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Echinoids represent an important component of the Cenozoic marine benthic communities. Their diversity in the Mediterranean area is reviewed within the Late Miocene–Recent, a period of remarkable paleogeographic and paleoclimate changes. Of the 37 genera that lived during the Late Miocene, only Holaster, Pliolampas, and Trachyaster did not survive the Messinian Mediterranean salinity crisis (MSC), indicating that this event was not as drastic as for other marine groups. The presence of Brissopsis within the uppermost Messinian testifies to the existence of fully marine conditions at least towards the end of the MSC. Severe drops in the echinoid diversity, involving the loss of 40% of the Pliocene genera, occurred during the Piacenzian, likely because of the onset of the Northern Hemisphere glaciation. Most of the echinoid extinctions correlate with the crisis of the Mediterranean bivalve assemblage recorded at about 3 Ma. The Early Pleistocene progressive cooling caused the disappearance of further thermophilous shallow-water genera (Clypeaster, Schizechinus, Echinolampas) and allowed the entrance of temperate taxa (Paracentrotus lividus, Placentinechinus davolii and Sphaerechinus granularis) from the Atlantic. Some deep-water taxa (Histocidaris sicula, Stirechinus scillae, Cidaris margaritifera), whose Recent relatives are currently restricted to tropical areas, are not found in the area after the Calabrian possibly because of the disappearance of the psychrosphere. The extant Mediterranean echinoid fauna mainly derives from the Late Miocene fauna, reduced after several climatic changes by about 43% at the genus level. The recent increase of the sea surface temperatures allowed the entrance of the Lessepsian Diadema setosum and confined the deep-water species of Holanthus to the coldest areas of the basin, making this genus endangered.

A critical reassessment of foraminiferan parasitism on echinoid hosts, past and present, identifies all previous records as doubtful and circumstantial evidence as being limited to possible foraminiferan bioerosion traces on a Late Cretaceous Echinocorys perconicus host from Northern Germany. Here, we report on a second type of putative foraminiferan attachment trace fossils found on a Late Cretaceous Echinocorys jaekeli from the Danish Basin, and establish the new ichnogenus and ichnospecies Solichnus aestheticus within the ichnofamily Centrichnidae. These delicate sun-shaped etchings are diagnosed as bowl-shaped circular depressions, wider than deep, from which numerous open canals radiate in a meandering fashion, ramify, and thin out. The canals indicate a mutual avoidance pattern with those of neighbouring specimens and they circumvent the areoles of the echinoid's primary tubercles. We interpret the central depression as anchoring site of a foraminiferan test and the radiating canals, formed right at the interface of the stereom and epithelium, as the work of its long and ramifying pseudopodia. The symbiotic relationship was probably of parasitic nature (sensu stricto), with the foraminiferan feeding on the organic tissue of the epithelium (epithelium browsing) and profiting from protection offered by the host's spines and defensive pedicellariae. The echinoid survived the infestation and formed skeletal regeneration textures that clearly identify the association as syn vivo. The high degree of specialisation required to infest an echinoid host and form the complex attachment trace might suggest that the pronounced rarity of the trace is not a case of a false host but of host specificity. The identity of the foraminiferan parasite remains unknown, although the bioerosion traces show some affinity to those of the extant species Cymbaloporella tabellaeformis and Gypsina vesicularis. [ABSTRACT FROM AUTHOR]

Echinoids represent an important component of the Cenozoic marine benthic communities. Their diversity in the Mediterranean area is reviewed within the Late Miocene-Recent, a period of remarkable paleogeographic and paleoclimate changes. Of the 37 genera that lived during the Late Miocene, only Holaster, Pliolampas, and Trachyaster did not survive the Messinian Mediterranean salinity crisis (MSC), indicating that this event was not as drastic as for other marine groups. The presence of Brissopsis within the uppermost Messinian testifies to the existence of fully marine conditions at least towards the end of the MSC. Severe drops in the echinoid diversity, involving the loss of 40% of the Pliocene genera, occurred during the Piacenzian, likely because of the onset of the Northern Hemisphere glaciation. Most of the echinoid extinctions correlate with the crisis of the Mediterranean bivalve assemblage recorded at about 3 Ma. The Early Pleistocene progressive cooling caused the disappearance of further thermophilous shallow-water genera (Clypeaster, Schizechinus, Echinolampas) and allowed the entrance of temperate taxa (Paracentrotus lividus, Placentinechinus davolii and Sphaerechinus granularis) from the Atlantic. Some deep-water taxa (Histocidaris sicula, Stirechinus scillae, Cidaris margaritifera), whose Recent relatives are currently restricted to tropical areas, are not found in the area after the Calabrian possibly because of the disappearance of the psychrosphere. The extant Mediterranean echinoid fauna mainly derives from the Late Miocene fauna, reduced after several climatic changes by about 43% at the genus level. The recent increase of the sea surface temperatures allowed the entrance of the Lessepsian Diadema setosum and confined the deep-water species of Holanthus to the coldest areas of the basin, making this genus endangered. [ABSTRACT FROM AUTHOR]

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.

A new quasimetric approach is used to statistically analyze taphonomic data from a commonly occurring shallow water clypeasteroid echinoid in order to obtain metric equivalent measurements of taphonomic alteration on an interval-like scale. This technique takes the character condition as well as its proportion into account and translates the taphonomic alteration into data, which behave as interval scaled and thus allows for the use of parametric as well as non-parametric statistics. Tests of Echinocyamus pusillus from Giglio Island (Mediterranean Sea, Italy) were analyzed with respect to a suite of taphonomic features including abrasion of the test surface, tubercles, ambulacral and genital pore margins as well as, if present, the outline and cross section of predatory drillholes. The degree of fragmentation and encrustation was also determined. Taphonomic features were analyzed using a semi-quantitative approach with three degrees of test alteration including non-altered, moderately altered, and highly altered which were statistically analyzed using non-parametric statistics due to highly non-normal distributed data. Abrasion intensities vary among different surface characters, with exposed areas of the test showing higher abrasion intensities than sheltered areas. Fragmentation occurs in low frequencies (7%) and fractures in the tests are almost absent (1.7%). Encrustation rates by bryozoans and serpulids can cover up to 80% of the test surface, but vary strongly among individuals and sample sites. Encrustation is independent of test size and prolongs overall test survival by crossing plate boundaries. The presence of drillholes in decreasing test preservation potentials is discussed with respect to analytical parameters.

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]

A new quasimetric approach is used to statistically analyze taphonomic data from a commonly occurring shallow water clypeasteroid echinoid in order to obtain metric equivalent measurements of taphonomic alteration on an interval-like scale. This technique takes the character condition as well as its proportion into account and translates the taphonomic alteration into data, which behave as interval scaled and thus allows for the use of parametric as well as non-parametric statistics. Tests of Echinocyamus pusillus from Giglio Island (Mediterranean Sea, Italy) were analyzed with respect to a suite of taphonomic features including abrasion of the test surface, tubercles, ambulacral and genital pore margins as well as, if present, the outline and cross section of predatory drillholes. The degree of fragmentation and encrustation was also determined. Taphonomic features were analyzed using a semi-quantitative approach with three degrees of test alteration including non-altered, moderately altered, and highly altered which were statistically analyzed using non-parametric statistics due to highly non-normal distributed data. Abrasion intensities vary among different surface characters, with exposed areas of the test showing higher abrasion intensities than sheltered areas. Fragmentation occurs in low frequencies (7%) and fractures in the tests are almost absent (1.7%). Encrustation rates by bryozoans and serpulids can cover up to 80% of the test surface, but vary strongly among individuals and sample sites. Encrustation is independent of test size and prolongs overall test survival by crossing plate boundaries. The presence of drillholes in decreasing test preservation potentials is discussed with respect to analytical parameters. [ABSTRACT FROM AUTHOR]

Based on new material from Germany and Spain, the echinoid "Lepidocentrus" ibericus from the Early Devonian (Emsian) of northern Spain is shown to be congeneric with Rhenechinus from the Hunsrück Slate of south-western Germany. New information on the lantern, pedicellariae and internal structure of the theca is provided, and confirms this genus as a member of the Echinocystitidae-Proterocidaridae clade and the most primitive of all Devonian echinoids. The two environmental settings in which Rhenechinus is found are very different: the Spanish specimens come from a relatively shallow-water bryozoan meadow setting while the German specimens are preserved in a deep-water setting. We deduce that the rare echinoid specimens from the Hunsrück Slate are all allochthonous, whereas the Spanish material is preserved in situ. [ABSTRACT FROM AUTHOR]