Plagioolithus

Plagioolithus Temporal range: Upper Barremian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Egg fossil classification
Oofamily:	incertae sedis
Oogenus:	†Plagioolithus Imai and Azuma, 2015
Oospecies
†Plagioolithus fukuiensis Imai and Azuma, 2015 (type)

Plagioolithus is an

Plagioolithus is most notable for having a three-layered eggshell. This trait is widespread in modern birds, but is very rare among Mesozoic fossil eggs. No complete eggs have been found, so the size and shape of Plagioolithus eggs are unknown. Its eggshell is unornamented and very thin, measuring only 0.44 mm thick. The shell consists of a 0.18 mm mammillary layer (the innermost layer of the shell), a 0.18 mm continuous layer, and a 0.08 mm external layer. The pores are narrow, straight, and constant width throughout the shell.^[1]

Parentage

Because no embryos are known, the parent of Plagioolithus cannot be identified with certainty. It was formerly believed that triple-layered eggshells were unique to

Even though birds are known to be as old as the Late Jurassic, fossil eggs from before the Late Cretaceous are very rare. Indeed, Plagioolithus is the oldest known trace of bird eggs in the fossil record.^[1]

At the Kitadani Formation, numerous other dinosaurs are known to have coexisted with Plagioolithus, including