knowledge of...

Marine basins that existed in present-day Ukraine during the Eocene harboured various groups of cartilaginous and bony fishes, reptiles, aquatic birds, and marine mammals. Fish remains from Paleogene deposits of Kyiv and its vicinities were first collected and described by O.S. Rogovich in the mid-19th century. Here we have carried out a re-examina...

New isolated teeth from the Upper Cretaceous of Ukraine and belonging to the extinct durophagous shark Ptychodus are described here. The taxonomic identification of the examined material reveals a quite diverse Cenomanian shark fauna which comprised both cuspidate and un-cuspidate species of Ptychodus from the coastal areas at the north-western mar...

Studies of the origin of evolutionary novelties (novel traits, feeding modes, behaviours, ecological niches, etc.) have considered a number of taxa experimenting with new body plans, allowing them to occupy new habitats and exploit new trophic resources. In the marine realm, coloniza-tion of pelagic environments by marine fishes occurred recurrentl...

Elasmobranchs form a highly diversified monophyletic clade of marine vertebrates comprising all living sharks, rays, and skates, as well as their immediate fossil relatives. Within crowngroup elasmobranchs, two major shark groups, the Galeomorphii and the Squalomorphii, are repeatedly supported by molecular evidence, and with more than 290 extant s...

Elasmobranchs (sharks, rays, skates) represent one of the most successful vertebrate groups, spanning a long geological time and continuously occupying essential roles in aquatic food webs as predators and regulators of other groups. Notwithstanding recent attempts to improve our knowledge of shark and batoid (rays and skates) palaeobiodiversity pa...

Almost half of all chondrichthyan species in the Mediterranean Sea are threatened with extinction, according to the IUCN Red List. Due to a substantial lack of access to data on chondrichthyan catches in the Mediterranean Sea, especially of threatened species, the implementation of conservation measures is extremely insufficient. This also concerns...

Eurhinodelphinids are a family of extremely long-snouted dolphins that once was widespread across the North Atlantic realm, but so far has not been recorded from the epicontinental Paratethys Sea. Here, we describe a new specimen of Xiphiacetus cristatus, including the cranium, left ear bones and a partial mandible, from the Middle Miocene (Badenia...

Environmental controls of species diversity represent a central research focus in evolutionary biology. In the marine realm, sharks are widely distributed, occupying mainly higher trophic levels and varied dietary preferences, mirrored by several morphological traits and behaviours. Recent comparative phylogenetic studies revealed that sharks prese...

Strophodus is a speciose and geographically widespread taxon of large durophagous hybodontiform chondrichthyan, with a stratigraphic range extending from Middle Triassic to the Early Cretaceous. Here, we describe a new species of Strophodus, S. atlasensis sp. nov., based on an incomplete articulated dentition recovered from marine Bajocian deposits...

We present preliminary results of a study focusing on Jurassic neoselachians based on a re-assessment of the known skeletal remains of †Palidiplospinax and other Jurassic cartilaginous fishes employing cladistic and parsimony principles. Nineteen fossil genera and forty-one living ones were considered and a phylogenetic matrix with 160 characters w...

The Late Jurassic-Early Cretaceous (164–100 Ma) represents one of the main transitional periods in life history. Recent studies unveiled a complex scenario in which abiotic and biotic factors and drivers on regional and global scales due to the fragmentation of Pangaea resulted in dramatic faunal and ecological turnovers in terrestrial and marine e...

The Late Jurassic elasmobranch Protospinax annectans is often regarded as a key species to our understanding of crown group elasmobranch interrelationships and the evolutionary history of this group. However, since its first description more than 100 years ago, its phylogenetic position within the Elasmobranchii (sharks and rays) has proven controv...

Isolated teeth belonging to the genus Ptychodus Agassiz, 1834 (Chondrichthyes; Elasmobranchii) from the Upper Cretaceous of the Ryazan and Moscow Oblast regions (European Russia) are described and discussed in detail herein. The taxonomic composition of the Ptychodus assemblage from the Ryazan region is very diverse including the first records of t...

A new extinct sclerorhynchoid sawfish, Ptychotrygon ameghinorum sp. nov., is presented here based on abundant isolated teeth and some dermal denticles, which were recovered from the Mata Amarilla Formation, belonging to the lower Upper Cretaceous of the Santa Cruz Province in the Austral Basin of Patagonia, Argentina. This new species is the first...

Despite the rich fossil record of Neogene chondrichthyans (chimaeras, sharks, rays, and skates) from Europe, little is known about the macroevolutionary processes that generated their current diversity and geographical distribution. We compiled 4368 Neogene occurrences comprising 102 genera, 41 families , and 12 orders from four European regions (A...

Since its original description in the early 20th century, the phylogenetic position of the Late Jurassic elasmobranch Protospinax annectans has been heavily debated and it was suggested that this fossil fish represented either a stem group batoid (rays and skates), a stem group elasmobranch (sharks, skates, and rays), a crown group batoid, a stem g...

Elasmobranch (modern sharks and rays) and extinct hybodontiform fishes were the dominant chondrichthyan lineages during the Mesozoic, with elasmobranchs having a fossil record extending back into the Permian, but probably even reaching farther back since hybodontiforms representing their sister group are supposed to have originated in the Devonian....

Elasmobranchs (sharks, rays, skates) represent one of the most successful vertebrate groups, spanning a long geological time and continuously occupying essential roles in the food chain as predators and regulators of other groups. Notwithstanding recent attempts to improve our knowledge of shark and batoids (rays and skates) paleobiodiversity patte...

Hybodontiform shark teeth, cephalic and fin spines as well as placoid scales are reported here for the first time from the continental, Lower Triassic Dongchuan Formation near the village of Zhaojia (Huize County, Yunnan Province) in southwest China. The isolated teeth are assigned to three unidentified hybodontiforms but also to a new species of P...

Billfishes include some of the largest pelagic teleostean species, but several aspects about their morphology, paleobiology, and evolution remain ambiguous. Their fossil record is fragmentary and mostly represented by rostral and skull remains. Here, we present a comparative study of the caudal vertebral morphology of extant istiophorid species and...

Ytterbium ferrites are being used in many promising applications, such as visible-light photocatalysis, solar cells, magnetooptic devices, electro-magnetic equipment, etc., due to their fantastic ferroelectric and ferromagnetic properties. However, despite their good magnetic and radiopaque features, the use of ytterbium ferrites as multiplatform c...

With an estimated maximum body length of up to three meters and its massive, powerful jaws equipped with highly specialized crushing teeth suitable for breaking up various kinds of marine hard-shelled invertebrate prey, the extinct hybodontiform shark-like chondrichthyan Strophodus is one of the most iconic durophagous predators that ever roamed th...

Extant istiophorids are open ocean apex predators that are extensively studied due to their ecological importance and high values for fisheries. Nevertheless, little is known about their evolution because of a fragmentary fossil record and extremely difficult taxonomy of fossil species. Here, we present a new phylogenetic hypothesis covering fossil...

Shark teeth are one of the most abundant vertebrate fossils, and because tooth size generally correlates with body size, their accumulations document the size structure of populations. Understanding how ecological and environmental processes influence size structure, and how this extends to influence these dental distributions, may offer a window i...

Stingrays are a group of batoid fishes comprising more than 360 extant species in 11 families, typically characterized by venomous tail stings. Living taxa are grouped in two different ecomorphotypes, with most species (the dasyatoid ecomorph) living in demersal habitats being characterized by a benthic lifestyle; their rounded, flattened, soft and...

Elasmobranchii are relatively well-studied. However, numerous phylogenetic uncertainties about their relationships remain. Here, we revisit the phylogenetic evidence based on a detailed morphological re-evaluation of all the major extant batomorph clades (skates and rays), including several holomorphic fossil taxa from the Palaeozoic, Mesozoic and...

Two newly discovered specimens of passerine birds-an isolated sternum and an associated skeleton-from the upper Middle Miocene (ca. 12 Ma) are the oldest representatives of Passeriformes from Austria. Although the condition of the specimens prevents their accurate identification, they provide further clues on the morphological diversity of the avif...

Elasmobranchs, comprising sharks, skates, and rays, have a long evolutionary history extending back into the Palaeozoic. They are characterized by various unique traits including a predominantly cartilaginous skeleton, superficial prismatic phosphatic layer, and permanent tooth replacement. Moreover, they exhibit a more or less marked sexual dimorp...

A solvothermal route to prepare Glutathione capped hybrid ytterbium/iron oxide nanoparticles with potential applications as multiplatform contrast agent in medical image techniques has been developed. The influence of ytterbium/iron molar ratio used as precursor, as well as the degree of the autoclave filling on the structural and morphological cha...

The lifelong tooth replacement in elasmobranch fishes (sharks, rays and skates) has led to the assemblage of a great number of teeth from fossil and extant species, rendering tooth morphology an important character for taxonomic descriptions, analysing phylogenetic interrelationships and deciphering their evolutionary history (e.g. origination, div...

The Cretaceous was an important period in the evolution of vertebrates, both on land and in the oceans. Reconfiguration of landscapes by the Pangaean break-up and subsequent oceanic phase that opened new seaways enabled the establishment of new migration routes and also created wide, shallow epicontinental seas that are considered to boost diversit...

Extant billfishes represent some of the largest fishes in the open ocean in tropical to subtropical latitudes. They are at the top of oceanic food webs and contribute to their functioning and stability. Their distribution, population genomics and phylogeny have been extensively studied because of their ecological and fishery importance. Conversely,...

Background The onset of morphological differences between related groups can be tracked at early stages during embryological development. This is expressed in functional traits that start with minor variations, but eventually diverge to defined specific morphologies. Several processes during this period, like proliferation, remodelling, and apoptos...

Here, we provide a detailed taxonomic reassessment of a historically collected chondrichthyan dental assemblage from the lower Kimmeridgian of Czarnogłowy in north-western Poland and discuss its significance for better understanding hybodontiform diversity patterns prior to their post-Jurassic decline in fully marine environments. In spite of its l...

The first articulated dentition of †Ptychodus from Africa is described herein. The specimen, likely coming from the Turonian of the Asfla area (Goulmima region, southeastern Morocco), exhibits a well-preserved lower dental plate of a second-level predator. A new species, †P. maghrebianus sp. nov., is erected herein based on this durophagous dentiti...

Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoderms. In comparison to its sister group, the often club-tailed ankylosaurids, a different lifestyle of nodosaurids could be assumed based on their neuroanatomy and weaponry, e.g., regarding applied defensive strategies. The holotype of the nodosaurid Stru...

Every night the greatest migration on Earth starts in the deep pelagic oceans where organisms move up to the meso-and epipelagic to find food and return to the deeper zones during the day. One of the dominant fish taxa undertaking vertical migrations are the dragonfishes (Stomiiformes). However, the functional aspects of locomotion and the architec...