New Early Cretaceous dinosaurian eggshell Multifissoolithus shimonosekiensis (Dinosauria, Dongyangoolithidae) from the Lower Cretaceous of Shimonoseki, Yamaguchi, Southwestern Japan

Dinosaur eggshells from Japan provide vital information about the relatively uncommon Early Cretaceous dinosaur eggs in Asia. Here, we describe a new Early Cretaceous dinosaur eggshell, Multifissoolithus shimonosekiensis from Shimonoseki, Yamaguchi, southwestern Japan. The specimen was collected in 1965 from the Aptian-Albian Shimonoseki Subgroup and range in diameter approximately from 1 to 7 cm and in thickness from 3.4 to 4.7 mm. The external surface exhibits roughly parallel clefts diagnostic to the dongyangoolithid Multifissoolithus. Computed tomography images reveal complex internal cavities. Subcircular pore canals extend from the cavities. In radial thin section, the eggshell microstructure resembles prolatocanaliculate pore system with dendrospherulitic morphotype typical of the Dendroolithidae. Similar eggs are reported from Zhejiang, southern China and Gyeonggi, western South Korea, while M. shimonosekiensis differs from them in greater thickness and more extensively developed internal cavities. Microstructural similarity among the Dongyangoolithidae, Dendroolithidae, and Spheroolithidae may indicate their phylogenetically close relationship and deserves further studies. These eggs and M. shimonosekiensis commonly occur in the Aptian-Albian deposits and provide evidence for a shared oofauna in these regions. These eggs were likely laid by closely related dinosaur taxa and future exploration for the skeletal remains of such dinosaurs in the regions is desirable.http://www.zoobank.org/urn:lsid:zoobank.org:pub:910B2029-9B98-4C33-BFC9-FD25AA09FE40