Reassessment of a large lamniform shark from the Upper Cretaceous (Santonian) of Italy (original) (raw)
Related papers
Journal of Paleontology, 2022
The definition of the Cretaceous shark genus Cretodus Sokolov, 1965 is primarily based on isolated teeth. This genus includes five species. Among these, Cretodus houghtonorum Shimada and Everhart, 2019 is the only species based on a partially preserved skeleton. Here, the taxonomic attribution of a virtually complete skeleton of Cretodus from the Turonian of northeastern Italy is discussed, together with a few specimens from the Turonian of England. One of the latter is investigated through micropaleontological analysis to determine its stratigraphic position. The material is referred to Cretodus crassidens (Dixon, 1850), the diagnosis of which is emended herein. The dentition is tentatively reconstructed, exhibiting strong similarities with congeneric species, although it differs in having strong vertical folds on the main cusp labial face, a mesiodistally broad tooth aspect, weak and well-spaced 'costulae' at crown base, and a different dental formula in the number of parasymphyseal and lateral rows. Some tooth malformations are interpreted as feeding-related or senile characters. The Italian specimen suggests that Cretodus crassidens had a wide and laterally expanded mouth and head, a stout body, and attained a gigantic size. Cretodus crassidens was a moderate-speed swimming shark ecologically like the extant tiger shark Galeocerdo cuvier (Péron and Lesueur in Lesueur, 1822). The age estimate from vertebral-band counting suggests that the Italian individual was at least 23 years old and the growth model indicates a longevity of 64 years and a maximum attainable total length of 9-11 m. Cretodus crassidens occurs both in Boreal and Tethyan domains, implying a broad paleobiogeographic distribution and a preference toward offshore settings. Geological setting The geological setting of the 'Lastame' lithofacies of the Scaglia Rossa of the Lessini Mountains (∼30 km N of Verona, Veneto, Italy; Fig. 1), which yielded the Cretodus remains, has been thoroughly described in a series of papers dealing with the remarkable vertebrate assemblage of this Cretaceous Lagerstätte *Corresponding author.
Cretaceous Research, 2019
Cretoxyrhina mantelli was a large pelagic lamniform shark geographically widespread during the Late Cretaceous, and well known because of several nearly complete skeletons from the Western Interior Seaway of North America. Here we report 15 partial skeletons belonging to lamniform sharks from the 'lastame' lithozone of the Upper Cretaceous Scaglia Rossa Formation of the Lessini Mountains (northeastern Italy). Seven partial but articulated skeletons include tooth sets that allow a confident attribution to Cretoxyrhina mantelli based on dental morphologies. We review the taxonomic history of C. mantelli, evidencing that the taxon was erected by Agassiz (1835) and tracing back four of the original syntypes. Based on calcareous plankton biostratigraphy, the rock in
Journal of Vertebrate Paleontology
We describe a partial skeleton of the Late Cretaceous shark, Cretodus, collected from the Blue Hill Shale (middle Turonian) in north-central Kansas, U.S.A. It consists of 134 disarticulated teeth, 61 vertebrae, 23 placoid scales, and fragments of calcified cartilage. The scale morphology suggests that Cretodus was a rather sluggish shark, and the vertebral morphology affirms its placement into Lamniformes. With a strong tendency towards monognathic heterodonty, the dental morphology indicates that the specimen belongs to a new species, C. houghtonorum, sp. nov., increasing the total known species of Cretodus to five. The five species can be divided into three distinct groups: the longiplicatus/semiplicatus-grade, gigantea/houghtonorumgrade, and crassidens-grade. Cretodus, that successively evolved by broadening the tooth crown. The individual of C. houghtonorum, sp. nov., is estimated to be about 515 cm in total length (TL). Our vertebra-based growth analysis suggests that the shark was about 118 cm TL at birth and that the species had an estimated maximum growth length of 684 cm TL. The large size at birth indicates that the intrauterine cannibalism behavior of embryos seen in extant lamniforms had already evolved by the Late Cretaceous. Where C. houghtonorum, sp. nov., preferred nearshore environments, the specimen cooccurred with isolated teeth of Squalicorax and fragments of two dorsal fin spines of a hybodont shark, circumstantially indicating that the individual of Cretodus fed on the much smaller hybodont and was scavenged by Squalicorax.
A new early cretaceous lamniform shark (Chondrichthyes, Neoselachii)
Zoological Journal of The Linnean Society, 2008
Eoptolamna eccentrolopha gen. et sp. nov. (Chondrichthyes, Lamniformes) from the near coastal upper Barremian Artoles Formation (Early Cretaceous) of Castellote (northwestern Spain) is described on the basis of about 50 isolated teeth. This taxon represents one of the earliest lamniform sharks known to date. We hypothesize that most pre-Aptian lamniforms belong to an ancient group characterized, amongst others, by a very weak gradient monognathic heterodont dental pattern, and by tearing-type dentition. There is a nutritive groove in the lingual root protuberance in juveniles of Eoptolamna, which persists in adults. A single pair of symphysial and a pair of upper intermediate teeth might have been present. Consequently, a new family, Eoptolamnidae, is introduced to include the new form, as well as Protolamna and probably Leptostyrax. The Eoptolamnidae represent an ancient family within Lamniformes. The origin of lamniform sharks remains, however, ambiguous despite recent advances. The new Spanish taxon is widespread in the Barremian of north-eastern Spain, and occurs in a wide range of facies from near-coastal to lake deposits. This lamniform also occurs in the Lower Cretaceous of northern Africa. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290.
The revision of "Cladodus" occidentalis, a late Palaeozoic ctenacanthiform shark
2000
. The revision of "Cladodus" occidentalis, a late Palaeozoic ctenacanthi− form shark. Acta Palaeontologica Polonica 50 : 623-631. The teeth of a well known late Palaeozoic cladodont chondrichthyan, "Cladodus" occidentalis from Russia, USA, and England are restudied and a new generic name, Glikmanius gen. nov., is proposed for this species. Yet another tooth−based species, formerly described as ?Symmorium myachkovensis, occurring on the Russian Platform and in Ne− braska, is considered to belong to the newly erected genus. Although there is no direct evidence that Glikmanius pos− sessed fin spines, the broad similarity between its teeth and those of Ctenacanthus compressus suggests it had a ctenacanthiform affinity. The possible relationships between Glikmanius, Cladodus sensu stricto, "Ctenacanthus" costellatus, and Heslerodus, are suggested. However, the proposition put forward by an earlier author that the teeth of Heslerodus might represent the lower jaw dentition of G. myachkovensis, is rejected. The overall resemblance of Glikmanius teeth and those of Cladoselache and Squatinactis is recognised as convergent.
A partial skeleton of a new lamniform mackerel shark from the Miocene of Europe
2016
Cenozoic lamniform sharks are mostly represented by isolated teeth and vertebrae, whereas articulated skeletal remains are usually very scarce. Here, we describe a partial skeleton of an extinct lamniform shark consisting of 42 slightly disarticulated teeth, 49 vertebrae, and additional unidentifiable cranial and postcranial remains. The specimen originates from the Miocene mica-clay of Groß Pampau (North Germany), which is of late Langenfeldian age ( = Serravallian-Tortonian boundary; middle–late Miocene). A total of 13 measurements of each tooth, as well as morphological features, were used to reconstruct the dentition of this specimen and to provide detailed taxonomic information. Additionally, the total body size and age at death were established using methodologies based on vertebral and tooth measurements and vertebral centra growth ring counts, respectively. The specimen undoubtedly represents the most complete indi-vidual of “Carcharodon ( = Isurus) escheri”, previously know...
PLOS ONE
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.
Skeletal anatomy of the Late Cretaceous shark,Squalicorax (Neoselachii: Anacoracidae)
Paläontologische Zeitschrift, 2005
The paleobiology of the Cretaceous neoselachian shark, Squalicorax, has largely been based on isolated teeth. We examined partial and nearly complete skeletons of three species of Squalicorax, S. falcatus (AGASSIZ), S. kaupi (AGASSIZ), and S.pristodontus (AGASSIZ), that were collected from the U.S.A. These specimens suggest that the total body length (TL) of S.falcatus typically measured 1.8-2.0 m, and probably did not exceed 3 m. Moderatesized individuals of S. kaupi and S. pristodontus perhaps measured about 3 m TL. Although S. pristodontus was the largest form among the three species examined, this taxon possessed a set of large jaws (with large but fewer teeth) relative to its body size compared to S.falcatus or S. kaupi. This suggests that tooth size is not an accurate indicator of the TL if one compares one Squalicorax species to another. Neurocranial features suggest that the vision of Squalicorax was not as acute as that of a contemporaneous macrophagous lamniform shark, Cretoxyrhina mantelli (AGAS-SIZ), but olfaction of Squalicorax may have been better than C. mantelli. The morphology of placoid scales suggests that Squalicorax was capable of fast swimming. New skeletal data support the view that the feeding dynamics of Squalicorax was similar to the modern tiger shark (Galeocerdo MULLER & HENLE). The present data do not allow for exact ordinal placement, but, contrary to some previous interpretations, Squalicorax can be excluded from the Hexanchiformes and Orectolobiformes. The taxon should more appropriately be placed within the Lamniformes or Carcharhiniformes.
Palaeontologia Electronica, 2021
The megatooth shark, Otodus megalodon, is widely accepted as the largest macrophagous shark that ever lived; and yet, despite over a century of research, its size is still debated. The great white shark, Carcharodon carcharias, is regarded as the best living ecological analog to the extinct megatooth shark and has been the basis for all body length estimates to date. The most widely accepted and applied method for estimating body size of O. megalodon was based upon a linear relationship between tooth crown height and total body length in C. carcharias. However, when applying this method to an associated dentition of O. megalodon (UF-VP-311000), the estimates for this single individual ranged from 11.4 to 41.1 m. These widely variable estimates showed a distinct pattern, in which anterior teeth resulted in lower estimates than posterior teeth. Consequently, previous paleoecological analyses based on body size estimates of O. megalodon may be subject to misinterpretation. Herein, we d...