Fig. 3

Cirrate egg capsules without macroscopically visible embryos. a Specimen G: egg capsule with chorion and sediment particles, lateral (above) and top view (below). b Specimen G: egg capsule with chorion, lateral view. c Specimen H: egg capsule with irregular structuring (left) and extracted chorion with large external yolk sac (right). d Specimen I: egg capsule with longitudinal striations and rupture exposing chorion. e Specimen I: virtual longitudinal section through 3D MRI data set showing chorion and external yolk sac—note the conspicuous gap between chorion and egg capsule. f Specimen J: egg capsule with longitudinal striations and white cristalline matter (left) as well as potential attachment areas to a hard substrate (right). g Specimen J: virtual longitudinal section showing chorion and external yolk sac. i Specimen K: egg capsule with potential apical attachment area to a hard substrate. j Specimen K: virtual longitudinal section showing chorion and external yolk sac—note the absence of a gap between chorion and egg capsule. Image a courtesy Frederick G. Hochberg. aa = attachment area, ch = chorion, ec = egg capsule, es = external yolk sac, gm = gelatinous matter, se = sediment. Scale bars = 1 mm, (e–h, k, j) not to scale