spent their early years of life out in the open ocean, not in sheltered nurseries or areas such as shallow water as previously believed. Whether mosasaurs provided parental care, like other marine reptiles such as plesiosaurs, is currently unknown. The discovery of young mosasaurs was published in the journal Palaeontology. Possible eggs A 2020 study published in Nature described a large fossilized hatched egg from Antarctica from the very end of the Cretaceous, about 68 million years ago. The egg is considered one of the largest amniote eggs ever known, rivalling that of the elephant bird, and due to its soft, thin, folded texture, it likely belonged to a marine animal. While the organism that produced it remains unknown, the egg's pore structure is very similar to that of extant lepidosaurs such as lizards and snakes, and presence of mosasaur fossils nearby indicates that it may have been a mosasaur egg. It is unknown whether the egg was laid on land or in the water. The egg was assigned to the newly described oospecies Antarcticoolithus bradyi. Environment Paleontologists compared the taxonomic diversity and patterns of morphological disparity in mosasaurs with sea level, sea surface temperature, and stable carbon isotope curves for the Upper Cretaceous to explore factors that may have influenced their evolution. No single factor unambiguously accounts for all radiations, diversification, and extinctions; however, the broader patterns of taxonomic diversification and morphological disparity point to niche differentiation in a "fishing up" scenario under the influence of "bottom-up" selective pressures. The most likely driving force in mosasaur evolution was high productivity in the Late Cretaceous, driven by tectonically controlled sea levels and climatically controlled ocean stratification and nutrient delivery. When productivity collapsed at the end of the Cretaceous, coincident with bolide impact, mosasaurs became extinct. Sea levels were high during the Cretaceous period, causing marine transgressions in many parts of the world, and a great inland seaway in what is now North America. Mosasaur fossils have been found in the Netherlands, Belgium, Denmark, Portugal, Sweden, South Africa, Spain, France, Germany, Poland, the Czech Republic, Italy Bulgaria, the United Kingdom, Russia, Ukraine, Kazakhstan, Azerbaijan, Japan, Egypt, Israel, Jordan, Syria, Turkey, Niger, Angola, Morocco, Australia, New Zealand, and on Vega Island off the coast of Antarctica. Tooth taxon Globidens timorensis is known from the island of Timor; however, the phylogenetic placement of this species is uncertain and it might not even be