A Cretaceous Chafer Beetle (Coleoptera: Scarabaeidae) with Exaggerated Hind Legs-Insight from Comparative Functional Morphology into a Possible Spring Movement

Yuanyuan Lu; Dirk Ahrens; Chungkun Shih; Josh Jenkins Shaw; Xingke Yang; Dong Ren; Ming Bai

doi:10.3390/biology12020237

A Cretaceous Chafer Beetle (Coleoptera: Scarabaeidae) with Exaggerated Hind Legs-Insight from Comparative Functional Morphology into a Possible Spring Movement

Biology (Basel). 2023 Feb 2;12(2):237. doi: 10.3390/biology12020237.

Authors

Yuanyuan Lu¹, Dirk Ahrens², Chungkun Shih^{3

4}, Josh Jenkins Shaw^{1

5}, Xingke Yang¹, Dong Ren³, Ming Bai^{1

6

7

8

9}

Affiliations

¹ Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
² Zoologisches Forschungsmuseum A. Koenig, Adenauerallee 127, 53113 Bonn, Germany.
³ College of Life Sciences and Academy for Multidisciplinary Studies, Capital Normal University, Beijing 100048, China.
⁴ Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA.
⁵ Natural History Museum of Denmark, Zoological Museum, Universitetsparken 15, 2100 Copenhagen, Denmark.
⁶ College of Plant Protection, Hebei Agricultural University, Baoding 071001, China.
⁷ School of Agriculture, Ningxia University, Yinchuan 750021, China.
⁸ Northeast Asia Biodiversity Research Center, Northeast Forestry University, Harbin 150040, China.
⁹ University of Chinese Academy of Sciences, Beijing 100049, China.

Abstract

The phenomenon of exaggerated morphological structures has fascinated people for centuries. Beetles of the family Scarabaeidae show many very diverse exaggerated characters, for example, a variety of horns, enlarged mandibles or elongated antennal lamellae. Here, we report a new Mesozoic scarab, Antiqusolidus maculatus gen. et sp. n. from the Lower Cretaceous Yixian Formation (~125 Ma), which has unusually robust and structured hind legs with greatly enlarged spurs and a unique elongated apical process. Based on simulations and finite element analyses, the function of these structures is hypothesized to support springing to aid movement and fighting. Based on available morphological characters, we performed phylogenetic analyses (maximum parsimony) of the main subfamilies and families of Scarabaeoidea. The results support the placement of Antiqusolidus gen. n. as a sister group of Rutelinae within the phytophagous lineage of pleurostict Scarabaeidae. Furthermore, the unusual delicate color marking patterns in the fossil specimens suggest that the new species might have been diurnal and potentially visited the leaves or flowers of Early Cretaceous plants. This morphological and functional study on this extinct scarab species provides new sights into exaggerated structures in Mesozoic insects.

Keywords: Cretaceous fossil; exaggerated hind legs; fighting; phytophagous; scarab beetles; springing.

Grants and funding

This research was funded by the National Key R&D Program of China (No. 2022YFC2601200), National Natural Science Foundation of China (Nos. 31900317, 32270468, 42288201 and 32020103006), the National Science & Technology Fundamental Resources Investigation Program (Grant Nos. 2022FY202100, 2022FY100500, 2019FY100400, 2019FY101800); the project of the Northeast Asia Biodiversity Research Center (NABRI202203); the Bureau of International Cooperation, Chinese Academy of Sciences; Guizhou Science and Technology Planning Project (General support-2022-173). We thank the Beijing Synchrotron Radiation Facility (BSRF) and Shanghai Synchrotron Radiation Facility (SSRF) for beam time and staff 4W1A and 4W1B of the BSRF and staff BL13HB of the SSRF for analytical assistance. J.J.S. was funded by the Chinese Academy of Sciences President’s International Fellowship Initiative for Postdoctoral Fellows, Grant No. 2019PB0090.