scholarly journals Functional morphology, evolution and systematics of Early Palaeozoic univalved molluscs

1991 ◽  
Vol 161 ◽  
pp. 1-116
Author(s):  
J.S Peel
Keyword(s):  
Functional Morphology ◽  
Lower Cambrian ◽  
Potential Role ◽  
Morphology Evolution ◽  
Early Palaeozoic ◽  
Molluscan Evolution ◽  
North Greenland

This bulletin contains two papers describing aspects of the functional morphology and systematics of Early Palaeozoic untorted molluscs and bellerophontacean gastropods. A brief discussion of the potential role in early molluscan evolution of articulated halkieriids recently discovered from the Lower Cambrian of North Greenland forms an introduction to the volume.

scholarly journals The Precambrian, Eocambrian and early Palaeozoic stratigraphy of the Jørgen Brønlund Fjord area, Peary Land, North Greenland

1971 ◽  
Vol 96 ◽  
pp. 1-42
Author(s):  
H.F Jepsen
Keyword(s):  
Lower Cambrian ◽  
Field Work ◽  
Sedimentary Sequence ◽  
Long Period ◽  
Composite Section ◽  
Lower Palaeozoic ◽  
Early Palaeozoic ◽  
North Greenland

The sedimentary sequence in the platform area (approx. 2500 km2) around Jørgen Brønlund Fjord, North Greenland, has been mapped, and sections through the Precambrian, Eocambrian and Lower Palaeozoic sequence are described. After a summary of the previous geological field work carried out in the area, a lithological description of a composite section through the sequence below the Lower Cambrian Brønlund Fjord Dolomite (Troelsen, 1949) is given. This sequence, which is about 1000 m thick, is divided into four formations – in ascending order: Inuiteq Sø Formation (sandstone), Morænesø Formation (tillite and dolomite), Portfjeld Formation (dolomite) and Buen Formation (sandstone and shale). The first three named formations are separated by two unconformities both representing a long period of erosion. The strata are cut by two dolerite sequences, of which the older (the Midsommersø dolerites) is of Precambrian age and intrudes only the Inuiteq Sø Formation. Intrusions of the younger sequence penetrate all the strata in the Jørgen Brønlund Fjord area and are regarded as post-Palaeozoic. In the last section the chronostratigraphy and the correlation with neighbouring areas are discussed. Special attention is given to the two newly discovered erosional unconformities, which together with the tillite occurrence and the radiometric K/Ar dated Midsommersø dolerites, throw new light on the stratigraphy of North Greenland.

scholarly journals Hadimopanella from the Lower Cambrian of North Greenland: structure and affinities

1988 ◽  
Vol 37 ◽  
pp. 83-103
Author(s):  
S. E. Bendix Almgreen ◽  
John S. Peel
Keyword(s):  
Lower Cambrian ◽  
New Records ◽  
Early Cambrian ◽  
Close Relationship ◽  
New Material ◽  
Early Palaeozoic ◽  
North Greenland

New records of minute phosphatic sclerites of Hadimopanella are described from the Aftenstjernesø and Henson Gletscher Formations of western and central North Greenland in strata of Early Cambrian age. The new material illustrates the occurrence of mineralisation in the wall between individual sclerites and confirms earlier suggestions of the close relationship between Hadimopanella and Utahphospha. Both forms are compared with spicules produced by living and fossil compound ascidians of the genus Cystodytes and it is concluded that they may have been Early Palaeozoic representatives of the chordate Class Urochordata.

The problematic fossil Triplicatella from the Early Cambrian of Greenland, Canada, and Siberia

2004 ◽  
Vol 41 (11) ◽  
pp. 1273-1283 ◽  
Author(s):  
Christian B Skovsted ◽  
John S Peel ◽  
Christian J Atkins
Keyword(s):  
New Species ◽  
Functional Morphology ◽  
Lower Cambrian ◽  
Early Cambrian ◽  
Taxonomic Affinity ◽  
East Greenland ◽  
North East ◽  
Close Proximity ◽  
Two New Species

The cap-shaped Early Cambrian fossil Triplicatella, previously known only from Australia, is reported from the upper Lower Cambrian of North and North-East Greenland, western Newfoundland, and Siberia. The occurrence of Triplicatella in Laurentia strengthens faunal ties between Laurentia and the Australian margin of Gondwana in late Early Cambrian times and supports hypotheses advocating the close proximity for the two palaeocontinents. Two new species, Triplicatella sinuosa n. sp., and T. peltata n. sp. are described, morphological details of which help elucidate the functional morphology and taxonomic affinity of the group. Three opercular types attributable to Triplicatella are left in open taxonomy. The postulated affinity of Triplicatella to hyoliths is confirmed, although the genus can not be placed within either of the two orders of hyoliths currently recognized.

Articulated halkieriids from the Lower Cambrian of North Greenland and their role in early protostome evolution

1995 ◽  
Vol 347 (1321) ◽  
pp. 305-358 ◽  
Keyword(s):  
Body Size ◽  
Molecular Biology ◽  
Lower Cambrian ◽  
Burgess Shale ◽  
Internal Anatomy ◽  
Middle Cambrian ◽  
Functional Consequence ◽  
Primitive State ◽  
North Greenland

Articulated halkieriids of Halkieria evangelista sp. nov. are described from the Sirius Passet fauna in the Lower Cambrian Buen Formation of Peary Land, North Greenland. Three zones of sclerites are recognizable: obliquely inclined rows of dorsal palmates, quincuncially inserted lateral cultrates and imbricated bundles of ventro-lateral siculates. In addition there is a prominent shell at both ends, each with radial ornamentation. Both sclerites and shells were probably calcareous, but increase in body size led to insertion of additional sclerites but marginal accretion of the shells. The ventral sole was soft and, in life, presumably muscular. Recognizable features of internal anatomy include a gut trace and possible musculature, inferred from imprints on the interior of the anterior shell. Halkieriids are closely related to the Middle Cambrian Wixaxia , best known from the Burgess Shale: this clade appears to have played an important role in early protostome evolution. From an animal fairly closely related to Wixaxia arose the polychaete annelids; the bundles of siculate sclerites prefigure the neurochaetae whereas the dorsal notochaetae derive from the palmates. Wixaxia appears to have a relic shell and a similar structure in the sternaspid polychaetes may be an evolutionary remnant. The primitive state in extant polychaetes is best expressed in groups such as chrysopetalids, aphroditaceans and amphinomids. The homology between polychaete chaetae and the mantle setae of brachiopods is one line of evidence to suggest that the latter phylum arose from a juvenile halkieriid in which the posterior shell was first in juxtaposition to the anterior and rotated beneath it to provide the bivalved condition of an ancestral brachiopod. H. evangelista sp. nov. has shells which resemble those of a brachiopod; in particular the posterior one. From predecessors of the halkieriids known as siphogonuchitids it is possible that both chitons (polyplacophorans) and conchiferan molluscs arose. The hypothesis of halkieriids and their relatives having a key role in annelid—brachiopod—mollusc evolution is in accord with some earlier proposals and recent evidence from molecular biology. It casts doubt, however, on a number of favoured concepts including the primitive annelid being oligochaetoid and a burrower, the brachiopods being deuterostomes and the coelom being an archaic feature of metazoans. Rather, the annelid coelom arose as a functional consequence of the transition from a creeping halkieriid to a polychaete with stepping parapodial locomotion.

scholarly journals Lower Cambrian trace fossils from northern Greenland

1988 ◽  
Vol 137 ◽  
pp. 43-53
Author(s):  
J Bergström ◽  
J.S Peel
Keyword(s):  
Lower Cambrian ◽  
Trace Fossils ◽  
Trace Fossil ◽  
East Greenland ◽  
North West ◽  
North Greenland

Rusophyciform and cruzianaeform trace fossils are described from Lower Cambrian siliciciastic shelf deposits in North-West and North Greenland. Cruziana cf. C. dispar Linnarsson, 1869 is reported from the Dallas Bugt Formation of Inglefield Land while a new ichnospecies, Rusophycus marginatus, occurs in the Buen Formation of Peary Land and in the equivalent Humboldt Formation of Daugaard-Jensen Land. These species show no similarity to the Cruziana sp. previously described from East Greenland. The occurrence of C. cf. C. dispar could indicate some similarity in Cambrian trace fossil 'ichnofaunas' between Greenland and Europe but available material is insufficient to ciarify this relationship.

scholarly journals Trachyplax arctica, a New Multiplated Problematic Fossil from the Lower Cambrian of North Greenland

2009 ◽  
Vol 54 (3) ◽  
pp. 513-523 ◽  
Author(s):  
Cecilia M. Larsson ◽  
John S. Peel ◽  
Anette E.S. Högström
Keyword(s):  
Lower Cambrian ◽  
North Greenland

Introduction to the Welsh Basin thematic issue

1992 ◽  
Vol 129 (5) ◽  
pp. 513-514
Author(s):  
N. H. Woodcock ◽  
C. J. N. Fletcher
Keyword(s):  
Lower Cambrian ◽  
Lower Devonian ◽  
Sedimentary Rocks ◽  
Thematic Issue ◽  
Irish Sea ◽  
Basin Inversion ◽  
Northwestern Margin ◽  
Marine Facies ◽  
Caledonian Orogeny ◽  
Early Palaeozoic

The Welsh Basin was an area of enhanced Early Palaeozoic subsidence on the northwestern margin of the Eastern Avalonian microcontinent. It is bordered to the southeast by the Midland Platform and to the northwest by the smaller Irish Sea Platform (Fig. 1). The sedimentary rocks of the basin and its flanking platforms range from Lower Cambrian through Lower Devonian. The sequence is dominantly marine, with abundant volcanics in the Ordovician. A basinwide change to non-marine facies is preserved in the Lower Devonian, heralding basin inversion and the culminating Acadian (late Caledonian) Orogeny.

Phytoplankton from the Lower Cambrian Læså formation on Bornholm, Denmark: biostratigraphy and palaeoenvironmental constraints

1992 ◽  
Vol 129 (1) ◽  
pp. 17-40 ◽  
Author(s):  
Małgorzata Moczydłowska ◽  
Gonzalo Vidal
Keyword(s):  
Lower Cambrian ◽  
Radioactive Decay ◽  
Depositional Environments ◽  
Event Correlation ◽  
East European ◽  
Depositional Settings ◽  
Assemblage Zone ◽  
Early Palaeozoic ◽  
A Minor ◽  
Bodies Of Water

AbstractAcritarchs from the Lower Cambrian Læsså formation on Bornholm, Denmark, are taxonomically diverse. Their state of preservation, including thermal, mechanical and chemical alteration, is discussed. Different states of thermal maturation of acritarchs in shales and phosphorites of the Broens Odde member could be explained in terms of possible irradiation from natural radioactive decay. The microfossils form two age-diagnostic assemblages that allow recognition of the Skiagia ornata–Fimbriaglomerella membranacea and Heliosphaeridium dissimilare–Skiagia ciliosa Assemblage Zones within the Broens Odde member of the Laeså formation. Acritarch-based biostratigraphy indicates that the Lower Cambrian Balka Formation and Læså formation correspond to the Schmidliellus mickwitzi Zone and Holmia kjerulfi Assemblage Zone recognized in Baltoscandia and the East European Platform. Acritarch distribution within three different depositional settings indicates that comparable spectra of morphotypes occurred in different depositional environments. This suggests the absence of facies control. During early Cambrian times palaeoenvironmental barriers in shallow, epicontinental shelf basins constituted a minor obstacle for widespread distribution of acritarch taxa. Formerly proposed early Palaeozoic acritarch provincialism appears insufficiently documented in the fossil record and no evidence could be extracted from the Cambrian record. Following a rapid radiation at the onset of the Phanerozoic, Cambrian phytoplankton populations underwent dispersion following oxygenic and nutrient-rich bodies of water within epicontinental and presumably basinal environments. Lower Cambrian acritarch taxa were largely cosmopolitan and little affected by lithofacies associations. A continuous flow of data is contributing to the emergence of acritarch-based biostratigraphy. Its apparent consistency suggests great usefulness for interregional and detailed event correlation.

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