I'm reading this fascinating book, Out of Thin Air by Peter Ward.
Up to and including the Permian period, life on Earth was proceeding steadily toward life as we know it today, including proto mammals and proto dinosaur / birds. But then in 251m BC oxygen levels fell through the floor, nearly wiping out all life. Oxygen levels didn't get back even to 20% until near the close of the Cretaceous (70m). This era between the old and the new forms of life is called "middle-life", Mesozoic.
The Triassic 251m-199m is a "lost period" in palaeontology. The Jurassic and Cretaceous periods 199m-65m are the focus of Ward's book.
Ward wonders why this period post-Triassic didn't just pick up after the Permian left off, with mammals. Mammals "won" in the end, and they were around in the Triassic, so why didn't they win at the beginning? Instead there is a "wrong turn" in life, lasting ~135 million years. This is the Dinosaur Age, fascinating to our six year olds and the basis for "alternate Earth" scenarioes in which the ornithosaurs, rather than the primates, begat intelligent life.
The reason I'm rambling about all this is because one of these scenarioes is in Beyond Countless Doorways: the Lizard Kingdoms.
The 19th century palaeontologists called their fossils "terrible lizards (deinoi sauroi)" but they really weren't lizards at all. Dinosaurs were more like birds. True reptiles don't have the heat-exchange or respiratory systems capable of supporting nervous systems much more complex than those of iguanas and crocodiles. And, except for spurts of energy, reptiles are sluggish. Dinosaurs are a more realistic prospect for a "lizard kingdom" civilisation. Besides "lizard kingdom" is certainly a name foisted upon the region by mammalian outsiders. The natives would retort that we were the "rodent kingdom".
Ward thinks that the birds', and by extension dinosaurs', evolutionary advantage over mammals during the Mesozoic was that they have an efficient respiratory system.
So, we could add a little more "kick" to that setting if we set the surface oxygen level to 15%. Sentient mammals there will be short and barrel-chested, like Andean natives, except that they won't venture up the mountains at all. Player characters who aren't adapted for hypoxic climes are going to have problems with "altitude sickness".
Ward predicts that mountainous barriers would be more effective at barring movement from one place to another at 15% oxygen than they are at 21%; he also predicts divergent evolution from one region to the next. This helps explain the plane's species diversity (better than most D&D settings can explain theirs). It also explains why Ancient Underhill is considered a "common conjunction plane". Stocneau likely also has low oxygen pockets in it, about what we can expect from a fire plane.
Low oxygen also helps explain why the Lizard Kingdoms's plane hasn't been invaded by cross-planar forces, e.g. from the Round Road or Ethereal Sea. No-one wants to move here! Although, this could change, if a mountain plane ruled by Pachacuti Inca were to come into conjunction with it.
[Oh, and insect kingdoms like Dendri will be high oxygen, 40% perhaps. But as they say, that is Another Rant...]
Up to and including the Permian period, life on Earth was proceeding steadily toward life as we know it today, including proto mammals and proto dinosaur / birds. But then in 251m BC oxygen levels fell through the floor, nearly wiping out all life. Oxygen levels didn't get back even to 20% until near the close of the Cretaceous (70m). This era between the old and the new forms of life is called "middle-life", Mesozoic.
The Triassic 251m-199m is a "lost period" in palaeontology. The Jurassic and Cretaceous periods 199m-65m are the focus of Ward's book.
Ward wonders why this period post-Triassic didn't just pick up after the Permian left off, with mammals. Mammals "won" in the end, and they were around in the Triassic, so why didn't they win at the beginning? Instead there is a "wrong turn" in life, lasting ~135 million years. This is the Dinosaur Age, fascinating to our six year olds and the basis for "alternate Earth" scenarioes in which the ornithosaurs, rather than the primates, begat intelligent life.
The reason I'm rambling about all this is because one of these scenarioes is in Beyond Countless Doorways: the Lizard Kingdoms.
The 19th century palaeontologists called their fossils "terrible lizards (deinoi sauroi)" but they really weren't lizards at all. Dinosaurs were more like birds. True reptiles don't have the heat-exchange or respiratory systems capable of supporting nervous systems much more complex than those of iguanas and crocodiles. And, except for spurts of energy, reptiles are sluggish. Dinosaurs are a more realistic prospect for a "lizard kingdom" civilisation. Besides "lizard kingdom" is certainly a name foisted upon the region by mammalian outsiders. The natives would retort that we were the "rodent kingdom".
Ward thinks that the birds', and by extension dinosaurs', evolutionary advantage over mammals during the Mesozoic was that they have an efficient respiratory system.
So, we could add a little more "kick" to that setting if we set the surface oxygen level to 15%. Sentient mammals there will be short and barrel-chested, like Andean natives, except that they won't venture up the mountains at all. Player characters who aren't adapted for hypoxic climes are going to have problems with "altitude sickness".
Ward predicts that mountainous barriers would be more effective at barring movement from one place to another at 15% oxygen than they are at 21%; he also predicts divergent evolution from one region to the next. This helps explain the plane's species diversity (better than most D&D settings can explain theirs). It also explains why Ancient Underhill is considered a "common conjunction plane". Stocneau likely also has low oxygen pockets in it, about what we can expect from a fire plane.
Low oxygen also helps explain why the Lizard Kingdoms's plane hasn't been invaded by cross-planar forces, e.g. from the Round Road or Ethereal Sea. No-one wants to move here! Although, this could change, if a mountain plane ruled by Pachacuti Inca were to come into conjunction with it.
[Oh, and insect kingdoms like Dendri will be high oxygen, 40% perhaps. But as they say, that is Another Rant...]
