Originating from Japanese monster movies like Godzilla, the word “kaiju” is now often used to refer to giant creatures in general – and so it was only a matter of time before a huge sauropod dinosaur was named after the concept.
Kaijutitan maui* was a titanosaur living in Argentina during the Late Cretaceous, about 89-86 million years ago. It’s only known from fragmentary remains, so its full size is difficult to estimate, but it was probably somewhere in the region of 20m long (66′). Nowhere close to the largest sauropod, but possibly one of the heaviest since it does seem to have been rather chunkily built, with stout limbs and an estimated weight of 40-60 tonnes (44-66 US tons).
* Not named for the Polynesian hero, apparently, but for the initials of the Museo Argentino Urquiza.
At the very end of the Cretaceous period, between about 72 and 66 million years ago, tectonic uplift from the start of the formation of the Alps created an island in the area corresponding to modern-day Romania.
Known as Hațeg Island, after the region where fossils of the native species were found, it was similar in size to Hispaniola and was surrounded by deeper waters than most of the other European archipelago islands.
Magyarosaurus here was was a titanosaur living on this island, and was one of the smallest known of all sauropod dinosaurs at just 6m long (19’8″). Much of that length would have been in its neck and tail, and its body was only actually about the size of a horse.
Like some other titanosaurs it had bony osteoderm armor along its back, although since only one isolated piece has been found the exact arrangement isn’t known.
Discovered by Franz Nopsca (the gay Transylvanian baron-paleobiologist-spy), in the early 1900s, it was one of the first dinosaurs proposed as an example of insular dwarfism. Later researchers disagreed with this hypothesis, suggesting instead that the Magyarosaurus fossils were just juveniles – and it wasn’t until 2010 that studies of bone microstructure proved that these miniature sauropods really were fully grown adults.
Sauropod dinosaurs are mainly known for being enormous, and so even some of the smallest members of the group were actually quite large compared to modern animals.
Europasaurus was an early brachiosaurid that lived during the Late Jurassic, about 154 million years ago, on a small island in the Lower Saxony region of northwestern Germany. It was an example of insular dwarfism in a sauropod, only growing to around 6.2m in length (~20′) – less than half the size of some of its other relatives.
A layer of rock just above the deposit of Europasaurus fossils also gives us a clue about their eventual fate. Footprints of large carnivorous theropods – bigger than the mini-sauropods themselves – suggest that at some point the sea level dropped and predators from the mainland were able to reach the island.
Since there were no large predators on the island before then,the small Europasaurus had no defenses against these new giant invaders. They very likely were literally eaten into extinction.
Islands are natural sites for evolutionary experiments. Their isolation and limited resources put a lot of selective pressure on their native species, often resulting in spectacular and unique adaptations. Big animals become small, small animals become big, and ecological niches can end up being filled in unexpected ways.
From the dodo becoming the first well-known example of human-caused extinction, to Darwin’s Galápagos finches being influential in the development of the theory of natural selection, to famous-but-endangered living examples like the kiwi and marine iguana, island species are fascinating and often fragile examples of how diverse life can get even in restricted conditions.
In fact, this theme ended up containing so many species I wanted to feature that I can’t possibly fit them all into just a single month. So, for the first time, a theme is going to need two months – with part 1 happening right now, and part 2 coming later this summer.
For much of the Mesozoic Europe was an archipelago of islands in a shallow tropical sea. During the Late Triassic, about 205-201 million years ago, some of the paleo-islands in this region existed around southern Wales and South West England, near the city of Bristol.
Thecodontosaurus was actually one of the first non-avian dinosaurs ever named by modern science, discovered in the mid 1830s – several years before the term “dinosaur” was even created to classify the “great ancient lizards”.
It was an early member of the herbivorous sauropodomorphs, the group that would eventually include the largest ever land animals. But unlike its enormous later cousins it was short-necked and bipedal, and was particularly small compared to other contemporary “prosauropods”, measuring only about 2m long (6′6″). This would make it one of the oldest known examples of insular dwarfism.
Zby atlanticus, a sauropod dinosaur from the Late Jurassic of Portugal (~156-151 mya). While its genus name might look like a keyboard smash, it was actually named after the Russian-French paleontologist Georges Zbyszewski, who spent much of his career studying Portuguese fossils.
(As for how to pronounce it, according to the original paper it’s “zee-bee”.)
It was a close relative of Turiasaurus, the largest dinosaur currently known from Europe – and although Zby itself wasn’t quite so enormous it was still pretty big, probably measuring somewhere around 15-19m long (49′2″-62′4″).
In fact, all the sauropods known from Late Jurassic Portugal seem to have grown to very large adult sizes. The complete lack of medium or small forms suggests that other types of herbivorous dinosaurs may have dominated the region’s lower-browsing niches at the time.