remained small, not exceeding wingspans during the Late Cretaceous (most pterosaurs during this time had larger wingspans, and thereby avoided the small-size niche). To these researchers, this indicated that the extinction of pterosaurs was abrupt instead of gradual, caused by the catastrophic Chicxulub impact. Their extinction freed up more niches that were then filled by birds, which led to their evolutionary radiation in the Early Cenozoic. Locomotion Witton summarized ideas about azhdarchid flight abilities in 2013, and noted they had generally been considered adapted for soaring, although some have found it possible their musculature allowed flapping flight like in swans and geese. Their short and potentially broad wings may have been suited for flying in terrestrial environments, as this is similar to some large, terrestrially soaring birds. Albatross-like soaring has also been suggested, but Witton thought this unlikely due to the supposed terrestrial bias of their fossils and adaptations for foraging on the ground. Studies of azhdarchid flight abilities indicate they would have been able to fly for long and probably fast (especially if they had an adequate amount of fat and muscle as nourishment), so that geographical barriers would not present obstacles. Azhdarchids are also the only group of pterosaurs to which trackways have been assigned, such as Haenamichnus from Korea, which matches this group in shape, age, and size. One long trackway of this kind shows that azhdarchids walked with their limbs held directly underneath their body, and along with the morphology of their feet indicates they were more proficient on the ground than other pterosaurs. According to Witton, their proportions indicate they were not good swimmers on the other hand, and though they could probably launch from water, they were not as good at this as some other pterosaur groups. Paleoenvironment Phosphatodraco is known from the "couche III" phosphatic unit of the Ouled Abdoun Basin in Morocco, which was deposited during the late Maastrichtian age of the Late Cretaceous period, which ended 66 million years ago. The phosphatic series is condensed and the Maastrichtian part is only thick. From the bottom to the top, "couche III" consists of thin phosphatic levels and marls, a grey limestone bed containing fish fossils, yellow, soft phosphates at the lower level, a thick, yellow marly level, separating the lower and upper "couche III", and gray, soft phosphates with brown stripes overlay in a thick marl level at upper "couche III". Pterosaur