Crinoid Ossicles Research Articles

Heritage Stone 9. Tyndall Stone, Canada’s First Global Heritage Stone Resource: Geology, Paleontology, Ichnology and Architecture

Tyndall Stone is a distinctively mottled and strikingly fossiliferous dolomitic limestone that has been widely used for over a century in Canada, especially in the Prairie Provinces. It comprises 6–8 m within the lower part of the 43 m thick Selkirk Member of the Red River Formation, of Late Ordovician (Katian) age. It has been quarried exclusively at Garson, Manitoba, 37 km northeast of Winnipeg, since about 1895, and for the past half-century extraction has been carried out solely by Gillis Quarries Ltd. The upper beds tend to be more buff-coloured than the grey lower beds, as a result of groundwater weathering. Tyndall Stone, mostly with a smooth or sawn finish, has been put to a wide variety of uses, including exterior and interior cladding with coursed and random ashlar, and window casements and doorways. Split face finish and random ashlar using varicoloured blocks split along stylolites have become popular for commercial and residential buildings, respectively. Tyndall Stone lends itself to carving as well, being used in columns, coats of arms and sculptures. Many prominent buildings have been constructed using Tyndall Stone, including the provincial legislative buildings of Saskatchewan and Manitoba, the interior of the Centre Block of the House of Commons in Ottawa, courthouses, land titles buildings, post offices and other public buildings, along with train stations, banks, churches, department stores, museums, office buildings and university buildings. These exhibit a variety of architectural styles, from Beaux Arts to Art Deco, Châteauesque to Brutalist. The Canadian Museum of History and the Canadian Museum for Human Rights are two notable Expressionist buildings. The lower Selkirk Member is massive and consists of bioturbated, bioclastic wackestone to packstone, rich in crinoid ossicles. It was deposited in a low-energy marine environment within the photic zone, on the present-day eastern side of the shallow Williston Basin, which was part of the vast equatorial epicontinental sea that covered much of Laurentia at the time. Scattered thin bioclastic grainstone lenses record episodic, higher energy events. Tyndall Stone is spectacularly fossiliferous, and slabs bearing fossils have become increasingly popular. The most common macrofossils are receptaculitids, followed by corals, stromatoporoid sponges, nautiloid cephalopods, and gastropods. The relative abundance of the macrofossils varies stratigraphically, suggesting that subtle environmental changes took place over time. The distinctive mottles—‘tapestry’ in the trade—have been regarded as dolomitized burrows assigned to Thalassinoides and long thought to have been networks of galleries likely made by arthropods. In detail, however, the bioclastic muddy sediment underwent a protracted history of bioturbation, and the large burrows were mostly horizontal back-filled features that were never empty. They can be assigned to Planolites. The matrix and the sediment filling them were overprinted by several generations of smaller tubular burrows mostly referrable to Palaeophycus due to their distinctive laminated wall linings. Dolomite replaced the interiors of the larger burrows as well as smaller burrows and surrounding matrix during burial, which is why the mottling is so variable in shape.

Carbonate diagenesis: A celebration of the work of John Anthony Dawson (Tony) Dickson

Carbonate diagenesis: A celebration of the work of John Anthony Dawson (Tony) Dickson

Clumped isotope analysis of zoned calcite cement, Carboniferous, Isle of Man

AbstractSequential analyses of δ13C, δ18O and Δ47 values of calcite and dolomite deposited in millimetre‐sized cavities are reported from the Ronaldsway Member packstones, Isle of Man. The Ronaldsway brachiopods have δ13C values of ca +2.3‰ and δ18O values of ca −7.2‰; carbon is like predicted Carboniferous values, while oxygen values are more negative. The brachiopods show preserved microstructure but have marginal alteration and a streaky cathodoluminescence pattern. Crinoid ossicles have δ13C values of ca +2.3‰ and one with a δ18O value of ca −3.1‰, compatible with Carboniferous marine precipitates; three samples have δ18O values of ca −6.5‰ and are 18O‐depleted. Calcite stages 1 and 2 have δ13C values ca +3.2‰ and δ18O values ca −2.5‰, compatible with Carboniferous sea water. Stage 1 and 2 have non‐luminescent to orange CL zones. Stage 1 and early stage 2 contain red luminescent dolomite micro crystals generated during Mg calcite stabilisation. The Δ47 values for stage 1 and 2 cements indicate temperatures of 86 and 105°C that occurred after the stabilisation of Mg calcite. Stage 3–8 zoned cements preserve their original growth surfaces and their δ13C and δ18O values suggest precipitation during burial and exhumation. The Δ47 values of the brachiopods and crinoids indicate temperatures between 85 and 140°C indicating they were either recrystallised at high temperatures or affected by solid state reordering. To evaluate these alternatives two quantitative models, water–rock reaction and reordering models are performed. The allochems and cements are progressively altered by porewater towards the fluid‐buffered behaviour. The quantitative evaluation of calcite and dolomite solid‐state reordering suggests the elevated clumped isotopic temperatures are produced by interaction with hydrothermal fluids. This study improves understanding by applying previously untried techniques; further Δ47 data and quantifying elemental variations would help further interpretation but the poorly documented post‐depositional history is a drawback.

Dendritické vrtby v miskách ramenonožců ze středního devonu (eifelu) pražské pánve (Barrandien, Česká republika)

Three ichnospecies of dendritic borings (Clionolithes cf. cervicornis, C. isp. A, and C. isp. B) were observed in abundant brachiopod shells in the Třebotov Formation (lowermost Eifelian, zone Polygnathus partitus) in two Prague localities (Praha-Holyně, “V rokli”, and Praha-Barrandov, street “K Barrandovu”). Borings are generally small-sized, of about 1 mm, but they can reach up to 4 mm. Borings are preserved inside thick translucent walls of brachiopods smooth shells (Trigonatrypa holynensis, Xenomartinia monoseptoides and Clorinda sp.). Borings are very frequent (almost in all examined shells), but never pass through a whole wall thickness of a brachiopod. Two or even more borings, commonly of a different type, are preserved on an individual shell. Both valves of articulated specimen may be bored, while the shell interior is devoid of borings neither shows any response to the boring activity such as uneven internal biomineralization. Majority of tunnels bores inside the shell wall, and the borings are opened by small irregular central pit. As more than a half of examined shells were infected, bioerosion likely had a negative impact on the shell preservation. Our study shows that the brachiopod infestation was selective. Only thick calcitic shells were bored, while thinner shells or exopunctate brachiopods (Holynatrypa, Peridalejina, Prokopia) were not a target of the borers. Similarly, crinoid and other echinoderm ossicles do not show any signs of a boring. A different dendritic boring referred to as Clionolithes radicans was observed on a shell of brachiopod coming from the Acanthopyge Limestone (Choteč Formation, Eifelian) from Zadní Kobyla locality near Koněprusy. The stellate trace is substantially larger (4.3 mm × 2.8 mm) than borings from the Třebotov Limestone, with deep and externally open canals. Borings from the Třebotov Limestone come from so-called “white beds”. These soft beds originated by weathering of a hard limestone, leaving loose generally small bioskeletal remains of echinoderms, gastropods, brachiopods, ostracods, dacryoconarids and other invertebrate groups. Dacryoconarid shells and crinoid ossicles dominate. The life assemblage occupied a deeper weakly hypoxic perireef environment below the fotic zone. The dendritic boring from the Acanthopyge Limestone comes from a completely different environment. Associated diverse and generally large brachiopods, fragmented fenestrate bryozoans and abraded tabulate and rugose corals (including Calceola sandalina) indicate a shallow-water highenergy reef environment. This is the first report of dendritic borings from the Eifelian of the Prague Basin. It confirms not only so far unknown presence of their borers in the area, but also reveals that their activity can be observed in the weakly lithified Devonian limestones in the area.

An Early Triassic small shelly fossil-style assemblage from the Virgin Limestone Member, Moenkopi Formation, western United States

Small shelly fossils (SSFs) are minute fossils moulded or replaced by apatite, and less commonly, other minerals like glauconite and iron oxides. This taphonomic mode is best known from Cambrian deposits, though some occurrences occur across geological time. Instances of small shelly-style preservation were found in insoluble residues from the Lower Triassic Virgin Limestone Member exposed in southern Nevada, the western United States, a second such occurrence known from this unit. Fossil steinkerns of tiny brachiopods, echinoid spines and ophiuroids are fluorapatite, with scarce phosphatic internal moulds of bivalves and two replaced ostracods. In contrast, the crinoid ossicles, almost all of which are >1000 µm, are preserved as stereomic moulds of silica or dolomite. Though the style of preservation is similar to another Virgin Limestone small shelly fossils-style assemblage, this assemblage preserves greater diversity, likely reflecting the variation in palaeocommunities across the shelf. The size selectivity of phosphatization is clear, as the majority of the fossils <1000 µm are phosphatized. Importantly, the original skeletal material does not exert the strongest control on style of preservation: crinoid ossicles are replaced or moulded by silica whilst ophiuroid and echinoid fragments are phosphatized. It is likely that the underlying phosphatization mechanisms are related to the small particle size of the skeletons or skeletal elements coupled with the local pore water environment. Early Triassic equatorial seas characterized by warm temperatures and lower oxygen levels likely fostered small shelly fossil-style preservation across the shelf during this time.

PALEOENVIRONMENTAL AND BIOSTRATIGRAPHIC IMPLICATIONS OF ECHINODERM OSSICLES TRAPPED WITHIN BURMESE AMBER

ABSTRACT Marine organisms are uncommonly preserved in amber. Recently, they were reported to be associated with Burmese amber. However, most of specimens from previous reports were preserved on the amber surface or within the sediment surrounding the amber. Based on X-ray tomography and thin-section optical microscopy of Burmese amber, we report here the first genuine and unambiguous evidence of inclusion of crinoid ossicles preserved in the fossil resin. Preservation of this exclusively marine group in amber gives insights into the paleoenvironment of the crinoid-amber association and provides additional evidence to support previous observations of shallow-water stalked crinoids from the mid-Cretaceous, when many stalked crinoids started to shift offshore due to increased predation pressure during the Mesozoic Marine Revolution. Crinoid remains, represented by disarticulated stem and arm ossicles assignable to Isocrinus cf. legeri (Repelin), point to a mid-Cretaceous age for the Burmese amber and support some previous hypotheses suggesting a close proximity between the resin-producing trees and seawater.

New data from Oman indicate benthic high biomass productivity coupled with low taxonomic diversity in the aftermath of the Permian–Triassic Boundary mass extinction

A new Early Triassic marine fauna is described from an exotic block (olistolith) from the Ad Daffah conglomerate in eastern Oman (Batain), which provides new insights into the ecology and diversity during the early aftermath of the Permian–Triassic Boundary mass extinction. Based on conodont quantitative biochronology, we assign a middle Griesbachian age to the upper part of this boulder. It was derived from an offshore seamount and yielded both nektonic and benthic faunas, including conodonts, ammonoids, gastropods and crinoid ossicles in mass abundance. This demonstrates that despite the stratigraphically near extinction at the Permian–Triassic Boundary, Crinoidea produced enough biomass to form crinoidal limestone as early as middle Griesbachian time. Baudicrinus, previously placed in Dadocrinidae, is now placed in Holocrinidae; therefore, Dadocrinidae are absent in the Early Triassic, and Holocrinidae remains the most basal crown-group articulates, originating during the middle Griesbachian in the Tethyan Realm. Abundant gastropods assigned to Naticopsis reached a shell size larger than 20 mm and provide another example against any generalized Lilliput effect during the Griesbachian. Whereas the benthic biomass was as high as to allow the resumption of small carbonate factories, the taxonomic diversity of the benthos remained low compared to post-Early Triassic times. This slow benthic taxonomic recovery is here attributed to low competition within impoverished post-extinction faunas.

Notes on Additional Material Associated with the Type Specimens of Diphuicrinus ohioensis (Echinodermata: Crinoidea) from the Middle Pennsylvanian of Southeastern Ohio

The cladid crinoid Diphuicrinus ohioensis Burke, 1976, was originally described from shallow marine facies of the Middle Pennsylvanian Putnam Hill Limestone of southeastern Ohio. One of the type localities for this taxon is an abandoned quarry in Vinton County, where a small number of articulated cups used in erection of this species was collected. Prior to formal description of this species, multiple isolated calyx ossicles were collected from this locality, but were not analyzed in detail or included in the description of D. ohioensis. The previously unidentified material, described herein, contributes to a more complete record of this taxon. Further, heavily sculptured (nodose) basal and radial plates are nearly ubiquitously encrusted by calcareous tubes, a paleoecological detail not otherwise noted in the description of D. ohioensis or the lithofacies from which material was collected. Encrusters, which consist of at least 2 varieties, are present primarily in depressed areas in between raised nodes. This may reflect post-mortem removal via abrading currents but may alternatively represent preferential encrustation of portions of hard bioclasts characterized by larger, smoother, protected surfaces. This study reinforces the value of isolated crinoid ossicles in paleoecology, paleobiology, and paleoenvironmental analysis.

Late Ordovician (Hirnantian) diploporitan fauna of Anticosti Island, Quebec, Canada: implications for evolutionary and biogeographic patterns

Hirnantian (latest Ordovician) localities containing echinoderm fossils are rare; the few that have been discovered primarily contain disarticulated crinoid ossicles. Therefore, relatively little is known about echinoderm evolutionary dynamics across the Late Ordovician – early Silurian boundary, especially noncrinoid echinoderms. New diploporitan echinoderms, Holocystites salmoensis and an unidentified holocystitid, from reefal facies of the Upper Ordovician Ellis Bay Formation of Anticosti Island provide a critical data point concerning diploporitan biogeography and evolutionary pathways undertaken during the Ordovician and Silurian. These fossils also provide a crucial link in understanding the ancestry of the Silurian Holocystites Fauna, an unusual diploporitan fauna from the middle Silurian of North America, whose origination dates back at least 15 million years earlier than previously thought with the discovery of taxa described here. New fossil data such as these stress the importance of uncovering new localities from underrepresented times and places in Earth’s history, so that these evolutionary transitions can be better understood.

Discovery of the Early Spathian (Late Olenekian, Early Triassic) AmmonoidTirolitesin the Hiraiso Formation, South Kitakami Belt, Northeast Japan

Abstract. Until now, the Hiraiso Formation was considered to be entirely of Smithian (early Olenekian, Early Triassic) age, but the discovery of the ammonoid Tirolites cf. ussuriensis in the lower part of the formation on the rocky coast between the Maekawara and Akaushi ports, Motoyoshi Town, Kesennuma City, in the South Kitakami Belt, Northeast Japan, establishes that this portion is actually equivalent to the upper part of the lower Spathian Tirolites-Amphistephanus Zone (upper Olenekian). The fauna of the Hiraiso Formation, which includes the large bivalve Eumorphotis iwanowi and crinoid ossicles, very much resembles the Tirolites ussuriensis beds in South Primorye, Russian Far East, suggesting a wide distribution of this shallow marine fauna in the low to middle northern latitudes on the western side of the Panthalassa during the early Spathian. Because pre-Spathian deposits contain only small-sized species of Eumorphotis and very rare crinoid ossicles, the appearance of large species of Eumorphotis ...

Geology: In All Modesty

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Fossil crinoids from the Valley of Rocks, Lynton, north Devon (Devonian)

Disarticulated crinoid ossicles, particularly columnals, from the Devonian of south-west England are locally common, but incompletely known; most studies have been in the 21st Century. A new collection of mouldic crinoid ossicles from the Lynton Formation (Lower/Middle Devonian) of the Valley of Rocks, west of Lynton, is rich in columnals of the monobathrid camerate Hexacrinites sp. D, represented by many hundreds of specimens. This is the first record of proximal columnals of Hexacrinites from the type area of the Devonian. A columnal of the cladid Cupressocrinites sp. is a rare example of a widely distributed Devonian genus; this is the oldest specimen known from the British Isles. Broad columnals of Annulocolumnus (col.) sp. A. annulus Donovan have a primitive morphology, with a wide lumen, more reminiscent of a Lower Ordovician taxon. Pentagonocyclicus (col.) sp. is a robust example of a widely distributed Palaeozoic morphotaxon. Elliptical brachials with synarthrial articulations (cladids?) are reminiscent of columnals of platycrinitid camerate crinoids. A radice ossicle with a figure-of-eight lumen is reminiscent of roots from the Silurian of Sweden. Taken together, these identifications indicate that our knowledge of the Devonian crinoids of south-west England remains incomplete in an area where few new collections have been made since the 19th Century.

Micro‐ to nanostructure and geochemistry of extant crinoidal echinoderm skeletons

This paper reports the results of micro- to nanostructural and geochemical analyses of calcitic skeletons from extant deep-sea stalked crinoids. Fine-scale (SEM, FESEM, AFM) observations show that the crinoid skeleton is composed of carbonate nanograins, about 20-100 nm in diameter, which are partly separated by what appears to be a few nm thick organic layers. Sub-micrometre-scale geochemical mapping of crinoid ossicles using a NanoSIMS ion microprobe, combined with synchrotron high-spatial-resolution X-ray micro-fluorescence (μ-XRF) maps and X-ray absorption near-edge structure spectroscopy (XANES) show that high Mg concentration in the central region of the stereom bars correlates with the distribution of S-sulphate, which is often associated with sulphated polysaccharides in biocarbonates. These data are consistent with biomineralization models suggesting a close association between organic components (including sulphated polysaccharides) and Mg ions. Additionally, geochemical analyses (NanoSIMS, energy dispersive spectroscopy) reveal that significant variations in Mg occur at many levels: within a single stereom trabecula, within a single ossicle and within a skeleton of a single animal. Together, these data suggest that physiological factors play an important role in controlling Mg content in crinoid skeletons and that great care should be taken when using their skeletons to reconstruct, for example, palaeotemperatures and Mg/Ca palaeo-variations of the ocean.

Crinoids from the Middle Jurassic (Bajocian–Lower Callovian) of Ardèche, France

Several Middle Jurassic outcrops in the Ardeche Department near La Voulte-sur-Rhone and St-Etienne-de-Boulogne are rich in the remains of crinoids, but these were known from surface collections only and were not described using present standards of systematics. This paper brings the taxonomic status of the previously described crinoids up to date, reassesses the systematic position of some of the species based on cups and describes new forms. Sampling and washing of bulk material from the Lower Bathonian of the La Pouza locality yielded nearly 100,000 crinoid ossicles. Among them are rare comatulids with the following recognized as new: Andymetragalei n. g., n. sp., Palaeocomaster messingi n. sp., Singillatimetra inordinata n. g., n. sp. and Solanocrinitesvoultensis n. sp. These forms supplement the meagre record of Middle Jurassic comatulids and indicate that this group radiated well before the Late Jurassic. The Cyrtocrinida constitute the bulk of the crinoids and they are dominated by Cyrtocrinus praenutans n. sp. from which nearly all parts of the skeleton are described in their morphological variability. The La Pouza site furnished the additional new cyrtocrinids, Praetetracrinus bathonicus n. sp. and Phyllocrinusvoultensis n. sp. The material also includes numerous remains of the isocrinids Isocrinus dumortieri (de Loriol), Balanocrinus dumortieride Loriol, Balanocrinus pacomeide Loriol and Balanocrinus inornatus (d’Orbigny), which are described in some detail, including brachials. From the Upper Bajocian–Lower Bathonian locality of Pont des Etoiles, Pentacrinites ausichi n. sp. and the cyrtocrinid Scutellacrinus tenuis n. g., n. sp. are new to science. The results demonstrate that the Middle Jurassic crinoids from the Ardeche are one of the important and diverse Mesozoic crinoid faunas. Some forms bridge the gap between the Early Jurassic and the Late Jurassic hardground faunas of cyrtocrinids. Cyrtocrinus praenutans n. sp., a form similar to Cyrtocrinus nutans (Goldfuss) from the Oxfordian, is described as a separate species despite some overlapping phenotypic variability of cups and columnals. Pathological deformations on all types of ossicles of C. praenutans n. sp. are ascribed to the epizoan commensal Oichnus paraboloides Bromley. Different species are dominant at the different Bathonian localities, namely C. praenutans n. sp. at La Pouza and Phyllocrinus fenestratus (Dumortier) and Lonchocrinus dumortieri (de Loriol) at La Clapouze. Preservation and rock formation of the Upper Bajocian–Lower Bathonian Isocrinus nicoleti (Thurmann) at Pont des Etoiles suggests that this form lived in rather shallow and turbulent water. The dominance of cyrtocrinids and the presence of all growth stages and parts of the skeleton at La Pouza and La Clapouze suggest a deeper palaeoenvironment, with some transport of the ossicles.

Bromalites from the Middle Triassic of Poland and the rise of the Mesozoic Marine Revolution

Durophagous predation has been an important cause of significant evolutionary changes in the history of life. One of the most dramatic predation-driven changes in marine ecosystems occurred during the middle and late Mesozoic, which has been called the Mesozoic Marine Revolution (MMR). At this time, diversification of various predators elicited many escalation-related adaptations among prey taxa including trends toward infaunalization, elaboration of armor shells, and environmental restriction. However, the rise of this phenomenon has been the source of considerable debate. Initially, it has been argued that these major evolutionary changes began in the Jurassic and continued to accelerate in the Cretaceous. Although recent reports have shown that the MMR may have actually started soon after the end-Permian extinction in some groups, Triassic records of predation on benthic organisms are still very scant. Here, we report several bromalites (most probably regurgitalites) from the Middle Triassic of the Gogolin Formation, Upper Silesia, southern Poland. They are in a form of distinct and packed accumulations of intermingled fossil remains composed primarily of various angular bivalve shell fragments with sharp, non-abraded margins as well as crinoid ossicles with common signs of breakage. These dispersions of material are up to 99mm in maximum diameter. It is suggested that these accumulations represent orally ejected waste produced by durophagous animals, most probably by durophagous sharks, colobodontid fish, placodonts, and some pachypleurosaurs or sauropterygian reptiles. All of these taxa have been recorded in the Middle Triassic of Poland. The feasibility of these vertebrates as potential agents of the present bromalites is discussed. We suggest that many morphological and behavioral innovations in the Triassic gastropods, bivalves and crinoids are escalation-related adaptations to durophagous predators and that the Mesozoic Marine Revolution was a far more prolonged evolutionary event than its name indicates.

A lost world? Archaic crinoid-dominated assemblages on an Antarctic seamount

The previously unsurveyed Admiralty (67°S, 171°E) and Scott Island (67°22′S, 179°55′E) seamounts to the north of the Ross Sea were explored using cameras and physical sampling gear during the New Zealand IPY-CAML research voyage (TAN0802) in February 2008. A striking assemblage dominated by stalked crinoids and brachiopods was found at 580–600 m depths on isolated knolls at the northwest and southeast extremities of Admiralty Seamount. The seabed at these sites was littered with crinoid ossicles, and crinoid stalk bases were conspicuous on exposed rocks, suggesting that these assemblages have persisted for a considerable period of time. The crinoid sites were limited to the isolated knolls but large areas of the flanks of the main seamount were covered by dense populations of suspension-feeding ophiuroids. These assemblages are more similar in structure to those preserved in fossil strata from the Palaeocene and late Eocene than to any extant assemblages yet described from the Antarctic. In comparisons with faunal assemblages on Scott Island seamount, the abundance of stalked crinoids was strongly inversely correlated with the abundance of echinoid, asteroid, and lithodid crab predators and both asteroids and echinoids were photographed feeding on crinoids. These observations are consistent with the prevailing hypotheses that crinoid- and ophiuroid-dominated assemblages, which were widespread in the Palaeocene, were displaced by the radiation of mobile predators, and that conditions in isolated habitats in the Southern Ocean may have acted as refugia, allowing the persistence of archaic benthic assemblages.

Reconstructing the kinematic evolution of curved mountain belts: Internal strain patterns in the Wyoming salient, Sevier thrust belt, U.S.A.

Analyses of mesoscopic structural and strain patterns in red beds of the Triassic Ankareh Formation and limestones of the Jurassic Twin Creek Formation, in concert with complementary paleomagnetic studies, constrain the three-dimensional kinematic evolution of curved fold-and-thrust systems in the Wyoming salient of the Sevier thrust belt. Spaced cleavage, fracture and vein networks, minor folds, and minor faults in limestones and red beds accommodated early layer-parallel shortening (LPS) concentrated in front of the growing thrust wedge, along with minor strike-parallel extension and wrench shear related to the development of orogenic curvature. Strain, estimated using mass balance relations for cleavage seams, crinoid ossicles in bioclastic limestone, and reduction spots in red beds, displays systematic regional patterns. Principal shortening directions are subperpendicular to structural trend around the salient, reflecting a combination of primary curvature and secondary rotation of early LPS fabrics. LPS magnitudes vary from <5% in central parts of the frontal Hogsback thrust system, where cleavage is absent, to 10%–30% in the more interior Crawford thrust system, where cleavage intensity is moderate to strong; strain also increases toward the salient ends. Internal strain is a significant component of total deformation and should be considered when restoring cross sections. Strain patterns are consistent with a kinematic model involving curved fault slip and differential shortening that produced progressive secondary curvature during thrusting.

Nanostructural and Geochemical Features of the Jurassic Isocrinid Columnal Ossicles

Calcite isocrinid ossicles from the Middle Jurassic (Bathonian) clays in Gnaszyn (central Poland) show perfectly pre− served micro− and nanostructural details typical of diagenetically unaltered echinoderm skeleton. Stereom pores are filled with ferroan calcite cements that sealed off the skeleton from diagenetic fluids and prevented structural and geochemical alteration. In contrast with high−Mg calcite skeleton of modern, tropical echinoderms, the fossil crinoid ossicles from Gnaszyn contain only 5.0–5.3 mole% of MgCO3. This low Mg content can be a result of either a low temperature environ− ment (ca. 10C) and/or low Mg/Ca seawater ratio. Both conditions have been proposed for the Middle Jurassic marine en− vironment. Occurrence of Mg−enriched central region of stereom bars of Jurassic columnal ossicle of Chariocrinus an− dreae is consistent with the concept of magnesium ions involvement in earliest growth phases of calcium carbonate biominerals. Key wor ds: Echinodermata, Crinoidea, calcite, nanostructure, geochemistry, AFM, NanoSIMS, Jurassic.

Dimerelloid rhynchonellide brachiopods in the Lower Jurassic of the Engadine (Canton Graubünden, National Park, Switzerland)

New brachiopods (Dimerelloidea, Rhynchonellida) from Lower Jurassic (?lower Hettangian) hemipelagic sediments of the Swiss National Park in south-eastern Engadine are described: Sulcirostra doesseggeri sp. nov. and Carapezzia engadinensis sp. nov. Sulcirostra doesseggeri is externally similar to S. fuggeri (Frauscher 1883), a dubious species, that could not be included in a comparative study, because relevant samples no longer exist. A single specimen was tentatively assigned to Sulcirostra ?zitteli (Böse 1894) by comparison of its external morphology with S. zitteli from the type locality. The partly silicified brachiopods are associated with sponge spicules, radiolarians and crinoid ossicles. Macrofossils are rare: dictyid sponges, gastropods, bivalves, crustaceans, shark teeth and scales of an actinopterygian fish. The Lower Jurassic sediments (Alpisella beds, a basal member of the Allgäu Formation) preserving the brachiopods belong to the Ortler nappe (Upper Austroalpine nappes). The exact age of the Alpisella beds is not known, as index fossils are lacking. Their stratigraphic position above the Rhaetian Kössen Formation and below the ammonite-dated Trupchun beds suggests a very Early Jurassic, probably early Hettangian age for the new brachiopod fauna. The new species of Sulcirostra and Carapezzia are confined to a very small geographic area, a peculiarity also observed in other Early Jurassic dimerelloid brachiopods. These brachiopods presumably adapted to current-dominated submarine highs, where their shells could not accumulate, except when trapped in submarine cavities or re-deposited in submarine fans. Transport by turbidity currents is suggested for the Early Jurassic dimerelloids from the Engadine. Problems with the generic definition of Sulcirostra and the higher rank classification of Carapezzia are discussed.

Urchins in the meadow: paleobiological and evolutionary implications of cidaroid predation on crinoids

Deep-sea submersible observations made in the Bahamas revealed interactions between the stalked crinoidEndoxocrinus parraeand the cidaroid sea urchinCalocidaris micans.The in situ observations include occurrence of cidaroids within “meadows” of sea lilies, close proximity of cidaroids to several upended isocrinids, a cidaroid perched over the distal end of the stalk of an upended isocrinid, and disarticulated crinoid cirri and columnals directly underneath a specimen ofC. micans.Guts of twoC. micanscollected from the crinoid meadow contain up to 70% crinoid material. Two of three large museum specimens of another cidaroid species,Histocidaris nuttingi, contain 14–99% crinoid material.A comparison of cidaroid gut contents with local sediment revealed significant differences: sediment-derived material consists of single crinoid ossicles often abraded and lacking soft tissue, whereas crinoid columnals, cirrals, brachials, and pinnulars found in the cidaroids are often articulated, linked by soft tissue, and unabraded. Furthermore, articulated, multi-element fragments often show a mode of fracture characteristic of fresh crinoid material. Taken together, these data suggest that cidaroids prey on live isocrinids.We argue that isocrinid stalk-shedding, whose purpose has remained a puzzle, and the recently documented rapid crawling of isocrinids are used in escaping benthic predators: isocrinids sacrifice and shed the distal stalk portion when attacked by cidaroids and crawl away, reducing the chance of a subsequent encounter. If such predation occurred throughout the Mesozoic and Cenozoic (possibly since the mid-Paleozoic), several evolutionary trends among crinoids might represent strategies to escape predation by slow-moving benthic predators.