Intraspecific dental variations in the deep-sea shark Etmopterus spinax and their significance in the fossil record

An important character on several taxonomic levels for shark identification is the tooth morphology. Sharks show a variety of highly specialized dentitions reflecting adaptations to their feeding habits. Intraspecific variation of tooth morphology such as sexual or ontogenetic dimorphism is poorly known in many species, even though tooth morphology plays a decisive role in the characterization of the fossil record of sharks, which comprises mostly fossil teeth. Here we analyzed the dentition of 40 jaws of the Velvet Belly Lantern Shark Etmopterus spinax and identified ontogenetic and sexual dimorphic characters such as total number of teeth, number of upper teeth, cusplet numbers in upper jaw teeth and width of lower jaw teeth. Dimorphic characters may reduce intraspecific competition for food, as E. spinax segregates by sex and size and may allow for identifying the male sex. The lower jaw tooth height, a sexually non-dimorphic character, was used to re-calculate the total length of specimens, which represents the first such approach for a squaliform shark. Results derived from the extant E. spinax are subsequently applied to fossil Etmopterus sp. teeth (Miocene) to gain individual information such as sex or size, but also characterize the extinct population from the excavation site by a size distribution profile in comparison to data from extant populations. This approach indicates the presence of multiple ontogenetic stages in the extinct population.publishedVersio

Parasquatina zitteli nov. sp. (Elasmobranchii: Orectolobiformes) aus dem Maastricht von Oberbayern (Gerhartsreiter Schichten, Siegsdorf) und Bemerkungen zur Verbreitung der Ordnung Orectolobiformes

Pollerspöck J, Beaury B: Parasquatina zitteli nov. sp. (Elasmobranchii: Orectolobiformes) from the Maastrichian of Upper Bavaria (Gerhartsreiter Ditch, Siegsdorf), with remarks on the distribution of the order Orectolobiformes. The genus Parasquatina is documented for the first time from the Gerhartsreiter Ditch near Siegsdorf (Upper Bavaria, Germany). The fossils are interpreted as a new species, for which the name Parasquatina zitteli nov. sp. is proposed, because they differ in morphology from all other species in that genus, especially with regard to the labial apron, which is absent in P. zitteli. Assignment of the genus Parasquatina to the order Squatiniformes is reversed, and the genus now placed in the order Orectolobiformes. In addition, a survey of recent records of Parasquatina is given, together with an up-to-date overview of the stratigraphic distribution of the order Orectolobiformes, and resulting questions are discussed.Aus dem Gerhartsreiter Graben bei Siegsdorf wird der erste Nachweis der Gattung Parasquatina dokumentiert und aufgrund der morphologischen Unterschiede zu den bisher bekannten Arten die Art Parasquatina zitteli nov. sp. beschrieben. Parasquatina zitteli nov. sp. unterscheidet sind von allen beschriebenen Arten dieser Gattung insbesondere durch das Fehlen des labialen Aprons. Die bisher bereits zweifelhafte taxonomische Zuordnung von Parasquatina zur Ordnung der Squatiniformes wird aufgegeben und die Gattung zur Ordnung der Orectolobiformes gestellt. Neben einer Zusammenfassung über die bisher in der Literatur dokumentierten Funde von Parasquatina wird eine aktuelle Übersicht über die stratigraphische Verbreitung der Ordnung Orectolobiformes vorgestellt und die sich daraus ergebenden Fragen diskutiert

Trophic position of Otodus megalodon and great white sharks through time revealed by zinc isotopes

Diet is a crucial trait of an animal’s lifestyle and ecology. The trophic level of an organism indicates its functional position within an ecosystem and holds significance for its ecology and evolution. Here, we demonstrate the use of zinc isotopes (δ66Zn) to geochemically assess the trophic level in diverse extant and extinct sharks, including the Neogene megatooth shark (Otodus megalodon) and the great white shark (Carcharodon carcharias). We reveal that dietary δ66Zn signatures are preserved in fossil shark tooth enameloid over deep geologic time and are robust recorders of each species’ trophic level. We observe significant δ66Zn differences among the Otodus and Carcharodon populations implying dietary shifts throughout the Neogene in both genera. Notably, Early Pliocene sympatric C. carcharias and O. megalodon appear to have occupied a similar mean trophic level, a finding that may hold clues to the extinction of the gigantic Neogene megatooth shark.publishedVersio

Intraspecific dental variations in the deep-sea shark Etmopterus spinax and their significance in the fossil record

An important character on several taxonomic levels for shark identification is the tooth morphology. Sharks show a variety of highly specialized dentitions reflecting adaptations to their feeding habits. Intraspecific variation of tooth morphology such as sexual or ontogenetic dimorphism is poorly known in many species, even though tooth morphology plays a decisive role in the characterization of the fossil record of sharks, which comprises mostly fossil teeth. Here we analyzed the dentition of 40 jaws of the Velvet Belly Lantern Shark Etmopterus spinax and identified ontogenetic and sexual dimorphic characters such as total number of teeth, number of upper teeth, cusplet numbers in upper jaw teeth and width of lower jaw teeth. Dimorphic characters may reduce intraspecific competition for food, as E. spinax segregates by sex and size and may allow for identifying the male sex. The lower jaw tooth height, a sexually non-dimorphic character, was used to re-calculate the total length of specimens, which represents the first such approach for a squaliform shark. Results derived from the extant E. spinax are subsequently applied to fossil Etmopterus sp. teeth (Miocene) to gain individual information such as sex or size, but also characterize the extinct population from the excavation site by a size distribution profile in comparison to data from extant populations. This approach indicates the presence of multiple ontogenetic stages in the extinct population

Parasquatina zitteli nov. sp. (Elasmobranchii: Orectolobiformes) aus dem Maastricht von Oberbayern (Gerhartsreiter Schichten, Siegsdorf) und Bemerkungen zur Verbreitung der Ordnung Orectolobiformes

Pollerspöck J, Beaury B: Parasquatina zitteli nov. sp. (Elasmobranchii: Orectolobiformes) from the Maastrichian of Upper Bavaria (Gerhartsreiter Ditch, Siegsdorf), with remarks on the distribution of the order Orectolobiformes. The genus Parasquatina is documented for the first time from the Gerhartsreiter Ditch near Siegsdorf (Upper Bavaria, Germany). The fossils are interpreted as a new species, for which the name Parasquatina zitteli nov. sp. is proposed, because they differ in morphology from all other species in that genus, especially with regard to the labial apron, which is absent in P. zitteli. Assignment of the genus Parasquatina to the order Squatiniformes is reversed, and the genus now placed in the order Orectolobiformes. In addition, a survey of recent records of Parasquatina is given, together with an up-to-date overview of the stratigraphic distribution of the order Orectolobiformes, and resulting questions are discussed.Aus dem Gerhartsreiter Graben bei Siegsdorf wird der erste Nachweis der Gattung Parasquatina dokumentiert und aufgrund der morphologischen Unterschiede zu den bisher bekannten Arten die Art Parasquatina zitteli nov. sp. beschrieben. Parasquatina zitteli nov. sp. unterscheidet sind von allen beschriebenen Arten dieser Gattung insbesondere durch das Fehlen des labialen Aprons. Die bisher bereits zweifelhafte taxonomische Zuordnung von Parasquatina zur Ordnung der Squatiniformes wird aufgegeben und die Gattung zur Ordnung der Orectolobiformes gestellt. Neben einer Zusammenfassung über die bisher in der Literatur dokumentierten Funde von Parasquatina wird eine aktuelle Übersicht über die stratigraphische Verbreitung der Ordnung Orectolobiformes vorgestellt und die sich daraus ergebenden Fragen diskutiert

Eine Elasmobranchierfauna (Elasmobranchii, Neoselachii) aus der Oberen Meeresmolasse (Ottnangium, Unteres Miozän) des Heigelsberger Grabens bei Teisendorf, Oberbayern

Pollerspöck J, Beaury B: A Miocene elasmobranch fauna (Elasmobranchii, Neoselachii) from the Upper Marine Molasse of Upper Bavaria (Heigelsberger Ditch, Teisendorf, Bavaria). A rich assemblage of elasmobranch teeth of Early Miocene age (Ottnangian, Upper Marine Molasse) is described from the Heigelsberger Ditch near Teisendorf (Upper Bavaria, Germany). The fauna includes 13 shark and 4 batoid species, including Centrophorus cf. granulosus, Isistius triangulus, Squalus sp., Pristiophorus suevicus, Squatina sp., Mitsukurina lineata, Alopias exigua, Carcharhinus priscus, Hemipristis serra, Chaenogaleus affinis, Iago angustidens, Premontreia sp., Carcharias acutissimus, Raja sp., Dasyatis rugosa, Dasyatis probsti, and Myliobatis sp., which are reported for the first time from the Upper Bavarian part of the Subalpine Molasse Basin.Aus der Oberen Meeresmolasse (Ottnangium) Bayerns (Heigelsberger Graben bei Teisendorf, Deutschland) wird erstmals eine artenreiche Hai- und Rochenfauna beschrieben. Insgesamt konnten 13 Hai- und 4 Rochenarten nachgewiesen werden (Centrophorus cf. granulosus, Isistius triangulus, Squalus sp., Pristiophorus suevicus, Squatina sp., Mitsukurina lineata, Alopias exigua, Carcharhinus priscus, Hemipristis serra, Chaenogaleus affinis, Iago angustidens, Premontreia sp., Carcharias acutissimus, Raja sp., Dasyatis rugosa, Dasyatis probsti, Myliobatis sp.)

First record of the somniosid shark Protoxynotus misburgensis from the Santonian (Late Cretaceous) of the Southern Tethyan Realm

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