Fig. 4

Cirrate egg capsules with embryos. a Specimen L: unnaturally ruptured egg capsule with longitudinal striations, chorion partially visible—note the large gap between chorion and egg capsule. b Specimen L: volume rendering of a 3D µCT data set of the artificially opened chorion showing embryo with 1 mm ML still attached to the large external yolk sac. c Specimen L: volume renderings of the extracted embryo in dorsal (top), ventral (center), and right lateral view (bottom). d Specimen L: semi-transparent volume rendering of the embryo showing a surface-rendered model of the open U-shaped shell, dorsal view. e Specimen M: egg capsule presumably naturally ruptured due to swelling of the chorion. f Specimen M: extracted and artificially opened chorion showing embryo with 10 mm ML detached from large external yolk sac. g Specimen M: extracted embryo in dorsal (top), ventral (center), and right lateral view (bottom). h Specimen M: close-up ventral view of the embryo's arm crown and funnel aperture—note the absence of cirri. Images (e–h) courtesy Francisco J. Cristobo. ar = arm, ch = chorion, ec = egg capsule, em = embryo, es = external yolk sac, ey = eye, fc = fin cartilage, fi = fin, fu = funnel, gi = gill, in = intestine, ma = mantle, sh = shell, su = sucker. Scale bars = 1 mm