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1.
A single stem section (pluricolumnal) belonging to a post-Palaeozoic crinoid (sea lily) is reported from a small outcrop of Lower Jurassic Lias Group strata exposed in low cliff near Dunrobin Castle. This is the first Jurassic crinoid recorded from Eastern Scotland and the small fragment has enough diagnostic characters to be assigned to the species Isocrinus cf. robustus; a crinoid found commonly in the Lower Jurassic of England. The Scottish form collected has unusual morphology that is atypical of the genus.  相似文献   

2.
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   

3.
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   

4.
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   

5.
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   

6.
Calyx plates of the crinoid Uintacrinus anglicus are recorded from the top and bottom of a 5 m interval, 4 m above the disappearance of calyx plates of the crinoid Marsupites testudinarius within the Flamborough Chalk Formation at Danes Dyke in North Yorkshire, UK. The U. anglicus Zone, as used here, comprises the interval from the disappearance of M. testudinarius to the disappearance of U. anglicus calyx plates, and therefore includes, but does not comprise, the total range of the index species. Two subzones are recognized in the M. testudinarius Zone; a lower subzone characterized by smooth Marsupites calyx plates and an upper subzone characterized by variably ornamented Marsupites calyx plates. A provisional study of the belemnite indicates the Gonioteuthis granulataquadrata appears in the highest part of the M. testudinarius Zone. The 1983 Copenhagen symposium on Cretaceous stage boundaries proposed that the base of the Campanian Stage should be drawn at a level close to the appearance of G. granulataquadrata. Consequently, the extinction of M. testudinarius is used to define the base of the Campanian here and U. anglicus Zone is placed in the basal Lower Campanian.  相似文献   

7.
An unusual crinoid pluricolumnal from the Lower Carboniferous of Salthill Quarry, Clitheroe, Lancashire, has a tetrastellate lumen. This may be derived from either a cupressocrinitid or a gasterocomid, two families of cladid inadunate which have previously only been reported from the Devonian. Large inadunate cups are relatively rare at Salthill but columnals are varied and numerous, so it is not surprising that the first indications of such a crinoid at this locality should be given by dissociated ossicles. However, it is also possible that this columnal represents an aberrant individual of a species with an axial canal that is usually pentastellate.  相似文献   

8.
Ammonites of the family Lytoceratidae from the Middle Jurassic Inferior Oolite Formation, Aalenian to lowermost Bathonian, of Dorset are rarely described, perhaps because the macroconchs are often very large and difficult to collect intact and the microconchs are very small and easily overlooked. Detailed stratigraphical collecting over several years has shown them to be a minor part of the ammonite fauna but more common at certain horizons. Four genera, Lytoceras, Megalytoceras Nannolytoceras and Pleurolytoceras have been shown to have different stratigraphical ranges and abundances in the Aalenian and Bajocian but they have not been found in the Lower Bathonian of Dorset. The taxonomic basis of several of the well-known species is poorly described in the literature and is remedied here.  相似文献   

9.
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   

10.
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   

11.
Pelmatozoans diversified primarily during the Middle and Late Ordovician Period, with Early Ordovician records being much more limited, resulting in many gaps in our knowledge of the early stages of their diversification. Dissociated pelmatozoan ossicles have been found abundantly in one section in the Tonggao Formation (Tetragraptus approximatus Biozone, Floian, Early Ordovician). Most of the ossicles are thecal plates and stem ossicles from hemicosmitoid and glyptocystitoid cystoids. Thecal plates of ‘Cheirocrinus’ sp., Polycosmites sp., and other plates of uncertain affinity are described. A different ossicle type, Pentagonopentagonalis (col.), may represent crinoid remains; this would be one of the earliest occurrences of the class. The thecal ossicles and columnals are all considered, as both sets of data are desirable to determine the most complete estimate of generic diversity. The echinoderm ossicles may have been transported in from shallower water palaeoenvironments and clusters of ossicles may represent coprolites or regurgitates. Estimates of Early Ordovician palaeogeography that place this site at 30°S or near the palaeoequator are supported by the physiological requirements of the primitive echinoderms described herein. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

12.
The most extensive ichnofauna yet recorded from a deep water Lower Palaeozoic sequence occurs within the distal turbidites of the Lower Silurian Aberystwyth Grits Formation of Central Wales. The strata contain an abundant assemblage comprising 25 ichnogenera: Asteriacites, Bergaueria, Chondrites, Cochlichnus, Cosmorhaphe, Glockerichnus, Gordia, Helicolithus, Helminthopsis, Helminthoida, Hormosiroidea, Lorenzinia, Megagrapton, Monomorphichnus, Neonereites, Nereites, Palaeophycus, Paleodictyon, Planolites, Protopaleodictyon, Spirorhaphe, Spirophycus, Squamodictyon, Subphyllochorda, Taphrhelminthopsis; 36 ichnospecies are described, three of which (Asteriacites aberensis, Helminthopsis regularis, Cosmorhaphe elongata) are new. The inorganic sedimentary structures and trace fossils of some 418 sandstone beds were examined in detail; 16 per cent of the beds commence with Divisions A or B and 84 per cent with Division C of the turbidite sequence. This indicates a relatively distal environment, mainly receiving low velocity turbidity currents, and favouring trace fossil preservation. The most common traces were Helminthopsis, Paleodictyon, and Squamodictyon which were found on 46 per cent, 34 per cent, and 19 per cent of the beds examined. Data from this, and other recently described sequences, confirms that there was a gradual increase in trace fossil diversity in the deep oceans throughout the Lower Palaeozoic, in contrast to the situation in shallow water shelf seas where a peak was reached as early as the Lower Cambrian.  相似文献   

13.
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   

14.
Liaostenophlebia yixianensis gen. et sp. nov., a new stenophlebiid damsel-dragonfly, is described from the Lower Cretaceous Yixian Formation of western Liaoning, northern China. It is the third Chinese damsel-dragonfly belonging to the family Stenophlebiidae to be described. Liaostenophlebia gen. nov. differs from the other genera of Stenophlebiidae in having Ax2 shifted just above MAb, a transverse and narrow Hal, a more curved anterior side of the hypertriangle, and a broader cubital-anal area. Sinostenophlebia zhanjiakouensis Hong, 1984 was previously attributed to Stenophlebiidae and hardly compares with other genera within this family. A check of the plates of the type species (Sinostenophlebia zhanjiakouensis Hong, 1984) suggests that Sinostenophlebia Hong, 1984 should be a member of the family Aeschnidiidae and it is very likely that this genus is a junior synonym of Leptaeschnidium Pritykina, 1977. The new data increases the diversity of both Stenophlebiidae and Aeschnidiidae in the Lower Cretaceous of China.  相似文献   

15.
A collection of numerous crinoid pluricolumnals from the uppermost Darriwilian (Middle Ordovician) of Tibet were derived from one biological species of crinoid. The specimens were collected from well‐lithified, bioclastic shelf limestones of the upper part of the Lower Chiatsun Group, Pygodus serra Biozone; coeval rocks of similar lithology outcrop at the summit of Everest. A new crinoid morphospecies, Segmentocolumnus (col.) hanshessi, is tentatively considered a ‘stem‐group cladid’, perhaps a dendrocrinid. The proxistele is broad and pentagonal in section with a broad, pentagonal axial canal; the mesistele of similar gross morphology is more slender with a regularly heteromorphic column and a similarly wide axial canal; the dististele is a terminal dendritic radice with a pentastellate axial canal. In the mesistele, the meric sutures correspond to the centres of the sides of the column, but in the dististele they occur in the angles. This range of morphologies would have led to their inclusion in at least two morphogenera if they had not been closely associated; as they belong to a single biological species, they have been ‘lumped’ together herein. This is a rare contribution to our knowledge of the early crinoids from a region outside Europe and North America. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

16.
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   

17.
The fossil echinoderms of the Lower Carboniferous (Mississippian) of Derbyshire remain understudied, principally due to the nature of the preservation rather than any lack of biodiversity. Echinoids and crinoids are described in float blocks of limestone from near Hurdlow, Derbyshire, which have been etched naturally after many years of being washed by weakly acidic rain. Surface detail is variable, commonly poor, but rare specimens retain enough features for tentative identification. Two species of echinoids are identified from rare disarticulated plates, namely Melonechinus? sp. (ambulacral plates) and archaeocidarid sp. (interambulacral plate); more and superior material will be necessary to confirm this division. Crinoids include a cladid brachial ossicle sp. with a distinctive sculpture; a columnal of a monobathrid camerate platycrinitid sp.; Annulocolumnus (col.) sp. cf. A. annulus Donovan, a columnal morphotaxon with an unusually broad axial canal; and Cyclocyclicus (col.) spp. This is the tenth echinoid site to be recognized from the Mississippian of the White Peak. Examination of etched float blocks provides a further method of investigation of the echinoderm fauna of this and other limestone areas.  相似文献   

18.
Only two crinoid faunas of Rhuddanian or early Aeronian age have been described hitherto, both from North America. A Rhuddanian pelmatozoan fauna from Haverfordwest, Dyfed, south-west Wales includes the cheirocrinid rhombiferan cystoid Homocystites? sp., plus the following crinoid species: the calceocrinid disparids Calceocrinus turnbulli sp. nov. and Calceocrinus? sp.; the dendrocrinid cladid Dendrocrinus? gasworksensis sp. nov.; the patelliocrinid monobathrid Macrostylocrinus? sp. indet.; columnals of the rhodocrinitid(?) diplobathrid Floricolumnus (col.) sp. cf. F. (col.) girvanensis Donovan and Clark; the rhodocrinitid diplobathrid Chaosocrinus ornatus sp. nov.; and two indeterminate crinoid species. At the familial level this fauna shows strong similarities with coeval, but more diverse, crinoid assemblages from North America, suggesting that endemism did not develop until later in the Silurian.  相似文献   

19.
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20.
The interpretation of newly released commercial 2D reflection seismic data in the Kattegat area, Denmark, has provided us with a better understanding of the Palaeozoic tectonic processes along the Tornquist Fault Zone. A Base Palaeozoic time structure map, a Lower Palaeozoic TWT isopach map, a “true” Lower Palaeozoic TWT isopach map, an Upper Carboniferous/Lower Permian syn-rift TWT isopach map, a Top pre-Zechstein time structure map and a Zechstein combined TWT isopach and Palaeogeography map have been generated. The uniform Lower Palaeozoic sequence thickness in the Kattegat, both inside and outside the Tornquist Zone indicates only minor lateral movements if any, whereas the extensive Upper Silurian sequence, increasing in thickness to the north, indicates a relatively fast regional subsidence. The Base Palaeozoic time structure map and the Late Palaeozoic syn-rift isopach map show a clear Late Palaeozoic extension in the area. The syn-rift isopach map, in combination with the time-equivalent opening of the Skagerrak graben at right angles to the Tornquist Zone in the Kattegat, indicates that this extensional tectonic event had a dextral slip component. Measurements on internal extensional faults in the Tornquist Zone, give a minimum right-lateral displacement of 10.4 km. The footwall blocks were deeply eroded during the Early Permian rifting, and at Zechstein times the area became a peneplane. The Tornquist Zone was later exposed to several tectonic phases, where dextral slip played a role, indicated by the “push up” and “pull down” structures caused by restraining and releasing bends of the Børglum Fault. The dextral displacement along the Børglum Fault since the beginning of the Permian is in the order of 5–7 km based on the displacement of a Lower Palaeozoic local depocentre. Early Permian depocentres and faults, which gives a total amount of right-lateral displacement since the Early Palaeozoic in the order of 15–20 km. The continuously repeated tectonic episodes along the Tornquist Zone throughout most of the Phanerozoic, show that the zone was easily reactivated, implying deep-seated basement faults. The Tornquist Zone can be seen as a “buffer zone”, between continental blocks, whenever changes in the regional stress field are induced.  相似文献   

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