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84-676: Dakotaraptor (meaning “thief from Dakota ”) is a chimaeric genus of maniraptoriform theropod dinosaur that lived in western North America during the Late Cretaceous period. The remains have been found in the Maastrichtian -aged Hell Creek Formation , dated to the very end of the Mesozoic era , making Dakotaraptor potentially one of the last surviving dromaeosaurids , though other researchers have disputed its classification. The remains of D. steini were discovered in

168-410: A "lower" down branch had them too, then a species in the middle position likely did as well. Dakotaraptor ’s quill knobs show that the animal unequivocally had prominent wing feathers, making it the largest dromaeosaurid with confirmed plumage of that type. The quill knobs of Dakotaraptor have a diameter of about 8–10 millimetres (0.31–0.39 in), which shows that these feathers were rather large. It

252-419: A body-case of broadened and somewhat overlapping ribs, suggesting an early stage in the acquisition of a shell. The fossil has been called "a diapsid reptile in the process of becoming secondarily anapsid". Olivier Rieppel summarizes the phylogenetic origins of the ancestral turtles: " Eunotosaurus is placed at the bottom of the stem section of the turtle tree, followed by Pappochelys and Odontochelys along

336-433: A complete bony plastron and an incomplete carapace. The fossil showed that the plastron evolved before the carapace. Like crown turtles, it lacked intercostal muscles, so rib mobility was limited. The ribs were laterally expanded and broadened without ossification, like the embryos of modern turtles. The development of a shell reaches completion with the late Triassic Proganochelys of Germany and Thailand. It lacked

420-461: A diameter of 16 centimetres (6.3 in) and a length of 24 centimetres (9.4 in) measured along the outer curve. This equals 29% of the length of the thighbone (as previously mentioned), compared to 23% in Deinonychus . The claw is transversely flattened and has a droplet-shaped cross-section. The flexor tubercle, a large bump near the base, served as an attachment site for flexor muscles -

504-467: A dromaeosaurid, with an estimated adult length of 5.5 m (18 ft). In 2016, other estimations suggested a length of 4.35-6 m (14.3-19.7 ft) and a weight of 220-350 kg (485-772 lbs). This approaches the size of one of the largest known dromaeosaurids, Utahraptor . Dakotaraptor , however, does not have the proportions and adaptations of Utahraptor , but more closely resembles smaller dromaeosaurids, like Deinonychus . Apart from its large size,

588-477: A fluvial bonebed bearing the remains of a variety of dinosaurian and non-dinosaurian remains, which yielded a partial skeleton attributed by DePalma to a large dromaeosaurid. Subsequently, the same site produced additional dromaeosaurid remains. In 2015, the type species Dakotaraptor steini was named and described by Robert A. DePalma, David A. Burnham, Larry Dean Martin , Peter Lars Larson , and Robert Thomas Bakker . The generic name , Dakotaraptor , combines

672-399: A fully formed plastron. In place of a modern plastron, Pappochelys has paired gastralia, like those found in E. africanus . Pappochelys is different from its ancestor because the gastralia show signs of having once been fused, as indicated by the fossil specimens which show forked ends. This evidence shows a gradual change from paired gastralia, to paired and fused gastralia, and finally to

756-490: A furcula, but now also excluded from the known remains of Dakotaraptor ). Additionally, four isolated teeth were referred (PBMNH.P.10.119.T, PBMNH.P.10.121.T, PBMNH.P.10.122.T, and PBMNH.P.10.124.T). These fossils are part of the collection of The Palm Beach Museum of Natural History. Other referred fossils are KUVP 156045 (an isolated tooth) and NCSM 13170 (a third supposed furcula that was later identified as not belonging to Dakotaraptor ). The elements originally identified as

840-483: A horny cover in their early terrestrial ancestral forms. The carapacial ridge plays an essential role in the development of the turtle shell. Embryological analyses show that the carapacial ridge initiates the formation of the turtle shell. It causes axial arrest which causes the ribs to be dorsalized, the shoulder girdle to be rearranged and encapsulated in the rib cage, and the carapace to develop. Odontochelys semitestacea presents evidence of axial arrest that

924-401: A member of Trionychidae . In 2016, DePalma et al. recognized that none of the referred furculae actually belonged to Dakotaraptor and excluded them from its hypodigm. In 2024, even the dinosaurian elements of Dakotaraptor were questioned, with supposed traits diagnostic for dromaeosaurs also referrable to caenagnathids and ornithomimosaurians . Dakotaraptor is exceptionally large for

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1008-413: A more minimized use of that claw. As these are the bony cores of the claws, they would have been covered in a keratinous sheath that extended the "nail" and ended in a sharp tip. The third claw is keeled too, but is much smaller, with a tip to joint length of 7 centimetres (2.8 in) and a curve length of 9 centimetres (3.5 in). The groove on its outer side towards the tip ends in a bone tunnel, which

1092-659: A multi-species bonebed. Elements of the holotype and referred specimens were later found to belong to trionychid turtles , and it is unclear whether further analysis of potential non-dromaeosaurid affinities of the holotype and referred material can be properly conducted, because currently the type specimen is housed in private collection. Phylogenetic analyses of D. steini place it in a variety of positions within Dromaeosauridae. In 2005, paleontologist Robert DePalma in Harding County , South Dakota discovered

1176-511: A reference to South Dakota and the Dakota people with the Latin word raptor , meaning "plunderer". The specific name , steini , honors paleontologist Walter W. Stein. Dakotaraptor was one of eighteen dinosaur taxa from 2015 to be described in open access or free-to-read journals. The holotype , PBMNH.P.10.113.T, was found in a sandstone layer of the upper Hell Creek Formation , dating to

1260-427: A series of neural bones, which although always present are not always visible, in many species of Pleurodire they are submerged below the pleurals. Beneath the neural bone is the neural arch which forms the upper half of the encasement for the spinal cord. Below this the rest of the vertebral column. Some species of turtles have some extra bones called mesoplastra, which are located between the carapace and plastron in

1344-481: Is 22% longer than the thighbone, indicating high running capability. The shinbone's cnemial crest has a sharp corner pointing to the front. Its fibular crest ends in a hook-shaped process pointing up, a condition that is unique in the entirety of Theropoda . The astragalus and calcaneum, the upper ankle bones, are fused and similar to those in Bambiraptor . The top of the calcaneum has but a small contact facet for

1428-523: Is a rare condition. Dakotaraptor was placed in Dromaeosauridae . A cladistic analysis showed that it was the sister taxa of Dromaeosaurus . They again formed a clade with Utahraptor , of which clade Achillobator was the direct side branch. Despite being related to other large dromaeosaurids, Dakotaraptor was suggested to represent a separate fourth instance of dromaeosaurid size increase, besides Deinonychus , Unenlagia , and

1512-488: Is another theropod from the Hell Creek Formation, named in 2013 for a lower jaw, a maxilla, and some teeth. Acheroraptor was diagnosed by multiple features, including the possession of ridges on its teeth. Teeth are the only overlapping features between Acheroraptor and Dakotaraptor . However Acheroraptor is significantly smaller and differs from Dakotaraptor only in that it possesses vertical ridges on

1596-430: Is normally referred to as tortoiseshell . The turtle shell is made up of numerous bony elements, generally named after similar bones in other vertebrates, and a series of keratinous scutes which are also uniquely named. The ventral surface is called the plastron . These are joined by an area called the bridge. The actual suture between the bridge and the plastron is called the anterior bridge strut. In Pleurodires

1680-401: Is observed in embryos but lacks fan-shaped ribs and a carapace. This suggests that the primitive carapacial ridge functioned differently and must have gained the function of mediating the ribs and carapace development later. The PAX1 and Sonic hedgehog gene ( Shh ) serve as key regulators during the development of the vertebral column. Shh expression in the neural tube is essential for

1764-483: Is the Pleurodiran turtles have an intergular scute between the gulars at the front, giving them a total of 13 plastral scutes. Compared to the 12 in all Cryptodiran turtles. The carapace is the dorsal (back), convex part of the shell structure of a turtle , consisting of the animal's ossified ribs fused with the dermal bone. The spine and expanded ribs are fused through ossification to dermal plates beneath

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1848-424: Is used as an anatomical descriptive term not related to its functionality, since Dakotaraptor was flightless. This is similar to the term “wing” for the same appendages in ostriches, emus, and other flightless birds. It is meant to express that the arm is equipped with long feathers resembling those of flight feathers in birds that can actually fly. Many of the wing bones were discovered (humerus, radius, ulna, two of

1932-412: Is used to compare the sizes of the individual plastral scutes (measured along the midseam). The following plastral scutes are often distinguished (with their abbreviation): Comparison of the plastral formulas provides distinction between the two species. For example, for the eastern box turtle , the plastral formula is: an > abd > gul > pect > hum >< fem. Turtle plastrons were used by

2016-675: The Achillobator plus Utahraptor clade. Saurornitholestes Velociraptor Deinonychus Atrociraptor Achillobator Utahraptor Dakotaraptor Dromaeosaurus A recent study conducted by Hartman et al. 2019 recovered a placement of Dakotaraptor in Unenlagiidae . If this study proves correct, then Dakotaraptor would have been one of the northernmost genera of Unenlagiine known. Austroraptor Buitreraptor Pyroraptor Pamparaptor Rahonavis Dakotaraptor Unenlagia In

2100-732: The Bozeman Trail , until the Treaty of Fort Laramie in 1868. The treaty established the Great Sioux Reservation and "designated the Black Hills as 'unceded Indian Territory' for the exclusive use of native peoples." The subsequent discovery of gold in the Black Hills in 1874 by George Armstrong Custer 's Black Hills Expedition , would cause a gold rush and the U.S. to violate the treaty. The Indian Appropriations Act of 1876 went into effect on August 15, 1876. This

2184-785: The Midwestern United States , with the western portion in the High Plains . The PBS miniseries New Perspectives on the West noted historically important areas within the Dakotas, including the Black Hills , the town of Deadwood , Fort Buford , Standing Rock Reservation and Wounded Knee . The Upper Missouri River and the Upper Missouri River Valley are important geological features in

2268-420: The dermis of the back to support the carapace. The development is signalled locally by fibroblast growth factors including FGF10 . Zoologists have sought to explain the evolutionary origin of the turtles, and in particular of their unique carapace. In 1914, J. Versluys proposed that bony plates in the dermis, osteoderms , fused first to each other and then to the ribs beneath them. The theory persisted into

2352-409: The remiges , or wing feathers. When quill knobs are present, this is considered a strong indication that the animal had long remiges on the wings. Since quill knobs are rare in the fossil record, paleontologists mainly relied on phylogenetic bracketing to determine if a species was likely to have had wing feathers - if a relative on a "higher" branch of the evolutionary tree had the feathers and one on

2436-413: The skin over the underlying bony structures; there is a very thin layer of subcutaneous tissue between the scute and the skeleton. The scutes can be brightly colored in some species, and turtle shells often follow Thayer's law with carapace usually being a darker patterning than the plastron, though there are exceptions. Moustakas-Verho and Cherepanov's embryological study reveals that the patterning of

2520-404: The "sickle claw", equals 29% of the thighbone length. On the shinbone, the crista fibularis , the crest that contacts the calfbone, is long and lightly built, with a height that does not exceed 9% of the crest length. The upper edge of this crest ends in a hook. On the second metacarpal, of the two condyles that contact the finger, the inner one is almost as large as the outer one. The outer side of

2604-413: The 19th century, wrote that the plastron developed primarily from the sternum of the turtle. This fits well with the knowledge obtained through embryological studies, showing that changes in the pathways of rib development often result in malformation or loss of the plastron. This phenomenon occurs in turtle development, but instead of experiencing complete loss of the sternum the turtle body plan repurposes

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2688-423: The 21st century, when Olivier Rieppel proposed a hypothetical turtle precursor, its back covered by bony armour plates in the dermis, which he called the "Polka Dot Ancestor". Michael Lee proposed that the transformation of the carapace began with an unarmoured parareptile and then an armoured pareiasaur, and ended with modern turtles with a fully developed carapace and a relocated rib cage. The theory accounted for

2772-657: The Black Hills and forced Native Americans onto reservations (see Black Hills land claim ) and left the Sioux with little means to address their grievances. Before he left office, President Cleveland signed a bill on February 22, 1889, splitting the Dakota Territory along the modern borders. This bill was ratified by Congress, and President Harrison signed the paper work to create the US states of North Dakota and South Dakota on November 2, 1889, deliberately signing such that it

2856-598: The Dakotas includes a large portion of the ancestral land of Native American tribes , in particular various tribes of Sioux such as the Dakota people , also known as the Santee Sioux . The United States government stakes its claim to the land through the Louisiana Purchase and Rupert's Land acquisition. The region historically involved a complex series of conflicts between the U.S. government and Native American tribes (and among themselves). The region

2940-529: The U.S. government and the Dakota people. The U.S. won the war, the aftermath which included a mass hanging of 38 people on December 26, 1862, the largest mass execution in U.S. history. The remaining Santee Dakota people were exiled by the U.S. government to the Dakota Territory. The end of the war did not solve the conflicts between Native Americans and the Americans. Fighting would continue, for example along

3024-415: The ability to pull its head into its shell, and had a long neck and a long, spiked tail ending in a club, somewhat like an ankylosaur . Septicemic cutaneous ulcerative disease (SCUD) or "shell rot" causes ulceration of the shell. This is caused by bacteria or fungi entering through an abrasion , and poor animal husbandry . The disease progresses to a septicemic infection causing the degradation of

3108-417: The agile, springy smaller dromaeosaurids and would have been well-suited to running and pursuit predation . The length of the thighbone is 558 millimetres (22.0 in). It is relatively shorter and more lightly built than that of Utahraptor . On the contrary, the shinbone is rather elongated. The holotype shinbone is, with a length of 678 millimetres (26.7 in), the longest dromaeosaurid tibia known. It

3192-486: The ancient Chinese in a type of divination called plastromancy . See also Oracle bones . The turtle's shell is covered in scutes that are made of keratin . The individual scutes as shown above have specific names and are generally consistent across the various species of turtles. Terrestrial tortoises do not shed their scutes. New scutes grow by the addition of keratin layers to the base of each scute. Aquatic chelonii shed individual scutes. The scute effectively forms

3276-419: The animal but also as an identification tool, in particular with fossils, as the shell is one of the likely parts of a turtle to survive fossilization. Hence understanding the shell structure in living species provides comparable material with fossils. The shell of the hawksbill turtle , among other species, has been used as a material for a wide range of small decorative and practical items since antiquity, but

3360-409: The area, as well. The area is mostly inhabited by people of Northern European origin. 44.9% of the population are of German ancestry, 21.8% of Norwegian, and 9.6% are of Irish heritage. Both of the Dakotas have humid continental climate , with warm to hot summers and cold to even subarctic temperatures in winter. Due to the difference in circle of latitude , temperatures differ by degrees between

3444-419: The back are highly pneumatised, filled with trabecular bone that shows many air spaces. On the middle tail vertebrae, the front joint processes, the prezygapophyses , are extremely elongated with an estimated intact length of 70 centimetres (28 in), spanning about ten vertebrae. This helps to stiffen out the tail. The wing of Dakotaraptor was given much attention in the describing article. Here, “wing”

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3528-425: The bone into the form of the plastron, although other analyses find that the endochondral sternum is absent and replaced by the exoskeletal plastron. The ventral ribs are effectively not present, replaced by the plastron, unless the gastralia from which the plastron evolved were once floating ventral ribs. During turtle evolution, there was probably a division of labor between the ribs, which specialized to stabilize

3612-405: The bridge area. They are present in most Pelomedusid turtles. The skeletal elements of the plastron are also largely in pairs. Anteriorly there are two epiplastra, with the hyoplastra behind them. These enclose the singular entoplastron. These make up the front half of the plastron and the hyoplastron contains the anterior bridge strut. The posterior half is made up of two hypoplastra (containing

3696-410: The calfbone, indicating that this fibula must have had a very narrow lower end. The metatarsus has an estimated length of 32 centimetres (13 in), which makes it rather long when compared to the remainder of the leg. The foot claws of Dakotaraptor include a typical dromaeosaurid raptorial second claw, or "sickle claw", which was used for killing or holding down prey. It is large and robust with

3780-409: The carapace is made up of eight pleurals on each side, these are a combination of the ribs and fused dermal bone. Outside of this at the anterior of the shell is the single nuchal bone, a series of twelve paired periphals then extend along each side. At the posterior of the shell is the pygal bone and in front of this nested behind the eighth pleurals is the suprapygal. Between each of the pleurals are

3864-435: The clavicles of other tetrapods. The rest of the plastral bones are homologous to the gastralia of other tetrapods. The plastron has been described as an exoskeleton , like osteoderms of other reptilians; but unlike osteoderms, the plastron also possesses osteoblasts , the osteoid , and the periosteum . The evolution of the plastron has remained more mysterious, though Georges Cuvier, a French naturalist and zoologist in

3948-453: The description of 2015 indicated some additional distinguishing traits. On the fourth foot claw, the boss that serves as an attachment for the tendon of the flexor muscle is reduced in size. The "blood groove" on the outer side of the fourth claw of the foot, towards the tip, is fully enclosed over half of its length, forming a bony tubular structure. The second and third claws of the foot have sharp keels at their undersides. The second foot claw,

4032-467: The evolution of fossil pareisaurs from Bradysaurus to Anthodon , but not for how the ribs could have become attached to the bony dermal plates. Recent stem-turtle fossil discoveries provide a "comprehensive scenario" of the evolution of the turtle's shell. A fossil that may be a stem-turtle from the Permian of South Africa, Eunotosaurus , some 260 million years ago, had a short broad trunk, and

4116-429: The female during copulation. The plastral scutes join along a central seam down the middle of the plastron. The relative lengths of the seam segments can be used to help identify a species of turtle . There are six laterally symmetric pairs of scutes on the plastron: gular, humeral, pectoral, abdominal, femoral, and anal (going from the head to the tail down the seam); the abdominal and gular scute seams are approximately

4200-405: The furcula of Dakotaraptor were U- to V-shaped, suggested by the describers to be similar to many other dromaeosaurids, such as Velociraptor , and even the large spinosaurid theropod Suchomimus . In 2015, a study by Victoria Megan Arbour et al. proposed that the presumed Dakotaraptor furculae in fact represented a part of a turtle’s armor, the entoplastron of Axestemys splendida ,

4284-423: The hand. The second metacarpal of the metacarpus of the hand, the bone that primary remiges attach to, also had a flat bony shelf as its dorsal surface. The shelf made a perfect spot for the primary feathers to lay across in their life-attachment. Overall, the legs of Dakotaraptor are lightly built and have long elements, contrary to the robust, stocky legs of Utahraptor . Dakotaraptor more closely resembles

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4368-420: The larger it was, the greater the slashing strength. Dakotaraptor has a flexor tubercle that is larger relative to overall claw size than it is in other discovered dromaeosaurids, potentially giving it the strongest slashing strength of any known member of this group. The flexor tubercle on the third claw of the foot is almost non-existent, being very reduced in size compared to other dromaeosaurids. This suggests

4452-409: The late Maastrichtian . It consists of a partial skeleton of an adult individual, albeit without a skull. It contains a piece of a back vertebra, ten tail vertebrae, both humeri , both ulnae , both radii , the first and second right metacarpals , three claws of the left hand, a right thighbone, both shinbones, a left astragalus bone , a left calcaneum, the left second, third and fourth metatarsal ,

4536-455: The main differences. However, the soft shell turtles, pig-nose turtles and the leatherback sea turtle have lost the scutes and reduced the ossification of the shell. This leaves the shell covered only by skin . These are all highly aquatic forms. The evolution of the turtle's shell is unique because of how the carapace represents transformed vertebrae and ribs. While other tetrapods have their scapula, or shoulder blades , found outside of

4620-414: The maintenance of Pax1 expression in the ventral sclerotome and thus plays a key role in carapacial rib development. Genetic observations of Pax1 and Shh further provide an understanding in key gene expression that could potentially be responsible for changing turtle morphology. During the development of the turtle embryo , the ribs grow sideways into the carapacial ridge, unique to turtles, entering

4704-411: The modern plastron across these three specimens. In certain families there is a hinge between the pectoral and abdominal scutes allowing the turtle to almost completely enclose itself. In certain species the sex of a testudine can be told by whether the plastron is concave , male or convex , female. This is because of the mating position; the male's concave plastron allows it to more easily mount

4788-436: The most part the sutures between the bones are in the middle of the scutes above. At the anterior of the shell there may be a cervical scute (sometimes incorrectly called a nuchal scute) however the presence or absence of this scute is highly variable, even within species. On the plastron there are two gular scutes at the front, followed by a pair of pectorals, then abdominals, femorals and lastly anals. A particular variation

4872-409: The offer because the land was "never for sale". The two states combined have a population of 1,670,324, slightly less than Idaho , ranking at 39th place. The Dakotas have a total area of 147,878 square miles (383,177 square kilometers), which would rank 4th among U.S. states, right before Montana . The two states also have a population density of 9.8 per sq. mi (3.8 per km ). The Dakotas are within

4956-539: The plastral scutes appear independent from the patterning of carapacial scutes, suggesting that the carapace and plastron evolved separately. The appearance of scutes correlates to the transition from aquatic to terrestrial mode of life in tetrapods during the Carboniferous period (340 Ma). In the evolution from amphibians to terrestrial amniotes, transition in a wide variety of skin structures occurred. Ancestors of turtles likely diverged from amphibians to develop

5040-403: The posterior bridge strut) and the rear is a pair of xiphiplastra. Overlying the boney elements are a series of scutes, which are made of keratin and are a lot like horn or nail tissue. In the center of the carapace are five vertebral scutes and out from these are four pairs of costal scutes. Around the edge of the shell are 12 pairs of marginal scutes. All these scutes are aligned so that for

5124-604: The posterior coracoid and their large and wide terminal phalanges creating shovel-like "hands". Fossoriality may have helped Eunotosaurus survive the global mass extinction at the end of the Permian period, and could have played an essential role in the early evolution of shelled turtles. A stem-turtle from the Middle Triassic of Germany, some 240 million years ago, Pappochelys , has more distinctly broadened ribs, T-shaped in cross-section. They vary in shape along

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5208-525: The posterior pelvis is also part of the carapace, fully fused with it. This is not the case in Cryptodires which have a floating pelvis. The anterior bridge strut and posterior bridge strut are part of the plastron. On the carapace are the sutures into which they insert, known as the Bridge carapace suture. In the shell there is a turtle 's epidermis layer. This layer is important to the strength of

5292-596: The recently performed phylogenetic analysis by Currie and Evans in 2019 , Dakotaraptor was again recovered as an eudromaeosaur, though the authors noted that the holotype may not represent one individual. Atrociraptor Saurornitholestes Dakotaraptor IGM 100/22 and IGM 100/23 Boreonykus Dromaeosaurus Deinonychus Adasaurus Achillobator Utahraptor Acheroraptor Velociraptor mongoliensis Velociraptor osmolskae Linheraptor Tsaagan In their description of Dineobellator , Jasinski et al. (2020) (using

5376-417: The ribcage, the scapula for turtles is found inside the ribcage. The shells of other tetrapods, such as armadillos , are not linked directly to the vertebral column or rib cage allowing the ribs to move freely with the surrounding intercostal muscle. However, analysis of the transitional fossil, Eunotosaurus africanus shows that early ancestors of turtles lost that intercostal muscle usually found between

5460-409: The ribs. The plastron (plural: plastrons or plastra) is the nearly flat part of the shell structure of a turtle , what one would call the belly or ventral surface of the shell. It also includes within its structure the anterior and posterior bridge struts and the bridge of the shell. The plastron is made up of nine bones and the two epiplastra at the anterior border of the plastron are homologous to

5544-470: The right fourth metatarsal, and the second and third claw of the right foot. An assigned furcula was later excluded from the specimen. Apart from the remains of the holotype, bones were discovered in the site that also belonged to Dakotaraptor , but which represented a more gracile morph . These included the specimens PBMNH.P.10.115.T (a right shinbone), PBMNH.P.10.118.T (a connected left astragalus and calcaneum), and KUVP 152429 (originally identified as

5628-405: The same dataset as Currie and Evans (2019)) again recovered this position for Dakotaraptor , but also noted the likely status of Dakotaraptor as a chimaera, casting doubt on this placement as too basal because of the potential composite nature of the taxon. As of 2024, Dakotaraptor cannot be confidently classified as a dromaeosaurid other than being a maniraptoriform. Acheroraptor temertyorum

5712-422: The same length, and the femoral and pectoral seams are approximately the same length. The gular scute or gular projection on a turtle is the most anterior part of the plastron, the underside of the shell. Some tortoises have paired gular scutes , while others have a single undivided gular scute. The gular scutes may be referred to as a gular projection if they stick out like a trowel . The plastral formula

5796-420: The second metacarpal has but a shallow groove for the ligament that connects it to the third metacarpal. When the arm is seen in a flat position, of the second metacarpal, the edge between the wrist joint and the upper shaft is straight in top view. The teeth have fifteen to twenty denticles per 5 millimetres (0.20 in) on the rear edges and twenty to twenty-seven denticles on the front edges. The vertebrae of

5880-475: The shell surrounding it. In an international study, the layer can be as thick as two to four cells. Even with such a small thickness, the epidermis allows the deformation the shell can experience and provides the shell more support. The epidermis layer is apparent in both sections of the shell, carapace, and plastron, and is thicker in critical areas. A thicker epidermis allows a higher stress force to be experienced without permanent deformation or critical failure of

5964-434: The shell. The shape of the shell is from its evolutionary process, which caused many microstructures to appear to aid survival and motion. Shell shape allows the animal to escape predatory situations. Microstructures can include the scutes mentioned prior or the ribs found internally of the shell. Many ribs can be found within the shell and throughout the shell. The rib structures provide extra structural support but allows

6048-401: The shells to deform elastically depending on the situation the turtle is in (i.e., predatory escape). Nonstructural mechanisms have also been in the turtle shell that aids the turtle during locomotion . A mucus film covers parts of the shell, allowing some physical protection and also reducing friction and drag . The bones of the shell are named for standard vertebrate elements. As such

6132-437: The skin to form a hard shell. Exterior to the skin the shell is covered by scutes , which are horny plates made of keratin that protect the shell from scrapes and bruises. A keel , a ridge that runs from front to the back of the animal is present in some species, these may be single, paired or even three rows of them. In most turtles the shell is relatively uniform in structure, species variation in general shape and color being

6216-496: The southern and northern areas, even inside the respective states. The following are the top twenty-two most populous cities in The Dakotas. Pierre, South Dakota, and Bismarck, North Dakota, are the respective state capitals. 46°N 100°W  /  46°N 100°W  / 46; -100 Entoplastron The turtle's shell is an important study, not just because of the apparent protection it provides for

6300-487: The spine. A Late Triassic stem-turtle from Guizhou , China, Eorhynchochelys , is a much larger animal, up to 1.8 metres (5.9 ft) long, with a long tail, and broadened but not overlapping ribs; like the earlier fossils, it has small teeth. Also in the Late Triassic, some 220 million years ago, the freshwater Odontochelys semitestacea of Guangling in southwest China has a partial shell, consisting of

6384-502: The three metacarpal wrist bones, and parts of the finger digits), so the wing is very complete. The humerus , the upper arm bone, is relatively long, slender, and somewhat bent to the inside. The most notable anatomical feature is the row of very prominent bumps along a ridge on the lower edge of the ulna , one of the forearm bones. These are called ulnar papillae, more commonly known as quill knobs. In birds and some other theropod dinosaurs, these bumps were spots for reinforced attachment of

6468-418: The tooth crowns. Andrea Cau noted that, though Dakotaraptor is known from individuals of differing sizes, some of the smaller specimens are also fully mature and it is possible that the size difference means Dakotaraptor is simply a different species or size morph of Acheroraptor . A phylogenetic analysis presented by Cau, mainly relying on fragmentary specimens, did not result in a close relationship between

6552-425: The trunk, and the abdominal muscles, which specialized for respiration, and these changes took place 50 million years before the shell was fully ossified. The discovery of an ancestral turtle fossil, Pappochelys rosinae, provides additional clues as to how the plastron formed. Pappochelys serves as an intermediate form between two early stem-turtles, E. africanus and Odontochelys, the latter of which possesses

6636-424: The turtle stem and on to more crown-ward turtles". Tyler Lyson and colleagues suggest that Eunotosaurus might imply a fossorial origin for the turtles. During the Permian, the broadened ribs may have provided great stability in burrowing, giving a body shape resembling the extant fossorial gopher tortoise , with strong shoulders and forelimbs, and increased muscle attachment structures such as their tubercle on

6720-502: The two. Dakotas The Dakotas , also known as simply Dakota , is a collective term for the U.S. states of North Dakota and South Dakota . It has been used historically to describe the Dakota Territory , and is still used for the collective heritage, culture, geography, fauna, sociology, economy, and cuisine of the two states. The name "Dakota" refers to the Dakota people . The territory now known as

6804-418: Was estimated that a complete series might include fifteen of these papillae ulnares . The ulna is 36 centimetres (14 in) long and the other lower arm bone, the radius, measures 32 centimetres (13 in). The hand bones show that their joints allowed for little mobility. The wingspan of Dakotaraptor was estimated at 120 centimetres (47 in), not taking into account possible primary remiges longer than

6888-571: Was part of the Minnesota and Nebraska territories until 1861. Dakota Territory initially included parts of present day Montana, Nebraska and Wyoming. The fall of 1861 resulted in a poor harvest and was followed by a harsh winter, leading to extreme hardship for the Dakota in the region. Desperate for food and money, they were denied loans by local traders. A series of raids in the spring of 1862 ultimately resulted in Dakota War of 1862 between

6972-720: Was referred to as "sell or starve" by the Native Americans and led to the Great Sioux War of 1876 . The conflict between the Sioux and miners and the U.S. forces backing them would culminate in the Battle of the Little Bighorn , also known as "Custer's Last Stand", the most significant battle of the war. Despite being a Sioux victory, Battle of the Little Bighorn preceded the Agreement of 1877 which took away

7056-540: Was unknown which was officially created first. The debate over the land within the Dakotas, specifically the Black Hills, is unsettled. The Sioux in 1920 began a legal battle over their ancestral lands within the US system of justice. Sixty years later, the US Supreme Court upheld in 1980's United States v. Sioux Nation of Indians case that tribal land was illegally taken from the Sioux and ruled they deserved financial compensation. The Sioux Nation has refused

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