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{{Short description|Extinct order of dragonfly-like animals}}
{{Short description|Extinct order of dragonfly-like animals}}
{{Automatic taxobox
{{Automatic taxobox
| image = Meganeura.jpg
| image = Meganeurites_gracilipes_restoration.webp
| image_caption = Illustration of a ''[[Meganeura]]'' species
| image_caption = Reconstruction of ''[[Meganeurites]] gracilipes''
| fossil_range = {{fossilrange|318|251|[[Pennsylvanian (geology)|Pennsylvanian]]-[[Lopingian]]}}
| fossil_range = {{fossilrange|318|251|[[Pennsylvanian (geology)|Pennsylvanian]]-[[Lopingian]]}}
| taxon = Meganisoptera
| taxon = Meganisoptera
| authority = Martynov, 1932
| authority = Martynov, 1932
| subdivision_ranks = Families
| subdivision_ranks = Families
| subdivision =
| subdivision = * [[Aulertupidae]] <small>Zessin & Brauckmann 2010</small>
* [[Aulertupidae]] <small>Zessin & Brauckmann 2010</small>
* [[Kohlwaldiidae]] <small>Guthörl 1962</small>
* [[Kohlwaldiidae]] <small>Guthörl 1962</small>
* [[Meganeuridae]] <small>Handlirsch 1906</small>
* [[Meganeuridae]] <small>Handlirsch 1906</small>
* [[Namurotypidae]] <small>Bechly 1996</small>
* [[Namurotypidae]] <small>Bechly 1996</small>
* [[Paralogidae]] <small>Handlirsch 1906</small>
* [[Paralogidae]] <small>Handlirsch 1906</small>
⚫
| synonyms = *'''Protodonata''' <small>[[Charles Jules Edmée Brongniart|C. Brongniart]], 1893</small>
| synonyms =
⚫
*'''Protodonata''' <small>[[Charles Jules Edmée Brongniart|C. Brongniart]], 1893</small>
}}
}}


'''Meganisoptera''' is an [[extinct]] [[order (biology)|order]] of very large to gigantic insects, which may informally be called '''griffinflies'''. The order was formerly named '''Protodonata''', the "proto-Odonata", for their similar appearance and supposed relation to modern [[Odonata]] ([[damselflies]] and [[dragonflies]]). They range in [[Palaeozoic]] ([[Pennsylvanian (geology)|Late Carboniferous]] to [[Lopingian|Late Permian]]) times. Though most were only slightly larger than modern dragonflies, the order includes the largest known insect species, such as the late Carboniferous ''[[Meganeura|Meganeura monyi]]'', ''[[Megatypus]]'', and the even larger [[Cisuralian|early Permian]] ''[[Meganeuropsis permiana]]'', with wingspans of up to {{convert|71|cm|in}}.{{sfn|Grimaldi|Engel|2005|p=175}}
'''Meganisoptera''' is an [[extinct]] [[order (biology)|order]] of large dragonfly-like insects, informally known as '''griffenflies''' or (incorrectly) as '''giant dragonflies'''. The order was formerly named '''Protodonata''', the "proto-Odonata", for their similar appearance and supposed relation to modern [[Odonata]] ([[damselflies]] and [[dragonflies]]). They range in [[Palaeozoic]] ([[Pennsylvanian (geology)|Late Carboniferous]] to [[Lopingian|Late Permian]]) times. Though most were only slightly larger than modern dragonflies, the order includes the largest known insect species, such as the late Carboniferous ''[[Meganeura|Meganeura monyi]]'' and the even larger [[Cisuralian|early Permian]] ''[[Meganeuropsis permiana]]'', with wingspans of up to {{convert|71|cm|in}}.{{sfn|Grimaldi|Engel|2005|p=175}}

⚫
[[File:Meganeura monyi au Museum de Toulouse.jpg|thumb|left|The giant [[Upper Carboniferous]] dragonfly relative, ''[[Meganeura monyi]]'', attained a wingspan of about {{convert|680|mm|in}}.{{sfn|Tillyard|1917|p=324 |ps=: "No Dragonfly at present existing can compare with the immense ''Meganeura monyi'' of the Upper Carboniferous, whose expanse of wing was somewhere about twenty-seven inches."}}.]]


⚫
The forewings and hindwings are similar in venation (a primitive feature) except for the larger anal (rearwards) area in the hindwing. The forewing is usually slenderer and slightly longer than the hindwing. Unlike the true dragonflies, the [[Odonata]], they had no [[pterostigma]]ta, and had a somewhat simpler pattern of veins in the wings.
⚫
[[File:Meganeura monyi au Museum de Toulouse.jpg|thumb|left|The giant [[Upper Carboniferous]] dragonfly relative, ''[[Meganeura monyi]]'', attained a wingspan of about {{convert|680|mm|in}}.{{sfn|Tillyard|1917|p=324 |ps=: "No Dragonfly at present existing can compare with the immense Meganeura monyi of the Upper Carboniferous, whose expanse of wing was somewhere about twenty-seven inches."}} [[Muséum de Toulouse|Museum of Toulouse]].]]
⚫
The forewings and hindwings are similar in venation (a primitive feature) except for the larger anal (rearwards) area in the hindwing. The forewing is usually more slender and slightly longer than the hindwing. Unlike the true dragonflies, the [[Odonata]], 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 [[Mandible (insect mouthpart)|mandible]]s, strong spiny legs, a large thorax, and long and slender dragonfly-like abdomen. Like true dragonflies, they were presumably predators.
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 [[Mandible (insect mouthpart)|mandible]]s, strong spiny legs, a large thorax, and long and slender dragonfly-like abdomen. Like true dragonflies, they were presumably predators.
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A few [[nymph (biology)|nymph]]s are also known, and show [[insect mouthparts|mouthparts]] similar to those of modern dragonfly nymphs, suggesting that they were also active aquatic predators.{{sfn|Hoell|Doyen|Purcell|1998|page=321}}
A few [[nymph (biology)|nymph]]s are also known, and show [[insect mouthparts|mouthparts]] similar to those of modern dragonfly nymphs, suggesting that they were also active aquatic predators.{{sfn|Hoell|Doyen|Purcell|1998|page=321}}


Although sometimes included under the dragonflies, the Protodonata lack certain distinctive wing features that characterise the Odonata. {{harvnb|Grimaldi|Engel|2005}} point out that the colloquial term "giant dragonfly" is therefore misleading, and suggest "griffinfly" instead.
Although sometimes included under the dragonflies, the Meganisoptera lack certain distinctive wing features that characterise the Odonata. {{harvnb|Grimaldi|Engel|2005}} point out that the colloquial term "giant dragonfly" is therefore misleading, and suggest "griffenfly" instead.


== Size ==
== Size ==
[[File:Meganeuramodell.jpg|thumb|left|Model of a meganisopteran.{{efn|The model in this photograph incorrectly depicts pterostigma on the wings.}}]]
[[File:Meganeuramodell.jpg|thumb|left|Scale model of a meganisopteran.{{efn|The model in this photograph incorrectly depicts pterostigmata on the wings.}}]]
Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way [[oxygen]] is [[diffusion capacity|diffused]] through the insect's body via its [[Invertebrate trachea|tracheal]] breathing system (see [[Respiratory system of insects]]) puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed in {{harvtxt|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.{{sfn|Chapelle|Peck|1999|pages= 114–115|ps=: "Oxygen supply may also have led to insect gigantism in the Carboniferous period, because atmospheric oxygen was 30-35% (ref. 7). The demise of these insects when oxygen content fell indicates that large species may be susceptible to such change. Giant amphipods may therefore be among the first species to disappear if global temperatures are increased or global oxygen levels decline. Being close to the critical MPS limit may be seen as a specialization that makes giant species more prone to extinction over geological time."}} 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".{{sfn|Westneat|Betz|Blob|Fezzaa|2003|ps=: "Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects. Beetles, crickets, and ants exhibited rapid cycles of tracheal compression and expansion in the head and thorax. Body movements and hemolymph circulation cannot account for these cycles; therefore, our observations demonstrate a previously unknown mechanism of respiration in insects analogous to the inflation and deflation of vertebrate lungs."}} 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.{{sfn|Dudley |1998|ps=: "Uniformitarian approaches to the evolution of terrestrial locomotor physiology and animal flight performance have generally presupposed the constancy of atmospheric composition. Recent geophysical data as well as theoretical models suggest that, to the contrary, both oxygen and carbon dioxide concentrations have changed dramatically during defining periods of metazoan evolution. [[Hyperoxia]] in the late Paleozoic atmosphere may have physiologically enhanced the initial evolution of tetrapod locomotor energetics; a concurrently hyperdense atmosphere would have augmented aerodynamic force production in early flying insects. Multiple historical origins of vertebrate flight also correlate temporally with geological periods of increased oxygen concentration and atmospheric density. Arthropod as well as amphibian gigantism appear to have been facilitated by a hyperoxic Carboniferous atmosphere and were subsequently eliminated by a late Permian transition to hypoxia. For extant organisms, the transient, chronic and ontogenetic effects of exposure to hyperoxic gas mixtures are poorly understood relative to contemporary understanding of the physiology of oxygen deprivation. Experimentally, the biomechanical and physiological effects of hyperoxia on animal flight performance can be decoupled through the use of gas mixtures that vary in density and oxygen concentration. Such manipulations permit both paleophysiological simulation of ancestral locomotor performance and an analysis of maximal flight capacity in extant forms."}}
Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way [[oxygen]] is [[diffusion capacity|diffused]] through the insect's body via its [[Invertebrate trachea|tracheal]] breathing system (see [[Respiratory system of insects]]) puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed in {{harvtxt|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.{{sfn|Chapelle|Peck|1999|pages= 114–115|ps=: "Oxygen supply may also have led to insect gigantism in the Carboniferous period, because atmospheric oxygen was 30-35% (ref. 7). The demise of these insects when oxygen content fell indicates that large species may be susceptible to such change. Giant amphipods may therefore be among the first species to disappear if global temperatures are increased or global oxygen levels decline. Being close to the critical MPS limit may be seen as a specialization that makes giant species more prone to extinction over geological time."}} If this theory is correct, these insects would have been susceptible to falling oxygen levels and certainly could not survive in the modern atmosphere. Other research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion".{{sfn|Westneat|Betz|Blob|Fezzaa|2003|ps=: "Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects. Beetles, crickets, and ants exhibited rapid cycles of tracheal compression and expansion in the head and thorax. Body movements and hemolymph circulation cannot account for these cycles; therefore, our observations demonstrate a previously unknown mechanism of respiration in insects analogous to the inflation and deflation of vertebrate lungs."}} 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.{{sfn|Dudley |1998|ps=: "Uniformitarian approaches to the evolution of terrestrial locomotor physiology and animal flight performance have generally presupposed the constancy of atmospheric composition. Recent geophysical data as well as theoretical models suggest that, to the contrary, both oxygen and carbon dioxide concentrations have changed dramatically during defining periods of metazoan evolution. [[Hyperoxia]] in the late Paleozoic atmosphere may have physiologically enhanced the initial evolution of tetrapod locomotor energetics; a concurrently hyperdense atmosphere would have augmented aerodynamic force production in early flying insects. Multiple historical origins of vertebrate flight also correlate temporally with geological periods of increased oxygen concentration and atmospheric density. Arthropod as well as amphibian gigantism appear to have been facilitated by a hyperoxic Carboniferous atmosphere and were subsequently eliminated by a late Permian transition to hypoxia. For extant organisms, the transient, chronic and ontogenetic effects of exposure to hyperoxic gas mixtures are poorly understood relative to contemporary understanding of the physiology of oxygen deprivation. Experimentally, the biomechanical and physiological effects of hyperoxia on animal flight performance can be decoupled through the use of gas mixtures that vary in density and oxygen concentration. Such manipulations permit both paleophysiological simulation of ancestral locomotor performance and an analysis of maximal flight capacity in extant forms."}}


A general problem with all oxygen related explanations of giant griffinflies is the circumstance that very large Meganeuridae with a wingspan of 45&nbsp;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]].{{sfn|Nel|Fleck|Garrouste|Gand|2008}}
A general problem with all oxygen related explanations of giant griffenflies is the circumstance that very large Meganeuridae with a wingspan of 45&nbsp;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]].{{sfn|Nel|Fleck|Garrouste|Gand|2008}}


{{harvnb|Bechly|2004}} suggested that the lack of aerial vertebrate predators allowed [[Pterygota|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 [[Meganeura|meganeurids]] as their predators.
{{harvnb|Bechly|2004}} suggested that the lack of aerial vertebrate predators allowed [[Pterygota|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 [[Meganeura|meganeurids]] as their predators.
Line 57: Line 56:


==References==
==References==
{{Reflist|2| refs=
{{Reflist| refs=
<ref name=paleo>
<ref name=paleo>
{{Cite web| title=The Paleobiology Database, order Meganisoptera
{{Cite web| title=The Paleobiology Database, order Meganisoptera
Line 67: Line 66:
==Bibliography==
==Bibliography==
* {{cite encyclopedia |last=Bechly |first=G |year=2004 |title=Evolution and systematics |pages=7–16 |editor-last1=Hutchins |editor-first1=M. |editor-last2=Evans |editor-first2=A.V. |editor-last3=Garrison |editor-first3=R.W. |editor-last4=Schlager |editor-first4=N.|encyclopedia=Grzimek's Animal Life Encyclopedia | edition=2nd |volume=Insects |publisher=Gale |location=Farmington Hills, MI |url=https://bechly.lima-city.de/Grzimek.pdf |name-list-style=amp }}
* {{cite encyclopedia |last=Bechly |first=G |year=2004 |title=Evolution and systematics |pages=7–16 |editor-last1=Hutchins |editor-first1=M. |editor-last2=Evans |editor-first2=A.V. |editor-last3=Garrison |editor-first3=R.W. |editor-last4=Schlager |editor-first4=N.|encyclopedia=Grzimek's Animal Life Encyclopedia | edition=2nd |volume=Insects |publisher=Gale |location=Farmington Hills, MI |url=https://bechly.lima-city.de/Grzimek.pdf |name-list-style=amp }}
* {{cite encyclopedia |author-link1=Frank M. Carpenter |last1=Carpenter |first1=F. M. |date=1992 |title=Superclass Hexapoda |volume=Volume 3 of Part R, Arthropoda 4 |encyclopedia=[[Treatise on Invertebrate Paleontology]] |location=Boulder, CO |publisher=[[Geological Society of America]] }}
* {{cite encyclopedia |author-link1=Frank M. Carpenter |last1=Carpenter |first1=F. M. |date=1992 |title=Superclass Hexapoda |volume=3 of Part R, Arthropoda 4 |encyclopedia=[[Treatise on Invertebrate Paleontology]] |location=Boulder, CO |publisher=[[Geological Society of America]] }}
*{{cite journal |first1=Robert |last1=Dudley |date=April 1998 |title= Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotion performance |journal= [[The Journal of Experimental Biology]] |volume = 201 |pages= 1043–1050 |pmid= 9510518 |issue= Pt8 }}
*{{cite journal |first1=Robert |last1=Dudley |date=April 1998 |title= Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotion performance |journal= [[The Journal of Experimental Biology]] |volume = 201 |pages= 1043–1050 |pmid= 9510518 |issue= Pt8 |doi=10.1242/jeb.201.8.1043 }}
*{{cite journal |first1=Gauthier |last1=Chapelle |first2=Lloyd S. |last2=Peck |name-list-style=amp |date=May 1999 |title= Polar gigantism dictated by oxygen availability |journal= [[Nature (journal)|Nature]] |volume= 399 |doi= 10.1038/20099 |issue= 6732 |pages=114–115 }}
*{{cite journal |first1=Gauthier |last1=Chapelle |first2=Lloyd S. |last2=Peck |name-list-style=amp |date=May 1999 |title= Polar gigantism dictated by oxygen availability |journal= [[Nature (journal)|Nature]] |volume= 399 |doi= 10.1038/20099 |issue= 6732 |pages=114–115 |bibcode=1999Natur.399..114C |s2cid=4308425 }}
* {{cite book |author-link1=David Grimaldi (entomologist)|last1=Grimaldi |first1=David |author-link2=Michael S. Engel |last2=Engel |first2=Michael S. |title=Evolution of the Insects |date=2005-05-16 |publisher=[[Cambridge University Press]] |isbn=978-0-521-82149-0 |name-list-style=amp }}
* {{cite book |author-link1=David Grimaldi (entomologist)|last1=Grimaldi |first1=David |author-link2=Michael S. Engel |last2=Engel |first2=Michael S. |title=Evolution of the Insects |date=2005-05-16 |publisher=[[Cambridge University Press]] |isbn=978-0-521-82149-0 |name-list-style=amp }}
* {{cite journal |last=Harlé |first=Edouard |title=Le Vol de grands reptiles et insectes disparus semble indiquer une pression atmosphérique élevée |language=fr |year=1911 |journal=Extr. Du Bulletin de la Sté Géologique de France |volume=4 |number=9 |pages=118–121 }}
* {{cite journal |last=Harlé |first=Edouard |title=Le Vol de grands reptiles et insectes disparus semble indiquer une pression atmosphérique élevée |language=fr |year=1911 |journal=Extr. Du Bulletin de la Sté Géologique de France |volume=4 |number=9 |pages=118–121 }}
Line 75: Line 74:
* {{cite journal |first1=André |last1=Nel |first2=Günther |last2=Fleck |first3=Romain |last3=Garrouste |first4=Georges |last4=Gand |first5=Jean |last5=Lapeyrie |first6=Seth M |last6=Bybee |first7=Jakub |last7=Prokop |year=2009 |title=Revision of Permo-Carboniferous griffenflies (Insecta: Odonatoptera: Meganisoptera) based upon new species and redescription of selected poorly known taxa from Eurasia |journal=Palaeontographica Abteilung A |volume=289 |pages=89–121 |number=4–6 |name-list-style=amp |doi=10.1127/pala/289/2009/89}}
* {{cite journal |first1=André |last1=Nel |first2=Günther |last2=Fleck |first3=Romain |last3=Garrouste |first4=Georges |last4=Gand |first5=Jean |last5=Lapeyrie |first6=Seth M |last6=Bybee |first7=Jakub |last7=Prokop |year=2009 |title=Revision of Permo-Carboniferous griffenflies (Insecta: Odonatoptera: Meganisoptera) based upon new species and redescription of selected poorly known taxa from Eurasia |journal=Palaeontographica Abteilung A |volume=289 |pages=89–121 |number=4–6 |name-list-style=amp |doi=10.1127/pala/289/2009/89}}
*{{cite journal |first1=André |last1=Nel |first2=Günther |last2=Fleck |first3=Romain |last3=Garrouste |first4=Georges |last4=Gand |year=2008 |title=The Odonatoptera of the Late Permian Lodève Basin (Insecta) |journal=[[Journal of Iberian Geology]] |volume=34 |number=1 |pages=115–122 |url=https://revistas.ucm.es/index.php/JIGE/article/view/JIGE0808120115A/32759 |language=en |name-list-style=amp }}
*{{cite journal |first1=André |last1=Nel |first2=Günther |last2=Fleck |first3=Romain |last3=Garrouste |first4=Georges |last4=Gand |year=2008 |title=The Odonatoptera of the Late Permian Lodève Basin (Insecta) |journal=[[Journal of Iberian Geology]] |volume=34 |number=1 |pages=115–122 |url=https://revistas.ucm.es/index.php/JIGE/article/view/JIGE0808120115A/32759 |language=en |name-list-style=amp }}
* {{cite book |last1=Tasch |first1=Paul |orig-year=1973 |year=1980 |title=Paleobiology of the Invertebrates |publisher=John Wiley and Sons |p=617 }}
* {{cite book |last1=Tasch |first1=Paul |orig-year=1973 |year=1980 |title=Paleobiology of the Invertebrates |publisher=John Wiley and Sons |page=617 }}
*{{cite book |title=The Biology of Dragonflies |url=https://archive.org/details/biologyofdragonf00tilluoft |page=[https://archive.org/details/biologyofdragonf00tilluoft/page/324 324] |publisher=Cambridge University Press |last=Tillyard |first=R.J. |year=1917 |id=GGKEY:0Z7A1R071DD }}
*{{cite book |title=The Biology of Dragonflies |url=https://archive.org/details/biologyofdragonf00tilluoft |page=[https://archive.org/details/biologyofdragonf00tilluoft/page/324 324] |publisher=Cambridge University Press |last=Tillyard |first=R.J. |year=1917 |id=GGKEY:0Z7A1R071DD }}
*{{cite journal |last1=Westneat |first1=MW |last2=Betz |first2=O |last3=Blob |first3=RW |last4=Fezzaa |first4=K |last5=Cooper |first5=WJ |last6=Lee |first6=WK |date=January 2003 |title= Tracheal respiration in insects visualized with synchrotron x-ray imaging |journal= [[Science (journal)|Science]] |volume = 299 |pages= 558–560 |doi= 10.1126/science.1078008 |pmid= 12543973 |issue= 5606 |name-list-style=amp }}
*{{cite journal |last1=Westneat |first1=MW |last2=Betz |first2=O |last3=Blob |first3=RW |last4=Fezzaa |first4=K |last5=Cooper |first5=WJ |last6=Lee |first6=WK |date=January 2003 |title= Tracheal respiration in insects visualized with synchrotron x-ray imaging |journal= [[Science (journal)|Science]] |volume = 299 |pages= 558–560 |doi= 10.1126/science.1078008 |pmid= 12543973 |issue= 5606 |bibcode=2003Sci...299..558W |s2cid=43634044 |name-list-style=amp }}


==External links==
==External links==
{{Wikispecies|Protodonata}}
{{Wikispecies|Meganisoptera}}
* [http://palaeos.com/metazoa/arthropoda/odonatoptera/meganisoptera.html Phylogenetic Systematics of Odonata]
* [http://palaeos.com/metazoa/arthropoda/odonatoptera/meganisoptera.html Phylogenetic Systematics of Odonata]


{{Orders of Insects|extinct}}
{{Orders of Insects|extinct}}
{{Taxonbar|from=Q164689}}
{{Taxonbar|from1=Q164689|from2=Q56479261}}


[[Category:Meganisoptera| ]]
[[Category:Meganisoptera| ]]
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[[Category:Lopingian extinctions]]
[[Category:Lopingian extinctions]]
[[Category:Extinct insect orders]]
[[Category:Extinct insect orders]]
[[Category:Odonatoptera]]

Latest revision as of 17:56, 6 August 2024

Meganisoptera
Temporal range: Pennsylvanian-Lopingian
Reconstruction of Meganeurites gracilipes
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Superorder: Odonatoptera
Order: †Meganisoptera
Martynov, 1932
Families
Synonyms

Meganisoptera is an extinct order of large dragonfly-like insects, informally known as griffenflies or (incorrectly) as giant dragonflies. The order was formerly named Protodonata, the "proto-Odonata", for their similar appearance and supposed relation to modern Odonata (damselflies and dragonflies). They range in Palaeozoic (Late Carboniferous to Late Permian) times. Though most were only slightly larger than modern dragonflies, the order includes the largest known insect species, such as the late Carboniferous Meganeura monyi and the even larger early Permian Meganeuropsis permiana, with wingspans of up to 71 centimetres (28 in).[1]

The giant Upper Carboniferous dragonfly relative, Meganeura monyi, attained a wingspan of about 680 millimetres (27 in).[2].

The forewings and hindwings are similar in venation (a primitive feature) except for the larger anal (rearwards) area in the hindwing. The forewing is usually slenderer and slightly longer than the hindwing. Unlike the true dragonflies, the Odonata, they had no pterostigmata, and had 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 nymphs are also known, and show mouthparts similar to those of modern dragonfly nymphs, suggesting that they were also active aquatic predators.[3]

Although sometimes included under the dragonflies, the Meganisoptera lack certain distinctive wing features that characterise the Odonata. Grimaldi & Engel 2005 point out that the colloquial term "giant dragonfly" is therefore misleading, and suggest "griffenfly" instead.

Size

[edit]
Scale model of a meganisopteran.[a]

Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way oxygen is diffused through the insect's body via its tracheal breathing system (see Respiratory system of insects) puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed in 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.[4] If this theory is correct, these insects would have been susceptible to falling oxygen levels and certainly could not survive in the modern atmosphere. Other research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion".[5] 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.[6]

A general problem with all oxygen related explanations of giant griffenflies is the circumstance that very large Meganeuridae with a wingspan 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.[7]

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.

Families and genera

[edit]

These families belong to the order Meganisoptera:[8]

These genera belong to the order Meganisoptera, but have not been placed in families:[8]

Notes

[edit]
  1. ^ The model in this photograph incorrectly depicts pterostigmata on the wings.

References

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  1. ^ Grimaldi & Engel 2005, p. 175.
  2. ^ Tillyard 1917, p. 324: "No Dragonfly at present existing can compare with the immense Meganeura monyi of the Upper Carboniferous, whose expanse of wing was somewhere about twenty-seven inches."
  3. ^ Hoell, Doyen & Purcell 1998, p. 321.
  4. ^ Chapelle & Peck 1999, pp. 114–115: "Oxygen supply may also have led to insect gigantism in the Carboniferous period, because atmospheric oxygen was 30-35% (ref. 7). The demise of these insects when oxygen content fell indicates that large species may be susceptible to such change. Giant amphipods may therefore be among the first species to disappear if global temperatures are increased or global oxygen levels decline. Being close to the critical MPS limit may be seen as a specialization that makes giant species more prone to extinction over geological time."
  5. ^ Westneat et al. 2003: "Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects. Beetles, crickets, and ants exhibited rapid cycles of tracheal compression and expansion in the head and thorax. Body movements and hemolymph circulation cannot account for these cycles; therefore, our observations demonstrate a previously unknown mechanism of respiration in insects analogous to the inflation and deflation of vertebrate lungs."
  6. ^ Dudley 1998: "Uniformitarian approaches to the evolution of terrestrial locomotor physiology and animal flight performance have generally presupposed the constancy of atmospheric composition. Recent geophysical data as well as theoretical models suggest that, to the contrary, both oxygen and carbon dioxide concentrations have changed dramatically during defining periods of metazoan evolution. Hyperoxia in the late Paleozoic atmosphere may have physiologically enhanced the initial evolution of tetrapod locomotor energetics; a concurrently hyperdense atmosphere would have augmented aerodynamic force production in early flying insects. Multiple historical origins of vertebrate flight also correlate temporally with geological periods of increased oxygen concentration and atmospheric density. Arthropod as well as amphibian gigantism appear to have been facilitated by a hyperoxic Carboniferous atmosphere and were subsequently eliminated by a late Permian transition to hypoxia. For extant organisms, the transient, chronic and ontogenetic effects of exposure to hyperoxic gas mixtures are poorly understood relative to contemporary understanding of the physiology of oxygen deprivation. Experimentally, the biomechanical and physiological effects of hyperoxia on animal flight performance can be decoupled through the use of gas mixtures that vary in density and oxygen concentration. Such manipulations permit both paleophysiological simulation of ancestral locomotor performance and an analysis of maximal flight capacity in extant forms."
  7. ^ Nel et al. 2008.
  8. ^ a b "The Paleobiology Database, order Meganisoptera". Retrieved 2019-10-17.

Bibliography

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