Құрып кеткен динозаврлар туысы: Saurornitholestes

Extinct genus of dinosaurs

Saurornitholestes ("lizard bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta) and the United States (Montana, New Mexico, Alabama, North Carolina, and South Carolina). Two species have been named: Saurornitholestes langstoni in 1978 and Saurornitholestes sullivani in 2015. Saurornitholestes was a small bipedal meat eating dinosaur, equipped with a sickle claw on the foot.

In 1974, Canadian amateur paleontologist Irene Vanderloh discovered the skeleton of a small theropod near Steveville in Alberta. She showed it to John Storer of the Provincial Museum of Alberta, who brought it to the attention of Hans Dieter Sues. In 1978, Sues named and described the specimen as the type species Saurornitholestes langstoni. The generic name is in reference to the Saurornithoididae, due to the resemblance with this group that is today seen as part of the Troodontidae, and combines their name with a Greek lestes, "thief". The specific name honours Wann Langston, Jr.

Two more complete and larger partial skeletons (RTMP 88.121.39 and MOR 660), dozens of isolated bones, and scores of teeth are known from the badlands of Dinosaur Provincial Park in Alberta; most of these are housed at the Royal Tyrrell Museum of Palaeontology, in Drumheller, Alberta and remain undescribed. The Alberta and Montana remains are usually attributed to the single species Saurornitholestes langstoni, though they come from a variety of rock formations indicating a wide span of time; for example, the Oldman Formation (dated to about 77 million years ago but whether they represent S. langstoni or a different, related species is unknown. Neonate sized Saurornitholestes fossils have been reported in the scientific literature. Saurornitholestes sullivani is known from the Hunter Wash fauna of the Kirtland Formation in New Mexico, based on the frontal SMP VP 1270. It differs from S. langstoni in the characters of the frontal. A well preserved skeleton of Saurornitholestes (specimen UALVP 55700) discovered in 2014 is currently under preparation by University of Alberta paleontologists working in Japan. After examining the skull of that specimen, Currie and Evans announced in 2019 that the Zapsalis teeth from the Dinosaur Park Formation represented the second premaxillary tooth of S. langstoni.

In 2006, Robert Sullivan named and described a second nominal species, Saurornitholestes robustus, based on holotype SMP VP 1955, a left frontal. The specific name refers to the great thickness of this bone, the only trait in which the species is known to differ from S. langstoni. The holotype was found in the Willow Wash fauna of the Kirtland Formation in New Mexico, dated to about 73 million years ago. and a study published in 2014 took the conclusion a step further by demonstrating that S. robustus was assignable to Troodontidae based on similarities with troodontids. Possible indeterminate fossils are known from the Hell Creek Formation in Montana, North Dakota, and South Dakota, dated to about 66 million years ago.

Saurornitholestes was a small dromaeosaur, with the type species S. langstoni measuring about long and weighing approximately between At the hip it stood tall. Like other theropods in the Dromaeosauridae, Saurornitholestes had a long, curving, blade like claw on the second toe. Saurornitholestes was more long legged and lightly built than other dromaeosaurids such as Velociraptor and Dromaeosaurus. It resembles Velociraptor in having large, fanglike teeth in the front of the jaws. Saurornitholestes most closely resembles Velociraptor, although the precise relationships of the Dromaeosauridae are still relatively poorly understood.

In 1978, Sues assigned Saurornitholestes to the Dromaeosauridae. Later studies most often found it a member of the dromaeosaurid Velociraptorinae, but a cladistic analysis by Philip J. Currie in 2009 recovered a position in a more basal dromaeosaurid clade that was named the Saurornitholestinae. The cladogram below is the result of a 2019 analysis by Philip J. Currie and David C. Evans. Currie and Evans recovered Saurornitholestes as the sister taxon of Atrociraptor. A tooth of Saurornitholestes has been found embedded in the wing bone of a large pterosaur, probably a juvenile Quetzalcoatlus.