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Island Weirdness #37 — Natunaornis gigoura

The islands of Fiji are located in the South Pacific, a couple of thousand kilometers east of Australia and northeast of New Zealand. Formed via volcanic activity, the over 300 islands making up the archipelago had no native land mammals for most of their history, leading to birds, reptiles, and amphibians taking up the large animal niches in the ecosystem.

Subfossil remains of a unique mix of species have been found on Viti Levu, the largest of the Fijian islands — including a flightless megapode, a sylviornithid, a big frog, a giant iguana, a terrestrial crocodilian, and a meolaniid tortoise.

One of the most surprising discoveries, however, was actually a pigeon.

Natunaornis gigoura was by far the biggest pigeon known from any Pacific island, and one of the largest pigeons to ever live, being almost the same size as the Mauritian dodo at around 0.9m tall (3′). But unlike its distant cousin it still looked very much like a scaled-up normal pigeon, probably resembling a giant version of the closely related modern crowned pigeons.

It had reduced wings and strong legs, indicating it was flightless, and an unspecialized beak that suggests it was a generalist forager eating fallen fruit, seeds, and invertebrates from the forest floor.

Natunaornis existed well into the Holocene, but like many other island dwellers it was severely affected by the arrival of humans. Austronesian peoples reached Fiji somewhere between 3500 BCE and 1000 BCE, and it’s likely that a combination of hunting and predation from introduced mammals rapidly killed off the giant pigeons along with all the other large native species.

Island Weirdness #36 — Haast’s Eagle

Before the arrival of humans in New Zealand, the only predator of the native giant flightless birds was Haast’s eagle (Hieraaetus moorei), an enormous species of raptor from the South Island.

With the slightly larger females reaching lengths of around 1.4m (4’7″) and hefty body weights of 15kg (33lbs), it was the largest eagle known to have ever lived, and one of the largest of all birds of prey. Yet its wings were actually proportionally short for its size, spanning about 2.5m (8’2″), giving it less ability to soar but much better maneuverability when flying in the thick vegetation of scrubland and forests.

Its closest living relatives are the much smaller Australian little eagle and the Palearctic booted eagle, which its lineage split from sometime in the Pleistocene — meaning that it must have evolved to be so huge incredibly quickly.

At its size and weight when striking it would have hit its prey with a force equivalent to a falling cinder block, and with no major competitors it could have fed from a single large kill for many days.

As apex predators Haast’s eagles would also have never been particularly numerous, and their population was very sensitive to the availability of their prey species.

Unfortunately the early Māori people also found the large flightless birds like the moa to be delicious easy meals, and by the early 1400s the eagle had disappeared alongside its main food sources. Legends about a giant human-eating bird called the pouakai are thought to be based on folk memory of Haast’s eagle, and it may well have occasionally preyed on the settlers during the short time it coexisted with them.

Island Weirdness #35 — Flightless Giants

With the lack of large terrestrial mammals in New Zealand, birds were free to exploit the “big herbivore” niches in the ecosystem — and the giant moa were the ultimate result.

Closely related to modern South American tinamous, the ancestors of moa were small flying birds that arrived in New Zealand sometime in the early Cenozoic. At the time of the Miocene St Bathans fossil deposits they were already large and flightless, and by the Holocene they had grown truly enormous.

Uniquely they completely lost their wings, not even having the tiny vestigial bones seen in other large flightless birds.

A stylized illustration of an extinct giant flightless bird. It has a tiny head with a downward-curving beak, a long neck, no wings at all, and long chunky legs. — Dinornis robustus

The South Island giant moa (Dinornis robustus) was the largest of them all, with females standing almost 2m tall at the back (6’6″) and able to reach their heads up to heights of around 3.6m (11’10”). It had a long neck, a relatively tiny head with a curved beak, and large powerful legs — and preserved hair-like body feathers show that it was reddish-brown in color.

It also had some of the most extreme sexual dimorphism seen in any bird species, with the males being significantly smaller than the females at only about 1.2m tall (3’11”). This seems to have been the result of scaling-up smaller differences in body size from their ancestors.

A stylized illustration of an extinct flightless bird. It has a triangular downward curving beak, a long neck, small wings, and short stout legs. — Aptornis defossor

The adzebills were another odd group of big flightless birds whose ancestors also date back to sometime before the St Bathans deposits. They had large downward-curving beaks, short strong legs, and highly reduced wings that were smaller proportionally than those of the dodo.

They were less common than the moa, found only the drier forested parts of the lowlands, and based on isotope analysis of their bones they seem to have been predators hunting invertebrates, reptiles, and smaller birds.

When their remains were first discovered they were even thought to be a type of moa, but later studies (including recovered ancient DNA) have shown they were actually gruiformes, with their closest living relatives being either the South American trumpeters or the African flufftails.

The South Island adzebill (Aptornis defossor) was the slightly larger of the two species known from the Holocene, reaching sizes of about 0.8-1m tall (2’8″-3’3″).

The ancestors of the Māori people arrived in New Zealand around the year 1300, and sadly within about a century a combination of human hunting pressure and predation by introduced mammals sent both the moa and adzebills into total extinction.

Island Weirdness #34 — Heracles inexpectatus

New Zealand is probably one of the most famous modern examples of a unique island ecosystem, having been isolated for the last 80 million years. Lacking any living terrestrial mammals, birds instead became the dominant land animals, adapting to a wide range of niches and evolving unusual flightless forms like the modern kiwi and kākāpō.

The St Bathans fossil site on the South Island dates to the early Miocene, about 19 to 16 million years ago, just after a period known as the “Oligocene drowning” when large portions of the landmass were underwater. It gives us a glimpse of an ancient version of New Zealand when the ecosystem was recovering and rapidly diversifying in a then-subtropical climate, and has produced a wide range of new fossil species (including a mysterious mammal).

One of the most recent discoveries from the site is Heracles inexpectatus, a close relative of the modern New Zealand parrots — but significantly larger than any living species, estimated to have stood almost 1m tall (3’3″). Known from just a few leg bones, the fossils were so big that they initially weren’t even recognized as belonging to a parrot, instead being mistaken for a large eagle before their true nature was realized.

At such a size it would likely have been flightless, although it may have still been capable of climbing trees and gliding. Much like the modern kea it was probably an omnivore, using its large curved beak and powerful crunching bite to eat pretty much whatever it wanted.

By the late Miocene, around 13 million years ago, New Zealand’s climate rapidly shifted cooler and drier, and the tropical forests were quickly replaced with temperate ones. This changing habitat may have been too much too fast for the giant parrots to deal with, and they went extinct alongside many of the other St Bathans species.

Kalligrammatids

Did you know butterflies weren’t the first insects to look like butterflies?

Lepidopterans (the group of insects containing moths and butterflies) have been around since the Late Triassic – but it wasn’t until the diversification of flowering plants during the Cretaceous that recognizable moths would have evolved, and true butterflies didn’t actually appear until the early Cenozoic.

Before then, back in the mid-Jurassic about 165 million years ago, a completely different group of insects convergently evolved remarkably butterfly-like features such as large colorful scaled wings and long sucking proboscises.

Known as the kalligrammatids, these insects were giant members of the lacewing group, related to modern forms like antlions and owlflies. But unlike their predatory relatives the kalligrammatids were specialized pollinators, possibly having a mutualistic relationship with the flower-like cones of bennettitales or the pollination drops of some types of conifers. They seem to have originated in China and were found across Asia and Europe by the Late Jurassic, but a few fossils from South America suggest they were even more widespread and may just have a poor fossil record.

They reached wingspans of up to 16cm (~6″), comparable to some of the largest modern butterflies, and often sported conspicuous anti-predator markings on their wings such as stripes and eyespots – so it’s not surprising that they’re often nicknamed the “butterflies of the Jurassic”.

Rather ironically, the extinction of the kalligrammatids was probably linked to the rise of the flowering plants that the true butterflies would later be so dependent on. As flowers diversified and plants like the bennettitales declined, the kalligrammatids dwindled and disappeared, with the last known fossil record coming from the mid-Cretaceous of Brazil about 113 million years ago.

But while they were around, I do wonder if they also exhibited some similar behaviors – such as mud-puddling for extra nutrients, and specifically the habit of drinking the tears of larger animals that we see in some species. Perhaps some non-avian dinosaurs like this Dilong occasionally put up with kalligrammatids sitting on their faces!

Tarsomordeo

While modern crocodilians are all semi-aquatic, their Mesozoic ancestors (known as neosuchians) started off fully terrestrial, only really moving into their familiar water-based ecological niches around the mid-Jurassic when the dinosaurs were dominating on land.

But on multiple occasions members of the neosuchian croc lineage independently went back to fully terrestrial habits, and Tarsomordeo winkleri here is one of the most recently discovered examples.

Living about 113 million years ago in the Early Cretaceous of central Texas, USA, Tarsomordeo was surprisingly small, only about 60cm long (2′) – the size of an average cat. Its tiny size even ended up inspiring its name, which translates to “ankle biter”.

It had long slender limbs held in an upright posture, suggesting it was a swift and agile runner capable of chasing after fast-moving prey. Since it lived in a semi-arid environment that seems to have been a major nesting site for the herbivorous Convolosaurus, their hatchlings probably also made up a large part of its diet during the breeding season.

Vespersaurus

For around 50 years some very unusual dinosaur tracks have been found in ancient desert sediments in South America: strange footprints showing the impression of only a single toe, a walking style never before seen in any reptiles.

And recently a fossil of what might be the track maker has actually been found.

Named Vespersaurus paranaensis, this new species lived during the Late Cretaceous of Brazil (~90 mya) and was a member of the noasaurid family of theropods, closely related to the weird-jawed Masiakasaurus from Madagascar.

Measuring about 1.5m long (~5′), Vespersaurus was fairly lightly built with legs proportioned for running – and its feet were absolutely unique. Although it had the standard three main toes of a theropod, it bore its weight entirely on the middle toe and held the other digits off the ground. The two raised toes on each foot also had large knife-like claws which may have been used during hunting, vaguely similar to the sickle claws on the feet of dromaeosaurs. But unlike dromaeosaurs these claws weren’t highly curved or pointed, suggesting Vespersaurus used more of a scratching and slashing technique rather than the raptors’ puncture-and-restraint strategy.

Much like ancient horses, it may have developed its single-toed stance as an adaptation for more efficient fast running, possibly to avoid larger predators or to chase down small fast-moving prey like hopping desert mammals.

The known one-toed fossil footprints are actually slightly older than the Vespersaurus fossil, and similar tracks in Argentina have been found dating back to the Late Jurassic (~150mya), so there may have been a long lineage of “one-toed” desert-dwelling noasaurids in South America that haven’t been found yet.

Scutellosaurus

The distinctive armored ankylosaurs and stegosaurs were very closely related to each other, and were part of a group of dinosaurs known as the thyreophorans.

One of the earliest known members of this lineage was Scutellosaurus lawleri. Living in Arizona during the Early Jurassic, about 196-183 million years ago, it was a small lightly-built bipedal herbivore, only about 1.2m long (3′11″) – with over half that length being just its unusually long tail.

Its body was covered in rows of hundreds of small bony osteoderms, helping to protect it against larger predators like Dilophosaurus. And this was obviously an evolutionary strategy that worked very well for Scutellosaurus and other early thyreophorans, because within about 20 million years they’d given rise to the first true ankylosaurs and stegosaurs – with the tank-like ankylosaurs being especially successful, spreading to every continent and lasting all the way up until the end-Cretaceous mass extinction.

Buteogallus daggetti

This leggy bird is known as Daggett’s eagle (Buteogallus daggetti), a bird of prey from the Late Pleistocene of southwest North America.

Living between about 2.5 million and 13,000 years ago, it would have stood around 80cm tall (2′7″), with a wingspan of almost 2m (6′6″) and a fairly hefty body weight of 3kg (6.6lbs). Its feet had less grasping ability than other eagles but it also had particularly strong leg muscles, suggesting it was much better adapted for walking around on the ground.

With its large size, long legs, and terrestrial habits it seems to have convergently evolved to fill the same ecological niche as the modern secretarybird – a grassland-dwelling walking predator that hunted on foot, kicking and stomping small prey animals like snakes, lizards, and rodents.

Voay

Did you know some crocodiles have “horns”?

Formed from the corners of the squamosal bone at the back of their skulls, just above their ears, these structures are seen in living crocs like the Cuban crocodile and the Siamese crocodile, as well as some fossil species.

But perhaps the most impressively-horned croc was Voay robustus here.

Voay lived on the island of Madagascar during the Late Pleistocene and Holocene, between about 100,000 and 2,000 years ago. At about 5m long (16′5″) it was similar in size and build to a large male Nile crocodile – but despite this resemblance its closest living relative is actually the much smaller dwarf crocodile.

It had a fairly short and deep snout and chunky limbs, adaptations associated with a more terrestrial lifestyle that suggest it was specialized for hunting its prey on land rather than just at the water’s edge.

Much like modern horned crocodiles its particularly prominent horns were probably used for territorial displays, and may have been a sexually dimorphic feature with big mature males having the largest examples.

Voay’s disappearance just a couple of thousand years ago may have been the result of the arrival of human settlers on the island, either from being directly hunted or due to the large native species it preyed on also going extinct around the same time.