Jurassic World Evolution 2 Dunkleosteus
Ayana Munsen
Dunkleosteus could quickly open and close its jaw, creating suction like modern-day suction feeders, and had a bite force that is considered the highest of any living or fossil fish, and among the highest of any animal. Fossils of Dunkleosteus have been found in North America, Poland, Belgium, and Morocco.
Dunkleosteus fossils were first discovered in 1867 by Jay Terrell, a hotel owner and amateur paleontologist who collected fossils in the cliffs along Lake Erie near his home of Sheffield Lake, Ohio (due west of Cleveland), United States. Terrell donated his fossils to John Strong Newberry and the Ohio Geological Survey, who in 1873 described all the material as belonging to a single new genus and species: Dinichthys herzeri. However, with later fossil discoveries, by 1875 it became apparent multiple large fish species were present in the Ohio Shale. Dinichthys herzeri came from the lowermost layer, the Huron Shale, whereas most of the fossils were coming from the younger Cleveland Shale and represented a distinct species.[4] Newberry named this more common species "Dinichthys" terrelli, after Terrell.[5] Most of Terrell's original collection does not survive, having been destroyed by a fire in Elyria, Ohio, in 1873.[4][6] Dunkleosteus fossils can also be found in the Birdsong Shale formation in Tennessee.
The largest collection of Dunkleosteus fossils in the world is housed at the Cleveland Museum of Natural History,[7] with smaller collections (in descending order of size) held at the American Museum of Natural History,[8] Smithsonian National Museum of Natural History,[9] Yale Peabody Museum,[10] the Natural History Museum in London, and the Cincinnati Museum Center. Specimens of Dunkleosteus are on display in many museums throughout the world (see table below), most of which are casts of the same specimen: CMNH 5768, the largest well-preserved individual of D. terrelli.[2][11] The original CMNH 5768 is on display in the Cleveland Museum of Natural History.
Originally thought to be a member of the genus Dinichthys, Dunkleosteus was later recognized as belonging to its own genus in 1956. It was thought to be closely related to Dinichthys, and they were grouped together in the family Dinichthyidae. However, in the phylogenetic analysis of Carr and Hlavin (2010), Dunkleosteus and Dinichthys were found to belong to separate clades of arthrodires: Dunkleosteus belonged to a group called the Dunkleosteoidea while Dinichthys belonged to the distantly related Aspinothoracidi. Carr & Hlavin resurrected the family Dunkleosteidae and placed Dunkleosteus, Eastmanosteus, and a few other genera from Dinichthyidae within it.[13] Dinichthyidae, in turn, is left a monospecific family, though closely related to arthrodires like Gorgonichthys and Heintzichthys.[14]
Alternatively, the subsequent 2016 Zhu et al. study using a larger morphological dataset recovered Panxiosteidae well outside of Dunkleosteoidea, leaving the status of Dunkleosteidae as a clade grouping separate from Dunkleosteoidea in doubt, as shown in the cladogram below:[16]
At least ten different species[13][17] of Dunkleosteus have been described so far. However, many of them are poorly characterized and may be synonyms of previously named species or not pertain to Dunkleosteus.[18] Dunkleosteus as currently defined is a wastebasket taxon for large dunkleosteoid arthrodires that are more evolutionarily derived than Eastmanosteus.[18]
D. belgicus (?) is known from fragments described from the Famennian of Belgium. The median dorsal plate is characteristic of the genus, but, a plate that was described as a suborbital is an anterolateral.[17] Lelivre (1982) considers this taxon a nomen dubium ("doubtful name") and suggests the material may actually pertain to Ardennosteus.[19]
D. denisoni is known from a small median dorsal plate, typical in appearance for Dunkleosteus, but much smaller than normal. It is comparable in skull structure to D. marsaisi.[17]
D. marsaisi refers to the Dunkleosteus fossils from the Lower Famennian Late Devonian strata of the Atlas Mountains in Morocco. It differs in size, the known skulls averaging a length of 35 centimetres (1.15 ft) and in form to D. terrelli. In D. marsaisi, the snout is narrower, and a postpineal fenestra may be present. Many researchers and authorities consider it a synonym of D. terrelli.[20] H. Schultze regards D. marsaisi as a member of Eastmanosteus.[17][21]
D. newberryi is known primarily from a 28 centimetres (11 in) long infragnathal with a prominent anterior cusp, found in the Frasnian portion of the Genesee Group of New York, and originally described as Dinichthys newberryi.[17] Lebedev et al. (2023) noted D. newberryi has an unusually long marginal tooth row compared to other species of Dunkleosteus and lacks the accessory odontoids typical of this genus, suggesting it might not belong to Dunkleosteus or even Dunkleosteoidea.[18]
D. amblyodoratus is known from some fragmentary remains from Late Devonian strata of Kettle Point Formation, Ontario. The species name means 'blunt spear' and refers to the way the nuchal and paranuchal plates in the back of the head form the shape of a blunted spearhead.[13]
D. raveri is a small species, possibly 1 meter long, known from an uncrushed skull roof found in a carbonate concretion from near the bottom of the Huron Shale, of the Famennian Ohio Shale strata. Besides its small size, it had comparatively large eyes. Because D. raveri was found in the strata directly below the strata where the remains of D. terrelli are found, D. raveri may have given rise to D. terrelli. The species name commemorates Clarence Raver of Wakeman, Ohio, who discovered the concretion containing the holotype.[13]
D. tuderensis is known from an infragnathal found in the lower-middle Famennian-aged Bilovo Formation of the Tver Region in northwest Russia. The specific name refers to the Maliy Tuder River as the holotype was found on its bank.[18]
In total, of the ten or so species listed above only four are agreed upon as valid species of Dunkleosteus by all researchers: D. terrelli (which may or may not include Dunkleosteus material from Morocco), D. raveri, D. tuderensis, and possibly D. amblyodoratus (which is known from limited material that appears distinct but is difficult to compare with other dunkleosteids). The taxonomy of early late Devonian (Frasnian) species is poorly established, whereas latest Devonian (Famennian) species are easily referable to this genus. This is not counting additional material assigned to Dunkleosteus sp. from the Famennian of California, Texas, Tennessee, and Poland.[18][23]
Mainly the armored frontal sections of specimens have been fossilized, and consequently, the appearance of the other portions of the fish is mostly unknown.[29] In fact, only about 5% of Dunkleosteus specimens have more than a quarter of their skeleton preserved.[30] Because of this, many reconstructions of the hindquarters are often based on fossils of smaller arthrodires, such as Coccosteus, which have preserved hind sections,[2] leading to widely varying size estimates.[2]
An exceptionally preserved specimen of D. terrelli preserves a pectoral fin outline with ceratotrichia, implying that the fin morphology of placoderms was much more variable than previously thought, and was heavily influenced by locomotory requirements. This knowledge, coupled with the knowledge that fish morphology is more heavily influenced by feeding niche than phylogeny, allowed a 2017 study to infer the caudal fin shape of D. terrelli, reconstructing this fin with a strong ventral lobe, a high aspect ratio, narrow caudal peduncle, in contrast to previous reconstructions based on the anguilliform caudal fin of coccosteomorph placoderms.[11]
In addition, teeth of a chondrichthyan thought to belong to Orodus (Orodus spp.) were found in association with Dunkleosteus remains, suggesting that these were probably stomach contents regurgitated from the animal. Orodus is thought to be tachypelagic, or a fast-swimming pelagic fish. Thus, Dunkleosteus might have been fast enough to catch these fast organisms, and not a slow swimmer like originally thought.[11] Fossils of Dunkleosteus are frequently found with boluses of fish bones, semidigested and partially eaten remains of other fish.[49] As a result, the fossil record indicates it may have routinely regurgitated prey bones rather than digest them. Mature individuals probably inhabited deep sea locations, like other placoderms, living in shallow waters during adolescence.[50]
Dunkleosteus, together with most other placoderms, may have also been among the first vertebrates to internalize egg fertilization, as seen in some modern sharks.[51] Some other placoderms have been found with evidence that they may have been viviparous, including what appears to have been an umbilical cord.[52]
Morphological studies on the lower jaws of juveniles of D. terrelli reveal they were proportionally as robust as those of adults, indicating they already could produce high bite forces and likely were able to shear into resistant prey tissue similar to adults, albeit on a smaller scale. This pattern is in direct contrast to the condition common in tetrapods in which the jaws of juveniles are more gracile than in adults.[53]
The Jurassic Park and Jurassic World movies brought dinosaurs to life on the big screen like never before, but thankfully, InGen never tried to clone these terrifying extinct creatures. By now, it's accepted that times change and evolution has produced an unimaginable menagerie of lifeforms over Earth's 4.5 billion-year history. While the Jurassic Park and Jurassic World series has hosted a slew of extinct animals in its surrounding media, were some of these animals portrayed in the movies, it'd be the stuff of nightmares.
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