Minute theropod eggs and embryo from the Lower Cretaceous of Thailand and the dinosaur-bird transition.
We report on very small fossil eggs from the Lower Cretaceous of Thailand, one of them containing a theropod embryo, which display a remarkable mosaic of characters. While the surficial ornamentation is typical of non-avian saurischian dinosaurs, the three-layered prismatic structure of the eggshell is currently known only in extant and fossil eggs associated with birds. These eggs, about the size of a goldfinch's, mirror at the reproductive level the retention of small body size that was paramount in the transition from non-avian theropods to birds. The egg-layer may have been a small feathered theropod similar to those recently found in China.
Buffetaut
Eric
E
CNRS (UMR 5125, Paléoenvironnements et Paléobiosphère), 16 cour du Liégat, 75013 Paris, France. eric.buffetaut@wanadoo.fr
Grellet-Tinner
Gerald
G
Suteethorn
Varavudh
V
Cuny
Gilles
G
Tong
Haiyan
H
Kosir
Adrijan
A
Cavin
Lionel
L
Chitsing
Suwanna
S
Griffiths
Peter J
PJ
Tabouelle
Jérôme
J
Le Loeuff
Jean
J
D000818:Animals; D001717:Birds / Q000033:anatomy & histology* / Q000196:embryology; D002681:China; D025061:Dinosaurs / Q000033:anatomy & histology* / Q000196:embryology; D004625:Embryo, Nonmammalian; D005260:Female; D005580:Fossils; D008855:Microscopy, Electron, Scanning; D010063:Ovum / Q000648:ultrastructure; D010163:Paleontology; D013785:Thailand