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Extinct genus of cartilaginous fishes From Wikipedia, the free encyclopedia
Dracopristis (meaning "dragon shark") is an extinct genus of ctenacanth (a group of shark-like elasmobranchs) that lived around 307 million years ago during the Pennsylvanian subperiod of the Carboniferous period. A single species is known, Dracopristis hoffmanorum, which is named in honor of Ralph and Jeanette Hoffman.
| Dracopristis Temporal range: | |
|---|---|
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| An illustration of D. hoffmanorum | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | †Ctenacanthiformes |
| Family: | †Heslerodidae |
| Genus: | †Dracopristis Hodnett et al. 2021 |
| Species: | †D. hoffmanorum |
| Binomial name | |
| †Dracopristis hoffmanorum Hodnett et al. 2021 | |
D. hoffmanorum possessed large dermal denticles along its head, along with rows of short, multi-cusped teeth in its jaws and very large spines on its dorsal fins, features which inspired the etymology of the genus name. The dorsal spines of the holotype fossil are about 0.57 m (1 ft 10 in) long, and the whole body was around 2 m (6 ft 7 in) long. Its large spines were likely used for defense against larger fishes, while Dracopristis itself was likely a benthic predator which inhabited shallow, brackish-water environments. Before receiving a scientific name, Dracopristis hoffmanorum was informally referred to as the "Godzilla shark".
Fossils of D. hoffmanorum were first discovered in 2013, when a graduate student unearthed the fish's remains from late Pennsylvanian age rocks of Albuquerque, New Mexico.[1] The fossils were discovered within the Tinajas member of the Atrasado Formation, which dates to the late Pennsylvanian.[1] The animal was formally named seven years later in a 2021 paper which described and classified it.[2] The fish's genus name, Dracopristis, is derived from the Latin words draco, meaning 'dragon', and pristis, intended to mean 'shark'. The dorsal spines, facial denticles, and teeth are said by the authors to give the animal a dragon-like appearance, while -pristis is a common suffix used to denote shark-like fishes. The specific name, hoffmanorum, is in honor of Ralph and Jeanette Hoffman who own the Kinney Brick Quarry and helped conduct research on the taxon.[1]
_(Pennsylvanian;_Kansas_or_Nebraska,_USA)_1.jpg)
The holotype specimen, catalogued as NMMNH P-68537, is an articulated skeleton that belonged to an adult female. This specimen is very complete, with about 87–90% of the skeleton being preserved, and represents the most complete ctenacanthiform fossil so far known.[1] A second fossil, NMMNH P-19181, consists of a neurocranium from a juvenile individual, and was originally described as a specimen of Orthacanthus huberi.[1][3]
Prior to its scientific description, the specimen now assigned as the holotype of Dracopristis hoffmanorum was informally referred to as the "Godzilla shark".[2][4]
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Dracopristis is classified within the group Ctenacanthiformes, which were similar to true sharks but differed, amongst other features, in that their mouths were proportionally larger and articulated with the skull in a less flexible manner. Dracopristis was a fairly large ctenacanthiform, reaching sizes of up to 2.06 m (6 ft 9 in) in length.[1] The teeth of D. hoffmanorum, which reach up to 2 cm (0.79 in) in width,[4] were similar to those of other ctenacanthiforms, with cladodont (multi-cusped) teeth which would have allowed the animal to grip on and crush prey.[1] Unlike other ctenacanthiforms, however, the cusps on the teeth of Dracopristis are noticeably shorter and have a more triangular shape.[1] In contrast to true sharks, ctenacanthiforms possessed proportionally large dorsal fin spines,[5] which in Dracopristis were very large even among ctenacanths, at about 57 cm (22 in) long (about 27% of the total body length).[1]
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| Phylogenetic position of D. hoffmanorum as reconstructed by Hodnett and colleagues in 2021.[1] |
Dracopristis was part of a chondrichthyan order known as the Ctenacathiformes,[1] which were likely part of the subclass Elasmobranchii and the infraclass Euselachii, meaning they were more closely related to living sharks and rays than to living chimaeras.[1][6] Despite often being referred to informally as sharks,[1][4][7] ctenacanths were outside of the clade Selachimorpha they were not true sharks.[8] In the taxon's description, conducted in 2021,[1] multiple cladistic studies were performed which found that this fish was most closely related to Ctenacanthus, while Bandringa (long considered another form of ctenacanth)[9][10] was recovered within the Euselachii alongside Tristychius, and Sphenacanthus.[1] They also suggested that ctenacanthiforms and xenacanthids are closer to the crown group euselachians than other chondricthyans such as the Symmoriiformes.[1] In a 2024 publication describing the ctenacanthiform Troglocladodus, Hodnett and coauthors placed Dracopristis in the family Heslerodidae, alongside other genera including Glikmanius, Avonacanthus, and Kaibabvenator.[7]
Later publications have suggested ctenacanths instead represent a much earlier diverging lineage, being on the stem of Chondrichthyes.[11]
During the Pennsylvanian, New Mexico was covered under a vast seaway;[2] Dracopristis would have lived in the shallow coastal waters of this seaway and probably would have been an ambush predator which hunted small fish, crustaceans, and other smaller animals.[12] Its teeth suggest that it was adapted towards grasping and crushing prey.[2] The shape of the fins suggests it lived a mainly nektobenthic (bottom dwelling) lifestyle, and its dorsal fin spines may have served as protection from other predators,[2] indicated by the fact that a fossil of the placoderm Holdenius has been found with the spine of a Devonian ctenacanthiform impaled through its head.[5] D. hoffmanorum is thought to have specialized for brackish-water habitats, and its ecology has been compared with that of the bull shark and common sawfish.[1]
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During the Carboniferous, the Atrasado Formation was a diverse area that consisted of estuarine and lagoonal areas.[12] This is evidenced by some of the fish specimens, which show adaptations to both freshwater and marine environments.[12] There may have been an anoxic zone, which allowed fossils to be preserved without scavengers disturbing them and explains the level of quality many of the Kinney Brick Quarry fossils show.[12] Dracopristis lived alongside a plethora of other organisms, including the larger ctenacanthiform, Glikmanius occidentalis, and may have been a potential prey item to the larger fish.[12] Alongside the ctenacanthiform, the quarry has also preserved the remains of "two hybodontiforms, two holocephalans, three actinopterygians, and a megalichthyoform sarcopterygian",[12] as well as more than 31 distinct fish genera.[12][13] Other fish, such as the large eugeneodont (whorl-tooth shark) Campyloprion might have been occasional marine visitors.[12]
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