Re: Allosaur baby faces

[Michael Lovejoy <michael@palaeoproductions.fsnet.co.uk>]

Chris Taylor wrote: 'does anyone know if coelurosaurs laid hard-shelled eggs
like modern birds, or leathery-shelled eggs like other reptiles? What is the
earliest branch on the avian stem that we can be sure laid a hard egg?'

According to Dingus and Chiappe, all dinosaurs laid hard shelled eggs. These
can be broken down into three types:
Spherulitic, in which an inner core supports stacks of calcite crystals that
radiate out from it. this type is considered typical of all dinosaurs except
theropods.
Prismatic, composed of an inner core that supports two crystalline layers,
with an indistinct boundary. Inner layer of radiating crystals, with an
outer layer of prism like structures. typical of primitive theropods.
Ornithoid, also composed of an inner core supporting two or more crystalline
layers, but with dinstinct and abrupt boundaries. The lower or inner part is
similar to that of the prismatic type, but the upper or outer part has a
scaly (?) appearance. (not sure what they mean by scaly.) Ornithoid
structure is typical of advanced theropods and all birds.

Regards,
Michael Lovejoy
Paleo Studio