INVESTIGADORES
FERNANDEZ Mariela Soledad
congresos y reuniones científicas
Título:
REPORT ON A THEROPOD NESTING SITE FROM HYOGO, JAPAN
Autor/es:
KOHEI TANAKA; DARLA K. ZELENITSKY; MARIELA S. FERNÁNDEZ; HARUO SAEGUSA; TADAHIRO IKEDA
Lugar:
Caparica
Reunión:
Simposio; VI Symposium of Eggs and babies; 2017
Resumen:
The Lower Cretaceous (Albian) Kamitaki locality in the eastern Hyogo Prefecture of southwestern Japan has yielded various dinosaur skeletal remains and eggshells, which revealed a high diversity of dinosaurs in the region. Although the previous discoveries of egg remains were limited in tiny eggshell fragments, here we report on a newly discovered nearly complete and partial eggs and discuss nesting behavior of dinosaurs at the locality.The new eggs were found from mudstone layers about five meters above the bonebed layer where eggshell fragments (e.g., Spheroolithus, Elongatoolithus, Prismatoolithus, and Nipponoolithus) and skeletal remains of dinosaurs (e.g., titanosaurs) have been yielded. So far, up to eight nearly complete and partial eggs, along with numerous scattered eggshell fragments, have been recognized at this level. Because these eggs are small (estimated to 5 cm by 2 cm) and thin (< 0.2 mm in shell thickness), they were likely laid by a small animal. The microstructure of the eggshell, which has two structural layers (i.e., mammillary and continuous layers), is consistent among the eggs and scattered eggshells, suggesting that they represent a single ootaxon likely belonging to a non-avian maniraptoran theropod.Taphonomic evidence suggests that this nesting site was repeatedly used by the dinosaur. Analysis of scattered eggshell fragments around partial eggs revealed that over 60% of eggshells were concave-up, rather than concave-down, indicating that the eggs/eggshells are in-situ and were unlikely transported far from the nesting site. Some eggs were found in clusters, representing partial clutches, and were situated at slightly different stratigraphic levels, which suggests that they were laid at different nesting seasons and thus infers nest site fidelity. The new nesting site of the Kamitaki locality therefore can provide insight into nesting behavior of small non-avian theropod dinosaurs in Lower Cretaceous, which have been poorly documented previously.