The name Palaeoptera (from Greek ( 'old') + ( 'wing')) has been traditionally applied to those ancestral groups of
winged insects (most of them extinct) that lacked the ability to fold the wings back over the
abdomen
The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...
as characterizes the
Neoptera. The
Diaphanopterodea, which are palaeopteran insects, had independently and uniquely
evolved a different wing-folding mechanism. Both
mayflies and
dragonflies
A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...
lack any of the smell centers in their brain found in
Neoptera.
Disputed status
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 indicates that Neoptera is a
monophyletic
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:
# the grouping contains its own most recent co ...
lineage. The
plesiomorph
In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral Phenotypic trait, character shared by all members of a clade, which does not distinguish the clade from other clades.
Plesiomorphy, symplesiomorph ...
ic absence of wing-folding does not necessarily mean the Palaeoptera form a natural group – they may be an assemblage containing all insects, closely related or not, that "are not Neoptera", an example of a
wastebasket taxon. If the extinct lineages are taken into account, it is 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
basal Pterygota, too. As it stands, the relationship of the two living Paleopteran groups –
Ephemeroptera (mayflies) and
Odonata (
dragonflies
A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...
and
damselflies) – to the Neoptera has not yet been resolved; there are three main competing 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 Palaeoptera appear to be
paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
.
[Maddison (2002), Trueman 008/ref>
]
See also
* Archedictyon
* Neoptera
Footnotes
References
* (2002): Tree of Life Web Project â€
Pterygota. Winged insects
Version of 2002-JAN-01. Retrieved 2008-DEC-15.
* 008 Tree of Life Web Project â€
Pterygote Higher Relationships
Retrieved 2008-DEC-15.
* (2008): Tree of Life Web Project â€
Odonata. Dragonflies and damselflies
Version of 2008-MAR-20. Retrieved 2008-DEC-15.
{{Taxonbar, from=Q927351
Insect taxonomy
Carboniferous first appearances
Pterygota
Paraphyletic groups