Maotianshania cylindrica

Cricocosmia (not Circocosmia, a very common misspelling!) and Maotianshania are really difficult to distinguish - the size is almost the same, but trunk ornamentation seems to be slightly different. I wouldn't dare to distinguish them without a very good microscope.
Lit.:
Han, J., Liu, J., Zhang, Z., Zhang, X., and Shu, D. 2007. Trunk ornament on the palaeoscolecid worms Cricocosmia and Tabelliscolex from the Early Cambrian Chengjiang deposits of China. Acta Palaeontologica Polonica 52 (2): 423–431.

Excerpt:

"Maotianshania cylindrica Sun and Hou, 1985 bears numerous irregularly arranged uniform trunk sclerites, SEM

analysis revealing that each sclerite bears four nodes (Hu 2005); the trunk of Cricocosmia jinningensis Hou and Sun, 1988 is well known for bearing double rows of lateral conical sclerites, but little is yet know about the microstructure of these sclerites."

Figure 2 Representatives of Chengjiang priapulids. (a) Maotianshania cylindrica Sun & Hou, 1987; (b) Palaeoscolex sinensis Hou & Sun, 1988; (c)

Cricocosmia jinningensis Hou & Sun, 1988;

I must have read the correct spelling a hundred times and it never sunk in...Thank you for the correction! 

They are indeed very difficult to distinguish, and my classification of this fossil may be wrong. I don't however see any "large paired sclerites along the trunk" (Hou et al, 2017).

I've just re-read Hou et al 2017, and would add that Maotianshania has 3-4 annuli per millimeter, whereas Cricocosmia has nearly half that number, at 2-2.4 annuli per millimeter. I think it fair to classify this fossil at Maotianshania based on its higher annuli per millimeter density. 

Hou et al. 2017, the chapter "Priapulida and Relatives" in 'The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life, pp.114-137'? Didn't know the difference of annuli per millimeter. Helped me a lot.

I knew, I should have bought this book...

Thanks Marcus

2 minutes ago, oilshale said:

I knew, I should have bought this book...

Just PM me your email address and I'll send it to you via WeShare

-Marc