Mickoleitiidae
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Coxoplectoptera or "chimera wings" is an extinct
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
of stem-group mayflies containing one family, Mickoleitiidae. Two adult and more than 20 nymphal fossils of ''Mickoleitia'' have been scientifically described from Mesozoic outcrops, mainly from the Lower Cretaceous Crato Formation of Brazil (in total, around 40 fossil nymphs have been found). Both the winged adults and the aquatic nymphs were predators with raptorial forelegs, which are reminiscent to those of
praying mantids Mantidae is one of the largest families in the order of praying mantises, based on the type species ''Mantis religiosa''; however, most genera are tropical or subtropical. Historically, this was the only family in the order, and many references ...
. The nymphs had a peculiar
freshwater shrimp Freshwater shrimp are any shrimp which live in fresh water. This includes: *Any Caridea (shrimp) which live in fresh water, especially the family Atyidae *Species in the genus ''Macrobrachium'' :*'' Macrobrachium ohione'', the Ohio River shrimp : ...
-like habitus.


Etymology

The genus ''Mickoleitia'' and family Mickoleitiidae was named in honor of German zoologist Gerhard Mickoleit from the University of Tübingen, who was among the first proponents of Willi Hennig's " Phylogenetic Systematics". The scientific name of the order Coxoplectoptera refers to the prolonged coxal segment of the nymphal and adult legs, and the old scientific name Plectoptera for mayflies (not to be confused with
Plecoptera Plecoptera is an order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the mo ...
for stoneflies). The common name "chimera wings" was coined in reference to the strange combination of characters in the morphology of the adult animal, which looks like a kind of chimera built from unrelated insects, with their oblique thorax and broad hind wing shape like a dragonfly, their wing venation like a primitive mayfly ancestor, and their raptorial forelegs like a mantis.


History of discovery

The fossil nymphs of the genus ''Mickoleitia'' are not especially rare in the limestones of the Crato Formation; the local brick workers even have a common Brazilian name for them ("Abacaxi" = pineapple). These nymphs were scientifically discovered and first mentioned by Bechly (2001: fig. 36), who also pointed to their strange morphology. Staniczek (2002, 2003) discussed the larvae as well and claimed that they arguably had been a kind of living fossil in the Lower Cretaceous. The German biologist
Rainer Willmann Rainer may refer to: People * Rainer (surname) * Rainer (given name) Other * Rainer Island, an island in Franz Josef Land, Russia * 16802 Rainer, an asteroid * Rainer Foundation, British charitable organisation See also

* Rainier (disambigua ...
described the nymphs in a chapter in Martill, Bechly & Loveridge (2007) and erroneously attributed them to the extinct stem group mayfly family Cretereismatidae that he described based on adult specimens from the same locality. During the work for this monograph on the Crato Formation the German palaeoentomologist Günter Bechly and entomologist Arnold H. Staniczek discovered in the fossil collection of the Stuttgart State Museum of Natural History the very adult specimen that later would become the holotype of ''Mickoleitia longimanus''. They figured this fossil in Martill, Bechly & Loveridge 2007 (Fig. 11.90i,j) as undescribed stem group mayfly and indicated in a brief figure legend the possible relationship to the erratic nymphs. The detailed scientific description of Coxoplectoptera and the demonstration of the relationship of fossil adult and nymphs was finally published by Staniczek, Bechly & Godunko (2011) in a special issue on Cretaceous insects of the journal "Insect Systematics & Evolution". The authors also determined that two fossil nymphs (''Mesogenesia petersae'' = ''Archaeobehnigia edmundsi'') that had been erroneously described by Tshernova (1977) as modern mayfly nymphs from the Middle or
Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...
of Transbaikals, can be attributed the order Coxoplectoptera. The discovery of Coxoplectoptera represented one of the more spectacular findings of paleontology in 2011 and was heavily covered by news media around the globe.


Description


Adult

The adult stage of the type species ''Mickoleitia longimanus'' had a wing length of 28–29 mm and a probable body length of ca. 35–40 mm (the abdomen is not preserved in the single known fossil holotype specimen). A second unnamed species of the genus ''Mickoleitia'' was only of half this size, and is only known by a single adult specimen from a private fossil collection in
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
. The head of ''Mickoleitia'' was provided with large compound eyes and functional
mouthparts Mouthparts may refer to: * The parts of a mouth ** Arthropod mouthparts *** Insect mouthparts {{disambig ...
(preserved are 3-segmented labial palps). The thoracic segments are obliquely tilted backwards as in dragonflies, so that the raptorial forelegs are shifted forwards. All legs have a strongly prolonged and free coxal segment. The forelegs are developed as subchelate raptorial devices with a single-segmented tarsus with an unpaired claw. Most likely the abdomen was provided with three caudal filaments (two lateral cerci and the median epiproct) as in modern mayflies and their Permian stem group representatives ( Permoplectoptera, e.g. Protereismatidae). Since males of modern mayflies and of Permoplectoptera have gonopods on the 9th abdominal segment that are developed as genital claspers to grip the female for copulation, such a character state and behavior is also likely for Coxoplectoptera, who have an intermediate position as phylogenetic link between these two groups.


Nymph

The more than 20 described nymphs of different stages have a body length of . Their laterally compressed body is unique among all known fossil and Recent
aquatic insect Aquatic insects or water insects live some portion of their life cycle in the water. They feed in the same ways as other insects. Some ''diving'' insects, such as predatory diving beetles, can hunt for food underwater where land-living insects c ...
nymphs, and rather resembles the body of gammarid freshwater shrimps. Many of the fossil nymphs are preserved in a characteristic posture with arched back, erect antennae and terminal filaments, and forelegs always in catching position similar to a praying mantis. The head was strongly armored and provided with horn- or shovel-like projections. Of the mouthparts only the crossed, sabre-like mandibles and the spoon-shaped labium are known. All legs have a strongly prolonged and free coxal segment as in the adult. Likewise, the forelegs are developed as slender subchelate raptorial legs with nearly identical segment proportions as in the adult stage, but with a shorter tibia that may have been fused with the single-segmented tarsus, which ended in an unpaired claw. Styliform and ventrally directed abdominal gills are developed on abdominal segments 1-7. These gills are composed of a broader, more strongly sclerotized basal part and a slender and rather membranous distal part. The gills articulate dorsally within the abdominal tergites that are distinctly separated from the ventral sternites. The caudal filaments are formed by the two lateral cerci and the slightly longer medial terminal filament. All three appendages are lined with dense rows of long and thin setae.


Ecology and behavior


Adult

Because in the adult holotype specimen well-preserved mouthparts (palps) are visible, the adult animals almost certainly were able to feed. In direct contrast, the adult form of modern mayflies has dramatically reduced, non-functional mouthparts, and lives solely to reproduce. The raptorial forelegs and oblique thorax indicate that ''Mickoleitia'' was a predator. The large and broad hinds suggest that they were ecologically similar to dragonflies, in that they were swift, flying predators of other flying insects.


Nymph

The abundance of fossils, the circumstances of preservation and special anatomical
adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...
s (7 pairs of abdominal gills, 3 caudal filaments with dense rows of swimming hairs) prove that the larvae have been living in freshwater of streams and rivers, just like those of modern mayflies. They were washed in as
allochthon upright=1.6, Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a nappe. If an erosional hole is created in the nappe that is called a window (geology)">window. A klippe is a solitary out ...
ous elements into the brackish Crato lagoon, were the limestones were deposited. The raptorial forelegs, sabre-like mandibles, large eyes and long antennae indicate that the nymphs were predators like the adults. On the other hand, the strong, shortened and broadened mid- and hind legs, the strong body armature, and shovel-like projections on the head all suggest that the animals were burrowing. Staniczek, Bechly & Godunko (2011) therefore assumed that the nymphs were ambush predators that were hiding, partly burrowed in the river bed, and waiting for small prey passing by.


Evolution and phylogeny

The nymphs of Coxoplectoptera provided new clues to the disputed question of the evolutionary origin of insect wings. Before this discovery the paranotal-hypothesis and the leg-exite-hypothesis have been considered as incompatible alternative explanations, which have both been supported by a set of evidences from the fossil record, comparative morphology,
developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and di ...
and genetics. The expression of leg genes in the ontogeny of the insect wing has been universally considered as conclusive evidence in favour of the leg-exite-hypothesis, which proposes that insect wings are derived from mobile leg appendages (exites). However, the larvae of Coxoplectoptera show that the abdominal gills of mayflies and their ancestors, which are generally considered as corresponding structures to insect wings, articulated within the dorsal tergite plates. This cannot be seen in modern mayfly nymphs, because their abdominal tergites and sternites are fused, without any traces of separation left even in embryonic development. If nymphal gills and wings are corresponding ("serial homologous") structures and thus share the same evolutionary origin, the new results from Coxoplectoptera demonstrate that also wings are of tergal origin, as proposed by the classical paranotal-hypothesis. Staniczek, Bechly & Godunko (2011) therefore suggested a new hypothesis that could reconcile the apparently conflicting evidence from paleontology and developmental genetics: wings originated as stiff outgrowths of tergal plates ( paranota), and only later in evolution became mobile, articulated appendages through secondary recruiting of leg genes. Within pterygote insects the Coxoplectoptera represent the
sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...
of modern mayflies ( Ephemeroptera). This relationship is indicated by several
synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...
, such as: adult wing venation with costal brace (absent in other winged insects), nymphs with 7 pairs of abdominal gills (compared to still 9 pairs in Permoplectoptera like '' Protereisma'' nymphs), and with single-segmented tarsus with unpaired claw (compared to 3-segmented tarsus with paired claw in Permoplectoptera like ''Protereisma'' larvae). Together with mayflies and dragonflies they belong to the clade Palaeoptera, which is characterized by a derived wing articulation with fused sclerites, a vertical resting position of the wings in the
groundplan Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived cha ...
, and a
wing venation Insect wings are adult outgrowths of the insect exoskeleton that enable insects to flight, fly. They are found on the second and third Thorax (insect anatomy), thoracic segments (the mesothorax and metathorax), and the two pairs are often referre ...
with intercalary veins between the main longitudinal veins (esp. IR1+ between RP1- and RP2-, and IR2+ between RP2- and RP3/4-). Because of some very primitive character states, the Coxoplectoptera rather looked like early Paleozoic ancestors of mayflies, e.g. in the wing venation of the adult stage they still had the elongate costal brace that is not fused to the costal margin, and in the nymphal stage they still had articulated lateral wing pads. The large and broad hind wings are a further plesiomorphy compared to the small hind wing of modern mayflies, and even compared to the slender hind wing of Permian stem group mayflies like ''Protereisma''. The monophyly of Coxoplectoptera is demonstrated by several
autapomorphic In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...
characters in the adult stage, such as the raptorial forelegs and single-segmented tarsi with unpaired claw, as well as in the larval stage by the laterally compressed body, the body armature, the raptorial forelegs and burrowing mid- and hind legs, and the styliform shape of the ventrally directed abdominal gills. Coxoplectoptera are only known from the Jurassic and the Lower Cretaceous. It is not yet known why and when they went
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
.


Systematics

The
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Coxoplectoptera contains a single family Mickoleitiidae with two
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
from the Mesozoic: ''Mickoleitia'' (
Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145  Ma to 100.5 Ma. Geology Pro ...
, Crato Formation, Brazil): * ''Mickoleitia longimanus'' ( type species) * ''Mickoleitia spec.'' (smaller unnamed species, represented by a single adult specimen in a private fossil collection in Japan) '' Mesogenesia'' (Middle or Late Jurassic, Transbaikals): * ''Mesogenesia petersae'' (= ''Archaeobehnigia edmundsi'')


References


Bibliography

* (1977): Distinctive new mayfly nymphs (Ephemeroptera; Palingeniidae, Behningiidae) from the Jurassic of Transbaikal. ''Paleontologicheskii Zhurnal'', 2: 91-96. (in Russian). * et al. (Hrsg.) (2001): Ur-Geziefer - Die faszinierende Evolution der Insekten. ''Stuttgarter Beiträge zur Naturkunde Serie C'', 49: 96 pp., Stuttgart. ISSN 0341-0161
PDF fulltext
. * (2002): Fossile Eintagsfliegen - Einblicke in die Welt urtümlicher Fluginsekten. ''Fossilien'', 19: 297-302. * (2003): Eintagsfliegen - Manna der Flüsse. ''Stuttgarter Beiträge zur Naturkunde Serie C'', 53: 80 pp., Stuttgart. ISSN 0341-0161. * (Hrsg.) (2007): ''The Crato Fossil Beds of Brazil - Window into an Ancient World.'' Cambridge University Press, Cambridge etc. . * (2011): Coxoplectoptera, a new fossil order of Palaeoptera (Arthropoda: Insecta), with comments on the phylogeny of the stem group of mayflies (Ephemeroptera). ''Insect Systematics & Evolution'', 42(2): 101-138, Brill, Leiden. ISSN 1399-560X

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External links

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* ttp://www.livescience.com/15100-insect-frakenstein-fossil-order-coxoplectoptera.html LiveScience: Ancient 'Frankenstein' Insect Discovered
Scientific American: Odd Insect Fossils Suggest Early Carnivorous Lifestyle

MSNBC: Fossil reveals an ancient 'Frankenstein' insect

Fox News: Ancient 'Frankenstein' Insect Discovered

YouTube: feature in German L-TV news magazine, incl. interviews

YouTube: feature in German Regio-TV news journal, incl. interviews
{{Taxonbar, from1=Q1073158, from2=Q21447579 Extinct insect orders Cretaceous insects Tithonian first appearances Early Cretaceous extinctions Prehistoric arthropods of Asia Jurassic animals of Asia Prehistoric arthropods of South America Early Cretaceous animals of South America