Misplaced Pages

#77922

44-475: 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 the Aptian age , about 113 million years ago. It thought to have been deposited in a semi-arid lacustrine wetland environment. The Crato Formation earns

88-588: A brackish lagoon and semionotid fish preserved in phosphatized nodules . The fossils are usually compacted and preserved in layers of limestone. Fossil Odonata ( dragonflies ) and damselflies are especially rich in the Crato lagerstätte: currently 384 specimens have been recovered, 264 adults and 120 larvae. Hemiptera (true bugs) and Orthoptera (grasshoppers and crickets) are also abundant in number of species and in number of specimens. There are also plant remains. Local mining activities for cement and construction damage

132-409: 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. Because in

176-611: A geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Werner in his theory of the origin of the Earth, which was developed over the period from 1774 to his death in 1817. The concept became increasingly formalized over time and is now codified in such works as the North American Stratigraphic Code and its counterparts in other regions. Geologic maps showing where various formations are exposed at

220-478: A new maniraptor was described in 1996. The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy. Fish fossils in the area were noted in 1823. When they were first methodically published, in 1993, the Crato Formation limestones provided a new site for pterosaurs , one that also preserved insects that fell into

264-542: A newly designated formation could not be named the Kaibab Formation, since the Kaibab Limestone is already established as a formation name. The first use of a name has precedence over all others, as does the first name applied to a particular formation. As with other stratigraphic units, the formal designation of a formation includes a stratotype which is usually a type section . A type section

308-591: A peculiar freshwater shrimp -like habitus. 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 for stoneflies). The common name "chimera wings"

352-617: A permanent natural or artificial feature of the geographic area in which they were first described. The name consists of the geographic name plus either "Formation" or a descriptive name. Examples include the Morrison Formation , named for the town of Morrison, Colorado , and the Kaibab Limestone , named after the Kaibab Plateau of Arizona. The names must not duplicate previous formation names, so, for example,

396-449: Is not a valid lithological basis for defining a formation. The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region. Formations must be able to be delineated at the scale of geologic mapping normally practiced in the region; the thickness of formations may range from less than a meter to several thousand meters. Geologic formations are typically named after

440-683: Is a very rare bird that was discovered only in the late 20th century; it is not known from anywhere outside the characteristic forest that grows on the Chapada do Araripe soils formed ultimately from Crato and Santana Formation rocks. The Crato Formation has often historically been considered the lowest member of the Santana Formation (or, alternatively, the Araripina Formation) of the Araripe Group, later redefined as

484-528: Is also used informally to describe the odd shapes (forms) that rocks acquire through erosional or depositional processes. Such a formation is abandoned when it is no longer affected by the geologic agent that produced it. Some well-known cave formations include stalactites and stalagmites . Coxoplectoptera Coxoplectoptera or "chimera wings" is an extinct order of stem-group mayflies containing one family, Mickoleitiidae . Together with mayflies ( Ephemeroptera ), Coxoplectoptera are assigned to

SECTION 10

#1732772454078

528-560: Is central to the geologic discipline of stratigraphy , and the formation is the fundamental unit of stratigraphy. Formations may be combined into groups of strata or divided into members . Members differ from formations in that they need not be mappable at the same scale as formations, though they must be lithologically distinctive where present. The definition and recognition of formations allow geologists to correlate geologic strata across wide distances between outcrops and exposures of rock strata . Formations were at first described as

572-470: 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

616-455: Is ideally a good exposure of the formation that shows its entire thickness. If the formation is nowhere entirely exposed, or if it shows considerably lateral variation, additional reference sections may be defined. Long-established formations dating to before the modern codification of stratigraphy, or which lack tabular form (such as volcanic formations), may substitute a type locality for a type section as their stratotype. The geologist defining

660-502: 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 and functional mouthparts (preserved are 3-segmented labial palps). The thoracic segments are obliquely tilted backwards as in dragonflies, so that

704-412: Is unique among all known fossil and Recent aquatic insect 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

748-472: The Middle or Upper Jurassic 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. 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

792-605: The Romualdo Formation of the Santana Group . The Crato Member is the product of a single phase, where complicated sequence of sediment strata reflect changeable conditions in the opening sea. The age of this strata has been controversial, though most workers have agreed that it lies on or near the Aptian-Albian boundary, about 112 million years ago. The extent of the Crato unit and its relationship to

836-529: 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

880-409: 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. The more than 20 described nymphs of different stages have a body length of 10 to 32 millimetres (0.39 to 1.26 in). Their laterally compressed body

924-680: 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

SECTION 20

#1732772454078

968-624: The Romualdo Formation had long been ill-defined. It was not until a 2007 volume on the unit by Martill, Bechly and Loveridge that the Crato Formation was given a formal type locality, and was formally made a distinct formation separate from the Santana, which is about 10 Ma younger. The Crato Formation is considered time equivalent with the Paracuru Formation . (Note: Many more insects have been described than are present in

1012-533: 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. The abundance of fossils,

1056-470: 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 allochthonous elements into the brackish Crato lagoon, were the limestones were deposited. The raptorial forelegs, sabre-like mandibles, large eyes and long antennae indicate that

1100-507: The clade Heptabranchia . 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 . The nymphs had

1144-451: The clade Palaeoptera , 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 ancestors of mayflies, e.g. in

1188-412: 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

1232-423: The designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator-prey relationships in this ecosystem. There are also fine examples of pterosaurs , reptiles and amphibians, invertebrates (particularly insects), and plants. Even dinosaurs are represented:

1276-404: 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 and genetics . The expression of leg genes in the ontogeny of

1320-550: The essential geologic time markers, based on their relative ages and the law of superposition . The divisions of the geological time scale were described and put in chronological order by the geologists and stratigraphers of the 18th and 19th centuries. Geologic formations can be usefully defined for sedimentary rock layers, low-grade metamorphic rocks , and volcanic rocks . Intrusive igneous rocks and highly metamorphosed rocks are generally not considered to be formations, but are described instead as lithodemes . "Formation"

1364-522: The formation is expected to describe the stratotype in sufficient detail that other geologists can unequivocally recognize the formation. Although formations should not be defined by any criteria other than primary lithology, it is often useful to define biostratigraphic units on paleontological criteria, chronostratigraphic units on the age of the rocks, and chemostratigraphic units on geochemical criteria, and these are included in stratigraphic codes. The concept of formally defined layers or strata

Crato Formation - Misplaced Pages Continue

1408-680: 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

1452-528: 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 described

1496-545: 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

1540-456: 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

1584-472: 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. The nymphs of Coxoplectoptera provided new clues to

1628-517: 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

1672-556: 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

1716-458: The sites. Trade in illegally collected fossils has sprung up in the last decade, driven by the remarkable state of preservation and beauty of these fossils and amounting to a considerable local industry. An urgent preservation program is being called for by paleontologists. In addition, the weathering of Crato and Santana Formation rocks has contributed soil conditions unlike elsewhere in the region. The Araripe manakin ( Antilophia bokermanni )

1760-643: The surface are fundamental to such fields as structural geology , allowing geologists to infer the tectonic history of a region or predict likely locations for buried mineral resources. The boundaries of a formation are chosen to give it the greatest practical lithological consistency. Formations should not be defined by any criteria other than lithology. The lithology of a formation includes characteristics such as chemical and mineralogical composition, texture, color, primary depositional structures , fossils regarded as rock-forming particles, or other organic materials such as coal or kerogen . The taxonomy of fossils

1804-432: The surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of

Crato Formation - Misplaced Pages Continue

1848-1041: The table below) Araripenymphes A. seldoni Nova Olinda Member A Cratosmylidae lacewing Gracilepteryx G. pulchra An Eolepidopterigidae moth Makarkinia M. adamsi M. kerneri A Kalligrammatid lacewing Mickoleitia M. longimanus A Coxoplectopteran insect Netoxena N. nana An Eolepidopterigidae moth Principiala P. incerta An Ithonidae lacewing, type species of Principiala Psamateia P. calipsa An Eolepidopterigidae moth Rafaeliana R. maxima Neuropterida incertae sedis Undopterix U. cariensis An Eolepidopterigidae moth Arariphrynus Arariphrynus placidoi Cratia Cratia gracilis Cratopipa Cratopipa novaolindensis Eurycephalella Eurycephalella alcinae Kururubatrachus Kururubatrachus gondwanicus Pipoidea Possible indeterminate pipoid remains. Calanguban Formation (stratigraphy) A formation must be large enough that it can be mapped at

1892-431: 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

1936-412: 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. The fossil nymphs of the genus Mickoleitia are not especially rare in

#77922