Last week I posted about New Zealand being a lost world of dinosaurs – as long as we think of birds as a dinosaur. Which, of course, they are.
This isn’t hyperbole. Today, birds are formally part of the dinosaur clade – the greater family. Specifically, they are avian dinosaurs, whereas the ones that went extinct 65 million years ago were the non-avian version.
This concept has been a long time coming, although it shouldn’t have been. The relationship between birds and dinosaurs began emerging in the nineteenth century, starting with the Jurassic-age fossil of Archaeopteryx dug out of a quarry near Solnhofen in 1860-61. It was a bird with toothed jaws, found to be related to contemporary ground-dwelling maniraptors. Even so, paleontologists usually imagined that birds were a dinosaur side-branch that had gained distinctive characteristics and become a separate creature.
New discoveries during the early twenty-first century revealed a different picture. Some dinosaurs – particularly many of the two-legged carnivorous species – were found to be feathered and, though the jury remains out, there has been speculation that all dinosaur families were feathered in various ways. Not all were ‘flight’ feathers, but some dinosaurs – birds – certainly flew, and they’d been doing it since the Jurassic. In fact there were two dinosaur families that flew – one of which, Enantiornithes, died out during the Cretaceous. What’s more, it seems that as the Cretaceous continued, many bipedal non-flying dinosaurs became increasingly like birds, apart from flight.
Birds, in short, were dinosaurs – specifically, theropods, which weren’t ‘bird hipped’ dinosaurs (‘Orthinischia’), they were ‘lizard hipped’ (‘Saurischia’). Go figure. Birds were also diapsids, like dinosaurs; and shared features we know existed across a wide range of dinosaur species, including nest-building, egg-laying, feathers of various types, beaks, pneumatised bones, and so on. Lest there be any doubt, experiments at the Max Planck institute revealed that chickens have the gene for atavistically growing dinosaur teeth (it’s talpid2, specifically).
From this we can hypothesise that dinosaurs were endothermic, because birds are – chickens, for instance, have a higher body temperature than we do – 41-45 degrees C vs our 37.
To put that in perspective, nineteenth century science classified ectotherms (reptiles and amphibians) as ‘cold blooded’, anthropomorphising the term into human behaviours such as ruthlessness. Actually, ectotherms can’t function when they’re cold – they have to warm up. I know. There was one time I ended up with a 2-metre long snake wrapped around my shoulders, and it was as warm as I was.
The problem for reptiles is they’re reliant on external heat to get to operating temperature. Providing enough food’s around, it’s an evolutionary advantage to generate your own – and birds show that mammals aren’t unique in developing that trait.
So how did flying dinosaurs survive when others didn’t? The Chixuclub impact that devastated Earth’s biosphere some 65 milion years ago didn’t specifically kill dinosaurs – it destroyed an immense range of life, including reptiles, mammals, amphibians, dinosaurs and plants. Vast areas were reduced to grass and fern-land. One issue, it seems, was the damage to the food chain. All the larger creatures – which included many species of dinosaur – died off. Some flying dinosaurs (birds), it’s been speculated, survived because of that ability to fly. Mammals – small rodent-like creatures – survived possibly by virtue of their size.
For me the crucial point is that afterwards, mammals didn’t automatically take over. After the Chixuclub impact, surviving species – dinosaurs (birds), mammals, reptiles and amphibians – re-radiated into empty ecological niches. There was nothing inevitable about mammals becoming dominant. They did so in Africa, North America and Eurasia. But in South America, large dinosaurs re-emerged in the form of flightless carnivorous birds. Other mixes appeared in Australia, where the dominant land animals became one of the variants on the mammal theme – marsupials – alongside dinosaurs (birds) that radiated into various ecological niches alongside the marsupials. Examples included a 2.5-metre tall carnivorous duck, Bullockornis. Yes, folks, a gigantic predatory duck. Don’t laugh.
In my own country, New Zealand, mammals didn’t flourish at all. Here, the reptiles, lizards, dinosaurs and insects that had dominated southern Gondwanaland during the Cretaceous continued – with a few amendments. For reasons associated with erosion and mountain-building, today’s land-mass isn’t what existed then. But in general the biota – isolated from the rest of the world – survived as the land changed around it. Larger dinosaurs were gone; but the New Zealand (‘Rangitata’) archipelago was re-colonised by the flying variety – which lost the ability to fly. And the flora was much as it had been through the dinosaur period.
If we want to speculate on how the world might have looked had the Chixuclub asteroid strike not occurred, New Zealand is probably all we need. Setting aside the absence of larger dinosaur species, it’s arguably where the dino-world would have gone had it lasted into the quaternary era.
Had? Yeah. A lot of that biota has gone. The arrival of humans around 1280 saw to that. New Zealand’s ‘lost world’ of archaic plants, flightless birds, insects and so forth reeled under the impact of humanity. The arrival of British settlers after the 1840s virtually completed the destruction.
New Zealand was – WAS – a true ‘lost world’. Its dinosaur age, basically, ended during the fourteenth century. Today, it’s still there in bits, especially on offshore islands. And in some cities, a bit. As I write this, a tui (Prosthemadera novaeseelandiae) is singing outside my window. A dinosaur? Hell yeah.
Copyright © Matthew Wright 2015