Eggshell membrane and porosity in Massospondylus eggs (BP/1/5347). (a) Nest of Massospondylus eggs with preserved embryos. Note the presence of numerous cracks in the eggs, likely caused by postmortem crushing of the thin but hard eggshell. Eggshell membrane is exposed in egg number 4, just beneath the skull, and in egg number 7, just beneath the right scapula. (b) CT scan of a complete egg in a, showing the eggshell (es) and the detached preserved eggshell membrane (em). (c) Outer surface SEM image of a Massospondylus eggshell fragment showing rare small and irregularly shaped pores occurring in random patterns (red arrows). (d) Enlarged view of boxed area in (c). See also Figs S1–S3.