Dickinsonia steroids not unique to animals

[piranha]

from: Science Magazine

 

Gregory J. Retallack, Department of Earth Sciences, University of Oregon (October 3, 2018)

Bobrovskiy et al. (1) have assembled impressive biomarker data which rules out three of five alternatives for the biological affinities of the problematic Ediacaran fossils Dickinsonia and Andiva. The cholesterols extracted from the fossils do indeed rule out affinities with lichenized fungi such as Ascomycota and Basidiomycota, and also with Rhizaria. This does not mean that Dickinsonia and Andiva were necessarily animals, because a third fungal phylum, Glomeromycota, also produces cholesterol without ergosterol (2). The living lichenized glomeromycotan, Geosiphon pyriformis, is unusual in housing the photosymbiont inside enlarged cells (3), and its fossil record may include Precambrian problematica such as Horodyskia (4) and Diskagma ranging in age back 2.2 Ga (5). Glomeromycotan fungi are also known from Ediacaran acritarchs with attached hyphae, stalked vesicles, complex wall ultrastructure, and chitin composition demonstrated by FTIR (6). A glomeromycotan lichen fragment preserved by cellular permineralization also has been described from Ediacaran rocks of China (7).

Cholesterol in Dickinsonia and Andiva permits both glomeromycotan and animal affinities, but additional observations provide a test of these alternatives. Bobrovskiy et al. (1) also found that the proportion of cholesterol relative to stigmasterol (a chlorophyte biomarker) increased in larger compared with smaller Dickinsonia. This is not what would be expected for a slow-moving or sessile animal increasingly fouled with algae as it grew, nor would such a regular decline be expected from vagaries of animal-feeding on algae. Declining stigmasterol with increasing cholesterol is compatible with building of fungal biomass by controlled populations of photosymbiotic algae. Dickinsonia and Andiva may have been glomeromycotan fungi lichenized with green algae. Undisputed Ediacaran animals trace and body fossils are small (< 5mm diameter) and vermiform with chitin or calcite skeletons, and have been characterized as Ediacaran Wormworld (8). In contrast, Dickinsonia and Andiva are part of a diverse group of large (up to 1.4 m) and unskeletonized, crustose to foliose, quilted organisms, from very different sedimentary facies (9), and could be characterized as Ediacaran Mattressland.

 

References and Notes
1. I. Brobovskiy, et al., Science 361, 1246-1249 (2018).
2. Fontaine et al. Lipids 36, 1357, 2001; J.D. Weete, M. Abril, M. Blackwell, PloS One 5(5), e10899 (2010).
3. A. Schüßler, M.Kluge, M., in The Mycota IX (ed. B. Hock), 151-161 (Springer, Berlin, 2000)
4. G.J. Retallack, K.L. Dunn, J. Saxby, J. Precambrian Research 126, 125–142 (2013).
5. G.J. Retallack, et al., Precambrian Research 235, 71-87 (2013).
6. G.J. Retallack, Botanica Pacifica 4(2), 19-33 (2015).
7. X. Yuan, S. Xiao, T. N. Taylor, Science 308, 1017-1020 (2005)
8. J.D. Schiffbauer et al. GSA Today 26(11), 4-11 (2016)
9. G.J. Retallack, Nature 493, 89-92 (2013), Gondwana Research 36, 94-110 (2016), Alcheringa 40, 583-600 (2016).

[Ludwigia]

I by have no means the expertise or understanding to give scientific support to the following suggestion, which is why I am framing it as a simple layman's question: Could it not be possible that some creatures way back at the beginnings of life on earth were both plant and animal at the same time?

[Bobby Rico]

2 minutes ago, Ludwigia said:

animal at the same time?

 Charnia  maybe a candidate  but I think it is thought of more as an animal now. Ediacaran sea pen-like animal that is named after Charnwood Forest  in my home town of Leicestershire UK

[piranha]

Charnia is considered incertae sedis.

[Bobby Rico]

1 minute ago, piranha said:

Charnia is considered incertae sedis.

Thanks it is a really interesting fossil . This is the specimen in my local museum New Walk Museum 

[Oxytropidoceras]

A related paper is:

 

Goryl, M., Marynowski, L., Brocks, J.J., Bobrovskiy, I. and Derkowski, 

A., 2018. Exceptional preservation of hopanoid and steroid biomarkers

in Ediacaran sedimentary rocks of the East European Craton. 

Precambrian Research, 316, pp.38-47.

https://www.sciencedirect.com/science/article/pii/S0301926818302316

 

Retallack’s  comment is part of an ongoing discussion between 

Dr. G. J. Retallack and other Earth scientists over whether the 

Ediacaran fauna are either fungi or something else and whether

the Ediacara Member of the Rawnsley Quartzite of South Australia

accumulated in either deep marine, shallow marine, or 

terrestrial depositional environments. Some papers are:

 

Retallack, G.J., 2013. Ediacaran life on land. Nature, 493(7430), p.89-92

https://www.nature.com/articles/nature11777

https://www.researchgate.net/profile/Gregory_Retallack

https://www.researchgate.net/publication/233909210_Ediacaran_life_on_land

 

Tarhan, L.G., Planavsky, N.J., Wang, X., Bellefroid, E.J., Droser, M.L. 

and Gehling, J.G., 2018. The late‐stage “ferruginization” of the 

Ediacara Member (Rawnsley Quartzite, South Australia): Insights 

from uranium isotopes. Geobiology, 16(1), pp.35-48.

https://www.researchgate.net/publication/320907331_The_late-stage_ferruginization_of_the_Ediacara_Member_Rawnsley_Quartzite_South_Australia_Insights_from_uranium_isotopes

https://www.researchgate.net/profile/Lidya_Tarhan

 

Tarhan, L.G., Droser, M.L., Gehling, J.G. and Dzaugis, M.P., 2017.

Microbial mat sandwiches and other anactualistic sedimentary

features of the Ediacara Member (Rawnsley Quartzite, South

Australia): Implications for interpretation of the Ediacaran

sedimentary record. Palaios, 32(3), pp.181-194.

https://www.researchgate.net/publication/314288480_Microbial_mat_sandwiches_and_other_anactualistic_sedimentary_features_of_the_Ediacara_Member_Rawnsley_Quartzite_South_Australia_Implications_for_interpretation_of_the_Ediacaran_sedimentary_record

https://www.researchgate.net/profile/Lidya_Tarhan

 

Counts, J.W., Rarity, F., Ainsworth, R.B., Amos, K.J., Lane, T., 

Moron, S., Trainor, J., Valenti, C. and Nanson, R., 2016. 

Sedimentological interpretation of an Ediacaran delta: Bonney 

Sandstone, South Australia. Australian Journal of Earth 

Sciences, 63(3), pp.257-273.

https://www.researchgate.net/publication/303498844_Sedimentological_interpretation_of_an_Ediacaran_delta_Bonney_Sandstone_South_Australia

https://www.researchgate.net/profile/John_Counts

 

The Adelaide Rift Complex in the Flinders Ranges: Geologic 

history, past investigations and relevant analogues

https://www.researchgate.net/profile/John_Counts

https://www.researchgate.net/project/Sedimentology-Provenance-and-Salt-Sediment-Interaction-in-the-Ediacaran-Pound-Subgroup-Flinders-Ranges-South-Australia

 

Yours,

 

Paul H.