Atypical ‘long-tailed’ cockroaches arose during Cretaceous in response to angiosperm terrestrial revolution

PeerJ

article

Xin-Ran Li¹  Di-Ying Huang¹ 

[1] State Key Laboratory of Palaeobiology and Stratigraphy, Center for Excellence in Life and Paleoenvironment, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences

关键词: Amber;    Angiosperm;    Dictyoptera;    Eoblattodea;    Fossil;    Holopandictyoptera;    Ovipositor;    Roachoids;   

DOI  :  10.7717/peerj.15067

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Typical cockroaches are flat, broad, with large pronotum and wings covering the body. This conserved morphotype dates back to the Carboniferous, during which the ancestral cockroaches, or roachoids, originated. On the other hand, the ovipositor of cockroaches gradually reduced during the Mesozoic, coupled with a major shift of reproductive strategy. By the Cretaceous, long external ovipositors became rare, most cockroaches used very short or even hidden internal ovipositors to fabricate egg cases (oothecae), which is an innovation for egg protection. Here, we describe two cockroaches from mid-Cretaceous Myanmar amber: Ensiferoblatta oecanthoides gen. et sp. nov. (Ensiferoblattidae fam. nov.) and Proceroblatta colossea gen. et sp. nov. They are slim, elongate, fusiform, with longitudinal pronotum, and have long external ovipositors. The combination of these traits represents a unique morphotype, which resembles crickets and katydids (Ensifera) more than general cockroaches. Ensiferoblatta and Proceroblatta may be arboreal, feeding on and/or laying eggs into certain angiosperms that newly emerged. Their open habit causes latent impairment to viability, and may contribute to their extinction. These new taxa are the youngest members of the ancient, extinct group of cockroaches, namely Eoblattodea, which are characterized by long ovipositors. We speculate that the extinction of certain gymnosperm hosts almost ended the 200-My triumph of Eoblattodea. Despite an attempt to adapt to angiosperm hosts, Ensiferoblatta, Proceroblatta and suchlike cockroaches as an evolutionary dead end failed to save Eoblattodea from extinction. The lack of protection for eggs (maternal care in particular) might accelerate the extinction of Eoblattodea as a whole.

【 授权许可】

CC BY