A new specimen of shark from the Monte Postale locality (Eocene, Bolca) and the rise of the Triakids in ancient ecosystems

This thesis focuses on the description of a fossil shark found in the Museo di Storia Naturale di Pavia during a complex restoration project started in 1989. The specimen represents one of the rarest shark taxa from the world–renown Eocene Bolca locality. Unlike the Ypresian taxa Galeorhinus cuvieri and Eogaleus bolcensis, the specimen partly disarticulated and lies in a limestone matrix, suggesting its provenience from the Monte Postale site. The dataset of measurements for body parameters, vertebral centra, teeth and placoid scales was compared to both fossil and extant taxa in order to discuss the overall systematic assessments of the Bolca sharks at higher taxonomic levels. Overall body measurements collected from all Bolca specimens were combine in order to estimate the size of the examined specimen. Statistical approach performed on body measurements and preserved vertebrae support a largely sharing of these characters among the extant taxa of the order Carcharhiniformes. SEM analysis on dermal denticle support that the Pavia specimen is an individual of Eogaleus bolcensis. A comprehensive dataset of teeth was used to compare dental morphologies of the living species Galeorhinus galeus and Galeocerdo cuvier, considered here as standards. The general clustering is primarily based on qualitative characters and ratios between selected measurements. The comparison between fossil and extant taxa based on newly defined tooth morphotypes increase our knowledge on taxonomic identifications of Bolca’s sharks. The morphometrical measurements for each fossil specimen indicates three distinct ontogenetic classes, further supported by estimated ages following standard Von Bertalanffy growth curves. As the present–day Galeocerdo, Eogaleus was most likely a mesopelagic, top predator. The combination of biological and abiotic proxies suggests the Bolca setting as a possible nursery area for the juvenile–schooling individuals of G. cuvieri

An exceptionally preserved Eocene shark and the rise of modern predator-prey interactions in the coral reef food web

Following extreme climatic warming events, Eocene Lagerstätten document aquatic and terrestrial vertebrate faunas surprisingly similar to modern counterparts. This transition in marine systems is best documented in the earliest teleost-dominated coral reef assemblage of Pesciara di Bolca, northern Italy, from near the end of the Eocene Climatic Optimum. Its rich fauna shows similarities with that of the modern Great Barrier Reef in niche exploitation by and morphological disparity among teleost primary consumers. However, such paleoecological understanding has not transcended trophic levels above primary consumers, particularly in carcharhiniform sharks

Why so many dipnoans? A multidisciplinary approach on the Lower Cretaceous lungfish record from Tunisia

The Lower Cretaceous record of vertebrates from Africa is problematic as the majority of fossil localities lack adequate stratigraphic and paleoecological data when compared with coeval Laurasian deposits. Thereby, our comprehension of paleocommunities and paleobiogeographic patterns may be affected by the lack of multidisciplinary approach. Among taxonomically and paleoecological significant clades, lungfishes (Sarcopterygii, Dipnoi) are commonly found in the Cretaceous fresh water, brackish and marginal-marine deposits of Gondwana, although identifiable elements are limited to isolated tooth plates. We provide the first taxonomic identification of dipnoans from the Ain el Guettar Formation of southern Tunisia (Oum ed Diab Member, Albian). Identification of tooth plates based on morphological parameters and phylogenetic analyses indicate the co-occurrence in a discrete stratigraphic unit of at least five lineages referable to Equinoxiodus, Neoceratodus, Asiatoceratodus and/or Ferganoceratodus, Ceratodus, and Lavocatodus. This unusually high diversity is unparalleled in the fossil record and is also challenged by an actualistic comparison with extant taxa. We suggest that a series of taphonomic factors significantly inflated observed lungfish diversity in the estuarine and marginal-marine deposits of the Oum ed Diab Member. Therefore, we recognize the fossil fauna as representative of a larger, inland paleo-hydrographic system. This study confirms the paleoecological scenario resulted from the analyses on terrestrial reptiles from the Oum ed Diab Member

Reassessment of a large lamniform shark from the Upper Cretaceous (Santonian) of Italy

To date, only a few partially articulated chondrichthyan specimens are known from the Upper Cretaceous marine fossil record of northern Italy. Here, we re-evaluate the taxonomic status and geological age of selachian remains originally discovered during the 19th century from the Castellavazzo locality. The described specimen is largely embedded in matrix with minute exposure of joined and moderately deformed sequentially stacked vertebral centra. Computed tomography (CT) image-data obtained of the specimen enabled the identification of potential cranial-cartilage elements located in close proximity to teeth and are here interpreted as remnants of the jaws. Based on tooth and vertebral morphology the specimen is in all likelihood an adult lamniform shark with a measured 3.5 m length. Using ordinary least-squares regression analysis (OLS) and proportion-based calculations, we estimated a total-length (TL) of 596.27 and 632.5e672.64 cm respectively. We prefer the size estimation derived through OLS bivariate regression; however, in the present analysis, reliance on a small sample size (n ¼ 11) and evidence for differential scaling between taxa impose limitations on the precision of our size prediction. Planktonic foraminifera examined from the surrounding matrix of the slab preserving shark vertebral centra and teeth indicate a Santonian age (Dicarinella asymetrica zone). Although, the specimen could not confidently be assigned beyond the ordinal-level, the sheer centrum size, gross dental morphology, and depositional environment, are indicative of a pelagic apex-predator comparable to coeval lamniforms, with a specific resemblance towards cretoxyrhinids, reported from elsewhere along the peri-Tethyan shelf of Europe and Western Interior Seaway of North America. Finally, the re-emergence of this historical specimen, here re-described using cutting-edge techniques, is of great importance as it contributes to the otherwise poor record of extinct lamniform shark skeletons