The first ophthalmosaurid ichthyosaur from the Upper Jurassic deposits of the Central–\ud
Northern Apennines (Marche, Italy) is here described for the first time. The specimen is relatively\ud
complete and is referred to Gengasaurus nicosiai gen. et sp. nov. based on a unique combination of\ud
characters, including a peculiar condition of the preaxial accessory facet on the humerus. The faunal\ud
association of the ichthyosaur-bearing level indicates a late Kimmeridgian – earliest Tithonian age,\ud
and its finding contributes significantly to our knowledge of the diversity of Late Jurassic ichthyosaurs\ud
from the Western Tethys. Two shark teeth assigned to the order Hexanchiformes were also recovered\ud
in association with the ichthyosaur specimen, suggesting that scavenging of the carcass might have\ud
occurred. Gengasaurus can be referred to Ophthalmosauridae based on the reduced extracondylar\ud
area of the basioccipital, and the presence of a preaxial digit. It differs from Ophthalmosaurus spp.\ud
in several respects, including the shape of the posterior basisphenoid, the shape of the supraoccipital,\ud
the anteriorly deflected preaxial facet of the humerus, and a proximodistally shortened ulna. The new\ud
taxon actually shares diagnostic characters with both members of the two main lineages recovered in\ud
previous phylogenetic analyses,more nested within Ophthalmosauridae. The affinities of Gengasaurus\ud
to genera from both the northern and southern hemispheres also suggest that connectivity between\ud
pelagic habitats was high during the early Late Jurassic, allowing dispersal of some forms, followed\ud
by local, endemic divergence
The digital storage and communication of significant geological data became\ud
increasingly more objective and accessible through the development of new technologies or the\ud
implementation of already well-known techniques as photogrammetry. Digital acquisition of\ud
geometries (both structural and depositional) of significant geological outcrops is deemed\ud
necessary, especially if the site concerned is liable to be damaged or hopelessly involved in natural\ud
processes of geological and geomorphological evolution. In this paper, we tested the performances\ud
of two different open-source software (i.e. VisualSFM and ARC3D) on a small-scale but\ud
paradigmatic outcrop in the Umbria-Marche Apennines (Italy). The test showed that ARC3D\ud
provides an high-resolution model, employing a relatively short time and requiring a not expensive\ud
hardware support for processing hundreds of photos. In the text, 3D models of the selected outcrop\ud
are reported and discussed emphasizing the potential of the method to highlight structural,\ud
sedimentological and paleontological details.\ud
As a result, 3D photogrammetry proved to be a powerful and effective tool to digitally conserve and\ud
objectively communicate important geological observations and to facilitate accessibility and\ud
dissemination of the collected data within the scientific community
This paper is companion to a 1:15,000 scale geological map of the southern sector of the Narni Range in Central Italy. This sector of the Apenninic Chain was affected by the western Tethyan rifting stage during the Early Jurassic, and the inherited architectural setting in turn influenced the Mesozoic stratigraphy and the Neogene-Quaternary tectonic evolution of the area. Based on stratigraphic and structural field evidence, a Jurassic structural high has been identified in the Mt. Cosce sector, flanked northward and westward by deeper basins. The basin that had to exist to the east, as well as the top of the horst-block, cannot be observed due to recent erosion and orogenic deformation. The western margin of the Mt. Cosce High was rejuvenated during an extensional tectonic phase which took place in the late Early Cretaceous. This synsedimentary faulting is reported in this area for the first time, and is documented by a sedimentary breccia (Mt. Cosce Breccia) resting unconformably on the Jurassic footwall-block.
ARTICLE HISTORY
Here we describe a number of articulated teeth of a hybodont shark from Upper Jurassic deposits of the Monte Nerone Pelagic Carbonate Platform, in the Umbria‐Marche‐Sabina Palaeogeographic Domain (Northern Apennines, Central Italy). The material has been referred to as Asteracanthus cf. A. magnus, a quite well‐known taxon already reported from Middle to Upper Jurassic deposits of Europe. Teeth indicate an extreme crushing feeding behaviour, suggesting as putative prey both infaunal and epifaunal hard‐shelled invertebrates dwelling the sea‐floor, such as large bivalves, brachiopods, gastropods as well as vagile crustaceans. The finding represents, to date, the first formal report of hybodont shark in the Umbria‐Marche‐Sabina Domain, throwing further light on the ecology within Pelagic Carbonate Platform settings, and on the occurrence of Asteracanthus in the Late Jurassic of the Western Tethys.
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