Biology Ancient Australia (Extinct Megafauna, Dinosaurs etc)
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- #127
This fossil is a beauty, a one in a trillion. Look at the soft tissue preservation. Meet Ptychodos, a 75 myo mackerel shark, from the same family that includes the extinct gigantic shark megalodon and our current great white shark.
Note - Other than their teeth, sharks preserve poorly because they have no bones. Often paleos will have millions of shark teeth from an animal and that's all. This is truly remarkable.
www.theguardian.com
‘An enigma’: scientists finally learn what giant prehistoric shark looked like
Full and part skeletons found in Mexico reveal body shape and anatomy of Ptychodus as well as its likely diet
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- #128
I've been watching Peter do this reconstruction of a short faced kangaroo, Simosthenurus occidentalis over the last few months, this is the first time I've seen it placed in a scene. Peter agonised over issues like the dew claw and the shape of the toes, matters which remain uncertain but are resolved by plonking it in a bit of grass.
Paleo's have just released a paper about Simosthenurus occidentalis
www.theguardian.com
I think I have posted about this before, these guys are believed to be walkers rather than hoppers, some have suggested an upright gait like a human, others have suggested a posture more like a bipedal dino. Peter has avoided the issue by posing it in a stationary position.
Added - I remembered I did a 'digital sketch' of it walking in a dino like fashion last year, the neck looks too long. Anyway here it is:
Paleo's have just released a paper about Simosthenurus occidentalis
‘Unlike anything today’: Gippsland fossil unlocks secrets of kangaroo that died out 46,000 years ago
Abrupt extinction of short-faced kangaroo a reminder to protect the environment, palaeontologists say
I think I have posted about this before, these guys are believed to be walkers rather than hoppers, some have suggested an upright gait like a human, others have suggested a posture more like a bipedal dino. Peter has avoided the issue by posing it in a stationary position.
Added - I remembered I did a 'digital sketch' of it walking in a dino like fashion last year, the neck looks too long. Anyway here it is:
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MP_
I am the devil that you forgot
Went to the Adelaide museum today, just seeing the T rex skull cast makes you wonder how crazy the earth was with these magnificent creatures roaming around.
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- #131
Totally irrelevant but very nice reconstruction of a typical Ediacaran 'frondomorph' by my friend Peter Trusler to start the post with, these are sessile animals, not plants. The Ediacaran period (691 to 541-mya) saw the rise of the first complex, active, multicellular organisms. These critters were powered by increasing oxygen levels over the previous billion years. Paleos argue about how much of the progressive rise oygen in the preceeding few billion years was biological and how much was geochemical, probably both. This article proposes a novel mechanism for higher oxygen levels occurring in Ediacaran, the loss of Earth's magnetic field about 591 mya.
Collapse of Earth's magnetic field may have fueled evolution of life 600 million years ago
The planet's magnetic field may have collapsed around 600 million years ago, enabling a major oxygenation event and perhaps supercharging evolution.
The authors propose the loss of the magnetic field led to increased hydrogen leaking from the upper atmosphere resulting in an increase in available oxygen in the atmosphere and the oceans. This is speculative without any actual proof. The graph below shows atmospheric oxygen over the last billion years, you will note oxygen levels rising in the 40 million years before the loss of the magnetic field.
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