Жоқ мұрын мүйізді динозавр - Arrhinoceratops туралы

Extinct species of dinosaurs

Arrhinoceratops (meaning "no nose horn face", derived from the Ancient Greek "a /α " "no", rhis/ῥίς "nose" "keras/κέρας" "horn", " ops/ὤψ" "face") is a genus of herbivorous ceratopsian dinosaur. The name was coined as its original describer concluded it was special because the nose horn was not a separate bone, however further analysis revealed this was based on a misunderstanding. Parks named the type species Arrhinoceratops brachyops. The generic name is derived from Greek α~, "without", ῥίς, rhis, "nose", κέρας, keras, "horn", and ὤψ, ops, "face" as Parks had established that no separate nose horn was present. The specific name means "short faced" from Greek βραχύς, brachys, "short". In 1976, Douglas A. Lawson transferred the species to Torosaurus, as a Torosaurus utahensis. Apart from the holotype skull little fossil material of Arrhinoceratops brachyops has been found. In 1981 Helen Tyson in a revision of the genus, provisionally referred specimen ROM 1439, but in 2007 Andrew Farke moved this to Torosaurus.

Since this dinosaur is known only from its skull, scientists have few data about its overall anatomy. The skull, as restored, features a broad, square, neck frill with two oval shaped openings. Already Richard Swann Lull had in 1933 been politely critical of Parks' original description, and Tyson discovered that Parks, an entomologist, had made many mistakes. The most notable of these was that the very trait the genus was named after, the lack of a separate ossification or os epinasale for the nose horn, is in fact normal for the ceratopsids, in which group this horn is an outgrowth of the nasal bone, not a distinct element. Other incorrect observations by Parks included the conclusion that the os rostrale, the bone core of the upper beak, directly touched the nasals instead of being separated from them by the premaxillae; a presumed anterior process of the jugal touching the premaxilla; and thinking that the interparietal bar of the frill presented a separate skeletal element, an os interparietale. Tyson concluded it was closely related to Torosaurus, probably even its direct ancestor. Cladistic analyses recover it close to Anchiceratops. The following cladogram shows the phylogeny of Arrhinoceratops according to a study by Scott Sampson e. a. in 2010.

Arrhinoceratops lived in a wet coast land with warm summers but cool winters. It was likely preyed upon by Albertosaurus. Arrhinoceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles. Its habitat was densely forested.