Tag: archosaur

Island Weirdness #25 – The Broad-Billed Parrot

The dodo wasn’t the only unique bird to evolve on Mauritius. While about eight other endemic bird species still survive today, there were at least twice that many before the arrival of humans in the late 1500s – including the broad-billed parrot Lophopsittacus mauritianus.

Also referred to as the “Indian raven” in historical accounts, it was a fairly large bird measuring between 45 and 65cm in length (1′6″-2′1″). Unusually for a parrot it had a high degree of sexual dimorphism, with males being significantly bigger than females.

Many images depict it as entirely black or blue-grey, but this seems to be based on a misinterpretation. More recent translations of old Dutch descriptions suggest it was actually much more colorful, with a red beak, blue head, and reddish body.

It had a proportionally big head and a flattened skull, and seems to have had a highly specialized diet, using its its large strong beak to crack open hard seeds and nuts like modern hyacinth macaws.

It was near-flightless, capable of taking to the air only with difficulty, and was said to be “bad-tempered”. Attempts to keep individuals in captivity failed, the birds refusing to eat, and while the wild population had apparently learned to be wary of humans by the late 1660s by that point it was already too late. Much like the dodos they lived alongside, a combination of deforestation, hunting, and predation by invasive mammal species sent them into extinction by the 1680s.

Island Weirdness #24 – The Dodo

Out of all the extinct island species we’ll be covering in this theme, there’s probably none more famous than the dodo (Raphus cucullatus) – a large flightless pigeon about 1m tall (3′3″).

The island of Mauritius was formed from a volcanic hotspot in the Indian Ocean about 10-7 million years ago, in a location roughly 1000km east of Madagascar (~620 miles). The dodo’s smaller flying ancestors must have arrived there sometime after that point via island-hopping from Southeast Asia – the area where its closest living relative the Nicobar pigeon is still found today – and finding themselves in an ecosystem completely lacking terrestrial mammals they quickly evolved to fill a large herbivore niche.

Although frequently depicted as blue-grey, the dodo’s actual life appearance is unknown for certain. No complete preserved specimens have survived into the present day, and contemporary accounts and drawings are somewhat inconsistent – but common elements among them suggest it was more of an earthy brown, with cream-colored primary feathers, yellow legs, a naked pale face, and a green-and-yellow streaked beak. The large white ostrich-like tail plumes shown in many images have also probably been highly exaggerated, since older images depict the dodo with only a tiny tufted tail at best.

Its appearance probably also varied based on the time of year, molting its feathers at the end of summer and being fattest during the breeding season in early spring.

And despite often being stereotyped as a slow dim-witted animal, the proportions of the dodo’s leg bones suggest it was actually quite fast and agile. Its brain-to-body size ratio was also typical compared to other pigeons – which are known to be highly intelligent birds – and it had a well-developed sense of smell.

Sadly this fascinating bird disappeared within only a century of being discovered by humans in the late 1500s. Its “island tameness” due to its lack of natural predators made it easy prey, its forest habitat was rapidly destroyed, and introduced mammal species (such as dogs, pigs, cats, rats, and macaques) competed for its food sources and ate its eggs and young – pressures that its population simply couldn’t hope to recover from all at one.

Its loss wasn’t even properly recognized until much later in the 1800s, but since then it has ironically become immortalized as a icon of human-caused extinction.

Island Weirdness #22 – Aepyornis maximus

Along with a lot of unusual mammals, Madagascar was also home to some of the largest birds to ever exist: the giant elephant birds.

Despite being located so close to mainland Africa, these enormous flightless ratites weren’t the closest relatives of ostriches as might be expected. Instead their closest living relatives are the kiwis of New Zealand, and they must have descended from flying ancestors that reached Madagascar across the Indian Ocean sometime during the early-to-mid Cenozoic.

Aepyornis maximus was one of the biggest of these big birds, standing around 3m tall (9′10″) and weighing over 500kg (1,100 lbs). Its eggs were equally massive, up to 34cm long (1’1″) and with a circumference of over 1m (3′3), making them the largest known eggs laid by any vertebrate.

Recent studies of the shape of its brain within its skull show that it had a good sense of smell but very poor eyesight – possibly being near-blind – suggesting that much like its kiwi relatives it was highly specialized for a nocturnal lifestyle.

There were several other species of elephant bird throughout Madagascar, and at least some of them appear to have successfully survived alongside humans for quite some time. Carbon dating of eggshells suggests they were still alive around 1000 years ago, and based on historical mentions they may have persisted as late as the 1600s before finally disappearing.

Island Weirdness #17 – Tyto gigantea

The largest terrestrial predators on the Late Miocene Gargano-Scontrone island(s) were unusually big hedgehog-relatives, and likewise the local aerial predators also increased in size compared to most of their cousins on the mainland.

Tyto gigantea was a massive barn owl, estimated to have been at least as large as the modern eagle-owl – probably measuring somewhere around 80cm in length (2′7″). It likely grew so big thanks to the lack of competition and in order to keep up with the larger sizes of its prey, since the rodents and pikas of Gargano-Scontrone were also comparative giants.

Alongside the slightly smaller species Tyto robusta it would have been the dominant nocturnal predator on the island(s), while during the daytime the golden-eagle-sized buzzard Garganoaetus occupied the same large-carnivorous-bird niche.

Island Weirdness #16 – Garganornis ballmanni

While some of the main big herbivores on the Late Miocene Gargano-Scontrone island(s) were the larger species of Hoplitomeryx, they weren’t the only animals filling that ecological niche.

Garganornis was an enormous anatid bird, closely related to modern ducks, geese, and swans. Although only known from fragments of its skeleton it’s estimated to have stood up to 1.5m tall (4′11″), making it the largest known waterfowl to have ever lived.

It probably reached such a size thanks to the lack of large terrestrial predators, and possibly also as protection against the island eagles and owls – literally growing too big for them to be able to eat.

It was flightless, with small wings, and had reduced webbing between its toes, suggesting it spent most of its time walking around on land. It also had bony knobs on its wrists that would have been used to give some extra force to wing-slaps when fighting with each other over territory or mates.

Island Weirdness #09 – Hatzegopteryx thambema

There are no big theropod dinosaurs known from the end-Cretaceous Hațeg Island ecosystem, but that doesn’t mean there weren’t any large carnivores at all.

The apex predator niche here instead seems to have been occupied by Hatzegopteryx, an enormous azhdarchid pterosaur. Standing up to 4.5m tall (14’9″) when on the ground, and with an estimated wingspan rivaling Quetzalcoatlus (~11m / 36′), it was one of the largest animals to ever fly – although like other azhdarchids it probably actually spent most of its time stalking around quadrupedally on the ground eating whatever it could fit into its mouth.

Its neck was shorter and chunkier than most other azhdarchids, and its skull was wider and more massively built. The walls of its hollow bones were also unusually thick and reinforced for a pterosaur, so much so that they were initially mistaken for those of a theropod instead.

Fossils of Hatzegopteryx are very fragmentary, however, so its full appearance and the specifics of its diet are still uncertain. But it would have probably been able to tackle much larger prey than other azhdarchids, possibly capable of using its sturdy beak to bludgeon or stab anything too big to pick up and swallow whole in a similar manner to modern marabou storks.

Island Weirdness #08 – Balaur bondoc

When Balaur was described in 2010 it was initially thought to be a dromaesaurid closely related to Asian forms like Velociraptor. With its particularly stocky legs built for strength rather than speed, two-fingered hands, and two large sickle claws on each foot, it was interpreted as a weird highly specialized predator terrorizing the other Hațeg Island species at the end of the Cretaceous. Although only 1.8m long (5’10”), it was hypothesized to have taken down prey much larger than itself with powerful slashing kicks.

But later analyses cast doubt on this interpretation.

A lot of the anatomical features of Balaur’s skeleton were odd for a dromaeosaurid, but matched those of avialans – a group of close evolutionary “cousins” to the dromaeosaurids, containing Archaeopteryx and the common ancestors of all modern birds. And, by 2015, multiple studies had confirmed Balaur wasn’t really a “raptor” but instead a little further along on the bird lineage.

So now our picture of this dinosaur is very different: a chunky-bodied island bird, grown large and secondarily flightless sort of like a Cretaceous equivalent to the dodo. Its double sickle claws were probably adaptations for climbing and perching in trees, and based on similar avialans it was likely a herbivore rather than a hypercarnivore.

Island Weirdness #07 – Telmatosaurus transsylvanicus

The hadrosauroid dinosaur Telmatosaurus was another resident of Hațeg Island, and while it wasn’t quite as small or specialized as its cousin Tethyshadros it was still dwarfed compared to their other relatives, only growing to about 5m long (16’4″).

It was also the first dinosaur fossil found with a specific type of non-cancerous tumor known as an ameloblastoma on its lower jaw – a surprising discovery, since ameloblastomas were previously only known to occur in mammals and a single snake species. Various other types of abnormal tissue growth have been identified in other hadrosauroids and hadrosaurs, however, suggesting that this particular lineage of dinosaurs may have been unusually susceptible to developing tumors.

Island Weirdness #06 – Zalmoxes robustus

Hațeg Island was home to quite a few unique species right at the end of the Cretaceous, so we’ll be focusing on it for a few more days.

Zalmoxes robusutus was a member of the rhabdodontids, a group of herbivorous ornithopod dinosaurs related to well-known names like Iguanodon, Tenontosaurus, and the hadrosaurs.

It had a chunkier build than its closest relatives, with a deep skull, a large beak, and a rotund body. Like other rhabdodontids it would have had powerful jaw muscles and ridged cheek teeth specialized for scissoring, adaptations for cutting up particularly tough plant matter.

It was also quite small, about 2.4m long (7’10”), although since the largest known fossils represent subadults this may not have been its full size. A second species in the same genus (Zalmoxes shqiperorum) lived on the same island and was actually slightly bigger, suggesting that Z. robustus represented a minor case of insular dwarfism.

Island Weirdness #05 – Magyarosaurus dacus

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.