HOME
The Info List - Meganeura



--- Advertisement ---


(i) (i) (i) (i)

MEGANEURA is a genus of extinct insects from the Carboniferous
Carboniferous
period (approximately 300 million years ago), which resembled and are related to the present-day dragonflies . With wingspans ranging from 65 cm (25.6 in ) to over 70 cm (27.6 in ), M. monyi is one of the largest known flying insect species ; the Permian
Permian
Meganeuropsis permiana is another. Meganeura
Meganeura
were predatory , and fed on other insects.

Fossils were discovered in the French Stephanian Coal Measures of Commentry
Commentry
in 1880. In 1885, French paleontologist Charles Brongniart described and named the fossil "Meganeura" (large-nerved), which refers to the network of veins on the insect's wings . Another fine fossil specimen was found in 1979 at Bolsover in Derbyshire
Derbyshire
. The holotype is housed in the Muséum national d\'histoire naturelle , Paris
Paris
.

CONTENTS

* 1 Size * 2 References * 3 Bibliography * 4 External links

SIZE

There has been some controversy as to how insects of the Carboniferous
Carboniferous
period were able to grow so large.

* OXYGEN LEVELS AND ATMOSPHERIC DENSITY. The way oxygen 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 therefore they were not true giant insects, only being giant in comparison with their living relatives. * LACK OF PREDATORS. Other explanations for the large size of meganeurids compared to living relatives are warranted. Bechly (2004) suggested that the lack of aerial vertebrate predators allowed pterygote insects to evolve to maximum sizes during the Carboniferous and Permian
Permian
periods, perhaps accelerated by an evolutionary "arms race " for increase in body size between plant-feeding Palaeodictyoptera and Meganisoptera
Meganisoptera
as their predators. * AQUATIC LARVAE STADIUM. Another theory suggests that insects that developed in water before becoming terrestrial as adults grew bigger as a way to protect themselves against the high levels of oxygen.

REFERENCES

* ^ Rake 2017 , p. 20. * ^ Taylor & Lewis 2007 , p. 160. * ^ Gauthier Chapelle & Lloyd S. Peck (May 1999). "Polar gigantism dictated by oxygen availability". Nature . 399 (6732): 114–115. doi :10.1038/20099 . Oxygen
Oxygen
supply may also have led to insect gigantism in the Carboniferous
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. * ^ Westneat MW, Betz O, Blob RW, Fezzaa K, Cooper WJ, Lee WK (January 2003). "Tracheal respiration in insects visualized with synchrotron x-ray imaging". Science . 299 (5606): 558–560. PMID 12543973 . doi :10.1126/science.1078008 . 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. * ^ Robert Dudley (April 1998). "Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotion performance". The Journal of Experimental Biology . 201 (Pt8): 1043–1050. PMID 9510518 . 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
Carboniferous
atmosphere and were subsequently eliminated by a late Permian
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. * ^ Nel A.N., Fleck G., Garrouste R. and Gand, G. (2008): The Odonatoptera
Odonatoptera
of the Late Permian
Permian
Lodève Basin (Insecta). Journal of Iberian Geology 34(1): 115-122 PDF * ^ Bechly G. (2004): Evolution and systematics. pp. 7-16 in: Hutchins M., Evans A.V., Garrison R.W. and Schlager N. (eds): Grzimek's Animal
Animal
Life Encyclopedia. 2nd Edition. Volume 3, Insects. 472 pp. Gale Group, Farmington Hills, MI PDF * ^ Than, Ker (August 9, 2011). "Why Giant Bugs Once Roamed the Earth". National Geographic. Retrieved 20 July 2017.

BIBLIOGRAPHY

* Rake, Matthew (2017). Prehistoric Ancestors of Modern Animals. Hungry Tomato. p. 20. ISBN 1512436097 . * Taylor, Paul D.; Lewis, David N. (2007).