The Hexapoda Gap

Early insects did not produce a lot of fossils. There is a gap between 385 and 300 million years ago that is devoid of known fossils. The fossils that might have been produced during this period were likely small insects that are difficult to recognize. Few rock formations deposited during the period are exposed to the surface which means that few potential sites are available. During The Hexapoda Gap, insects diversified and evolved many new adaptations including the evolution of wings. Prior to the gap, the only insect fossils may be suggestive, but do not show wings. After the gap, we find fossils with fully developed complext wing structures. As a consequence, we are left to guess about the evolution of insect flight, when it happened and what type of insect first developed powered flight. If new fossils can be located from this period, they could have a profound effect on our model of insect evolution.

Nel and colleagues* review the fossils and produce this useful graphic in a publication in the journal, Nature*. This clearly demostrates the gap in fossils that leaves a gap in our knowledge.

Hexapoda Gap

Strudiella devonica Garrouste et al., 2012 (ref. 25) (1); wing of an archaeorthopteran, Prokop et al., 2005 (2); Westphalopsocus pumilio gen. et sp. nov. (3); Protoprosbole straeleni Laurentiaux, 1952 (4); Aviorrhyncha magnifica gen. et sp. nov. (5); Westphalothripides oudardi Nel et al., 2012 (ref. 15) (6); Avioxyela gallica gen. et sp. nov. (7); Metabolarva bella gen. et sp. nov. (8); Srokalarva berthei Kukalová-Peck, 1997 (9); Pteridotorichnos stipitopteri Labandeira and Phillips, 1996 (10); Westphalomerope maryvonneae Nel et al., 2007 (ref. 16) (11); undescribed Neuroptera of Obora (Czech Republic) (12); Stephanastus polinae gen. et sp. nov. (13); Coleopsis archaica Kirejtshuk et al., 2013 (ref. 22) (14). Bashk., Bashkirian; Gzh., Gzhelian; Kas., Kasimovian; Mosc., Moscovian; Serpukh., Serpukhovian.
Image From: Nature

* Nel, Andre; Roques, Patrick; Nel, Patricia; Prokin, Alexander A.; Bourgoin, Thierry; Prokop, Jakub; Szwedo, Jacek; Azar, Dany; Desutter-Grandcolas, Laure; Wappler, Torsten; Garrouste, Romain; Coty, David; Huang, Diying; Engel, Michael S.; Kirejtshuk, Alexander G. 2013. The earliest known holometabolous insects. Nature. 503: 257 261.

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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1 Response to The Hexapoda Gap

  1. Pingback: How Flight Evolved in Insects - Why Flies Can Bug You So Much - Darwin's Door

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