the ceratopsian Serendipaceratops which could be an ankylosaur, and the difficult-to-classify theropod Timimus have consequently been made. The supercontinent Pangaea of the Jurassic allowed major dinosaur clades to achieve a global distribution before breaking up, and several closely related cognates existed between South Polar forms and forms found elsewhere despite separation by the Tethys Ocean. However, dinosaur groups that achieved pan-Gondwanan distribution over the course of the Cretaceous would have had to have used the land bridge connecting Australia to South America via Antarctica in the South Polar region. The South Polar iguanodontian Muttaburrasaurus is most closely related to European rhabdodontids, which were the dominant group in Europe during the Late Cretaceous. The Cretaceous South Polar Kunbarrasaurus is identified as being part of a unique lineage of Gondwanan ankylosaurs, which suggests homogeneity in the Gondwanan fauna. The Dromaeosauridae are known from Antarctica, and represent a relict population from a previously world-wide distribution. Despite these apparent cross-continental migrations, it is unlikely that South Polar dinosaurs migrated out of the polar forests during the winter, as they were either too massive–such as ankylosaurs–or too small–such as troodontids–to travel long distances, and a large sea between East Gondwana and other continents impeded any such migrations in the Late Cretaceous. It is possible, to cope with the winter conditions, some dinosaurs hibernated, such as the theropod Timimus. The most common and diverse group found so far are the hypsilophodont-like dinosaurs, making up half of the dinosaur taxa found in southeastern Australia, which is unseen in more tropical regions, perhaps indicating some kind of advantage over other dinosaurs in the poles. Being small with grinding dentition, they likely fed on low-lying vegetation such as lycopods and podocarp seed pods. The hypsilophodont-like Leaellynasaura had large eye sockets, larger than more tropical hypsilophodont-like dinosaurs, and may have had acute night vision, suggesting that Leaellynasaura, and perhaps other hypsilophodont-like dinosaurs, lived in the polar areas for year-round or most of the year, including polar winters. Bonegrowth was continuous throughout its life, indicating it did not hibernate, being possible by perhaps being endothermic or poikilothermic, or by digging burrows. However, it is possible that the large eyes are merely due to ontogenesis, that is, relatively large eye-sockets may have been a feature only seen in juveniles or perhaps was a birth-defect, since there is only one specimen known. Though remains are scant and, consequently, taxonomic descriptions can be dubious,