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43-1134: Chimaeriformes indet. Alabama Cretolamna C. appendiculata Alabama An otodontid Ischyrhiza I. mira Alabama A sclerorhynchid Scapanorhynchus S. texanus Alabama A mitsukurinid Serratolamna S. serrata? Alabama A lamniform shark Squalicorax S. kaupi Alabama Anacoracids S. pristodontus S . sp. Enchodus E. ferox Alabama Enchodontids E. gladiolus E. petrosus Protosphyraena P . sp. Alabama A pachycormiform Saurodon S . sp. Alabama An ichthyodectiform Stratodus S . sp. Alabama An aulopiform Xiphactinus X. vetus An ichthyodectid Indeterminate hadrosaurid remains have been found in Tennessee . Possible indeterminate tyrannosaurid remains have been found in Alabama . Appalachiosaurus A. montgomeriensis Geographically present in Alabama . Chimaeriformes Chimaeras are cartilaginous fish in

86-428: A chemical arms race. Predator/prey pairs are expected to coevolve over long periods of time. As the predator capitalizes on susceptible individuals, the surviving individuals are limited to those able to evade predation. Resistance typically increases over time as the predator becomes increasingly unable to subdue resistant prey. The cost of developing venom resistance is high for both predator and prey. The payoff for

129-482: A global distribution prior to the end of the Triassic . Unlike modern chimaeras, Mesozoic representatives are often found in shallow water settings. Extinct chimaeriforms include: [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through

172-625: A physical delivery mechanism. Venom has evolved in terrestrial and marine environments and in a wide variety of animals: both predators and prey, and both vertebrates and invertebrates . Venoms kill through the action of at least four major classes of toxin, namely necrotoxins and cytotoxins , which kill cells; neurotoxins , which affect nervous systems; myotoxins , which damage muscles; and haemotoxins , which disrupt blood clotting . Venomous animals cause tens of thousands of human deaths per year. Venoms are often complex mixtures of toxins of differing types. Toxins from venom are used to treat

215-464: A sting. In bees and wasps , the stinger is a modified ovipositor (egg-laying device). In Polistes fuscatus , the female continuously releases a venom that contains a sex pheromone that induces copulatory behavior in males. In wasps such as Polistes exclamans , venom is used as an alarm pheromone, coordinating a response from the nest and attracting nearby wasps to attack the predator. In some species, such as Parischnogaster striatula , venom

258-922: A sustainable level, though Callorhinchus milii (the Australian ghostshark ) experienced severe overfishing in the 20th century before protections were enacted. Neoharriotta pinnata ( sicklefin chimaera ) is targeted along the coast of India for its liver oil, and a recent decline of catch rates may indicate a population crash. Even species without commercial exploitation can fall victim to bycatch: Callorhinchus callorynchus ( American elephantfish ), Neoharriotta carri ( dwarf sicklefin chimaera ), Chimaera monstrosa ( rabbit fish ), Chimaera ogilbyi ( Ogilby's ghostshark ), Hydrolagus colliei ( spotted ratfish ), and Hydrolagus melanophasma ( eastern Pacific black ghostshark ) all have bycatch rates exceeding 10% in certain parts of their range, and some are experiencing steep declines. Chimaeras have mostly avoided harvesting for

301-424: A unique hypermineralized tissue called pleromin . Pleromin is an extremely hard enamel -like tissue, arranged into sheets or beaded rods, but it is deposited by mesenchyme -derived cells similar to those that form bone . In addition, pleuromin's hardness is due to the mineral whitlockite , which crystalizes within the teeth as the animal matures. Other vertebrates with hypermineralized teeth rely on enamel, which

344-470: A wide range of diseases, explored in over 5,000 scientific papers. In medicine, snake venom proteins are used to treat conditions including thrombosis , arthritis , and some cancers . Gila monster venom contains exenatide , used to treat type 2 diabetes . Solenopsins extracted from fire ant venom has demonstrated biomedical applications, ranging from cancer treatment to psoriasis . A branch of science, venomics , has been established to study

387-422: A wide range of medical conditions including thrombosis , arthritis , and some cancers . Studies in venomics are investigating the potential use of venom toxins for many other conditions. The use of venom across a wide variety of taxa is an example of convergent evolution . It is difficult to conclude exactly how this trait came to be so intensely widespread and diversified. The multigene families that encode

430-441: A wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved venom apparatus , such as fangs or a stinger , in a process called envenomation . Venom is often distinguished from poison , which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen , which is actively transferred to the external surface of another animal via

473-701: Is Protochimaera from the Early Carboniferous (338–332 million years ago) of Russia, which is more closely related to modern chimeras (Chimaeroidei) than any other known extinct groups of Chimaeriformes. The earliest known remains attributable to modern chimaeras are known from the Early Jurassic ( Pliensbachian ) of Europe, but egg cases from the Late Triassic of Yakutia, Russia and New Zealand that resemble those of rhinochimaerids and callorhinchids respectively indicates that they had

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516-621: Is holostylic , meaning that the palatoquadrate (upper jaw cartilage) is completely fused to the neurocranium (cranial cartilage). This contrasts with modern sharks, where the palatoquadrate is movable and detachable, a trait known as hyostyly . The back of the head is supported by a complex of fused vertebrae called the synarcual, which also connects to the dorsal fin spine. Instead of sharks' many sharp, consistently-replaced teeth, chimaeras have just six large, permanent tooth-plates, which grow continuously throughout their entire life. These tooth-plates are arranged in three pairs, with one pair at

559-669: Is a monogenean parasite of the gills of Chimaera monstrosa ; the species can attain 50 mm (2.0 in) in length. Despite their secluded habits, some chimaera species may be threatened by overfishing through bycatch or commercial exploitation. No species are listed as Endangered according to the IUCN , but four are listed as Vulnerable , four more as Near Threatened , and many more as Data Deficient (too rare to evaluate). Many species have restricted ranges and practically none have had their movement patterns studied. In addition, bycatch reports are usually insufficiently precise to

602-539: Is applied all over the body as an antimicrobial protection. Many caterpillars have defensive venom glands associated with specialized bristles on the body called urticating hairs . These are usually merely irritating, but those of the Lonomia moth can be fatal to humans. Bees synthesize and employ an acidic venom ( apitoxin ) to defend their hives and food stores, whereas wasps use a chemically different venom to paralyse prey, so their prey remains alive to provision

645-406: Is derived from ameloblasts and encases round crystals of the mineral apatite . Chimaeras also differ from sharks in that they have separate anal and urogenital openings. Chimaeras live in temperate ocean floors, with some species inhabiting depths exceeding 2,000 m (6,600 ft), with relatively few modern species regularly inhabiting shallow water. Exceptions include the members of

688-534: Is found in a few other reptiles such as the Mexican beaded lizard , the gila monster , and some monitor lizards, including the Komodo dragon . Mass spectrometry showed that the mixture of proteins present in their venom is as complex as the mixture of proteins found in snake venom. Some lizards possess a venom gland; they form a hypothetical clade, Toxicofera , containing the suborders Serpentes and Iguania and

731-459: Is higher. Rattlesnakes have responded locally by increasing the effectiveness of their venom. The kingsnakes of the Americas are constrictors that prey on many venomous snakes. They have evolved resistance which does not vary with age or exposure. They are immune to the venom of snakes in their immediate environment, like copperheads, cottonmouths, and North American rattlesnakes, but not to

774-460: Is proven that reptile and platypus venom have independently evolved, it is thought that there are certain protein structures that are favored to evolve into toxic molecules. This provides more evidence of why venom has become a homoplastic trait and why very different animals have convergently evolved. Envenomation resulted in 57,000 human deaths in 2013, down from 76,000 deaths in 1990. Venoms, found in over 173,000 species, have potential to treat

817-1006: The Cnidaria , sea urchins among the Echinodermata , and cone snails and cephalopods , including octopuses , among the Molluscs . Venom is found in some 200 cartilaginous fishes, including stingrays , sharks , and chimaeras ; the catfishes (about 1000 venomous species); and 11 clades of spiny-rayed fishes ( Acanthomorpha ), containing the scorpionfishes (over 300 species), stonefishes (over 80 species), gurnard perches , blennies , rabbitfishes , surgeonfishes , some velvetfishes , some toadfishes , coral crouchers , red velvetfishes , scats , rockfishes , deepwater scorpionfishes , waspfishes , weevers , and stargazers . Some salamanders can extrude sharp venom-tipped ribs. Two frog species in Brazil have tiny spines around

860-469: The fin trade , which threatens many true sharks. Another threat is habitat destruction of coastal nurseries (by urban development) or deepwater reefs (by deep sea mining and trawling ). Near-shore species such as Callorhinchus milii are vulnerable to the effects of climate change : stronger storms and warmer seawater are predicted to increase egg mortality by disrupting the stable environments necessary to complete incubation. In some classifications,

903-617: The genus Callorhinchus , the rabbit fish and the spotted ratfish , which locally or periodically can be found at shallower depths. Consequently, these are also among the few species kept in public aquaria . They live in all the oceans except for the Arctic and Antarctic oceans. The usual diet of chimaeras consist of crustaceans , and more specifically, they include ophiurans and molluscs. Modern species are demersal durophages , but they used to be more diverse. The Carboniferous period had forms that lived as specialised suction feeders in

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946-636: The order Chimaeriformes ( / k ɪ ˈ m ɛ r ɪ f ɔːr m iː z / ), known informally as ghost sharks , rat fish , spookfish , or rabbit fish ; the last three names are not to be confused with rattails , Opisthoproctidae , or Siganidae , respectively. At one time a "diverse and abundant" group (based on the fossil record ), their closest living relatives are sharks and rays , though their last common ancestor with them lived nearly 400 million years ago. Living species are largely confined to deep water. Chimaeras are soft-bodied, shark-like fish with bulky heads and long, tapered tails; measured from

989-474: The pectoral fins . The pectoral fins are large enough to generate lift at a relaxed forward momentum, giving the chimaera the appearance of "flying" through the water. Further back on the body are also a pair of smaller pelvic fins , and some genera bear an anal fin in front of the tail. In chimaerids and rhinochimaerids , the tail is leptocercal , meaning that it is thin and whip-like, edged from above and below by fins of similar size. In callorhinchids ,

1032-439: The phosphodiester bonds of DNA ; and neurotoxins, which disrupt signalling in the nervous system. Snake venom causes symptoms including pain, swelling, tissue necrosis, low blood pressure, convulsions, haemorrhage (varying by species of snake), respiratory paralysis, kidney failure, coma, and death. Snake venom may have originated with duplication of genes that had been expressed in the salivary glands of ancestors. Venom

1075-413: The chimaeras are included (as subclass Holocephali ) in the class Chondrichthyes of cartilaginous fishes; in other systems, this distinction may be raised to the level of class. Chimaeras also have some characteristics of bony fishes . A renewed effort to explore deep water and to undertake taxonomic analysis of specimens in museum collections led to a boom during the first decade of the 21st century in

1118-473: The cost of physiological resistance is an increased chance of survival for prey, but it allows predators to expand into underutilised trophic niches. The California ground squirrel has varying degrees of resistance to the venom of the Northern Pacific rattlesnake . The resistance involves toxin scavenging and depends on the population. Where rattlesnake populations are denser, squirrel resistance

1161-406: The crown of their skulls which, on impact, deliver venom into their targets. Some 450 species of snake are venomous. Snake venom is produced by glands below the eye (the mandibular glands ) and delivered to the target through tubular or channeled fangs. Snake venoms contain a variety of peptide toxins, including proteases , which hydrolyze protein peptide bonds; nucleases , which hydrolyze

1204-472: The evolution of these species has been problematic given the paucity of good fossils. DNA sequencing has become the preferred approach to understanding speciation. The group containing chimaeras and their close relatives ( Holocephali ) is thought to have diverged from Elasmobranchii (the group containing modern sharks and rays) during the Devonian , over 380 million years ago. The oldest known chimaeriform

1247-538: The families Varanidae , Anguidae , and Helodermatidae . Euchambersia , an extinct genus of therocephalians , is hypothesized to have had venom glands attached to its canine teeth. A few species of living mammals are venomous, including solenodons , shrews , the European mole , vampire bats , male platypuses , and slow lorises . Shrews have venomous saliva and most likely evolved their trait similarly to snakes. The presence of tarsal spurs akin to those of

1290-464: The females' pectoral fins during mating. The prepelvic tentacula are serrated hooked plates normally hidden in pouches in front of the pelvic fins, and they anchor the male to the female. Lastly, the pelvic claspers (sexual organs shared by sharks) are fused together by a cartilaginous sheathe before splitting into a pair of flattened lobes at their tip. As other fish, chimaeras have a number of parasites . Chimaericola leptogaster ( Chimaericolidae )

1333-521: The food chambers of their young. The use of venom is much more widespread than just these examples; many other insects, such as true bugs and many ants , also produce venom. The ant species Polyrhachis dives uses venom topically for the sterilisation of pathogens. There are venomous invertebrates in several phyla , including jellyfish such as the dangerous box jellyfish , the Portuguese man-of-war (a siphonophore) and sea anemones among

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1376-637: The many toxins that they contain; some venoms are complex mixtures of toxins of differing types. Major classes of toxin in venoms include: Venom is widely distributed taxonomically, being found in both invertebrates and vertebrates, in aquatic and terrestrial animals, and among both predators and prey. The major groups of venomous animals are described below. Venomous arthropods include spiders , which use fangs on their chelicerae to inject venom , and centipedes , which use forcipules   —   modified legs   —   to deliver venom, while scorpions and stinging insects inject venom with

1419-478: The number of new species identified. A preliminary study found 8% of species to be threatened. There are over 50 extant species in six genera and three families, with other genera known from fossils. The extant species fall into three families—the Callorhinchidae, Rhinochimaeridae and Chimaeridae with the callorhinchids being the most basal clade . Suborder Chimaeroidei Patterson 1965 Tracing

1462-443: The platypus in many non- therian Mammaliaformes groups suggests that venom was an ancestral characteristic among mammals. Extensive research on platypuses shows that their toxin was initially formed from gene duplication, but data provides evidence that the further evolution of platypus venom does not rely as much on gene duplication as was once thought. Modified sweat glands are what evolved into platypus venom glands. Although it

1505-414: The proteins associated with venom and how individual components of venom can be used for pharmaceutical means. Venom is used as a trophic weapon by many predator species. The coevolution between predators and prey is the driving force of venom resistance, which has evolved multiple times throughout the animal kingdom. The coevolution between venomous predators and venom-resistant prey has been described as

1548-471: The species or even genus level, so it is difficult to keep track of bycatch on a species-by-species basis. This lack of data renders chimaera species especially susceptible to overlooked population declines. Several near-shore species are purposefully caught for their meat, especially callorhinchids, Hydrolagus bemisi ( pale ghost shark ), and Hydrolagus novaezealandi ae ( dark ghost shark ). Modern quotas have helped to moderate collection of these species to

1591-465: The tail is instead heterocercal , with a larger upper lobe inclined upwards, similar to many sharks. There are two dorsal fins: a large triangular first dorsal fin and a low rectangular or depressed second dorsal fin. For defense, some chimaeras have a venomous spine on the front edge of the dorsal fin . In many species, the bulbous snout is modified into an elongated sensory organ, capable of electroreception to find prey. The cartilaginous skull

1634-410: The tail, they can grow up to 150 cm (4.9 ft) in length. Like other members of the class Chondrichthyes , chimaera skeletons are entirely cartilaginous, or composed of cartilage . Males use forehead denticles to grasp a female by a fin during copulation. The gill arches are condensed into a pouch-like bundle covered by a sheet of skin (an operculum ), with a single gill -opening in front of

1677-527: The tentacles of venomous sea anemones (an obligatory symbiosis for the fish), and are resistant to their venom. Only 10 known species of anemones are hosts to clownfish and only certain pairs of anemones and clownfish are compatible. All sea anemones produce venoms delivered through discharging nematocysts and mucous secretions. The toxins are composed of peptides and proteins. They are used to acquire prey and to deter predators by causing pain, loss of muscular coordination, and tissue damage. Clownfish have

1720-420: The tip of the lower jaws and two pairs along the upper jaws. They together form a protruding, beak-like crushing and grinding mechanism, comparable to the incisor teeth of rodents and lagomorphs (hence the name "rabbit fish"). Chimaera teeth are unique among vertebrates, due to their mode of mineralization. Most of each plate is formed by relatively soft osteodentin , but the active edges are supplemented by

1763-403: The toxins of venomous animals are actively selected , creating more diverse toxins with specific functions. Venoms adapt to their environment and victims, evolving to become maximally efficient on a predator 's particular prey (particularly the precise ion channels within the prey). Consequently, venoms become specialized to an animal's standard diet. Venoms cause their biological effects via

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1806-433: The venom of, for example, king cobras or black mambas. Among marine animals, eels are resistant to sea snake venoms, which contain complex mixtures of neurotoxins, myotoxins, and nephrotoxins, varying according to species. Eels are especially resistant to the venom of sea snakes that specialise in feeding on them, implying coevolution; non-prey fishes have little resistance to sea snake venom. Clownfish always live among

1849-413: The water column. Chimaera reproduction resembles that of sharks in some ways: males employ claspers for internal fertilization of females and females lay eggs within spindle -shaped, leathery egg cases . Unlike sharks, male chimaeras have retractable sexual appendages (known as tentacula) to assist mating. The frontal tentaculum, a bulbous rod which extends out of the forehead, is used to clutch

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