34-657: Siphonops is a genus of caecilians in the family Siphonopidae , found in South America . All species are known to occur within Brazil , however, only S. hardyi and S. leucoderus are endemic to it. The native ranges of the other two known species, S. annulatus and S. paulensis , extend outwards into the surrounding countries of Argentina , Bolivia , and Paraguay . S. annulatus' s range extends even further, stretching into Colombia , Ecuador , French Guiana , Guyana , Peru , Suriname , and Venezuela , and giving it perhaps
68-594: A chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves and may contain scales. Modern caecilians are a clade , the order Gymnophiona / ˌ dʒ ɪ m n ə ˈ f aɪ ə n ə / (or Apoda / ˈ æ p ə d ə / ), one of the three living amphibian groups alongside Anura ( frogs ) and Urodela ( salamanders ). Gymnophiona is a crown group , encompassing all modern caecilians and all descendants of their last common ancestor. There are more than 220 living species of caecilian classified in 10 families . Gymnophionomorpha
102-400: A fleshy fin running along the rear section of their bodies, which enhances propulsion in water. Caecilians have small or absent eyes, with only a single known class of photoreceptors , and their vision is limited to dark-light perception. Unlike other modern amphibians (frogs and salamanders) the skull is compact and solid, with few large openings between plate-like cranial bones. The snout
136-419: A phenomenon wherein they provide their hatchlings with a nutrient-rich substance akin to milk, delivered through a maternal vent. Among the species investigated, the oviparous nonmammalian caecilian amphibian Siphonops annulatus stood out, indicating that the practice of lactation may be more widespread among these creatures than previously thought. As detailed in a 2024 study, researchers collected 16 mothers of
170-417: A strong hydrostatic force that lengthens the body. This muscle system allows the animal to anchor its hind end in position, and force the head forwards, and then pull the rest of the body up to reach it in waves. In water or very loose mud, caecilians instead swim in an eel-like fashion. Caecilians in the family Typhlonectidae are aquatic, and the largest of their kind. The representatives of this family have
204-675: Is a clade of medium-sized, temnospondyl amphibians that appeared during the Moscovian in Euramerica , and continued through to the Late Permian and the Early Triassic of Gondwana . They are distinguished by various details of the skull, and many species seem to have been well adapted for life on land. Dissorophoid diversity was highest in the Permian; some of the more diverse families within
238-426: Is a recently coined name for the corresponding total group which includes Gymnophiona as well as a few extinct stem-group caecilians (extinct amphibians whose closest living relatives are caecilians but are not descended from any caecilian). Some palaeontologists have used the name Gymnophiona for the total group and the old name Apoda for the crown group . However, Apoda has other even older uses, including as
272-408: Is much smaller than the right one, an adaptation to body shape that is also found in snakes. Their trunk muscles are adapted to pushing their way through the ground, with the vertebral column and its musculature acting as a piston inside the outer layer of the body wall musculature, which is closely attached to the skin. By contracting the outer layer of muscles it squeezes the coelom and generates
306-401: Is pointed and bullet-shaped, used to force their way through soil or mud. In most species the mouth is recessed under the head, so that the snout overhangs the mouth. The bones in the skull are reduced in number compared to prehistoric amphibian species. Many bones of the skull are fused together: the maxilla and palatine bones have fused into a maxillopalatine in all living caecilians, and
340-456: Is the name of a genus of moth, and its continued use in caecilian taxonomy is potentially confusing and unhelpful. A classification of caecilians by Wilkinson et al. (2011) divided the living caecilians into 9 families containing nearly 200 species. In 2012, a tenth caecilian family was newly described, Chikilidae . This classification is based on a thorough definition of monophyly based on morphological and molecular evidence, and it solves
374-665: The Seychelles Islands in the Indian Ocean , Central America , and in northern and eastern South America . In Africa, caecilians are found from Guinea-Bissau ( Geotrypetes ) to southern Malawi ( Scolecomorphus ), with an unconfirmed record from eastern Zimbabwe . They have not been recorded from the extensive areas of tropical forest in central Africa. In South America, they extend through subtropical eastern Brazil well into temperate northern Argentina . They can be seen as far south as Buenos Aires , when they are carried by
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#1732855280355408-577: The Siphonops annulatus species from cacao plantations in Brazil's Atlantic Forest and filmed them with their altricial hatchlings in the lab. The mothers remained with their offspring, which suckled on a white, viscous liquid from their cloaca , experiencing rapid growth in their first week. This milk-like substance, rich in fats and carbohydrates , is produced in the mother's oviduct epithelium 's hypertrophied glands, similar to mammal milk . The substance
442-412: The nasal and premaxilla bones fuse into a nasopremaxilla in some families. Some families can be differentiated by the presence of absence of certain skull bones, such as the septomaxillae , prefrontals , an/or a postfrontal -like bone surrounding the orbit (eye socket). The braincase is encased in a fully integrated compound bone called the os basale, which takes up most of the rear and lower parts of
476-416: The venom glands of some snakes and lizards . The function of these glands is unknown. The middle ear consists of only the stapes bone and the oval window , which transfer vibrations into the inner ear through a reentrant fluid circuit as seen in some reptiles. Adults of species within the family Scolecomorphidae lack both a stapes and an oval window, making them the only known amphibians missing all
510-461: The wildlife trade . Whether a breeding population has been established in the area is unknown. The name caecilian derives from the Latin word caecus , meaning "blind", referring to the small or sometimes nonexistent eyes. The name dates back to the taxonomic name of the first species described by Carl Linnaeus , which he named Caecilia tentaculata . There has historically been disagreement over
544-572: The Seychelles and India has led to speculation on the presence of undiscovered extinct or extant caecilians there. In 2021, a live specimen of Typhlonectes natans , a caecilian native to Colombia and Venezuela , was collected from a drainage canal in South Florida . It was the only caecilian ever reported in the wild in the United States, and is considered to be an introduction , perhaps from
578-436: The abductors, insert into the rear edge of the pseudoangular below and behind the jaw joint. They close the jaw by pulling backwards and downwards. Jaw muscles are more highly developed in the most efficient burrowers among the caecilians, and appear to help keep the skull and jaw rigid. Their skin is smooth and usually dark, but some species have colourful skins. Inside the skin are calcite scales . Because of these scales,
612-419: The body, giving them a segmented appearance. Like some other living amphibians, the skin contains glands that secrete a toxin to deter predators. The skin secretions of Siphonops paulensis have been shown to have hemolytic properties. Recent research, as documented in the journal Science , has shed light on the behavior of certain species of caecilians. These studies reveal that some caecilians exhibit
646-459: The caecilians were once thought to be related to the fossil Stegocephalia , but they are now believed to be a secondary development, and the two groups are most likely unrelated. Scales are absent in the families Scolecomorphidae and Typhlonectidae , except the species Typhlonectes compressicauda where minute scales have been found in the hinder region of the body. The skin also has numerous ring-shaped folds, or annuli, that partially encircle
680-447: The components of a middle ear apparatus. The lower jaw is specialized in caecilians. Gymnophionans, including extinct species, have only two components of the jaw: the pseudodentary (at the front, bearing teeth) and pseudoangular (at the back, bearing the jaw joint and muscle attachments). These two components are what remains following fusion between a larger set of bones. An additional inset tooth row with up to 20 teeth lies parallel to
714-763: The flood waters of the Paraná River coming from farther north. Their American range extends north to southern Mexico . The northernmost distribution is of the species Ichthyophis sikkimensis of northern India. Ichthyophis is also found in South China and Northern Vietnam . In Southeast Asia, they are found as far east as Java , Borneo , and the southern Philippines , but they have not crossed Wallace's line and are not present in Australia or nearby islands. There are no known caecilians in Madagascar , but their presence in
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#1732855280355748-451: The group include Dissorophidae (toad-like amphibians with armored scutes along their backbone), Trematopidae (terrestrial predators with large triangular skulls), and Branchiosauridae (small neotenic amphibians with large external gills). The small Permo-Carboniferous Micromelerpetontidae are another example of neotenic dissorophoids. Many small dissorophoids with short rounded skulls were historically known as " amphibamids "; in 2018,
782-629: The idea that frogs, salamanders, and caecilians (collectively known as lissamphibians ) are each other's closest relatives. Frogs and salamanders show many similarities to dissorophoids , a group of extinct amphibians in the order Temnospondyli . Caecilians are more controversial; many studies extend dissorophoid ancestry to caecilians. Some studies have instead argued that caecilians descend from extinct lepospondyl or stereospondyl amphibians, contradicting evidence for lissamphibian monophyly (common ancestry). Rare fossils of early gymnophionans such as Eocaecilia and Funcusvermis have helped to test
816-431: The least familiar amphibians. Modern caecilians live in the tropics of South and Central America , Africa , and southern Asia . Caecilians feed on small subterranean creatures such as earthworms . The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and
850-1051: The longstanding problems of paraphyly of the Caeciliidae in previous classifications without an exclusive reliance upon synonymy. There are 219 species of caecilian in 33 genera and 10 families. The most recent phylogeny of caecilians is based on molecular mitogenomic evidence examined by San Mauro et al. (2014), and modified to include some more recently described genera such as Amazops . † Eocaecilia micropodia † Rubricacaecilia monbaroni Amazops Rhinatrema Epicrionops Uraeotyphlus Ichthyophis Crotaphatrema Scolecomorphus Chikila Herpele Boulengerula ? Atretochoana ? Nectocaecilia ? Potamotyphlus Chthonerpeton Typhlonectes Oscaecilia Caecilia ? Idiocranium ? Indotyphlus ? Sylvacaecilia Gegeneophis Hypogeophis Praslinia Grandisonia Geotrypetes Schistometopum Dissorophoidea See text. Dissorophoidea
884-423: The main marginal tooth row of the jaw. All but the most primitive caecilians have two sets of muscles for closing the jaw, compared with the single pair found in other amphibians. One set of muscles, the adductors, insert into the upper edge of the pseudoangular in front of the jaw joint. Adductor muscles are commonplace in vertebrates, and close the jaw by pulling upwards and forwards. A more unique set of muscles,
918-582: The most widespread distribution of any single caecilian species. Siphonops contains the following four species: [REDACTED] [REDACTED] This caecilian article is a stub . You can help Misplaced Pages by expanding it . Caecilian Caecilians ( / s ɪ ˈ s ɪ l i ə n / ; New Latin for 'blind ones') are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians among
952-688: The name Amphibamiformes was erected for a clade equivalent to the broad historical definition of "Amphibamidae". Since 2008, a consensus of early amphibian researchers consider Lissamphibia (modern amphibians) to be part of this clade. There is a large degree of similarity between lissamphibians (for which the oldest known fossils are Early Triassic) and certain Early Permian amphibamiforms , such as Gerobatrachus and Doleserpeton . A few authors still dispute affinities between dissorophoids and lissamphibians. An extensive phylogenetic analysis of dissorophoids conducted in 2016 and 2018 found that
986-578: The name of a genus of Butterfly making its use potentially confusing and best avoided. 'Gymnophiona' derives from the Greek words γυμνος / gymnos ( Ancient Greek for 'naked') and οφις / ophis ( Ancient Greek for 'snake'), as the caecilians were originally thought to be related to snakes and to lack scales. The study of caecilian evolution is complicated by their poor fossil record and specialized anatomy. Genetic evidence and some anatomical details (such as pedicellate teeth ) support
1020-502: The skull. In skulls viewed from above, a mesethmoid bone may be visible in some species, wedging into the midline of the skull roof. All caecilians have a pair of unique sensory structures, known as tentacles , located on either side of the head between the eyes and nostrils. These are probably used for a second olfactory capability , in addition to the normal sense of smell based in the nose. The ringed caecilian ( Siphonops annulatus ) has dental glands that may be homologous to
1054-411: The smaller species resemble worms, while the larger species like Caecilia thompsoni , with lengths up to 1.5 m (5 ft), resemble snakes. Their tails are short or absent, and their cloacae are near the ends of their bodies. Except for one lungless species, Atretochoana eiselti , all caecilians have lungs , but also use their skin or mouths for oxygen absorption. Often, the left lung
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1088-517: The use of the two primary scientific names for caecilians, Apoda and Gymnophiona. Some palaeontologists prefer to use the name Apoda to refer to the "crown group", that is, the group containing all modern caecilians and extinct members of these modern lineages and the name Gymnophiona to refer to the total group, that is, all caecilians and caecilian-like amphibians that are more closely related to modern groups than to frogs or salamanders. However, Apoda been used for groups of fishes and of sea cucumbers and
1122-525: The various conflicting hypotheses for the relationships between caecilians and other living and extinct amphibians. Caecilians' anatomy is highly adapted for a burrowing lifestyle. In a couple of species belonging to the primitive genus Ichthyophis vestigial traces of limbs have been found, and in Typhlonectes compressicauda the presence of limb buds has been observed during embryonic development, remnants in an otherwise completely limbless body. This makes
1156-672: Was released seemingly in response to tactile and acoustic stimulation by the babies. The researchers observed the hatchlings emitting high-pitched clicking sounds as they approached their mothers for milk, a behavior unique among amphibians. This milk-feeding behavior may contribute to the development of the hatchlings' microbiome and immune system, similar to mammalian young. The presence of milk production in caecilians that lay eggs suggests an evolutionary transition between egg-laying and live birth . Caecilians are native to wet, tropical regions of Southeast Asia , India , Bangladesh , Nepal and Sri Lanka , parts of East and West Africa ,
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