Journal article
Relationships of Cambrian Arachnata and the systematic position of Trilobita
Journal of paleontology, Vol.73(2), pp.263-287
Second international trilobite conference
03/1999
DOI: 10.1017/S0022336000027761
Abstract
Cladistic relationships of Trilobita, Naraoiidae (five ingroup taxa), Helmetiida (five ingroup taxa), Xandarellida, and the Cambrian arachnates Retifacies, Sinoburius, Emeraldella, and Sidneyia are investigated based on 29 characters. Documentation of appendage morphology and other ventral structures in Saperion from the Chengjiang fauna permits an appraisal of helmetiid relationships. A monophyletic Trilobita [= "Olenellida" (Emuellida + Eutrilobita)] is defined by numerous synapomorphies, including exoskeletal calcification and dorsal eyes with calcified lenses and circumocular sutures. Helmetiida is a robust clade, resolved as (Helmetiidae (Tegopeltidae (Saperiidae + Skioldiidae))). Naraoiid monophyly is well-supported, but neither a naraoiid-trilobite nor a naraoiid-Retifacies clade are parsimonious, the latter grouping ("Nectopleura") being explicitly paraphyletic. A sister group relationship between Xandarellida and Sinoburius is endorsed, although character support is novel compared to previous groupings of these taxa. The fourth postantennal limb pair in trilobites, naraoiids, and apparently helmetiids is based beneath the cephalothoracic articulation. Reweighted characters favor Trilobita and Helmetiida as closest relatives, with Petalopleura and then araoiidae as sister groups.
Details
- Title: Subtitle
- Relationships of Cambrian Arachnata and the systematic position of Trilobita
- Creators
- Gregory D Edgecombe - Australian MuseumLars Ramskold - Uppsala UniversityJonathan M Adrain - Natural History Museum, Department of Palaeontology London GBR United KingdomStephen R Westrop - University of Oklahoma
- Resource Type
- Journal article
- Publication Details
- Journal of paleontology, Vol.73(2), pp.263-287
- Conference
- Second international trilobite conference
- Publisher
- Paleontological Society
- DOI
- 10.1017/S0022336000027761
- ISSN
- 0022-3360
- eISSN
- 1937-2337
- Alternative title
- Trilobite paleobiology; past, present, and future
- Language
- English
- Date published
- 03/1999
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240911402771
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