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.
Nyasasaurus
"Nyasasaurus" is likely either a basal dinosaur or close to Dinosauria. Other phylogenetic analyses have indicated that the sister group to Dinosauria is a family of herbivorous dinosauriforms called Silesauridae. The fossil record of silesaurids dates back to the late Anisian (the silesaurid "Asilisaurus" is also known from the Manda Formation), suggesting that the first dinosaurs also appeared around this time. Before "Nyasasaurus" was recognized as a possible dinosaur, a long ghost lineage of approximately 16 million years existed between the earliest dinosaurs and earliest silesaurids.