Brachiopod community paleoecology, paleobiogeography, and depositional topography of the Devonian Onondaga Limestone and correlative strata in eastern North America

The Emsian? through early Eifelian Onondaga Limestone of the Appalachian Basin was deposited in a topographic basin and on the carbonate platform which surrounded the basin on the west, north, and northeast. Onondaga strata thin from the platform into the basin. Two sedimentary cycles are present in the sub-Tioga Onondaga of eastern North America. The Edgecliff-Amherstburg represents an interval of transgression, in which epeiric seas spread over much of eastern North America. During the Nedrow-Lucas regression, the interior of the carbonate platform became restricted, resulting in the deposition of evaporites. The Moorehouse-Anderdon transgression continued through the deposition of the Tioga Bentonite, followed by the pre-Speeds-Dundee regression from the craton. Early Eifelian Appalachian Basin Onondaga brachiopod communities, arranged from nearshore to offshore, include the Atrypid-Megakozlowskiella, Atrypid-Levenea, Chonetid, Atlanticocoelia, Ambocoeliid, and Truncalosia Communities. The Onondaga-age Eastern Americas Realm is divided into the Appohimchi Province in the Appalachian Basin and the Michigan Basin-Hudson Bay Lowland Province in the Midwest. The provincial assignment of the James Bay region of Ontario is uncertain; the Eastern Townships of Quebec are near the boundaries both of the two provinces of the Eastern Americas Realm, and of the Eastern Americas Realm and the Old World Realm, the latter realm being probably in the Canadian Maritime Provinces.     

Cyrtinoides Yudina and Rzhonsnitskaya, 1985, an aberrant Middle Devonian ambocoeliid brachiopod genus from China

Here we redescribe and reillustrate specimens of an ambocoeliid brachiopod previously described as Echinocoelia guangsiensis Sun, 1992 from the late Eifelian–earliest Givetian Mingtang Formation of the Liujing section in Guangxi Autonomous Region. The internal structure of the species, and especially the presence of a spondylium with tichorhinum in the ventral valve indicates that the species represents the aberrant genus Cyrtinoides Yudina and Rzhonsnitskaya, 1985. It seems probable that the anterior part of the tichorhinum in Cyrtinoides accommodated the diductor attachments. Geographic distribution of Cyrtinoides is restricted to the Northern Hemisphere and shows a disjunct pattern. This genus has not hitherto been identified from China.     

Two new Middle Devonian megaspores from Saudi Arabia

Two new megaspore species, Biharisporites jubahensis and Verrucisporites yabrinensis, are described from the Middle Devonian Jubah Formation of south central Saudi Arabia. Miospore-based biostratigraphy indicates that the age of the megaspore-bearing interval is no older than the early Givetian Geminospora lemurata Interval Zone, and not younger than Givetian. The presence of similar species in both Arctic Canada and Saudi Arabia suggests that the megaspore-producing plants achieved wide distribution in the Middle Devonian.     

Substrate specific associations of epebionts on Middle Devonian brachiopods: Implications for paleoecology

A detailed study of over 2500 host brachiopods, from the Middle Devonian Hamilton Group of New York State, revealed distinct patterns of epibiont encrustation, that provide insight into taphonomy and paleoautecology of the host brachiopod shells and depositional environments. The concavo‐convex orthid, Tropidoleptus carinatus (Conrad), as well as strophomenid, and smooth athyrid brachiopods are among the most heavily encrusted. However, terebratulids of nearly identical size and shape are relatively clean of epibionts. This selective distribution strongly suggests that epibionts were discouraged from settling on punctate brachiopods. Brachiopods with small spines and frills were also nearly clean of epibionts, possibly because of entrapment of a mud layer, which made the outer layer of the host inhospitable for larval settling. Concavo‐convex taxa reveal high percent coverage and diversity of epibionts on the convex valve, which probably rested on the substrate during the life of brachiopod. This pattern is observed even on brachiopods that were buried with the convex valve downward. This implies complex post‐mortem histories involving multiple episodes of reorientation and colonization.     

A new species of psammosteiform heterostracan (Agnatha) from the Givetian (Middle Devonian) of the Voronezh Region

A new pycnosteid species, Schizosteus shkurlatensis sp. nov. (Agnatha, Psammosteiformes), from the Staryi Oskol beds (Givetian, Middle Devonian) of the Voronezh Region is described. This is the first species of the genus Schizosteus Obruchev from the Central Devonian Field. The similarity between species of this genus and early species of Psammolepis is discussed.     

Earliest ontogeny of Middle Ordovician rhynchonelliform brachiopods (Clitambonitoidea and Polytoechioidea): implications for brachiopod phylogeny

New data on the earliest ontogeny of Mid-Ordovician Baltoscandian clitambonitoid ( Apomatella , Neumania and Oslogonites ) and polytoechioid ( Antigonambonites and Raunites ) brachiopods reveal significant differences in the life history of the taxa belonging to these two superfamilies. The Polytoechioidea and probably other members of the Billingsellida had planktotrophic larvae, in which the dorsal and ventral mantle lobes formed separately and without reversion. The 'pedicle sheath' in Antigonambonites is secreted by a section of modified ventral mantle and thus this 'pedicle' is not homologous within the pedicle of rhynchonellate brachiopods. It is likely that polytoechioids and other members of the strophomenate clade had the same type of ontogeny and mode of attachment. In contrast, the ontogeny and mode of attachment of clitambonitoids are similar to that of recent rhynchonellates: their mantle lobes and both valves formed simultaneously, and the pedicle most likely formed from the larval pedicle lobe. Evidence for the lecithotrophic nature of clitambonitoid larva is discussed. This confirms that the Clitambonitoidea, unlike the Polytoechioidea, represents an ingroup within the Rhynchonellata.     

Lower Devonian brachiopod communities of the northern Canadian Cordillera

The northern Canadian Cordillera can be divided into three more or less parallel arrayed lithofacies, which from east to west correspond to progrcssively deepening waters. The shallow water, yellow, or orange-weathering carbonates occupy essentially the eastern half of the region and northwestern Yukon. Shallowest water carbonates yield fairly abundant ostracodem faunas, ostracodes, and little else. Slightly deeper water carbonates contain brachiopod faunas rich in individuals but low in generic diversity. The name Howellella-Protathyris Community is applied to the Lower Lochkovian shallow water faunas: the Sieberella-Nymphorhynchia-Athyrhynchus Community is the approximate Upper Pragian-Zlichovian equivalent. Deep water calcareous shales and limestones occupy a narrow band and yield faunas rich both in number and diversity. These faunas are designated the Skenidioides-Spirigerina-Vagrania Community and are recognized through the entire Lower Devonian interval. An intermediate depth fauna from Upper Pragian and Zlichovian dark carbonates is probably recognizable in northwestern Yukon, and termed the Strophochonetes-Proreticularia- receptaculitid Community. The widespread deep water graptolitic shales and carbonates contain a rich fauna of graptolites and relatively rare trilobite, sponge, and brachiopod faunas.     

Biostratinomy and functional morphology of enrollment in two Middle Devonian trilobites

Although it is common knowledge that many trilobites enrolled, behavioral and functional aspects of enrollment are not at all well understood. Taphonomic details portrayed by enrolled trilobites in the Middle Devonian Hamilton Group (New York State) indicate that enrollment was a complex and morphologically constrained behavior. The trilobites Phacops rana (Green) and Greenops boothi (Green) are frequently enrolled in Hamilton strata; biostratinomic data indicate two very different enrollment postures. Interlocking morphologies (coaptative devices) and apodeme structure and disposition indicate that these postures reflect specific behaviors which involved interaction between tergal structures, inferred musculature, and the substratum. Phacops enrolled by burrowing forward and down into the sediment; dorsal muscles, attached to prominent articulating half-rings, imbricated the thorax such that each lappet overlapped the next posterior segment and locked into a posterior pleural facet. The pygidium was brought into place as the posterior segments of the thorax were placed into vincular notches along the lateral margin of the ventral cephalon. The pygidium locked with the cephalic vincular furrow to complete ‘perfect sphaeroidal’ closure. Greenops enrolled with the cephalon in an upright position at the sediment surface; a submarginal furrow on the ventral surface of the pygidium received the anterior rim of the cephalon. Relatively narrow articulating half-rings limited pleural rotation. Segments were loosely locked into narrow facets at the anterior margin of the next posterior lappet. In spite of rudimentary lappet and half-ring structures, Greenops displays an elaborate system of thoracopygidial muscles which involved dorsoventral and longitudinal attachments along the thorax and into the pygidium. Phacops, in contrast, displays very poorly developed apodemes which occur in the thorax only. Longitudinal muscle strength was likely less important during Phacops enrollment than is evident for the Greenops enrollment procedure. Conversely, Phacops clearly relied to a great degree upon competent closure devices which are poorly developed in Greenops. Biostratinomic data reveal different enrollment behaviors which reflect the function of different enrollment-related morphologies present in each species.     

A New Jawless Vertebrate from the Middle Devonian of Scotland

A new jawless vertebrate, Cornovichthys blaauweni gen. et sp. nov., is described from a single complete specimen from the Achanarras fish bed at Achanarras Quarry in Caithness, northern Scotland. The Achanarras fish bed consists of lacustrine laminites and was deposited in a major deep-water phase of the Orcadian lake during the deposition of the cyclic Caithness Flagstone Group. The Achanarras fish bed is of Middle Devonian (Eifelian) age. The new animal compares closely with Euphanerops, one ofthe Frasnian 'anaspids' (Hyperoartii) of the Escuminac Formation at Miguasha, Quebec, Canada.     

Marine benthic communities in the Upper Devonian of New York

Four distinctive benthic communities occur in the mid-shelf deltaic deposits of the Upper Devonian Sonyea Group: the Bellerophon Community, dominated by herbivorous gastropods and deposit-feeding bivalves; the Prodrtctella Community, dominated by brachiopods with adaptations for life on muddy substrata; the Cypricardella Community, dominated by bivalves and brachiopods with a variety of adaptations; and the Rhipidomella Community, dominated by brachiopods adapted for life on sandy substrata. The geographic and stratigraphic occurrence of the communities suggest that their distribution was controlled by two principal sets of environmental variables: (1) onshore to offshore gradients in salinity, dissolved oxygen concentrations, and sedimentary substrata, and (2) rate of delta progradation. A change in the rate of delta build-out during mid-Sonyea time led to a dramatic change in onshore to offshore community patterns. The change suggests that great care must be used in constructing generalized community models for longer intervals of Paleozoic time.     

Microbial impacts on the genesis of Lower Devonian reefal limestones, eastern Australia

Microbial contributions to reefal limestones are evident in eastern Australian Lower Devonian microbial frame/bindstones, red algal-microbial-stromatoporoid bindstones, and microbial-stromatoporoid bindstones. Varied microbialite textures, such as stromatolites, thrombolites, and leiolites, originated as accumulations and partial aggregations of calcimicrobes, peloids, and micrites, which also derived from microbial activities. In microbial frame/bindstones, calcimicrobes (e.g., Rothpletzella and Wetheredella) and dense micrite layers covered and bound underlying substrates. Stabilized substrates promoted the subsequent construction of layered, domal, and columnar frameworks, which were produced by combined accumulations and intermixed associations of calcimicrobes and micritic microbialites. Microbes flourished in the microbial-stromatoporoid bindstones and red algal-microbial-stromatoporoid bindstones during repeated growth interruptions of the framework-building skeletal organisms. Microbes bored into and eroded the skeletal frameworks to subsequently leave micritic envelopes, on which microbial and skeletal encrustations took place in turn. The importance of microbial colonization on the skeletal frameworks was first as subsidiary encrusters that helped to preserve them from erosion, and second as modifiers of the spaces suitable for succeeding encrusters. Partial aggregations of Renalcis filled in the interstices of the skeletal and microbial frameworks, thereby enhancing their rigidity.The microbial impacts on the genesis of reefal limestones are: (1) origination of components (calcimicrobes, peloids, and micrites); (2) formation of characteristic microbial textures; (3) main and subsidiary reef construction and encrustation; and (4) destruction of these components, textures, and structures, but also the protection of resultant constructions in turn. The Lower Devonian reefal limestones treated herein, surprisingly, preserve excellent records of a variety of microbial impacts. Similar effects may also have been common, although variable in preservation, in other ancient reefal deposits.     

Integrated Middle Devonian chitinozoan and miospore zonation of the Amazonas Basin, northern Brazil

Middle Devonian chitinozoans were studied from 13 deep wells in the central part of the Amazonas Basin, northern Brazil, and compared with a newly established regional miospore zonation. Of the 23 chitinozoan species encountered, four are newly described: Ancyrochitina multibrachiata, Lagenochitina praeavelinoi, Ramochitina autasmirimense, and Ramochitina herculesi and seven species are retained in open nomenclature because of an insufficient number of well-preserved specimens. The stratigraphic intervals investigated herein correspond to three miospore interval range zones previously defined for the Amazonas Basin, namely, the Grandispora/Samarisporites spp. (GS); late Emsian-early Eifelian, Grandispora permulta (Per); late early Eifelian through the Eifelian-Givetian transition, and Geminospora lemurata-Chelinospora ex. gr. ligurata (LLi); early Givetian. A regional Middle Devonian chitinozoan biozonation, also consisting of three zones, is proposed for the investigated interval. These zones are the interval zone of Angochitina n. sp. A (early Eifelian), the interval zone of Alpenachitina eisenacki (late early to late Eifelian), and the total range zone of Ramochitina stiphrospinata (early Givetian).     

Functional adaptation of spiriferide brachiopod morphology

It has been suggested that spiriferide morphologies have evolved to adapt to a variety of environmental conditions. Through a computational fluid dynamics approach, we examined how the spiriferide original form was optimized for a lotic condition, specifically addressing the functionalization of the Devonian spiriferide brachiopod Paraspirifer bownockeri to generate passive feeding flows. The results using four models, each of which differed in the development of the spiriferide shell depression, i.e. sulcus, showed that a deeper sulcus functions to create strong spiral flows so as to align on the feeding organ inside the shell. Among the sulcus‐developed models, only the mimic of the natural form could generate comparative slow flows with a stable inflow area. The fossil record of spiriferides shows a morphological trade‐off between the development of the sulcus and wing form. We concluded that spiriferide shells with such a morphological combination evolved to produce various feeding strategies, resulting in diversification.     

Ribbing patterns in the brachiopod Diceromyonia

Ribbing patterns in two collections of the Ordovician brachiopod Diceromyonia from central North America are compared using the system invented by Bancroft (1928; Manchester Memoirs 72 ) for naming ribs. Simple and nearly symmetric arrangements of frequently occurring branches characterize both collections, with much of the complexity evident in larger valves due to irregular occurrence of low-frequency branches on either side of major ribs. Examination of median sectors reveals little support for Bancroft's derivation of the rhipidomelloid midrib from isorthoid forms, and an alternative non-evolutionary interpretation is proposed in which median patterns appear as predictable outcomes of a simple space-filling process. The approximately 2500 ribs identified in this study are treated as a population in their own right: orderly patterns which emerge are not inferred but are simple summaries of complete counts, obtained by hand. This approach is quick and painless compared to methods using order relations to assess ribbing differences in dalmanellid brachiopods. For this reason, it may encourage systematic study of ribbing patterns among these taxa and lead ultimately to better understanding of the utility of ribbing in their taxonomy.     

A new genus of lycopods from the Devonian of New York State

Drepanophycus colophyllus Grierson & Banks is transferred to llaskinsia Grierson & Banks on the basis of the morphology of its leaves and its anatomical structure. Slender, dichotomizing axes bear helically arranged leaves that are falcate, petiolate, simple, lanceolate and entire. A solid cylinder of metaxylem is surrounded by ridges of protoxylem. Pitting on tracheid walls is annular, helical, reticulate, scalariform to circular-bordered. This lycopod extends from early Givetian into early Frasnian time in the Catskill strata of eastern New York State. The effect of cleavage of fossiliferous rock on patterns observed on the exposed fossils and the bearing of recent research on the fossil history of lycopods are discussed.     

A New Naked Jawless Vertebrate From The Middle Devonian Of Scotland

A new jawless vertebrate, Achanarella trewini gen. et sp. nov., is described from some recently discovered, relatively well–preserved specimens from the Achanarras fish bed at Achanarras Quarry, northern Scotland. The Achanarras fish bed is of Middle Devonian (Eifelian) age. Achanarella is a torpedo–shaped jawless vertebrate with a strongly hypocercal tail and well–developed anal fin. It has at least 13 branchial openings with possibly more than 20. It is scaleless. Achanarella compares well with the Frasnian Euphaneropidae of the Escuminac Formation in Quebec, Canada, and Cornovichthys blaauweni Newman and Trewin, 2001, also from the Achanarras fish bed. It differs from these forms mainly in being extremely long and thin and having a very small head compared with body length.     

Brachiopods from the family Ambocoeliidae George (Order Spiriferida) from the Emsian (Lower Devonian) of northeastern Russia

Brachiopods from the family Ambocoeliidae George from the Emsian (Lower Devonian) of northeastern Russia are described: Bisinocoelia despecta sp. nov.; Yakutospirifer gen. nov. with the type species Y. krivensis sp. nov.; Micospirifer gen. nov. with the type species M. simplex sp. nov.; Kolymospirifer gen. nov. with the type species K. optatus sp. nov. (subfamily Ambocoeliinae); Datnospirifer gen. nov. with the type species D. alius sp. nov.; Khalimospirifer gen. nov. with the type species Kh. microscopicus sp. nov.; Gerospirifer gen. nov. with the type species G. normalis sp. nov., and G. gerensis sp. nov.; Dogdospirifer gen. nov. with the type species D. yolkini sp. nov. (subfamily Rhynchospiriferinae).     

A new Middle Devonian gasterocomid crinoid from central Turkey and revision of the Gasterocomidae

A juvenile cup, disarticulated arm plates, and columnals of the crinoid Arachnocrinus sarizensis n. sp. are described from the Eastern Taurus Mountains of central Turkey. This is the first Paleozoic crinoid based on a cup and arm plates reported from Turkey. Suggested revision of the Gasterocomidae includes transfer of Arachnocrinus and Ancyrocrinus to the family and rejection of Kopficrinus from the family. The stratigraphic range of Arachnocrinus is extended upward into the Middle Devonian from the Early Devonian. The Devonian of Turkey is of special interest because it includes Laurasian and Gondwanan components on different tectonic blocks. The paleogeographic range of Arachnocrinus is extended from the North American plate onto the Anatolian block, which would have been located on the southern edge of the Paleotethys Sea in the Middle Devonian in a shelf basin off the northern coast of Gondwana at approximately 42° south latitude.     

Discussion of the Early Devonian rhynchonellid brachiopod genus Borealirhynchia Su, 1976

The Early Devonian brachiopod genus Borealirhynchia was established by Su, 1976. Phylum Brachiopoda (Cambrian to Devonian). In: Paleontological Atlas of North China, Inner Mongolia Volume 1. Geological Publishing House Beijing, pp. 155-227 (in Chinese). It has not been previously described in detail, nor have transverse serial sections of the internal features of Borealirhynchia delerensis, the type species, been published. In this paper Borealirhynchia, along with a few species previously assigned to it, is analysed and discussed. Detailed transverse serial sections of the internal features of B.? lata Su, 1976, are provided, based on well-preserved specimens collected from the Lower Devonian strata of Dong Ujimqin Qi, northeastern Inner Mongolia. Borealirhynchia? gigantea Su, 1976 and Latonotoechia multicosta Su, 1976 are considered to be synonyms of B.? lata Su with the same external and internal characters present in all three species. Some Lower Devonian strata, in which Borealirhynchia was found and reported, from Dong Ujimqin Qi, northeastern Inner Mongolia, are fully described.