Dinosaur survivors in Australia
"...maybe an alternate geology where dwarf dinosaurs survive on an island not far north of Antarctica?"
I've been thinking about what it would take to get some dino survival (after having watched the entire "When Dinosaurs Ruled"
series on TLC this last week).
First of all, forget big sauropods, carnosaurs, or hadrosaurs. Ceratopsians are right out. In fact, forget anything larger than about 150-200 pounds, max. The effects of the impact at Chicxulub made it almost given that if you were big, you - in some way - starved to death before it was all over (assuming you survived the impact in the first place, of course). In fact, 200 pounds is probably stretching it: I'd expect survival more in the 20-50 pound range, at best - which seems to be a limited number of dinosaur types.
Forget plant eaters. Even the small ones are going to have it rough finding food what with the mix of impact fires, acid rain, six months of darkness, a major
"cold snap" followed by a major heat
wave. You'll want something that can survive on what's around for the next couple of years - which will be dead bodies, bugs, and even smaller animals that live off the first two (read: lizards and mammals).
You can begin to understand why birds
survived, but not their larger cousins.
Thirdly, we'll want our dinos as far
away from Chicxulub as we can get them. Given the location of the continents at the time, this would be somewhere in Antarctica/Australia or India. Islands are right out, as there will be worldwide tsunamis pretty much flooding most of those.
So what have we got. We've got the possibility of a few small species, dog-size and under, surviving the K/T event in Australia and/or Antarctica (I think
there's still a connection between the two 65 mybp) and maybe India. India's probably a loss, though, just too much competition from all the other Eurasian animals.
(Farther from there and closer to Chicxulub, you get the survival of similar, but even smaller species. Almost certainly, OTL, all those niches were taken up by birds - we'll assume it holds true on this ATL too)
In fact, it's possible that there was
some localized survival of small dinos of this type on OTL
- the birds did it after all - and that they were later (within a million or so years) replaced by mammals/birds/reptiles, leaving little palentological trace. Individual species of dinosaurs had gone extinct all the time - it's just this time, they'd be the last.
But on this ATL the dice fall the other way.
Let's call our primary species here a survivaraptor. It's a small coelurosaur-like dinosaur, about fifteen to twenty-five pounds in weight. It's primarily carnivorous, but sees nothing wrong with the occasional egg, cockroach, or rotting lizard. When pushed, it'll even eat fruits, but it's not really adapted to this very well.
Our POD here is a mother survivarapter winning its tug of war with the a bird over a "possum," rather than losing as on OTL. It goes on to feed its current nestlings and have lots more before the crocodile gets it a few year later.
Her children, however, live up to their name "survivaraptors" and do just that: Survive.
And as the millennium role by, they begin to radiate into new niches and grow larger, just like their 200 my distant ancestors did. By 55 mybp, they've developed into a number of medium to large bipedal carnivores in Australia, much like birds did in the Americas. In fact, except for the teeth and arms, they probably look
much like the "Terror Birds"
of the Americas. There are also a larger number of small to medium omnivores roaming the pre-Outback.
Ten million years after that, and we get the development of some cow-sized herbivores, which eventually push what would have been the larger kangaroos out of the picture.
Over the next 45 million years till the present, they expand into most niches on the continent. Mammals are once again relegated to their smaller roles. Flight, however, remains a providence of birds and (somewhat later) bats, though a few gliding species of "Australiosaurs" develop. Crocodilians - and later cetacea and seals - prevent any real push towards aquatic living except for one small diving insectivore that pushes the last of the monotremes to extinction.
Australia went through a prolonged period with mostly rain-forest – little open country and, of course, the biped dinosaurs look like they were built for speed, which probably means open country. But I'm not sure that would be a huge problem, long term. I strongly suspect that built for “open country” is more a matter of size and speed than any specific number of legs. And even then, it's more having size and
speed – in a forest, you can be big, or you can be fast, it doesn't look like you can be both.
So as forests wax in Australia, we see a shift into small (less than one-hundred pounds) fast bipeds and the larger, heavier – and a lot slower – big bipeds, end up more like a “therizinosaur” than a “velociraptor.”
And as the trees wane, we may see the return of the big fast bipedal carnivores. Or not. Monitors – to use one suggestion, might totally lock up the “big carnivore” niche – at least, as long as there's still enough big herbivores to eat.
Note that I strongly suspect none
of these new species will be anywhere near
the big dinos of the past – it's still Australia after all, and I'd be
very surprised to see any herbivores get much above a ton or any carnivores above two-hundred-and-fifty pounds.
And when man arrives in Australia, he finds a world of where the medium to large animals are dinosaurs, rather than weird pouched-mammals. Oh, they'll only resemble pre-K-T dinosaurs in the same way that modern mammals resemble, say, those in the Eocene.
But they'll be dinosaurs.
And there will be a die-off when humans arrive, 50K years ago, of course.
Flash-forward to the Eighteenth Century and most of what large and medium species (call it twenty to five-hundred pounds) European
explorers will see in Australia will be dinosaurs. There may not be as many species as the marsupials they replaced, if only because they probably won't spread out into as many niches as mammals did (their bird relatives will suck up all the small-body niches, and probably most of the tree-dwelling ones. And there will still be small marsupials competing), but those that they fill will spread as far as they can and be present in fairly large numbers (rather like American Bison did after most of their Pleistocene competitors went extinct)...at least until they start importing sheep.
But what this timeline's Europeans going to consider them to be – especially since they’re going to see them probably well before
anyone really starts digging up dinosaurs fossils?
Given all the new information we’ve been getting about dinosaurs – and especially raptors – lately, it seems likely that our initial “surviaraptor” is going to look to the “uninitiated” like a funny bird. Oh, it’s a funny bird with hands
and it’s got teeth instead of a beak (though it may well have a partial beak too), and while the tail’s all covered with feathers, it’s still a tail...
but essentially to a generation not
raised on dinosaur discoveries, it’s going to look pretty much like a largish ground bird.
And that’s just the initial species, who knows what’ll evolve from it!
There’s a very good chance all the descendants will be bipedal and feathered. Partial – or even the occasional full – beaks will be the rule too. If some of the carnivores try to recreated the tyrannosaur route, they may well end up with no more arms than the “terror birds” I compared them to above, though I suspect most species will hang onto their arms. It’s just vaguely possible some might try to go the quadruped route again if they get big enough...but I can’t really see anything getting that big on Australia in that “short” a time.
So it’s now the late 18th
century and ur-Cook’s just made his landfall on this dino-Australia. Any biologist at the time is going to look at live examples of the big animals there – and the less-live specimens the hunters bring in – see feathers, see bipedalism, see warm-bloodedness, maybe even see the eggs or nesting females and they are going to put a big check mark in the “Bird” column of the species description. They’ll be uncomfortable with this – for all the “funny birds” reasons listed above – but it obviously isn’t a reptile, even more
obviously isn’t a mammal and – really – in the end, they’re a lot less a “funny bird” than OTL’s platypus is a “funny mammal...”
The arguments will keep going on for decades, but it’s almost a given that the Australian animals are going to get listed as “birds” in all the best biology manuals within the first decade or two of their discovery. And it’s at about that time that the first big dinosaur fossils start getting dug up (or at least, start getting dug up by people who don’t think they’d make just peachy wall-building material).
Most of the initial finds were bipedal and paleontologists, looking for something to compare them to, are probably not
going to go down the “big lizard” path, because they’ll have a modern animal to compare them to sitting right next to them in their cabinet.
So dinosaurs – at least the theropods
(it’ll take a while before the relationship between them and the saurischian
dinos is cleared up) – get listed as an order(s) under the class Aves
. When Archaeopteryx
comes along, it’ll not be seen so much as a link between reptiles and birds, but as confirmation of the Aves
status of dinosaurs (both living and extinct), with Archaeopteryx
as a link between the “Ground Birds” and the “Sky Birds” (in, of course, whatever mock-Latin/Greek names those translate to).
This actually results in a lot more accurate picture than the one we’re more or less moving out of now – though there’ll be blind alleys when biologists try to show ostriches, moas, kiwis, penguins, etc are direct descendants of “Ground Birds” rather than “Sky Birds” that have resumed that mode of living. But on the whole, biology will be a lot more advanced.