Tag: odontoanserae

Brontornis

Brontornis burmeisteri was one of the largest flightless birds known to have ever existed, standing around 2.8m tall (9’2″) and estimated to have weighed 400kg (~880lbs).

Known from the early and mid-Miocene of Argentina, between about 17 and 11 million years ago, it’s traditionally considered to be one of the carnivorous terror birds that dominated predatory roles in South American ecosystems during the long Cenozoic isolation of the continent.

But Brontornis might not actually have been a terror bird at all – it may have instead been a giant cousin of ducks and geese.

The known fossil material is fragmentary enough that it’s still hard to tell for certain, but there’s some evidence that links it to the gastornithiformes, a group of huge herbivorous birds related to modern waterfowl.

If it was a gastornithiform, that would mean it represents a previously completely unknown lineage of South American giant flightless galloanserans. And, along with the gastornithids and the mihirungs, it would represent a third time that group of birds convergently evolved this sort of body plan and ecological role on entirely different continents during the Cenozoic.

Weird Heads Month #29: Giant Saw-Toothed Birds

The pelagornithids, or “pseudotooth birds”, were a group of large seabirds that were found around the world for almost the entire Cenozoic, existing for at least 60 million years and only going completely extinct just 2.5 million years ago.

Their evolutionary relationships are uncertain and in the past they’ve been considered as relatives of pelicaniformes, albatrosses and petrels, or storks, but more recently they’ve been proposed to have been closer related to ducks and geese instead.

Whatever they were, they were some of the largest birds to ever fly, and many of the “smaller” species still had wingspans comparable to the largest modern flying birds.

But their most notable feature was their beaks. Although at first glance they look like they were lined with pointy teeth, these structures were actually outgrowths of their jaw bones covered with keratinous beak tissue. While these bony spikes would have been useful for holding onto slippery aquatic animals like fish and squid, they were actually hollow and relatively fragile so pelagornithids must have mainly caught smaller prey that couldn’t thrash around hard enough to break anything.

The serrations also only developed towards full maturity, and the “toothless” juveniles may have had a completely different ecology to adults.

Pelagornis chilensis here was one of the larger species of pelagornithid, with a wingspan of 5-6m (16’4″-19’8″), known from the western and northern coasts of South America during the late Miocene about 11-5 million years ago.

Like other pelagornithids it was highly adapted for albatross-like dynamic soaring, with long narrow wings that allowed it to travel huge distances while expending very little energy – but with its proportionally short legs it would have been clumsy on the ground and probably spent the vast majority of its life on the wing, only returning to land to breed.

Almost-Living Fossils Month #26 – Angry Land-Flamingo-Ducks

The presbyornithids were an early group of waterfowl birds – relatives of modern ducks, geese, swans, and screamers – that first appeared in the Late Cretaceous, about 71 million years ago. With their long necks, long legs, and duck-like bills adapted for filter-feeding, they seem to have essentially been primitive ducks converging on the body shape and lifestyle of flamingos – and as a result they’re sometimes even nicknamed “flamingo ducks”.

They lived in shallow freshwater environments all around the world, and after surviving through the end-Cretaceous extinction they even became some of the most common waterbirds in the early Cenozoic. Some species have been found in large bonebeds containing fossils from thousands of individuals all in one place, suggesting they were very social and lived in huge flocks.

Around the mid-to-late Eocene (~40-37 mya) they seemed to disappear completely, until some fossils from Australia that were originally thought to be from a species of ancient stone-curlew were reassessed in 2016 and found to actually represent the latest-surviving members of the presbyornithids.

Named Wilaru, this bird lived in South Australia during the Late Oligocene and Early Miocene (~28-20 mya). Two different species have been identified: Wilaru tedfordi and its slightly larger and stockier descendant Wilaru prideauxi. With only partial pieces of their skeletons known it’s difficult to estimate their full life size, but based on similar presbyornithids they were probably both somewhere around 1m tall (3′3″).

As well as outliving the rest of their kind, the two Wilaru species were also rather weird compared to the other known flamingo-ducks, with adaptations that indicate they were spending much more time walking around on land than wading in water. Their feet resembled those of modern screamers (which are also more terrestrial) and may have partially or fully lost their webbing, and since they lived alongside various other species of waterfowl and early flamingos they clearly weren’t competing for the same ecological niches. It’s possible they might have also shifted away from their ancestral filter-feeding diet, perhaps becoming more herbivorous, but without any preserved skulls we can’t tell for certain.

Unlike other presbyornithids they also had large spurs on their wings – and based on the behavior of modern spurred waterfowl this suggests they were much less social. They were probably rather aggressive animals, living solitary or in pairs and fighting each other over mates and territory.

This major departure from the lifestyle of their ancestors may have been what allowed Wilaru to survive for so much longer than all the other presbyornithids. They might potentially have lasted a few more million years into the mid-Miocene, but a cooling and drying climate – especially a sudden temperature drop about 14 million years ago – may ultimately have altered their habitat and food sources too quickly for them cope with.

Turtle-jawed moa-nalo

The turtle-jawed moa-nalo (Chelychelynechen quassus) was a large flightless goose-like duck from the Hawaiian island of Kaua‘i. About 90cm tall (3′) and weighing around 7kg (15lbs), these birds and their relatives were descended from dabbling ducks and existed on most of the larger Hawaiian islands for the last 3 million years or so – before going extinct around 1000 years ago following the arrival of Polynesian settlers.

Chelychelynechen had an unusually-shaped bill, tall and broad with vertically-oriented nostrils, convergently similar to the beak of a turtle. It would have occupied the same sort of ecological niche as giant tortoises on other islands, filling the role of large herbivore in the absence of mammals.