Notes on Mississippian echinoderms from Hurdlow,Derbyshire, central England

The fossil echinoderms of the Lower Carboniferous (Mississippian) of Derbyshire remain understudied, principally due to the nature of the preservation rather than any lack of biodiversity. Echinoids and crinoids are described in float blocks of limestone from near Hurdlow, Derbyshire, which have been etched naturally after many years of being washed by weakly acidic rain. Surface detail is variable, commonly poor, but rare specimens retain enough features for tentative identification. Two species of echinoids are identified from rare disarticulated plates, namely Melonechinus? sp. (ambulacral plates) and archaeocidarid sp. (interambulacral plate); more and superior material will be necessary to confirm this division. Crinoids include a cladid brachial ossicle sp. with a distinctive sculpture; a columnal of a monobathrid camerate platycrinitid sp.; Annulocolumnus (col.) sp. cf. A. annulus Donovan, a columnal morphotaxon with an unusually broad axial canal; and Cyclocyclicus (col.) spp. This is the tenth echinoid site to be recognized from the Mississippian of the White Peak. Examination of etched float blocks provides a further method of investigation of the echinoderm fauna of this and other limestone areas.     

Stock Evaluation of Three Littoral Echinoid Species on the Catalan Coast North-Western Mediterranean

Abstract. We estimated the abundances of the three common littoral echinoid species Paracentrotus lividus, Arbacia lixula and Sphaerechinus granularis in a littoral zone between 0 and 10m depth on the Catalan shores NE Spain. Densities of each species were estimated from a total number of 11 571× 1 m² sampling units deployed at 152 sites along the 13 zones into which the coast was divided. The surface area available in each of these zones was estimated at the scale of the sampling unit 1 m² taking into account the fractal dimension of the shore. The stocks individuals > 2cm test diameter of these species for the whole Catalan shore ≅ 300 km, straight-line distance were estimated to be about 279.1 × 10⁶ individuals for P. lividus , 28.9 × 10⁶ individuals for A. lixula and 10.9 × 10⁶ individuals for S. granularis. These sea-urchins are key species in the regulation of algal communities and some of them P. lividus. S. granularis are of commercial interest. This information will provide a tool for the future monitoring and management of this resource, which now faces diverse pressures of human origin.     

Turonian-Santonian echinoids from Wadi Qena,Eastern Desert,Egypt; a new arrangement of apical disc plating in spatangoids

Eighteen echinoid species (seven regular and eleven irregular) belonging to twelve genera have been described from the Turonian-Santonian succession of two sections located in the northern part of Wadi Qena, Eastern Desert. The diversity of the recorded species is low in the Turonian (six species), but comparatively high in the Coniacian-Santonian (twelve species). Of the recorded species, Most of these species (72%) are recorded for the first time from Wadi Qena area, one left in open nomenclature, Mecaster sp., represents a new species, and two, Phymosoma microtuberculatum and Thylechinus (T.) said, represent new records for Egypt. The taxonomic rank of Parapygus sudrensis has been changed. Phymosoma microtuberculatum which is known from the ‘Senonian’ of southwest Europe is recorded herein in the lower Turonian. Two echinoid assemblage zones are recognizable in each of the studied two sections. They are correlated with other fossil assemblage zones in Egypt. Faunal affinity and paleobiogeography of the species are discussed. A new arrangement of apical disc plating in spatangoids is described and discussed.     

Oceanographic controls on shallow‐water temperate carbonate sedimentation: Spencer Gulf,South Australia

Spencer Gulf is a large (ca 22 000 km²), shallow (<60 m water depth) embayment with active heterozoan carbonate sedimentation. Gulf waters are metahaline (salinities 39 to 47‰) and warm‐temperate (ca 12 to ?28°C) with inverse estuarine circulation. The integrated approach of facies analysis paired with high‐resolution, monthly oceanographic data sets is used to pinpoint controls on sedimentation patterns with more confidence than heretofore possible for temperate systems. Biofragments – mainly bivalves, benthic foraminifera, bryozoans, coralline algae and echinoids – accumulate in five benthic environments: luxuriant seagrass meadows, patchy seagrass sand flats, rhodolith pavements, open gravel/sand plains and muddy seafloors. The biotic diversity of Spencer Gulf is remarkably high, considering the elevated seawater salinities. Echinoids and coralline algae (traditionally considered stenohaline organisms) are ubiquitous. Euphotic zone depth is interpreted as the primary control on environmental distribution, whereas seawater salinity, temperature, hydrodynamics and nutrient availability are viewed as secondary controls. Luxuriant seagrass meadows with carbonate muddy sands dominate brightly lit seafloors where waters have relatively low nutrient concentrations (ca 0 to 1 mg Chl‐a m^?3). Low‐diversity bivalve‐dominated deposits occur in meadows with highest seawater salinities and temperatures (43 to 47‰, up to 28°C). Patchy seagrass sand flats cover less‐illuminated seafloors. Open gravel/sand plains contain coarse bivalve–bryozoan sediments, interpreted as subphotic deposits, in waters with near normal marine salinities and moderate trophic resources (0·5 to 1·6 mg Chl‐a m^?3) to support diverse suspension feeders. Rhodolith pavements (coralline algal gravels) form where seagrass growth is arrested, either because of decreased water clarity due to elevated nutrients and associated phytoplankton growth (0·6 to 2 mg Chl‐a m^?3), or bottom waters that are too energetic for seagrasses (currents up to 2 m sec^?1). Muddy seafloors occur in low‐energy areas below the euphotic zone. The relationships between oceanographic influences and depositional patterns outlined in Spencer Gulf are valuable for environmental interpretations of other recent and ancient (particularly Neogene) high‐salinity and temperate carbonate systems worldwide.     

Aspects of the marine Cretaceous of China

The marine Cretaceous of China is distributed mainly in southwestern Xinjiang, the West Kunlun Mountains, the Karakorum Mountains and most parts of Xizang (Tibet), with findings even from Taiwan.The marine Cretaceous of China may be divided into three sedimentary belts according to the lithologic and tectonic characters, biological provinces and the different modes of deposition.On the basis of recent research on the Cretaceous marine strata and faunas in China, the lithostratigraphic and biostratigraphic sequences have been preliminarily established and the division and correlation of strata and boundaries between the Jurassic and Cretaceous, Lower Cretaceous and Upper Cretaceous, as well as Cretaceous and Tertiary outlined; the position of the beach line of the Laurasian landmass in China and the events of the tectonic movement and the transgression and regression during the Cretaceous period are discussed.