Дат кәсірлі динозавр: Dromaeosauroides bornholmensis

Genus of dromaeosaurid theropod dinosaur from the Early Cretaceous

Dromaeosauroides is a genus of dromaeosaurid theropod dinosaur from the Early Cretaceous of what is now Denmark and possibly also England. It was discovered in the Jydegaard Formation in the Robbedale valley, on the island of Bornholm in the Baltic Sea. This is the only likely place for dinosaur remains to be discovered on Danish territory, since the Mesozoic deposits exposed in the rest of the country are marine. Dromaeosauroides is the first known dinosaur from Denmark, and the only one which has been scientifically named. It is one of the oldest known dromaeosaurs in the world, and the first known uncontested dromaeosaur from the Early Cretaceous of Europe. It is known from two teeth, the first of which was found in 2000 and the second in 2008. Based on the first tooth (the holotype), the genus and species Dromaeosauroides bornholmensis was named in 2003. The genus name means "Dromaeosaurus like", due to the similarity to the teeth of that genus, and the species name means "from Bornholm". After this discovery, remains and tracks of more dinosaurs were found in several formations on Bornholm. Some teeth from the United Kingdom that have been referred to the genus Nuthetes may also belong to this animal. Coprolites containing fish remains found in the Jydegaard Formation may belong to Dromaeosauroides. The holotype tooth is long, and the second tooth is They are curved and finely serrated. In life, Dromaeosauroides would have been in length, and weighed about As a dromaeosaur it would have been feathered, and had a large sickle claw on its feet like its relatives Dromaeosaurus and Deinonychus. It lived in a coastal lagoon environment with sauropods, as evidenced by a possible titanosaur tooth.

Few dinosaur remains have been found in Scandinavia. The mainland of western Denmark is an unlikely region to find dinosaur remains, since the Mesozoic sediments there are marine Maastrichtian chalk. Fossils of non dinosaurian marine animals, including mosasaurs and plesiosaurs, have been found in these deposits. The tooth was presented at the 45th annual meeting of the Palaeontological Association in 2001, and identified as a dromaeosaur. In 2003 the tooth (MGUH 27218/DK 315) was made the holotype specimen of Dromaeosauroides bornholmensis—named and described by Christiansen and Bonde. The genus name combines Dromaeosaurus with the Greek ides ("in the form of"), referring to the resemblance between the teeth of the two genera. The specific name refers to Bornholm. The name Dromaeosaurus itself has been translated as "swift" or "running reptile". Bonde and Christiansen had expected the first Danish dinosaur remains to be teeth of herbivorous dinosaurs such as hypsilophodonts or Iguanodon, and were surprised to find a dromaeosaur tooth instead, since these are rare in Early Cretaceous formations; herbivores would have been more abundant than carnivores. This specimen (DK 559) was found in the same location, and later assigned to D. bornholmensis as well. In a press release, the second dromaeosaur tooth was also certified Danekræ by the Natural History Museum of Denmark, which compared the animal to the raptors in the film Jurassic Park, noting that the animals, unlike the film's raptors, would have been feathered. and sauropod tracks were also reported from the formation that year. In 2011, footprints of a sauropod, a thyreophoran and a theropod were reported from the Bagå Formation. Lower Jurassic tracks reported form the Rønne Formation in 2014 are the earliest evidence of dinosaur activity in Denmark. A tooth from the multituberculate Sunnyodon was found in the Rabekke Formation in 2004, making it the first known Danish and Scandinavian Mesozoic mammal. A tooth of a turiasaurian sauropod was reported from the Lower Jurassic Hasle Formation in 2023. In 2012, Jesper Milàn and colleagues described two coprolites (fossilised faeces) containing fish scales and bones. They were found in the Jydegaard Formation, the first such fossils found in Danish continental Mesozoic deposits. Although the producer of these faeces cannot be identified with certainty, marine turtles and dromaeosaurids such as Dromaeosauroides are the most likely candidates.

Fossil theropod teeth are typically identified according to features including size, proportion, curvature of the crown and the morphology and number of denticles (serrations). The holotype of D. bornholmensis is a tooth crown long, from front to back and wide at the base. The front part of the tooth was worn, indicating that it was shed when the animal was alive. It was further affected by taphonomic wear; the base of the tooth is irregular, so it may have been slightly longer in life. The second known tooth is smaller——with the same features as the holotype. As a dromaeosaur, Dromaeosauroides would have had a large sickle claw on its highly mobile second toe, like its relatives Dromaeosaurus, Velociraptor and Deinonychus. That group is closely related to birds, and the NaturBornholm interpretive centre houses a roughly life sized sculpture of Dromaeosauroides covered in feathers. Later Chinese finds of well preserved feathered dromaeosaurs indicate that the sculpture should have more and longer feathers to be accurate. Although some smaller dromaeosaurs may have been able to fly, flight was unlikely for an animal the size of Dromaeosauroides.

Several features of the tooth are only known from members of the family Dromaeosauridae of theropod dinosaurs. Dromaeosauroides was considered an indeterminate dromaeosaur by Johan Lindgren and colleagues in 2008. Nicholas R. Longrich and colleagues stated in 2021 that Dromaeosauroides may have been an early eudromaeosaur.

Only a corner of the Jydegaard Formation is exposed today; the remainder is overgrown. Jydegaard is part of the Nyker Group, which includes three formations (Rabekke, Robbedale, and Jydegaard) ranging from the Berriasian to the Valanginian ages of the Early Cretaceous. Jydegaard consists of sediments deposited in a fresh to brackish lagoon facing a coastal strip. In addition to Dromaeosauroides and a possible titanosaur, remains of hybodont sharks, fish such as Lepidotes and Pleuropholis, turtles, lizards, the crocodile Pholidosaurus and thin bone fragments from birds or pterosaurs have been found in the deposit. The fish and bivalves were found in clay which was probably a lagoon, and the dinosaurs and lizards in sand which probably was land, perhaps a beach; turtles and crocodiles were found in both. Freshwater snails were found in clay that may have been shallow, drying lakes behind a sandy barrier between lagoon and sea, in a setting perhaps similar to the Florida Keys or the southwestern coast of Jutland. Dinosaurs may have fed there, based on the remains of plants and small land animals, and theropods may have hunted along the shore. Bornholm and Scania appear to be the only places were remains of the Scandinavian Russian fauna of the Early Cretaceous can be found. Further investigations there may show whether this fauna has European or Asian affinities. Based on possible dromaeosaur coprolites from the Jydegaard Formation, which contained scales of the fish Lepidotes, Milàn and colleagues speculated that some dromaeosaurids were able to catch fish with the enlarged sickle claw on the second digit of the foot, similar to the "spear fishing" that has been proposed for the theropod Baryonyx and its enlarged thumb claw. The larger of the two coprolites has evidence of coprophagous organisms.