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Jürgen Kriwet

University of Vienna, Department of Palaeontology, Faculty Member

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I am a palaeoichthyologist with a strong interest in the development and evolution of characters and biodiversity patterns of vertebrates in deep time. Multidisciplinary approaches are employed to understand evolutionary processes, morphological rate changes, adaptive trait developments, and diversity patterns at the broadest temporal and spatial scales. I use chondrichthyan fishes as model organisms because they display conserved but also highly derived traits (e.g., reduction of a bony dermal and endoskeleton) within gnathostomes.
Phone: ++43 1 4277 535 20
Address: Department of Palaeontology
University of Vienna
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1090 Vienna, Austria

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University of Florida

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Università di Pisa

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Museum für Naturkunde Berlin

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Papers by Jürgen Kriwet

First evidence of a palaeo-nursery area of the great white shark

Scientific Reports, 2020

Shark nurseries are essential habitats for shark survival. Notwithstanding the rich fossil record... more Shark nurseries are essential habitats for shark survival. Notwithstanding the rich fossil record of the modern great white shark (Carcharodon carcharias, GWS), its use of nursery areas in the fossil record has never been assessed before. Here, we analysed the fossil record of the GWS from three South American Pliocene localities, assessed body size distributions and applied previously established criteria to identify palaeo-nurseries. We found that juveniles dominate the Coquimbo locality (Chile), whereas subadults and adults characterize Pisco (Peru) and Caldera (Chile), respectively. These results, summed to the paleontological and paleoenvironmental record of the region, suggest that Coquimbo represents the first nursery area for the GWS in the fossil record. Our findings demonstrate that one of the top predators in today’s oceans has used nursery areas for millions of years, highlighting their importance as essential habitats for shark survival in deep time.

On the need of providing tooth morphology in descriptions of extant elasmobranch species

Zootaxa, Jan 20, 2018

Elasmobranchii is a clade of chondrichthyans (cartilaginous fishes) that comprises sharks, skates... more Elasmobranchii is a clade of chondrichthyans (cartilaginous fishes) that comprises sharks, skates and rays represented today by approximately 1,200 species. Chondrichthyans have a long evolutionary history dating back to the Late Ordovician (ca. 450 million years ago [Mya]) based on isolated dermal denticles (Janvier 1996). Other remains such as articulated skeletons and teeth are known from the Lower Devonian (ca. 410 Mya: Mader 1986; Miller et al. 2003). The fossil record of modern elasmobranchs (Neoselachii) can be traced back to the Early Permian (ca. 290 Mya) and is represented by isolated teeth (Ivanov 2005), with fossils of crown group sharks and rays appearing in Lower Jurassic (ca. 200 Mya) rocks (e.g., Cappetta 2012). Since their appearance in the geological record, elasmobranchs are mainly represented by isolated teeth, whereas articulated skeletons are very rare and restricted to a small number of fossil localities (e.g., Cappetta 2012). The scarcity of skeletal remains ...

Eocene isopods on electric rays: tracking ancient biological interactions from a complex fossil record

Palaeontology, Oct 10, 2018

F I G. 1. The Monte Postale deposit. Location and geological map of the Bolca area, showing the M... more

Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria

Scientific Reports, Jan 7, 2022

Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoder... more 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 Struthiosaurus austriacus consists of a single partial braincase from the Late Cretaceous of Austria. Since neuroanatomy is considered to be associated with ecological tendencies, we created digital models of the braincase based on micro-CT data. The cranial endocast of S. austriacus generally resembles those of its relatives. A network of vascular canals surrounding the brain cavity further supports special thermoregulatory adaptations within Ankylosauria. The horizontal orientation of the lateral semicircular canal independently confirms previous appraisals of head posture for S. austriacus and, hence, strengthens the usage of the LSC as proxy for habitual head posture in fossil tetrapods. The short anterior and angular lateral semicircular canals, combined with the relatively shortest dinosaurian cochlear duct known so far and the lack of a floccular recess suggest a rather inert lifestyle without the necessity of sophisticated senses for equilibrium and hearing in S. austriacus. These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions. Thyreophora are ornithischian dinosaurs, comprising iconic taxa like Stegosaurus and Ankylosaurus 1. Ankylosauria thrived at least since the Middle Jurassic and some of their representatives witnessed the end-Cretaceous mass extinction 1. These globally distributed quadruped herbivores were heavily armoured living fortresses; partly either equipped with a club tail (ankylosaurids 2) or a collar of hypertrophied spikes on their neck and shoulders (nodosaurids 3). Potential palaeoenvironmental 4 and food preferences 5 , together with features of their nasal passages 6 , jaw mechanics 7,8 and osteoderms 9 , may indicate different lifestyles for both groups. Since the brain and associated neuroanatomical structures of vertebrates leave perceivable traces, which are possibly ecologically informative, it is worthwhile to thoroughly examine the braincase of nodosaurids in order to compare it to ankylosaurids. Whereas complete braincase material among early-diverging thyreophorans is only known from Scelidosaurus harrisoni 10 , neurocranial material of stegosaurs 11,12 , and ankylosaurs (e.g. 13-15) is more common. The heavily armored skull roofs of the latter likely improved their preservation potential. Struthiosaurus is a European nodosaurid with an estimated body length of up to three metres, known from cranial and postcranial material of Campanian to Maastrichtian age 16-22. As currently accepted, Struthiosaurus comprises three species: S. austriacus from the early Campanian of Austria 16-18 , S. languedocensis from the early Campanian of France 22 , and S. transylvanicus from the Maastrichtian of Romania 23,24. In addition, skeletal remains referred to Struthiosaurus sp. were reported from late Campanian to early Maastrichtian deposits of

Paleoecology and depositional environment of the Tendaguru Beds, Upper Jurassic-Lower Cretaceous of Tanzania, East Africa

Evolutionary Development of the Postcranial and Appendicular Skeleton in Fishes

Cambridge University Press eBooks, Dec 31, 2018

Virtual reconstruction of the skeletal labyrinth of two lamnid sharks (Elasmobranchii, Lamniformes)

Journal of Fish Biology, Nov 22, 2016

The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and... more The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and the shortfin mako shark Isurus oxyrinchus is presented here using high-resolution micro-computed tomography. The results, in comparison with previously published information, suggest relationships between skeletal labyrinth morphology and locomotion mode in chondrichthyans, but also show that further studies are required to establish such connections. Nevertheless, this study adds to the knowledge of the skeletal labyrinth morphology in two apex elasmobranch species.

Topology optimized and 3D printed polymer-bonded permanent magnets for a predefined external field

Journal of Applied Physics, Aug 7, 2017

Topology optimization offers great opportunities to design permanent magnetic systems that have s... more Topology optimization offers great opportunities to design permanent magnetic systems that have specific external field characteristics. Additive manufacturing of polymer bonded magnets with an end-user 3D printer can be used to manufacture permanent magnets with structures that have been difficult or impossible to manufacture previously. This work combines these two powerful methods to design and manufacture permanent magnetic system with specific properties. The topology optimization framework is simple, fast, and accurate. It can be also used for reverse engineering of permanent magnets in order to find the topology from field measurements. Furthermore, a magnetic system that generate a linear external field above the magnet is presented. With a volume constraint the amount of magnetic material can be minimized without losing performance. Simulations and measurements of the printed system show a very good agreement.

3D models related to the publication: Ontogenetic development of the otic region in the new model organism, Leucoraja erinacea (Chondrichthyes; Rajidae)

MorphoMuseuM, Feb 5, 2019

Anatomy, relationships and palaeobiogeographic implications of the first Neogene holomorphic stingray (Myliobatiformes: Dasyatidae) from the early Miocene of Sulawesi, Indonesia, SE Asia

Zoological Journal of the Linnean Society, May 12, 2018

The early Miocene stingray †Trygon vorstmani represented by a single specimen collected from the ... more The early Miocene stingray †Trygon vorstmani represented by a single specimen collected from the fish-bearing limestones of the Tonasa Formation of SW Sulawesi, Indonesia, is redescribed here in detail. This taxon exhibits a unique combination of features that clearly support the presence of a new genus, †Protohimantura gen. nov. and its assignment to the whiptail stingrays (Dasyatidae) of the subfamily Urogymninae. The morphological and phylogenetic affinities of †Protohimantura gen. nov. with the living whiprays suggest a close association of this taxon with tropical shallow-water habitats hypothesized for the SW Sulawesi palaeoenvironment during early Miocene. Moreover, this occurrence, which also represents the first holomorphic stingray specimen from the Neogene, provides new insights into the role of the Indo-Australian Archipelago for the evolutionary history of fishes associated with reefs in the context of the shift of the marine biodiversity hotspot across the globe during the last 50 million years.

Comment on “An early Miocene extinction in pelagic sharks”

Science, Dec 10, 2021

Musculotendinous system of mesopelagic fishes: Stomiiformes (Teleostei)

Journal of Anatomy, Dec 19, 2021

Every night the greatest migration on Earth starts in the deep pelagic oceans where organisms mov... more 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 architecture of the musculotendinous system (MTS) in these fishes have never been examined. In general, the MTS is organized in segmented blocks of specific three-dimensional 'W-shaped' foldings, the myomeres, separated by thin sheets of connective tissue, the myosepta. Within a myoseptum characteristic intermuscular bones or tendons may be developed. Together with the fins, the MTS forms the functional unit for locomotion in fishes. For this study, microdissections of cleared and double stained specimens of seven stomiiform species (Astronesthes sp., Chauliodus sloani, Malacosteus australis, Eustomias simplex, Polymetme sp., Sigmops elongatus, Argyropelecus affinis) were conducted to investigate their MTS. Soft tissue was investigated non-invasively in E. schmidti using a micro-CT scan of one specimen stained with iodine. Additionally, classical histological serial sections were consulted. The investigated stomiiforms are characterized by the absence of anterior cones in the anteriormost myosepta. These cones are developed in myosepta at the level of the dorsal fin and elongate gradually in more posterior myosepta. In all but one investigated stomiiform taxon the horizontal septum is reduced. The amount of connective tissue in the myosepta is very low anteriorly, but increases gradually with body length. Red musculature overlies laterally the white musculature and exhibits strong tendons in each myomere within the muscle bundles dorsal and ventral to the horizontal midline. The amount of red musculature increases immensely towards the caudal fin. The elongated lateral tendons of the posterior body segments attach in a highly complex pattern on the caudal-fin rays, which indicates that the posterior most myosepta are equipped for a multisegmental force transmission towards the caudal fin. This unique anatomical condition might be essential for steady swimming during diel vertical migrations, when prey is rarely available.

First eurhinodelphinid dolphin from the Paratethys reveals a new family of specialised echolocators

Historical Biology, Jun 10, 2022

Evolutionary trends of the conserved neurocranium shape in angel sharks (Squatiniformes, Elasmobranchii)

Scientific Reports, Jul 28, 2020

elasmobranchii (i.e., sharks, skates, and rays) forms one of the most diverse groups of marine pr... more elasmobranchii (i.e., sharks, skates, and rays) forms one of the most diverse groups of marine predators. With a fossil record extending back into the Devonian, several modifications in their body plan illustrate their body shape diversity through time. the angel sharks, whose fossil record dates back to the Late Jurassic, some 160 Ma, have a dorsoventrally flattened body, similar to skates and rays. fossil skeletons of this group show that the overall morphology was well established earlier in its history. By examining the skull shape of well-preserved fossil material compared to extant angel sharks using geometric morphometric methods, within a phylogenetic framework, we were able to determine the conservative skull shape among angel sharks with a high degree of integration. the morphospace occupation of extant angel sharks is rather restricted, with extensive overlap. Most of the differences in skull shape are related to their geographic distribution patterns. We found higher levels of disparity in extinct forms, but lower ones in extant species. Since angel sharks display a highly specialized prey capture behaviour, we suggest that the morphological integration and biogeographic processes are the main drivers of their diversity, which might limit their capacity to display higher disparities since their origin. Elasmobranchs (sharks, skates, and rays) represent a lineage of vertebrates with a fossil record extending over 400 million years 1,2. Throughout their evolutionary history, adaptations of feeding mechanisms, behavioural specializations and ecological distributions are well reflected in their body plan 3,4. Most modern sharks display rather conservative overall body shapes 5 , for most of the pelagic species, and distinguishable from the benthic species 6 , also some specific morphological traits like the neurocranium may vary strongly in shape, as seen in the hammerhead and sawsharks 7-10. Another example of extreme morphology is displayed by angel sharks (Squatiniformes), which are characterized by highly dorsoventrally compressed bodies similar to batomorphs (i.e., skates and rays). This similarity caused controversies in their phylogenetic placement 11,12 , but their systematic position within sharks 13-16 and intra-relationships 17 are well resolved (Fig. 1). All the 22 living valid species of the squatiniforms are included in a single genus, Squatina 18-20. Living angel sharks can be divided into clades that follow a biogeographical pattern explained both by vicariant and dispersion events during the last 20 million years, forming distinct Europe-North African, South African, Asian, Australian, North American and South American clades 17. More recently, it has been suggested that the species from North and South America can be differentiated into eastern and western clades 21. The evolutionary history of angel sharks can be traced back into the Oxfordian (Late Jurassic; 160 Ma), with several specimens initially assigned to Squatina, but later transferred to the genus †Pseudorhina in the family †Pseudorhinidae, ranging from the Oxfordian to the Tithonian 22,23. Extant members of the order Squatiniformes have a fossil record that dates back to the Early Cretaceous 23,24. The body plan of Squatiniformes nevertheless, arose during the Late Jurassic, based on holomorphic fossil specimens, which remains consistent with only few changes to date (Fig. 1B,C). Another feature present in some of the holomorphic fossil species is the

Systematics and Phylogenetic Interrelationships of the Enigmatic Late Jurassic Shark Protospinax annectans Woodward, 1918 with Comments on the Shark–Ray Sister Group Relationship

Diversity

The Late Jurassic elasmobranch Protospinax annectans is often regarded as a key species to our un... more 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 controversial, and a closer relationship between Protospinax and each of the posited superorders (Batomorphii, Squalomorphii, and Galeomorphii) has been proposed over the time. Here we revise this controversial taxon based on new holomorphic specimens from the Late Jurassic Konservat-Lagerstätte of the Solnhofen Archipelago in Bavaria (Germany) and review its skeletal morphology, systematics, and phylogenetic interrelationships. A data matrix with 224 morphological characters was compiled and analyzed under a molecular backbone constraint. Our results indicate a close relationship between Protospinax, angel sharks (Squatiniformes), and saw sharks...

A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships

Diversity

The Late Jurassic-Early Cretaceous (164–100 Ma) represents one of the main transitional periods i... more 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 environments. However, chondrichthyan faunas from this interval have received surprisingly little recognition. The presence of numerous entire skeletons of chondrichthyans preserved in several localities in southern Germany, often referred to as Konservat-Lagerstätten (e.g., Nusplingen and the Solnhofen Archipelago), provides a unique opportunity of to study the taxonomic composition of these assemblages, their ecological distributions and adaptations, and evolutionary histories in detail. However, even after 160 years of study, the current knowledge of southern Germany’s Late Jurassic chondrichthyan diversity remains incomplete. Over the l...

Scanning pulsed laser ablation in liquids: An alternative route to obtaining biocompatible YbFe nanoparticles as multiplatform contrast agents for combined MRI and CT imaging

Ceramics International

Solvothermal synthesis and characterization of ytterbium/iron mixed oxide nanoparticles with potential functionalities for applications as multiplatform contrast agent in medical image techniques

Ceramics International

A solvothermal route to prepare Glutathione capped hybrid ytterbium/iron oxide nanoparticles with... more 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 characteristics of the obtained nanoparticles has been extensively studied. Although all nanoparticles present similar composition, with YbFeO 3 being the majority phase, size and morphology of the as synthetized nanoparticles are highly influenced by the critical temperature and by the over-saturation reached during the solvothermal process. We have demonstrated that glutathione properly functionalizes the hybrid nanoparticles, increasing their colloidal stability and decreasing their cytotoxicity. Additionally, they show good imaging in magnetic resonance and X-ray computerized tomography, thereby indicating promising potential as a dual contrast agent. This work presents, for the first time, glutathione functionalized ytterbium/iron oxide nanoparticles with potential applications in Biomedicine.

Two passeriform birds (Aves: Passeriformes) from the Middle Miocene of Austria

PalZ, 2021

Two newly discovered specimens of passerine birds—an isolated sternum and an associated skeleton—... more 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 avifauna during this period and fill gaps in the paleobiogeography of Miocene passerines. The associated skeleton represents a bird similar in size to the extant Sylvia atricapilla or Erithacus rubecula, and the delicate beak indicates that the bird fed mainly on small invertebrates and possibly also soft fruit. The isolated sternum belonged to a small thrush-sized bird and, considering the fragility of this skeletal element, is one of the best-preserved Miocene passerine sterna in the world.

Using Citizen Science to Detect Rare and Endangered Species: New Records of the Great White Shark Carcharodon Carcharias off the Libyan Coast

Annales. Series historia naturalis : anali za istrske in mediteranske studije = annali di studi istriani e mediterranei = annals of Istrian and Mediterranean studies, 2021

The presence of the great white shark (Carcharodon carcharias) in the Mediterranean Sea is well d... more The presence of the great white shark (Carcharodon carcharias) in the Mediterranean Sea is well documented, but encounters with this species are rare and all assumptions about its spatial and temporal distribution are heavily relying on anecdotal observations. To date, only one record off the Libyan coast has been reported, raising the question if this species is underreported in these waters or simply represents a rare occasional transient. We utilised citizen science-sourced data to document the presence of the great white shark off the Libyan coast, and found six additional records for this species from the period between 2017 and 2020. Our study points out the need for scientific monitoring of this species along the Libyan coast to facilitate the establishment of effective conservation plans to protect this critically endangered species.

First evidence of a palaeo-nursery area of the great white shark

Scientific Reports, 2020

Shark nurseries are essential habitats for shark survival. Notwithstanding the rich fossil record... more Shark nurseries are essential habitats for shark survival. Notwithstanding the rich fossil record of the modern great white shark (Carcharodon carcharias, GWS), its use of nursery areas in the fossil record has never been assessed before. Here, we analysed the fossil record of the GWS from three South American Pliocene localities, assessed body size distributions and applied previously established criteria to identify palaeo-nurseries. We found that juveniles dominate the Coquimbo locality (Chile), whereas subadults and adults characterize Pisco (Peru) and Caldera (Chile), respectively. These results, summed to the paleontological and paleoenvironmental record of the region, suggest that Coquimbo represents the first nursery area for the GWS in the fossil record. Our findings demonstrate that one of the top predators in today’s oceans has used nursery areas for millions of years, highlighting their importance as essential habitats for shark survival in deep time.

On the need of providing tooth morphology in descriptions of extant elasmobranch species

Zootaxa, Jan 20, 2018

Elasmobranchii is a clade of chondrichthyans (cartilaginous fishes) that comprises sharks, skates... more Elasmobranchii is a clade of chondrichthyans (cartilaginous fishes) that comprises sharks, skates and rays represented today by approximately 1,200 species. Chondrichthyans have a long evolutionary history dating back to the Late Ordovician (ca. 450 million years ago [Mya]) based on isolated dermal denticles (Janvier 1996). Other remains such as articulated skeletons and teeth are known from the Lower Devonian (ca. 410 Mya: Mader 1986; Miller et al. 2003). The fossil record of modern elasmobranchs (Neoselachii) can be traced back to the Early Permian (ca. 290 Mya) and is represented by isolated teeth (Ivanov 2005), with fossils of crown group sharks and rays appearing in Lower Jurassic (ca. 200 Mya) rocks (e.g., Cappetta 2012). Since their appearance in the geological record, elasmobranchs are mainly represented by isolated teeth, whereas articulated skeletons are very rare and restricted to a small number of fossil localities (e.g., Cappetta 2012). The scarcity of skeletal remains ...

Eocene isopods on electric rays: tracking ancient biological interactions from a complex fossil record

Palaeontology, Oct 10, 2018

F I G. 1. The Monte Postale deposit. Location and geological map of the Bolca area, showing the M... more

Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria

Scientific Reports, Jan 7, 2022

Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoder... more 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 Struthiosaurus austriacus consists of a single partial braincase from the Late Cretaceous of Austria. Since neuroanatomy is considered to be associated with ecological tendencies, we created digital models of the braincase based on micro-CT data. The cranial endocast of S. austriacus generally resembles those of its relatives. A network of vascular canals surrounding the brain cavity further supports special thermoregulatory adaptations within Ankylosauria. The horizontal orientation of the lateral semicircular canal independently confirms previous appraisals of head posture for S. austriacus and, hence, strengthens the usage of the LSC as proxy for habitual head posture in fossil tetrapods. The short anterior and angular lateral semicircular canals, combined with the relatively shortest dinosaurian cochlear duct known so far and the lack of a floccular recess suggest a rather inert lifestyle without the necessity of sophisticated senses for equilibrium and hearing in S. austriacus. These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions. Thyreophora are ornithischian dinosaurs, comprising iconic taxa like Stegosaurus and Ankylosaurus 1. Ankylosauria thrived at least since the Middle Jurassic and some of their representatives witnessed the end-Cretaceous mass extinction 1. These globally distributed quadruped herbivores were heavily armoured living fortresses; partly either equipped with a club tail (ankylosaurids 2) or a collar of hypertrophied spikes on their neck and shoulders (nodosaurids 3). Potential palaeoenvironmental 4 and food preferences 5 , together with features of their nasal passages 6 , jaw mechanics 7,8 and osteoderms 9 , may indicate different lifestyles for both groups. Since the brain and associated neuroanatomical structures of vertebrates leave perceivable traces, which are possibly ecologically informative, it is worthwhile to thoroughly examine the braincase of nodosaurids in order to compare it to ankylosaurids. Whereas complete braincase material among early-diverging thyreophorans is only known from Scelidosaurus harrisoni 10 , neurocranial material of stegosaurs 11,12 , and ankylosaurs (e.g. 13-15) is more common. The heavily armored skull roofs of the latter likely improved their preservation potential. Struthiosaurus is a European nodosaurid with an estimated body length of up to three metres, known from cranial and postcranial material of Campanian to Maastrichtian age 16-22. As currently accepted, Struthiosaurus comprises three species: S. austriacus from the early Campanian of Austria 16-18 , S. languedocensis from the early Campanian of France 22 , and S. transylvanicus from the Maastrichtian of Romania 23,24. In addition, skeletal remains referred to Struthiosaurus sp. were reported from late Campanian to early Maastrichtian deposits of

Paleoecology and depositional environment of the Tendaguru Beds, Upper Jurassic-Lower Cretaceous of Tanzania, East Africa

Evolutionary Development of the Postcranial and Appendicular Skeleton in Fishes

Cambridge University Press eBooks, Dec 31, 2018

Virtual reconstruction of the skeletal labyrinth of two lamnid sharks (Elasmobranchii, Lamniformes)

Journal of Fish Biology, Nov 22, 2016

The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and... more The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and the shortfin mako shark Isurus oxyrinchus is presented here using high-resolution micro-computed tomography. The results, in comparison with previously published information, suggest relationships between skeletal labyrinth morphology and locomotion mode in chondrichthyans, but also show that further studies are required to establish such connections. Nevertheless, this study adds to the knowledge of the skeletal labyrinth morphology in two apex elasmobranch species.

Topology optimized and 3D printed polymer-bonded permanent magnets for a predefined external field

Journal of Applied Physics, Aug 7, 2017

Topology optimization offers great opportunities to design permanent magnetic systems that have s... more Topology optimization offers great opportunities to design permanent magnetic systems that have specific external field characteristics. Additive manufacturing of polymer bonded magnets with an end-user 3D printer can be used to manufacture permanent magnets with structures that have been difficult or impossible to manufacture previously. This work combines these two powerful methods to design and manufacture permanent magnetic system with specific properties. The topology optimization framework is simple, fast, and accurate. It can be also used for reverse engineering of permanent magnets in order to find the topology from field measurements. Furthermore, a magnetic system that generate a linear external field above the magnet is presented. With a volume constraint the amount of magnetic material can be minimized without losing performance. Simulations and measurements of the printed system show a very good agreement.

3D models related to the publication: Ontogenetic development of the otic region in the new model organism, Leucoraja erinacea (Chondrichthyes; Rajidae)

MorphoMuseuM, Feb 5, 2019

Anatomy, relationships and palaeobiogeographic implications of the first Neogene holomorphic stingray (Myliobatiformes: Dasyatidae) from the early Miocene of Sulawesi, Indonesia, SE Asia

Zoological Journal of the Linnean Society, May 12, 2018

The early Miocene stingray †Trygon vorstmani represented by a single specimen collected from the ... more The early Miocene stingray †Trygon vorstmani represented by a single specimen collected from the fish-bearing limestones of the Tonasa Formation of SW Sulawesi, Indonesia, is redescribed here in detail. This taxon exhibits a unique combination of features that clearly support the presence of a new genus, †Protohimantura gen. nov. and its assignment to the whiptail stingrays (Dasyatidae) of the subfamily Urogymninae. The morphological and phylogenetic affinities of †Protohimantura gen. nov. with the living whiprays suggest a close association of this taxon with tropical shallow-water habitats hypothesized for the SW Sulawesi palaeoenvironment during early Miocene. Moreover, this occurrence, which also represents the first holomorphic stingray specimen from the Neogene, provides new insights into the role of the Indo-Australian Archipelago for the evolutionary history of fishes associated with reefs in the context of the shift of the marine biodiversity hotspot across the globe during the last 50 million years.

Comment on “An early Miocene extinction in pelagic sharks”

Science, Dec 10, 2021

Musculotendinous system of mesopelagic fishes: Stomiiformes (Teleostei)

Journal of Anatomy, Dec 19, 2021

Every night the greatest migration on Earth starts in the deep pelagic oceans where organisms mov... more 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 architecture of the musculotendinous system (MTS) in these fishes have never been examined. In general, the MTS is organized in segmented blocks of specific three-dimensional 'W-shaped' foldings, the myomeres, separated by thin sheets of connective tissue, the myosepta. Within a myoseptum characteristic intermuscular bones or tendons may be developed. Together with the fins, the MTS forms the functional unit for locomotion in fishes. For this study, microdissections of cleared and double stained specimens of seven stomiiform species (Astronesthes sp., Chauliodus sloani, Malacosteus australis, Eustomias simplex, Polymetme sp., Sigmops elongatus, Argyropelecus affinis) were conducted to investigate their MTS. Soft tissue was investigated non-invasively in E. schmidti using a micro-CT scan of one specimen stained with iodine. Additionally, classical histological serial sections were consulted. The investigated stomiiforms are characterized by the absence of anterior cones in the anteriormost myosepta. These cones are developed in myosepta at the level of the dorsal fin and elongate gradually in more posterior myosepta. In all but one investigated stomiiform taxon the horizontal septum is reduced. The amount of connective tissue in the myosepta is very low anteriorly, but increases gradually with body length. Red musculature overlies laterally the white musculature and exhibits strong tendons in each myomere within the muscle bundles dorsal and ventral to the horizontal midline. The amount of red musculature increases immensely towards the caudal fin. The elongated lateral tendons of the posterior body segments attach in a highly complex pattern on the caudal-fin rays, which indicates that the posterior most myosepta are equipped for a multisegmental force transmission towards the caudal fin. This unique anatomical condition might be essential for steady swimming during diel vertical migrations, when prey is rarely available.

First eurhinodelphinid dolphin from the Paratethys reveals a new family of specialised echolocators

Historical Biology, Jun 10, 2022

Evolutionary trends of the conserved neurocranium shape in angel sharks (Squatiniformes, Elasmobranchii)

Scientific Reports, Jul 28, 2020

elasmobranchii (i.e., sharks, skates, and rays) forms one of the most diverse groups of marine pr... more elasmobranchii (i.e., sharks, skates, and rays) forms one of the most diverse groups of marine predators. With a fossil record extending back into the Devonian, several modifications in their body plan illustrate their body shape diversity through time. the angel sharks, whose fossil record dates back to the Late Jurassic, some 160 Ma, have a dorsoventrally flattened body, similar to skates and rays. fossil skeletons of this group show that the overall morphology was well established earlier in its history. By examining the skull shape of well-preserved fossil material compared to extant angel sharks using geometric morphometric methods, within a phylogenetic framework, we were able to determine the conservative skull shape among angel sharks with a high degree of integration. the morphospace occupation of extant angel sharks is rather restricted, with extensive overlap. Most of the differences in skull shape are related to their geographic distribution patterns. We found higher levels of disparity in extinct forms, but lower ones in extant species. Since angel sharks display a highly specialized prey capture behaviour, we suggest that the morphological integration and biogeographic processes are the main drivers of their diversity, which might limit their capacity to display higher disparities since their origin. Elasmobranchs (sharks, skates, and rays) represent a lineage of vertebrates with a fossil record extending over 400 million years 1,2. Throughout their evolutionary history, adaptations of feeding mechanisms, behavioural specializations and ecological distributions are well reflected in their body plan 3,4. Most modern sharks display rather conservative overall body shapes 5 , for most of the pelagic species, and distinguishable from the benthic species 6 , also some specific morphological traits like the neurocranium may vary strongly in shape, as seen in the hammerhead and sawsharks 7-10. Another example of extreme morphology is displayed by angel sharks (Squatiniformes), which are characterized by highly dorsoventrally compressed bodies similar to batomorphs (i.e., skates and rays). This similarity caused controversies in their phylogenetic placement 11,12 , but their systematic position within sharks 13-16 and intra-relationships 17 are well resolved (Fig. 1). All the 22 living valid species of the squatiniforms are included in a single genus, Squatina 18-20. Living angel sharks can be divided into clades that follow a biogeographical pattern explained both by vicariant and dispersion events during the last 20 million years, forming distinct Europe-North African, South African, Asian, Australian, North American and South American clades 17. More recently, it has been suggested that the species from North and South America can be differentiated into eastern and western clades 21. The evolutionary history of angel sharks can be traced back into the Oxfordian (Late Jurassic; 160 Ma), with several specimens initially assigned to Squatina, but later transferred to the genus †Pseudorhina in the family †Pseudorhinidae, ranging from the Oxfordian to the Tithonian 22,23. Extant members of the order Squatiniformes have a fossil record that dates back to the Early Cretaceous 23,24. The body plan of Squatiniformes nevertheless, arose during the Late Jurassic, based on holomorphic fossil specimens, which remains consistent with only few changes to date (Fig. 1B,C). Another feature present in some of the holomorphic fossil species is the

Systematics and Phylogenetic Interrelationships of the Enigmatic Late Jurassic Shark Protospinax annectans Woodward, 1918 with Comments on the Shark–Ray Sister Group Relationship

Diversity

The Late Jurassic elasmobranch Protospinax annectans is often regarded as a key species to our un... more 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 controversial, and a closer relationship between Protospinax and each of the posited superorders (Batomorphii, Squalomorphii, and Galeomorphii) has been proposed over the time. Here we revise this controversial taxon based on new holomorphic specimens from the Late Jurassic Konservat-Lagerstätte of the Solnhofen Archipelago in Bavaria (Germany) and review its skeletal morphology, systematics, and phylogenetic interrelationships. A data matrix with 224 morphological characters was compiled and analyzed under a molecular backbone constraint. Our results indicate a close relationship between Protospinax, angel sharks (Squatiniformes), and saw sharks...

A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships

Diversity

The Late Jurassic-Early Cretaceous (164–100 Ma) represents one of the main transitional periods i... more 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 environments. However, chondrichthyan faunas from this interval have received surprisingly little recognition. The presence of numerous entire skeletons of chondrichthyans preserved in several localities in southern Germany, often referred to as Konservat-Lagerstätten (e.g., Nusplingen and the Solnhofen Archipelago), provides a unique opportunity of to study the taxonomic composition of these assemblages, their ecological distributions and adaptations, and evolutionary histories in detail. However, even after 160 years of study, the current knowledge of southern Germany’s Late Jurassic chondrichthyan diversity remains incomplete. Over the l...

Scanning pulsed laser ablation in liquids: An alternative route to obtaining biocompatible YbFe nanoparticles as multiplatform contrast agents for combined MRI and CT imaging

Ceramics International

Solvothermal synthesis and characterization of ytterbium/iron mixed oxide nanoparticles with potential functionalities for applications as multiplatform contrast agent in medical image techniques

Ceramics International

A solvothermal route to prepare Glutathione capped hybrid ytterbium/iron oxide nanoparticles with... more 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 characteristics of the obtained nanoparticles has been extensively studied. Although all nanoparticles present similar composition, with YbFeO 3 being the majority phase, size and morphology of the as synthetized nanoparticles are highly influenced by the critical temperature and by the over-saturation reached during the solvothermal process. We have demonstrated that glutathione properly functionalizes the hybrid nanoparticles, increasing their colloidal stability and decreasing their cytotoxicity. Additionally, they show good imaging in magnetic resonance and X-ray computerized tomography, thereby indicating promising potential as a dual contrast agent. This work presents, for the first time, glutathione functionalized ytterbium/iron oxide nanoparticles with potential applications in Biomedicine.

Two passeriform birds (Aves: Passeriformes) from the Middle Miocene of Austria

PalZ, 2021

Two newly discovered specimens of passerine birds—an isolated sternum and an associated skeleton—... more 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 avifauna during this period and fill gaps in the paleobiogeography of Miocene passerines. The associated skeleton represents a bird similar in size to the extant Sylvia atricapilla or Erithacus rubecula, and the delicate beak indicates that the bird fed mainly on small invertebrates and possibly also soft fruit. The isolated sternum belonged to a small thrush-sized bird and, considering the fragility of this skeletal element, is one of the best-preserved Miocene passerine sterna in the world.

Using Citizen Science to Detect Rare and Endangered Species: New Records of the Great White Shark Carcharodon Carcharias off the Libyan Coast

Annales. Series historia naturalis : anali za istrske in mediteranske studije = annali di studi istriani e mediterranei = annals of Istrian and Mediterranean studies, 2021

The presence of the great white shark (Carcharodon carcharias) in the Mediterranean Sea is well d... more The presence of the great white shark (Carcharodon carcharias) in the Mediterranean Sea is well documented, but encounters with this species are rare and all assumptions about its spatial and temporal distribution are heavily relying on anecdotal observations. To date, only one record off the Libyan coast has been reported, raising the question if this species is underreported in these waters or simply represents a rare occasional transient. We utilised citizen science-sourced data to document the presence of the great white shark off the Libyan coast, and found six additional records for this species from the period between 2017 and 2020. Our study points out the need for scientific monitoring of this species along the Libyan coast to facilitate the establishment of effective conservation plans to protect this critically endangered species.