Adeopapposaurus

Adeopapposaurus (meaning "far eating lizard", in reference to its long neck) is a genus of prosauropod dinosaur from the Early Jurassic Cañón del Colorado Formation of San Juan, Argentina. It was similar to Massospondylus. Four partial skeletons with two partial skulls are known. The type specimen, PVSJ568, includes a skull and most of a skeleton to just past the hips. The form of the bones at the tips of the upper and lower jaws suggests it had keratinous beaks. The fossils now named Adeopapposaurus were first thought to represent South American examples of Massospondylus; while this is no longer the case, Adeopapposaurus is classified as a massospondylid. Adeopapposaurus was described in 2009 by Ricardo N. Martínez. The type species is A. mognai, referring to the Mogna locality where it was found.

Achillobator

Achillobator (pronounced /əˌkɪloʊˈbeɪtɔr/; "Achilles' warrior/hero") is a genus of dromaeosaurid theropod dinosaur from the late Cretaceous Period of what is now Mongolia, about 90 million years ago. It was probably an active bipedal predator, hunting with the large sickle-shaped claw on the second toe of each hind foot. It was a large dromaeosaurid, between 15 and 20 feet (4.6 to 6 meters) from snout to tail.

The generic name comes from Achilles, a famous ancient Greek warrior of the Trojan War, and the Mongolian word bator ("warrior" or "hero"). It refers to the large Achilles tendon needed to use the sickle claw on the foot, which was the major combat organ of dromaeosaurids. The one species is named A. giganticus because it is much larger than most other dromaeosaurids.

Discovery and species

The fossil remains of Achillobator were first discovered during a Mongolian and Russian field expedition in 1989, though it was not described and named until ten years later, in 1999,[1] by Mongolian paleontologist Altangerel Perle, and Americans Mark Norell and Jim Clark, although the description was not complete and was actually published without the knowledge of the latter two authors.[2]

Fossil bones of Achillobator were found mostly disarticulated, but associated, including a fragment of the upper jaw with teeth, as well as vertebrae from all sections of the spinal column, ribs, and bones from the shoulder, pelvis, forelimbs and hindlimbs. These remains were found in the Bayan Shireh Formation of Dornogovi Province, Mongolia, which dates to the Late Cretaceous epoch. The exact age is uncertain, with two competing hypotheses; based on comparisons with other formations, the Bayan Shireh fauna seems to correspond best with the Turonian through early Campanian stages of the Late Cretaceous, about 93 to 80 million years ago.[3] However, examination of the magnetostratigraphy of the formation seems to confirm that the entire Bayan Shireh lies within the Cretaceous Long Normal, which lasted only until the end of the Santonian stage, giving a possible Cenomanian through Santonian age, or between 98 and 83 million years ago.[4] Other dinosaurs found in the Bayan Shireh include Alectrosaurus, Segnosaurus, Talarurus, and Bactrosaurus.

Achelousaurus

Achelousaurus (typically pronounced /əˌkiːloʊˈsɔrəs/, though /ˌækɨˌloʊəˈsɔrəs/ might be a better reflection of the butchered etymology;[1] "Achelous's lizard") is a genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous Period of what is now North America. It was a quadrupedal herbivore with a parrot-like beak, a rough boss (raised bony area) on the snout and two more behind the eyes, and two horns on the end of its long bony neck frill. With a total body length of 6 meters (20 feet), Achelousaurus was a medium-sized ceratopsian.

The genus and the one named species (A. horneri) were both named by paleontologist Scott Sampson in 1995. The specific name honors Jack Horner, an influential American paleontologist famous for his Montana dinosaur discoveries. The generic name Achelousaurus is a complex reference to Greek mythology. Achelous, an important Greek river deity, had one of his horns torn off by Hercules, in a mythological fight with the legendary hero. All three known skulls of Achelousaurus have rough bosses in the same places where other ceratopsians had horns, giving it the appearance of having had its horns ripped off. Achelous was also celebrated for his shapeshifting ability, just as Achelousaurus appears to combine features of other ceratopsian dinosaurs.

Early reports suggested that Achelousaurus represented a transitional form between ceratopsians with modified horns like Einiosaurus (with which A. horneri shares two horns on the end of the frill), and the derived, hornless Pachyrhinosaurus (Horner et al., 1992). While they may or may not form a direct line of descent, all three of these species are at least closely related, and are often united in the tribe Pachyrhinosaurini, inside the subfamily Centrosaurinae and the family Ceratopsidae (Sampson, 1995; Dodson et al., 2004).

Achelousaurus is known from the U.S. state of Montana, in the Two Medicine Formation, which preserves sediments dated from the Campanian stage of the Late Cretaceous Period, between 83 and 74 million years ago. Achelousaurus was found in the highest levels of the formation, so it is probably closer to the end of that timeframe. Other dinosaurs found in this formation include Daspletosaurus, Bambiraptor, Euoplocephalus, Maiasaura, and Einiosaurus.

Scientists have so far recovered three skulls and some postcranial material from the Two Medicine, all housed at the Museum of the Rockies in Bozeman, Montana. The skull of a full-grown Achelousaurus (including the frill horns) is over 5 feet (1.6 meters) long.