[B-PT06] Phanerozoic biodiversity change: Extinction and diversification

[BPT06-01] Do we have any evidence of the existence of bilaterian animals in the Ediacaran? New trace fossil data from the Ediacaran of western Mongolia

*Tatsuo Oji¹, Stephen Dornbos², Keigo Yada³, Hitoshi Hasegawa¹, Sersmaa Gonchigdorj^5,4, Takafumi Mochizuki⁵ (1.Nagoya University Museum, Nagoya University, 2.University of Wisconsin-Milwaukee, 3.Graduate School of Environmental Sciences, Nagoya University, 4.Mongolian University of Science and Technology, 5.Iwate Prefectural Museum)

Keywords:Ediacaran, bilaterians, Mongolia

Although a lot of arguments exist as to the existance or absence of bilaterians in the Ediacaran, no conclusive evidence has so far been obtained. There are a variety of trace fossils from the Ediacaran, but no deeply penetrative, or U-shape burrows have been discovered. Therefore, these Ediacaran traces should be made by protozoans or cnidarians. We found vertically penetrative burrows, presumably assigned to Arenicolites, from multiple horizons of the upper Ediacaran of western Mongoliia. These presumably have U-shape form, and the animal that lived in the burrow should have longitudinally elongate form, probably assignable to bilaterian animals. Mongolia was located in low-lattitudinal area in the late Ediacaran, and animal evolution is thus thought to have proceeded earlier than other areas.