The first ophthalmosaurid ichthyosaur from the Upper Jurassic of the Umbrian–Marchean Apennines (Marche, Central Italy)

Abstract

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

Hybodont dentition from the Upper Jurassic of Monte Nerone Pelagic Carbonate Platform (Umbria‐Marche Apennine, Italy) and its ecological implications

“…According to Wahl (), the presence of abundant medium‐size predators such as small plesiosaurs and ichthyosaurs may have represented a competitive exclusion for the nonreptilian vertebrate such as durophagous sharks, bringing their presence to a minimum. Considering that material referred to ichthyosaurs is known from the UMS Domain (see Paparella et al, ), including material precisely from the Kimmeridgian of Monte Nerone area, the extreme poverty of hybodont remains found in this domain could fit such an ecological explanation.…”

“…These fossil remains are represented by fragments of crinoids belonging to the genus Saccocoma and by the thin‐shelled (sensu Giovagnoli & Schiavinotto, ) “pelagic” foraminifer Globuligerina oxfordiana (Figure d). The ecological event represented by the mass occurrence of the genus Saccocoma is dated, at a regional scale, to the latest early Kimmeridgian (Paparella, Maxwell, Cipriani, Roncacè, & Caldwell, and references therein). Two species of Saccocoma characterize the Upper Jurassic stratigraphic record of the Western Tethys: Saccocoma tenella and Saccocoma vernioryi (Manni & Nicosia, ).…”

Peer Review #2 of "A new specimen of Palvennia hoybergeti: implications for cranial and pectoral girdle anatomy in ophthalmosaurid ichthyosaurs (v0.1)"

“…Anteriorly, it is elongate and mediolaterally and dorsoventrally narrow; in the posterior half, the element widens into a dorsoventrally oriented sheet that gradually decreases in height posteriorly. The dorsal sheet has an uneven outline in lateral view with at least two broken processes in the dorsal portion oriented dorsally and anteriorly, as in Ophthalmosaurus icenicus and Gengasaurus nicosiai (Moon & Kirton, 2016;Paparella et al, 2016). The element is laterally convex with a lateral side that is more uneven than the smoother, medial side.…”

Restos apendiculares de un ictiosaurio oftalmosáurido del Barremiano inferior de Villa de Leiva, Colombia

“…P. ochevi y P. campylodon son considerados como species inquirenda por Fischer et al (2016). (Maxwell y Caldwell, 2006a;Maxwell y Caldwell, 2006b;Maxwell, 2010;Druckenmiller y Maxwell, 2010;Fischer et al, 2011a;Fernández y Maxwell, 2012;Druckenmiller et al, 2012;Fischer, 2012;Fischer et al, 2012;Roberts et al, 2014;Fischer et al, 2014a;Fischer et al, 2014b;Ji et al, 2016;Paparella et al, 2017;Maxwell et al, 2016;Fischer et al, 2016). Un panorama de estos aportes, con sus respectivas referencias, se expone sintéticamente en la revisión de las ocurrencias de especímenes de oftalmosáuridos presentada por Fernández y Campos (2015).…”