uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
The lobes and lobopods of Opabinia regalis from the middle Cambrian Burgess Shale
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. (Palaeobiology)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. (Palaeobiology)
2012 (English)In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 45, no 1, 83-95 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2012. Vol. 45, no 1, 83-95 p.
Keyword [en]
Biramous limb, Burgess Shale, exceptional preservation, Opabinia regalis
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-114193DOI: 10.1111/j.1502-3931.2011.00264.xISI: 000298301900009OAI: oai:DiVA.org:uu-114193DiVA: diva2:293434
Available from: 2010-02-11 Created: 2010-02-11 Last updated: 2012-02-07Bibliographically approved
In thesis
1. The morphology and evolutionary significance of the anomalocaridids
Open this publication in new window or tab >>The morphology and evolutionary significance of the anomalocaridids
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 40 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 714
anomalocaridids, Cambrian, Burgess Shale, exceptional preservation, palaeontology
National Category
Research subject
Historical Geology and Paleontology
urn:nbn:se:uu:diva-114102 (URN)978-91-554-7723-3 (ISBN)
Public defence
2010-03-26, Hambergsalen, Villavägen 16, Institutionen för geovetenskaper, 10:00 (English)
Available from: 2010-03-03 Created: 2010-02-10 Last updated: 2010-03-03Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Budd, Graham E.
By organisation
In the same journal
Lethaia: an international journal of palaeontology and stratigraphy
Biological Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 277 hits
ReferencesLink to record
Permanent link

Direct link