Palćos:		Procoelomates
INVERTEBRATES		Coeloscleritophora

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Coeloscleritophora

This Cambrian group includes the Halkeriida.  They are characterized by having a large number of small sclerites.  In fact, most members of the group are a large number of small sclerites, the actual body form being unknown.  Where known, the body plan includes a prominent internal cavity and restricted basal foramen -- something like a balloon with scales.  

The scales of coeloscleritophorans are distinctive in having a thin (<1µ) organic layer over the entire scale and an internal layer of aragonite fibers oriented along the long axis of the sclerite.  Most, like Siphoguchites in the image (scale bar = 100µ) also have (1) bundles of external aragonite fibers inclined toward the tip which look like microscales, and (2) a rim around the base which lacks these aragonite bundles.  See Porter (2005).  

Recent specimens from Chenjiang  suggest that the sclerites were embedded in a flexible, continuous layer of organic cuticle and stuck out "like cactus spines."   In this model, both scales and cuticle were formed by an epithelilial layer of living cells.  Bengston & Hou (2001).  ATW051231.

References

References

Bengston, S (2004), Early skeletal fossils, in JH Lipps & BM Waggoner (eds.), Neoproterozoic-Cambrian Biological Revolutions.  Pal. Soc. Papers 10: 67-77. WWW

Bengtson, S & VV Missarzhevsky (1981), Coeloscleritophora – a major group of enigmatic Cambrian metazoans. Short Pap. 2d Intn. Symp. Cambrian Syst., U.S. Geol. Surv. O.-F. Rep. 81-743: 19-21.