Careful study and description of the incredible diversity of soft-bodied fossils from the Middle Cambrian of Utah over the last 30 years has permitted investigations of the broader evolutionary and paleobiogeographic contexts of these remarkable fossils. Especially imporant descriptive work includes the research of:
Exploring the evolutionary and paleobiogeographic context of this documented diversity has been the focus of significant research in recent years in the Division of Invertebrate Paleontology at the University of Kansas. This research was supported by National Science Foundation Grant EAR-0518976.
One of the major goals of this research was to resolve the relationships of arachnomorph arthropods. In particular, cladistic methods were used to explore the relationships of two new genera from the Middle Cambrian of Utah, Dicranocaris and Nettapezoura to previously described species from other deposits, including the Burgess Shale and Chengjiang soft-body faunas (see Hendricks & Lieberman, 2008).
One of our results is shown to the right (Hendricks & Lieberman, 2007, fig. 3). Besides identifying Sidneyia as the sister taxon (i.e., closest relative) of Nettapezoura and Alalcomenaeus as the sister taxon of Dicranocaris, this research demonstrates that trilobites (group in red) are evolutionarily derived arachnomorphs. This suggests that many other arthropod groups known only from soft-body deposits must be at least as old, if not older, than trilobites, a group which had likely diverged before 550 million years ago.
After this phylogenetic analysis was completed, the branching order of the tree, in conjunction with biogeographic information, was used to study the role of continental breakup in driving the observed patterns (see Hendricks & Lieberman, 2007). This research found that cyclic environmental events such as sea-level change, as well as the dispersal ability of the animals themselves, were likely repsonsible for the observed evolutionary patterns.
A second approach to studying paleobiogeographic in soft-body fossils has involved using geographic information systems (GIS) and models of ancient paleogeography to compare distributional patterns in trilobite and non-trilobite arthropod species using a newly compiled database derived from literature and museum sources (work in revision by Hendricks, Lieberman, and Stigall; for GSA abstract, click <here>). Surprisingly, this research has shown that soft-body arthropod species were, on average, more widely distributed than trilobites.
Papers resulting from recent research on soft-body fossils from the Middle Cambrian of Utah:
Briggs, D. E. G., Lieberman, B. S., Halgedahl, S. L. & Jarrard, R. D. 2005. A new metazoan from the Middle Cambrian of Utah and the nature of the Vetulicolia. Palaeontology, 48(4): 681-686. <Download PDF>
Briggs, D. E. G, Lieberman, B. S., Hendricks, J. R., Halgedahl, S. L., & Jarrard, R. D. 2008. Middle Cambrian arthropods from Utah. Journal of Paleontology, 82(2): 238-254. <Download PDF>
Cartwright, P., Halgedahl, S. L., Hendricks, J. R., Jarrard, R. D., Marques, A. C., Collins, A. G. & Lieberman, B. S. 2007. Exceptionally preserved jellyfishes from the Middle Cambrian. PLoS ONE 2(10): e1121. doi:10.1371/journal.pone.0001121. <Download PDF>
Hendricks, J. R. & Lieberman, B. S. 2007. Biogeography and the Cambrian radiation of arachnomorph arthropods. Memoirs of the Association of Australasian Palaeontologists, 34: 29-40. <Download PDF>
Hendricks, J. R. & Lieberman, B. S. 2008 (in press). New phylogenetic insights into the Cambrian radiation of arachnomorph arthropods. Journal of Paleontology, 82(3): 585-594.
Hendricks, J. R., Lieberman, B. S. & Stigall, A. L. In Revision. Using GIS to study palaeobiogeographic and macroevolutionary patterns in soft-bodied Cambrian arthropods. Palaeogeography, Palaeoclimatology, Palaeoecology.
Lieberman, B. S. 2008. The Cambrian radiation of bilaterians: evolutionary origins and palaeontological emergence; earth history change and biotic factors. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 180-188. <Download PDF>
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