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91-565: Palaeognathae ( / ˌ p æ l i ˈ ɒ ɡ n ə θ i / ; from Ancient Greek παλαιός (palaiós)  'old' and γνάθος (gnáthos)  'jaw') is an infraclass of birds , called paleognaths or palaeognaths , within the class Aves of the clade Archosauria . It is one of the two extant infraclasses of birds, the other being Neognathae , both of which form Neornithes. Palaeognathae contains five extant orders consisting of four flightless lineages (plus two that are extinct), termed ratites , and one flying lineage,

182-543: A pitch accent . In Modern Greek, all vowels and consonants are short. Many vowels and diphthongs once pronounced distinctly are pronounced as /i/ ( iotacism ). Some of the stops and glides in diphthongs have become fricatives , and the pitch accent has changed to a stress accent . Many of the changes took place in the Koine Greek period. The writing system of Modern Greek, however, does not reflect all pronunciation changes. The examples below represent Attic Greek in

273-504: A favored allele will tend to increase exponentially in frequency when rare. Genome size is influenced by the amount of repetitive DNA as well as number of genes in an organism. Some organisms, such as most bacteria, Drosophila , and Arabidopsis have particularly compact genomes with little repetitive content or non-coding DNA. Other organisms, like mammals or maize, have large amounts of repetitive DNA, long introns , and substantial spacing between genes. The C-value paradox refers to

364-525: A fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Regarding the speech of the ancient Macedonians diverse theories have been put forward, but the epigraphic activity and the archaeological discoveries in the Greek region of Macedonia during the last decades has brought to light documents, among which the first texts written in Macedonian , such as

455-405: A flat breastbone, or sternum , shaped like a raft. This characteristic sternum differs from that in flighted birds, where the pectoral musculature is disproportionately large to provide the power for wingbeats and the sternum develops a prominent keel, or carina sterni to anchor these muscles. The clavicles do not fuse into a furcula. Instead, if present at all, each is splint-like and lies along

546-679: A mechanism by which various birds became flightless and came to look similar to one another. Hope (2002) reviewed all known bird fossils from the Mesozoic looking for evidence of the origin of the evolutionary radiation of the Neornithes . That radiation would also signal that the paleognaths had already diverged. She notes five Early Cretaceous taxa that have been assigned to the Palaeognathae. She finds that none of them can be clearly assigned as such. However, she does find evidence that

637-661: A novel gene sequence. Chimeras often cause regulatory changes and can shuffle protein domains to produce novel adaptive functions. De novo gene birth can give rise to protein-coding genes and non-coding genes from previously non-functional DNA. For instance, Levine and colleagues reported the origin of five new genes in the D. melanogaster genome. Similar de novo origin of genes has been also shown in other organisms such as yeast, rice and humans. De novo genes may evolve from spurious transcripts that are already expressed at low levels. Constructive neutral evolution (CNE) explains that complex systems can emerge and spread into

728-607: A population through neutral transitions with the principles of excess capacity, presuppression, and ratcheting, and it has been applied in areas ranging from the origins of the spliceosome to the complex interdependence of microbial communities . The Society for Molecular Biology and Evolution publishes the journals "Molecular Biology and Evolution" and "Genome Biology and Evolution" and holds an annual international meeting. Other journals dedicated to molecular evolution include Journal of Molecular Evolution and Molecular Phylogenetics and Evolution . Research in molecular evolution

819-550: A prefix /e-/, called the augment . This was probably originally a separate word, meaning something like "then", added because tenses in PIE had primarily aspectual meaning. The augment is added to the indicative of the aorist, imperfect, and pluperfect, but not to any of the other forms of the aorist (no other forms of the imperfect and pluperfect exist). The two kinds of augment in Greek are syllabic and quantitative. The syllabic augment

910-452: A proper semicircular furcula , with no trace of a hypocleidium . There is an acute angle between the scapula and coracoid , as in all flying birds. The pelvis has an open ilio–ischiatic fenestra that incises the posterior edge between the ilium and ischium , as in all paleognaths. Tinamous have no true pygostyle , their caudal vertebrae remain unfused, as in ratites. Tinamou feathers look like those of volant birds in that they have

1001-474: A rachis and two vanes. The structure of tinamou feathers is unique, however, in that they have barbs that remain joined at their tips. Thus the parallel barbs are separated only by slits between them. Tinamous have uropygial glands . Ratite birds are strictly flightless and their anatomy reflects specializations for terrestrial life. The term " ratite " is from the Latin word for raft, ratis , because they possess

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1092-405: A result of small effective population sizes. With a smaller effective population size, a larger variety of mutations will behave as if they are neutral due to inefficiency of selection. Gene conversion occurs during recombination, when nucleotide damage is repaired using an homologous genomic region as a template. It can be a biased process, i.e. one allele may have a higher probability of being

1183-471: A single pair of chromosomes whereas the Adders-tongue fern Ophioglossum reticulatum has up to 1260 chromosomes. The number of chromosomes in an organism's genome does not necessarily correlate with the amount of DNA in its genome. The genome-wide amount of recombination is directly controlled by the number of chromosomes, with one crossover per chromosome or per chromosome arm, depending on

1274-542: A strong Northwest Greek influence, and can in some respects be considered a transitional dialect, as exemplified in the poems of the Boeotian poet Pindar who wrote in Doric with a small Aeolic admixture. Thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Pamphylian Greek , spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either

1365-473: A very long, keeled, breastbone with an unusual three-pronged shape. This bone, the sternum , has a central blade (the Carina sterni ), with two long, slender lateral trabeculae , which curve to either side and nearly touch the keel posteriorly. These trabeculae may also be thought of as the rims of two large foramina that incise the posterior edge of the sternum, and extend almost its whole length. Tinamous have

1456-510: A vowel or /n s r/ ; final stops were lost, as in γάλα "milk", compared with γάλακτος "of milk" (genitive). Ancient Greek of the classical period also differed in both the inventory and distribution of original PIE phonemes due to numerous sound changes, notably the following: The pronunciation of Ancient Greek was very different from that of Modern Greek . Ancient Greek had long and short vowels ; many diphthongs ; double and single consonants; voiced, voiceless, and aspirated stops ; and

1547-481: Is a large, open ilio–ischiatic fenestra in the pelvis. The pubis and ischium are likely to be longer than the ilium , protruding out beneath the tail. The postacetabular portion of the pelvis is longer than the preacetabular portion. Paleognaths share a pattern of grooves in the horny covering of the bill. This covering is called the rhamphotheca . The paleognath pattern has one central strip of horn, with long, triangular, strips to either side. In paleognaths,

1638-418: Is added to stems beginning with consonants, and simply prefixes e (stems beginning with r , however, add er ). The quantitative augment is added to stems beginning with vowels, and involves lengthening the vowel: Some verbs augment irregularly; the most common variation is e → ei . The irregularity can be explained diachronically by the loss of s between vowels, or that of the letter w , which affected

1729-448: Is considered by some linguists to have been closely related to Greek . Among Indo-European branches with living descendants, Greek is often argued to have the closest genetic ties with Armenian (see also Graeco-Armenian ) and Indo-Iranian languages (see Graeco-Aryan ). Ancient Greek differs from Proto-Indo-European (PIE) and other Indo-European languages in certain ways. In phonotactics , ancient Greek words could end only in

1820-479: Is currently lacking. Living members of Palaeognathae range from 6 inches (15 cm) to 9 feet (2.7 m) and weight can be from .09 to 345 pounds (0.0–156.5 kg). Ostriches are the largest struthioniforms (members of the order Struthioniformes), with long legs and neck. They range in height from 5.7 to 9 feet (1.7–2.7 m) and weigh from 139 to 345 pounds (63–156 kg). They have loose-feathered wings. Males have black and white feathers while

1911-401: Is equal to the mutation rate per replication. A relatively constant mutation rate thus produces a constant rate of change per generation (molecular clock). Slightly deleterious mutations with a selection coefficient less than a threshold value of 1 / the effective population size can also fix. Many genomic features have been ascribed to accumulation of nearly neutral detrimental mutations as

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2002-547: Is far higher than that of mammals, due largely to flight, and oxygen needs are high. Hence, most birds have small, compact genomes with few repetitive elements. Indirect evidence suggests that non-avian theropod dinosaur ancestors of modern birds also had reduced genome sizes, consistent with endothermy and high energetic needs for running speed. Many bacteria have also experienced selection for small genome size, as time of replication and energy consumption are so tightly correlated with fitness. The ant Myrmecia pilosula has only

2093-644: Is incorrect; tinamous are within the ratite radiation, meaning flightlessness arose independently multiple times via parallel evolution . There are three extinct groups that are undisputed members of Palaeognathae: the Lithornithiformes , the Dinornithiformes ( moas ) and the Aepyornithiformes ( elephant birds ), the latter two of which became extinct in the last 1250 years. There are other extinct birds which have been allied with

2184-416: Is often found for genes involved in intragenomic conflict , sexual antagonistic coevolution , and the immune system . Genetic drift is the change of allele frequencies from one generation to the next due to stochastic effects of random sampling in finite populations. These effects can accumulate until a mutation becomes fixed in a population . For neutral mutations, the rate of fixation per generation

2275-813: Is then used to generate one or more plausible trees. Some phylogenetic methods account for variation among sites and among tree branches . Different genes, e.g. hemoglobin vs. cytochrome c , generally evolve at different rates . These rates are relatively constant over time (e.g., hemoglobin does not evolve at the same rate as cytochrome c, but hemoglobins from humans, mice, etc. do have comparable rates of evolution), although rapid evolution along one branch can indicate increased directional selection on that branch. Purifying selection causes functionally important regions to evolve more slowly, and amino acid substitutions involving similar amino acids occurs more often than dissimilar substitutions. Gene duplication can produce multiple homologous proteins (paralogs) within

2366-679: The Archaic or Epic period ( c.  800–500 BC ), and the Classical period ( c.  500–300 BC ). Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers . It has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance . This article primarily contains information about

2457-610: The Cretaceous . Given the northern hemisphere location of the morphologically most basal fossil forms (such as Lithornis , Pseudocrypturus , Paracathartes and Palaeotis ), a Laurasian origin for the group can be inferred. The present almost entirely Gondwanan distribution would then have resulted from multiple colonisations of the southern landmasses by flying forms that subsequently evolved flightlessness, and in many cases, gigantism. One study of molecular and paleontological data found that modern bird orders, including

2548-606: The Epic and Classical periods of the language, which are the best-attested periods and considered most typical of Ancient Greek. From the Hellenistic period ( c.  300 BC ), Ancient Greek was followed by Koine Greek , which is regarded as a separate historical stage, though its earliest form closely resembles Attic Greek , and its latest form approaches Medieval Greek . There were several regional dialects of Ancient Greek; Attic Greek developed into Koine. Ancient Greek

2639-460: The Neotropic tinamous . There are 47 species of tinamous, five of kiwis ( Apteryx ), three of cassowaries ( Casuarius ), one of emus ( Dromaius ) (another became extinct in historic times), two of rheas ( Rhea ) and two of ostriches ( Struthio ). Recent research has indicated that paleognaths are monophyletic but the traditional taxonomic split between flightless and flighted forms

2730-501: The Pella curse tablet , as Hatzopoulos and other scholars note. Based on the conclusions drawn by several studies and findings such as Pella curse tablet , Emilio Crespo and other scholars suggest that ancient Macedonian was a Northwest Doric dialect , which shares isoglosses with its neighboring Thessalian dialects spoken in northeastern Thessaly . Some have also suggested an Aeolic Greek classification. The Lesbian dialect

2821-603: The epic poems , the Iliad and the Odyssey , and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects. The origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between

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2912-501: The present , future , and imperfect are imperfective in aspect; the aorist , present perfect , pluperfect and future perfect are perfective in aspect. Most tenses display all four moods and three voices, although there is no future subjunctive or imperative. Also, there is no imperfect subjunctive, optative or imperative. The infinitives and participles correspond to the finite combinations of tense, aspect, and voice. The indicative of past tenses adds (conceptually, at least)

3003-443: The 1950s to explore homologous proteins . The advent of protein sequencing allowed molecular biologists to create phylogenies based on sequence comparison, and to use the differences between homologous sequences as a molecular clock to estimate the time since the most recent common ancestor . The surprisingly large amount of molecular divergence within and between species inspired the neutral theory of molecular evolution in

3094-1031: The 5th century BC. Ancient pronunciation cannot be reconstructed with certainty, but Greek from the period is well documented, and there is little disagreement among linguists as to the general nature of the sounds that the letters represent. /oː/ raised to [uː] , probably by the 4th century BC. Greek, like all of the older Indo-European languages , is highly inflected. It is highly archaic in its preservation of Proto-Indo-European forms. In ancient Greek, nouns (including proper nouns) have five cases ( nominative , genitive , dative , accusative , and vocative ), three genders ( masculine , feminine , and neuter ), and three numbers (singular, dual , and plural ). Verbs have four moods ( indicative , imperative , subjunctive , and optative ) and three voices (active, middle, and passive ), as well as three persons (first, second, and third) and various other forms. Verbs are conjugated through seven combinations of tenses and aspect (generally simply called "tenses"):

3185-495: The Archaic period of ancient Greek (see Homeric Greek for more details): Μῆνιν ἄειδε, θεά, Πηληϊάδεω Ἀχιλῆος οὐλομένην, ἣ μυρί' Ἀχαιοῖς ἄλγε' ἔθηκε, πολλὰς δ' ἰφθίμους ψυχὰς Ἄϊδι προΐαψεν ἡρώων, αὐτοὺς δὲ ἑλώρια τεῦχε κύνεσσιν οἰωνοῖσί τε πᾶσι· Διὸς δ' ἐτελείετο βουλή· ἐξ οὗ δὴ τὰ πρῶτα διαστήτην ἐρίσαντε Ἀτρεΐδης τε ἄναξ ἀνδρῶν καὶ δῖος Ἀχιλλεύς. The beginning of Apology by Plato exemplifies Attic Greek from

3276-668: The Classical period of ancient Greek. (The second line is the IPA , the third is transliterated into the Latin alphabet using a modern version of the Erasmian scheme .) Ὅτι [hóti Hóti μὲν men mèn ὑμεῖς, hyːmêːs hūmeîs,   Molecular evolution The history of molecular evolution starts in the early 20th century with comparative biochemistry , and the use of "fingerprinting" methods such as immune assays, gel electrophoresis , and paper chromatography in

3367-676: The DNA fall within a region coding for a protein , they are characterized by whether they are synonymous (do not change the amino acid sequence) or non-synonymous. Other types of mutations modify larger segments of DNA and can cause duplications, insertions, deletions, inversions, and translocations. The distribution of rates for diverse kinds of mutations is called the "mutation spectrum" (see App. B of ). Mutations of different types occur at widely varying rates. Point mutation rates for most organisms are very low, roughly 10 to 10 per site per generation, though some viruses have higher mutation rates on

3458-748: The DNA level under selective pressure at rates comparable to the Neognathae branch of living birds, though there is some controversy about the precise relationship between them and the other birds. There are also several other scientific controversies about their evolution (see below). No unambiguously paleognathous fossil birds are known until the Cenozoic (though birds occasionally interpreted as lithornithids occur in Albian appalachian sites), but there have been many reports of putative paleognaths, and it has long been inferred that they may have evolved in

3549-545: The Dorians. The Greeks of this period believed there were three major divisions of all Greek people – Dorians, Aeolians, and Ionians (including Athenians), each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, and Cypriot, far from the center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for

3640-613: The Neognathae and, therefore, also the Palaeognathae had diverged no later than the Early Campanian age of the Cretaceous period. Vegavis is a fossil bird from the Maastrichtian stage of Late Cretaceous Antarctica. Vegavis is most closely related to true ducks. Because virtually all phylogenetic analyses predict that ducks diverged after paleognaths, this is evidence that paleognaths had already arisen well before that time. An exceptionally preserved specimen of

3731-433: The Palaeognathae by at least one author, but their affinities are a matter of dispute. The word Paleognath is derived from the ancient Greek for 'old jaws' in reference to the skeletal anatomy of the palate , which is described as more primitive and reptilian than that in other birds. Paleognathous birds retain some basal morphological characters but are by no means living fossils as their genomes continued to evolve at

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3822-462: The Palaeognathae. The topic has been studied by Dubois (1891), Sharpe (1891), Shufeldt (1904), Sibley and Ahlquist (1972, 1981) and Cracraft (1981). Merrem (1813) is often credited with classifying the paleognaths together, and he coined the taxon "Ratitae" (see above). However, Linnaeus (1758) placed cassowaries, emus, ostriches, and rheas together in Struthio . Lesson (1831) added

3913-588: The Ratitae-Carinatae classification that separated tinamous and ratites. He reasoned that a keelless, or "ratite", sternum could easily evolve in unrelated birds that independently became flightless. He also recognized that the ratites were secondarily flightless. His subdivisions were based on the characters of the palatal skeleton and other organ systems. He established seven roughly modern orders of living and fossil paleognaths (Casuarii, Struthiones, Rheae, Dinornithes, Aepyornithes, Apteryges, and Crypturi –

4004-411: The adults have brown feathers. Ancient Greek language Ancient Greek ( Ἑλληνῐκή , Hellēnikḗ ; [hellɛːnikɛ́ː] ) includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek ( c.  1400–1200 BC ), Dark Ages ( c.  1200–800 BC ),

4095-550: The aorist. Following Homer 's practice, the augment is sometimes not made in poetry , especially epic poetry. The augment sometimes substitutes for reduplication; see below. Almost all forms of the perfect, pluperfect, and future perfect reduplicate the initial syllable of the verb stem. (A few irregular forms of perfect do not reduplicate, whereas a handful of irregular aorists reduplicate.) The three types of reduplication are: Irregular duplication can be understood diachronically. For example, lambanō (root lab ) has

4186-419: The augment when it was word-initial. In verbs with a preposition as a prefix, the augment is placed not at the start of the word, but between the preposition and the original verb. For example, προσ(-)βάλλω (I attack) goes to προσ έ βαλoν in the aorist. However compound verbs consisting of a prefix that is not a preposition retain the augment at the start of the word: αὐτο(-)μολῶ goes to ηὐ τομόλησα in

4277-493: The clades Notopalaeognathae and Novaeratitae , the former defined in the PhyloCode by Sangster et al. (2022) as "the least inclusive crown clade containing Rhea americana , Tinamus major , and Apteryx australis ", while the latter also defined in the PhyloCode by Sangster et al. (2022) as "the least inclusive crown clade containing Apteryx australis and Casuarius casuarius ". Notopalaeognathae represents

4368-615: The dialect of Sparta ), and Northern Peloponnesus Doric (including Corinthian ). All the groups were represented by colonies beyond Greece proper as well, and these colonies generally developed local characteristics, often under the influence of settlers or neighbors speaking different Greek dialects. After the conquests of Alexander the Great in the late 4th century BC, a new international dialect known as Koine or Common Greek developed, largely based on Attic Greek , but with influence from other dialects. This dialect slowly replaced most of

4459-530: The dialects is: West vs. non-West Greek is the strongest-marked and earliest division, with non-West in subsets of Ionic-Attic (or Attic-Ionic) and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Often non-West is called 'East Greek'. Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian Greek had come under

4550-510: The divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period. They have the same general outline but differ in some of the detail. The only attested dialect from this period is Mycenaean Greek , but its relationship to the historical dialects and the historical circumstances of the times imply that the overall groups already existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not later than 1120 BC, at

4641-538: The donor than the other in a gene conversion event. In particular, GC-biased gene conversion tends to increase the GC-content of genomes, particularly in regions with higher recombination rates. There is also evidence for GC bias in the mismatch repair process. It is thought that this may be an adaptation to the high rate of methyl-cytosine deamination which can lead to C→T transitions. The dynamics of biased gene conversion resemble those of natural selection, in that

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4732-562: The estimated rates of molecular evolution are too slow, and that bird evolution actually accelerated during an adaptive radiation after the Cretaceous–Paleogene boundary (K–Pg boundary). Other authors questioned the monophyly of the Palaeognathae on various grounds, suggesting that they could be a hodgepodge of unrelated birds that have come to be grouped together because they are coincidentally flightless. Unrelated birds might have developed ratite-like anatomies multiple times around

4823-514: The expense of organismal fitness, resulting in intragenomic conflict . This is because there can be a selective advantage for selfish genetic elements in spite of a host cost. Examples of such selfish elements include transposable elements , meiotic drivers , and selfish mitochondria . Selection can be detected using the Ka/Ks ratio , the McDonald–Kreitman test . Rapid adaptive evolution

4914-614: The extinct flying paleognathe Lithornis was published by Leonard et al. in 2005. It is an articulated and nearly complete fossil from the early Eocene of Denmark, and thought to have the best preserved lithornithiform skull ever found. The authors concluded that Lithornis was a close sister taxon to tinamous, rather than ostriches, and that the lithornithiforms + tinamous were the most basal paleognaths. They concluded that all ratites, therefore, were monophyletic, descending from one common ancestor that became flightless. They also interpret

5005-474: The female has grayish brown feathers. They are unique among birds in that they retain only the third and fourth toe on each foot. Ostrich wings have claws, or unguals , on the first and second fingers (and, in some individuals, also on the third). Ostriches differ from other paleognaths in that they have a reduced vomer bone of the skull. Emus are 6 to 7.5 feet (1.8–2.3 m) in height and weigh 75 to 110 pounds (34–50 kg). They have short wings and

5096-695: The function of a protein. Directed evolution is the attempt to engineer proteins using methods inspired by molecular evolution. Change at one locus begins with a new mutation , which might become fixed due to some combination of natural selection , genetic drift , and gene conversion . Mutations are permanent, transmissible changes to the genetic material ( DNA or RNA ) of a cell or virus . Mutations result from errors in DNA replication during cell division and by exposure to radiation , chemicals, other environmental stressors, viruses , or transposable elements . When point mutations to just one base-pair of

5187-1028: The grouping containing the majority of ratites with the exception of ostriches , and the clade Novaeratitae was named to support the relationship between kiwis , cassowaries , emus , and the extinct elephant birds . Cloutier, A. et al . (2019) in their molecular study places ostriches as the basal lineage with the rhea as the next most basal. An alternative phylogeny was found by Kuhl, H. et al. (2020). In this treatment, all members of Palaeognathae are classified in Struthioniformes, but they are still shown as distinct orders here. Struthioniformes ( Ostriches ) [REDACTED] Rheiformes ( Rhea ) [REDACTED] Aepyornithiformes † ( Elephant bird ) [REDACTED] Apterygiformes ( Kiwi ) [REDACTED] Dinornithiformes † ( Moa ) [REDACTED] Tinamiformes ( Tinamous ) [REDACTED] Casuariidae ( Cassowary ) [REDACTED] Dromaiidae ( Emu ) [REDACTED] Other studies have suggested that

5278-474: The highest rates of speciation identified to date. Cilliate genomes house each gene in individual chromosomes. In addition to the nuclear genome , endosymbiont organelles contain their own genetic material. Mitochondrial and chloroplast DNA varies across taxa, but membrane-bound proteins , especially electron transport chain constituents are most often encoded in the organelle. Chloroplasts and mitochondria are maternally inherited in most species, as

5369-416: The introduction of variation (arrival bias). Selection can occur when an allele confers greater fitness , i.e. greater ability to survive or reproduce, on the average individual than carries it. A selectionist approach emphasizes e.g. that biases in codon usage are due at least in part to the ability of even weak selection to shape molecular evolution. Selection can also operate at the gene level at

5460-605: The kiwis to the Ratitae. Parker (1864) reported the similarities of the palates of the tinamous and ratites, but Huxley (1867) is more widely credited with this insight. Huxley still placed the tinamous with the Carinatae of Merrem because of their keeled sterna , and thought that they were most closely related to the Galliformes . Pycraft (1900) presented a major advance when he coined the term Palaeognathae. He rejected

5551-418: The lack of correlation between organism 'complexity' and genome size. Explanations for the so-called paradox are two-fold. First, repetitive genetic elements can comprise large portions of the genome for many organisms, thereby inflating DNA content of the haploid genome. Repetitive genetic elements are often descended from transposable elements . Secondly, the number of genes is not necessarily indicative of

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5642-411: The late 1960s. Neutral theory also provided a theoretical basis for the molecular clock , although this is not needed for the clock's validity. After the 1970s, nucleic acid sequencing allowed molecular evolution to reach beyond proteins to highly conserved ribosomal RNA sequences, the foundation of a reconceptualization of the early history of life . The Society for Molecular Biology and Evolution

5733-414: The latest Paleocene and afterwards, with ostriches diverging in the latest Paleocene, rheas in the early Eocene , kiwis (and presumably elephant birds ) very shortly after in the early Eocene, and finally Casuariiformes and tinamous (and presumably moas ) diverging from one another in the mid-Eocene. In the history of biology there have been many competing taxonomies of the birds now included in

5824-1166: The latter his term for tinamous, after the Tinamou genus Crypturellus ). The Palaeognathae are usually considered a superorder , but authors have treated them as a taxon as high as subclass (Stresemann 1927–1934) or as low as an order (Cracraft 1981 and the IUCN , which includes all paleognaths in an expanded Struthioniformes). Palaeognathae was defined in the PhyloCode by George Sangster and colleagues in 2022 as "the least inclusive crown clade containing Tinamus major and Struthio camelus ". Struthioniformes ( Ostriches ) [REDACTED] Rheiformes ( Rhea ) [REDACTED] Dinornithiformes † ( Moa ) [REDACTED] Tinamiformes ( Tinamous ) [REDACTED] Aepyornithiformes † ( Elephant bird ) [REDACTED] Apterygiformes ( Kiwi ) [REDACTED] Casuariidae ( Cassowary ) [REDACTED] Dromaiidae ( Emu ) [REDACTED] Cladogram based on Mitchell (2014) with some clade names after Yuri et al. (2013) Yuri et al. (2013) named

5915-576: The male incubates the eggs. The male may include in his nest the eggs of one female or more than one. He may also have eggs deposited in his nest by females that did not breed with him, in cases of nest parasitism . Only in ostriches and the great spotted kiwi does the female also assist in incubating the eggs. The tinamous of Central and South America are primarily terrestrial, though they fly weakly. Tinamous have very short tail feathers, giving them an almost tailless aspect. In general, they resemble galliform birds like quails and grouse. Tinamous have

6006-411: The medial border of the coracoid , attached there by a coraco–clavicular ligament. There is an obtuse angle between the scapula and coracoid , and the two bones fuse together to form a scapulocoracoid . Ratites have reduced and simplified wing structures and strong legs. Except in some rhea wing feathers, the barb filaments that make up the vanes of the feathers do not lock tightly together, giving

6097-445: The new gene performs a subset of the original ancestral functions. Retrotransposition duplicates genes by copying mRNA to DNA and inserting it into the genome. Retrogenes generally insert into new genomic locations, lack introns . and sometimes develop new expression patterns and functions. Chimeric genes form when duplication, deletion, or incomplete retrotransposition combine portions of two different coding sequences to produce

6188-491: The number of developmental stages or tissue types in an organism. An organism with few developmental stages or tissue types may have large numbers of genes that influence non-developmental phenotypes, inflating gene content relative to developmental gene families. Neutral explanations for genome size suggest that when population sizes are small, many mutations become nearly neutral. Hence, in small populations repetitive content and other 'junk' DNA can accumulate without placing

6279-508: The older dialects, although the Doric dialect has survived in the Tsakonian language , which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek . By about the 6th century AD, the Koine had slowly metamorphosed into Medieval Greek . Phrygian is an extinct Indo-European language of West and Central Anatolia , which

6370-734: The order of 10 per generation. Different frequencies of different types of mutations can play an important role in evolution via bias in the introduction of variation (arrival bias), contributing to parallelism, trends, and differences in the navigability of adaptive landscapes. Mutation bias makes systematic or predictable contributions to parallel evolution . Since the 1960s, genomic GC content has been thought to reflect mutational tendencies. Mutational biases also contribute to codon usage bias . Although such hypotheses are often associated with neutrality, recent theoretical and empirical results have established that mutational tendencies can influence both neutral and adaptive evolution via bias in

6461-517: The order of 10 per site per generation. Transitions (A ↔ G or C ↔ T) are more common than transversions ( purine (adenine or guanine)) ↔ pyrimidine (cytosine or thymine, or in RNA, uracil)). Perhaps the most common type of mutation in humans is a change in the length of a short tandem repeat (e.g., the CAG repeats underlying various disease-associated mutations). Such STR mutations may occur at rates on

6552-536: The organelles must pass through the egg . In a rare departure, some species of mussels are known to inherit mitochondria from father to son. New genes arise from several different genetic mechanisms including gene duplication , de novo gene birth , retrotransposition , chimeric gene formation, recruitment of non-coding sequence into an existing gene, and gene truncation. Gene duplication initially leads to redundancy. However, duplicated gene sequences can mutate to develop new functions or specialize so that

6643-612: The organism at a competitive disadvantage. There is little evidence to suggest that genome size is under strong widespread selection in multicellular eukaryotes. Genome size, independent of gene content, correlates poorly with most physiological traits and many eukaryotes, including mammals, harbor very large amounts of repetitive DNA. However, birds likely have experienced strong selection for reduced genome size, in response to changing energetic needs for flight. Birds, unlike humans, produce nucleated red blood cells, and larger nuclei lead to lower levels of oxygen transport. Bird metabolism

6734-550: The paleognath-like Limenavis , from Early Cretaceous Patagonia , as possible evidence of a Cretaceous and monophyletic origin for paleognaths. Mysterious large eggs from the Pliocene of Lanzarote in the Canary Islands have been attributed to ratites. An ambitious genomic analysis of the living birds was performed in 2007, and it contradicted Leonard et al. (2005). It found that tinamous are not primitive within

6825-500: The paleognathous ones, began diverging from one another in the Early Cretaceous . Benton (2005) summarized this and other molecular studies as implying that paleognaths should have arisen 110 to 120 million years ago in the Early Cretaceous . He points out, however, that there is no fossil record until 70 million years ago, leaving a 45 million year gap. He asks whether the paleognath fossils will be found one day, or whether

6916-498: The paleognaths, but among the most advanced. This requires multiple events of flightlessness within the paleognaths and partially refutes the Gondwana vicariance hypothesis (see below). The study looked at DNA sequences from 19 loci in 169 species. It recovered evidence that the paleognaths are one natural group ( monophyletic ), and that their divergence from other birds is the oldest divergence of any extant bird groups. It also placed

7007-487: The perfect stem eilēpha (not * lelēpha ) because it was originally slambanō , with perfect seslēpha , becoming eilēpha through compensatory lengthening. Reduplication is also visible in the present tense stems of certain verbs. These stems add a syllable consisting of the root's initial consonant followed by i . A nasal stop appears after the reduplication in some verbs. The earliest extant examples of ancient Greek writing ( c.  1450 BC ) are in

7098-462: The plumage a shaggier look and making it unnecessary to oil their feathers. Adult ratites have no preen gland ( uropygial gland ) that contains preening oil. Paleognaths as a whole tend to have proportionally small brains, and are among the living birds with the most limited cognitive abilities. Kiwis are exceptional, however, and have large brains comparable to those of parrots and songbirds , though evidence for similar levels of behaviour complexity

7189-413: The relationships between the four main groups of non-ostrich palaeognaths (Casuariiformes, Rheiformes, Apteryformes+Aepyornithformes and Tinamiformes+Dinornithformes) are an effective polytomy , with only slightly more support for Novaeratitae over the alternative hypotheses of Apterygiformes+Aepyornithformes being more closely related to Rheiformes or to Tinamiformes+Dinornithformes. This lineage containing

7280-536: The same species. Phylogenetic analysis of proteins has revealed how proteins evolve and change their structure and function over time. For example, ribonucleotide reductase (RNR) has evolved a multitude of structural and functional variants. Class I RNRs use a ferritin subunit and differ by the metal they use as cofactors. In class II RNRs, the thiyl radical is generated using an adenosylcobalamin cofactor and these enzymes do not require additional subunits (as opposed to class I which do). In class III RNRs,

7371-559: The similarities between the ratite orders are partly due to convergent evolution , and that the Palaeognathae are monophyletic , but the ratites are not. Beginning in 2010, DNA analysis studies have shown that tinamous are the sister group to extinct moa of New Zealand. A 2020 molecular study of all bird orders found paleognaths and neognaths to have diverged in the Late Cretaceous or earlier, before 70 million years ago. However, all modern paleognath orders only originated in

7462-447: The sister relationship between tinamous and moas was given the clade name Dinocrypturi , being named and defined in the PhyloCode by Sangster et al. (2022) as "the smallest clade containing Tinamus major and Dinornis novaezealandiae ". Paleognaths are named for a characteristic, complex architecture of the bones in the bony palate. Cracraft (1974) defined it with five characters. Paleognaths share similar pelvis anatomy. There

7553-591: The species. Changes in chromosome number can play a key role in speciation , as differing chromosome numbers can serve as a barrier to reproduction in hybrids. Human chromosome 2 was created from a fusion of two chimpanzee chromosomes and still contains central telomeres as well as a vestigial second centromere . Polyploidy , especially allopolyploidy, which occurs often in plants, can also result in reproductive incompatibilities with parental species. Agrodiatus blue butterflies have diverse chromosome numbers ranging from n=10 to n=134 and additionally have one of

7644-517: The syllabic script Linear B . Beginning in the 8th century BC, however, the Greek alphabet became standard, albeit with some variation among dialects. Early texts are written in boustrophedon style, but left-to-right became standard during the classic period. Modern editions of ancient Greek texts are usually written with accents and breathing marks , interword spacing , modern punctuation , and sometimes mixed case , but these were all introduced later. The beginning of Homer 's Iliad exemplifies

7735-459: The thiyl radical is generated using S-adenosylmethionine bound to a [ 4Fe-4S ] cluster. That is, within a single family of proteins numerous structural and functional mechanisms can evolve. In a proof-of-concept study, Bhattacharya and colleagues converted myoglobin , a non-enzymatic oxygen storage protein, into a highly efficient Kemp eliminase using only three mutations . This demonstrates that only few mutations are needed to radically change

7826-467: The time of the Dorian invasions —and that their first appearances as precise alphabetic writing began in the 8th century BC. The invasion would not be "Dorian" unless the invaders had some cultural relationship to the historical Dorians . The invasion is known to have displaced population to the later Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with

7917-422: The tinamous within the ratites, more derived than ostriches, or rheas and as a sister group to emus and kiwis, and this makes ratites paraphyletic . A related study addressed the issue of paleognath phylogeny exclusively. It used molecular analysis and looked at twenty unlinked nuclear genes. This study concluded that there were at least three events of flightlessness that produced the different ratite orders, that

8008-529: The world through convergent evolution . McDowell (1948) asserted that the similarities in the palate anatomy of paleognaths might actually be neoteny , or retained embryonic features. He noted that there were other features of the skull, such as the retention of sutures into adulthood, that were like those of juvenile birds. Thus, perhaps the characteristic palate was actually a frozen stage that many carinate bird embryos passed through during development. The retention of early developmental stages, then, may have been

8099-480: Was Aeolic. For example, fragments of the works of the poet Sappho from the island of Lesbos are in Aeolian. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric (including Cretan Doric ), Southern Peloponnesus Doric (including Laconian ,

8190-452: Was a pluricentric language , divided into many dialects. The main dialect groups are Attic and Ionic , Aeolic , Arcadocypriot , and Doric , many of them with several subdivisions. Some dialects are found in standardized literary forms in literature , while others are attested only in inscriptions. There are also several historical forms. Homeric Greek is a literary form of Archaic Greek (derived primarily from Ionic and Aeolic) used in

8281-570: Was founded in 1982. Molecular phylogenetics uses DNA , RNA , or protein sequences to resolve questions in systematics , i.e. about their correct scientific classification from the point of view of evolutionary history . The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree . Phylogenetic inference is conducted using data from DNA sequencing . This is aligned to identify which sites are homologous . A substitution model describes what patterns are expected to be common or rare. Sophisticated computational inference

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