Ordovician Crinoids Research Articles

Paleocommunity composition, relative abundance, and new camerate crinoids from the Brechin Lagerstätte (Upper Ordovician)

AbstractThe Brechin Lagerstätte of southern Ontario contains an exceptionally diverse and well-preserved Late Ordovician (Katian) crinoid fauna. We describe four genera and eight species of camerate crinoids from the Brechin Lagerstätte, including six new species. Consequently, the total diversity of the fauna now stands at 27 genera and 39 nominal species, thereby making it the most taxonomically diverse Ordovician crinoid fauna known. Taxa described include the diplobathrid Pararchaeocrinus kiddi new species and the monobathrids Glyptocrinus ramulosus Billings, 1856, Periglyptocrinus priscus (Billings, 1857a), Periglyptocrinus astricus new species, Periglyptocrinus kevinbretti new species, Periglyptocrinus mcdonaldi new species, Periglyptocrinus silvosus new species, and Abludoglyptocrinus steinheimerae new species. We summarize the taxonomic composition, diversity, and abundance distribution of all known crinoids from the Brechin Lagerstätte to better characterize the paleoecological structure and complexity of the community. We establish that the fauna is dominated by the subclass Pentacrinoidea, both in terms of abundance and species richness. In addition, we analyze species-level abundance data using Relative Abundance Distribution (RAD) models to evaluate the ecological complexity of the paleocommunity. We found that community structure of the Brechin Lagerstätte is best explained by an ecologically ‘complex’ RAD model, which suggests that species partitioned niches along multiple resource axes and/or the presence of multiple ecological ways of life. These results indicate that the Brechin Lagerstätte is significant not only for being the most taxonomically diverse Katian crinoid assemblage, but also for being an early ecologically complex fauna that developed in the wake of the Great Ordovician Biodiversification Event.UUID: http://zoobank.org/f86582ed-5db6-469E-befe-34b801f9a113

Late Ordovician crinoids from the Anti-Atlas region of Morocco

Abstract The crinoid fauna of the Late Ordovician (Sandbian and Katian) of Morocco is sparse, but diverse. The one previously described species, Rosfacrinus robustus Le Menn & Spjeldnaes, 1996 , is now known to be part of an assemblage of at least 10 species, including the new taxa Iocrinus ouzammoui sp. nov. (Disparida), Superlininicrinus advorsa gen. et sp. nov., Isthloucrinus praecursor gen. et a sp. nov. (Cladida) and Euptychocrinus ? atelis sp. nov. (Camerata). The fauna also includes an additional species of Iocrinus , and several camerates including Trichinocrinus sp. and a monobathrid with probable affinities to the Tanaocrinidae. Undeterminable specimens of demonstrably different taxa are described as far as possible. The fauna includes genera previously known from Laurentia and Avalonia, implying unexpected latitudinal dispersal, together with evidence for substantial endemic diversification among cladids and camerates. Several of the taxa have unusual plate arrangements, including a mosaic of primitive and derived characters; this implies that early crinoid diversification was not limited to tropical carbonate facies. The fauna remains poorly known, with low numbers of specimens, and future collecting is likely to increase the diversity significantly.

An echinoderm Lagerstätte from the Upper Ordovician (Katian), Ontario: taxonomic re-evaluation and description of new dicyclic camerate crinoids

AbstractThe Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region of Ontario contain a highly diverse echinoderm assemblage that is herein recognized as a Konservat-Lagerstätte. Although fossil crinoids have long been recognized from these formations, the fauna has not received a comprehensive taxonomic evaluation since Springer’s classic 1911 monograph. Recent extensive collection and preparation of new material from the Bobcaygeon and Verulam formations near Brechin, Ontario recovered numerous exceptionally preserved crinoid specimens with arms, stems, and attachment structures intact. The Brechin Lagerstätte is the most taxonomically diverse Katian crinoid fauna, with more than 20 crinoid genera represented in this collection.Here, all dicyclic crinoids belonging to subclass Camerata from the Brechin Lagerstätte are evaluated. The following four genera and seven species are described from the fauna, including one new genus and four new species:Reteocrinus stellaris,Reteocrinus alveolatus,Archaeocrinus sundayaen. sp.,Archaeocrinus maraensisn. sp.,Priscillacrinus elegansn. gen. n. sp.,Cleiocrinus regius, andCleiocrinus lepidotusn. sp. The exceptional preservation of this collection provides an opportunity to describe more fully the morphologic and ontogenetic details of known Ordovician crinoid taxa, to conduct a taxonomic re-evaluation of many species, to describe new taxa, and to provide a framework for subsequent studies of crinoid community paleoecology.UUID:http://zoobank.org/e3e268a7-88e5-43cd-84ea-b40df45e8281

New crinoids from the Baltic region (Estonia): fossil tip‐dating phylogenetics constrains the origin and Ordovician–Silurian diversification of the Flexibilia (Echinodermata)

AbstractThis study documents previously unknown taxonomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end‐Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high‐resolution temporal, taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end‐Ordovician mass extinction. A Bayesian ‘fossil tip‐dating’ analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via ‘budding’ cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from ‘taxocrinid’ grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post‐Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeographical regions for clade‐based phylogenetic studies and improving estimates of global biodiversity through geological time.

Upper Ordovician crinoid pavement lagerstätte from South Wales - the discovery and rescue

In 2012 a new relief road was built in Carmarthenshire, South Wales cutting through fossiliferous rocks of Upper Ordovician age and revealing new geological sections. The engineering company undertaking the construction work developed a good working relationship with palaeontologists wanting to collect from new temporary exposures. This was extremely valuable when a bed revealing large accumulations of a single species of fossil crinoids was discovered. Due to engineering deadlines the specimens had to be excavated rapidly but cooperation with company allowed access to the site until all the material was removed.

Aboral nervous system in two Ordovician crinoids: Reconstruction and comparison of Baltic Pentamerocrinus Jaekel and Grammocrinus Eichwald

Two unusual Middle Ordovician crinoid genera from the St. Petersburg Region, Pentamerocrinus Jaekel, 1918 and Grammocrinus Eichwald, 1860, are redescribed. A new species, Pentamerocrinus kosovi sp. nov., is described based on new material and the cup structure in the type species Grammocrinus lineatus, which has previously been known only from stem fragments, is reconstructed. The system of ridges and canals on the internal surface of the cup plates in both genera is described, allowing the reconstruction of the aboral nervous system. It is in general similar to extant crinoids, but the two Ordovician genera differ considerably in structural details. In Pentamerocrinus, ten nerve cords diverge interradially from the ganglionated nerve ring at the cup base and soon are fused in pairs inside the rays. In Grammocrinus, a similar nerve ring also gives rise to ten cords, but they are inside the rays and become fused in the interrays. This distinction in morphology of the nervous systems is correlated with the interradial arrangement of the axial canal angles of the stem in the first case and radial in the second. Therefore, despite general similarity in the structure and arrangement of calyceal plates, the genus Grammocrinus is assigned to the disparid crinoid family Iocrinidae, while the monotypic family Pentamerocrinidae Jaekel, 1918 is regarded as a fam. inc. sed. of inadunate crinoids.

A review of Ordovician crinoids from France: New data from the Darriwilian of the Armorican Massif and palaeobiogeographic implications

All known occurrences of crinoids in the Ordovician of France (Armorican Massif, Montagne Noire, Corbières and Pyrénées) are reviewed and replaced stratigraphically. Fully articulated crinoids are described for the first time in the Darriwilian (Middle Ordovician) of the Armorican Massif. The disparid crinoid Heviacrinus melendezi is reported from the middle and late Darriwilian (artus and teretiusculus zones) of both Brittany and Normandy, which extends both its geographic distribution and its temporal range. In addition, a new species of Heviacrinus, H. tromelini is described from the late Darriwilian (teretiusculus zone) of both Brittany and Normandy. Finally, three successive French Ordovician crinoid faunas are identified. They show strong palaeobiogeographic affinities with other Gondwanan and peri-Gondwanan assemblages, and in particular with those of the Mediterranean Province.

South America’s earliest (Ordovician, Floian) crinoids

AbstractTwo new Early Ordovician crinoids have been discovered in Gondwanan rocks of northwest Argentina.Ramseyocrinus argentinusn. sp., among the most complete for the genus, aids in reconstructing key morphology.Ramseyocrinusis unorthodox with just four radials forming the entire cup, these articulating to five arms above and a tetrameric stem below. Evidence is presented radials comprise A, B, D, and E ray elements (C absent) with B and D radials adjoining to form a compound facet for the C arm. Thus the cup entirely lacks posterior plating; an elongate anal sac projects from the CD tegmen region alongside the C arm. Cup synapomorphies closely linkRamseyocrinusand the Middle OrdovicianTetragonocrinus; inclusion of this clade within disparids is tenuous.Quechuacrinus ticsan. gen. and sp., increases the paleogeographic range of reteocrinid camerates, previously documented only from Laurentia. This taxon expresses synapomorphies characterizing the Late OrdovicianReteocrinus, demonstrating the antiquity of this morphotype.

A Middle Ordovician crinoid from the beach gravels of Ristna Cape, Hiiumaa Island, Estonia

Abstract Reworked fossils may be exotic, but more typically are locally derived. Echinoderms have only rarely been identified from beach clasts; most commonly, these are Upper Cretaceous echinoids from the Chalk. A pebble collected from a beach in Estonia has yielded a moderately well preserved specimen of the crinoid stem, Baltocrinus (col.) antiquus (Eichwald). This species is typical of the Baltic region, only being known from the Middle Ordovician (Darriwilian) of Estonia, but is exotic because the local outcrop is Upper Ordovician to Silurian.

A Laurentian Iocrinus Hall (Crinoidea, Disparida) in the Dapingian or Darriwilian (Middle Ordovician, Arenig) of Oman

Early and early Middle Ordovician crinoids are rare globally, and are best known from North America and the British Isles. The first Arenig crinoid from the Arabian Peninsula is Iocrinus sp. cf. I. subcrassus (Meek and Wor- then), known from two near-complete individuals, and numerous fragmentary specimens and ossicles. These are the stratigraphically oldest Iocrinus specimens, and provide an unexpected extension of the palaeogeographical range of a genus known otherwise from slightly younger deposits in Laurentia (North America) and Avalonia (Wales). The Oman specimens differ from Gondwanan Heviacrinus melendezi Gil Cid et al., currently classified as a maennilicrinid, but mor- phologically close to Iocrinus, in having arms that branch at least seven times instead of four and in having columnals typical of Iocrinus. Three species from Wales and the Welsh Borders, previously placed in Iocrinus, but differing in having smooth, conical dorsal cups, are reclassified as Margoiocrinus Donovan gen. nov., type species Iocrinus shelvensis Rams- bottom.

Paleoecology of suspension-feeding echinoderm assemblages from the Upper Ordovician (Katian, Shermanian) Walcott-Rust Quarry of New York

The Walcott-Rust Quarry echinoderm fauna lived at the base of a carbonate ramp in moderately deep water (Benthic Assemblage 5 of Boucot and others) below wave base for all or most storms but within the photic zone. The inhabitants of the soft substrate were buried rapidly by distal carbonate turbidity currents or mudflows. Because of the episodic sedimentation, the organisms were opportunistic. The suspension-feeding echinoderms include nine crinoids, a rhombiferan, and a paracrinoid. They occur with a variety of filter-feeding bryozoan colonies, a few brachiopods, and numerous trilobites. Most suspension-feeding echinoderms were attached by small holdfasts to hard shelly substrates. Some of these substrates lay on the seafloor, whereas others may have been elevated when the larvae settled. Other types of holdfasts are distal stems that are tightly and permanently coiled around crinoid stems, open distal stem coils that lay on the substrate or were wrapped around soft objects, and recumbent stems running along the seafloor. The echinoderms occupied levels from the seafloor to almost a meter above it, whereas the bryozoans and brachiopods ranged from the seabed to a maximum height of about 10 cm. The sizes of the echinoderm food grooves and comparisons with their modern analogues along with filtration theory indicate that they ate food particles that were mostly larger than those taken by bryozoans. In general, the different taxa of suspension-feeding echinoderms living at the same elevation above the seafloor collected food particles of different maximum sizes and different mean sizes; however, they overlapped greatly with respect to smaller food items. The various crinoid species were able to feed at different ranges of ambient current velocities, which also tended to separate them ecologically. Crinoids having narrow food grooves were restricted to feeding on small food particles but they caught food items over a wide range of current velocities; the converse is also true, which suggests an evolutionary or behavioral tradeoff. As in most Ordovician crinoid communities, predation was comparatively low. Regenerated arms in crinoids reflect predation on about 1.8% of the individuals in the fauna and the most likely fossilized culprits are trilobites and straight nautiloids. Competition for space and attachment sites within and between species of the Walcott-Rust Quarry crinoid and rhombiferan assemblages does not seem to have been significant in regulating their ecological structure. Comparison with shallow-water crinoid assemblages of roughly the same age demonstrates that the Walcott-Rust Quarry faunas were less diverse and less complex. This could be caused by one or more of the following conditions that affected the Walcott-Rust fauna: lower average current velocities, the episodic sedimentological disturbances, higher suspended sediment content in the water, and softer substrates.

The effects of rarity and abundance distributions on measurements of local morphological disparity

Understanding the relationships between morphological disparity and environment, geography, and scale require examination at the local level. Even with disparity metrics that are inherently sample size independent, the nature of rare species and the segregation of common and rare species within morphospace can create substantial sampling issues. Eight well-sampled, Late Ordovician crinoid assemblages were examined for potential biases in the study of local disparity. Disparity is based on the ordination of discrete characters. The rare and common species within these assemblages contributed equally to disparity. In spite of this pattern, rare species in some localities occupy a different area of morphospace, causing disparity to vary greatly with sampling intensity. Morphological rarefaction based on the number of specimens shows that disparity weighted by abundance is constant past a sample size of approximately 30 individuals. This metric is dependent on the evenness within an assemblage as well as the abundance within subgroups in morphospace. Disparity weighted according to abundance gives a view of the functional disparity of an assemblage, which is more applicable in studies of local disparity, though unweighted disparity is still preferred in regional-scale studies and in investigations of morphospace filling through a clade's history.

The application of filtration theory to food gathering in Ordovician crinoids

Food gathering of some adult Upper Ordovician crinoids was modeled by means of filtration theory. The arm-branching patterns of the 13 species examined range from nonpinnulate isotomous arms to uniserial and biserial arms with numerous pinnules. Most taxa are roughly equivalent with respect to ambient current velocities and the nutrient contents needed from seawater. Two species with extensively branched arms have markedly higher nutritional requirements at any one ambient current velocity. The results are somewhat correlated with environment in the form of differential current velocities, water flow patterns, and food abundance and composition. The data are generally compatible with filtration theory and the environmental distributions of many Ordovician and other Paleozoic crinoids, and they reveal that Upper Ordovician crinoids had at least partially developed the ecological patterns seen in later Paleozoic crinoids. Various morphological, physiological, and behavioral changes can be employed by crinoids to alter their nutritional balance. The size distributions of food particles that are caught by the crinoids are modeled. These food particle distributions for the Ordovician fossils resemble those of modern crinoids. Relative to the population of food items, the distributions of particles that are trapped are shifted towards larger items because the crinoid filtration nets are more efficient at catching larger particles. Crinoids with relatively open filtration nets and large food-catching tube feet are generalized and feed on a wide range of food particles of a relatively large mean size. The more specialized taxa with extensively branched arms bearing small and closely packed food-catching tube feet are restricted to a more narrow range of smaller food particles.

New and revised occurrences of Ordovician crinoids from southwestern Europe

A comprehensive treatment of Ordovician crinoids from southwestern Europe is presented, including taxa based on articulated crowns and stems. This summary incorporates new material, new localities, and a revision of some southwestern Europe occurrences. The first record of an Ordovician crinoid from Portugal,Delgadocrinus oportovinumn. gen. and sp., is reported, and this is the oldest known crinoid from the Iberian Peninsula (Arenigian/Oretanian boundary, early Darriwilian). Geographic and temporal ranges of several crinoids are revised from peri-Gondwanan areas in southwestern Europe and northern Africa or modified with new Iberian material. The Spanish range ofHeviacrinus melendeziGil Cid et al., 1996 is extended down into the lower upper Oretanian, andMerocrinus millanaeAusich et al., 2002 is restricted to the upper lower Dobrotivian. The stratigraphic position ofOrtsaecrinus cocaeGil Cid et al., 1999b is restricted to the early middle Berounian, and the range ofVisocrinus castelliAusich et al., 2002 is restricted to the late middle Berounian (see Fig. 2). New topotype material ofMorenacrinus silvaniAusich et al., 2002 is reported that furthers understanding of the occurrence this taxon, which was previously only positively known from the holotype.

OBITUARY: W. H. C. (Bill) RAMSBOTTOM (1926–2004)

Bill Ramsbottom, one of the greatest names in Carboniferous geology of the 20th century, not just in Britain but throughout the world, died at Kirby Malzeard in Nidderdale on the 31st October, 2004. Bill was born in Salford in 1926, but grew up in Yorkshire, a county that he loved. He graduated from Clare College, Cambridge, in 1947, and in the same year joined the Geological Survey in London. He completed his doctoral dissertation on Lower Palaeozoic crinoids at Chelsea Polytechnic College (University of London) in 1954. A monograph of Ordovician crinoids was duly published, but although some of the results of his work on Silurian forms also appeared in several journals, much important work on echinoderms from this period remained unpublished at the time of his death. He moved to the Leeds Geological Survey Office in 1958, and purchased a house in Collingham, near Wetherby, close to the home of W. S. Bisat, F.R.S., the pioneering worker on the Carboniferous ammonoids of northern England and their use in bio- and chronostratigraphy. This coincidental but happy juxtaposition of great minds proved of particular benefit to Bill since, because of the requirements of his official duties, the principal objects of his researches had changed from Lower Palaeozoic echinoderms to Carboniferous stratigraphy and biostratigraphy. As a …

ONTOGENY OF THE FOOD-GATHERING SYSTEM IN ORDOVICIAN CRINOIDS

The growth of the food-gathering systems of Ordovician crinoids illustrates the solutions evolved to avoid or minimize problems of suspension feeding and maintenance. The column has low metabolic requirements and may even be self-sufficient; little or no food need be diverted from the crown to the column. The tissue that the food-gathering system supplies with food is all or mostly in the crown. The volume of tissue in the crown is isometric with its volume. Distal arm branches, ramules, or pinnules form throughout growth of most taxa. The number of arm branches is constant in hybocrinids and porocrinids. The length and number of plates in the food-gathering system show marked positive allometry relative to crown volume. Food grooves become wider in larger crinoids but growth rates vary greatly. Branch density declines in all species studied. The tubefoot spacing can be constant, increase, or decrease in larger crinoids. Food-gathering capacity is the number of food-catching tubefeet multiplied by the average food-groove width, and it is positively allometric in terms of crown volume. The food-gathering ratio (food-gathering capacity: crown volume) declines somewhat, remains the same, or increases slightly during growth. The food-gathering parameters are correlated with arm structure. Crinoids with pinnulate arms exhibit the highest food-gathering ratios, high values of tubefoot spacing and branch density, and narrow food grooves, and they catch small food particles with small and closely spaced tubefeet. The lowest food-gathering ratios are seen in crinoids with unbranched and nonpinnulate arms which possess low tubefoot spacings and branch densities and wide food grooves. On average these organisms ate larger food items collected by larger and more widely spaced tubefeet. Larger food-gathering ratios are associated with greater resistance to fluid flow through the arms and tubefeet. The allometry of the food-gathering systems of Ordovician crinoids suggests that their metabolic rates could be proportional to body mass0.75 as in many living animals and plants.

Paleoecologic Associations and Secondary Tiering of Cornulites on Crinoids and Bivalves in the Upper Ordovician (Cincinnatian) of Southwestern Ohio, Southeastern Indiana, and Northern Kentucky

Other| December 01, 2003 Paleoecologic Associations and Secondary Tiering of Cornulites on Crinoids and Bivalves in the Upper Ordovician (Cincinnatian) of Southwestern Ohio, Southeastern Indiana, and Northern Kentucky ROBERT W. MORRIS; ROBERT W. MORRIS 1Department of Geology, Wittenberg University, Springfield, OH 45501, rmorris@wittenberg.edu Search for other works by this author on: GSW Google Scholar STEPHEN H. FELTON STEPHEN H. FELTON 25678 Biscayne Avenue, Cincinnati, OH 45248 Search for other works by this author on: GSW Google Scholar Author and Article Information ROBERT W. MORRIS 1Department of Geology, Wittenberg University, Springfield, OH 45501, rmorris@wittenberg.edu STEPHEN H. FELTON 25678 Biscayne Avenue, Cincinnati, OH 45248 Publisher: SEPM Society for Sedimentary Geology Accepted: 28 Jul 2003 First Online: 03 Mar 2017 Online ISSN: 1938-5323 Print ISSN: 0883-1351 Society for Sedimentary Geology PALAIOS (2003) 18 (6): 546–558. https://doi.org/10.1669/0883-1351(2003)018<0546:PAASTO>2.0.CO;2 Article history Accepted: 28 Jul 2003 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation ROBERT W. MORRIS, STEPHEN H. FELTON; Paleoecologic Associations and Secondary Tiering of Cornulites on Crinoids and Bivalves in the Upper Ordovician (Cincinnatian) of Southwestern Ohio, Southeastern Indiana, and Northern Kentucky. PALAIOS 2003;; 18 (6): 546–558. doi: https://doi.org/10.1669/0883-1351(2003)018<0546:PAASTO>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract The stems of once-living Ordovician crinoids, especially the genera Ectenocrinus, Iocrinus, and Cincinnaticrinus, provided suitable attachment sites for the growth and development of both individuals and clusters of Cornulites—a tubiculous, suspension-feeding, worm-like organism. This association of cornulitids as opportunistic secondary tierers on crinoids was common from the Late Edenian into the Maysvillian in the Kope and Fairview portions of the Cincinnatian Series in the Cincinnati Arch area and less common in the Richmondian. Cornulitids utilizing this elevated location avoided some of the turbidity problems associated with an unstable, muddy substrate, and benefited from their ability to feed at a higher tier level. Several specimens of the byssate clam Ambonychia document the presence of Cornulites as secondary, low-level tierers on these bivalves, mainly during the Richmondian. Cornulitids positioned themselves on these ambonychiids to take advantage of feeding currents generated by the host. Cornulitids were also epizoans on the epifaunal clam Caritodens. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

ORDOVICIAN [DOBROTIVIAN (LLANDEILLIAN STAGE) TO ASHGILL] CRINOIDS (PHYLUM ECHINODERMATA) FROM THE MONTES DE TOLEDO AND SIERRA MORENA, SPAIN WITH IMPLICATIONS FOR PALEOGEOGRAPHY OF PERI-GONDWANA

Seven crinoid species and one very unusual column are recognized from the Ordovician, Dobrotivian (Llandeillian Stage) to Ashgill of Spain. Three previously described species, Heviacrinus melendezi Gil Cid, Domínguez, and Silván, 1996; Coralcrinus sarachagorum Gil Cid, Domínguez, and Silván, 1998; and Ortsaecrinus cocae Gil Cid, Domínguez, Torres, and Jiménez, 1999, are considered, and four new species assigned to three new genera are described herein, including Visocrinus castelli, Fresnedacrinus ibericus, Morenacrinus silvani, and Merocrinus millanae. Previous reports of Ramseyocrinus from Spain have been revised, and we agree that this disparid is not presently known from Spain. These crinoids represent the largest Ordovician crinoid fauna from Gondwana, including these localities and those from the Montagne Noire along peri-Gondwana during the Ordovician. The crinoids reported here, from the Montes de Toledo and Sierra Morena, and the Ordovician crinoids from Montagne Noire have very little in common with Ordovician crinoids from the Prague Basin. Thus, these new data support paleogeographic plate positioning that allows for either paleoclimatic, paleoenvironmental, or paleogeographic isolation between the Prague Basin and peri-Gondwana.

Ordovician [Dobrotivian (Llandeillian Stage) to Ashgill] crinoids (phylum Echinodermata) from the Montes de Toledo and Sierra Morena, Spain with implications for paleogeography of Peri-Gondwana

Seven crinoid species and one very unusual column are recognized from the Ordovician, Dobrotivian (Llandeillian Stage) to Ashgill of Spain. Three previously described species, Heviacrinus melendezi Gil Cid, Domínguez, and Silván, 1996; Coralcrinus sarachagorum Gil Cid, Domínguez, and Silván, 1998; and Ortsaecrinus cocae Gil Cid, Domínguez, Torres, and Jiménez, 1999, are considered, and four new species assigned to three new genera are described herein, including Visocrinus castelli, Fresnedacrinus ibericus, Morenacrinus silvani, and Merocrinus millanae. Previous reports of Ramseyocrinus from Spain have been revised, and we agree that this disparid is not presently known from Spain. These crinoids represent the largest Ordovician crinoid fauna from Gondwana, including these localities and those from the Montagne Noire along peri-Gondwana during the Ordovician. The crinoids reported here, from the Montes de Toledo and Sierra Morena, and the Ordovician crinoids from Montagne Noire have very little in common with Ordovician crinoids from the Prague Basin. Thus, these new data support paleogeographic plate positioning that allows for either paleoclimatic, paleoenvironmental, or paleogeographic isolation between the Prague Basin and peri-Gondwana.

Survival of crinoid stems following decapitation: evidence from the Ordovician and palaeobiological implications

It was recently discovered that the stems of extant crinoids may survive after detachment of the crown, presumably feeding by the absorption of nutrients through the ectoderm. Previously, only one analogous, albeit morphologically dissimilar, pattern of crownless survival has been recognized from the fossil record. Certain Upper Ordovician (Cincinnatian) crinoid pluricolumnals from Kentucky, Ohio and Indiana, derived from the disparids Cincinnaticrinus spp., have rounded terminations reminiscent of some modern bourgueticrinid overgrowths. Such specimens have hitherto been interpreted as distal terminations of mature individuals that have become detached from their attachment structures and taken to an eleutherozoic existence. However, it is considered more probable that they represent overgrowths of the column following predatory decapitation. If this new interpretation is correct, then post-decapitation survival of crinoid stems is now recognized for most of the history of the crinoids, ‘lethal’ predation on crinoid crowns occurred at least as early as the Late Ordovician and ancient crinoid populations can no longer be determined merely by counting crowns.