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Episodes 2020; 43(4): 1045-1052

Published online December 1, 2020

https://doi.org/10.18814/epiiugs/2020/020069

Copyright © International Union of Geological Sciences.

New evidence for truly gregarious behavior of ornithopods and solitary hunting by a theropod

by In Sung Paik1*, Hyun Joo Kim1, Seung Gyun Baek2, and Young Kyo Seo2

1Department of Earth and Environmental Sciences, Pukyong National University, 48513 Busan, Republic of Korea
2Gematek Co. Ltd. Busan 48071, Republic of Korea

Correspondence to:*E-mail: paikis@pknu.ac.kr

Received: April 7, 2020; Revised: June 11, 2020; Accepted: June 11, 2020

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Multiple subparallel dinosaur trackways closely associated with a solitary theropod trackway occur in the Late Cretaceous deposits at Yugok-dong in Ulsan City, Korea. The trackway-bearing deposits are sheetflood deposits and are well-lithified to preserve the footprints. The paleoenvironment of trackway deposits is interpreted as a lake margin where microbial mats formed under semi-arid paleoclimatic conditions. The unique features of these dinosaur trackways are 1) preservation of transformed skin impressions in every footprint of multiple trackways indicating nearly simultaneous trackway formation, 2) occurrence of multiple trackways representing three kinds of ornithopods, and 3) close association of a theropod trackway with the ornithopod trackway. This study reports the another discovery to support the gregarious travelling of ornithopod dinosaurs and solitary hunting of theropods for herbivorous dinosaurs by the occurrence of simultaneously formed multiple trackways of ornithopods and one theropod trackway. This tracksite is very exceptional not only in preserving skin impressions in every footprint of six subparallel trackways but also in providing new evidence to support that different kinds of herbivorous dinosaurs moved together in the same direction to form a group. In addition, this tracksite suggests that solitary hunting was also present in non-avian dinosaurs as in modern tigers or leopards.