Coxoplectoptera or "chimera wings" is an extinct order of

stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

mayflies Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the order ...

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 Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...

Crato Formation The Crato Formation is a geologic formation of Early Cretaceous (Aptian) age in northeastern Brazil's Araripe Basin. It is an important Lagerstätte (undisturbed fossil accumulation) for palaeontologists. The strata were laid down mostly during ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

(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. The nymphs had a peculiar freshwater shrimp-like habitus.

Etymology

The genus ''Mickoleitia'' and family Mickoleitiidae was named in honor of German zoologist Gerhard Mickoleit from the

University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (german: Eberhard Karls Universität Tübingen; la, Universitas Eberhardina Carolina), is a public research university located in the city of Tübingen, Baden-W� ...

, who was among the first proponents of

Willi Hennig Emil Hans Willi Hennig (20 April 1913 – 5 November 1976) was a German biologist and zoologist who is considered the founder of phylogenetic systematics, otherwise known as cladistics. In 1945 as a prisoner of war, Hennig began work on his the ...

's "

Phylogenetic Systematics 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 chara ...

". 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 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 Chimera, Chimaera, or Chimaira (Greek for " she-goat") originally referred to: * Chimera (mythology), a fire-breathing monster of Ancient Lycia said to combine parts from multiple animals * Mount Chimaera, a fire-spewing region of Lycia or Cilici ...

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 The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centuri ...

). 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 A living fossil is an extant taxon that cosmetically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living foss ...

in the Lower Cretaceous. The German biologist Rainer Willmann 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 A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

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 of

Transbaikal Transbaikal, Trans-Baikal, Transbaikalia ( rus, Забайка́лье, r=Zabaykalye, p=zəbɐjˈkalʲjɪ), or Dauria (, ''Dauriya'') is a mountainous region to the east of or "beyond" (trans-) Lake Baikal in Far Eastern Russia. The steppe and ...

s, 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 The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...

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. The head of ''Mickoleitia'' was provided with large

compound eyes A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distin ...

and functional mouthparts (preserved are 3-segmented labial palps). The

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

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 The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...

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 In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

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 nymphs, and rather resembles the body of

gammarid Gammaridae is a family of amphipods. In North America they are included among the folk taxonomic category of " scuds", and otherwise gammarids is usually used as a common name. They have a wide distribution, centered on Eurasia, and are euryha ...

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 In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

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 A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'mar ...

that are distinctly separated from the ventral

sternites The sternum (pl. "sterna") is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the ...

. 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 adaptations (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 predator Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey ...

s that were hiding, partly burrowed in the

river bed A stream bed or streambed is the bottom of a stream or river (bathymetry) or the physical confine of the normal water flow ( channel). The lateral confines or channel margins are known as the stream banks or river banks, during all but flood ...

, 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

record,

comparative morphology Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny (the evolution of species). The science began in the classical era, continuing i ...

, developmental biology and

genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...

. The expression of leg

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

s in the

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the s ...

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 Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

and

developmental genetics Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem c ...

: 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 of modern mayflies ( Ephemeroptera). This relationship is indicated by several synapomorphies, 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 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 as characterizes the Neopte ...

, which is characterized by a derived wing articulation with fused sclerites, a vertical resting position of the wings in the groundplan, and a wing venation 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 The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

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 In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and ...

compared to the small hind wing of modern mayflies, and even compared to the slender hind wing of

stem group mayflies like ''Protereisma''. The monophyly of Coxoplectoptera is demonstrated by several autapomorphic 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.

Systematics

The order Coxoplectoptera contains a single

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Mickoleitiidae with two genera from the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

: ''Mickoleitia'' ( Early Cretaceous,

): * ''Mickoleitia longimanus'' (

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

) * ''Mickoleitia spec.'' (smaller unnamed species, represented by a single adult specimen in a private fossil collection in Japan) '' Mesogenesia'' (Middle or

Late 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 ...

s): * ''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

.

External links

*

* 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