Functional Interpretation of the Sacs of Ancyrochitina fragilis Eisenack, and the Paleobiology of the Ancyrochitinids

Scanning electron microscopy reveals details of appendage sacs of Ancyrochitina fragilis Eisenack, here interpreted as flotation organs. All ancyrochitinid chitinozoans are concluded to have possessed sacs or similar flotation organs at some life stage and to have been free-living, active, planktonic metazoans.