A New Late Silurian or Early Devonian Thelodont from the Boothia Peninsula, Arctic Canada

Isolated scales of Boothialepis thorsteinssoni gen. et sp. nov. are described from a fossiliferous calcareous dolomite at the base of the Somerset Island Formation of the Boothia Peninsula, Arctic Canada. A new family, Boothialepididae (Thelodonti), is established on features of the scale morphology and histology. The new genus and species are distinguished by characteristics of crown sculpture, neck, and unusual size of the base. Two other thelodonts, Nikolivia elongata Karatajūtė-Talimaa and Canonia grossi Vieth, and an acanthodian, Poracanthodes sp., are described from the same stratigraphical level. Thelodonts have not previously been described from the Boothia Peninsula. Conodont-based correlation indicates a Late Silurian age for the base of the Somerset Island Formation on the Boothia Peninsula. Correlation of the beds with precisely dated microvertebrates in the Read Bay section on Cornwallis Island enables the age of the horizon with the new species to be determined as Early Devonian.     

An operculum of the Silurian nautiloid Aptychopsis from Arctic Canada

Three articulated valves of the genus Aptychopsis are interpreted as the operculum of a nautiloid. The valves are joined by an organic film which covers the entire dorsal valve. This genus has not been previously reported from North America.     

Upper Ordovician and Lower Silurian chitinozoans from central Nevada and Arctic Canada

Late Ordovician and Early Silurian chitinozoans from the uppermost Vinini Formation, and the Hanson Creek Formation in central Nevada and the lower Cape Phillips Formation, Cape Manning section, in Arctic Canada have been re-investigated and a new chitinozoan biozonation is proposed. The Upper Ordovician of central Nevada can easily be correlated to that of Arctic Canada through the common occurrence of the Ordochitina nevadensis biozone in both regions. No such correlation, however, is possible with the Late Ordovician of Anticosti Island in eastern Canada because of the absence of the index Upper Ordovician chitinozoan zonal species of central Nevada such as Belonechitina tenuispinata sp. nov, Ordochitina nevadensis sp. nov. and Nevadachitina vininica gen. nov., sp. nov. in the former area.One new genus, Nevadachitina, and nine new species, Eisenackitina ripae, Belonechitina martinica, Nevadachitina vininica, Nevadachitina praevininica, Ordochitina nevadensis, Belonechitina tenuispinata, Belonechitina parvispinata, Tanuchitina laurentiana, Angochitina hansonica are described and illustrated in this paper and four species are left in open nomenclature.     

Peridermal and interthecal tissue in Silurian retiolitid graptolites: with examples from Sweden and Arctic Canada

Peridermal tissue, and thecal 'floors' are shown to be present in some specimens of Pseudoretiolites, Retiolites and Stomatograptus. The development of a dense reticulum and thecal hoods is also recognized as being a progressive developmental feature in Gothograptus. It is suggested that all these structures, whether internal or external, are the product of mature or old-age development. It appears questionable whether the Rhabdopleura model of rhabdosomal development adequately explains late-stage membranes and other adventitious tissues such as discussed herein.     

Late Silurian trilete spores from northern Jiangsu, China

The Late Silurian is generally considered to a particular significant key period in the study of early land vascular plants. A trilete spore assemblage of the Upper Silurian is described from northern Jiangsu, China. This assemblage comprises 11 genera and 20 species of trilete spores (including laevigate, apiculate, perinotrilite, patinate, rarely distally murornate and equatorially crassitate, and three indeterminate trilete miospores forms). It has similarities to those described from coeval assemblages from around the world (e.g., England and South Wales; Tripolitania, Libya; Cornwallis Island, Canadian Arctic; Northwest Spain). The rare cryptospore, only one specimen (Tetrahedraletes sp.) had been found to be associated with the Chinese trilete spore assemblage. The discovery of the trilete spores from Late Silurian rocks indicates the existence of early land plants, some possibly vascular, at that time in northern Jiangsu, China.     

Bryozoan palaeoecology in the Late Silurian of Gotland

The present paper deals with the ecology of the Bryozoa in the Upper Wenlockian of Gotland. The Upper Wenlockian sedimentary rocks of Gotland, locally known as the Halla-Mulde Beds, are deposited in a shallow sea. The sedimentary rock types include well-developed reefs of “barrier” and “fringing” types and marly limestones in both forereef and backreef positions. These sedimentary rocks are rich in Bryozoa as well as in other shelly fossils. Twenty seven bryozoan species have been identified from this stratigraphic sequence. The bryozoans tend to occur in associations. These are not strictly comparable with the neontological animal communities in the Petersen sense, but should rather be regarded as “ecozones”.Twelve different faunistic associations can be identified in the investigated material. On Bryozoa alone, five major zones are discernible.     

Late Silurian brachiopods from Darhan Mumingan Joint Banner, Inner Mongolia

Seven brachiopod species (including three new species) and three undetermined forms are described and figured here from an unnamed stratigraphic unit which mainly consists of argillaceous and bioclastic limestone near the stratotype of the Late Silurian Xibiehe Formation of the Xibiehe section in the Darhan Mumingan Joint Banner, north of the Bateaobao area, Inner Mongolia. Three new species, Eoschizophoria minuta, Navispira navicula and Howellella asiatica are established with transverse serial sections for their interiors. All brachiopod taxa described here show that this unnamed stratigraphic unit is higher than the Late Silurian Xibiehe Formation in the Xibiehe section and is possibly transitional between the Late Silurian and the Early Devonian. Authors temporarily regard this unit as the upper part of the Xibiehe Formation in this paper.     

Late Silurian trilobites from the Nuratau and Turkestan ranges, Uzbekistan and Tajikistan

Silurian trilobites of Ludlow and P?ídolí age are described from sections in southern Uzbekistan and from adjacent parts of Tajikistan. They belong to 22 species (10 named and 12 under open nomenclature) distributed among 13 genera belonging to the families Proetidae, Tropidocoryphidae, Aulacopleuridae, Scharyiidae, Cheiruridae, Encrinuridae and Odontopleuridae. The following new species are described: Interproetus pentaxus, Paleodechenella turkestanica, P. zaaminicus, Cromus tamchii and Leonaspis nuratensis. The generic associations from the mid Ludlow bear a striking resemblance to coeval ones from Bohemia, and include genera otherwise known only from that region or from adjacent parts of central Europe. The trilobite faunas from the late Ludlow and P?ídolí series are much less diverse and are dominated by genera of the Warburgellinae (Tropidocoryphidae), which include one species common to Vaigatch Island in the Russian Arctic, and Podolia, Ukraine. The closest links of the diverse central Asian mid Ludlow faunas are therefore to central Europe, whilst the sparser younger Ludlow and P?ídolí faunas, such as they are, suggest closer links to Baltica.     

Biogeographical analysis of Late Silurian brachiopod faunas, chiefly from Asia and Australia

Shallow water benthic marine invertebrates (such as brachiopods from Benthic Assemblages [BA] 1–3) have usually played a much more important role than deeper ones (BA 4–5 or even deeper) in evaluating biogeographical provincialism in geological history. The Silurian brachiopod Retziella Fauna, characterized by the common presence of Retziella in association with various provincial taxa and many common North Silurian Realm genera, is known from southwest Tienshan, North China, South China, North Vietnam, and East Australia. It is possibly also present in North Korea, the central Pamirs, Afghanistan, and New Zealand. The coeval Tuvaella Fauna occurs only in the southern marginal belt of the Siberian Plate. Synecologically, both faunas inhabited a normal, shallow-water, level-bottom environment, usually with a low-diversity community (commonly 3–8 genera); assignment to BA 2–3 is indicated. Their mutual exclusiveness is of biogeographical significance: subdivisions of the Uralian-Cordilleran Region can be based on them, with the Tuvaella Fauna being included in a redefined Mongolo-Okhotsk Province. A Sino-Australian Province is established and defined herein for the area occupied by the Retziella Fauna during the Ludlow-Pridoli and probably the Wenlock. Two subdivisions of the province can be recognized, a Sino-Central-Asian Subprovince and an Australian Subprovince, based on different endemic brachiopods and separate geographical positions. The presence of a number of more cosmopolitan genera in both the tropical-subtropical Sino-Australian and subtropical-temperate Mongolo-Okhotsk Provinces during the Late Silurian testifies to oceanic surface current circulation patterns adequate for the distribution of planktic larvae capable of long-distance dispersal while maintaining reproductive communication. This contrasts with the dispersal potential of endemic components of the newly defined Silurian biogeographical units. □ Late Silurian, Brachiopoda, Retziella , Fauna, Tuvaella Fauna, Synecology, Biogeography, Asia, Australia     

Fungal endorhizal associates of Equisetum species from Western and Arctic Canada

We describe endorhizal fungi associated with Equisetum species collected from Ellesmere Island (82°N), Axel Heiberg Island (80°N), and from sites in Yukon Territory and the Prairie Provinces (51–67°N). Fungal colonization was assessed using a multiple quantitation microintersect method for lactofuchsin-stained roots examined with wide-field and confocal epifluorescence microscopy. Equisetum roots host abundant and diverse endorhizal fungal associates. For 85 specimens from 14 sites, total colonization averaged 30 ± 3%, range 0–97%. Colonization rates for wide aseptate hyphae characteristic of arbuscular mycorrhizae (5 ± 1%) was significantly less than for fine endophytes (20 ± 3%) or septate endophytes (17 ± 2%). Equisetum spp. are abundant in tundra and an important understory plant in boreal forests, where they are particularly common on burned or disturbed sites. Endorhizal fungi associated with Equisetum may have broad ecological relevance.     

Late Ordovician-Early Silurian fluctuations in sea level from eastern Anticosti Island, Quebec

Over 1,000 m of Upper Ordovician to Lower Silurian mixed carbonate and clastic strata on Anticosti Island are nearly tectonically undisturbed, despite their proximity to the Northern Appalachians fronting Quebec's Gulf of St. Lawrence. Natural cliffs exposed along the coast and rivers in the eastern part of the island make a relatively conformable sequence belonging to the Ashgill and Llandovery Series. Fossil communities interpreted as depth-associated in life are especially repetitious in the Becscie, Gun River, Jupiter, and Chicotte Formations (Llandovery Series), and to a lesser degree in the Upper Vaureal and Ellis Bay Formations (Ashgill Series). Preliminary study of the pattern of changeovers in Eocoelia, Pentamerus and Stricklandia communities suggests that Anticosti seas deepened and shallowed three and a half times during the Early Silurian. High water peaks were reached during B₁-B₂, C₁-C₂ and C₄-C₅ times, with a final deepening trend beginning in late C₅ time. Age determinations of these events are based on the occurrence of graptolites (with some new records from Anticosti) keyed to the standard graptolite zones, and species of the Eocoelia lineage are also useful for correlation. The profile of the Anticosti sea-level curve compares well with other curves reconstructed from the Lower Silurian of New York, Michigan, and Iowa. Widespread synchronism in sea-level changes on the North American platform is thus corroborated.     

Extracellular enzymes of cold-adapted bacteria from Arctic sea ice,Canada Basin

A total of 338 aerobic heterotrophic bacterial strains were isolated from Arctic sea ice, Canada Basin (77°30′N–80°12′N). The capability of the isolates to produce protease, lipase, amylase, chitinase, β-galactosidase, cellulase and/or agarase was investigated. Isolates that were able to degrade tributyrin, skim milk, starch, lactose and chitin accounted for 71.6, 65.7, 38.5, 31.6 and 16.9% of sea ice strains, respectively. Lipase producers and/or protease producers were phylogenetically widespread among the isolated strains. Starch and/or lactose hydrolytic strains were mainly distributed among Colwellia, Marinomonas, Pseudoalteromonas, Pseudomonas and Shewanella isolates. Pseudoalteromonas tetraodonis, Pseudoalteromonas elyakovii, Bacillus firmus and Janibacter melonis isolates all have the ability to degrade chitin. Only some strains belonging to Pseudoalteromonas genus scored positive for agarase (6) and cellulose (9). The temperature dependences for lipase activities were determined for five psychrophilic and six psychrotolerant bacteria. At low temperatures, the psychrophilic bacterial lipase activity was not significantly higher than psychrotolerant bacterial lipase, though all lipases showed remarkably high activity with 10–36% residual activity at 0°C.     

Crinoid holdfasts from the Silurian of Gotland

Crinoid holdfasts occur throughout the Silurian sequence of Gotland, with a marked concentration to reefs and immediate reef surroundings. Four morphological groups are recognized: (1) Discoid holdfasts. (2) Cirriferous holdfasts, represented by (a) Rhizocrinus -like holdfasts, (b) large radices with stout, often branching cirri, and (c) rhizoid holdfasts, formed by a complicated net of pseudocirri. (3) Creeping stems attached to the substrate by thin strands of stereome. (4) Coiling stems. Discoid attachments, cirriferous holdfasts (types b and c) and coiling stems show little preference to substrate and adapt morphologically to conditions at hand. Rhizoid holdfasts display the greatest variation and apparently occur within many different groups of crinoids. Rhizocrinusttke holdfasts have been found only in quiet-water deposits, while creeping stems were concentrated to more turbulent environments. Coiling stems were epizoic, attached to rugose corals, bryozoans, crinoid stems and similar supports. Growth, mode of life (attached or free), settling and fixation of larvae, and relation to substrate and other organisms ate discussed.     

Representation of aquatic vegetation change by plant macrofossils in a small and shallow freshwater lake

We explored spatial and temporal relationships between contemporary aquatic vegetation and surface sediment macrofossil remains in a small, shallow, English lake (Green Plantation Pond). The aquatic vegetation of Green Plantation Pond underwent a marked compositional change after 2005 with a shift from Elodea spp.-Potamogeton pusillus-Chara spp. to Ceratophyllum spp.-Chara spp.-Potamogeton crispus dominance. By comparing macrophyte and plant macrofossil distributions at multiple, closely spaced points in Green Plantation Pond for 2000 and 2008–2009, we studied the ability of macrofossils to track this major aquatic vegetation change. Representation of macrophytes by macrofossils was high with 63 and 76 % of extant plant species recorded by macro-remains in the 2000 and 2009 sediment surveys respectively. Nevertheless, plants were both over-represented (Nitella flexilis, Chara spp. and Zannichellia palustris) and under-represented (Ranunculus sect. Batrachium, Potamogeton spp.) in the sediment record in terms of relative macrofossil abundances and the number of occupied sample points. The study also revealed a lack of preservation of Elodea spp. leaf remains in the second (2009) survey compared to the first (2000) probably due to a longer time interval (5 vs. 10 months) between macrophyte and sediment sampling. Nevertheless, the macrofossils reliably recorded both the main shift in the contemporary vegetation (e.g. especially increases in Ceratophyllum spp. and P. crispus abundance) and other more subtle floristic changes (e.g. increases in Myriophyllum spicatum and Lemna spp.) exceptionally well. This study highlights the huge potential of macrofossils for tracking sub-decadal changes in the aquatic vegetation of small, shallow lakes.     

Ecology of a Late Silurian fauna of graptolites and associated organisms

The Ludlow Series of Wales and the Welsh Borderland represents an ocean-bordering basin and shelf which received a shoaling sequence of sediments in the late Silurian. Graptolites grade from highest diversity and density in basin areas to lowest diversity and density on the nearshore shelf. By analogy with modern zooplankton, this distribution is attributed to differentiation of surface water masses over basin and shelf. During Ludlow time, the center of graptolite abundance shifted northward, indicating a restriction and seaward movement of the basin water mass. Small nektic cephalopods and phyllocarids parallel distribution trends of the graptolites, as does a fauna of small bivalves and brachiopods which may have lived on floating plants. The water mass model accounts for most distributional patterns of pelagic organisms in this local area, and has broader application to the distribution and evolution of graptolites.     

Arctic plant diversity in the Early Eocene greenhouse

For the majority of the Early Caenozoic, a remarkable expanse of humid, mesothermal to temperate forests spread across Northern Polar regions that now contain specialized plant and animal communities adapted to life in extreme environments. Little is known on the taxonomic diversity of Arctic floras during greenhouse periods of the Caenozoic. We show for the first time that plant richness in the globally warm Early Eocene (approx. 55-52 Myr) in the Canadian High Arctic (76° N) is comparable with that approximately 3500 km further south at mid-latitudes in the US western interior (44-47° N). Arctic Eocene pollen floras are most comparable in richness with today's forests in the southeastern United States, some 5000 km further south of the Arctic. Nearly half of the Eocene, Arctic plant taxa are endemic and the richness of pollen floras implies significant patchiness to the vegetation type and clear regional richness of angiosperms. The reduced latitudinal diversity gradient in Early Eocene North American plant species demonstrates that extreme photoperiod in the Arctic did not limit taxonomic diversity of plants.     

A soft-bodied lophophorate from the Silurian of England

Soft-bodied taxa comprise an important component of the extant lophophorate fauna, but convincing fossils of soft-bodied lophophorates are extremely rare. A small fossil lophophorate, attached to a brachiopod dorsal valve, is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of England. This unmineralized organism was bilaterally symmetrical and comprised a subconical body attached basally to the host and partially enclosed by a broad ‘hood’; the body bore a small, coiled lophophore. Where the hood attached laterally, there is a series of transverse ridges and furrows. The affinities of this organism probably lie with Brachiopoda; the hood is interpreted as the homologue of a dorsal valve/mantle lobe, and the attachment as the homologue of the ventral valve and/or pedicle. The ridges are arranged in a manner that suggests constructional serial repetition, indicating that they are unlikely to represent mantle canals. Extant brachiopods are not serially structured, but morphological and molecular evidence suggests that their ancestors were. The new organism may belong to the brachiopod stem group, and might also represent a significant element of the Palaeozoic lophophorate fauna.