Based off of the previous Spec World expeditions in the past, it was commonly accepted that the last of the lambeosaurines, most notably the massive Sauropodimimus giganticus from Asia, died out during the final days of the Oligocene and before the start of the Miocene. However, a recent expedition to the island Japan have revealed something different that challenges everything once accepted. It should be noted that this is the only dinosaur living on the island.
First appearing in the fossil record over 78 million years ago with Adelolophus hutchisoni, the lambeosaurs eventually became of the most successful groups of hadrosaurs. At the height of the Campanian age, multiple species of them could be seen roaming western North America in large numbers having produced such proud and recognizable beasts like Parasaurolophus, Hypacrosaurus, Corythosaurus, Lambeosaurus and Olorotitan. Eventually these creatures made their way towards Eurasia where they became the dominate species of hadrosaur.
However, by the time of the Maastrichtian, their numbers had begun to drop in North America with comeptition from the likes of more advanced Saurolophines like Kritosaurus, Augustynolophus and the famous Edmontosaurus. However, they were thriving in Asia and Europe with the likes of many species like Pararhabdodon, Olorotitan and Charonosaurus just to name a few examples. However, by the time of the Eocene, the number of Lambeosaurs started to drop like flies, with some arguing that they couldn't adapt to new environments. The final nail in the coffin to the lambeosaurs dynasty would be the extinction of Sauropodimimus giganticus. However, to the surprise of all, it appears that one group of lambeosaurs survived that changing world.
This group of lambeosaurs have adapted to the environments of islands. The most common theory to their survival was isolation from the changing world which allowed them to live and adapt to the small islands while their larger relatives had begun to die out else where in the world. This could be a case of Foster's rule.
Onoatama (Obliticristus insularis)Growing up to lengths of 8-12 feet long, the Onoatama (Obliticristus insularis), literally meaning "axe head" in Japanese, is a small species of lambeosaur native to the island of Japan. Being the only member of its clade, it is believed to be the sole survivor of an once wide spread group of hadrosaurs which dominated the Northern Hemisphere during the final years of the Late Cretaceous and halfway years of the Eocene. Scientists are still figuring out how this species managed to escape extinction, a terrible fate which befell the rest of the Lambeosaurines during the Eocene, finally completed during the Oligocene when Sauropodimimus giganticus from Asia perished as mentioned earlier, while the Saurolophines adapted and evolved into species like the hmungos and singers as time marched forward. Some argue that living in an isolated environment spared the species from extinction, something similar to the likes of non aquatic ankylosaurs which inhabit Papua and Australia, not to mention the fact the in-depth research conducted had confirmed that its ancestry can be traced back all the way to the small Cretaceous lambeosaurine, Nipponosaurus sachalinensis, which was also found in Japan and the small Russian island of Sakhalin.Very few changes have occurred with this relic from a bygone age, the most noticeable exceptions being the change from a small, crested forehead to somewhat tall, arched forehead and slender limbs in adaptation to the island's environment. Some behaviors have been documented, most notably that they are solitary creatures except during mating season in the spring. Another theory in regards for their success is the lack of any major predators, with the exception of the massive mosasaurs that inhabit the coastal areas of Japan, a few species of mammals that prey on the younglings, most notably the pikachilla, and the errosaurid tyrannosaur known as the Oni (Contusisaurus ferox japonicus). This species is also known to display sexual dimorphism, as males have larger crests than females.
Recent analysis have revealed another species of onoatama, the Northern Onoatama (Obliticristus borealis) which can be found on the island of Sakhalin. As of now, not much about it is known, but more research on the area will be conducted sometime in the near-future.