A new prospect in crinoid (Crinoidea, Echinodermata) research: an example from the Lower Jurassic of Montenegro

Lower Jurassic (Hettangian-Pliensbachian) shallow-marine ooidal limestones of southern Montenegro contain a large number of isocrinid ossicles. They are assigned to the following taxa: Iso-crinus psilonoti (QUENSTEDT), Isocrinus sp., and Pentacrinites cf. fossilis BLUMENBACH. The echinoderm assemblage also yields cyrtocrinid ossicles (Cotylederma sp., Cyrtocrinina indet.) and echinoid spines (only spotted in thin sections); however, these elements are rare. Given the fact that the recorded assemblage comes from a single locality, there is a growing need for further research that will require intense sampling to compile and complete the faunal list of crinoids and other echinoderm taxa

Late Cretaceous crinoids (Echinodermata) from the southwestern margin of the Holy Cross Mts. (southern Poland) and phylogenetic relationships among bourgueticrinids

A systematic account of crinoids from the Upper Coniacian–Lower Campanian of the southwestern margin of the Holy Cross Mountains in southern Poland is presented. Seven crinoid taxa [Marsupites testudinarius (von Schlotheim), Bourgueticrinus ellipticus (Miller), Bourgueticrinus sp., I.? granosus Valette, Isocrinus? sp., Nielsenicrinus carinatus Roemer and Austinocrinus bicoronatus (von Hagenow)] are described and illustrated. The new material from Poland extends down the stratigraphic range of Austinocrinus bicoronatus to the Lower Campanian. Morphometric data support that Bourgueticrinus ellipicus and B.? suedicus are conspecific. Taphonomy and paleoecology of recorded crinoid assemblages are discussed. Phylogeny of Cretaceous bourgueticrinids is also revisited

Comment on „palaeoenvironmental control on distribution of crinoids in the bathonian (middle jurassic) of England and France” by Aaron W. Hunter and Charlie J. Underwood

Aaron W. Hunter and Charlie J. Underwood in their article published in Acta Palaeontologica Polonica (Hunter and Underwood 2009) present some interesting results regarding facies control on the distribution of certain crinoids in the Bathonian of England and France. This is an important contribution, but we feel necessary to comment on some issues raised in their paper

Experimental tumbling of Dreissena polymorpha : implications for recognizing durophagous predation in the fossil record

Shell damage left by predators constitutes an important source of information on predator–prey interactions. However, recognition of the origins of shell damage can often be controversial, and needs to be assessed cautiously. More specifically, differentiation between predation- and abiotic-induced shell damage remains challenging. Here, we show the results of tumbling experiments using a bivalve species Dreissena polymorpha in order to determine rates and patterns of shell damage induced by physical forces in high-energy conditions. It is demonstrated that, in contrast to durophagous fish and crab predation, abiotic-induced fragmentation and damage are typically characterized by the presence of distinct abrasive scratches and wear scars on the surface of shell fragments. Furthermore, fragmented shells typically reveal a wide size distribution, and a different degree of sphericity and roundness resulting from abrasion. Importantly, large shell fragments commonly display smooth edges. These data suggest that durophagous predation, which typically induces fragmentation into large and angular shell fragments bearing no wear scars, can be reliably recognized both in present-day environments and in the fossil record

Reassessing the improbability of a muscular crinoid stem

Muscular articulations in modern stalked crinoids are only present in the arms. Although it has been suggested that certain coiled-stemmed fossil taxa may have been functionally adapted to utilize muscles, evidence supporting this interpretation is lacking. Here, we use cathodoluminescence and SEM to reveal the skeletal microstructure of the enigmatic coiled-stemmed taxon Ammonicrinus (Flexibilia). Based on the well-established link between skeletal microstructure and the nature of infilling soft tissues in modern echinoderms, we reconstructed the palaeoanatomy of the Middle Devonian ammonicrinids. We show that their median columnals with elongated lateral columnal enclosure extensions (LCEE) have stereom microstructure unexpectedly resembling that in the crinoid muscular arm plates. In particular, large ligamentary facets, that are present on each side of a transverse ridge, are mainly comprised of fine galleried stereom that is indicative of the mutable collagenous tissues. In contrast, fine labyrinthic stereom, commonly associated with muscles, is situated in the periphery on each side of the surface of elongated LCEE. Our findings thus strongly suggest that the muscles may have also been present in the stem of ammonicrinids. These results reassess the previous hypotheses about evolution of muscles in crinoids and provide new insights into the mode of life of Ammonicrinus

Body-size increase in crinoids following the end-Devonian mass extinction

The Devonian period ended with one of the largest mass extinctions in the Earth history. It comprised a series of separate events, which eliminated many marine species and led to long-term post-extinction reduction in body size in some groups. Surprisingly, crinoids were largely unaffected by these extinction events in terms of diversity. To date, however, no study examined the long-term body-size trends of crinoids over this crucial time interval. Here we compiled the first comprehensive data sets of sizes of calyces for 262 crinoid genera from the Frasnian-Visean. We found that crinoids have not experienced long-term reduction in body size after the so-called Hangenberg event. Instead, size distributions of calyces show temporal heterogeneity in the variance, with an increase in both the mean and maximum biovolumes between the Famennian and Tournaisian. The minimum biovolume, in turn, has remained constant over the study interval. Thus, the observed pattern seems to fit a Brownian motion-like diffusion model. Intriguingly, the same model has been recently invoked to explain morphologic diversification within the eucladid subclade during the Devonian-early Carboniferous. We suggest that the complex interplay between abiotic and biotic factors (i.e., expansion of carbonate ramps and increased primary productivity, in conjunction with predatory release after extinction of Devonian-style durophagous fishes) might have been involved not only in the early Mississippian diversity peak of crinoids, but possibly also in their overall passive expansion into larger body-size niches

Drill Holes and Predation Traces versus Abrasion-Induced Artifacts Revealed by Tumbling Experiments

Drill holes made by predators in prey shells are widely considered to be the most unambiguous bodies of evidence of predator-prey interactions in the fossil record. However, recognition of traces of predatory origin from those formed by abiotic factors still waits for a rigorous evaluation as a prerequisite to ascertain predation intensity through geologic time and to test macroevolutionary patterns. New experimental data from tumbling various extant shells demonstrate that abrasion may leave holes strongly resembling the traces produced by drilling predators. They typically represent singular, circular to oval penetrations perpendicular to the shell surface. These data provide an alternative explanation to the drilling predation hypothesis for the origin of holes recorded in fossil shells. Although various non-morphological criteria (evaluation of holes for non-random distribution) and morphometric studies (quantification of the drill hole shape) have been employed to separate biological from abiotic traces, these are probably insufficient to exclude abrasion artifacts, consequently leading to overestimate predation intensity. As a result, from now on, we must adopt more rigorous criteria to appropriately distinguish abrasion artifacts from drill holes, such as microstructural identification of micro-rasping trace

Cretaceous Roveacrinids from Mexico revisited: Overcoming the taxonomic misidentifications and subsequent biostratigraphic abuse

The Mesozoic carbonate deposits of Mexico yield a number of overlooked, ill-known, and even enigmatic microfossils, among which are roveacrinoids (Echinodermata, Crinoidea, Roveacrinida). Most of these pelagic organisms probably came from the central Tethysian seaways, and later on from the early central Atlantic Ocean through the northwestern Tethysian neck, thus reaching the Central American platforms (Comanchean shelf, Central Texas platform, and Coahuila platform) and the Western Interior seaway. The present work intends to enlist as comprehensively as possible the Mexican records of roveacrinid crinoids, to propose a revised interpretation of the sections illustrated (most of them being originally erroneously assigned) and to provide a sound data base for further systematic and biostratigraphic research

A regurgitalite of the Middle Triassic (Muschelkalk) from Upper Silesia (Poland)

A bromalite from the Middle Triassic (Muschelkalk) of southern Poland, Sadowa Góra Quarry, is herein described and interpreted as a regurgitalite. The fossils occurring within the regurgitalite are angular and have sharp edges. They are represented by common fragments of thin-shelled bivalves as well as rare crinoid and gastropod remains. The composition of the collected inclusion is different from that of the host rock. There are many candidates that could have produced the regurgitalite, including durophagous sharks, marine reptiles, the actinopterygian Colobodus, or nautiloids. Our finding adds to the emerging evidence of durophagous predation in the Triassic sea of Polish part of the Germanic Basin. It is the second record of a regurgitalite from the Muschelkalk of Upper Silesia

Ophiuroids from the Middle Triassic (Muschelkalk) of Sadowa Góra, Jaworzno (southern Poland)

Ophiuroids belonging to Aspiduriella sp., Aspiduriella similis (Eck), and Arenorbis sp. are described from the Middle Triassic (Muschelkalk) strata of the Sadowa Góra Quarry (Jaworzno) in southern Poland. This is the only Polish location where three taxa of these ophiuroids have been found in one stratigraphic horizon (1st Wellenkalk). To date, only single taxa have been found in the Triassic sections of the eastern part of the Germanic Basin. Finally, other ophiuroid mass aggregations also known from Poland are presented