Complex Relationships of Pararotadiscus guishouensis in Life and Death

Paleoecological Significance of Complex Fossil Associations of the Eldonioid Pararotadiscus guishouensis with other Faunal Members of the Kaili Biota (Stage 5, Cambrian, South China)

by: Yuanlong Zhao, Mingkun Wang, Steven T. LoDuca, Xinglian Yang, Yuning Yang, Yujuan Liu, and Xin Cheng

Summarized by: Dinah Hunsicker. Dinah Hunsicker is currently an undergraduate senior studying Geology at the University of South Florida.  She will earn her Bachelor’s degree at the end of 2019. She has a passion for science, music, mathematics, and spends much of her time outdoors. She loves to garden and paint, and absolutely loves collecting cool rocks and minerals! (Favorite mineral: azurite).

What data were used? 628 collected fossil specimens from the Kaili Formation, Guizhou Province, South China preserved in association with the Pararotadiscus guishouensis, an organism that has a high likelihood to have shared symbiotic relationships with other groups. P. guishouensis is an eldonid, a medusoid (e.g., like jellyfish) -shaped organism that scientists aren’t entirely sure what groups it belongs to. 

Methods: Associated fossils were classified into 4 types of relationships with P. guishouensis  (symbiosis (interacting with one another), co-burial, attachment of benthic taxa on P. guishouensis carcasses, and scavenging of carcasses after death.

The figure above shows a variety of organisms preserved in the fossil record showing different types of symbiotic relationships with Pararotadiscus guizhouensis. Parts 5 and 6 show the symbiotic relationships between this fossil and brachiopods and how many brachiopods could be found in association on one organism.

Results: I have broken this into the 4 sections defined above. Symbiotic Relationship: brachiopods, trilobites, and juvenile echinoderms in this area were found to have symbiotic relationships with Pararotadiscus guishouensis (P. g.). Benthic (lived on the seafloor): organisms latched onto P. guishouensis, taking advantage of the calmer water current, giving them an opportunity to expand their ecological niche. Co-burial: it makes sense that since many of the previously mentioned critters latch on to P. g, they’ve committed to life and death with their host. Additionally, a variety of fragmented and partial fossils (bits and pieces of trilobites, brachiopods, echinoderms and algae) buried around the same time are also associated with P. guishouensis. Post-Mortem Attachment: the carcass of P. guishouensis was an oasis of solid mass on the soft-sediment seafloor, leading to a multitude of species taking up life habits on the carcasses of P. guishouensis, including colonization by echinoderms. Post-Mortem Scavenging: Among the 628 specimens, 24% are preserved with squiggling traces of surface scavenging, associated with worm-like creatures called Gordia marina. No evidence of any other type of scavenging relationship has been detected.

Why is this study important? This study contributes to the growing body of evidence that the ecology of the Cambrian biosphere was more intricate and complex than previously suspected; originally, scientists assumed the Cambrian had a general lack of ecological diversity. Insights relating to organismal interactions during the Cambrian can help us further our understanding about the inter-complexities of life on this planet through a broad lens of time.

The big picture: This well-preserved group of organisms, such such as brachiopods, trilobites, echinoderms, and a type of ancient sea worm co-habituated and had multi-layered, complex biotic relationships with Pararotadiscus guishouensis at the site of the Kaili Formation in China, giving us insight into the lives of these ancient sea critters, contributing to our conceptions and understandings about Cambrian life.

Citation: Zhao, Y., Wang, M., LoDuca, S., Yang, X., Yang, Y., Liu, Y., & Cheng, X. (2018). Paleoecological Significance of Complex Fossil Associations of the Eldonioid Pararotadiscus guizhouensis with other Faunal Members of the Kaili Biota (Stage 5, Cambrian, South China). Journal of Paleontology, 92(6), 972-981.