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.     

Age and distribution of the Late Devonian brachiopod genus Dzieduszyckia Siemiradzki, 1909 in southern China

Conodont biostratigraphical work was done at four sections recently found with occurrence of the rhynchonellide brachiopod genus, Dzieduszyckia Siemiradzki, in southern Guangxi and in the border area between Dushan County of Guizhou and Nandan County of Guangxi, South China. These sections represent two different types of facies, i.e., carbonate platform and intraplatform basin. The conodont analysis reveals that this genus occurs in the Upper triangularis Zone and the Middle crepida Zone at the Dazhai Section, through the Lower to Upper crepida zones at Dalong, and is restricted within the Upper rhomboidea Zone at the two intraplatform basin sections (Changtang and Duli). This result demonstrates that the occurrence of these peculiar rhynchonellide brachiopods in South China, regardless of the depositional environments, is within the Lower Famennian instead of the previously suggested Upper Famennian. Furthermore, this brachiopod genus in South China began to inhabit on the carbonate platform almost since the beginning of the Famennian and did not extend to the intraplatform basin facies until the late Early Famennian.Available biostratigraphic data indicate that during the Early and Middle Famennian, Dzieduszyckia is widely distributed not only in South China, but also throughout the world, such as Morocco and southern Ural.Observation on the new collections from the four studied sections reveals that the peculiar rhynchonellide brachiopods have a great morphological variation within each section. Significant differences existed among the collections from different sedimentary settings and localities, probably reflecting the environmental and geographic constraint on the morphology of Dzieduszyckia. Samples from different layers in the same section have nearly identical morphological variation, suggesting the temporal inheritance in morphology of the rhynchonellide brachiopod.     

Level-bottom brachiopod communities in the Middle Devonian of New York

Depositional environments of the Onondaga Limestone from central to southeastern New York are found to be normal, subtidal marine, due to the absence of characteristic supratidal or intertidal sedimentary features and the presence of a typical, diverse, marine level-bottom community framework. Post-mortem transport has not been extensive, as evidenced by low articulation ratios, lack of abraded valves, and complete ontogenetic gradations within species, which precludes large scale winnowing. Sedimentation rates appear to have been greatest in eastern New York where the Onondaga Limestone reaches a thickness almost three times that of the strata in central New York. Shaly beds in the central area represent periods of cessation of carbonate deposition rather than an influx of clastic material. Deposition terminated with the onset of deeper water characterized by a westerly advance of terrigenous sedimentation (the Marceilus Shale of the Hamilton Group). Nine brachiopod communities can be recognized in the Onondaga Limestone. There is a strong correlation between sediment-substrate and community type, reflecting the sedimentologic control of brachiopod community distribution. Sandy facies, cherty limestones and coral biostromes and bioherms are associated with inner-neritic deposition in Edgecliff time; argillaceous lime muds and lime sands are characteristic of mid-neritic deposition in Nedrow to Moorehouse time; and highly argillaceous lime muds are associated with outer-nerittc deposition in Seneca time.     

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.     

Notes on a fertile rhyniophytoid from the Lower Devonian of Guangxi,southwestern China

A fertile rhyniophytoid is discovered from the Lower Devonian of Guangxi, southwestern China, which is characterised by small size, dichotomous branchings and terminal sporangia. This plant is similar to the genus Aberlemnia Gonez et Gerrienne and also, is comparable to some mesofossil morphotypes of early land plants from the Early Devonian (Lochkovian) Old Red Sandstone floras. This study adds new data to the generally zosterophyll-dominated Early Devonian floras of South China and sheds some lights on the palaeophytogeography of rhyniophytoids.     

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.     

Growth forms and palaeoenvironmental interpretation of stromatoporoids in a Middle Devonian reef, southern Morocco (west Sahara)

Growth forms of well-preserved stromatoporoids, including genera Actinostroma, Stachyodes, and Stromatopora, are described for the first time from the Devonian Sabkhat Lafayrina reef complex of southern Morocco (west Sahara), one of the best exposed Middle-Devonian stromatoporoid-dominated fossil reefs. Three facies types representing the well illuminated fore-reef, reef-core and transition to back-reef facies display the distribution and growth of stromatoporoids in a high latitude setting at 40–50° south of the palaeoequator. Stromatoporoids are largely in growth position and reflect the well-preserved reef architecture. Although outcrops are low topography, the reef's prominent profile is indicated by presence of spur and groove form and a clearly defined reef margin. Stromatoporoids are mostly laminar and domical forms, with little evidence of ragged margins, and indicate normal turbulence shallow waters, with low sediment deposition.     

An anatomically preserved lycopsid from the Upper Devonian of South China

An anatomically preserved lycopsid, Lobodendron fanwanensegen. et sp. nov. Liu, Wang, Xue & Meng, is described from the Upper Devonian (Famennian) Wutong Formation of Changxing County, Zhejiang Province, China. The fossil plant bears slender, dichotomously branched axes. The vascular strand consists of solid terete primary xylem and lobed secondary xylem, which implies the result from the activity of possibly discontinuous cambium. The new plant has character combinations that do not conform to any branches in the canopy of the tree-lycopsids known previously, but resemble those of the basal part of some pseudoherbaceous lycopsids. This new plant may exemplify a Late Devonian lycopsid with a pseudoherbaceous growth habit.     

Anatomical reinvestigation ofArchaeopteris macilenta from the Upper Devonian (Frasnian) of South China

Archaeopteris macilenta is one of the most widespread plants in the Late Devonian.Based on fossils from the Frasnian Huangjiadeng Formation,Yichang District of Hubei Province,for the first time we study in detail the anatomy of this progymnosperm plant in South China.Ultimate axes are protostelic with three xylem sympodia and lack secondary tissue.Penultimate axes are eustelic,bearing eight sympodia and a thin band of secondary xylem.Radially symmetrical sympodia of mesarch primary xylem produce traces of appendages in a spiral arrangement.Archaeopteris macilenta and A.halliana (A.roemeriana) are dominant in the Frasnian and Famennian,respectively.Comparisons with these two species from other tectonic plates indicate consistent stelar architectures.Global spread,continuous occurrence,and identical anatomy during the Late Devonian indicate that Archaeopteris survived the Frasnian-Famennian extinction event.In this time,endemic genera and cosmopolitan taxa,including Archaeopteris,suggest the palaeogeographic isolation of South China and certain associations with other plates.     

Miospore stratigraphy of Lower and early Middle Devonian deposits from Tidikelt, Central Sahara, Algeria

The Tidikelt region forms an outstanding area for subsurface Lower Devonian stratigraphy in the central Algerian Sahara. Sediments from five boreholes have revealed abundant and diverse assemblages of miospores, acritarchs, chitinozoa, scolecodont and microplant remains. The miospores are moderately well preserved. Three new miospore species (Dibolisporites saharansis nov. sp. Hassan Kermandji, Acinosporites conatus nov. sp. Hassan Kermandji and Scylaspora tidikeltense nov. sp. Hassan Kermandji) are described. Miospore assemblages vary through the regressive and transgressive sequences. Seven miospore assemblage biozones, including six new miospore assemblage biozones (Scylaspora tidikeltense-Perotrilites microbaculatus, Dictyotriletes emsiensis-Emphanisporites spinaeformis, Apiculiretusispora arenorugosa-Camptozonotriletes caperatus, Verrucosisporites polygonalis-Dictyotriletes subgranifer, Emphanisporites annulatus-Geminospora svalbardiae, Hystricosporites microancyreus-Grandispora protea, Calyptosporites velatus-Rhabdosporites langii) are proposed for the Lower and early Middle Devonian rocks of Tidikelt Plateau. The combined use of distinctive, wide distribution cosmopolitan and Gondwanan forms as biozonal and species characteristics permits accurate subdivision, dating and correlation of Tidikelt successions with other similar miospore zones of the Lower Devonian of Europe, Canada and other parts of Gondwana plate. The miospore data provide new explanations to stratigraphic relationships of regional rock units, sedimentary cycles and stratigraphic hiatus. The miospore biozones are proposed as a provincial biozonation, which may also be applied to other Palaeozoic rocks of similar miospore content.     

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.     

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.     

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).     

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 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.     

Vent and mound rugose coral associations from the Middle Devonian of Hamar Laghdad (Anti-Atlas, Morocco)

Peculiar associations of small, solitary, deep-water rugose corals are described from the Middle Devonian buildups situated in the easternmost part of Hamar Laghdad area of southern Morocco. The most of them are monospecific and consist of simplified taxon “Amplexus” florescens but one is polyspecific and composed of specimens belonging to four different species representing three families. These rugosan associations form isolated nest-like aggregations where numerous densely packed specimens are arranged mostly in life position. The polyspecific and two monospecific associations are interpreted as growing in close proximity to venting fields. They reveal a unique “calice-in-calice” recolonization pattern expressed by successive settlement of juvenile specimens in the calice of dead individuals. This pattern was presumably a consequence of selective survival of coral larvae settling in extreme vent habitats. Although, the “calice-in-calice” pattern is common in both, mono- and polyspecific associations, there are differences expressed in the character of larval attachments and various types of the calice fillings. The trophic interaction between corals and ostracods is discussed. Additionally, associations of “Amplexus” florescens, not displaying “calice-in-calice” pattern of growth have been found within the mound where polyspecific association occurs. These are interpreted as growing away from venting fields. Comparisons of Amplexus-type coral faunas with the other North African and European corals allow the classification of these ampleximorph rugosan taxa as characteristic biotic components of the Middle Devonian mound environments influenced by venting activity. Two new genera and species, Weyeraia prima and Vesiculolasma erfoudi, are introduced.     

Early to Middle Devonian miospores from northern Saudi Arabia

Well-preserved palynomorph assemblages are recovered from the Devonian Jauf and Jubah formations in five shallow boreholes in the northern part of Saudi Arabia. These fully cored boreholes overlap stratigraphically to form a 1640 ft composite sequence. Miospores dominate the palynological assemblages of most samples. The assemblages are mainly composed of trilete spores but also contain cryptospores and monolete spores. One new genus, sixteen new species and two new varieties of miospores are described from the studied assemblages: Artemopyrainconspicua nov. sp., Artemopyrarecticosta nov. sp., Camarozonotriletesfilatoffii nov. sp., Camarozonotriletesrugulosus nov. sp., Cymbohilatesbaqaensis nov. sp., Cymbohilatescomptulus nov. sp., Cymbohilatesheteroverrucosus nov. sp., Cymbosporitesasymmetricus nov. sp., Dibolisporitespilatus nov. sp., Dictyotriletesbiornatus nov. sp., Gneudnasporadivellomedia (Chibrikova) Balme, 1988 var. divellomedia, Gneudnasporadivellomedia (Chibrikova) Balme, 1988 var. minor nov. var., Latosporitesovalis nov. sp., Scylasporacostulosa nov. sp., Squamisporaarabica nov. gen. and sp., Stellatisporamulticostata nov. sp., Zonotriletesarmillatus nov. sp. and Zonotriletessimplicissimus nov. sp. Their stratigraphic distribution is compared to the well-established Devonian West European zonation of Streel et al. (1987) (Streel, M., Higgs, K.T., Loboziak, S., Riegel, W., Steemans, P., 1987. Spore stratigraphy and correlation with faunas and floras in the type marine Devonian of the Ardenne-Rhenish region. Review of Palaeobotany and Palynology 50, 211-219). A late Pragian-Givetian age is suggested for this sequence. No characteristic Eifelian taxa are recorded, but this could be explained by a gap in palyniferous samples.     

The problematic cemented Devonian brachiopod Schuchertellopsis durbutensis Maillieux, 1939

The Devonian cemented brachiopod Schuchertellopsis durbutensis has proved difficult to classify and its possible taxonomic relationships are unknown. Morphologically Schuchertellopsis resembles more closely members of the Orthotetidina than the Davidsoniidina. Examination of the shell structure, a key diagnostic feature of the Orthotetidina, shows that Schuchertellopsis has the cross laminar secondary shell typical of all orthotetidines. However, the presence of both pseudopunctate and incipient an extropunctate fabric within the ventral valve is unique amongst orthotetidine brachiopods and is thought to represent a phase of shell fabric experimentation. Schuchertellopsis probably fits most comfortably within the Schuchertellidae, and is the earliest representative of that family.     

A neotype for Coipodexylon gracilentum Dou (Lycopsida) from the Middle Devonian of North Xinjiang, China

According to newly collected and well preserved specimens,herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang,NW China are reduced to C.gracilentum,for which a neotype is designated and emended diagnosis is given.Colpodexylon gracilentum has leaves with three nearly equal segmems,an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.