Cnidarian Medusae (Jellyfish)
One of the most significant discoveries from the Middle Cambrian soft-bodied faunas of Utah has been of the oldest record of definitive fossilized cnidarian medusae, or jellyfish. All jellyfish are members of the phylum Cnidaria, which also includes animals such as corals, sea anemones, and the fresh water animal Hydra. Many circular shaped impressions on sedimentary rocks have been attributed to jellyfish, but the Utah fossils show a different style of preservation that reveals amazing details such as tentacles and varius organ structures.
These medusae fossils were recently published by Cartwright et al. (2007) in the open access journal PLoS One. Anyone may access and read this scientific report by clicking on the link below:
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.
The superb preservation of the fossil jellyfish specimens allowed Cartwright et al. (2007) to assign them to four different cnidarian groups, all of which are still alive today:
Gallery of Cnidarian Medusae
Notes: All scale bars are 5 mm in length unless otherwise indicated. All specimens are housed in the University of Utah Paleontology Collections.
Class Hydrozoa, Family Narcomedusae
UU 07021.03. Marjum Formation, House Range, Millard County, Utah. Figure 3 in Cartwright et al. (2007).
UU 07021.04. Marjum Formation, House Range, Millard County, Utah. Figure 4 in Cartwright et al. (2007).
Class Scyphozoa, Order Semaeostomeae
UU 07021.09. Marjum Formation, House Range, Millard County, Utah. Figures 5, 6 in Cartwright et al. (2007). Bottom figure shows close-up view of "structures interpreted as radially arranged coronal muscles" (Cartwright et al., 2007, p. 4).
UU 07021.10. Marjum Formation, House Range, Millard County, Utah. Figures 7,8 in Cartwright et al. (2007). Bottom figure shows close-up view of "structures interpreted as folded gonads " (Cartwright et al., 2007, p. 5). Scale bar in bottom figure = 2.5 mm.
Class Scyphozoa, Order Coronatae
UU 07021.05. Marjum Formation, House Range, Millard County, Utah. Figure 9 in Cartwright et al. (2007). Abbreviations: Cg = coronal groove; L = lappets; and T = tentacles.
UU 07021.01. Marjum Formation, House Range, Millard County, Utah. Figure 10 in Cartwright et al. (2007). Abbreviations: Ped = pedalia.
UU 07021.02. Marjum Formation, House Range, Millard County, Utah. Figure 11 in Cartwright et al. (2007). Abbreviations: Nb = nematocyst batteries.
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