Shark Fauna Research Articles

A diverse assemblage of Ptychodus species (Elasmobranchii: Ptychodontidae) from the Upper Cretaceous of Ukraine, with comments on possible diversification drivers during the Cenomanian

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 margin of the Ukrainian Massif. In addition, P. latissimus from the Turonian of Ukraine is reported here for the first time. The revision of the Ukrainian record of Ptychodus revealed that most specimens described here are the oldest so far known from this part of the European Peri-Tethys. Moreover, the present study highlights the co-occurrence of cuspidate and un-cuspidate Ptychodus and a variety of shelled macroinvertebrates, which inhabited coastal and offshore areas of the European epicontinental seas during the Late Cretaceous. The availability of different prey items is proposed here as one of the possible drivers, in addition to abiotic environmental factors, for the diversification of shark tooth morphologies, and possible trophic partitioning between cuspidate and un-cuspidate species of the genus Ptychodus.

New data about the shark fauna of the Brejo Santo formation, Late Jurassic of the Araripe Basin, Northeastern Brazil

The Late Jurassic fauna of the Araripe Basin is represented by chondrichthyans and osteichthyans (Actinopterygii and Sarcopterygii). At the present study, we describe new records of hybodontid shark from the Brejo Santo Formation (Upper Jurassic – Tithonian) and characterize their paleohistology. They are represented by a complete cephalic spine of Planohybodus sp., which indicates sexual dimorphism, being present only in male sharks; as well as by a dorsal spine, which is the most complete found so far for this formation. Microstructural analyzes were performed in the dorsal spine, indicating this specimen as a juvenile, early sub-adult individual, approximately one year old.

Quaternary fossil shark (Neoselachii: Galeomorphii and Squalomorphii) diversity from southern Brazil

Sharks are cartilaginous fish that appeared 245 million years ago and became a highly diversified group, occupying several niches successfully. On the coast of Rio Grande do Sul, Brazil, shark fossils are commonly found ex situ associated with accumulations of biodetrital gravels along the current beach line. The present study consisted of a faunistic and paleobiologic survey of sharks from the Quaternary in the southern region of the Rio Grande do Sul Coastal Plain (RSCP), southern Brazil. Based on taxonomy, about 3611 fossilized shark teeth collected on the beaches of Cassino and Hermenegildo were analyzed. A total of 13 taxa were identified, among them cf. Carcharhinus brachyurus, cf. Carcharhinus leucas, cf. Carcharhinus longimanus, Carcharhinus sp., Carcharias taurus, Carcharodon carcharias, Galeocerdo cuvier, Galeorhinus galeus, Isurus oxyrinchus, Notorynchus cepedianus, Rhizoprionodon sp., Sphyrna sp. and Squatina sp. Besides the already known species, here we also report the presence of Carcharhinus brachyurus, Carcharhinus longimanus, Galeorhinus galeus, Rhizoprionodon sp. and Squatina sp. as the first fossil record in the Pleistocene of Brazil for these taxa in the region. The study showed that the fossil taxa identified are similar to those extant taxa that inhabit the coast of Rio Grande do Sul. Evidence of climate oscillations that occurred during the Quaternary can be seen throughout the presence of the species Carcharhinus leucas, Carcharodon carcharias, and Galeocerdo cuvier (when compared to the composition of the modern shark fauna). Since, currently, the occurrence of these species are given as rare in the region. The present study expanded the occurrence of fossil species on the coast of the state of Rio Grande do Sul and confirmed the occurrence of populations of Carcharias taurus, Carcharodon carcharias, Carcharhinus sp., and Carcharhinus leucas during the Quaternary.

Community-Based Whale Sharks Conservation to Strengthen Ma-rine Tourism Management in Sumbawa

Sumbawa is famous for its marine tourism, apart from the beauty of its beaches, Sumbawa also has marine fauna that attracts the attention of tourists, namely whale sharks. It is recorded that there are around 99 species of Whale Sharks located in Saleh Bay, Sumbawa. Thus, making Saleh Bay the location with the second largest whale shark population in Indonesia and UNESCO designated Saleh Bay as part of the SAMOTA biosphere reserve. Currently, whale sharks have protected fauna according to the decree of the Minister of Marine Affairs and Fisheries No. 18 of 2013. This is due to the pollution of whale shark habitats by pollutants including garbage and microplastics. In addition, the Overexploitation of whale sharks is some of the causes of the significant decline in whale shark populations. Marine ecotourism activities in the form of exhibiting Whale Sharks to tourists can be an alternative way of sustainable use because it has minimal impact on individual Whale Sharks, in addition, marine ecotourism activities can also provide economic benefits to the Sumbawa community and regional development including supporting efforts to protect and preserve the whale shark fauna. The Study "Community-Based Whale Shark Conservation to Strengthen Marine Tourism Management in Sumbawa “aims to present a blue economy model for coastal communities in Sumbawa and increase community participation in conservation activities, as well as improve the welfare of coastal communities in Sumbawa.

South Brazil pre-colonial sharks: Insights into biodiversity and species distributions.

South Brazil's archaeological coastal sites (shellmounds and middens) show a diverse collection of shark faunal remains, some of which belong to species considered rare nowadays for the region. However, shark archaeological remains identification in this region has been historically insufficient and prone to mistakes. This study identified shark fauna and estimated body size (total length) present at two archaeological sites: Rio do Meio (1220-977 Cal B.P.) and Enseada II (4286-3783 Cal B.P.), located in Santa Catarina, South of Brazil. Here, 1600 teeth and 3588 vertebrae were analysed and identified. We showed higher historical shark species richness than previously reported for South Brazil in historical and archaeological studies. In total, we identified at least 15 species of sharks (11 species and four identifications at the genus level). The presence of juvenile shark remains adds to the evidence of pre-colonial fishing impacts in local shark populations. The consistent recovery of adults and juveniles of Carcharias taurus points to a possible nursery area on the mouth of Babitonga bay. The high teeth frequency (43%) of C. taurus suggests the South Brazil coastline was once home to abundant populations of this critically endangered species. Furthermore, we discuss the presence of rare species nowadays, suggesting a possible historical residency for adult populations of Carcharodon carcharias based on the presence of juveniles and young-of-the-year on archaeological sites. The occurrence of Negaprion brevirostris, a tropical species, might have been facilitated by ocean current variations.

An unusual shark assemblage from the Ladinian–Carnian interval of South China

AbstractA detailed taxonomic study of a diverse chondrichthyan fauna from the Ladinian–Carnian (Middle–Late Triassic) interval at Nimaigu locality in Guizhou Province, South China is presented. Six taxa are described, two of which are assigned to Elasmobranchii incertae sedis (aff. Rosaodus sp., Rosaodus xingyiensis gen. et sp. nov.) and three to the Euselachii (Euselachii gen. et sp. indet., Favusodus orientalis gen. et sp. nov., Keichouodus nimaiguensis gen. et sp. nov.), while the last one represents a possible Holocephali (aff. Arctacanthus sp.). Their stratigraphic distribution is documented on a bed‐by‐bed basis. This fauna is unusual because it is dominated by sharks with a cladodont‐like dentition (which were barely known after the end‐Permian mass extinction), and because it is almost devoid of durophagous euselachians, which makes it different from all other contemporaneous shark faunas worldwide. Transitional features are documented between ‘cladodont’ teeth and those of neoselachian sharks, which provide new insights into the replacement pattern of ancient sharks by modern ones.

A closer look at the bycatch of medium‐sized and large sharks in the northern Catalan coast (north‐western Mediterranean Sea): Evidence of an ongoing decline?

Abstract Historically, the Mediterranean Sea supported a rich shark fauna. Presently, however, populations of most shark species have significantly declined, largely due to intense fishing pressure. Interviews with crew members of bottom trawlers, drifting longliners and bottom longliners operating off the Costa Brava (Catalonia, NE Spain) were conducted between October 2016 and July 2017 in order to gather information on the current bycatch rate of several shark species. Interviews covered 41.2% of the fleet and respondents were asked for the bycatch of selected shark species—Alopias vulpinus, Cetorhinus maximus, Galeorhinus galeus, Hexanchus griseus, Isurus oxyrinchus, Mustelus spp., Prionace glauca, and Squalus acanthias—in two distinct time periods. Bottom trawlers captured the highest diversity of species (eight) followed by bottom longliners (seven), and drifting longliners (three). Most respondents (89.7%) declared having captured at least one shark from 2006 to 2016 but only 56.4% declared having captured at least one shark from 2016 to 2017. From 2016 to 2017, the whole fleet captured 89 specimens of H. griseus (95% confidence interval (CI) = 145, 34), 14 of G. galeus (95% CI = 30, 0), 3 of A. vulpinus (95% CI = 8, 0), 3 of I. oxyrinchus (95% CI = 8, 0), 3 of C. maximus (95% CI = 6, 0), and no Mustelus spp. The total bycatch of P. glauca and S. acanthias was uncertain due to extremely loose confidence intervals. A significant decline was perceived by fishermen in the bycatch of C. maximus and S. acanthias, whereas the bycatch of H. griseus was considered to have remained stable. This study suggests a dramatic reduction in the abundance of most of the medium‐sized and large sharks of the Costa Brava and the likely disappearance of Mustelus spp. from the area. Only H. griseus, S. acanthias, and P. glauca are still being bycaught frequently.

A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages

ABSTRACT This article describes a rich and diversified elasmobranch fauna collected from the Upper Campanian Northumberland Formation, a part of the Nanaimo Group, exposed on Hornby Island, British Columbia, Canada. This fauna consists of 30 species belonging to 26 genera and is characterised by a large number of new elasmobranch taxa (17 species, 7 genera and 2 families); all these principally belong to the usual deep-water squalomorphs (e.g. Chlamydoselachiformes, Hexanchiformes, Echinorhiniformes, Squaliformes, Pristiophoriformes). This elasmobranch association displays two striking features: no batoid taxa have been found despite the extremely fine process of collection, and it is mainly composed of taxa living in a deep-water environment. The identified species have a large panel of body size estimated between about 50 cm (Eoetmopterus?) up to probably 3 to 4 metres long (eg. Xampylodon nov. gen., Carcharias) and maybe more for Dykeius nov. gen. The Hornby Island fauna represents by far the most diverse deep-water assemblage ever described in the Late Cretaceous, particularly rich in hexanchiforms and squaliforms, providing new insights into the history of the deep-water settlement of this period.

Features and Paleoecological Significance of the Shark Fauna from the Upper Cretaceous Hinoshima Formation, Himenoura Group, Southwest Japan

The shark fauna of the Upper Cretaceous Hinoshima Formation (Santonian: 86.3–83.6 Ma) of the Himenoura Group (Kamiamakusa, Kumamoto Prefecture, Kyushu, Japan) was investigated based on fossil shark teeth found at five localities: Himedo Park, Kugushima, Wadanohana, Higashiura, and Kotorigoe. A detailed geological survey and taxonomic analysis was undertaken, and the habitat, depositional environment, and associated mollusks of each locality were considered in the context of previous studies. Twenty-three species, 15 genera, 11 families, and 6 orders of fossil sharks are recognized from the localities. This assemblage is more diverse than has previously been reported for Japan, and Lamniformes and Hexanchiformes were abundant. Three categories of shark fauna are recognized: a coastal region (Himedo Park; probably a breeding site), the coast to the open sea (Kugushima and Wadanohana), and bottom-dwelling or near-seafloor fauna (Kugushima, Wadanohana, Higashiura, and Kotorigoe). The shark fauna of the Hinoshima Formation is similar to that of the Yezo and Futaba groups, and also to faunas from Angola, Australia, and Antarctica. However, based on the composition of taxa, the fauna differs from that of the Upper Cretaceous shark fauna of the Western Interior Seaway and Europe. The Upper Cretaceous shark fauna of Japan, including the Hinoshima Formation, contained active pelagic (Squalicorax and Cretoxyrhina mantelli) and bentho-pelagic (e.g. Notidanodon, Chlamydoselachus, Sphenodus) predators. These taxa probably coexisted, as they occupied different ecological niches. The characteristics of the Late Cretaceous shark fauna in Japan are similar to those of the contemporaneous Southern Hemisphere fauna (e.g. Angola, Australia, and Antarctica). This shows that the characteristic shark fauna (e.g. Notidanodon, Chlamydoselachus, Sphenodus) of the Southern Hemisphere had spread to the middle latitudes of the Northern Hemisphere by the Late Cretaceous.

PALEOPROSTŘEDÍ VE SPODNÍM BADENU NA SEVERNÍM OKRAJI BRNA (DIVIŠOVA ČTVRŤ)

Lower Badenian sediments were studied on the locality Hvozdíkova at the Diviš district, Brno. There were interpreted 4 lithofacies of Neogene (Lower Badenian) sediments (lithofacies M1, M2, Sl, and SGl). Occurrence of basal Lower Badenian clastics is connected with existence of coarse-grained delta (foreset). Overlying pelites document pelagic sedimentation of open sea. Garnet dominates in assemblage of heavy translucent minerals.Rich assemblages of foraminifers, molluscs, spines of echinoids, ostracods and shark fauna were discovered in sediments. Diversified assemblages are dominated by plankton specimens. Species Orbulina suturalis Brön., Praeorbulina glomerosa circularis (Blow) and Globigerinoides bisphericus Todd. indicate the Lower Badenian age.From the point of view of the shark fauna diversity the locality Hvozdíkova is unique; shark fauna is very rare in Lower Badenian clays, and the genera of Squaliolus and Paraetmopterus are identified for the first time. Oysters – especially species Neopycnodonte navicularis (Brocchi) – dominate in Lower Badenian sediments. Small gastropods (for example Cancellaria sp., ?Tornus sp., Rissoa sp., Alvania sp.) probably represent fossils reworked from shallow littoral area.

A new assemblage of freshwater sharks (Chondrichthyes: Elasmobranchii) from the Upper Triassic of India

This study reports the first occurrence of a varied xenacanth assemblage from the Upper Triassic Tiki Formation of India, based on multiple well-preserved isolated teeth. Based on distinct tooth morphology, two species of the genus Mooreodontus are described: M. indicus and a new species, M. jaini. The new species is diagnosed based on a tricuspid crown containing two stout, slightly diverging lateral cusps pointing in the same direction, a high median cusp, crown-base angle almost at 90°, large, rounded, apical button with several foramina and multiple, 8–9 coarse vertical cristae on all the cusps. Dental anomaly in the form of a partial quadri-cuspidate xenacanthid tooth is present in the collection. Another group of xenacanthid teeth have bicuspid crowns with two upright, asymmetric cusps, where the mesial cusp is thicker than the distal one, and consistently lack a median cusp. Such distinct bicuspid tooth morphology is usually present in Palaeozoic forms and is reported for the first time from the Late Triassic. It is considered to belong to a new taxon, Tikiodontus asymmetricus nov. gen., nov. sp., of indeterminate family. Distinctive tooth histology also differentiates the two Indian genera Mooreodontus and Tikiodontus nov. gen. from other xenacanthid taxa. In addition, the Tiki assemblage has yielded multiple chondrichthyan dermal denticles, which may be subdivided into two morphotypes based on their robustness and presence/absence of linear ridges on the fused cusps. India holds a unique position in terms of its Late Triassic freshwater shark fauna, as it exhibits distinct Laurasian affinities. These freshwater sharks had restricted occurrences in other parts of the Gondwanan landmass.

First report on a diverse Neogene cartilaginous fish fauna from Borneo (Ambug Hill, Brunei Darussalam)

The highest biodiversity of marine fishes occurs in South-east Asia in the Indo-Australian Archipelago (IAA). However, the fossil record of fishes is very sparse and extremely incomplete in the IAA. Here we present a diverse fossil cartilaginous fish fauna from Borneo, found in late Miocene sediments in Brunei Darussalam. This fauna provides the first insight into the types of fishes that existed in the IAA region about 6.5–8 million years ago. The chondrichthyan remains belong to 24 selachian and batoid taxa. The shark fauna is dominated by Carcharhiniformes, comprising three families with at least 12 taxa, most related to modern species: Hemigaleidae (one species), Carcharhinidae (nine) and Sphyrnidae (two). In addition, the teeth of one Lamniformes shark, the extinct giant macro-predator Otodus (Megaselachus) megalodon, are present in the fauna. The batoids are dominated by Myliobatiformes from the following families: Dasyatidae (three species), Aetobatidae (one), Myliobatidae (three), Rhinopteridae (one), while three taxa of the order Rhinopristiformes were also recovered: Pristidae (one species), and Rhinidae (two). Such diversity of fossil cartilaginous fish has never before been reported from the tropical region of South-east Asia. The dominance of the carcharhinid sharks and small rays suggests a shallow marine, coastal palaeoenvironment. The presence of the freshwater shark genus Glyphis indicates a nearby fluvial influence. Some species of the ray genera, such as Himantura or Pastinachus, have also been reported from estuaries and fresh water. The lack of some generally common Neogene taxa, such as Odontaspididae, Lamnidae and Alopidae, may be linked to such local factors and the coastal shallow-water environment.

A Serravallian (Middle Miocene) shark fauna from Southeastern Spain and its palaeoenvironment significance

The study of a new Serravallian (Middle Miocene) locality from the Southeastern Spain has yielded a shark assemblage characterized by microremains of at least seven taxa (Deania calcea, †Isistius triangulus, †Squaliolus cf. S. schaubi, †Paraetmopterus sp., Pristiophorus sp., Scyliorhinus sp. and a cf. Squaliformes indet) of three different orders (Squaliformes, Pristiophoriformes and Carcharhiniformes). In addition, associated macroremains have also been found, including teeth of †Cosmopolitodus hastalis, Isurus sp., Hemipristis serra, Odontaspis sp., Carcharhinus spp. and †Otodus (Megaselachus) megalodon. The assemblage contains taxa with disparate environmental preferences including not only neritic and epipelagic sharks but also an important number of meso and bathypelagic representatives. The migration of deep water taxa to shallower waters through submarine canyons/coastal upwelling is proposed as the most plausible cause for explaining the origin of such assemblage. Interestingly, the composition of the deep-water taxa here reported contrast with the chondrichthyans assemblages from the Pliocene and extant Mediterranean communities. This entails a complex biogeographic history, where the Messinian salinity crisis strongly affected the posterior evolution of the Mediterranean ecosystems but some other factors, such us the existence of anoxic events during the Quaternary, could have also played an important role.

Late Miocene chondrichthyans from Lago Bayano, Panama: Functional diversity, environment and biogeography

AbstractThis newly described chondrichthyan fauna from the late Miocene Chucunaque Formation of Lago Bayano reveals a prolific and highly diverse assemblage from Panama, and one of the richest shark faunas from the Neotropics. Strontium geochronology indicates an age of 10–9.5 Ma for the chonrichthyan-bearing strata. Field efforts resulted in 1429 identifiable specimens comprising at least 31 taxa, of which at least eight are new to the documented fossil record of Panama. With this information an analysis of functional diversity was conducted, indicating ecosystems dominated by generalist species feeding upon a wide range of organisms, from plankton to marine mammals. A probabilistic approach of paleobathymetric estimation suggests a neritic environment. Previous studies based on foraminifera have suggested that the Chucunaque Formation had a greater Pacific Ocean affinity, making this the first Miocene chondrichthyan fauna described from the Pacific shelf of Panama. However, our geographic comparisons show that this fauna has mixed Caribbean and Pacific biogeographic affinities, which likely supports the previously purported connection between chondrichthyan faunas during the late Miocene.

The extinct river shark Glyphis pagoda from the Miocene of Myanmar anda review of the fossil record of the genus Glyphis (Carcharhiniformes: Carcharhinidae).

We redescribe an extinct river shark, Glyphis pagoda (Noetling), on the basis of 20 teeth newly collected from three different Miocene localities in Myanmar. One locality is a nearshore marine deposit (Obogon Formation) whereas the other two localities represent terrestrial freshwater deposits (Irrawaddy sediments), suggesting that G. pagoda from the Irrawaddy sediments was capable of tolerating low salinity like the extant Glyphis. Glyphis pagoda likely reached up to at least 185 cm in total body length and was probably piscivorous. The fossil species occurs in rocks of Myanmar and eastern and western India and stratigraphically ranges at least from the Lower Miocene (Aquitanian) to thelower Upper Miocene (mid-Tortonian). Ithas been classified under at least eight other genera to date, along with numerous taxonomic synonyms largely stemming from the lack of understanding of the heterodonty in extant Glyphis in the original description. Our literature review suggests that known Miocene shark faunas, particularly those in India, are manifested with unreliable taxonomic identifications and outdated classifications that warrant the need for a comprehensive taxonomic review in order to evaluate the evolutionary history and diversity pattern of Miocene shark faunas. The genus Glyphis has a roughly 23-million-year-long history, and its success may be related to the evolution of its low salinity tolerance. While extant Glyphisspp. are considered to be particularly vulnerable to habitat degradation and overfishing, the fossil record of G. pagoda provides renewed perspective on the natural history of the genus that can be taken into further consideration for conservation biology of the extant forms.

A preliminary report on the Early Oligocene (Rupelian, Kiscellian) selachians from the Kiscell Formation (Buda Mts, Hungary), with the re-discovery of Wilhelm Weiler’s shark teeth

An Early Oligocene (Rupelian, Kiscellian), partially published shark tooth material, unearthed from the Kiscell Clay (Budapest, Hungary) is shortly reviewed here. A few shark taxa have been published by Wilhelm Weiler in 1933 and 1938, and some of this material was re-dis- covered in the Hungarian Natural History Museum. Th e here described shark taxa are Notorynchus primigenius , Hexanchus agassizi , Heptranchias howelli , Araloselachus cuspidatus , Carcharias spp., Carcharoides catticus , Isurolamna gracilis , Otodus ( Carcharocles ) angustidens , Alopias cf. exigua , Car- charhinus sp., and Physogaleus latus . Th e results indicate a relatively diverse shark fauna with mixed ecological needs. Th e revised list of the local selachian taxa suggests that a detailed review of all Kiscell shark material (collected in the last century), placed both in public and private collections, is needed. With 73 fi gures, 1 table and 1 appendix.

A gigantic shark from the lower cretaceous duck creek formation of Texas.

Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous.

Marine vertebrates from the Santonian coastal carbonates ofnorthwestern Germany – a tool for the reconstruction of a Proto-North Sea Basin intertidal dinosaur-exchange bridge

AbstractA diverse vertebrate fauna, dominated by sharkteeth, is recorded from conglomerates within the limestonesof the Upper Cretaceous (Santonian) BurgsteinfurtFormation of northwestern Germany. The conglomeratebeds comprise carbonatic, glauconitic and phosphatenodules, as well as Triassic, Jurassic and Cretaceous extraclasts.The Burgsteinfurt Formation conglomerates containfining-upwards parasequences 2–20 cm in thickness,interpreted as tempestite layers within a unit formed bylarger-scale Milankovitch Cycles. The presence of the inoceramidSphenoceramus patootensis and belemnite Gonioteuthisgranulata indicate a late Santonian age for theunit. The studied vertebrate fauna from the Weiner Eschlocality consists of 20 selachian species (14 macroselachiansand 6 microselachians), a few teleosts, rare marinemosasaur remains, and one tooth from a theropod dinosaur.95% of the vertebrates in the assemblage are depositionallyautochthonous, with the remaining materialreworked from older underlying Cenomanian–Coniacian(lower Upper Cretaceous) limestones. On the basis of observedsedimentary structures, the scarcity of deep-seaselachians, and the dominance of the Mitsukurinidae(59% of the preserved shark fauna) in the fossil assemblage,the unit is interpreted as a shallow (0–3 metresdeep), subtidal, nearshore environment, or even subaerialcarbonate-sand islands, located on the southern marginof a submarine swell. The presence of a Santonian theropodin this deposit, and other dinosaur records in northernGermany, together support the interpretation of ashort-lived uplift event with strong upwelling influence forthe Northwestphalian-Lippe submarine swell north of theRhenish Massif in the southern Proto- North Sea Basin. Anew migration model for dinosaurs moving along carbonatecoasts or intertidal zones of shallow carbonate-sand islandsin Central Europe is presented, which may explainthe scattered distribution of dinosaur remains across Europein the Upper Cretaceous.

A sand tiger shark–dominated fauna from the Eocene Arctic greenhouse

ABSTRACTWe describe a new shark fauna from Canada's westernmost Arctic island, Banks Island, Northwest Territories, based upon thousands of shark teeth recovered from lower–middle Eocene sediments of the Cyclic Member (Eureka Sound Formation) on northern Banks Island, Northwest Territories (∼74°N latitude). Based upon palynology, the sediments preserving the shark teeth are late early to middle Eocene in age and likely span the Early Eocene Climatic Optimum (EECO). The low-diversity faunal assemblage is dominated by the sand tiger sharks Striatolamia and Carcharias, but also includes relatively rare teeth of the carcharhinid Physogaleus (extinct relative of sharpnose and tiger sharks) and very rare teeth of the odontaspidid Odontaspis winkleri. We also report the occurrence of the ray Myliobatis. Based upon analogy with extant Carcharias taurus and Myliobatis, the presence of Carcharias and Myliobatis on northern Banks Island corroborates the relatively warm sea surface temperatures estimated by others for the Eocene Arctic Ocean. We hypothesize that the low diversity of the Banks Island shark fauna, in comparison with other early Eocene brackish, shallow-marine chondrichthyan assemblages such as the Abbey Wood (U.K.) fauna, is probably due to environmental factors, including reduced salinity.

SHARKS AND RAYS IN INDONESIA

Indonesia is considered to have a high diversity of sharks and rays due in part to its position in the equatorial line, between two continents and two oceans. According to recent studies and various publications, the number of chondrichthyan species known to date is 207 species of 44 families, comprised of 109 species of sharks, 96 species of batoids, and two species of ghost sharks (chimaera). The Dasyatidae (stingrays) is the most speciose family of chondrichthyans occurring in Indonesia, followed by the Carcharhinidae (whaler sharks). Most species of elasmobranchs commonly occur on the continental or insular shelves and rays are more commonly found than sharks. This type of habitat can be found mostly in the western part of Indonesia (the Java Sea, Karimata Strait, South China Sea, Malacca Strait, and Macassar Strait). Due to the separation by the Wallace Line, there are some differences in species diversity between western and eastern region. The shark and ray fauna of the eastern region is more similar to the Australian fauna, while the fauna in the western region is more similar to the Asian fauna. There are also some endemic species known to occur in Indonesian waters. The endemicity of some species can be restricted in a certain area or in a regional area such as the Indo-West Pacific.