34-648: Archelosauria is a clade grouping turtles and archosaurs (birds and crocodilians) and their fossil relatives, to the exclusion of lepidosaurs (the clade containing lizards , snakes and the tuatara ). The majority of phylogenetic analyses based on molecular data (e.g. DNA and proteins ) have supported a sister-group relationship between turtles and archosaurs. On the other hand, Archelosauria had not been historically supported by most morphological analyses, which have instead found turtles to either be descendants of parareptiles , early-diverging diapsids outside of Sauria , or close relatives of lepidosaurs within
68-588: A population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of
102-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
136-446: A branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
170-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
204-490: A dense row. The teeth sequentially decrease in size posteriorly. Compared to Weigeltisaurus , Coelourosauravus has a shorter neck and longer thorax (which is also flattened), and like other weigeltisaurids the tail is elongate. Like other weigeltisaurids, the penultimate phalanges are elongated, which in combination with their recurved unguals indicative of claws were likely an adaption to cling to tree bark. At least 29 pairs of long, elongate rod-shaped bones project from
238-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
272-464: A substantial drop in height per glide, corresponding with a steep descent angle of more than 45 degrees. However, some authors have considered that the unique configuration and aspect ratio of the wings of weigeltisaurids means that the comparison needs to be tested experimentally. The Lower Sakamena Formation was deposited in a wetland environment situated within a North-South orientated rift valley , perhaps similar to Lake Tanganyika . The climate at
306-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
340-537: Is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are the fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual,
374-471: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
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#1732891566166408-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
442-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
476-522: The Carboniferous to the Triassic ), as early-diverging diapsids outside of Sauria, or as close relatives of Lepidosauria. The hypothetical clade formed by turtles and lepidosaurs to the exclusion of archosaurs is known as Ankylopoda . A 2022 analysis by Simões et al. found a monophyletic Archelosauria using only morphological data for the first time, thus agreeing with most molecular analyses. Archelosauria
510-467: The type species , C. elivensis , which was named by Jean Piveteau in 1926 based on fossils from the Lower Sakamena Formation of Madagascar . The species Weigeltisaurus jaekeli from Europe was formerly considered a species of Coelurosauravus , but is now placed in its own genus. The only known specimens of Coelurosauravus were collected in 1907-1908 by J.-M. Colcanap, a captain of
544-805: The French colonial infantry, in southwest Madagascar. The precise location is not known, but it is likely from Mount Eliva near the upstream part of the Sakamena River, a tributary of the Onilahy River . In 1926, the specimens were described by Jean Piveteau as Coelurosauravus elivensis . In 1930 Weigeltisaurus jaekeli was described from specimens Germany . This European species is now known from numerous specimens found in Germany (and one in England ), of which some were very well preserved. In 1987, Weigeltisaurus jaekeli
578-501: The clade Ankylopoda . Some recent morphological analyses have also found support for Archelosauria. Multiple sequence alignments of DNA and protein sequences and phylogenetic inferences have shown that turtles are the closest living relatives to birds and crocodilians. There are about 1000 ultra-conserved elements in the genome that are unique to turtles and archosaurs , but which are not found in lepidosaurs . Other genome-wide analyses also support this grouping. Archelosauria
612-867: The definition to specifically exclude the lizard Lacerta agilis from the group. Below is the phylogeny from Crawford et al. , showing interrelationships of Testudines at family level down to Durocryptodira . Archelosauria was grouped within Sauria (the clade formed by archosaurs and lepidosaurs), as the sister branch to Lepidosauria, the clade containing lizards, snakes and the tuatara . Sphenodon Anolis Python Chelidae Pelomedusidae Podocnemididae Carettochelys Trionychidae Durocryptodira Crocodylus Gallus Analyses based on morphological data have generally recovered turtles either as non- diapsid reptiles nested within Parareptilia (a group of basal reptiles that lived from
646-413: The family Weigeltisauridae , members of this genus possessed long, rod-like ossifications projecting outwards from the body. These bony rods were not extensions of the ribs but were instead a feature unique to weigeltisaurids. It is believed that during life, these structures formed folding wings used for gliding flight , similar to living gliding Draco lizards. Coelurosauravus is solely known from
680-421: The fourth digit of the hands of weigeltisaurids, which would have allowed them to more effectively grasp the wing. In a 2011 study comparing Coelurosauravus elivensis and other extinct gliding reptiles to modern Draco species, Coelurosauravus was found to be a less efficient glider than modern Draco due to its larger body size, with a wing loading around 107.9 N/m , 4.5 times than higher than Draco, with
714-419: The holotype specimen, but it has subsequently been regarded as not distinct from C. elivensis. The skull of Coelurosauravus is the smallest of the weigeltisaurids, with a mature skull length of 3.5 centimetres (1.4 in) around half those of other weigeltisaurids. The total combined head and torso length is 18 centimetres (7.1 in), reaching a length of at least 35 centimetres (14 in) including
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#1732891566166748-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
782-411: The low-wing configuration, it is likely that the gliding surface was angled upwards to increase stability. In living gliding lizards, it has been found that the forelimbs grab hold of the membrane during flight, suggesting that the forelimbs are used to control the patagium while in flight. Similar behaviour has been proposed for weigeltisaurids. This is supported the presence of an additional phalange in
816-414: The piercing of arthropod cuticle. The cranial ornamentation may have served a display purpose. The rods originate from the lower-lateral surface of the body. The furling and unfurling of the gliding membrane were likely controlled by the abdominal muscles . Preserved fossils of Weigeltisaurus show that the bony rods had a high degree of flexibility, similar to the ribs of living gliding lizards . Due to
850-417: The preserved length of the tail. Like other weigeltisaurids, the skull bones are covered in cranial ornamentation, consisting of low tubercles and spikes, including a horned frill present on the squamosal bone . In contrast to Weigeltisaurus , only tubercles, rather than spikes, are present on the parietal bone , which is also shared with Glaurung . The teeth are simple and conical in shape and packed into
884-482: The relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade" is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade"
918-582: The sides of the body, dubbed "patagials". These are roughly equally spaced along the trunk. The first nine patagials show a rapid increase in size, with the ninth being the longest of all of the patagials, with the remaining pairs gradually decreasing in size posteriorly. When fully opened, each patagial membrane would have had a wingspan of 35 centimetres (14 in). Though no stomach contents have been found, Coelurosauravus and other weigeltisaurids have been interpreted as arboreal insectivores . The simple conical teeth of Coelurosauravus are well adapted to
952-603: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Coelurosauravus Coelurosauravus (meaning "hollow lizard grandfather") is an extinct genus of gliding reptile, known from the Late Permian of Madagascar. Like other members of
986-423: The three Mesozoic marine reptile clades of uncertain placement: Lepidosauromorpha Coelurosauravus Choristodera Testudines Thalattosauria Sauropterygia Ichthyosauromorpha Archosauromorpha [REDACTED] Clade In biological phylogenetics , a clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group ,
1020-473: The time of deposition was temperate, warm, and humid, with seasonal rainfall and possible monsoons Flora from the formation includes the equisetalean Schizoneura , the glossopterid gymnosperm Glossopteris , and seed fern Lepidopteris . Other vertebrates known from the Lower Sakamena Formation include the palaeoniscoid fish Atherstonia , the procolophonid parareptile Barasaurus ,
1054-423: Was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case, the group consists of a common ancestor with all its descendant branches. Rodents, for example, are
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1088-650: Was diagnosed by two unambiguous synapomorphies (shared derived traits): a sagittal crest on the supraoccipital bone, and the lack of an entepicondylar foramen on the humerus . A cladogram adapted from their analysis is shown below: Younginiformes Eunotosaurus Coelurosauravus Sphenodontia Squamata Pappochelys Odontochelys Kayentachelys Proganochelys Ichthyosauromorpha Sauropterygia Thalattosauria Protorosauria Allokotosauria Rhynchosauria Prolacerta Archosauriformes Wolniewicz et al (2023) also found evidence for an expanded Archelosauria containing
1122-502: Was named in a 2015 article by Crawford et al . The name is meant to evoke the archosaurs and chelonians (turtles), the two living subgroups of the clade. Crawford et al. defined Archelosauria as the clade formed by the descendants of the most recent common ancestor of Crocodylus niloticus (the Nile crocodile) and Testudo graeca (the Greek tortoise). A 2021 article by Joyce et al. modified
1156-411: Was synonymized with Coelurosauravus as a second species, Coelurosauravus jaekeli . However, a 2015 study reinstated Weigeltisaurus as a separate genus for "Coelurosauravus" jaekeli, which has been retained by subsequent authors . In 1979 Robert L. Carroll placed one of the C. elivensis specimens into the new genus and species Daedalosaurus madigascariensis , based on supposed differences with
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