Picture: Mark Witton
The Island Where Life Was Turned Upside Down
This article is part of a series about evolution on islands. Part 1, which provides an overview of the subject, can be found here.
Hateg (pronounced ‘hots egg’) was an island that existed during the late Cretaceous, not long before the dinosaurs went extinct. Today, it is part of Romania and mainland Europe. However, back then, the warmer climate and higher sea levels meant it was 200km (120 miles) away from the nearest landmass, in a giant sea known as Tethys. It was a large, sub-tropical, island about the same size as modern day Hispaniola, approximately 80,000 square kilometres.
As most mainland dinosaurs were already giants, Foster’s Rule meant the common trend was towards dwarfism for those on Hateg. Zalmoxes, a close relation of the Iguanadon that found its way to the island, possibly weighed in at under 100kg, minuscule compared to its 3-ton relative. However, the dwarfish effect was most wonderfully illustrated by the island’s Titanosaurs. Cousins of this clade of sauropods (the grouping that includes Argentinosaurus and Giraffatitan), were evolving into the largest creatures to ever walk the land elsewhere on the planet. However, on Hateg, they were becoming pint-size by comparison…I mean, Magyarosaurus and Paludititan were still 6 metres long and weighed in at over a ton; but compared to the 30+ metre, 80+ ton, Argentinosaurus on the mainland, these things were bloody tiny!
Titchy titanosaurs! (and that other thing I mentioned).
1. Paludititan (by Robert Liesens), 2. Magyarosaurus (size comparison), 3. Zalmoxes (by Danny Cicchetti).
Baluar Bondoc is a strange little dinosaur, closely related to both ancient Dromaeosaurs, like Velociraptor, and Avialans…also known as birds. In fact, where exactly it should be placed has been the centre of much debate. It has lots of weird features that set it apart from any of its kin. If it was a bird it was thicc, it was much more heavily-built than other avians (Balaur Bondoc actually means ‘stocky dragon’ in Romanian). However, its skeleton has lots of subtle features that would make it a downright bizarre Dromaeosaur, elongated toes, shortened fingers, and fused bones that just shouldn’t be there. It even has 2 retractable claws on each foot, instead of the 1 most raptors had.
Initially, scientists were happy to stick Balaur in with the raptors and chalk its oddities up to the fact that we know island evolution gets weird…and whilst they were right about that second part, it might not be for the reasons they initially expected. Other scientists have posited that Balaur is actually a rare example of secondary flightlessness in Paravians. What the hell does that mean?
a) Balaur isn’t a bird or a Dromaeosaur, it’s closely related to both but is its own thing entirely.
b) It’s descendants had, very recently, evolved flight. Which they used to travel to Hateg, before promptly evolving (devolving?) into flightlessness again…suggesting the island trend towards flightlessness in birds is about as old as flying and birds are themselves.
Paravians: pioneers of both flight and flightlessness!
(Artwork by Emily Willoughby)
Despite only being the size of a goose, it’s possible Balaur was one of the apex predators on Hateg (not including the nightmare fuel in the section below). Although, we have never found a fossil skull of the animal, so its diet is hard to determine with any certainty; some believe it may have been an omnivore. Despite being flightless, if it was a hunter, it probably used a similar strategy for killing as modern birds of prey: pinning its victim down with its talons, using its wings for power and balance, and then devouring them alive!
Perhaps, the most spectacular of all the beasts on Hateg were the native pterosaurs, known as Hatzegopteryx. These monsters, as tall as giraffes, were one of the largest creatures to ever take to the air. However, in the absence of large therapod dinosaurs, like Tyrannosaurus, they were also the island’s top land predator. Fossilised footprints show these animals were equally adept on all fours as they were in the sky and, with their enormous size including a 3-metre long skull, it seems they would have had little problem picking off a young Magyarosaurus, or smaller species of Zalmoxes.
Hatzegopteryx had some unique adaptations that allowed it to both tackle this larger prey on the ground and travel around in the air. Despite its giraffe-like size, its neck was actually quite short in relation to its body, when compared to other pterosaurs in its family. Its bones were thicker and it had a broader skull, with more heavy musculature. Whilst such robustness is an excellent adaptation for a top predator, trending in this direction would usually lead towards flightlessness as well, such as in Balaur. Hatzegopteryx was able to get around this evolutionary trap, however, thanks to its unusual bone structure, which was pitted with hollows, separated by bony struts. This was unique among pterosaurs and is similar in structure to Styrofoam. Making Hatzegopteryx’s skeleton both lightweight and durable.
As impressive as they were on the ground, it’s in the skies that these things must have truly been a sight to behold. Their wingspans measured 10-12 metres, as big as a light aircraft, making any flying creature alive today look like a pipsqueak by comparison. An eagle or an albatross might be majestic by our standards but next to Hatzegopteryx they may as well be starlings.
Hateg is just one example from Earth’s past of the oddities of island life, over the coming week we will examine more. Next up, Flores in Indonesia…home to hobbits and hell rats!