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47-581: In 2019, a worm-shaped amphibian caecilian , Typhlonectes natans , was found living in the canal. Normally found in Venezuela and Colombia, its capture was the first record of a caecilian in the United States. 25°47′43″N 80°14′40″W  /  25.7952°N 80.2445°W  / 25.7952; -80.2445 This Miami-Dade County, Florida location article is a stub . You can help Misplaced Pages by expanding it . This article about

94-594: 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

141-613: A monophyletic group, it has been considered an evolutionary grade of basal ("primitive") lepospondyls, although there is growing consensus that a large subset of fossorially-adapted microsaurs, the Recumbirostra , is monophyletic. Lysorophia may belong within the Recumbirostran clade, distinct from other derived lepospondyls. Nectridea may also be paraphyletic, consisting of a range of more anatomically-specialized lepospondyls. The name Holospondyli has been proposed for

188-501: A 1995 paper by Robert Carroll argued that lepospondyls were actually a monophyletic group closer to reptiles. Carroll considered them closer to reptiles than the seymouriamorphs , but not as close as the diadectomorphs . Many phylogenetic analyses since Carroll (1995) agreed with his interpretation, including Laurin & Reisz (1997), Anderson (2001), and Ruta et al. (2003). A few have still considered lepospondyls ancestral to amphibians, but came to this conclusion without changing

235-1391: A clade including aïstopods, and nectrideans, and possibly adelospondyls, although not all recent phylogenetic analyses support the grouping. The following cladogram , simplified, is after an analysis of tetrapods and stem-tetrapods presented by Ruta et al. in 2003: Batropetes fritschi Tuditanus punctulatus Pantylus cordatus Stegotretus agyrus Asaphestera intermedia Saxonerpeton geinitzi Hapsidopareion lepton Micraroter erythrogeios Pelodosotis elongatum Rhynchonkos stovalli Cardiocephalus sternbergi Euryodus primus Microbrachis pelikani Hyloplesion longicostatum Odonterpeton triangulare Brachydectes spp. Acherontiscus caledoniae Adelospondylus watsoni Adelogyrinus simorhynchus Dolichopareias disjectus Scincosaurus crassus Keraterpeton galvani Batrachiderpeton reticulatum Diceratosaurus brevirostris Diplocaulus magnicornis Diploceraspis burkei Ptyonius marshii Sauropleura spp. Urocordylus wandesfordii Lethiscus stocki Oestocephalus amphiuminum Phlegethontia linearis The "lepospondyl hypothesis" of modern amphibian origins proposes that lissamphibians are monophyletic (that is, they form their own clade) and that they evolved from lepospondyl ancestors. Two alternatives are

282-447: A diverse range of body forms and include species with newt-like, eel- or snake-like, and lizard -like forms. Various species were aquatic, semiaquatic, or terrestrial. None were large (the biggest genus, the diplocaulid Diplocaulus , reached a meter in length, but most were much smaller), and they are assumed to have lived in specialized ecological niches not taken by the more numerous temnospondyl amphibians that coexisted with them in

329-400: 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

376-401: A group with elongated bodies and very small limbs; Aïstopoda , a group of limbless, extremely elongated snake-like forms; Adelospondyli , a group of presumably aquatic forms that resemble aïstopods, but have more solidly built skulls; and Nectridea , another diverse group that includes terrestrial and aquatic newt-like forms. Microsauria is generally considered paraphyletic ; rather than being

423-509: A location in Collier County , Florida 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

470-419: 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

517-417: 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

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564-451: A suite of anatomical features shared between lissamphibians and a group of Paleozoic temnospondyls called dissorophoids . Under this hypothesis, Lepospondyli either falls outside crown group Tetrapoda (the smallest clade containing all living tetrapods, i.e. the smallest clade containing Lissamphibia and Amniota), or is closer to amniotes and therefore part of Reptiliomorpha . However, some phylogenetic analyses continue to find support for

611-716: Is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ( Diplocaulus minimus ), lepospondyls lived from the Visean stage of the Early Carboniferous to the Early Permian and were geographically restricted to what is now Europe and North America . Five major groups of lepospondyls are known: Adelospondyli ; Aïstopoda ; Lysorophia ; Microsauria ; and Nectridea . Lepospondyls have

658-426: 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

705-448: Is an artificial ( polyphyletic ) grouping with some members closely related to extinct stem tetrapod groups and others more closely related to modern amphibians or reptiles. Early phylogenetic analyses conducted in the 1980s and 1990s often maintained the idea that lepospondyls were paraphyletic, with nectrideans close to colosteids and microsaurs close to temnospondyls, which were considered to be ancestral to modern amphibians. However,

752-408: 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

799-401: 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

846-456: 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

893-679: 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

940-586: 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

987-412: 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

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1034-416: 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

1081-465: 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

1128-543: The "temnospondyl hypothesis", in which lissamphibians originated within Temnospondyli, and the "polyphyly hypothesis", in which caecilians originated from lepospondyls while frogs and salamanders (collectively grouped within Batrachia ) evolved from temnospondyls. Of the three hypotheses, the temnospondyl hypothesis is currently the most widely accepted among researchers. Strong support for this relationship comes from

1175-520: The Paleozoic. Lepospondyli was named in 1888 by Karl Alfred von Zittel , who coined the name to include some tetrapods from the Paleozoic that shared some specific characteristics in the notochord and teeth . Lepospondyls have sometimes been considered to be either related or ancestral to modern amphibians or to Amniota (the clade containing reptiles and mammals). It has been suggested that

1222-529: 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

1269-436: 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,

1316-419: 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

1363-459: 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

1410-607: The clade Lissamphibia . For a long time, the Lepospondyli were considered one of the three subclasses of Amphibia , along with the Lissamphibia and the Labyrinthodontia . However, the dissolution of "labyrinthodonts" into separate groups such as temnospondyls and anthracosaurs has cast doubt on these traditional amphibian subclasses. Much like "Labyrinthodontia", some studies proposed that Lepospondyli

1457-447: 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

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1504-786: 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

1551-428: The grouping is polyphyletic , with aïstopods being primitive stem-tetrapods, while recumbirostran microsaurs are primitive reptiles. All lepospondyls are characterised by having simple, spool-shaped vertebrae that did not ossify from cartilage , but rather grew as bony cylinders around the notochord. In addition, the upper portion of the vertebra, the neural arch, is usually fused to the centrum (the main body of

1598-629: 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

1645-479: The internal and external relationships of the remaining lepospondyl taxa. The former places the remaining lepospondyls into a single clade along the amniote stem. The latter does not treat the relationships of nectrideans or adelospondyls, but finds microsaurs to be early amniotes, and places lysorophians within microsaurs. Five main groups of lepospondyls are often recognized: Microsauria , a superficially lizard- or salamander-like and species-rich group; Lysorophia ,

1692-431: 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

1739-581: The lepospondyl hypothesis. The analysis by Vallin and Laurin (2004) found lissamphibians to be most closely related to lysorophians, followed by microsaurs. Pawley (2006) also found lysorophians to be the closest relatives of lissamphibians, but found aïstopods and adelogyrinids rather than microsaurs to be the second most closely related groups. Marjanović (2010) found holospondyls to be the most closely related group to lissamphibians, followed by lysorophians. Under this hypothesis, lepospondyls would be crown tetrapods and temnospondyls would be stem tetrapods. Below

1786-1190: 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 Lepospondyli Lissamphibia ? † Westlothiana ? † Adelospondyli ? † Aïstopoda ? † Lysorophia † " Microsauria " † " Nectridea " Lepospondyli

1833-423: 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,

1880-582: 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

1927-444: The position of lepospondyls compared to seymouriamorphs and diadectomorphs. Lepospondyl and tetrapod classification is still controversial, and even recent studies have had doubts about lepospondyl monophyly. For example, a 2007 paper has suggested that adelospondyls are stem-tetrapods close to colosteids and a 2017 paper on Lethiscus has Aïstopoda in the tetrapod stem based on their primitive braincase. These studies differ in

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1974-502: 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

2021-411: 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

2068-517: 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

2115-531: 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

2162-514: The vertebra). The position of the Lepospondyli within the Tetrapoda is uncertain because the earliest lepospondyls were already highly specialized when they first appeared in the fossil record. Some lepospondyls were once thought to be related or perhaps ancestral to modern salamanders (Urodela), but not the other modern amphibians. This view is no longer held and all modern amphibians (frogs, salamanders, and caecilians ) are now grouped within

2209-672: 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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