This is an accepted version of this page
135-443: Theropoda ( / θ ɪəˈr ɒ p ə d ə / ; from ancient Greek θηρίο- ποδός [ θηρίον , ( therion ) "wild beast"; πούς , ποδός ( pous, podos ) "foot"]) whose members are known as theropods , is an extant dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous , although
270-695: A Compsognathus longipes fossil was found with a lizard in its stomach, and a Velociraptor mongoliensis specimen was found locked in combat with a Protoceratops andrewsi (a type of ornithischian dinosaur). The first confirmed non-carnivorous fossil theropods found were the therizinosaurs , originally known as "segnosaurs". First thought to be prosauropods , these enigmatic dinosaurs were later proven to be highly specialized, herbivorous theropods. Therizinosaurs possessed large abdomens for processing plant food, and small heads with beaks and leaf-shaped teeth. Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not
405-537: 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
540-489: A branch and stays perfectly still, with only its eyes moving. When an insect lands, the chameleon focuses its eyes on the target and slowly moves toward it before projecting its long sticky tongue which, when hauled back, brings the attached prey with it. Geckos feed on crickets , beetles, termites and moths . Termites are an important part of the diets of some species of Autarchoglossa, since, as social insects , they can be found in large numbers in one spot. Ants may form
675-529: A computed tomography scan and 3D reconstruction software. These finds are of evolutionary significance because they help document the emergence of the neurology of modern birds from that of earlier reptiles. An increase in the proportion of the brain occupied by the cerebrum seems to have occurred with the advent of the Coelurosauria and "continued throughout the evolution of maniraptorans and early birds." Studies show that theropods had very sensitive snouts. It
810-422: A doubled clitoris. The majority of species are oviparous (egg laying). The female deposits the eggs in a protective structure like a nest or crevice or simply on the ground. Depending on the species, clutch size can vary from 4–5 percent of the females body weight to 40–50 percent and clutches range from one or a few large eggs to dozens of small ones. In most lizards, the eggs have leathery shells to allow for
945-414: A group including the relatively derived theropod subgroups Ceratosauria and Tetanurae , and excluding coelophysoids . However, most later researchers have used it to denote a broader group. Neotheropoda was first defined as a clade by Paul Sereno in 1998 as Coelophysis plus modern birds , which includes almost all theropods except the most primitive species. Dilophosauridae was formerly considered
1080-452: A higher probability of being within the Theropoda may share more specific traits, such as a prominent promaxillary fenestra, cervical vertebrae with pleurocoels in the anterior part of the centrum leading to a more pneumatic neck, five or more sacral vertebrae, enlargement of the carpal bone, and a distally concave portion of the tibia, among a few other traits found throughout the skeleton. Like
1215-472: A lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between 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
1350-419: A lesser degree. Pamphylian Greek , spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either 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
1485-436: A lesser extent amphisbaenians ), encompassing over 7,000 species , ranging across all continents except Antarctica , as well as most oceanic island chains . The grouping is paraphyletic as some lizards are more closely related to snakes than they are to other lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3-meter-long Komodo dragon . Most lizards are quadrupedal, running with
SECTION 10
#17328444993511620-555: A limited ability to regulate their body temperature, and must seek out and bask in sunlight to gain enough heat to become fully active. Thermoregulation behavior can be beneficial in the short term for lizards as it allows the ability to buffer environmental variation and endure climate warming. In high altitudes, the Podarcis hispaniscus responds to higher temperature with a darker dorsal coloration to prevent UV-radiation and background matching. Their thermoregulatory mechanisms also allow
1755-791: A number of theropod groups evolved to become herbivores and omnivores . Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago ( Ma ) and included the majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous , about 66 Ma. In the Jurassic , birds evolved from small specialized coelurosaurian theropods, and are today represented by about 11,000 living species. Various synapomorphies for Theropoda have been proposed based on which taxa are included in
1890-567: A pouch beneath its eyes, to a distance of about two metres (6.6 feet); the blood tastes foul to these attackers. The closest living relatives of lizards are rhynchocephalians , a once diverse order of reptiles, of which is there is now only one living species, the tuatara of New Zealand. Some reptiles from the Early and Middle Triassic , like Sophineta and Megachirella , are suggested to be stem-group squamates, more closely related to modern lizards than rhynchocephalians, however, their position
2025-463: A predator that has caught them; attempt to outrun the rattlesnake , which does not pursue prey; but stay still, relying on their cryptic coloration, for Masticophis whip snakes which can catch even swift prey. If caught, some species such as the greater short-horned lizard puff themselves up, making their bodies hard for a narrow-mouthed predator like a whip snake to swallow. Finally, horned lizards can squirt blood at cat and dog predators from
2160-543: 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
2295-430: A prominent part of the diet of some lizards, particularly among the lacertas. Horned lizards are also well known for specializing on ants. Due to their small size and indigestible chitin , ants must be consumed in large amounts, and ant-eating lizards have larger stomachs than even herbivorous ones. Species of skink and alligator lizards eat snails and their power jaws and molar-like teeth are adapted for breaking
2430-415: A relationships between tooth size and skull length and also a comparison of the degree of wear of the teeth of non-avian theropods and modern lepidosaurs , it is concluded that theropods had lips that protected their teeth from the outside. Visually, the snouts of such theropods as Daspletosaurus had more similarities with lizards than crocodilians, which lack lips. Tyrannosaurus was for many decades
2565-427: A result of growth or seasonal changes, which can be used to approximate age at the time of death. However, the amount of rings in a skeleton can vary from bone to bone, and old rings can also be lost at advanced age, so scientists need to properly control these two possibly confounding variables. Body mass is harder to determine as bone mass only represents a small proportion of the total body mass of animals. One method
2700-608: 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 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
2835-410: A shift in the use of the forearm, with greater flexibility at the shoulder allowing the arm to be raised towards the horizontal plane, and to even greater degrees in flying birds. However, in coelurosaurs, such as ornithomimosaurs and especially dromaeosaurids, the hand itself had lost most flexibility, with highly inflexible fingers. Dromaeosaurids and other maniraptorans also showed increased mobility at
SECTION 20
#17328444993512970-475: A side-branch of more advanced theropods, they may have been ancestral to all other theropods (which would make them a paraphyletic group). Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs , and is the only group of theropods that survived the Triassic–Jurassic extinction event . Neotheropoda was named by R.T. Bakker in 1986 as
3105-472: A single clade , the Toxicofera ). However, most of these putative venom genes were "housekeeping genes" found in all cells and tissues, including skin and cloacal scent glands. The genes in question may thus be evolutionary precursors of venom genes. Recent studies (2013 and 2014) on the lung anatomy of the savannah monitor and green iguana found them to have a unidirectional airflow system, which involves
3240-423: A single unit with little flexibility. In theropods and prosauropods, the only way for the palm to face the ground would have been by lateral splaying of the entire forelimb, as in a bird raising its wing. In carnosaurs like Acrocanthosaurus , the hand itself retained a relatively high degree of flexibility, with mobile fingers. This was also true of more basal theropods, such as herrerasaurs . Coelurosaurs showed
3375-468: A small clade within Neotheropoda, but was later considered to be paraphyletic . By the Early Jurassic , all non-averostran neotheropods had gone extinct. Averostra (or "bird snouts") is a clade within Neotheropoda that includes most theropod dinosaurs , namely Ceratosauria and Tetanurae . It represents the only group of post-Early Jurassic theropods. One important diagnostic feature of Averostra
3510-700: A species affects the structure of territories, for example, rock lizards have territories atop rocky outcrops. Some species may aggregate in groups, enhancing vigilance and lessening the risk of predation for individuals, particularly for juveniles. Agonistic behaviour typically occurs between sexually mature males over territory or mates and may involve displays, posturing, chasing, grappling and biting. Lizards signal both to attract mates and to intimidate rivals. Visual displays include body postures and inflation, push-ups, bright colours, mouth gapings and tail waggings. Male anoles and iguanas have dewlaps or skin flaps which come in various sizes, colours and patterns and
3645-609: A standard subject of study in educational institutions of the Western world since the Renaissance . This article primarily contains information about 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
3780-474: A strong side-to-side motion. Some lineages (known as " legless lizards ") have secondarily lost their legs, and have long snake-like bodies. Some lizards, such as the forest-dwelling Draco , are able to glide. They are often territorial , the males fighting off other males and signalling, often with bright colours, to attract mates and to intimidate rivals. Lizards are mainly carnivorous, often being sit-and-wait predators ; many smaller species eat insects, while
3915-423: A variety of different camouflage methods . Many lizards are disruptively patterned . In some species, such as Aegean wall lizards , individuals vary in colour, and select rocks which best match their own colour to minimise the risk of being detected by predators. The Moorish gecko is able to change colour for camouflage: when a light-coloured gecko is placed on a dark surface, it darkens within an hour to match
4050-510: 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
4185-405: A wide variety of tasks (see below). In modern birds, the body is typically held in a somewhat upright position, with the upper leg (femur) held parallel to the spine and with the forward force of locomotion generated at the knee. Scientists are not certain how far back in the theropod family tree this type of posture and locomotion extends. Non-avian theropods were first recognized as bipedal during
Theropoda - Misplaced Pages Continue
4320-556: Is a literary form of Archaic Greek (derived primarily from Ionic and Aeolic) used in 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
4455-418: 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
4590-467: Is also believed to have also been different among different families. The spinosaurids could have used their powerful forelimbs to hold fish. Some small maniraptorans such as scansoriopterygids are believed to have used their forelimbs to climb in trees . The wings of modern birds are used primarily for flight, though they are adapted for other purposes in certain groups. For example, aquatic birds such as penguins use their wings as flippers. Contrary to
4725-644: Is called 'East Greek'. Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian Greek had come under 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
4860-448: 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
4995-569: Is disputed, with some studies recovering them as less closely related to squamates than rhynchocephalians are. The oldest undisputed lizards date to the Middle Jurassic, from remains found In Europe, Asia and North Africa. Lizard morphological and ecological diversity substantially increased over the course of the Cretaceous . In the Palaeogene , lizard body sizes in North America peaked during
5130-466: Is known as the extant-scaling (ES) approach. A second method, known as the volumetric-density (VD) approach, uses full-scale models of skeletons to make inferences about potential mass. The ES approach is better for wide-range studies including many specimens and doesn't require as much of a complete skeleton as the VD approach, but the VD approach allows scientists to better answer more physiological questions about
5265-666: Is known to occur in various species of whiptail lizards . Parthenogenesis was also recorded in species that normally reproduce sexually. A captive female Komodo dragon produced a clutch of eggs, despite being separated from males for over two years. Sex determination in lizards can be temperature-dependent . The temperature of the eggs' micro-environment can determine the sex of the hatched young: low temperature incubation produces more females while higher temperatures produce more males. However, some lizards have sex chromosomes and both male heterogamety (XY and XXY) and female heterogamety (ZW) occur. A significant component of aging in
5400-510: Is suggested they might have been used for temperature detection, feeding behavior, and wave detection. Shortened forelimbs in relation to hind legs was a common trait among theropods, most notably in the abelisaurids (such as Carnotaurus ) and the tyrannosaurids (such as Tyrannosaurus ). This trait was, however, not universal: spinosaurids had well developed forelimbs, as did many coelurosaurs. The relatively robust forelimbs of one genus, Xuanhanosaurus , led D. Zhiming to suggest that
5535-564: Is the absence of the fifth metacarpal. Other saurischians retained this bone, albeit in a significantly reduced form. The somewhat more advanced ceratosaurs (including Ceratosaurus and Carnotaurus ) appeared during the Early Jurassic and continued through to the Late Jurassic in Laurasia . They competed alongside their more anatomically advanced tetanuran relatives and—in the form of
Theropoda - Misplaced Pages Continue
5670-406: Is to measure the circumference of the femur, which in non-avian theropod dinosaurs has been shown to be a relatively proportional to quadrupedal mammals, and use this measurement as a function of body weight, as the proportions of long bones like the femur grow proportionately with body mass. The method of using extant animal bone proportion to body mass ratios to make predictions about extinct animals
5805-406: Is used to signify groups with no living members. The following family tree illustrates a synthesis of the relationships of the major theropod groups based on various studies conducted in the 2010s. † Herrerasauridae [REDACTED] † Eoraptor † Eodromaeus † Daemonosaurus Ancient Greek Ancient Greek ( Ἑλληνῐκή , Hellēnikḗ ; [hellɛːnikɛ́ː] ) includes
5940-592: The Allosauroidea (the diverse carcharodontosaurs ) and the Coelurosauria (a very large and diverse dinosaur group including the birds). Thus, during the late Jurassic, there were no fewer than four distinct lineages of theropods—ceratosaurs, megalosaurs, allosaurs, and coelurosaurs—preying on the abundance of small and large herbivorous dinosaurs. All four groups survived into the Cretaceous, and three of those—the ceratosaurs, coelurosaurs, and allosaurs—survived to end of
6075-647: The Coelophysoidea . The coelophysoids were a group of widely distributed, lightly built and potentially gregarious animals. They included small hunters like Coelophysis and Camposaurus . These successful animals continued from the Late Carnian (early Late Triassic) through to the Toarcian (late Early Jurassic ). Although in the early cladistic classifications they were included under the Ceratosauria and considered
6210-745: The Greek region of Macedonia during the last decades has brought to light documents, among which the first texts written in Macedonian , such as 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
6345-584: The abelisaur lineage—lasted to the end of the Cretaceous in Gondwana . The Tetanurae are more specialised again than the ceratosaurs. They are subdivided into the basal Megalosauroidea (alternately Spinosauroidea ) and the more derived Avetheropoda . Megalosauridae were primarily Middle Jurassic to Early Cretaceous predators, and their spinosaurid relatives' remains are mostly from Early and Middle Cretaceous rocks. Avetheropoda, as their name indicates, were more closely related to birds and are again divided into
6480-405: The bee hummingbird ( Mellisuga helenae ) is smallest at 1.9 g and 5.5 cm (2.2 in) long. Recent theories propose that theropod body size shrank continuously over a period of 50 million years, from an average of 163 kilograms (359 lb) down to 0.8 kilograms (1.8 lb), eventually evolving into over 11,000 species of modern birds . This was based on evidence that theropods were
6615-474: The clade Tetanurae for one branch of a basic theropod split with another group, the Ceratosauria. As more information about the link between dinosaurs and birds came to light, the more bird-like theropods were grouped in the clade Maniraptora (also named by Gauthier in 1986). These new developments also came with a recognition among most scientists that birds arose directly from maniraptoran theropods and, on
6750-740: The coelurosaurs , feathers may have been confined to the young, smaller species, or limited parts of the animal. Many larger theropods had skin covered in small, bumpy scales. In some species, these were interspersed with larger scales with bony cores, or osteoderms . This type of skin is best known in the ceratosaur Carnotaurus , which has been preserved with extensive skin impressions. The coelurosaur lineages most distant from birds had feathers that were relatively short and composed of simple, possibly branching filaments. Simple filaments are also seen in therizinosaurs, which also possessed large, stiffened "quill"-like feathers. More fully feathered theropods, such as dromaeosaurids , usually retain scales only on
6885-406: The common basilisk , can run across water. Lizards make use of their senses of sight , touch , olfaction and hearing like other vertebrates . The balance of these varies with the habitat of different species; for instance, skinks that live largely covered by loose soil rely heavily on olfaction and touch, while geckos depend largely on acute vision for their ability to hunt and to evaluate
SECTION 50
#17328444993517020-524: The cranium and forelimb, with injuries occurring in about equal frequency at each site. Most pathologies preserved in theropod fossils are the remains of injuries like fractures, pits, and punctures, often likely originating with bites. Some theropod paleopathologies seem to be evidence of infections , which tended to be confined only to small regions of the animal's body. Evidence for congenital malformities have also been found in theropod remains. Such discoveries can provide information useful for understanding
7155-626: The furcula (wishbone), pneumatized bones, brooding of the eggs , and (in coelurosaurs, at least) feathers . O. C. Marsh coined the name Theropoda (meaning "beast feet") in 1881. Marsh initially named Theropoda as a suborder to include the family Allosauridae , but later expanded its scope, re-ranking it as an order to include a wide array of "carnivorous" dinosaur families, including Megalosauridae , Compsognathidae , Ornithomimidae , Plateosauridae and Anchisauridae (now known to be herbivorous sauropodomorphs ) and Hallopodidae (subsequently revealed as relatives of crocodilians). Due to
7290-592: The geckos , anoles , and chameleons , have modified the scales under their toes to form adhesive pads , highly prominent in the first two groups. The pads are composed of millions of tiny setae (hair-like structures) which fit closely to the substrate to adhere using van der Waals forces ; no liquid adhesive is needed. In addition, the toes of chameleons are divided into two opposed groups on each foot ( zygodactyly ), enabling them to perch on branches as birds do. Aside from legless lizards , most lizards are quadrupedal and move using gaits with alternating movement of
7425-485: The microflora necessary for their transition to a plant-based diet. Perhaps the most herbivorous species is the marine iguana which dives 15 m (49 ft) to forage for algae , kelp and other marine plants. Some non-herbivorous species supplement their insect diet with fruit, which is easily digested. Lizards have a variety of antipredator adaptations , including running and climbing, venom , camouflage , tail autotomy , and reflex bleeding . Lizards exploit
7560-501: 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)
7695-451: The spinosaurids ) appear to have specialized in catching fish. Diet is largely deduced by the tooth morphology , tooth marks on bones of the prey, and gut contents. Some theropods, such as Baryonyx , Lourinhanosaurus , ornithomimosaurs, and birds, are known to use gastroliths , or gizzard-stones. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Others are pachydont or folidont depending on
7830-479: The 19th century, before their relationship to birds was widely accepted. During this period, theropods such as carnosaurs and tyrannosaurids were thought to have walked with vertical femurs and spines in an upright, nearly erect posture, using their long, muscular tails as additional support in a kangaroo-like tripodal stance. Beginning in the 1970s, biomechanical studies of extinct giant theropods cast doubt on this interpretation. Studies of limb bone articulation and
7965-1031: 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"):
8100-490: 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
8235-544: 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, Lizard Sauria Macartney , 1802 Lizard is the common name used for all squamate reptiles other than snakes (and to
SECTION 60
#17328444993518370-460: The Early Cretaceous. A few palaeontologists, such as Gregory S. Paul , have suggested that some or all of these advanced theropods were actually descended from flying dinosaurs or proto-birds like Archaeopteryx that lost the ability to fly and returned to a terrestrial habitat. The evolution of birds from other theropod dinosaurs has also been reported, with some of the linking features being
8505-653: The Komodo dragon can kill prey as large as water buffalo . Dragons are prolific scavengers , and a single decaying carcass can attract several from 2 km (1.2 mi) away. A 50 kg (110 lb) dragon is capable of consuming a 31 kg (68 lb) carcass in 17 minutes. Around 2 percent of lizard species, including many iguanids, are herbivores. Adults of these species eat plant parts like flowers, leaves, stems and fruit, while juveniles eat more insects. Plant parts can be hard to digest, and, as they get closer to adulthood, juvenile iguanas eat faeces from adults to acquire
8640-432: The Komodo eats mammals as big as water buffalo . Lizards make use of a variety of antipredator adaptations , including venom , camouflage , reflex bleeding , and the ability to sacrifice and regrow their tails . The adult length of species within the suborder ranges from a few centimeters for chameleons such as Brookesia micra and geckos such as Sphaerodactylus ariasae to nearly 3 m (10 ft) in
8775-667: The Order Saurischia into two suborders, Theropoda and Sauropoda. This basic division has survived into modern palaeontology, with the exception of, again, the Prosauropoda, which Romer included as an infraorder of theropods. Romer also maintained a division between Coelurosauria and Carnosauria (which he also ranked as infraorders). This dichotomy was upset by the discovery of Deinonychus and Deinocheirus in 1969, neither of which could be classified easily as "carnosaurs" or "coelurosaurs". In light of these and other discoveries, by
8910-460: The Tetanurae and Ceratosauria. While some used to consider coelophysoids and ceratosaurs to be within the same group due to features such as a fused hip, later studies showed that it is more likely that these were features ancestral to neotheropods and were lost in basal tetanurans. Averostrans and their close relatives are united via the complete loss of any digit V remnants, fewer teeth in the maxilla,
9045-508: The abandonment of ranks in cladistic classification, with the re-evaluation of birds as a subset of theropod dinosaurs that survived the Mesozoic extinctions and lived into the present. The following is a simplified classification of theropod groups based on their evolutionary relationships, and organized based on the list of Mesozoic dinosaur species provided by Holtz. A more detailed version can be found at dinosaur classification . The dagger (†)
9180-439: The air moving in a loop through the lungs when breathing. This was previously thought to only exist in the archosaurs ( crocodilians and birds ). This may be evidence that unidirectional airflow is an ancestral trait in diapsids . As with all amniotes, lizards rely on internal fertilisation and copulation involves the male inserting one of his hemipenes into the female's cloaca . Female lizards also have hemiclitorises ,
9315-541: The animal might have been quadrupedal. However, this is no longer thought to be likely. The hands are also very different among the different groups. The most common form among non-avian theropods is an appendage consisting of three fingers; the digits I, II and III (or possibly II, III and IV ), with sharp claws. Some basal theropods, like most Ceratosaurians , had four digits, and also a reduced metacarpal V (e.g. Dilophosaurus ). The majority of tetanurans had three, but some had even fewer. The forelimbs' scope of use
9450-458: The animal, such as locomotion and center of gravity. The current consensus is that non-avian theropods didn't exhibit a group wide growth rate, but instead had varied rates depending on their size. However, all non-avian theropods had faster growth rates than extant reptiles, even when modern reptiles are scaled up to the large size of some non-avian theropods. As body mass increases, the relative growth rate also increases. This trend may be due to
9585-550: 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
9720-419: 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
9855-483: The avian theropods (birds). However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed even in more basal lineages. All early finds of theropod fossils showed them to be primarily carnivorous . Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, and some specimens even showed direct evidence of predatory behavior. For example,
9990-556: The case of the largest living varanid lizard, the Komodo dragon . Most lizards are fairly small animals. Lizards typically have rounded torsos, elevated heads on short necks, four limbs and long tails, although some are legless. Lizards and snakes share a movable quadrate bone , distinguishing them from the rhynchocephalians , which have more rigid diapsid skulls . Some lizards such as chameleons have prehensile tails, assisting them in climbing among vegetation. As in other reptiles,
10125-438: 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 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
10260-611: 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
10395-499: The different parts of theropod anatomy. The most common sites of preserved injury and disease in theropod dinosaurs are the ribs and tail vertebrae . Despite being abundant in ribs and vertebrae, injuries seem to be "absent... or very rare" on the bodies' primary weight supporting bones like the sacrum , femur , and tibia . The lack of preserved injuries in these bones suggests that they were selected by evolution for resistance to breakage. The least common sites of preserved injury are
10530-500: The distance to their prey before striking. Monitor lizards have acute vision, hearing, and olfactory senses. Some lizards make unusual use of their sense organs: chameleons can steer their eyes in different directions, sometimes providing non-overlapping fields of view, such as forwards and backwards at once. Lizards lack external ears, having instead a circular opening in which the tympanic membrane (eardrum) can be seen. Many species rely on hearing for early warning of predators, and flee at
10665-419: The early sauropodomorphs, the second digit in a theropod's hand is enlarged. Theropods also have a very well developed ball and socket joint near their neck and head. Most theropods belong to the clade Neotheropoda, characterized by the reduction of several foot bones, thus leaving three toed footprints on the ground when they walk (tridactyl feet). Digit V was reduced to a remnant early in theropod evolution and
10800-586: The environment. The chameleons in general use their ability to change their coloration for signalling rather than camouflage, but some species such as Smith's dwarf chameleon do use active colour change for camouflage purposes. The flat-tail horned lizard 's body is coloured like its desert background, and is flattened and fringed with white scales to minimise its shadow. Many lizards, including geckos and skinks , are capable of shedding their tails ( autotomy ). The detached tail, sometimes brilliantly coloured, continues to writhe after detaching, distracting
10935-599: The evolutionary history of the processes of biological development. Unusual fusions in cranial elements or asymmetries in the same are probably evidence that one is examining the fossils of an extremely old individual rather than a diseased one. The trackway of a swimming theropod, the first in China of the ichnogenus named Characichnos , was discovered at the Feitianshan Formation in Sichuan. These new swim tracks support
11070-454: The exchange of water, although more arid-living species have calcified shells to retain water. Inside the eggs, the embryos use nutrients from the yolk . Parental care is uncommon and the female usually abandons the eggs after laying them. Brooding and protection of eggs do occur in some species. The female prairie skink uses respiratory water loss to maintain the humidity of the eggs which facilitates embryonic development. In lace monitors ,
11205-658: The expansion of the dewlap as well as head-bobs and body movements add to the visual signals. Some species have deep blue dewlaps and communicate with ultraviolet signals. Blue-tongued skinks will flash their tongues as a threat display . Chameleons are known to change their complex colour patterns when communicating, particularly during agonistic encounters. They tend to show brighter colours when displaying aggression and darker colours when they submit or "give up". Several gecko species are brightly coloured; some species tilt their bodies to display their coloration. In certain species, brightly coloured males turn dull when not in
11340-526: The extant non-avian reptiles. Archosauromorpha [REDACTED] [REDACTED] Pantestudines [REDACTED] † Kuehneosauridae [REDACTED] Rhynchocephalia [REDACTED] Squamata [REDACTED] Both the snakes and the Amphisbaenia (worm lizards) are clades deep within the Squamata (the smallest clade that contains all the lizards), so "lizard" is paraphyletic . The cladogram
11475-410: The feet. Some species may have mixed feathers elsewhere on the body as well. Scansoriopteryx preserved scales near the underside of the tail, and Juravenator may have been predominantly scaly with some simple filaments interspersed. On the other hand, some theropods were completely covered with feathers, such as the troodontid Anchiornis , which even had feathers on the feet and toes. Based on
11610-468: The first known dromaeosaurid ( Dromaeosaurus albertensis ) in 1922, W. D. Matthew and Barnum Brown became the first paleontologists to exclude prosauropods from the carnivorous dinosaurs, and attempted to revive the name "Goniopoda" for that group, but other scientists did not accept either of these suggestions. In 1956, "Theropoda" came back into use—as a taxon containing the carnivorous dinosaurs and their descendants—when Alfred Romer re-classified
11745-663: 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 ), 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
11880-484: The group. For example, a 1999 paper by Paul Sereno suggests that theropods are characterized by traits such as an ectopterygoid fossa (a depression around the ectopterygoid bone), an intramandibular joint located within the lower jaw, and extreme internal cavitation within the bones. However, since taxa like Herrerasaurus may not be theropods, these traits may have been more widely distributed among early saurischians rather than being unique to theropods. Instead, taxa with
12015-524: The heaviest theropods known to science. It is still not clear why these animals grew so heavy and bulky compared to the land predators that came before and after them. The largest extant theropod is the common ostrich , up to 2.74 m (9 ft) tall and weighing between 90 and 130 kg (200 - 290 lb). The smallest non-avian theropod known from adult specimens is the troodontid Anchiornis huxleyi , at 110 grams in weight and 34 centimeters (1 ft) in length. When modern birds are included,
12150-556: 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 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
12285-472: 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 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
12420-608: The hypothesis that theropods were adapted to swimming and capable of traversing moderately deep water. Dinosaur swim tracks are considered to be rare trace fossils, and are among a class of vertebrate swim tracks that also include those of pterosaurs and crocodylomorphs . The study described and analyzed four complete natural molds of theropod foot prints that are now stored at the Huaxia Dinosaur Tracks Research and Development Center (HDT). These dinosaur footprints were in fact claw marks, which suggest that this theropod
12555-418: The knee was normally strongly flexed in all theropods while walking, even giants like the tyrannosaurids. It is likely that a wide range of body postures, stances, and gaits existed in the many extinct theropod groups. Although rare, complete casts of theropod endocrania are known from fossils. Theropod endocrania can also be reconstructed from preserved brain cases without damaging valuable specimens by using
12690-542: The largest known theropod and best known to the general public. Since its discovery, however, a number of other giant carnivorous dinosaurs have been described, including Spinosaurus , Carcharodontosaurus , and Giganotosaurus . The original Spinosaurus specimens (as well as newer fossils described in 2006) support the idea that Spinosaurus was probably 3 meters longer than Tyrannosaurus , though Tyrannosaurus might have been more massive than Spinosaurus . Specimens such as Sue and Scotty are both estimated to be
12825-462: The largest living land animal today, the African elephant , which is characterized by a rapid period of growth until maturity, subsequently followed by slowing growth in adulthood. As a hugely diverse group of animals, the posture adopted by theropods likely varied considerably between various lineages through time. All known theropods are bipedal , with the forelimbs reduced in length and specialized for
12960-456: The late 1970s Rinchen Barsbold had created a new series of theropod infraorders: Coelurosauria, Deinonychosauria , Oviraptorosauria , Carnosauria, Ornithomimosauria, and Deinocheirosauria . With the advent of cladistics and phylogenetic nomenclature in the 1980s, and their development in the 1990s and 2000s, a clearer picture of theropod relationships began to emerge. Jacques Gauthier named several major theropod groups in 1986, including
13095-489: The lizard to maintain their ideal body temperature for optimal mobility. Most social interactions among lizards are between breeding individuals. Territoriality is common and is correlated with species that use sit-and-wait hunting strategies. Males establish and maintain territories that contain resources that attract females and which they defend from other males. Important resources include basking, feeding, and nesting sites as well as refuges from predators. The habitat of
13230-553: The male tokay gecko is heard as "tokay-tokay!". Tactile communication involves individuals rubbing against each other, either in courtship or in aggression. Some chameleon species communicate with one another by vibrating the substrate that they are standing on, such as a tree branch or leaf. Lizards are found worldwide, excluding the far north and Antarctica, and some islands. They can be found in elevations from sea level to 5,000 m (16,000 ft). They prefer warmer, tropical climates but are adaptable and can live in all but
13365-495: The middle of the period. Mosasaurs likely evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous . Dolichosauridae is a family of Late Cretaceous aquatic varanoid lizards closely related to the mosasaurs. The position of the lizards and other Squamata among the reptiles was studied using fossil evidence by Rainer Schoch and Hans-Dieter Sues in 2015. Lizards form about 60% of
13500-666: The most extreme environments. Lizards also exploit a number of habitats; most primarily live on the ground, but others may live in rocks, on trees, underground and even in water. The marine iguana is adapted for life in the sea. The majority of lizard species are predatory and the most common prey items are small, terrestrial invertebrates, particularly insects . Many species are sit-and-wait predators though others may be more active foragers. Chameleons prey on numerous insect species, such as beetles , grasshoppers and winged termites as well as spiders . They rely on persistence and ambush to capture these prey. An individual perches on
13635-543: The mouth, and is often long. In the beaded lizards, whiptails and monitor lizards, the tongue is forked and used mainly or exclusively to sense the environment, continually flicking out to sample the environment, and back to transfer molecules to the vomeronasal organ responsible for chemosensation, analogous to but different from smell or taste. In geckos, the tongue is used to lick the eyes clean: they have no eyelids. Chameleons have very long sticky tongues which can be extended rapidly to catch their insect prey. Three lineages,
13770-403: The movement of the tooth row further down the maxilla and a lacrimal fenestra. Averostrans also share features in their hips and teeth. Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered a characteristic exclusive to
13905-657: The need to reach the size required for reproductive maturity . For example, one of the smallest known theropods was Microraptor zhaoianus , which had a body mass of 200 grams, grew at a rate of approximately 0.33 grams per day. A comparable reptile of the same size grows at half of this rate. The growth rates of medium-sized non-avian theropods (100–1000 kg) approximated those of precocial birds, which are much slower than altricial birds. Large theropods (1500–3500 kg) grew even faster, similar to rates displayed by eutherian mammals. The largest non-avian theropods, like Tyrannosaurus rex had similar growth dynamics to
14040-499: 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
14175-492: The oldest known bird, Archaeopteryx ), the bird-like troodontids and oviraptorosaurs, the ornithomimosaurs (or "ostrich Dinosaurs"), the strange giant-clawed herbivorous therizinosaurs, and the avialans, which include modern birds and is the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event . While the roots of these various groups are found in the Middle Jurassic, they only became abundant during
14310-490: The only dinosaurs to get continuously smaller, and that their skeletons changed four times as fast as those of other dinosaur species. In order to estimate the growth rates of theropods, scientists need to calculate both age and body mass of a dinosaur. Both of these measures can only be calculated through fossilized bone and tissue , so regression analysis and extant animal growth rates as proxies are used to make predictions. Fossilized bones exhibit growth rings that appear as
14445-407: The only early members of this group to abandon carnivory. Several other lineages of early maniraptorans show adaptations for an omnivorous diet, including seed-eating (some troodontids ) and insect-eating (many avialans and alvarezsaurs ). Oviraptorosaurs , ornithomimosaurs and advanced troodontids were likely omnivorous as well, and some early theropods (such as Masiakasaurus knopfleri and
14580-441: The only venomous lizards. However, several species of monitor lizards, including the Komodo dragon , produce powerful venom in their oral glands . Lace monitor venom, for instance, causes swift loss of consciousness and extensive bleeding through its pharmacological effects, both lowering blood pressure and preventing blood clotting . Nine classes of toxin known from snakes are produced by lizards. The range of actions provides
14715-460: The painted dragon lizard Ctenophorus pictus is fading breeding colors. By manipulating superoxide levels (using a superoxide dismutase mimetic) it was shown that this fading coloration is likely due to gradual loss with lizard age of an innate capacity for antioxidation due to increasing DNA damage . The majority of lizard species are active during the day , though some are active at night , notably geckos. As ectotherms , lizards have
14850-418: The palms faced the ground or backwards towards the legs. In humans, pronation is achieved by motion of the radius relative to the ulna (the two bones of the forearm). In saurischian dinosaurs, however, the end of the radius near the elbow was actually locked into a groove of the ulna, preventing any movement. Movement at the wrist was also limited in many species, forcing the entire forearm and hand to move as
14985-399: The past considered the herrerasaurians to be members of Theropoda, while other theorized the group to be basal saurischians, and may even have evolved prior to the saurischian-ornithischian split. Cladistic analysis following the discovery of Tawa , another Triassic dinosaur, suggests the herrerasaurs likely were early theropods. The earliest and most primitive unambiguous theropods are
15120-487: 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
15255-531: The period, where they were geographically separate, the ceratosaurs and allosaurs in Gondwana, and the coelurosaurs in Laurasia. Of all the theropod groups, the coelurosaurs were by far the most diverse. Some coelurosaur groups that flourished during the Cretaceous were the tyrannosaurids (including Tyrannosaurus ), the dromaeosaurids (including Velociraptor and Deinonychus , which are remarkably similar in form to
15390-401: The potential for new medicinal drugs based on lizard venom proteins . Genes associated with venom toxins have been found in the salivary glands of a wide range of lizards, including species traditionally thought of as non-venomous, such as iguanas and bearded dragons. This suggests that these genes evolved in the common ancestor of lizards and snakes , some 200 million years ago (forming
15525-515: The predator's attention from the fleeing prey. Lizards partially regenerate their tails over a period of weeks. Some 326 genes are involved in regenerating lizard tails. The fish-scale gecko Geckolepis megalepis sheds patches of skin and scales if grabbed. Many lizards attempt to escape from danger by running to a place of safety; for example, wall lizards can run up walls and hide in holes or cracks. Horned lizards adopt differing defences for specific predators. They may play dead to deceive
15660-478: The presence of rivals or females. While it is usually males that display, in some species females also use such communication. In the bronze anole , head-bobs are a common form of communication among females, the speed and frequency varying with age and territorial status. Chemical cues or pheromones are also important in communication. Males typically direct signals at rivals, while females direct them at potential mates. Lizards may be able to recognise individuals of
15795-436: The relative absence of trackway evidence for tail dragging suggested that, when walking, the giant, long-tailed theropods would have adopted a more horizontal posture with the tail held parallel to the ground. However, the orientation of the legs in these species while walking remains controversial. Some studies support a traditional vertically oriented femur, at least in the largest long-tailed theropods, while others suggest that
15930-592: The right and left limbs with substantial body bending. This body bending prevents significant respiration during movement, limiting their endurance, in a mechanism called Carrier's constraint . Several species can run bipedally, and a few can prop themselves up on their hindlimbs and tail while stationary. Several small species such as those in the genus Draco can glide: some can attain a distance of 60 metres (200 feet), losing 10 metres (33 feet) in height. Some species, like geckos and chameleons, adhere to vertical surfaces including glass and ceilings. Some species, like
16065-527: The same species by their scent. Acoustic communication is less common in lizards. Hissing , a typical reptilian sound, is mostly produced by larger species as part of a threat display, accompanying gaping jaws. Some groups, particularly geckos, snake-lizards, and some iguanids, can produce more complex sounds and vocal apparatuses have independently evolved in different groups. These sounds are used for courtship, territorial defense and in distress, and include clicks, squeaks, barks and growls. The mating call of
16200-467: The scales. The dentitions of lizards reflect their wide range of diets, including carnivorous, insectivorous, omnivorous, herbivorous, nectivorous, and molluscivorous. Species typically have uniform teeth suited to their diet, but several species have variable teeth, such as cutting teeth in the front of the jaws and crushing teeth in the rear. Most species are pleurodont , though agamids and chameleons are acrodont . The tongue can be extended outside
16335-467: The scope of Marsh's Order Theropoda, it came to replace a previous taxonomic group that Marsh's rival E. D. Cope had created in 1866 for the carnivorous dinosaurs: Goniopoda ("angled feet"). By the early 20th century, some palaeontologists, such as Friedrich von Huene , no longer considered carnivorous dinosaurs to have formed a natural group. Huene abandoned the name "Theropoda", instead using Harry Seeley 's Order Saurischia , which Huene divided into
16470-778: The shape of the tooth or denticles . The morphology of the teeth is distinct enough to tell the major families apart, which indicate different diet strategies. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were actually folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey. The folds helped the teeth stay in place longer, especially as theropods evolved into larger sizes and had more force in their bite. Mesozoic theropods were also very diverse in terms of skin texture and covering. Feathers or feather-like structures (filaments) are attested in most lineages of theropods (see feathered dinosaur ). However, outside
16605-482: The shells. Larger species, such as monitor lizards, can feed on larger prey including fish, frogs, birds, mammals and other reptiles. Prey may be swallowed whole and torn into smaller pieces. Both bird and reptile eggs may also be consumed as well. Gila monsters and beaded lizards climb trees to reach both the eggs and young of birds. Despite being venomous, these species rely on their strong jaws to kill prey. Mammalian prey typically consists of rodents and leporids ;
16740-536: The skin of lizards is covered in overlapping scales made of keratin . This provides protection from the environment and reduces water loss through evaporation. This adaptation enables lizards to thrive in some of the driest deserts on earth. The skin is tough and leathery, and is shed (sloughed) as the animal grows. Unlike snakes which shed the skin in a single piece, lizards slough their skin in several pieces. The scales may be modified into spines for display or protection, and some species have bone osteoderms underneath
16875-415: The slightest sound. As in snakes and many mammals, all lizards have a specialised olfactory system, the vomeronasal organ , used to detect pheromones . Monitor lizards transfer scent from the tip of their tongue to the organ; the tongue is used only for this information-gathering purpose, and is not involved in manipulating food. Some lizards, particularly iguanas, have retained a photosensory organ on
17010-490: The suborders Coelurosauria and Pachypodosauria . Huene placed most of the small theropod groups into Coelurosauria, and the large theropods and prosauropods into Pachypodosauria, which he considered ancestral to the Sauropoda (prosauropods were still thought of as carnivorous at that time, owing to the incorrect association of rauisuchian skulls and teeth with prosauropod bodies, in animals such as Teratosaurus ). Describing
17145-517: 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
17280-413: The theropod dinosaurs were the carnivorous Eodromaeus and, possibly, the herrerasaurids of Argentina . The herrerasaurs existed during the early late Triassic (Late Carnian to Early Norian ). They were found in North America and South America and possibly also India and Southern Africa. The herrerasaurs were characterised by a mosaic of primitive and advanced features. Some paleontologists have in
17415-499: The top of their heads called the parietal eye , a basal ("primitive") feature also present in the tuatara . This "eye" has only a rudimentary retina and lens and cannot form images, but is sensitive to changes in light and dark and can detect movement. This helps them detect predators stalking it from above. Until 2006 it was thought that the Gila monster and the Mexican beaded lizard were
17550-407: The way theropods have often been reconstructed in art and the popular media, the range of motion of theropod forelimbs was severely limited, especially compared with the forelimb dexterity of humans and other primates . Most notably, theropods and other bipedal saurischian dinosaurs (including the bipedal prosauropods ) could not pronate their hands—that is, they could not rotate the forearm so that
17685-602: The wrist not seen in other theropods, thanks to the presence of a specialized half-moon shaped wrist bone (the semi-lunate carpal) that allowed the whole hand to fold backward towards the forearm in the manner of modern birds. In 2001, Ralph E. Molnar published a survey of pathologies in theropod dinosaur bone. He found pathological features in 21 genera from 10 families. Pathologies were found in theropods of all body size although they were less common in fossils of small theropods, although this may be an artifact of preservation. They are very widely represented throughout
17820-623: The young hatch close to 300 days, and the female returns to help them escape the termite mound where the eggs were laid. Around 20 percent of lizard species reproduce via viviparity (live birth). This is particularly common in Anguimorphs. Viviparous species give birth to relatively developed young which look like miniature adults. Embryos are nourished via a placenta -like structure. A minority of lizards have parthenogenesis (reproduction from unfertilised eggs). These species consist of all females who reproduce asexually with no need for males. This
17955-475: 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 ,
18090-406: Was gone by the late Triassic. Digit I is reduced and generally do not touch the ground, and greatly reduced in some lineages. They also lack a digit V on their hands and have developed a furcula which is otherwise known as a wishbone. Early neotheropods like the coelophysoids have a noticeable kink in the upper jaw known as a subnarial gap. Averostrans are some of the most derived theropods and contain
18225-422: Was swimming near the surface of a river and just the tips of its toes and claws could touch the bottom. The tracks indicate a coordinated, left-right, left-right progression, which supports the proposition that theropods were well-coordinated swimmers. During the late Triassic , a number of primitive proto-theropod and theropod dinosaurs existed and evolved alongside each other. The earliest and most primitive of
#350649