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Description

A selection of the basal galloanserae known as gastornithids, to scale.

With the catastrophic event that occurred at the end of the Cretaceous, surviving terrestrial vertebrates were restricted in size to under 25 kilograms (not including the amphibious turtles and crocodylians). This blank slate heralded in the dawn of a new era, the so-called 'Age of the mammals'. However the first steps were hardly thunderous as the earliest mammals barely increased in size from their Mesozoic ancestors. It took until the latter half of the of Palaeocene before large-bodied mammals appeared. Previously it was thought that giant birds dominated ecosystems as the apex predators, in the 'absence' of large mammals. Flightless gastornithids were usually depicted as running down unfortunate mammalian victims, commonly the early horse Eohippus, which were dispatched with a blow from their deadly beak. This horse-killer went by the name Diatryma. For various reasons, this story is a complete fabrication. While some other families of flightless birds were indeed predatory (such as the mostly South American phorusrhacids Birds of Mass Destruction - Phorusrhacids ), the giant birds of the early Cenozoic were less terrifying and very different in behaviour.

Only three genera have been named: the European Gastornis, the Chinese Zhongyuanus, and the aforementioned Diatryma from North America. Differences between the three are minimal and now all are subsumed under the first named Gastornis. Standing as tall as an average male human, there is no doubt that it would have been intimidating bird. A large head on a strong neck with a deep hatchet-shaped beak looks like it could do some serious damage. Yet the edges of this beak were straight lacking a hooked tip, as one would typically see in meat-eating birds. Short lower legs that were not built for sprinting and blunt hoof-like claws complete an unlikely hunter. Deep muscles anchoring the lower jaw were definitely capable of generating a strong bite, but it wasn't for tearing into a carcass. The beak was built to crack tough seeds and hard fruits, and subsequent calcium isotope studies has proved that that this bird was a herbivore.

They were previously allied to the Gruiformes (cranes and rails) but recent research has shown gastornithids are more closely related to the Australian dromornithids (Demon ducks - Dromornithids ) and both are basal to the waterfowl line (What the duck? - Anatids ). As forests retreated with a cooling climate towards the end of the Eocene, the gastornithids disappeared.

Description

A selection of the basal galloanserae known as gastornithids, to scale.

With the catastrophic event that occurred at the end of the Cretaceous, surviving terrestrial vertebrates were restricted in size to under 25 kilograms (not including the amphibious turtles and crocodylians). This blank slate heralded in the dawn of a new era, the so-called 'Age of the mammals'. However the first steps were hardly thunderous as the earliest mammals barely increased in size from their Mesozoic ancestors. It took until the latter half of the of Palaeocene before large-bodied mammals appeared. Previously it was thought that giant birds dominated ecosystems as the apex predators, in the 'absence' of large mammals. Flightless gastornithids were usually depicted as running down unfortunate mammalian victims, commonly the early horse Eohippus, which were dispatched with a blow from their deadly beak. This horse-killer went by the name Diatryma. For various reasons, this story is a complete fabrication. While some other families of flightless birds were indeed predatory (such as the mostly South American phorusrhacids Birds of Mass Destruction - Phorusrhacids ), the giant birds of the early Cenozoic were less terrifying and very different in behaviour.

Only three genera have been named: the European Gastornis, the Chinese Zhongyuanus, and the aforementioned Diatryma from North America. Differences between the three are minimal and now all are subsumed under the first named Gastornis. Standing as tall as an average male human, there is no doubt that it would have been intimidating bird. A large head on a strong neck with a deep hatchet-shaped beak looks like it could do some serious damage. Yet the edges of this beak were straight lacking a hooked tip, as one would typically see in meat-eating birds. Short lower legs that were not built for sprinting and blunt hoof-like claws complete an unlikely hunter. Deep muscles anchoring the lower jaw were definitely capable of generating a strong bite, but it wasn't for tearing into a carcass. The beak was built to crack tough seeds and hard fruits, and subsequent calcium isotope studies has proved that that this bird was a herbivore.

They were previously allied to the Gruiformes (cranes and rails) but recent research has shown gastornithids are more closely related to the Australian dromornithids (Demon ducks - Dromornithids ) and both are basal to the waterfowl line (What the duck? - Anatids ). As forests retreated with a cooling climate towards the end of the Eocene, the gastornithids disappeared.