| 1. |
- Budd, Graham E., et al.
(författare)
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The lobes and lobopods of Opabinia regalis from the middle Cambrian Burgess Shale
- 2012
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 45:1, s. 83-95
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Tidskriftsartikel (refereegranskat)abstract
- Despite many papers devoted to it, the morphology of the Burgess Shale animal Opabinia regalis continues to excite controversy. In particular, the trunk region remains incompletely understood, leading to several recent attempts to interpret the fossil in radically different ways. New material of Opabinia from the Royal Ontario Museum and the Smithsonian collection, together with the recent description of comparative material of the Burgess Shale anomalocaridid Hurdia, help clarify details of its morphology, in particular with regards to the lateral lobes and setal blades. A recent reconstruction of the trunk lobes is rejected, and further evidence for the presence of trunk limbs is presented. Despite disagreements over its morphology, the phylogenetic placement of Opabinia is now relatively uncontroversial, although various derived aspects of its morphology complicate placing it precisely.
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| 2. |
- Caron, Jean-Bernard, et al.
(författare)
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A new Burgess Shale-type assemblage from the "thin" Stephen Formation of the Southern Canadian Rockies
- 2010
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Ingår i: Geology. - 0091-7613 .- 1943-2682. ; 38:9, s. 811-814
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Tidskriftsartikel (refereegranskat)abstract
- A new Burgess Shale–type assemblage, from the Stephen Formation of the southern Canadian Rocky Mountains, is described herein. It occurs near Stanley Glacier in Kootenay National Park, 40 km southeast of the type area near Field, British Columbia. While at least a dozen Burgess Shale localities are known from the “thick” Stephen Formation, the Stanley Glacier locality represents the first discovery of Burgess Shale–type fossils from the “thin” Stephen Formation. The Cathedral Escarpment, an important regional paleotopographic feature, has been considered important to the paleoecologic set- ting and the preservation of the Burgess Shale biota. However, the Stanley Glacier assemblage was preserved in a distal ramp setting in a region where no evidence of an escarpment is present. The low- diversity assemblage contains eight new soft-bodied taxa, including the anomalocaridid Stanleycaris hirpex n. gen., n. sp. (new genus, new species). Pelagic or nektobenthic predators represent the most diverse group, whereas in relative abundance, the assemblage is dominated by typical Cambrian shelly benthic taxa. The low diversity of both the benthic taxa and the ichnofauna, which includes diminutive trace fossils associated with carapaces of soft-bodied arthropods, suggests a paleoenvironment with restrictive conditions. The Stanley Glacier assemblage expands the temporal and geographic range of the Burgess Shale biota in the southern Canadian Rockies, and suggests that Burgess Shale–type assemblages may be common in the “thin” Ste- phen Formation, which is regionally widespread.
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| 3. |
- Daley, Allison C., et al.
(författare)
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A possible anomalocaridid from the Cambrian Sirius Passet lagerstätte, North Greenland
- 2010
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Ingår i: Journal of Paleontology. - 0022-3360 .- 1937-2337. ; 84:2, s. 352-355
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Tidskriftsartikel (refereegranskat)abstract
- The Sirius Passet biota of North Greenland is one of the oldest Cambrian lagerstätten, and although it is dominated by non-mineralized arthropods and lobopods, anomalocaridids have never been identified. Based on a single specimen, we herein describe for the first time an appendage with possible anomalocaridid affinities as suggested by an overall gross morphology similar to that of the frontal appendage of Anomalocaris from other localitites. Tamisiocaris borealis n. gen. and n. sp. has an elongated appendage with paired spines along one margin, and differs from the frontal appendage of Anomalocaris in that segment boundaries are absent and ventral spines are relatively long and spineless. These differences may be taphonomic, but the entire surface of the appendage is covered in a fine fabric, making it unlikely that this appendage was originally segmented or sclerotized. The taxon is tentatively placed within Radiodonta, but this systematic placement cannot be confirmed while complete body specimens are lacking.
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| 4. |
- Daley, Allison C, et al.
(författare)
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Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah
- 2013
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Ingår i: Journal of Systematic Palaeontology. - : Informa UK Limited. - 1477-2019 .- 1478-0941. ; 11:7, s. 743-787
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Tidskriftsartikel (refereegranskat)abstract
- In Cambrian fossil Lagerstätten like the Burgess Shale, exceptionally preserved arthropods constitute a large part of the taxonomic diversity, providing opportunities to study the early evolution of this phylum in detail. The anomalocaridids, large presumed pelagic predators, are particularly relevant owing to their unique combination of morphological characters and basal position in the arthropod stem lineage. Although isolated elements and fragmented specimens were first discovered over 100 years ago, subsequent findings of more complete bodies ofAnomalocaris and Peytoia, especially in the 1980s, allowed for a better understanding of these enigmatic forms. Their evolutionary significance as stem group arthropods was further clarified by the recent discovery of a third anomalocaridid taxon, Hurdia. Here, examination of hundreds ofHurdia specimens from different stratigraphical layers within the Burgess Shale and Stephen Formation, combined with statistical analyses, provides a detailed description of the taphonomy, morphology and diversity of the genus and further elucidates anomalocaridid systematics. Hurdiais distinguished from other anomalocaridids in having mouthparts with extra rows of teeth, a large frontal carapace complex and diminutive swimming flaps with prominent setal structures. The two original species, H. victoria Walcott, 1912 and H. triangulata Walcott, 1912, are confirmed based on morphometric outline analyses of the frontal carapace components combined with stratigraphical evidence; a third species, Hurdia dentata Simonetta & Delle Cave, 1975, is synonymized with H. victoria. Morphology, preservation and stratigraphical distribution suggest that H. victoria and H. triangulata share the same type of frontal appendage; a second type of appendage, previously assigned to Hurdia (Morph A), belongs to Peytoia nathorsti. These and other morphological differences between the anomalocaridids may reflect different feeding strategies. Appendages and mouthparts of Hurdia indet. sp. are also identified from the Spence Shale Member of Utah, making Hurdia and Anomalocaris the most common and globally distributed anomalocaridid taxa.
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| 5. |
- Daley, Allison C., et al.
(författare)
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New anomalocaridid appendages from the Burgess Shale, Canada
- 2010
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Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 53:4, s. 721-738
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Tidskriftsartikel (refereegranskat)abstract
- The complex history of description of the anomalocaridids has partly been caused by the fragmentary nature of these fossils. Frontal appendages and mouth parts are more readily preserved than whole-body assemblages, so the earliest work on these animals examined these structures in isolation. After several decades of research, these disarticulated elements were assembled together to reconstruct the anomalocaridid body plan, and a total of three Burgess Shale genera, Anomalocaris, Laggania, and Hurdia, were described in full. Here we present new frontal appendage material of additional anomalocaridid taxa from the ‘Middle’ Cambrian (Series 3) Burgess Shale Formation in Canada, showing that the diversity of anomalocaridids in this locality is even higher than previously thought. Material includes Amplectobelua stephenensis sp. nov., the first known occurrence of this genus outside of China; Caryosyntrips serratus gen. et sp. nov., which is similar to the Anomalocaris appendage but has a straighter outline and a different arrangement of spines; and an appendage that may be either the Laggania appendage or a third morph of the Hurdia appendage. The new anomalocaridid material is contemporaneous with the previously described taxa Anomalocaris, Laggania, and Hurdia, and the differences in morphology between the frontal appendages may reflect different feeding strategies. The stratigraphically lowest locality, S7 on Mount Stephen, yields material from all anomalocaridid taxa, but the assemblages in the younger quarries on Fossil Ridge are dominated by Anomalocaris and Hurdia only.
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| 6. |
- Daley, Allison C.
(författare)
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Statistical analysis of mixed-motive shell borings in Ordovician, Silurian, and Devonian brachiopods from northern and eastern Canada
- 2008
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Ingår i: Canadian journal of earth sciences (Print). - 0008-4077 .- 1480-3313. ; 45:2, s. 213-229
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Tidskriftsartikel (refereegranskat)abstract
- Hundreds of shell borings of different origin and displaying variable patterns were found in strophomenide, pentameride, and orthide brachiopods of five Paleozoic localities in northern and eastern Canada. The borings were analyzed using simple statistics as well as cluster and nonmetric multidimensional scaling analyses. At the Ordovician Anticosti Island locality, all borings are parasitic or post-mortem in origin, while at the Wenlock-Ludlow Baillie-Hamilton Island, almost all borings are predatory. At the remaining three localities, borings represent a mix of predatory, parasitic, and post-mortem domichnial borings in all three brachiopod taxa, the proportions of which were controlled largely by brachiopod shell morphology and paleoecology. For the strophomenides, predatory borings can be segregated from parasitic and post-mortem domichnial using simple and multivariate statistical analyses. Sowerbyella-type strophomenides have a higher proportion of predatory borings at the Lochkovian localities than at the Ordovician localities, while the reverse is true for the Strophomena-type strophomenides. In pentamerides and orthides, very few predatory borings are identified; most borings were emplaced by parasitic or post-mortem domichnial borers. In pentamerides, this is due to the internal structure of the shells, which elevated the muscles of the organism above the shell floor, rendering them inaccessible to boring predators. In orthides, more deliberate defense mechanisms such as toxins or external ornamentation may have deterred predation. This study indicates that throughout the Paleozoic interactions between borers and brachiopods were complex but can be elucidated using a large sample size and statistical analyses.
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| 7. |
- Daley, Allison C., 1980-, et al.
(författare)
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The Burgess Shale Anomalocaridid Hurdia and Its Significance for Early Euarthropod Evolution
- 2009
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Ingår i: Science. - Washington, DC : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 323:5921, s. 1597-1600
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Tidskriftsartikel (refereegranskat)abstract
- As the largest predators of the Cambrian seas, the anomalocaridids had an important impact in structuring the first complex marine animal communities, but many aspects of anomalocaridid morphology, diversity, ecology, and affinity remain unclear owing to a paucity of specimens. Here we describe the anomalocaridid Hurdia, based on several hundred specimens from the Burgess Shale in Canada. Hurdia possesses a general body architecture similar to Anomalocaris and Laggania, including the presence of exceptionally well-preserved gills, but differs from those anomalocaridids by possessing a prominent anterior carapace structure. These features amplify and clarify the diversity of known anomalocaridid morphology and provide insight into the origins of important arthropod features, such as the head shield and respiratory exites.
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| 8. |
- Daley, Allison
(författare)
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The morphology and evolutionary significance of the anomalocaridids
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Approximately 600 to 500 million years ago, a major evolutionary radiation called the “Cambrian Explosion” gave rise to nearly all of the major animal phyla known today. This radiation is recorded by various fossil lagerstätten, such as the Burgess Shale in Canada, where soft-bodied animals are preserved in exquisite detail. Many Cambrian fossils are enigmatic forms that are morphologically dissimilar to their modern descendants, but which still provide valuable information when interpreted as stem-group taxa because they record the actual progression of evolution and give insight into the order of character acquisitions and homologies between living taxa. One such group of fossils is the anomalocaridids, large presumed predators that have had a complicated history of description. Their body has a trunk with a series of lateral lobes and associated gills, and a cephalic region with a pair of large frontal appendages, a circular mouth apparatus, stalked eyes and a cephalic carapace. Originally, two taxa were described from the Burgess Shale, Anomalocaris and Laggania, however data presented herein suggests that the diversity of the anomalocaridids was much higher. Newly collected fossil material revealed that a third Burgess Shale anomalocaridid, Hurdia, is known from whole-body specimens and study of its morphology has helped to clarify the morphology and systematics of the whole group. Hurdia is distinguished by having mouthparts with extra rows of teeth, a unique frontal appendage, and a large frontal carapace. Two species, Hurdia victoria and Hurdia triangulata were distinguished based on morphometric shape analysis of the frontal carapace. A phylogenetic analysis placed the anomalocaridids in the stem lineage to the euarthropods, and examination of Hurdia’s well-preserved gills confirm the homology of this structure with the outer branches of limbs in upper stem-group arthropods. This homology supports the theory that the Cambrian biramous limb formed by the fusion of a uniramous walking limb with a lateral lobe structure bearing gill blades. In this context, new evidence is present on the closely allied taxon Opabinia, suggesting that it had lobopod walking limbs and a lateral lobe structure with attached Hurdia-like gills. The diversity of the anomalocaridids at the Burgess Shale is further increased by two additional taxa known from isolated frontal appendages. Amplectobelua stephenensis is the first occurrence of this genus outside of the Chengjiang fauna in China, but Caryosyntrips serratus is an appendage unique to the Burgess Shale. To gain a better understanding of global distribution, a possible anomalocaridid is also described from the Sirius Passet biota in North Greenland. Tamisiocaris borealis is known from a single appendage, which is similar to Anomalocaris but unsegmented, suggesting this taxon belongs to the arthropod stem-lineage, perhaps in the anomalocaridid clade. Thus, the anomalocaridids are a widely distributed and highly diverse group of large Cambrian presumed predators, which provide important information relevant to the evolution of the arthropods.
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| 9. |
- Fischer, Antje H. L., et al.
(författare)
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ZOONET : perspectives on the evolution of animal form. Meeting report
- 2009
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Ingår i: Journal of Experimental Zoology. - Hoboken, N. J. : Wiley-Blackwell. - 0022-104X .- 1097-010X. ; 312B:7, s. 679-685
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Tidskriftsartikel (refereegranskat)abstract
- What drives evolution? This was one of the main questions raised at the final ZOONET meeting in Budapest, Hungary, in November 2008. The meeting marked the conclusion of ZOONET, an EU-funded Marie-Curie Research Training Network comprising nine research groups from all over Europe (Max Telford, University College London; Michael Akam, University of Cambridge; Detlev Arendt, EMBL Heidelberg; Maria Ina Arnone, Stazione Zoologica Anton Dohrn Napoli; Michalis Averof, IMBB Heraklion; Graham Budd, Uppsala University; Richard Copley, University of Oxford; Wim Damen, University of Cologne; Ernst Wimmer, University of Gottingen). ZOONET meetings and practical courses held during the past four years provided researchers from diverse backgrounds-bioinformatics, phylogenetics, embryology, palaeontology, and developmental and molecular biology-the opportunity to discuss their work under a common umbrella of evolutionary developmental biology (Evo Devo). The Budapest meeting emphasized in-depth discussions of the key concepts defining Evo Devo, and bringing together ZOONET researchers with external speakers who were invited to present their views on the evolution of animal form. The discussion sessions addressed four main topics: the driving forces of evolution, segmentation, fossils and phylogeny, and the future of Evo Devo.
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| 10. |
- Fu, Dongjing, et al.
(författare)
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The evolution of biramous appendages revealed by a carapace-bearing Cambrian arthropod
- 2022
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8436 .- 1471-2970. ; 377:1847
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Tidskriftsartikel (refereegranskat)abstract
- Biramous appendages are a common feature among modern marine arthropods that evolved deep in arthropod phylogeny. The branched appendage of Cambrian arthropods has long been considered as the ancient biramous limb, sparking numerous investigations on its origin and evolution. Here, we report a new arthropod, Erratus sperare gen. et sp. nov., from the Lower Cambrian (Stage 3, 520 Ma) Chengjiang biota of Yunnan, China, with unique trunk appendages formed of lateral anomalocaridid-type flaps and ventral subconical endopods. These appendages represent an intermediate stage of biramous limb evolution, i.e. from 'two pairs of flap appendages' in radiodonts to 'flap + endopod' in Erratus, to 'exopod + endopod' in the rest of carapace-bearing arthropods that populate the basal region of the upper-stem lineage arthropods (deuteropods). The new species occupies a phylogenetic position at the first node closer to deuteropods than to radiodonts, and therefore pinpoints the earliest occurrence of the endopod within Deuteropoda. The primitive endopod is weakly sclerotized, and has unspecialized segments without endites or claw. The findings might support previous claims that the outer branch of the biramous limb of fossil marine arthropods, such as trilobites, is not a true exopod, but is instead a modified exite. This article is part of the theme issue 'The impact of Chinese palaeontology on evolutionary research'.
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