(meaning "separated Kritosaurus lizard"; sometimes misinterpreted as "noble lizard", in reference to the presumed "Roman nose"; the nasal region was fragmented, disarticulated, and originally restored flat) is an incompletely known but historically important genus of extinct hadrosaurid (duckbilled) dinosaur. It lived about 73 million years ago, during the Late Cretaceous of North and possibly South America. Its taxonomic history is convoluted, also incorporating , Gryposaurus , and Anasazisaurus ; this tangle will remain unresolved until better remains of Naashoibitosaurus Kritosaurus are described. Despite the dearth of material, this herbivore appeared in dinosaur books until the 1990s, although what was usually represented was the much more completely known Gryposaurus, then thought to be a synonym. In 1904, Barnum Brown discovered the type specimen ( AMNH 5799) of Kritosaurus near Ojo Alamo, San Juan County, New Mexico, United States, while following up on a previous expedition. He initially could not definitely correlate the stratigraphy, but by 1916 was able to establish it as from what is now known as the late Campanian-age De-na-zin Member of the Kirtland Formation.
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is an American Paul Sereno paleontologist who is the discoverer of several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco and Niger. He is a professor at the University of Chicago and a National Geographic "explorer-in-residence." Sereno's most widely publicized discovery is that of a nearly complete specimen of (popularly known as SuperCroc) at Gadoufaoua in the Tenere desert of Niger. Other major discoveries include Sarcosuchus imperator - the oldest known dinosaur fossil, Eoraptor , the first good skull of Jobaria , Carcharodontosaurus iguidensis , Afrovenator and the African Suchomimus pterosaur.
Fossilized brains are unusual, and this is by far the oldest known example."
— John Maisey, Curator in the Division of Paleontology at the AMNH describing the discovery of the .
oldest known fossil brain
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, meaning ("Spiral Saw"), is an Helicoprion extinct genus of whorl-toothed shark that first arose in the oceans of the Late Carboniferous, approximately 280 million years ago, and survived the Permian-Triassic extinction event, and eventually went extinct during the Early Triassic, some 225 million years ago. Its fossils can be found in Russia and in the Western U.S. but no other part of the jaw or shark has ever been found. The type species, , was discovered and described in the H. bessonovi Ural Mountains of Russia in 1899 by Russian paleontologist Andrzej P. Karpinski. The type specimen is a holotype based upon a single tooth-whorl. The tooth-whorl has puzzled paleontologists for decades, as it was unknown as to where it fit into the jaw, until a modern reconstruction determined that the most feasible place was within the shark's mouth.
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