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Clypeasteroid echinoids are widespread and abundant within Miocene sedimentary sequences of the Mediterranean area within both siliciclastic and carbonate deposits. Herein, three clypeasteroid-dominated echinoid assemblages from the mixed siliciclastic-carbonate succession of the Mores Formation (lower Miocene) cropping out within the Porto Torres Basin (northern Sardinia) are described. These assemblages were compared to previously described clypeasteroid-bearing deposits from the Miocene of northern Sardinia with the purpose of investigating their palaeoecology and taphonomy along a shelf gradient. These goals are accomplished by various methods including (i) logging sedimentary facies, (ii) analysing the functional morphology of sea urchin skeletons, (iii) comparing the relative abundance of taxa and taphonomic features, and (iv) studying associated fauna, flora, and trace fossils. The clypeasteroid-bearing deposits differ greatly with respect to echinoid diversity, accompanying fauna and flora, sedimentological signatures, and taphonomic features. They also show variations in depositional environments and the mechanism of formation of the deposits. Three different shelf settings are distinguished: littoral, inner sublittoral, and outer sublittoral environments. Furthermore, an ecomorphological gradient along the shelf is recognized with respect to echinoid taxa and their morphologies. This gradient ranges from shallow water to a moderately deep shelf and is interpreted with respect to both abiotic and biotic factors as well as the taphonomy of the echinoid tests. [ABSTRACT FROM AUTHOR]

The occurrence of typical Boreal echinoid taxa in the Upper Cretaceous of Sardinia is reported and its implications discussed. These new records are unexpected, but not unprecedented, since previous studies have documented other benthic invertebrates with Boreal affinities from the Sardinian Cretaceous. Earlier papers have explained these occurrences by intermittent faunal exchange. This, however, fails to explain why they are absent from most Tethyan shelf deposits. Here we propose a new interpretation: these records could represent examples of a distribution mode widespread in present-day marine species, that of ‘isothermal submergence’. This refers to distribution patterns where organisms occur at different depths at different latitudes. The palaeoenvironmental setting of Sardinia (pelagic limestones) and the Chalk Sea (epicratonic deposits) make such an interpretation plausible. A new species of cardiasterid heart urchin,Infulaster navicularissp. nov., is described, as well as rostrum fragments of aHagenowiaspecies named in open nomenclature. The specimens were collected from the ‘Lanaittu Marl’ exposed in the Gorropu Canyon in eastern Sardinia, and are of Coniacian and Late Santonian age, respectively. The newInfulasterspecies is distinguished by a strongly elongated, non-cordiform outline, high, anteriorly projecting profile, narrow apical angle (c. 55°), and a plastron with two uniserially arranged sternal plates following the labrum. In form it is close toHagenowia infulasteroides, but it differs from that taxon by its contiguous plastron and larger aboral ambulacral pores. http://zoobank.org/urn:lsid:zoobank.org:pub:01FE658C-DF01-4D63-B06C-882A2158FB34 [ABSTRACT FROM PUBLISHER]