HYBODONT SHARKS FROM JURASSIC PCP-BASIN SYSTEMS OF UMBRIAMARCHE APENNINE

ANGELO CIPRIANI; MARCO ROMANO; PAOLO CITTON; SIMONE FABBI

Trento

Congreso; Giornate di Paleontologia XVIII edizione; 2018

Società Paleontologica Italiana

The Umbria-Marche-Sabina (hereafter UMS) Domain in Central and NorthernApennines hosts a Upper Triassic to Neogene sedimentary succession recording a rifting stageoccurred by the late Hettangian, dismembering a Bahamian-type carbonate platform. Tectonicsubsidence and palaeoceanographic/palaeoecological perturbations diachronically led to thedrowning of the benthic factory, triggering the onset of different styles of sedimentation inPCP-basin systems up to the deposition of the Maiolica Fm. since the Tithonian p.p. The newtopographic configuration enabled burgeoning trophic niches available both for the vertebrateand invertebrate fauna. While the invertebrate fossil record of the UMS Domain is wealthy,vertebrate remains are relatively less represented and, thus, to date under-investigated. Threespecimens consisting of teeth attributed to hybodont sharks are here discussed. Twospecimens are isolated teeth referred to as Asteracanthus sp. coming from early Toarcian(Bifrons Zone) red marly-limestone of the Rosso Ammonitico Fm. (Polino, Umbria, Italy).The third specimen comes from the ?Bugarone superiore Fm.? of the Monte Nerone PCP(Piobbico, Marche, Italy). It consists of five teeth in anatomical connection and somefragments referred to as Asteracanthus cf. A. magnus. In the Mesozoic, hybodont sharksdominated a wide range of ecological niches, displaying many different dentition patterns andlifestyles. On the whole, the teeth here reported fit well a dentition pattern known as ?Typebroyeur?, typical of extreme crushing feeding behaviour, characterizing Jurassic hybodontsharks feeding on the seafloor. The genus Asteracanthus has a cosmopolitan distribution inthe Jurassic of Tethys and has been reported from several palaeoenvironments; in the presentcase, the taxon is related to open marine settings. By considering the invertebrate fauna thatinhabited PCP-basin contexts of UMS Domain, potential prey living on the sea-floor areostreids, limids, terebratulid brachiopods, gastropods and crustaceans. Zooxanthellate coralsfrom several PCP-top and basin-margin condensed successions indirectly extend the in-depthAsteracanthus outreach to more than 100 m, increasing the range depth previously reportedfor this taxon.