Ordovician echinoderms

A diverse crinoid fauna is described from the Upper Ordovician (Katian) Fombuena Formation from the eastern Iberian Chains of Spain. New crinoids include the diplobathrid cameratesFombuenacrinus nodulusn. gen. n. sp.,Goyacrinus gutierrezin. gen. n. sp.,Dalicrinus hammannin. gen. n. sp., andAmbonacrinus decorusn. gen. n. sp.; the monobathrid camerateEopatelliocrinus hispaniensisn. sp.; and the cladidPicassocrinus villasin. gen. n. sp. A new occurrence ofHeviacrinus melendeziGil Cid, Domínguez Alonso, and Silván Pobes, 1996 is also documented from the Castillejo Formation (Darriwilian, Middle Ordovician) from the eastern Iberian Chains of Spain. The Fombuena Formation comprises a Gondwanan crinoid assemblage from a high paleolatitude and has the highest crinoid diversity of any currently known Katian Gondwanan fauna. This assemblage is compared to other Katian age faunas around the globe, and its paleobiogeographic implications are discussed.

The material of the discussed rare ophiuroid Bohemura jahni Jaekel, 1903 was originally collected by J. Barrande at the well-known Middle Ordovician locality Zahorany near Beroun, Barrandian area (Berounian stage, Zahofany Formation, corresponding approx. to Upper Caradocian). In Barrande' s collections these brittle-stars were designated as "Asterias Bohemica ", but this manuscript name was only mentioned in BIGSBY (1868, p.197). J. Barrande published no paper on the Bohemian asterozoans. The first description and illustration was given by O. JAEKEL (1903, short notes p. 109, 110, 112, text-fig. 6, p. 111). His description was only brief, but the text-figure showing oral side of one arm , MAPs, and outline of the disk of the ophiuroid was good, only slightly inco rrect in shape of the "boot-shaped" ambulacral ridges, in number of ambulacrals in the disk, in length • of groove spines, and in shape of the disk margin. In this Jaekel's work the brittle-star was named Bohemura jahni. The above mentioned figure was reproduced by SCHUCHERT, (1915, p. 224, fig. 21) but Schuchert did not study the original material. This was lent to W. K. Spencer who made from the specimens gutta-percha impressions (at least from the specimen NM L 10066 which is the lectotype now) and presented some remarks, short diagnosis, and an illustration (SPENCER, 1934, p. 479, p. 473, fig. 305), however, no photographs. Unfortunately, th e Spencer 's drawing is incredibly incorrect and invented, and is reproduced in SPENCER and WRIGHT (1966, in Treatise.. . , p. U86, fig. 75 2a) .

Two 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 t...

A new crinoid association reported from the Kope Formation (Katian, Ordovician) of northern Kentucky and southwestern Ohio changes the model for facies distribution of crinoids along an Ordovician onshore-offshore depth gradient.Glyptocrinus nodosusn. sp.,Plicodendrocrinus casei(Meek, 1871),Cincinnaticrinus varibrachialis(Warn and Strimple, 1977), andEctenocrinus simplex(Hall, 1847) are reported from a suspension-feeding assemblage with 26 taxa. This assemblage developed above an argillaceous packstone with most of the fossils preserved in shale. The fauna was comprised principally of secondary epifaunally tiered suspension feeders, deposit feeders, and predators. This is the first reported occurrence ofGlyptocrinusHall, 1847 andPlicodendrocrinusBrower, 1995 from the Kope Formation (lower Cincinnatian), andGlyptocrinusis represented by a new species,G.nodosus. Also, this is the first report of pinnulate camerate crinoids from the deep-water facies of the Kope Formation. Thus, deep-w...

A stepwise approach is employed to determine the phylogeny of the initial crinoid radiation during the Arenig and Llanvirn series of the Ordovician. Parsimony-based character analysis is completed first on Arenig crinoids and then for Arenig and Llanvirn crinoids combined.The topology from well-resolved trees of this early crinoid radiation indicates that the Crinoidea should be subdivided into six subclasses. A new subclass and new order, Aethocrinea and Aethocrinida, respectively, are proposed for crinoids with four circlets of plates in the aboral cup: lintels, infrabasals, basals, and radials. This aboral cup construction is best displayed byAethocrinus, one of the oldest known crinoids (?Tremadoc-Arenig). However, this primitive aboral cup construction is also present in two Llanvirn crinoids,PerittocrinusandTetracionocrinus.The Aethocrinea was a small, short-lived radiation of crinoids with this design that was different from those of other crinoids. Two families in the Aethoc...

Two echinoderm assemblages are described in the Middle Ordovician of Iran (Darriwilian). The Simeh Kuh section (Damghan area, eastern Alborz range) has yielded a rich and diverse blastozoan fauna consisting of fistuliporite (Echinosphaerites, Heliocrinites) and dichoporite rhombiferans (cheirocrinids indet., hemicosmitids indet.), as well as aristocystitid (Sinocystis) and sphaeronitid diploporites (Glyptosphaerites, Tholocystis). Heliocrinites, cheirocrinids, hemicosmitids, Glyptosphaerites, and Tholocystis are reported for the first time in the Ordovician of Iran. A less diverse assemblage was collected in the Shirgesht section (Tabas area, Derenjal Mountains), and represents the first report of Ordovician echinoderms in east-central Iran. The Shirgesht fauna includes fistuliporite rhombiferans (Heliocrinites), aristocystitid and sphaeronitid diploporites. The new Iranian material documents some of the earliest known assemblages of diploporites and rhombiferans, and thus, brings i...

The Pole Khavand area southeast of the town of Anarak preserves important clues for understanding geological evolution of Central Iran during the Palaeozoic. New observations confirm the non-conformable relationship between Doshakh metamorphites and overlying unmetamorphosed Lower Palaeozoic sediments, suggesting accretion of the volcanic arc in front of the Yazd block sometime in the late Cambrian to early Ordovician. The newly introduced volcano-sedimentary Polekhavand Formation preserves evidence of a ?Late Cambrian to Early Ordovician post-collisional bimodal volcanism and related extensional regime in the Pole Khavand area during that time. The Middle to Upper Ordovician interval of the studied succession is assigned to the newly introduced Chahgonbad Formation. The Darriwilian age of the base of this lithostratigraphical unit is demonstrated by the brachiopods Tritoechia and Yangtzeella which co-occur with a diverse a cephalopod assemblage. The low diversity fauna including br...

Moroccodiscus smithi represents a new cyclocystoid genus and species based on moldic specimens from the Middle Ordovician Taddrist Formation (Darriwilian) of SE Morocco. This represents the earliest articulated member of the Cyclocystoidea and is the first complete cyclocystoid described from the Ordovician of Gondwana, as well as the first cyclocystoid ever recorded from Africa. The anatomy and morphology of this new species were studied using a combination of conventional paleontological methods and nondestructive X-ray computed tomography. Because Moroccodiscus differs from other cyclocystoids, in particular by lacking cupules attached to the marginal ossicles, it is assigned to the new family Moroccodiscidae. This new taxon illustrates the relatively poorly known early diversification of these enigmatic extinct echinoderms and sheds light on the mode of life of cyclocystoids, including injuries to plate circlets during early ontogeny and folding of these disk-like specimens at t...

The construction of supertrees from smaller, character−based cladograms permits simultaneous inclusion of a large num− ber of taxa in a single analysis, summarizes patterns of relationships from many independent data sources, and highlights areas of conflict to be targeted by ...

Exceptionally preserved fossils yield crucial information about the evolution of Life on Earth. The Fezouata Biota from the Lower Ordovician of Morocco is a Konservat-Lagerstätte of major importance, and it is today considered as an 'Ordovician Burgess Shale.' This biota was discovered only some 15 years ago, but geological studies of the area date back to the beginning of the 20th century. Pioneering geological investigations lead to the discovery of Ordovician strata in the Anti-Atlas (1929) and ultimately resulted in their formal subdivision into four main strat-igraphic units (1942). In the Agdz area, the presence of fossiliferous Tremadocian (Lower Ordovician) strata was suspected as early as 1939, but only definitively confirmed in 1955. In the 1960s–1990s, Jacques Destombes provided the first detailed biostratigraphic framework for the Lower Ordovician of the Anti-Atlas, and collected thousands of fossils that were subsequently described in a series of monographs. In the early 2000s, exceptionally preserved fossils were discovered in the Fezouata Shale (Tremadocian–late Floian) in the central Anti-Atlas by Mohamed 'Ou Saïd' Ben Moula. This biota, now known as the Fezouata Biota, is of utmost importance, for it demonstrates the extent in the fossil record of non-biomineralising animals typical of the 'Cambrian Explosion' into the Ordovician, during the 'Great Ordovician Biodiversification.' Although most components are still in need of formal descriptions, a fairly good picture of the composition and organisation of this biota, and how it contributes to our understanding of the early evolution of metazoan communities, can now be depicted. Moreover, recent studies have substantially clarified the biostratigraphical and palaeoenvironmental context of the Fezouata Shale, and are now being followed up by detailed investigations of the taphonomy, geochemistry and micropalaeontology of this unique Konservat-Lagerstätte. These efforts will soon greatly benefit from the recovery of fresh, unweathered samples from drill cores.