Protodonata
Encyclopedia
Meganisoptera is an extinct order
of very large to gigantic insects often called griffenflies. The order was formerly named Protodonata for their similar appearance and relation to dragonflies
. They range in Palaeozoic (Late Carboniferous
to Late Permian) insects, Most were only slightly larger than modern dragonflies and the order includes the largest known insect species such as the late Carboniferous Meganeura monyi
, Megatypus
, and the even larger early Permian Meganeuropsis permiana
, with wingspans of up to 71 centimetres (2.3 ft).
The fore and hind wings are similar in venation (a primitive feature) except for the larger anal (rearwards) area in the hind wing. The fore wing is usually more slender and slightly longer than the hind wing. Unlike the true dragonflies, they had no pterostigma
, and a somewhat simpler pattern of veins in the wings.
Most specimens are known from wing fragments only; with only a few as complete wings, and even fewer (of the family Meganeuridae) with body impressions. These show a globose head with large dentate mandibles, strong spiny legs, a large thorax, and long and slender dragonfly-like abdomen. Like true dragonflies, they were presumably predators.
A few nymph
s are also known, and show similar mouthparts
to those of modern dragonfly nymphs, suggesting that they were also active aquatic predators.
Although sometimes included under the dragonflies, the Protodonata lack certain distinctive wing features that characterise the Odonata. Grimaldi
and Engel
, pointing out that the colloquial term "giant dragonfly" is therefore misleading, suggest "griffinfly" instead.
is diffused
through the insect's body via its tracheal
breathing system puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed (Harlé & Harlé, 1911) that Meganeura was only able to fly because the atmosphere at that time contained more oxygen than the present 20%. This theory was dismissed by fellow scientists, but has found approval more recently through further study into the relationship between gigantism
and oxygen availability. If this theory is correct, these insects would have been susceptible to falling oxygen levels and certainly could not survive in our modern atmosphere. Other research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion". Recent analysis of the flight energetics of modern insects and birds suggests that both the oxygen levels and air density provide a bound on size.
A general problem with all oxygen related explanations of the giant dragonflies is the circumstance that very large Meganeuridae with a wing span of 45 cm also occurred in the Upper Permian of Lodève
in France, when the oxygen content of the atmosphere was already much lower than in the Carboniferous
and Lower Permian.
Bechly (2004) suggested that the lack of aerial vertebrate predators allowed pterygote insects to
evolve to maximum sizes during the Carboniferous and Permian periods, maybe accelerated by an evolutionary "arms race
" for increase in body size between plant-feeding Palaeodictyoptera
and meganeurids
as their predators.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of very large to gigantic insects often called griffenflies. The order was formerly named Protodonata for their similar appearance and relation to dragonflies
Odonata
Odonata is an order of insects, encompassing dragonflies and damselflies . The word dragonfly is also sometimes used to refer to all Odonata, but the back-formation odonate is a more correct English name for the group as a whole...
. They range in Palaeozoic (Late Carboniferous
Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
to Late Permian) insects, Most were only slightly larger than modern dragonflies and the order includes the largest known insect species such as the late Carboniferous Meganeura monyi
Meganeura
Meganeura is a genus of extinct insects from the Carboniferous period approximately 300 million years ago, which resembled and are related to the present-day dragonflies. With wingspans of more than 75 cm , M. monyi is one of the largest known flying insect species; the Permian Meganeuropsis...
, Megatypus
Megatypus
Megatypus is an extinct genus of insect. It looked like a dragonfly and was related to these creatures, but was much larger....
, and the even larger early Permian Meganeuropsis permiana
Meganeuropsis permiana
Meganeuropsis is an extinct genus of griffenfly, order Protodonata, known from the Early Permian of North America, and represents the biggest known insect of all times. The genus includes two described species:...
, with wingspans of up to 71 centimetres (2.3 ft).
The fore and hind wings are similar in venation (a primitive feature) except for the larger anal (rearwards) area in the hind wing. The fore wing is usually more slender and slightly longer than the hind wing. Unlike the true dragonflies, they had no pterostigma
Pterostigma
The pterostigma is a cell in the outer wing of insects which is often thickened or coloured and so stands out from other cells. It is particularly noticeable in dragonflies, but present also in other insect groups, such as snakeflies, hymenopterans and megalopterans.The purpose of the pterostigma,...
, and a somewhat simpler pattern of veins in the wings.
Most specimens are known from wing fragments only; with only a few as complete wings, and even fewer (of the family Meganeuridae) with body impressions. These show a globose head with large dentate mandibles, strong spiny legs, a large thorax, and long and slender dragonfly-like abdomen. Like true dragonflies, they were presumably predators.
A few nymph
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
s are also known, and show similar mouthparts
Insect mouthparts
Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
to those of modern dragonfly nymphs, suggesting that they were also active aquatic predators.
Although sometimes included under the dragonflies, the Protodonata lack certain distinctive wing features that characterise the Odonata. Grimaldi
David Grimaldi
David A. Grimaldi is an entomologist and Curator of Invertebrate Zoology at the American Museum of Natural History in New York. He received his graduate training at Cornell University, where he earned his doctorate in Entomology in 1986. Dr. Grimaldi is an authority in many fields of insect...
and Engel
Michael S. Engel
Michael S. Engel is an American paleontologist and entomologist. He has undertaken field work in Central Asia, Asia Minor, and the Western Hemisphere, and published more than 300 papers in scientific journals. He was trained at the University of Kansas where in 1993 he received a B.S. in Cellular...
, pointing out that the colloquial term "giant dragonfly" is therefore misleading, suggest "griffinfly" instead.
Size
Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way oxygenOxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
is diffused
Diffusion capacity
In biology, diffusion capacity is a measurement of the lung's ability to transfer gases. Oxygen uptake may be limited by diffusion in circumstances of low ambient oxygen or high pulmonary blood flow...
through the insect's body via its tracheal
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....
breathing system puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed (Harlé & Harlé, 1911) that Meganeura was only able to fly because the atmosphere at that time contained more oxygen than the present 20%. This theory was dismissed by fellow scientists, but has found approval more recently through further study into the relationship between gigantism
Gigantism
Gigantism, also known as giantism , is a condition characterized by excessive growth and height significantly above average...
and oxygen availability. If this theory is correct, these insects would have been susceptible to falling oxygen levels and certainly could not survive in our modern atmosphere. Other research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion". Recent analysis of the flight energetics of modern insects and birds suggests that both the oxygen levels and air density provide a bound on size.
A general problem with all oxygen related explanations of the giant dragonflies is the circumstance that very large Meganeuridae with a wing span of 45 cm also occurred in the Upper Permian of Lodève
Lodève
Lodève is a commune in the Hérault département in Languedoc-Roussillon in southern France. It is a sub-prefecture of the department.-Geography:...
in France, when the oxygen content of the atmosphere was already much lower than in the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
and Lower Permian.
Bechly (2004) suggested that the lack of aerial vertebrate predators allowed pterygote insects to
evolve to maximum sizes during the Carboniferous and Permian periods, maybe accelerated by an evolutionary "arms race
Arms race
The term arms race, in its original usage, describes a competition between two or more parties for the best armed forces. Each party competes to produce larger numbers of weapons, greater armies, or superior military technology in a technological escalation...
" for increase in body size between plant-feeding Palaeodictyoptera
Palaeodictyoptera
The Palaeodictyoptera are an extinct order of medium-sized to very large, primitive Palaeozoic paleopterous insects.-Overview:They were characterised by beak-like mouthparts, similarity between fore- and hind wings, and an additional pair of winglets on the prothorax, in front of the first pair of...
and meganeurids
Meganeura
Meganeura is a genus of extinct insects from the Carboniferous period approximately 300 million years ago, which resembled and are related to the present-day dragonflies. With wingspans of more than 75 cm , M. monyi is one of the largest known flying insect species; the Permian Meganeuropsis...
as their predators.
General references
- Carpenter, F. M.Frank M. CarpenterFrank M. Carpenter received his PhD from Harvard University, and was curator of fossil insects at the Harvard Museum of Comparative Zoology for 60 years. He studied the Permian fossil insects of Elmo, Kansas, and compared the North American fossil insect fauna with Paleozoic taxa known from...
1992. Superclass Hexapoda. Volume 3 of Part R, Arthropoda 4; Treatise on Invertebrate PaleontologyTreatise on Invertebrate PaleontologyThe Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
, Boulder, Colorado, Geological Society of AmericaGeological Society of AmericaThe Geological Society of America is a nonprofit organization dedicated to the advancement of the geosciences. The society was founded in New York in 1888 by Alexander Winchell, John J. Stevenson, Charles H. Hitchcock, John R. Proctor and Edward Orton and has been headquartered at 3300 Penrose...
. - Tasch, Paul, 1973, 1980 Paleobiology of the Invertebrates, John Wiley and Sons, p. 617
- André Nel, Günther Fleck, Romain Garrouste, Georges Gand, Jean Lapeyrie, Seth M Bybee, and Jakub Prokop (2009): Revision of Permo-Carboniferous griffenflies (Insecta: Odonatoptera: Meganisoptera) based upon new species and redescription of selected poorly known taxa from Eurasia. Palaeontographica Abteilung A, 289(4-6): 89–121.
External links
- Phylogenetic Systematics of Odonata by Günter Bechly, 2005