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Eggshells of small theropods from Lower Cretaceous of Japan

Ben Creisler

A new online paper:

Kohei Tanaka, Darla K. Zelenitsky, Haruo Saegusa, Tadahiro Ikeda,
Christopher L. DeBuhr & François Therrien (2015)
Dinosaur eggshell assemblage from Japan reveals unknown diversity of
small theropods.
Cretaceous Research (advance online publication)


We describe a diverse dinosaur eggshell assemblage from Japan.

Five different ootaxa, assignable to theropods and ornithopods were identified.

Nipponoolithus ramosus oogen. et oosp. nov. was erected as a new ootaxon.

This study reveals a hidden diversity of small theropods in Lower
Cretaceous Japan.


The Lower Cretaceous (Albian) Sasayama Group in the Hyogo Prefecture
of southwestern Japan has yielded various vertebrate fossils,
including skeletal remains of dinosaurs, anurans, lizards, and
mammals, and recently eggshell fragments. Here we report on numerous
fossil eggshells from the bone-bearing Kamitaki locality in Tamba
City, which represents a diverse dinosaur eggshell assemblage. Of the
more than 90 eggshell fragments recovered, five different types were
identified, including eggshells that likely belong to a variety of
theropods (Nipponoolithus ramosus oogen. et oosp. nov.,
Elongatoolithus sp., Prismatoolithus sp., and Prismatoolithidae
indet.) and at least one ornithopod (Spheroolithus sp.). All eggshells
are relatively thin, and a new derived estimation method correlating
egg mass with eggshell thickness indicates that they are among the
smallest (28–135 g) theropod eggs known, likely laid by small bodied
forms. The eggshell assemblage from this locality suggests that a
diverse small dinosaur fauna, consisting primarily of theropods,
nested in the region, a diversity yet to be evidenced from skeletal
remains in Japan.