scholarly journals Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides—New data from the middle Cambrian Burgess Shale Formation

2021 ◽  
Vol 66 ◽  
Author(s):  
Paul Johnston ◽  
Michael Streng
Keyword(s):  
Burgess Shale ◽  
Middle Cambrian ◽  
Shale Formation

A new study of Marrella splendens (Arthropoda, Marrellomorpha) from the Middle Cambrian Burgess Shale, British Columbia, Canada

2006 ◽  
Vol 43 (6) ◽  
pp. 721-742 ◽  
Author(s):  
Diego C García-Bellido ◽  
Desmond H Collins
Keyword(s):  
Alimentary Canal ◽  
Three Dimensional ◽  
Circulatory System ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Body Segments ◽  
Royal Ontario Museum ◽  
New Information ◽  
Shale Formation ◽  
Pair Of Antennae

Study of over 1000 specimens of Marrella splendens Walcott, 1912, out of the more than 9000 collected by the Royal Ontario Museum (ROM) since 1975, has produced new information on the anatomy, functional morphology, and behaviour of this most common arthropod in the Burgess Shale fauna. Among the new features recognized is the distinction between the alimentary canal and circulatory system; where the former is generally three-dimensional and slightly reflective, the latter never presents any relief and is very reflective. A larger range of size is now known, from 2.4 to 24.5 mm in length, with small individuals possessing 17 body segments to large specimens with more than 26 body segments, representing an almost complete ontogenetic series. The second pair of "antennae" is now interpreted as swimming appendages, since the five distal segments are dorsoventrally compressed, fringed with setae and with a considerable blood supply, providing a paddlelike appendage capable of producing a considerable propelling force. The ROM collections extend the geographical distribution of Marrella 13 km to the southeast and the stratigraphical range through the lowest five members of the Burgess Shale Formation.

The Middle Cambrian Burgess Shale and its relationship to the Stephen Formation in the southern Canadian Rocky Mountains

1998 ◽  
Vol 35 (4) ◽  
pp. 413-436 ◽  
Author(s):  
Terence P Fletcher ◽  
Desmond H Collins
Keyword(s):  
Rocky Mountains ◽  
Main Part ◽  
Canadian Rocky Mountains ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Royal Ontario Museum ◽  
Shale Formation ◽  
Geologic Setting ◽  
Continuous Deposition ◽  
Zonal Boundary

The Burgess Shale has been an anomalous geologic unit ever since Walcott named it in 1911 as the geographic equivalent of the Ogygopsis Shale in the Middle Cambrian Stephen Formation of southeastern British Columbia, but it has never been recognized outside of its type locality, so its status relative to the Stephen Formation remained uncertain. The geologic setting of the Burgess Shale was determined by Aitken and Fritz in 1968, when they recognized the Cathedral Escarpment and divided the Stephen Formation into a "thin" platformal succession on top of the Escarpment, and a "thick" basinal succession, which included Walcott's Burgess Shale, in front. Fieldwork by Royal Ontario Museum parties between 1982 and 1997 has now demonstrated that the thin and thick Stephen successions lie within different facies belts and should be regarded as separate formations; the Stephen Shale Formation is part of the Middle Carbonate Belt succession, whereas the name Burgess Shale Formation is applied to the thick basinal succession within the Outer Detrital Belt Chancellor Group. Ten distinct members are recognized in the Burgess Shale: Kicking Horse Shale, Yoho River Limestone, Campsite Cliff Shale, Wash Limestone, Walcott Quarry Shale, Raymond Quarry Shale, Emerald Lake Oncolite, Odaray Shale, Paradox Limestone, and Marpole Limestone. In contrast to the Stephen Shale Formation with its nonsequences, the thicker Burgess Shale Formation seems to represent continuous deposition spanning the Glossopleura to Bathyuriscus-Elrathina zonal boundary, incorporating the Polypleuraspis insignis and Pagetia bootes subzones and the main part of the Pagetia walcotti subzone.

Polypleuraspis (Arthropoda, Trilobita) from the middle Cambrian (Miaolingian Series) around Kane Basin (Nunavut and Greenland)

2020 ◽  
Vol 57 (1) ◽  
pp. 16-24
Author(s):  
John S. Peel
Keyword(s):  
British Columbia ◽  
New Species ◽  
North American ◽  
Type Species ◽  
Wood Formation ◽  
Ellesmere Island ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Shale Formation ◽  
A New Species

Polypleuraspis Poulsen, 1927, originally established on the basis of a single trilobite pygidium from the Cape Wood Formation of Inglefield Land, northwestern Greenland, is redescribed on the basis of material from additional occurrences in the Cape Wood and Telt Bugt formations exposed around Kane Basin in Ellesmere Island (Nunavut) and northern and northwestern Greenland. Polypleuraspis occurs together with Glossopleura Poulsen, 1927 in the Glossopleura walcotti Poulsen, 1927 Biozone of the Delamaran Stage of North American (Laurentian) usage, in middle Cambrian strata (Miaolingian Series) of the Wuliuan Stage. The type species, Polypleuraspis solitaria Poulsen, 1927, is compared with Polypleuraspis insignis Rasetti, 1951 from the Stephen Formation (Burgess Shale Formation) of British Columbia and to a new species from the Telt Bugt Formation of Daugaard-Jensen Land: Polypleuraspis glacialis sp. nov. Polypleuraspis cooperi Robison and Babcock, 2011, from the Spence Shale of Utah of similar age, is assigned to Polypleuraspidella gen. nov.

scholarly journals Skimming the surface with Burgess Shale arthropod locomotion

2011 ◽  
Vol 279 (1733) ◽  
pp. 1613-1620 ◽  
Author(s):  
Nicholas J. Minter ◽  
M. Gabriela Mángano ◽  
Jean-Bernard Caron
Keyword(s):  
Direct Evidence ◽  
The Body ◽  
Sedimentation Rates ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Ecological Information ◽  
Mode Of Life ◽  
Bottom Waters ◽  
Shale Formation ◽  
Chengjiang Biota

The first arthropod trackways are described from the Middle Cambrian Burgess Shale Formation of Canada. Trace fossils, including trackways, provide a rich source of biological and ecological information, including direct evidence of behaviour not commonly available from body fossils alone. The discovery of large arthropod trackways is unique for Burgess Shale-type deposits. Trackway dimensions and the requisite number of limbs are matched with the body plan of a tegopeltid arthropod. Tegopelte , one of the rarest Burgess Shale animals, is over twice the size of all other benthic arthropods known from this locality, and only its sister taxon, Saperion , from the Lower Cambrian Chengjiang biota of China, approaches a similar size. Biomechanical trackway analysis demonstrates that tegopeltids were capable of rapidly skimming across the seafloor and, in conjunction with the identification of gut diverticulae in Tegopelte , supports previous hypotheses on the locomotory capabilities and carnivorous mode of life of such arthropods. The trackways occur in the oldest part (Kicking Horse Shale Member) of the Burgess Shale Formation, which is also known for its scarce assemblage of soft-bodied organisms, and indicate at least intermittent oxygenated bottom waters and low sedimentation rates.

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.

A new Late Silurian (Pridolian) naraoiid (Euarthropoda: Nektaspida) from the Bertie Formation of southern Ontario, Canada—delayed fallout from the Cambrian explosion

2004 ◽  
Vol 78 (6) ◽  
pp. 1138-1145 ◽  
Author(s):  
Jean-Bernard Caron ◽  
David M. Rudkin ◽  
Stuart Milliken
Keyword(s):  
Late Ordovician ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Soft Bottom ◽  
Southern Ontario ◽  
Middle Cambrian ◽  
Holotype Specimen ◽  
Extinction Events ◽  
Lazarus Effect ◽  
Mass Extinction Events

The discovery of a new naraoiid nektaspid in the Upper Silurian (Pridolian) of southeastern Ontario significantly extends the range of this unusual group. Nektaspids are nonmineralized arthropods typical of Early and Middle Cambrian soft-bottom communities, but were thought to have become extinct in the Late Ordovician. The unique holotype specimen of Naraoia bertiensis n. sp. comes from a Konservat–Lagerstätte deposit renowned for its eurypterid fauna (the Williamsville Member of the Bertie Formation). Naraoia bertiensis lacks thoracic segments and is morphologically similar to Naraoia compacta from the Middle Cambrian Burgess Shale, save for the presence of a long ventral cephalic doublure and a subtly pointed posterior shield. To examine the phylogenetic relationships of the new naraoiid, we coded characters of the holotype specimen and of nine previously described nektaspids. The results confirm a sister taxon relationship between Naraoia compacta and Naraoia bertiensis and the monophyly of nektaspid forms lacking thoracic segments (family Naraoiidae). This latter group may have arisen from an ancestral segment-bearing form through heterochronic loss of thoracic segments early in the Cambrian. The disjunct occurrence of a naraoiid nektaspid in the Late Silurian resembles the reappearance of other “Lazarus taxa” that were thought to have been eliminated during mass extinction events. The naraoiid lineage survived the Late Ordovician biotic crisis, but in this case the “Lazarus effect” seems likely to be taphonomic in origin.

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