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1.
An overview is provided of fossil echinoderm taxa recovered from the Jurassic (Lias Group) and Triassic (Penarth Group) of Ireland. Despite limited outcrop and generally poor exposure, at least 12 species are recorded (6 crinoids, 2 echinoids, 3 ophiuroids and one asteroid), with significant new material recovered from an early Hettangian lagerstätte. The crinoid Isocrinus angulatus (Fraas, 1858), omitted from an earlier Palaeontographical Society Monograph on Lower Jurassic crinoids, is described based on articulated material.  相似文献   

2.
The monobathrid camerate crinoid Macrostylocrinus bornholmensis Laursen has an unfortunate history. It was published in a journal not commonly consulted by echinoderm workers and, worse, in time of war; written in a language not in common use for crinoid studies; and described by a stratigrapher, not an expert on pelmatozoans. These and other factors combined to ensure that M. bornholmensis has not been reassessed since it was first described almost 80?years ago, despite belonging to a genus well-known from the Lower Palaeozoic. Macrostylocrinus bornholmensis is Llandovery (Telychian) and not Wenlock as has been reported elsewhere. Diagnostic features include a column that does not bear radices close beneath the cup; a heteromorphic mesistele with five orders of regularly inserted internodals; three basal plates; smooth thecal plates with central folds following rays; and ten pinnulate free arms that are biserial distally. Macrostylocrinus bornholmensis is distinctly different in morphology from well-known, congeneric species described from the Lower Palaeozoic of northern Europe.  相似文献   

3.
New brachiopods (Dimerelloidea, Rhynchonellida) from Lower Jurassic (?lower Hettangian) hemipelagic sediments of the Swiss National Park in south-eastern Engadine are described: Sulcirostra doesseggeri sp. nov. and Carapezzia engadinensis sp. nov. Sulcirostra doesseggeri is externally similar to S. fuggeri (Frauscher 1883), a dubious species, that could not be included in a comparative study, because relevant samples no longer exist. A single specimen was tentatively assigned to Sulcirostra ?zitteli (Böse 1894) by comparison of its external morphology with S. zitteli from the type locality. The partly silicified brachiopods are associated with sponge spicules, radiolarians and crinoid ossicles. Macrofossils are rare: dictyid sponges, gastropods, bivalves, crustaceans, shark teeth and scales of an actinopterygian fish. The Lower Jurassic sediments (Alpisella beds, a basal member of the Allgäu Formation) preserving the brachiopods belong to the Ortler nappe (Upper Austroalpine nappes). The exact age of the Alpisella beds is not known, as index fossils are lacking. Their stratigraphic position above the Rhaetian Kössen Formation and below the ammonite-dated Trupchun beds suggests a very Early Jurassic, probably early Hettangian age for the new brachiopod fauna. The new species of Sulcirostra and Carapezzia are confined to a very small geographic area, a peculiarity also observed in other Early Jurassic dimerelloid brachiopods. These brachiopods presumably adapted to current-dominated submarine highs, where their shells could not accumulate, except when trapped in submarine cavities or re-deposited in submarine fans. Transport by turbidity currents is suggested for the Early Jurassic dimerelloids from the Engadine. Problems with the generic definition of Sulcirostra and the higher rank classification of Carapezzia are discussed.  相似文献   

4.
The origin of the genus Bos is a debated issue. From ∼ 0.5 Ma until historic times, the genus is well known in the Eurasian large mammal assemblages, where it is represented by Bos primigenius. This species has a highly derived cranial anatomy that shows important morphological differences from other Plio-Pleistocene Eurasian genera of the tribe Bovini such as Leptobos, Bison, Proamphibos-Hemibos, and Bubalus. The oldest clear evidence of Bos is the skull fragment ASB-198-1 from the middle Pleistocene (∼ 0.6-0.8 Ma) site of Asbole (Lower Awash Valley, Ethiopia). The first appearance of Bos in Europe is at the site of Venosa-Notarchirico, Italy (∼ 0.5-0.6 Ma). Although the origin of Bos has traditionally been connected with Leptobos and Bison, after a detailed anatomical and morphometric study we propose here a different origin, connecting the middle Pleistocene Eurasian forms of B. primigenius with the African Late Pliocene and early Pleistocene large size member of the tribe Bovini Pelorovis sensu stricto. The dispersal of the Bos lineage in Western Europe during middle Pleistocene times seems to coincide with the arrival of the Acheulean tool technology in this continent.  相似文献   

5.
Distinctive trace fossils, indicating the infestation of the monobathrid camerate crinoid Neoplatycrinus Wanner by coprophagous platyceratid gastropods, are recognised for the first time from the Permian of West Timor. Platyceratid shells from West Timor have previously been reported preserved on or about the crinoid tegmen, that is, apically; in contrast, the trace fossils described herein occur in the CD interray (=posteriorly), mainly on the radials. There are two patterns of infestation in the CD interray. Circular grooves in this position, situated below the periproct, are referred to Lacrimichnus isp. Thecal modifications include the CD interray sloping towards the base, and incomplete curved ridges developed outside the circular groove and confined to the radials. A different morphology is shown by other specimens that have a broad, flattened CD interray, curving down to and extending onto the basals; this interray also slopes towards the base. These unusual CD interray modifications are interpreted as a product of snail/crinoid associations. We speculate that the major modifications to the theca may have permitted the platyceratid shell to mimic an uninfested CD interray and thus maintain the hydrodynamic integrity of the crown. This would have been to the advantage of both gastropod and crinoid. The camerates did not survive the P/Tr extinction; their demise ended an association that had persisted over 200 million years, although the platyceratids persisted into the Mesozoic.  相似文献   

6.
Crinoidal debris is common from the basal parts of the open marine Khuff Formation in Oman; yet, little is known about the diversity and affinities of this fauna. Exallocrinus khuffensis n. gen., n. sp. is described from this unit, and is the first crinoid crown from outcrops of the Wordian, Lower Khuff Member, in the northern Huqf region of Oman. This new crinoid is among the youngest Paleozoic crinoids known, yet it has a combination of more stemward and crownward characters. Because of the uncertainties concerning the latest Paleozoic and earliest Mesozoic crinoid phylogeny, Exallocrinus n. gen. is questionably assigned to the Ampelocrinidae.  相似文献   

7.
An incomplete forefin in the collections of the National Museum of Wales, Cardiff, is herein assigned to the rare leptonectid species, Leptonectes solei, known only from the west Dorset coast. It is only the third specimen of the species and is smaller than both the holotype and referred specimen. The new specimen is from the Lower Jurassic (lower Pliensbachian, Charmouth Mudstone Formation, Tragophylloceras ibex Ammonite Zone, Acanthopleuroceras valdani Ammonite Subzone) of Seatown, Dorset, UK. It confirms that all three species of Leptonectes were present in the Pliensbachian and expands the known diversity of ichthyosaurs for that time period. We show that isolated forefins of Leptonectes can be assigned to a species with a high degree of confidence.  相似文献   

8.
Nineteenth-century references to clavate borings in woody substrates in the Lower Greensand of the Isle of Wight used a variety of names, but Teredo (a wood-boring bivalve, not a boring), Teredolithes (a junior synonym of Teredolites) and Gastrochaena (a bivalve borer of rock and shelly substrates, not a boring in wood) are all nomenclatorially incorrect. Borings in a beach clast derived from the Lower Greensand Group and recently collected from Sandown Bay, Isle of Wight, are referred to Teredolites isp. cf. T. longissimus Kelly and Bromley. This specimen confirms the presence of Teredolites in the Lower Greensand Group and demonstrates a common ichnological problem of beach clasts; borings, either fossil or modern, are incompletely preserved, making confident classification below the level of ichnogenus problematic.  相似文献   

9.
Reworked fossils may be exotic, but more typically are locally derived. Echinoderms have only rarely been identified from beach clasts; most commonly, these are Upper Cretaceous echinoids from the Chalk. A pebble collected from a beach in Estonia has yielded a moderately well preserved specimen of the crinoid stem, Baltocrinus (col.) antiquus (Eichwald). This species is typical of the Baltic region, only being known from the Middle Ordovician (Darriwilian) of Estonia, but is exotic because the local outcrop is Upper Ordovician to Silurian.  相似文献   

10.
The Bathonian crinoid fauna that occurs in red nodular limestone and argillaceous limestones from the Hidas Valley, Mecsek Mts (southern Hungary) consists of three isocrinid and six cyrtocrinid species. Isocrinids are represented by Balanocrinus inornatus (d’Orbigny), B. berchteni Hess and Pugin and Balanocrinus sp. Cyrtocrinids are represented by Phyllocrinus stellaris Zar?czny, P. birkenmajeri G?uchowski, P. malbosianus d’Orbigny, Apsidocrinus sp., Lonchocrinus sp., and the new species Psalidocrinus hidasinus sp. nov. This last species is the earliest occurrence of the genus Psalidocrinus previously known from the Early Tithonian to Valanginian. This is the first crinoid fauna described from the Middle Jurassic (Bathonian) of Hungary. The co-occurrence of isocrinids and cyrtocrinids indicates an environment subject to weak currents. The stratigraphical and geographical distribution of the identified cyrtocrinid genera and species suggests a Tethyan origin and subsequent migration to the northern Tethyan shelf.  相似文献   

11.
Radiolaria from chert in the Indarung Area belong to the Transhsuum hisuikyoense Zone, indicating an Aalenian, lower Middle Jurassic, age. Carbonate in the area has been dated as Upper Jurassic to Lower Cretaceous from the occurrence of Lovcenipora, and overlying tuff has given a radiometric K/Ar age of 105±3 (Albian, uppermost Lower Cretaceous). The chert and carbonate are probably in tectonic contact, with the chert faulted into the limestone during ENE-directed compression. This comprises one of the best dated occurrences of allochthonous material in Sumatra and confirms the accretion of oceanic material along the Sunda margin during Mid- to Late-Cretaceous times.  相似文献   

12.
Well-preserved specimens, such as complete individuals, crowns and cups, are the common focus for crinoid systematic research. Yet the majority of specimens are disarticulated ossicles which are essentially ignored. The incompleteness of the fossil record is even more so when we ignore potential sources of data. A new species of crinoid comes from a monospecific assemblage from the Pennsylvanian (Upper Carboniferous) of western Ireland. All specimens are from a float block of the Clare Shale Formation (Bashkirian stage) at Fisherstreet Bay, Doolin, County Clare, western Ireland. Heloambocolumnus (col.) harperi gen. et sp. nov. has a pentagonocyclic, heteromorphic column; the small, central lumen is in a shallow, circular claustrum; the articulation is radial symplectial; the crenulae are slightly swollen and peg-like close to the circumference; nodals have rounded, unsculptured epifacets; nodal articular facets are sunken and in which narrow internodals are situated; and circlets of tubercles on epifacet surround priminternodals. These columnals are associated with robust, uniserial brachial ossicles. This crinoid is most likely a cladid.  相似文献   

13.
In the Netherlands, Late Palaeozoic pelmatozoans – that is, stalked echinoderms – are known from building stones and cobbles in rivers, but there are no in-situ carbonate rocks from which they might be collected. Unsurprisingly, most recognisable specimens are columnals and pluricolumnals. Two small thecae, collected in the mid-1970s from silexite cobbles in the bedload of the River Maas in the Venlo-Tegelen area (province of Limburg, south-east Netherlands) are exceptional finds. One specimen, the diplobathrid camerate crinoid Rhodocrinites sp., has an unsculptured theca and some minor differences of form, yet otherwise satisfies the diagnosis of this genus. The other, the pentremitid blastoid Doryblastus? sp. is rather poorly preserved, yet is the first blastoid to be recorded from the Netherlands. Either or both of these specimens may be juveniles, particularly the blastoid. They are unlikely to be coeval, coming from separate cobbles and being of slightly different preservation. Their provenance from silexite cobbles suggest they originated from Lower Carboniferous (Tournaisian-Visean = Mississippian) carbonates in the southern Ardennes (south-central Belgium).  相似文献   

14.
Given the difficulty of separating the three Picea species—P. glauca, P. mariana, and P. rubens (white, black, and red spruce)—in the pollen record, little is known about their unique histories in eastern North America following deglaciation. Here we report the first use of a classification tree analysis (CART) to distinguish pollen grains of these species. It was successfully applied to fossil pollen from eight sites in Maine and one in Massachusetts. We focused on the late glacial/early Holocene (14,000 to 8000 cal yr B.P.) and the late Holocene (1400 cal yr B.P. to present)—the two key periods since deglaciation when Picea has been abundant in the region. The result shows a shift from a Picea forest of P. glauca and P. mariana in the late glacial to a forest of P. rubens and P. mariana in the late Holocene. The small number of P. rubens grains identified from the late glacial/early Holocene samples (<5%) suggests that that species was either absent or rare at most of the sites. The occurrence and distribution of the three species do not reveal any geographic or temporal trend during late glacial time, but the data suggest that they were distributed in local patches on the landscape. The results of this study indicate that the recent population expansion of Picea (1000 to 500 cal yr B.P.) was likely the first time since deglaciation that P. rubens was abundant in the region.  相似文献   

15.
Salthill Quarry, Clitheroe, Lancashire (Mississippian, Visean) is a Site of Special Scientific Interest (SSSI), in part based on its diverse fauna of invertebrates, particularly echinoderms. A small collection of crinoid pluricolumnals are described herein, collected from muddy horizons in the Hodder Mudstone Formation to typify the diversity and frequency of their encrusting and boring fauna. These specimens are infested by a range of episkeletozoans, namely a single occurrence of Sutherlandia parasitica (Phillips), four occurrences of Cladochonus sp. and eight of Oichnus paraboloides Bromley. Two variants of the pit (boring or embedment or both) O. paraboloides are recognised: those in which a living crinoid showed a growth reaction to pit formation; and those that did not and which were presumably dead at the time of infestation. The epizoozoan tabulate coral Cladochonus sp. is also common, including specimens intergrown between and within the columnals. Sutherlandia parasitica is relatively uncommon; the only specimen likely infested a dead pluricolumnal on the sea floor. A comparative collection of pluricolumnals infested by Cladochonus beecheri Grabau from the Mississippian Borden Group of the Midwest, USA, showed superior preservation to the Clitheroe Cladochonus sp. Cladochonus beecheri in the Borden Group infested platycrinitid crinoid stems, an association not noted from Salthill Quarry. Similar suites of borings-episkeletozoans, from two other sites – the Visean of Feltrim, Co. Dublin, Ireland, and the Permian of Timor – suggest that these were persistent associations for much of the Late Palaeozoic.  相似文献   

16.
Complete fossils must be preferred to fragments for most palaeontological studies, but disarticulated specimens are nonetheless potential sources of noteworthy data. Two crinoid pluricolumnals are recorded from the lower Palaeozoic; informed discussion shows each is a basis for palaeobiological interpretation. Both are gracile and are probably belong to disparids. Floricrinus (col.) sp. is from the Silurian of Wenlock Edge, Shropshire, either from the Much Wenlock Limestone Formation (Wenlock) or, more likely, the Lower Elton Formation (Ludlow). This is the first crinoid from the Silurian of the British Isles with a pentapetaloid arrangement of the areola, a geometry common in the Middle-Upper Ordovician and higher in the geologic column. Pluricolumnal gen. et sp. indet. is from the Lower Llanvirn of Powys. One end of the otherwise straight specimen is tightly coiled. This is likely the proxistele, the most flexible region of the column, and the coiling occurred after the crown was lost by autotomy in response to an environmental disturbance.  相似文献   

17.
The Kela-2 gas field, found in the Kuqa Depression of the Tarim Basin, northwestern China, is a large-sized dry gas field (C1 /C1-5 =0.992 0.999) and characterized by ultra-high pressure (pressure factor up to 2.0 2.2). The pyrolysis experiment was carried out under isothermal gold-tube closed system, with samples collected from the Jurassic coal, Jurassic mudstone and Triassic mudstone in the Kuqa Depression. The result of gas yield showed that the Middle and Lower Jurassic source rocks have higher gas generation potential than the Triassic source rocks. The kinetic modeling of gas generation and methane carbon isotope fractionation suggested that the Kela-2 gases belong to the products of high-over mature stages and were mainly derived from the Middle and Lower Jurassic coal-bearing strata. The Triassic source rocks made a minor contribution to the Kela-2 gases. The Kela-2 gases chiefly generated from coal-bearing source rocks with R o values from 1.3% to 2.5%, and thus primarily accumulated after 5 Ma.  相似文献   

18.
The Family Afrograptidae is a ‘conchostracan’ group with multiple radial costae reaching to the umbo on their carapaces. It comprises four described genera: Afrograpta, Camerunograpta, Congestheriella and Graptoestheriella with a total of thirteen described species which are occasionally reported from the Jurassic and the Cretaceous in Africa, Europe and South America (i.e. Afrograpta from the Upper Cretaceous of Cameroon; Camerunograpta from the Jurassic to Cretaceous of Cameroon; Congestheriella from the Jurassic to Upper Cretaceous of the Congo Basin, Brazil, Bulgaria, Venezuela and Argentina; and Graptoestheriella from the Upper Jurassic to Lower Cretaceous of Brazil). A new genus and a new species, Surreyestheria ockleyensis gen. et sp. nov., belonging to the Family Afrograptidae from the Lower Cretaceous (lower Barremian) Upper Weald Clay Formation of Ockley Village, Surrey County, southern England is described in this paper. The new genus mainly differs from the other four genera by the special reticulate ornamentation on its carapace. It indicates that the Family Afrograptidae was more diverse and more widely distributed in the late Mesozoic than previously supposed. Afrograptidae is a special branch of Estheriellina the latter originating in the late Palaeozoic and the former in the early Mesozoic. Afrograptids, as a whole had been widespread across Pangea in the Early Jurassic.  相似文献   

19.
Valanginian strata in central epicratonic Poland have recently yielded crinoids, not previously recorded from the area. The fauna comprises isocrinids (Balanocrinus subteres, B. gillieroni, “Isocrinus?” lissajouxi), millericrinids (Apiocrinites sp.) and comatulids (Comatulida indet.). For comparison, a few samples of isocrinids from Valanginian strata of Hungary (Tethyan province) were also analysed. The isocrinids, cyrtocrinids and roveacrinids (sensu Rasmussen 1978 inclusive of Saccocoma sp.) were already known from the Valanginian of the southernmost Tethyan regions of Poland (Pieniny Klippen Belt and Tatra Mountains). The current study demonstrates their occurrence in central epicratonic Poland, and suggests that many Jurassic to Cretaceous stalked crinoid taxa (mainly isocrinids) predominated in the shallow-water settings of this area. Thus, the hypothesis of migration (at least from mid-Cretaceous onwards) to deep-water areas, as a response to an increase of the number of predators during the Mesozoic marine revolution, seems not to be universally applicable.  相似文献   

20.
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