16 results on '"Patrick L. Jambura"'
Search Results
2. Updated Checklist of Chondrichthyan Species in Croatia (Central Mediterranean Sea)
- Author
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Pia F. Balàka, Pero Ugarković, Julia Türtscher, Jürgen Kriwet, Simone Niedermüller, Patrik Krstinić, and Patrick L. Jambura
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cartilaginous fishes ,endangered species ,Adriatic Sea ,Red List (IUCN) ,citizen science ,MECO project ,Biology (General) ,QH301-705.5 - Abstract
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 the Adriatic Sea. Here we present a detailed and up-to-date assessment of the species occurring in Croatian waters, as the last checklist of chondrichthyans in Croatian waters was conducted in 2009. Occurrence records from historical data, literature and citizen science information have been compiled in order to present a comprehensive list of species occurrences. We found 54 chondrichthyan species between 1822 and 2022, consisting of a single chimaera, 23 rays and skates, and 30 shark species. Here, four additional species are listed but are considered doubtful. Five species are reported here for the first time for Croatian waters that were not listed in the survey from 2009. Nearly one-third of the species reported here are critically endangered in the entire Mediterranean Sea, based on the IUCN Red List. Additionally, we revisited the Croatian records of the sandtiger shark Carcharias taurus Rafinesque, 1810 and discussed its potential confusion with the smalltooth sandtiger shark Odontaspis ferox (Risso, 1810). Our results thus provide novel insights into the historical and current distribution patterns of chondrichthyan fishes in the Croatian Sea and provide a basis for further research as well as conservation measures.
- Published
- 2023
- Full Text
- View/download PDF
3. A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships
- Author
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Eduardo Villalobos-Segura, Sebastian Stumpf, Julia Türtscher, Patrick L. Jambura, Arnaud Begat, Faviel A. López-Romero, Jan Fischer, and Jürgen Kriwet
- Subjects
Chondrichthyes ,diversity ,biogeography ,Kimmeridgian ,Tithonian ,Late Jurassic ,Biology (General) ,QH301-705.5 - Abstract
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 last 20 years, the systematic study and bulk sampling of southern Germany’s Late Jurassic deposits significantly increased the number of known fossil chondrichthyan genera from the region (32 in the present study). In the present work, the fossil record, and the taxonomic composition of Late Jurassic chondrichthyans from southern Germany are reviewed and compared with several contemporaneous assemblages from other sites in Europe. Our results suggest, inter alia, that the Late Jurassic chondrichthyans displayed extended distributions within Europe. However, it nevertheless also is evident that the taxonomy of Late Jurassic chondrichthyans is in urgent need of revision.
- Published
- 2023
- Full Text
- View/download PDF
4. Systematics and Phylogenetic Interrelationships of the Enigmatic Late Jurassic Shark Protospinax annectans Woodward, 1918 with Comments on the Shark–Ray Sister Group Relationship
- Author
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Patrick L. Jambura, Eduardo Villalobos-Segura, Julia Türtscher, Arnaud Begat, Manuel Andreas Staggl, Sebastian Stumpf, René Kindlimann, Stefanie Klug, Frederic Lacombat, Burkhard Pohl, John G. Maisey, Gavin J. P. Naylor, and Jürgen Kriwet
- Subjects
phylogenetics ,elasmobranch evolution ,calibration fossil ,molecular backbone constraint ,hypnosqualea ,Mesozoic ,Biology (General) ,QH301-705.5 - Abstract
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 (Pristiophoriformes). However, the revision of our morphological data matrix within a molecular framework highlights the lack of morphological characters defining certain groups, especially sharks of the order Squaliformes, hampering the phylogenetic resolution of Protospinax annectans with certainty. Furthermore, the monophyly of modern sharks retrieved by molecular studies is only weakly supported by morphological data, stressing the need for more characters to align morphological and molecular studies in the future.
- Published
- 2023
- Full Text
- View/download PDF
5. Heterodonty and ontogenetic shift dynamics in the dentition of the tiger shark Galeocerdo cuvier (Chondrichthyes, Galeocerdidae)
- Author
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Julia Türtscher, Patrick L. Jambura, Faviel A. López‐Romero, René Kindlimann, Keiichi Sato, Taketeru Tomita, and Jürgen Kriwet
- Subjects
Histology ,Fossils ,Sharks ,Animals ,Dentition ,Skates, Fish ,Cell Biology ,Anatomy ,Molecular Biology ,Phylogeny ,Ecology, Evolution, Behavior and Systematics ,Developmental Biology - Abstract
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, divergence, extinction). Heterodonty (exhibition of different tooth morphologies) occurs in most elasmobranch species and has proven to be one of the main challenges for these analyses. Although numerous shark species are discovered and described every year, detailed descriptions of tooth morphologies and heterodonty patterns are lacking or are only insufficiently known for most species. Here, we use landmark-based 2D geometric morphometrics on teeth of the tiger shark Galeocerdo cuvier to analyse and describe dental heterodonties among four different ontogenetic stages ranging from embryo to adult. Our results reveal rather gradual and subtle ontogenetic shape changes, mostly characterized by increasing size and complexity of the teeth. We furthermore provide the first comprehensive description of embryonic dental morphologies in tiger sharks. Also, tooth shapes of tiger sharks in different ontogenetic stages are re-assessed and depicted in detail. Finally, multiple cases of tooth file reversal are described. This study, therefore, contributes to our knowledge of dental traits across ontogeny in the extant tiger shark G. cuvier and provides a baseline for further morphological and genetic studies on the dental variation in sharks. Therefore, it has the potential to assist elucidating the underlying developmental and evolutionary processes behind the vast dental diversity observed in elasmobranch fishes today and in deep time.
- Published
- 2022
6. Tooth mineralization and histology patterns in extinct and extant snaggletooth sharks, Hemipristis (Carcharhiniformes, Hemigaleidae)-Evolutionary significance or ecological adaptation?
- Author
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Patrick L Jambura, Cathrin Pfaff, Charlie J Underwood, David J Ward, and Jürgen Kriwet
- Subjects
Medicine ,Science - Abstract
Shark jaws exhibit teeth that are arranged into distinct series and files and display great diversities in shapes and structures, which not only is related to their function (grasping, cutting, crushing) during feeding, but also bear a strong phylogenetic signal. So far, most research on the relationship between shark teeth and feeding ecology and systematics focused on the external tooth morphology only. Although the tooth histology of sharks has been examined since the early 19th century, its functional and systematic implications are still ambiguous. Shark teeth normally consist of either a porous, cellular dentine, osteodentine (in lamniform sharks and some batoids) or a dense layer of orthodentine (known from different sharks). Sharks of the order Carcharhiniformes, comprising ca. 60% of all extant shark species, are known to have orthodont teeth, with a single exception-the snaggletooth shark, Hemipristis elongata. High resolution micro-CT images of jaws and teeth from selected carcharhiniform sharks (including extant and fossil snaggletooth sharks) and tooth sections of teeth of Hemipristis, other carcharhiniform and lamniform sharks, have revealed that (1) Hemipristis is indeed the only carcharhiniform shark filling its pulp cavity with osteodentine in addition to orthodentine, (2) the tooth histology of Hemipristis elongata differs from the osteodont histotype, which evolved in lamniform sharks and conversely represents a modified orthodonty, and (3) this modified orthodonty was already present in extinct Hemipristis species but the mineralization sequence has changed over time. Our results clearly show the presence of a third tooth histotype-the pseudoosteodont histotype, which is present in Hemipristis. The unique tooth histology of lamniform sharks might provide a phylogenetic signal for this group, but more research is necessary to understand the phylogenetic importance of tooth histology in sharks in general.
- Published
- 2018
- Full Text
- View/download PDF
7. Observations of juvenile sandbar sharks Carcharhinus plumbeus (Nardo, 1827) around the Bojana River delta (Southern Adriatic Sea)
- Author
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ILIJA ĆETKOVIĆ, PATRICK L. JAMBURA, ANA PEŠIĆ, ZDRAVKO IKICA, and ALEKSANDAR JOKSIMOVIĆ
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Montenegro ,Environmental Engineering ,Adriatic Sea ,Shark Nursery Area ,Estuary ,Aquatic Science ,Oceanography ,Ecology, Evolution, Behavior and Systematics ,elasmobranchs - Abstract
The sandbar shark (Carcharhinus plumbeus) is considered rare in the Adriatic Sea and the majority of records originate from the northern Adriatic, where a nursery area for this species close to the Po delta system has been repeatedly proposed. This study provides 5 new records and analyses the previously published records of sandbar sharks recorded around the delta of the River Bojana (in Montenegro, in the south-eastern Adriatic). The River Bojana located on the border between Montenegro and Albania, is the second largest river flowing into the Adriatic Sea, where it forms a highly productive ecosystem already known as a local hotspot for smooth-hound sharks (Mustelus spp.). New records of sandbar sharks have emerged as a result of citizen science (a social media survey) and direct reports from fishermen. The total length of C. plumbeus juveniles ranged from approximately 800 mm to 1100 mm, and most (n=5) were caught by set gillnets. The data presented here show that juveniles are consistently present around the estuary and indicate the importance of this fragile estuarine ecosystem for sandbar sharks. Additionally, this study also provides morphometric data collected from a single individual.
- Published
- 2022
8. Evolution, diversity, and disparity of the tiger shark lineage Galeocerdo in deep time
- Author
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Patrick L. Jambura, René Kindlimann, Faviel A. López-Romero, David Ward, Jürgen Kriwet, and Julia Türtscher
- Subjects
0106 biological sciences ,0303 health sciences ,food.ingredient ,Lineage (genetic) ,Ecology ,biology ,media_common.quotation_subject ,Paleontology ,biology.organism_classification ,Galeocerdo ,010603 evolutionary biology ,01 natural sciences ,Article ,03 medical and health sciences ,food ,stomatognathic system ,Evolutionary biology ,General Agricultural and Biological Sciences ,human activities ,Ecology, Evolution, Behavior and Systematics ,Tiger shark ,Deep time ,030304 developmental biology ,Diversity (politics) ,media_common - Abstract
Sharks have a long and rich fossil record that consists predominantly of isolated teeth due to the poorly mineralized cartilaginous skeleton. Tiger sharks (Galeocerdo), which represent apex predators in modern oceans, have a known fossil record extending back into the early Eocene (ca. 56 Ma) and comprise 22 recognized extinct and one extant species to date. However, many of the fossil species remain dubious, resulting in a still unresolved evolutionary history of the tiger shark genus. Here, we present a revision of the fossil record of Galeocerdo by examining the morphological diversity and disparity of teeth in deep time. We use landmark-based geometric morphometrics to quantify tooth shapes and qualitative morphological characters for species discrimination. Employing this combined approach on fossil and extant tiger shark teeth, our results only support six species to represent valid taxa. Furthermore, the disparity analysis revealed that diversity and disparity are not implicitly correlated and that Galeocerdo retained a relatively high dental disparity since the Miocene despite its decrease from four to one species. With this study, we demonstrate that the combined approach of quantitative geometric morphometric techniques and qualitative morphological comparisons on isolated shark teeth provides a useful tool to distinguish between species with highly similar tooth morphologies.
- Published
- 2021
9. Using historical and citizen science data to improve knowledge about the occurrence of the elusive sandbar shark
- Author
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Patrick L, Jambura, Ilija, Ćetković, Jürgen, Kriwet, and Julia, Türtscher
- Subjects
Article - Abstract
The Mediterranean Sea is an extinction hotspot for sharks, skates, and rays, with at least half of all species being threatened. The sandbar shark Carcharhinus plumbeus is among the most threatened species and is declared endangered (EN) in the Mediterranean according to the IUCN Red List of Threatened Species. The Adriatic Sea was previously proposed to be an important nursery area for this species based on sporadic sightings of neonates and juveniles. However, this species is generally considered to be rare in this region, and reports of its presence are scarce. Here, we present new records for the sandbar shark in the Adriatic Sea and review spatial and temporal data accumulated from literature, museum specimens, and citizen science initiatives in an attempt to assess the distribution and seasonality of this species. The majority of the records were from neonate and juvenile sandbar sharks, and three hotspots for their occurrence could be identified: (1) the Emilia-Romagna region, (2) the Veneto region, and (3) the Gulf of Trieste. Our data indicate a high concentration of sandbar sharks around the delta of the Po river, emphasising the need for scientific surveys in this confined area in order to confirm a possible nursery ground. Data collected by citizen science initiatives reveal that this species is still present in the Adriatic Sea and might be more abundant than previously thought, underlining the potential of citizen science as a valuable tool to monitor the distribution of rare and endangered species.
- Published
- 2021
10. Sightings of a White Shark (Carcharodon carcharias) with a Significantly Deformed Pectoral Fin off the coast of Southern California
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Patrick L. Jambura and Phillip C. Sternes
- Subjects
Fishery ,food.ingredient ,food ,White (horse) ,biology ,Fish fin ,General Medicine ,General Chemistry ,biology.organism_classification ,Carcharodon ,Carcharias - Published
- 2021
11. Skeletal remains of the oldest known pseudocoracid shark Pseudocorax kindlimanni sp. nov. (Chondrichthyes, Lamniformes) from the Late Cretaceous of Lebanon
- Author
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Jürgen Kriwet, Patrick L. Jambura, and Sebastian Stumpf
- Subjects
010506 paleontology ,food.ingredient ,Heterodont ,Zoology ,010502 geochemistry & geophysics ,01 natural sciences ,Article ,Pseudocorax ,food ,Elasmobranchii ,stomatognathic system ,Chondrichthyes ,Pseudocoracidae ,0105 earth and related environmental sciences ,biology ,Dentition ,Haqel ,Paleontology ,biology.organism_classification ,Cretaceous ,Heterodonty ,Lamniformes ,Cenomanian ,human activities ,Mesozoic - Abstract
A new fossil mackerel shark, Pseudocorax kindlimanni sp. nov. (Lamniformes, Pseudocoracidae), is described from the Cenomanian Konservat-Lagerstatte of Haqel, Lebanon. The new species is based on the most complete fossil of this group to date, which comprises an associated tooth set of 70 teeth, six articulated vertebral centra, numerous placoid scales and pieces of unidentifiable mineralized cartilage. The dentition of P. kindlimanni sp. nov. is marked by a high degree of monognathic heterodonty but does not exhibit the characteristic “lamnoid tooth pattern” known from other macrophagous lamniform sharks. In addition, P. kindlimanni sp. nov. shows differences in tooth microstructure and vertebral centrum morphology compared to other lamniform sharks. These variations, however, are also known from other members of this order and do not warrant the assignment of Pseudocorax outside the lamniform sharks. The new fossil is the oldest known pseudocoracid shark and pushes the origin of this group back into the Cenomanian, a time when lamniform sharks underwent a major diversification. This radiation resulted not only in high species diversity, but also in the development of a diverse array of morphological traits and adaptation to different ecological niches. Pseudocorax kindlimanni sp. nov. was a small, active predator capable of fast swimming, and it occupied the lower trophic levels of the marine food web in the Late Cretaceous.
- Published
- 2021
12. Using historical and citizen science data to improve knowledge about the occurrence of the elusive sandbar shark Carcharhinus plumbeus (Chondrichthyes – Carcharhinidae) in the Adriatic Sea
- Author
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Ilija Ćetković, Patrick L. Jambura, Jürgen Kriwet, and Julia Türtscher
- Subjects
Environmental Engineering ,Sandbar shark ,biology ,Endangered species ,Neonates ,Aquatic Science ,Oceanography ,biology.organism_classification ,Chondrichthyes ,Parturition ,Fishery ,Mediterranean sea ,Geography ,Elasmobranchii ,Carcharhinus ,Threatened species ,Mediterranean Sea ,IUCN Red List ,Estuaries ,Ecology, Evolution, Behavior and Systematics ,Migration - Abstract
The Mediterranean Sea is an extinction hotspot for sharks, skates, and rays, with at least half of all species being threatened. The sandbar shark Carcharhinus plumbeus is among the most threatened species and is declared endangered (EN) in the Mediterranean according to the IUCN Red List of Threatened Species. The Adriatic Sea was previously proposed to be an important nursery area for this species based on sporadic sightings of neonates and juveniles. However, this species is generally considered to be rare in this region, and reports of its presence are scarce. Here, we present new records for the sandbar shark in the Adriatic Sea and review spatial and temporal data accumulated from literature, museum specimens, and citizen science initiatives in an attempt to assess the distribution and seasonality of this species. The majority of the records were from neonate and juvenile sandbar sharks, and three hotspots for their occurrence could be identified: (1) the Emilia-Romagna region, (2) the Veneto region, and (3) the Gulf of Trieste. Our data indicate a high concentration of sandbar sharks around the delta of the Po river, emphasising the need for scientific surveys in this confined area in order to confirm a possible nursery ground. Data collected by citizen science initiatives reveal that this species is still present in the Adriatic Sea and might be more abundant than previously thought, underlining the potential of citizen science as a valuable tool to monitor the distribution of rare and endangered species.
- Published
- 2021
13. Deadly interaction between a swordfish Xiphias gladius and a bigeye thresher shark Alopias superciliosus
- Author
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Sara A. A. Al Mabruk, Jürgen Kriwet, Julia Türtscher, and Patrick L. Jambura
- Subjects
Fishery ,biology ,Bigeye thresher shark ,Alopias superciliosus ,Swordfish ,Gladius ,biology.organism_classification ,Ecology, Evolution, Behavior and Systematics ,Article - Published
- 2020
14. Evolutionary trajectories of tooth histology patterns in modern sharks (Chondrichthyes, Elasmobranchii)
- Author
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Jürgen Kriwet, Patrick L. Jambura, René Kindlimann, Cathrin Pfaff, Julia Türtscher, Gerhard W. Weber, Sebastian Stumpf, and Brian D. Metscher
- Subjects
0301 basic medicine ,Histology ,tooth histology ,dentition ,micro‐computed tomography ,03 medical and health sciences ,0302 clinical medicine ,Tooth mineralization ,Extant taxon ,Elasmobranchii ,stomatognathic system ,histotype ,Animals ,Pristiophorus ,micro-computed tomography ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics ,Phylogeny ,teeth ,biology ,Cell Biology ,Anatomy ,Original Articles ,X-Ray Microtomography ,biology.organism_classification ,Chondrichthyes ,Biological Evolution ,stomatognathic diseases ,030104 developmental biology ,Posterior teeth ,Sharks ,Pulp (tooth) ,Original Article ,Tooth ,030217 neurology & neurosurgery ,Developmental Biology - Abstract
During their evolutionary history, modern sharks developed different tooth mineralization patterns that resulted in very distinct histological patterns of the tooth crown (histotypes). To date, three different tooth histotypes have been distinguished: (i) orthodont teeth, which have a central hollow pulp cavity in the crown, encapsulated by a prominent layer of dentine (orthodentine); (ii) pseudoosteodont teeth, which have their pulp cavities secondarily replaced by a dentinal core of porous dentine (osteodentine), encased by orthodentine; and (iii) osteodont teeth, which lack orthodentine and the whole tooth crown of which consists of osteodentine. The aim of the present study was to trace evolutionary trends of tooth mineralization patterns in modern sharks and to find evidence for the presence of phylogenetic or functional signals. High resolution micro‐computed tomography images were generated for the teeth of members of all nine extant shark orders and the putative stem group †Synechodontiformes, represented here by three taxa, to examine the tooth histology non‐destructively. Pseudoosteodonty is the predominant state among modern sharks and represents unambiguously the plesiomorphic condition. Orthodonty evolved several times independently in modern sharks, while the osteodont tooth histotype is only developed in lamniform sharks. The two shark orders Heterodontiformes and Pristiophoriformes showed highly modified tooth histologies, with Pristiophorus exhibiting a histology only known from batomorphs (i.e. rays and skates), and Heterodontus showing a histological difference between anterior and posterior teeth, indicating a link between its tooth morphology, histology and durophagous lifestyle. The tooth histotype concept has proven to be a useful tool to reflect links between histology, function and its taxonomic value for distinct taxa; however, a high degree of variation, especially in the pseudoosteodont tooth histotype, demonstrates that the current histotype concept is too simplistic to fully resolve these relationships. The vascularization pattern of the dentine might offer new future research pathways for better understanding functional and phylogenetic signals in the tooth histology of modern sharks., Using micro‐computed tomography techniques, we examined the tooth mineralization in modern shark clades (Elasmobranchii, Chondrichthyes). The inclusion of fossil taxa and computing ancestral states allowed us to trace back the development of different mineralization patterns in deep time.
- Published
- 2019
15. Tooth mineralization and histology patterns in extinct and extant snaggletooth sharks, Hemipristis (Carcharhiniformes, Hemigaleidae)—Evolutionary significance or ecological adaptation?
- Author
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Jürgen Kriwet, Patrick L. Jambura, Charlie J. Underwood, Cathrin Pfaff, and David J. Ward
- Subjects
0106 biological sciences ,Teeth ,Physiology ,Digestive Physiology ,lcsh:Medicine ,01 natural sciences ,Hemipristis ,Extant taxon ,Medicine and Health Sciences ,lcsh:Science ,Chondrichthyes ,Phylogeny ,Data Management ,Multidisciplinary ,biology ,Dentition ,Fossils ,Histological Techniques ,Eukaryota ,Adaptation, Physiological ,Biological Evolution ,Phylogenetics ,Connective Tissue ,Vertebrates ,Anatomy ,Research Article ,Systematics ,010506 paleontology ,Computer and Information Sciences ,Histology ,Zoology ,chemical and pharmacologic phenomena ,010603 evolutionary biology ,Tooth mineralization ,stomatognathic system ,Carcharhiniformes ,Animals ,Evolutionary Systematics ,0105 earth and related environmental sciences ,Taxonomy ,Evolutionary Biology ,lcsh:R ,Organisms ,Biology and Life Sciences ,X-Ray Microtomography ,biology.organism_classification ,Hemigaleidae ,stomatognathic diseases ,Fish ,Biological Tissue ,Cartilage ,es ,Jaw ,Dentin ,Sharks ,lcsh:Q ,Adaptation ,Tomography, X-Ray Computed ,Digestive System ,Head ,Tooth ,human activities ,Tooth Calcification ,Elasmobranchii - Abstract
Shark jaws exhibit teeth that are arranged into distinct series and files and display great diversities in shapes and structures, which not only is related to their function (grasping, cutting, crushing) during feeding, but also bear a strong phylogenetic signal. So far, most research on the relationship between shark teeth and feeding ecology and systematics focused on the external tooth morphology only. Although the tooth histology of sharks has been examined since the early 19th century, its functional and systematic implications are still ambiguous. Shark teeth normally consist of either a porous, cellular dentine, osteodentine (in lamniform sharks and some batoids) or a dense layer of orthodentine (known from different sharks). Sharks of the order Carcharhiniformes, comprising ca. 60% of all extant shark species, are known to have orthodont teeth, with a single exception-the snaggletooth shark, Hemipristis elongata. High resolution micro-CT images of jaws and teeth from selected carcharhiniform sharks (including extant and fossil snaggletooth sharks) and tooth sections of teeth of Hemipristis, other carcharhiniform and lamniform sharks, have revealed that (1) Hemipristis is indeed the only carcharhiniform shark filling its pulp cavity with osteodentine in addition to orthodentine, (2) the tooth histology of Hemipristis elongata differs from the osteodont histotype, which evolved in lamniform sharks and conversely represents a modified orthodonty, and (3) this modified orthodonty was already present in extinct Hemipristis species but the mineralization sequence has changed over time. Our results clearly show the presence of a third tooth histotype-the pseudoosteodont histotype, which is present in Hemipristis. The unique tooth histology of lamniform sharks might provide a phylogenetic signal for this group, but more research is necessary to understand the phylogenetic importance of tooth histology in sharks in general.
- Published
- 2018
16. Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the Upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks.
- Author
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Patrick L Jambura and Jürgen Kriwet
- Subjects
Medicine ,Science - Abstract
Due to their cartilaginous endoskeleton and the continuous tooth replacement, the chondrichthyan fossil record predominantly consists of isolated teeth, which offer diagnostic features for taxonomic identifications, but only provide very limited information of an organism's life history. In contrast, the calcified vertebral centra of elasmobranchs (sharks, skates and rays) yield important information about ecological and biological traits that can be utilized for constructing age-structured population dynamic models of extant species and palaeoecological reconstructions of such aspects in extinct groups. Here, we describe two large shark vertebrae from the Santonian (Upper Cretaceous) of Spain, which show a unique combination of characters (asterospondylic calcification pattern, with concentric lamellae and numerous parallel bands that are oriented perpendicular) that is only known from ptychodontid sharks, a distinct, extinct group of giant durophagous sharks of the Cretaceous era. Based on linear regression models for large extant sharks a total length between 430 and 707cm was estimated for the examined specimen. Our results indicate that ptychodontid sharks were large viviparous animals, with slow growth rates, matured very late and, therefore, show typical traits for K-selected species. These traits combined with a highly specialized feeding ecology might have played a crucial role for the success but also, eventually, extinction of this group.
- Published
- 2020
- Full Text
- View/download PDF
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