A. Nel ,..., A. Prokin,..., Рђ. Kirejtshuk . 2013. The earliest-known holometabolous insects.
Nel A., Roques P., Nel P., Prokin A.A., Bourgoin T., Prokop J., Szwedo J., Azar D., Desutter-Grandcolas L., Wappler T., Garrouste R., Coty D., Huang D., Engel M.S., Kirejtshuk A.G. 2013.
The earliest-known holometabolous insects.
Nature, Research Letters, doi:10.1038/nature12629, 15 pp.
+ Supplementary Information, 14 pp.
This paper is available online on the electronic version of the journal:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12629.html
Abstract.
The Eumetabola (Endopterygota (also known as Holometabola) plus Paraneoptera)
have the highest number of species of any clade, and greatly contribute to
animal species biodiversity. The palaeoecological circumstances that favoured
their emergence and success remain an intriguing question. Recent molecular
phylogenetic analyses have suggested a wide range of dates for the initial
appearance of the Holometabola, from the Middle Devonian epoch (391 million
years (Myr) ago) to the Late Pennsylvanian epoch (311 Myr ago), and Hemiptera
(310 Myr ago). Palaeoenvironments greatly changed over these periods,
with global cooling andincreasing complexity of green forests. The
Pennsylvanian-period crown-eumetabolan fossil record remains notably
incomplete, particularly as several fossils have been erroneously
considered tobe stem Holometabola (Supplementary Information);
the earliest definitive beetles are from the start of the Permian period.
The emergence of the hymenopterids, sister group to other Holometabola, is
dated between 350 and 309 Myr ago, incongruentwith their current earliest
record (Middle Triassic epoch). Here we describe five fossils
a Gzhelian-age stem coleopterid, a holometabolous larva of uncertain ordinal
affinity, a stem hymenopterid, and early Hemiptera and Psocodea, all from the
Moscovian age and reveal a notable penecontemporaneous breadth of early
eumetabolan insects. These discoveries are more congruent with current
hypotheses of clade divergence. Eumetabola experienced episodes of
diversification during the Bashkirian-Moscovian and the Kasimovian-Gzhelian
ages. This cladogenetic activity is perhaps related to notable episodes of
drying resulting from glaciations, leading to the eventual demise in
Euramerica of coal-swamp ecosystems, evidenced by floral turnover during
this interval. These ancient species were of very small size, living in
the shadow of Palaeozoic-era "giant" insects. Although these discoveries
reveal unexpected Pennsylvanian eumetabolan diversity, the lineage radiated
more successfully only after the mass extinctions at the end of the Permian
period, giving rise to the familiar crown groups of their respective clades.