Revision of the disparid Stylocrinus (Crinoidea) from the Devonian of Europe,Asia and Australia

Abstract: The discovery of new specimens and the restudy of known collections result in revision of the diagnosis and the stratigraphic distribution of the disparid crinoid genus Stylocrinus, from the Middle and Upper Devonian of Europe, Asia and Australia. The consistent development of three basal plates, the atomous arms with internally inclined edges adjoining laterally with adjacent brachials in an interlocking network and an apparently rudimentary pinnulation is recognised. The high ecophenotypic plasticity of the common species S. tabulatus negates the validity of several former subspecies and demonstrates the general morphologic variability of the aboral cup proportions. This contrasts with the low morphological spectrum of rarer stylocrinid species. With exclusion of ‘S. elimatus’ (Silurian) from Stylocrinus, the genus is limited to the Devonian. A neotype is proposed for the lost holotype of S. tabulatus. Stylocrinus prescheri sp. nov. is described from the Eifelian to Givetian of Europe and Asia. The first evidence of the gastropod grazing trace fossil Radulichnus on a crinoid aboral cup (S. tabulatus), the post‐mortem incurred ossicular‐boring of radial and basal plates as well as the post‐mortem encrusting by a rugose coral are further observations on Stylocrinus aboral cups.     

Chinese origin and radiation of the Palaeozoic crinoid family Petalocrinidae

The Ordovician to Devonian family Petalocrinidae includes 28 species belonging to 5 genera. This family is unique because the arm plates are fused into a large fan or cylinder. Paleobiogeographic occurrences of this family include Laurentia, Baltica, Avalonia, South China, Sibumasu, and Perunica blocks. The family has the oldest petalocrinids from China. An early radiation of this clade resulted in three genera during the Llandovery of China. Petalocrinus became cosmopolitan during the Llandovery and Wenlock, and the youngest genus is present in the Lower Devonian of the Czech Republic. Taxonomic determination for the Petalocrinidae is based on the fused arm plates instead of cup plates. The diverse morphology of these arm plates suggests a variety of aerosol suspension-feeding modes may have been used by petalocrinids.     

Lower Middle Devonian,Eifelian, crinoids from central Guangxi,South China

The extensive Devonian marine deposits of South China have yielded few articulated crinoid cups or theca. Two Eifelian specimens, from the Gupa Member, are the first ones reported from the Yingtang Formation, Eifelian, from the Ma’anshan section, Guangxi, South China. The new taxon Guangxicrinus xiangzhouensis n. gen. n. sp. is the first report of a marsupiocrinid in China, extending the paleogeographic range of the family into the Paleotethys and the stratigraphic range of the family upward from the upper Silurian into the lower Middle Devonian, Eifelian. The occurrence of Halocrinites sp. is the third occurrence of a cupressocrinitid in China and extends the paleogeographic range from Yunnan to Guangxi.     

Aboral nervous system in two Ordovician crinoids: Reconstruction and comparison of Baltic <Emphasis Type="Italic">Pentamerocrinus</Emphasis> Jaekel and <Emphasis Type="Italic">Grammocrinus</Emphasis> 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.     

Testing reduced evolutionary rates during the Late Palaeozoic Ice Age using the crinoid fossil record

In 2003, Stanley & Powell reported depressed rates of origination and extinction in marine invertebrates during the Late Palaeozoic Ice Age (LPIA). Using a database of crinoid genera, rates of origination, extinction and genus duration were calculated at the stage level from the Early Devonian to the Late Permian. This 165 m.y. time span includes non‐glacial intervals before and after the LPIA, which spanned the Serpukhovian to Sakmarian, providing background rates for comparison. Data generated on crinoid evolutionary rates during the Middle to Late Palaeozoic were analysed and compared to Stanley & Powell's data to determine whether crinoid evolutionary patterns support their findings or suggest an alternative hypothesis. Rates of origination and extinction in all crinoid clades were reduced during the LPIA compared to the combined background intervals before and after the LPIA. However, crinoid diversity was higher during the LPIA than the surrounding time intervals. The difference in diversity trends between crinoids and other marine invertebrates is due to the advanced cladids clade. Unstable, fluctuating environmental conditions during the LPIA may have created habitats suitable for opportunistic crinoid genera that reduced both the probability of origination and extinction. The increased diversity of the advanced cladids is likely due to their unique adaptation of muscular arm articulations, which allowed them to thrive in marine settings with increased siliciclastic influx brought on by the Alleghenian orogeny. Despite the advanced cladids’ departure from the expected diversity count, the results of analyses performed on the updated crinoid database provide independent confirmation of Stanley & Powell's original hypothesis of depressed evolutionary rates in marine invertebrates during the LPIA.     

Revision of Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia

Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia was originally described as the earliest crinoid(?) known from the fossil record. Recently, Conway Morris and Ausich & Babcock have questioned whether Echmatocrinus is in fact an echinoderm, comparing it instead to cnidarians with a polyp-like body and pinnate tentacles, and other authors are beginning to use this reinterpretation. We studied the well-preserved holotype of Echmatocrinus brachiatus, two paratypes, and 18 new specimens recovered from different levels in the Burgess Shale sequence at three localities. All are preserved as pyrite films in dark shale with relatively little relief, suggesting a lightly skeletized body. Complete specimens have a long, slightly tapering, large-plated attachment stalk, a conical cup or calyx with numerous small to medium-sized irregular plates, and 7–10 short arms with heavier plating and (in the holotype) soft appendages alternating from opposite sides of several arms. Several morphologic features indicate that Echmatocrinus is an echinoderm and has crinoid affinities: (1) Sutured plates, shown by darker depressed sutures, slightly raised plate centers, and oriented plate ornament, cover all major parts of the body; (2) reticulate surface ornament in the pyrite film on the plates of all specimens matches the ornament in the Burgess Shale edrioasteroid Walcottidiscus, an undoubted echinoderm, but not the pyritized surfaces of other metazoans in the fauna; (3) this distinctive ornament may represent the surface expression of microporous stereom; (4) possible ligament or muscle pads are present between the arm ossicles to fold and unfurl the more heavily plated arms. Within the echinoderms, only crinoids commonly have a calyx attached by a stalk or stem to the substrate and bear erect, moveable, uniserial arms for feeding. Although Echmatocrinus shows some resemblance to octocorals in overall body shape as an attached suspension feeder, almost all the details are different, indicating that Echmatocrinus is most likely unrelated to this group. All complete specimens of Echmatocrinus are attached to hard substrates, either another fossil or skeletal debris. The new specimens indicate that Echmatocrinus was twice as common (about 0.02%) in the Burgess Shale fauna as previously recorded and represents one of the earliest attached, medium-level, skeletized, suspension feeders or microcarnivores in the fossil record.     

Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco

Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa.     

Mode of life of fan-hand-like Scoliocrinus according to functional form and syntopy with two other irregular crinoids from the Middle Devonian of the Rhenish Massif (Germany)

For a long time, the highly aberrant crinoid Scoliocrinus was known only from the Lower Givetian Eifel area (western Rhenish Massif) as a single oblique calyx with only two out of five radials having an arm facet. Several almost complete crowns of a new species in the Middle Givetian Finnentrop area (eastern Rhenish Massif) have two fan-like arms (in the A and E rays), and a horizontal large anal tube. The probable mode of life of Scoliocrinus is analysed by (a) functional morphology mainly of the arms, (b) criteria of minimised faecal recycling, (c) biostratinomic association with two new species of another aberrant, but four-armed new crinoid genus thus suggesting original syntopy with Scoliocrinus. It is concluded that the construction of Scoliocrinus is probably an adaptation to prevailing unidirectional (tidal?) currents in biostromal reef biotopes. This is supported by rather similar crinoid occurrences in a Lower Givetian biostromal reef-related region in the western Rhenish Massif, with the genotype of Scoliocrinus and a newly assigned third species of Scoliocrinus (arm and probable part of the calyx), as well as four-armed species. The new forms are described as Scoliocrinus ubaghsi nov. sp., Scoliocrinus gerolsteinensis nov. sp., Trapezocrinus scheeri nov. gen., nov. sp., and Trapezocrinus hilperti nov. gen., nov. sp.     

Host‐specific acrothoracid barnacles on Middle Devonian platyceratid gastropods

Borings, attributed to acrothoracic barnacles, occur on the platyceratid gastropod Naticonema lineatum (Conrad) from the Middle Devonian Hamilton Group of western New York and rarely in specimens as old as the Early Devonian. These latter are the oldest known acrothoracid borings are in the fossil record. The borings are consistently developed as laterally compressed, inequilateral pouches exclusively on these gastropods, commonly as dense infestations.

Naticonema shells yielding borings typically occur associated with partially articulated qrinoid remains, and they are sometimes found attached to crinoids in a manner similar to coprophagous Platyceras. In addition to barnacle borings, Naticonema shells often bear thin encrustations of bryozoans which are usually perforated by these borings but sometimes also overgrow them. Barnacles bored live hosts; gastropods prevented shell penetration by producing cyst‐like secondary secretions of calcite beneath acrothoracid boreholes.

The relative antiquity of these borings and their association with coprophagous platyceratids makes their discovery particularly significant in revealing aspects of the early ecology of barnacles. Attachment to the host commensal gastropods was one of the first successful life modes of these crustaceans prior to their later diversification to other habitats. Mississippian and Pennsylvanian occurrences of similarly bored gastropods demonstrate continuity of the barnacle‐gastropod‐crinoid ecological association from the Middle to Late Paleozoic.     

Redescription of the cyathocrinid cladid <Emphasis Type="Italic">Codiacrinus schultzei</Emphasis> Follmann, 1887 from the Lower Devonian Hunsrück Slate at Bundenbach (Germany)

Codiacrinus schultzei Follmann, 1887 commonly occurs in the Lower Devonian Hunsrück Slate of Bundenbach (Germany). Although this cyathocrinid cladid has been studied for almost 125 years, its morphology remains incompletely known. This article reports unusual arm growth, the regeneration of an arm, the preservation of tegminal plates, the sculpture of the cup (hexagonal concentric lines), and the preservation of visceral organs, which were positioned within the cup. One X-radiograph possibly shows the mid- and hind-gut (preserved as soft tissues). Furthermore, the shape and arrangement of the cover plates are described in more detail than previously. Codiacrinus schultzei is systematically redescribed and compared with the other species in the genus. Further study of the systematic placement (within the Flexibilia?) is appropriate.     

Revision of Strunian crinoids and blastoids from Germany

In 1930W.E. Schmidt described all known crinoids from the German Early Carboniferous, including the Etroeungt beds of Germany, which are now judged to be latest Devonian (Famennian) in age. On a global basis, Famennian camerate crinoids generally show a closer relationship to succeeding Early Carboniferous faunas than they do to older Frasnian or Middle Devonian crinoids, which also is the case for the Strunian fauna. Holdovers from older Devonian faunas include, among others,Adelocrinus, a descendant of olderArthroacantha, in England and Germany, andPetaloblastus, which is one of the youngest genera of the blastoid family Hyperoblastidae. Precursors of younger Early Carboniferous groups include platycrinoids, primitive actinocrinoids, dichocrinoids, and the blastoid genusDoryblastus, which is one of the oldest members of the family Orbitremitidae. All of these groups, which became important parts of the Early Carboniferous crinoid and blastoid radiation, give Famennian crinoid faunas much more of an Early Carboniferous than a Devonian aspect. Rhipidocrinus schmidti n. sp. is erected for specimens that originally were reported from the Etroeungt asRhodocrinus uniarticulatus. We judge that there are currently four valid species assigned toRhipidocrinus: R. crenatus, R. perloricatus, R. praecursor, and our new species,R. schmidti. Hydriocrinus ratingensis Schmidt is reassigned to ?Sostronocrinus. We note thatSchmidt (1906), notJaekel (1906) as has been reported previously, is the author ofRhipidocrinus perloricatus. Owing to the poor preservation of the Etroeungt material, we regard the namePlatycrinites wunstorfi Schmidt 1930 to be a nomen nudum.     

A Lower Devonian hexacrinitid crinoid (Camerata,Monobathrida) from south-west England

The most species-rich and widespread crinoid clade in the type area of the Devonian of south-west England is the monobathrid camerate family Hexacrinitidae Wachsmuth and Springer. These crinoids occur either as thecae (Middle Devonian) or pluricolumnals and columnals (Lower to Upper Devonian). The first new, nominal species of hexacrinitid, probably Oehlerticrinus Le Menn, to be described from this region since the nineteenth century is Oehlerticrinus peachi sp. nov. from the Lower Devonian Looe Basin of southern Cornwall. This specimen is mouldic and somewhat flattened, retaining the proxistele and arms. Diagnostic features include the heteromorphic proxistele with circlets of long, unbranched radices directed towards the crown; the high, box-like (=skyphosiform) theca with a flattened base; a thecal plate sculpture of tubercles and ridges arranged in triangles; and the pinnulate arms. Any uncertainty in identifying this species at the generic level rests with the arms being pinnulate, not ramulose as is common in Hexacrinites Austin and Austin, indicating that O. peachi is closer to Oehlerticrinus Le Menn.     

Unusual tabulate‐crinoid biocoenosis from the Lower Devonian of Morocco

The Early Devonian (Pragian: sulcatus to pireneae conodont zones) crinoid–coral biocoenosis from Hamar Laghdad, Morocco contains fragments of crinoid stalks of various taxa encrusted by spherical and ellipsoidal coralla of the tabulate coral Hamarilopora minima. These corals were encrusting host crinoids syn vivo, and this is evidenced by pluricolumnals exceeding 30 elements overgrown from all sides. Most known to date crinoid–epibiont associations display various types of reaction to the epibiont, such as swellings and deformations. In the case discussed here, no clear interaction is visible; therefore, this association can be classified as paroecia. It can be inferred, however, that due to a change in mechanical properties of the crinoid stalk (losing flexibility), the epizoan influence on the host was negative, while the coral was profiting from the elevated position over the seafloor and nutrient‐bearing water currents. It can be supposed that this interaction was close to parasitism. No strict species‐specific relationship between the epizoan and the host was observed.     

Disarticulation patterns in Ordovician crinoids: Implications for the evolutionary history of connective tissue in the Crinoidea

Taphonomic information is examined to evaluate the early history of connective tissues in the Crinoidea. The pattern of stalk segmentation of Middle and Late Ordovician crinoids is consistent with the two-ligament (intercolumnal and through-going ligaments) pattern present in living isocrinid crinoids and interpreted for fossil isocrinids, holocrinids, and Lower Mississippian crinoids. A single rhombiferan was also examined; its taphonomic pattern is also indicative of this style of tissue organization. Furthermore, the taphonomy of all Middle and Late Ordovician crinoids may reflect that they lacked discretely organized muscles between arm brachials, which is consistent with the hypothesis that muscles evolved as a connective tissue between plates only once within the Crinoidea, during the Early Devonian. These data indicate that the two-ligament organization of the stalk is a primitive feature among the Crinoidea and perhaps even among stalked echinoderms. Therefore, the autotomy function of this column-tissue organization among living crinoids is an exaptation. On the other hand, discretely organized muscles as connective tissue in crinoid arms is a derived trait that first appeared during the middle Paleozoic; this adaptation proved very successful for the advanced cladid crinoids.     

Revision Of Late Devonian (Famennian) And Some Early Carboniferous (Tournaisian) Crinoids And Blastoids From The Type Devonian Area Of North Devon

The crinoids and blastoids from the Pilton (Beds) Formation of the type Devonian of north Devonshire are revised. These fossils were monographed by the Rev. G. F. Whidborne in 1898, but have not been studied since that time. Recent studies on various groups of fossils from the Pilton and related rocks in North Devon confirm that the great majority of these fossils are Famennian, although three specimens from Fremington are probably Early Carboniferous (Tournaisian). We identify four blastoid taxa from a fauna that is sparse and poorly preserved; two spiraculates, one fissiculate, and one taxon unidentifiable at the ordinal level. Mesoblastus cf. M. crenulatus from the Gattendorfia Zone (Lower Carboniferous) near Fremington is the oldest known representative of this genus. The crinoid fauna is somewhat more diverse, but the preservation is equally poor. No changes are made in the flexible crinoids. Among camerate crinoids, one species is reassigned to Eumorphocrinus and one is retained in Actinocrinites. Specimens of some crinoids, such as Rhodocrinites and Megistocrinus, are so poorly preserved that certain identification was not possible. The hexacrinoid Adelocrinus, relegated to uncertainty for 150 years, is here shown to be a valid genus that is very similar to Arthroacantha, but not synonymous with it. Among the cladid crinoids, the dominant groups are those within the Superfamily Scytalocrinacea, which includes Bridgerocrinus, Sostronocrinus, and Scytalocrinus, all of which are placed in the new family Sostronocrinidae. One new species, Glossocrinus whidbornei, is named. Non‐pinnulate cladids, common in older Devonian rocks, do not occur. The fauna shows considerable similarity with faunas from eastern North America and Germany. It shows less resemblance to the extensive Famennian crinoid and blastoid fauna of north‐western China, despite some remarkable congruencies, especially the occurrence of very similar species of Actinocrinites in these widely separated areas.     

Tube foot preservation in the Devonian crinoid Codiacrinus from the Lower Devonian Hunsrück Slate,Germany

Fossilized tube feet are described on Codiacrinus schultzei Follmann from the Lower Devonian Hunsrück Slate of Germany. This is the first definitive proof of tube feet on any fossil crinoid. Three lightly pyritized, flattened tube feet are preserved in a single interray of this cladid crinoid. The tube feet were at least 7 mm long. Their preservation is very similar to the tube feet reported previously from a Hunsrück ophiuroid, except that the Codiacrinus tube feet have small papillae, similar to living crinoids.     

The Middle Devonian lycopsid Haskinsia Grierson et Banks from the Ruppert Coast, Marie Byrd Land, West Antarctica

New observations on leaves of herbaceous lycopsid specimens previously attributed to Drepanophycus schopfii Mildenhall from Marie Byrd Land, West Antarctica, indicate that they belong to Haskinsia colophylla Grierson et Banks. Haskinsia was a wide spread lycopsid during the Middle Devonian.     

Revision of Hyolitha from the Ordovician of Estonia

Topotype specimens of the Middle OrdovicianHyolithes acutus Eichwald, 1840, which is the type of the genus that lent its name to a family, order, class, and even phylum according to some, andH. latus Eichwald, 1860 allow that genus and those species to be firmly established on a sound, morphologic basis. In addition, preservation of the types ofHyolithes striatus Eichwald, 1860 is sufficiently good to warrant reassignment toDorsolinevitus Syssoiev, 1958. In contrast, the type ofH. insularis Eichwald, 1860 is incompletely preserved, and this species is not recognizable beyond the type material. The concept of the family Hyolithidae is revised to more closely conform to the morphology ofHyolithes, with authorship herein ascribed toSyssoiev (1958) rather than toNicholson (1872). The stratigraphic distribution of these taxa suggests thatHyolithes as defined herein first appears in the Middle Ordovician, but extends into at least the Lower Devonian, as suggested by two species from the Barrandian region of the Czech Republic. Their geographic distribution further re-enforces the notion of two distinct paleobiogeographic provinces based on hyoliths, a Mediterranean province and Baltic province, with almost no mixing of hyolith faunas during the Ordovician.      

The subterranean genus Niphargus (Crustacea, Amphipoda) in the Middle East: A faunistic overview with descriptions of two new species

The Middle East is at the southeastern borderline of the range of the subterranean amphipod Niphargus. The review of new and published data identified two new species and set the guidelines for the future research in the area. The genus in this part of the world seems to be insufficiently studied. The taxonomic status of Niphargus valachicus, population identified as N. spoeckeri and some populations, identified as N. nadarini, need to be reviewed. According to present data, we expect the highest diversity in Western Turkey. The eventual new records of the genus in the Middle East can be expected from those areas where even the longest periods of drought in the recent geological history did not affect the water supply.