Comparison of fossil eggs (c) with existing soft-shelled, leathery, and hard-shelled eggs . Credit: IVPP
Phys.org has a story about dinosaur eggs. A paper in the journal National Science Review suggests that the first dinosaur eggs were leathery not hard as we see in modern day birds. The study looked at three skeletons from adult individuals and five egg clutches of the early Jurassic dinosaur Qianlong shouhu. The name Qianlong means "Guizhou dragon," while shouhu means "guarding"—a reference to the preservation of adult skeletal fossils in association with embryo-containing egg fossils. These dinosaurs were basal sauropodomorphs.
The calcareous layer of Qianlong eggs was much thicker than that of most soft-shelled eggs but thinner than that of hard-shelled eggs. The comparison of eggshell fragmentation among different eggshell types also suggests that the eggshell surface of Qianlong featured small fragments, similar to a leathery eggshell, in contrast with the folded surface of soft-shelled eggs or the large-fragmented surface of hard-shelled eggs. These observations indicate that Qianlong laid leathery eggs.
In order to test the macroevolutionary patterns of selected reproductive traits across the dinosaur–bird transition, the researchers assembled data from 210 fossil and extant species representing all major reptilian clades and tested evolutionary trends using multiple time-scaled phylogenies.
