Mosasaur
Mosasaurs (from Latin "Mosa" meaning the 'Meuse river', and Greek σαύρος "sauros" meaning 'lizard') are an extinct group of large marine reptiles containing 38 genera in total. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of the Cretaceous period (Turonian-Maastrichtian ages), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. They became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago.
Jack Horner (paleontologist)
In Montana during the mid-1970s, Horner and his research partner Bob Makela discovered a colonial nesting site of a new dinosaur genus which they named "Maiasaura", or "Good Mother Lizard". The dinosaur bones, originating from a juvenile, were first discovered by Marion Brandvold. Horner then studied the bones, and at first, there was a refusal to return the bones to Brandvold. It contained the first dinosaur eggs in the Western hemisphere, the first dinosaur embryos, and settled questions of whether some dinosaurs were sociable, built nests and cared for their young. The discovery established Horner's career. He has named several other species of dinosaur (including "Orodromeus makelai," in memory of his late friend Bob Makela) and has had three named after himself: "Achelousaurus horneri", "Anasazisaurus horneri", and "Daspletosaurus horneri".
Within the paleontological community, Horner is best known for his work on dinosaur growth research. He has published numerous articles in collaboration with Berkeley paleontologist Kevin Padian, and French dinosaur histologist Armand de Ricqlès, on the growth of dinosaurs using growth series. This usually involves leg bones in graduated sizes from different individuals ranging in age from embryos to adults. Horner also revitalized the contested theory that "Tyrannosaurus rex" was an obligate scavenger, rather than a predatory killer. While this theory has been widely discussed by the popular press, it has never been a major research focus for Horner. He claimed that he never published the scavenger hypothesis in the peer reviewed scientific literature, stating that it was mainly a tool for him to teach a popular audience, particularly children, of the dangers of making assumptions in science (such as assuming "T. rex" was a hunter) without using evidence. In 2000, teams led by Horner discovered five specimens of "T. rex" and three more the following summer, including one larger than the specimen nicknamed "Sue". The new fossil was 10–13 tons in weight and 10% larger than other specimens. The Museum of the Rockies, as the result of continuing fieldwork, now exhibits the largest "Tyrannosaurus rex" collection in the world. Currently, Horner is working on the developmental biology of dinosaurs.