A New Ichnospecies of Arthrophycus from the Late Carboniferous (Pennsylvanian) of Michigan,USA

A unique ichnofossil assemblage from Pennsylvanian-age sandstones near Eaton Rapids, Michigan, USA, comprises straight-to-curved traces preserved in convex hyporelief, with the transverse ridges and median grove associated with the ichnogenus Arthrophycus. The Michigan traces show some branching or pseudo-branching (also known from other Arthrophycus specimens) and are among the smallest structures (millimeters in diameter) attributed to this ichnogenus. The orientation of the Michigan Arthrophycus burrows is distinct from other ichnospecies of this taxon in the pronounced co-planar alignment of the burrows, as opposed to the multiplanar, interweaving, “bundled” nature typical of the ichnogenus. On this basis we assign the Michigan specimens to a new ichnospecies of Arthrophycus. The “paralleling behavior” of the new taxon may reflect a strategy of the tracemaker to avoid previous burrows and reflect differences in resource availability or current energy. This new taxon supports previous records of the occurrence of this ichnogenus in Upper Carboniferous strata.     

The changing face of the deep: Colonization of the Early Ordovician deep-sea floor, Puna, northwest Argentina

An Upper Tremadocian deep-sea ichnofauna from the Chiquero Formation of Puna, northwest Argentina, represents a link between Ediacaran and Cambrian microbial-mat dominated ecosystems and younger Ordovician deep-marine trace-fossil assemblages. This ichnofauna is preserved at the base of thin-bedded turbidites formed in the lobe fringe of a back-arc deep-sea fan. While Ediacaran–Cambrian deep-marine trace fossils are typically linked to matground grazing and feeding, microbial textures in the Chiquero Formation are rare and not associated with trace fossils. Morphologic patterns (e.g. radial trace fossils and networks) of the Chiquero ichnofauna indicate the onset of novel trophic types, recording trapping of microorganisms and bacterial farming. However, in comparison with younger Ordovician deep-sea ichnofaunas, graphoglyptids are relatively rare, poorly diverse, and geometrically simpler. This study indicates that the Early Ordovician was a pivotal point in the ecology of deep-sea infaunal communities. This Upper Tremadocian ichnofauna records the arrival of the Agronomic Revolution to the deep sea. Comparisons with slightly older and younger deep-sea ichnofaunas demonstrate that the colonization of the deep sea was a protracted process spanning the Early Paleozoic, lagging behind colonization of nearshore and offshore substrates.     

Gyrophyllites cristinae isp. nov. from Lower Ordovician Shallow-Marine Deposits of Northwest Argentina

Abstract

The lower Paleozoic marine siliciclastic succession of the Central Andean Basin, northwestern Argentina, provides a valuable record of the onset of the Great Ordovician Biodiversification Event in western Gondwana. A new ichnospecies of rosette trace fossil, Gyrophyllites cristinae, is documented from lower and upper Tremadocian (Tr1 and Tr2) deposits of this basin. It is characterized by five to six non-overlapping petaloid lobes and can be easily differentiated from the other four formally defined ichnospecies. Gyrophyllites cristinae occurs at the top of hummocky cross-stratified sandstone regularly interbedded with mudstone. These deposits are interpreted as reflecting the alternation of high-energy storm events and low-energy fair-weather conditions immediately below the fair-weather wave base, representing deposition in offshore transition environments. Gyrophyllites has been traditionally interpreted as the product of worms of uncertain taxonomic affinity that mined the sediment in search for food (fodinichnia). The occurrence of Gyrophyllites cristinae in these Ordovician deposits records post-storm colonization. Storms may have increased oxygenation and supplied fresh organic detritus that were exploited by worm-like, surface detritus- or shallow deposit-feeders exploring the uppermost silt-rich fine-grained sediments.     

New graptolite,chitinozoan and acritarch records from the Pascha-Incamayo area,Cordillera Oriental,Argentina

A new fossil assemblage bearing graptolites, chitinozoans and acritarchs is analyzed based on material collected in the Pascha-Incamayo area, Salta Province, NW Argentina. The occurrence of Hunnegraptus copiosus (Lindholm, 1991), associated with specimens of the genus Tetragraptus (Salter, 1863), is highly relevant to improve the age assignment and correlate the fossil-bearing levels previously assigned to the Devendeus Formation. Different stages in the development of the index species of the Upper Tremadocian H. copiosus Biozone are described and illustrated. The precise stratigraphic ranges of the associated chitinozoans and acritarchs are discussed, according to the biostratigraphic analysis, and the stratigraphic relationships for the studied section are considered.     

Cambrian Acritarchs from the Col di Foglia (Agordo) southalpine metamorphic basement, Italian Eastern Alps: the oldest biostratigraphic record in the alps

Abstract  The Lower Palaeozoic biostratigraphic records in the Alps are briefly reviewed and the result of a new study of the acritarch assemblage found by Sassi et al. (1984) in the greenschist facies black metapelites of the Southalpine metamorphic basement at Col di Foglia, and studied by Kalvacheva et al. (1986), is presented. The new  taxonomic and biostratigraphic study indicates a late Cambrian age, which is the oldest unquestionable, recently assessed, biostratigraphic dating of the entire Alps, as well as of the Italian peninsular. Keywords Alps, Southalpine metamorphic basement, Eastern Alps, Agordo, Acritarchs, Cambrian Subject codes: G17002     

Ichnological analysis of Jurassic shallow to marginal marine deposits: example from Wagad Highland,Western India

Abstract

Jurassic deposits of shallow to marginal marine (delta) environments are widely reported from different continents of the world. This study shows inter-relationship of the animal-sediment behaviours in shallow and marginal marine conditions, suggesting an interpretation of the possible ichnodisparity. The Jurassic succession exposed at Washtawa Dome and Adhoi Anticline of Wagad highland, Kachchh comprises an approximately 341 m thick succession, divided into two formations – Lower Washtawa and Upper Wagad Sandstone. Eight sparsely to highly bioturbated sedimentary units show twenty-three identifiable ichnospecies from fifteen ichnogenera representing five ichnoassemblages broadly attributable to the Skolithos and the Cruziana ichnofacies, and developed in shallow-marine strandplain shoreface and delta depositional facies. The relative frequency statistical data reveals the dominant occurrence of feeding structures generated by polychaetes preferentially in quartz arenites. These structures represent sub-horizontal, sub-vertical and complex burrows, and show twelve and six categories of architectural designing Callovian-Oxfordian of shallow-marine shoreface and Oxfordian-Kimmeridgian shallow-water delta successions, respectively. The lower ichnodiversity and ichnodisparity associated with the Oxfordian-Kimmeridgian deltaic intervals represents a decrease in the exploitation of under-used ecospace, due to unfavourable environmental conditions rather than an expression of evolutionary radiation.     

New ichnospecies of Linichnus Jacobsen & Bromley, 2009

Abstract

A new ichnospecies, Linichnus bromleyi, is described on bone substrate as the result of a very likely predator/scavenger interaction. L. bromleyi consists of a single groove with a non-serrated edge. This new ichnotaxon is compared with L. serratus which was defined as a single elongate serrate-edged groove. L. bromleyi has been identified over the surface of bones of marine mammals (in particular, cetaceans and pinnipeds) from two Pliocene outcrops of Andalusia, southern Spain. The new ichnospecies can be clearly related with a trophic interaction between sharks and marine mammals (mainly whales, dolphins and seals).     

Review of Japanese Dinosaur Track Localities: Implications for Ichnotaxonomy,Paleogeography and Stratigraphic Correlation

Nine dinosaur ichnospecies from the Lower Jurassic to Upper Cretaceous of Japan, including two that are new, are described herein. The new ichnotaxa are Asianopodus pulvinicalx ichnogen. et ichnosp. nov. and Schizograllator otariensis ichnosp. nov. The Japanese ichnotaxa are allied to Lower Jurassic ichnospecies in South China, North America, Western Europe and South Africa, and Upper Jurassic to Lower Cretaceous ichnospecies from Southeast and East Asia. This suggests they were part of a global ichnofauna before continental drift began in the Middle Jurassic, leading to the development of a more endemic dinosaur fauna in the Cretaceous. At least two assemblages, an ornithopod-gracile-toed theropod-dominated community, in northeastern Asia, and a robust theropod- and sauropod-dominated community in the southern part of the continent, existed in the Cretaceous. This parallels North American dinosaur distribution patterns in the Cretaceous and seems to be a reflection of paleolatitudinal controls.     

山东潍坊寒武系苗岭统乌溜阶馒头组上部的腕足动物

寒武系腕足动物属种多样性高、个体数量丰富、形态差异明显、地理分布广泛,具有辅助寒武系三叶虫生物地层划分和对比的潜力。华北板块寒武系苗岭统沉积和化石记录发育良好,是中国苗岭统的经典研究区之一。前人已针对华北寒武系苗岭统乌溜阶腕足动物的系统古生物学开展了一系列基础工作,但这些相关研究主要集中于辽宁地区,目前对华北其他地区苗岭统乌溜阶腕足动物的研究程度仍然有限,相关生物地层学也有待进一步探索。本文首次系统描述了山东潍坊寒武系苗岭统乌溜阶馒头组上部碎屑岩中的腕足动物,共鉴定出舌形贝型亚门4属5种,包括馒头组洪河段的舌孔贝未定种Lingulellotreta sp.indet.以及馒头组上页岩段的山西小舌形贝Lingulella shansiensia(Walcott,1905)、德姆斯小舌形贝Lingulella damesi (Walcott,1905)、伊瑞克乳房贝Acrothele eryx (Walcott,1905)和东方原孔贝Prototreta orientalis(Resser and Endo,1937)。值得注意的是,在馒头组上页岩段的3层岩性略有差异的泥岩中,分布着3层完全不同的腕足动物,共有4种,但这3个组合都位于Bailiella lantenoisi带这一三叶虫生物带。腕足动物组合在极短时间内的快速交替现象,表明了腕足动物对环境背景的微弱变化具有较强的响应。     

Trace fossils in the Ediacaran-Cambrian transition: Behavioral diversification, ecological turnover and environmental shift

After taxonomic revision, trace fossils show a similarly explosive diversification in the Ediacaran-Cambrian transition as metazoan body fossils. In shallow-marine deposits of Ediacaran age, trace fossils are horizontal, simple and rare, and display feeding strategies related to exploitation of microbial matgrounds. Equally notable is the absence of arthropod tracks and sinusoidal nematode trails. This situation changed in the Early Cambrian, when a dramatic increase in the diversity of distinct ichnotaxa is associated was followed by the onset of vertical bioturbation and the disappearance of a matground-based ecology (‘‘agronomic revolution’’). On deep sea bottoms, animals have been present already in the Ediacaran, but ichnofaunas were poorly diverse and dominated by the horizontal burrows of undermat miners. As shown by the ichnogenus Oldhamia, this life style continued to be predominant into the Early, and to a lesser extent, Middle Cambrian. Nevertheless, there was an explosive radiation of behavioral programs during the Early Cambrian. When exactly the bioturbational revolution arrived in the deep sea is uncertain. In any case, the Nereites ichnofacies was firmly established in the Early Ordovician. The rich ichnofauna in the Early Cambrian Guachos Formation of northwest Argentina probably marks a first step in this ecological onshore-offshore shift.     

Upper Cambrian-Ordovician successions overlying Timanian complexes: new evidence of acritarchs and brachiopods from Kolguev Island, Arctic Russia

Drillholes to several kilometres depth on Kolguev Island in the southern Barents Sea have sampled early Palaeozoic successions, known elsewhere in the Pechora Basin to overlie Neoproterozoic basement complexes. New studies on acritarch microfossils from the lowermost part of the Palaeozoic succession (c. 4500 m depth), reached by the Bugrino 1 and North-Western 202 boreholes, revealed diverse and biostratigraphically significant assemblages, which indicate the position of the Cambrian-Ordovician boundary in a sedimentologically continuous offshore marine succession. Upper Cambrian strata equivalent to the Peltura and Acerocare zones are distinguished on the basis of common taxa known from the neighbouring East European Platform and other areas in Baltica, Avalonia, and Gondwana. Invertebrate faunas, including brachiopods, problematic mollusc and phyllocarid arthropods, are revised taxonomically; they are indicative for the Tremadocian and Arenigian stages in the upper part of the succession. The Cambrian strata are insofar documented by fossil record only on the Kolguev Island, although their extension (of various series) in other areas of the Pechora Basin is claimed on the grounds of geophysical data and/or is inferred from geological successions. This new biostratigraphic evidence and facies development suggest that the Upper Cambrian-Tremadocian platformal deposits were likely widely distributed over the northeastern Baltica, as they were in the East European Platform and Baltoscandia. They were accumulated on a stable and passive margin of the craton with steady subsidence and a high rate of sedimentation.     

Additional observations on the gross morphology and microstructure of Baccaconularia Hughes, Gunderson et Weedon, 2000, a Cambrian (Furongian) conulariid from the north-central USA

Baccaconularia Hughes, Gunderson et Weedon, 2000, from the Furongian Series (Cambrian System) of the north-central USA, has been interpreted as a conulariid cnidarian, based on a suite of gross morphological similarities shared only with other post-Cambrian genera currently assigned to this group. Closely spaced, squarish to subrectangular facial nodes of Baccaconularia are aligned in distinct longitudinal files. Nodes also display a subtler, more or less rectilinear transverse alignment, though this pattern commonly is disrupted by offset parallel to the longitudinal files. In their shape and pattern of arrangement, the nodes of Baccaconularia are most similar to the squarish to elongate nodes of Pseudoconularia Bouček, 1939. Longitudinal node files of Baccaconularia may also be compared with the longitudinal facial ridges of Conularia cambria Walcott, 1890 from the Furongian of Wisconsin. Apical angles of Baccaconularia range from approximately 13° to 14.5°. Scanning electron imaging of B. cf. robinsoni shows that its thin, phosphatic skeleton is finely lamellar, with the thickness of individual lamellae measuring approximately 1 μm. The skeleton also exhibits microscopic circular pores and crater-like pits that range from approximately 5 to 10 μm in diameter. These pores and pits are similar in size, geometry, areal density and pattern of arrangement to those of many post-Cambrian conulariids. Microscopic circular pores are documented here for the first time in the genus Archaeoconularia Bouček, 1939 from the Upper Ordovician of the Czech Republic. Although the origin of the pores and pits is open to alternative interpretations, the discovery of these features and fine lamination in Baccaconularia strengthens the argument that this genus is a Cambrian conulariid.     

A Middle Cambrian edrioasteroid from the Murero biota (NE Spain) with Australian affinities

A Middle Cambrian edrioasteroid belonging to the genus Cambraster is described from the Middle Cambrian Murero biota (Cadenas Ibéricas, NE Spain). Up to now, this genus was known only from Australia and France. This represents the first record of the class Edrioasteroidea in the Cambrian of Spain. Moreover, preliminary results on the diversity and biostratigraphic position of Cincta, Eocrinoidea and Edrioasteroidea from this area are reported.     

A Tremadocian (Early Ordovician) palaeoscolecidan worm from graptolitic shales in Hunan Province,South China

A new locality exposing Tremadocian (Early Ordovician) graptolitic shales in Hunan Province, South China, has yielded an exceptionally well‐preserved annulated worm. This palaeoscolecidan is described as Waflascolex changdensis gen. et sp. nov. and reveals extremely fine detail of the cuticle organization and plating array. The new taxon is characterized by three critical characters: incomplete plate rows that occur only on the posterior end of the worm (except in the posterior‐most area) and do not extend over the entire circumference or along the entire trunk; a regular rhomboidal array of platelets around intercalations; and reduced cuticular organization at the posterior termination. The unique cuticular organization and platelet ornamentation in the new taxon offer insight into functional differentiation of plates in the scleritome. Palaeoscolecid distribution through the early Palaeozoic is reviewed, showing that the worms were widespread in the Cambrian and Ordovician, but became more restricted during the Silurian. Ordovician palaeoscolecidans are diverse in scleritome architecture, and strikingly different from Cambrian taxa, indicating that this group diversified as part of the Great Ordovician Biodiversification Event.     

The Early Cambrian acritarch Skiagia and its significance for global correlation

Global records of Early Cambrian acritarchs from the Skiagia plexus reveal that they are stratigraphically significant and can be used as biostratigraphic markers. Skiagia ornata and Skiagia ciliosa have a cosmopolitan distribution and the levels of their first appearance datums are proposed to serve as biostratigraphic horizons for interregional correlation. These levels are close to the lower boundary of the undefined Cambrian Stage 3, and within the Stage 3, respectively. The acritarch assemblage diagnostic of the Heliosphaeridium dissimilare-S. ciliosa Zone of Baltica is recorded worldwide and some species are traced on four of the Cambrian continents that include South Australia, South China and Laurentia. This supports the intercontinental correlation of certain Lower Cambrian strata and establishes the time equivalence between the regional trilobite zones to which these strata are attributed. The regional zonation is briefly reviewed for the purpose of comparing and evaluating the acritarch ranges. The biostratigraphic correlation of the Lower Cambrian strata, belonging to different faunal provinces, is based for the first time on the same fossil species, which have a cosmopolitan distribution and well-defined first appearance datums, and on the entire diagnostic acritarch assemblages.     

A new rhynchosaur maxillary tooth plate morphotype expands the disparity of the group in the Ischigualasto Formation (Late Triassic) of Northwestern Argentina

Abstract

Rhynchosaurs are a clade of quadruped, herbivorous stem-archosaur diapsids restricted to the Triassic Period. The group became globally distributed and the numerically dominant tetrapods of several terrestrial ecosystems before their extinction. Derived rhynchosaurs are characterized by a specialized masticatory apparatus, composed of a blade-and-groove occlusion with multiple longitudinal maxillary tooth rows. The morphology of the maxillary tooth plate has shown to be taxonomically and phylogenetically informative. So far, two rhynchosaur maxillary tooth plate morphotypes are known in Argentina, one belonging to an unnamed stenaulorhynchine from the Chañares Formation and the other to the hyperodapedontine Hyperodapedon sanjuanensis, the single rhynchosaur species currently name for the Ischigualasto Formation. Here we describe a new rhynchosaur maxillary tooth plate morphotype based on an indeterminate hyperodapedontine specimen from the Ischigualasto Formation. This maxillary tooth plate (PVL 2728) possesses a single longitudinal groove that divides symmetric lateral and medial tooth-bearing areas with relatively large tooth crowns, which is an uncommon combination of features among hyperodapedontines. These qualitative observations in addition to quantitative analyses show that the morphology of PVL 2728 differs from that of, at least, other sampled South American rhynchosaurs. Therefore, this specimen expands the morphological disparity of rhynchosaurs in northwest Argentina and southwestern Pangaea.     

Arthrophycus as a mimic of crinoid column impressions in the lower Silurian of central Kentucky,USA

Unusual specimens of an ichnofossil, herein ascribed to Arthrophycus, are described from siltstone tempestites in the lower Silurian (Llandovery, Telychian) Estill Shale near Irvine, Estill County, central Kentucky, USA. The specimens display closely spaced, uncurved transverse annulations, but lack the medial ridge, rectangular cross‐sectional shape and dense branching typical of common Silurian Arthrophycus ichnospecies. This combination of features, coupled with the straightness of burrows and alignment parallel to inorganic tool marks, closely approximates the appearance of moulds of partially articulated crinoid columns (= pluricolumnals) that were impressed into firm mud and cast by storm‐deposited sediment. That these structures do not represent the external moulds of body fossils is suggested by minor width variations along the long axis of specimens, possible bioglyphs and the total absence of skeletal material, including isolated crinoid columnals, in this and other tempestites from this interval. More convincingly, the presence of very sparse branching indicates a trace fossil origin for these structures. These fossils are best interpreted as the products of preferential mining of inorganically generated tool marks by deposit feeders, owing to exposure of more organic‐rich muds by erosional scouring. Thus, this occurrence represents a rare instance in which trace fossils display a strong alignment parallel to inorganic sedimentary structures.