Alternate History: How much area do I need for viable dinosaurs to be found thriving in Antarctica

Question

To narrow this down, I'm looking only for climactic specifications. Not cultural responses, etc.

During Ernest Shackleton's expedition to the Antarctic continent, he found a huge canyon/crevasse that spanned a very large area of tectonic activity. In fact, with hot springs, volcanic activity and geysers, it remained a humid subtropical and temperate tropical version of Yellowstone or Gobustan.

This area was protected from climate changes over millions of years and still boasts the remnants of the Cretaceous Period. Due to heat from the planet, it maintains a humid and humid-subtropical climate to have allowed ancient plants and animals to thrive.

In a magnitude of order (no hard science needed), how big should my sheltered canyon or basin be, in order that Mr. Shackleton has stumbled upon dinosaurs and ancient plants, that were able to survive in a 'biome' for 66+ million years?

Post Script: I know this to be impossible; I'm asking only for the physical size, in a magnitude of order, needed to support such a large ecosystem over 66+ million years in an Alternate History story. Are we talking, "The Whole Continent," or can we have a good "Thousand Acres," et. al.

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I don't care if the dinosaurs have evolved a bit. I want Shackleton to have stumbled upon a Cretaceous remnant that includes 'dinosaurs'

Answer 1

There is no chance a reptile will be able to survive the cold of antartica - even in a sheltered valley - without some kind of heat source.

Let us assume that the valley is heated by a series of hot springs which come up and form a river which runs end to end. The heat of these hot springs can be above boiling temperature - which would provide a humid environment that can fill the open-topped valley. To prevent contamination from external organisms, the river runs out to sea via a crevasse and is dug deep into the rock with steep, sheer sides.

Looking at the dinosaur population from the point of view of a food web, your ecosystem will need some manner of food source to maintain it. It's possible that there is some sort of algae or seaweed that has evolved to live off the steam and low-light conditions of the hot springs - and perhaps some plants that were introduced in the dung of migrating dinosaurs.

For large sauropod dinosaurs, I've looked up the home range (where it browses/forages for food) of the giraffe which would have a similar diet and walking speed - and it can reach roughly 160kms (99 miles) or 25600 square km (9801 square miles).

With the assumptions:

• the valley must be narrow enough to contain the steam
• wide enough for any plants that need to photosynthesise to gather light
• wide/complicated enough for herbivores to avoid predators

Your valley could be 3 miles wide and 3267 miles long. (3.737 times the length of the United Kingdom)

Picture for comparison with Australia in there for good measure:

Remember, your valley could be wider and narrower in places, riddled with caves and be a tangled, winding shape as is natural for gullys cut by rivers. If this were the case, it could easily fit within the silhouette of the UK.

In actuality, this would not be such a stretch of the imagination and could, potentially, exist were Antarctica a little closer to the edge of its tectonic plate.

Answer 2

I would proceed like this:

• Figure out what the biggest dinosaur is which you want to be found in this biome.
• Figure out what its Minimum viable population is. (If you don't find values for this by googling it, I'd just take the largest related currently living carnivore/herbivore you can find.)
• Calculate how much area you would need per individual of said race of big dinosaurs. (Again if Google doesn't yield anything I'd look up values for elephants/giraffes/tigers/... and scale them up.)
• MVP times area-per-individual will give you the minimal size of your biome to support a stable long term population of your biggest dinosaur.

You can generally assume that the smaller species will need less area and can thus easily have stable populations within the same area.

Answer 3

I say the size of large city like New York or London . But that just a guess. The are numerous islands small then that and they are self sustaining. Your area would be bigger because of the need to accommodate the dinosaur.