Palaeoptera Fossil range: Carboniferous - Recent
The Green Drake (Ephemera danica), a mayfly (Ephemeroptera: Ephemeridae)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Hexapoda
Class:	Insecta
Subclass:	Pterygota
Infraclass:	Palaeoptera (disputed) Martynov, 1923
Superorders
Ephemeropteroidea Odonatoptera[1] Palaeodictyopteroidea (extinct; disputed)

The name Palaeoptera has been traditionally applied to those primitive groups of winged insects (most of them extinct) that lacked the ability to fold the wings back over the abdomen as characterizes the Neoptera. While this may not sound like a fundamental distinction, the complexities of the wing-folding mechanism, as well as the mechanical operation of the wings in flight (indirect flight muscles), are such that it clearly indicates the Neoptera are a monophyletic lineage. The Diaphanopterodea, which are palaeopteran insects, had independently and uniquely evolved a different wing-folding mechanism.

The problem is that the plesiomorphic absence of wing-folding does not necessarily mean the Palaeoptera form a natural group – they may simply be an assemblage containing all insects, closely related or not, that "are not Neoptera". As it stands, the relationship of the two living Paleopteran groups – Ephemeroptera (mayflies) and Odonata (dragonflies and damselflies) – to the Neoptera has not been resolved yet; there are three competing main hypotheses with many variations. In two of these – those that treat the ephemeropteran or the odonatan lineage as closer to the Neoptera than to the other "palaeopterans" –, the Paleoptera appear to be paraphyletic and thus an artificial grouping that is best abandoned.^[2]

If the extinct lineages are taken into account, it seems likely that the concept of Palaeoptera will eventually be discarded or changed in content to more accurately reflect insect evolution. In any case, three main palaeopteran lineages, traditionally treated as superorders, are recognized. Of these, the Palaeodictyopteroidea themselves might be a paraphyletic assemblage of very basal Pterygota, too.

[edit] See also

• Archedictyon

[edit] Footnotes

[edit] References

• Maddison, David R. (2002): Tree of Life Web Project – Pterygota. Winged insects. Version of 2002-JAN-01. Retrieved 2008-DEC-15.
• Trueman, John W.H. [2008]: Tree of Life Web Project – Pterygote Higher Relationships. Retrieved 2008-DEC-15.
• Trueman, John W.H. & Rowe, Richard J. (2008): Tree of Life Web Project – Odonata. Dragonflies and damselflies. Version of 2008-MAR-20. Retrieved 2008-DEC-15.