No Triassic-Jurassic mass extinction event: No Dinosaur dominance?

The Professor

The Professor

Very interesting.
A minor nitpick - I think you meant "the Archosaurs whose descendants were the Dinosaurs" - Ancestors being back in time ie grandparents etc, descendants being forward ie grandchildren etc.

I think we may still get some birds of some description - afterall the presence of birds did not preclude the evolution of bats, ditto pterosaurs and avians - however they'd have more restricted niches wrt OTL.

On regards ASB or not. These types of thread are generally considered ASB only if the cause of the POD appears ASB or if too much parallel evolution occurs ie in extremis you end with humans riding ceratopsians
 

Archon of Thessaly

The Professor said:
Very interesting.
A minor nitpick - I think you meant "the Archosaurs whose descendants were the Dinosaurs" - Ancestors being back in time ie grandparents etc, descendants being forward ie grandchildren etc.

I think we may still get some birds of some description - afterall the presence of birds did not preclude the evolution of bats, ditto pterosaurs and avians - however they'd have more restricted niches wrt OTL.

On regards ASB or not. These types of thread are generally considered ASB only if the cause of the POD appears ASB or if too much parallel evolution occurs ie in extremis you end with humans riding ceratopsians
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Yep, thanks for that nitpick, i don't really pay attention to grammar or word order when i'm typing.

Secondly, yes i agree that pterosaurs would evolve as OTL, since they were already pretty diverse at the time of the TJ extinction. However, i disagree on birds. Lets look at it like this; their is now less niches for the small theropods to occupy. How could they evolve? My guess is that they would become tree dwelling and eventually become birds earlier then OTL. After all, animals will always occupy any niche available when facing more competition.

When thing i would also ask about is ocean going reptiles: how would they be changed? Would the giant Ichthyosaurs continue to thrive?
 

Archon of Thessaly

yourworstnightmare said:
Biology is different, it has to do with living creatures. People who didn't domesticate animals OTL could well have done it ATL. Evolution could have gone differently if one species survived an extinction event, or if one species had spread to a certain place and thus been able to adopt a certain niche before another species is able to do the same. Climate, Continental Drifts, Volcanic Activity etc. are things a living creature can't affect.
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But wait a moment....... wouldn't the changes needed to make certain animals more domestic able or give Australia agricultural plants completely beyond the control of man and linked to geology? Surely that would make them ASB.......
 

ArKhan

The smallest change in Biology would make all the difference. If the KT extinction still happens, I see mammals, therapsids, dinosaurs, pterosuars, and other Archosaurs, but no birds competeing, and only the smallest surviving the intital impact only to grow larger over millions of years as in OTL. If both extinctions are averted, I see large Therapsids, Mammals, Dinosaurs, Pterosaurs, Crocodilians, and other Archosaurs continuing to evolve along the lines they did in the Jurassic and Cretaceous, whatever those lines maybe. It maybe that the Climate of the Jurassic favors creatures evolving along similar lines as in OTL's Jurassic, and likewise the Cretaceous, and since large creatures evolved in OTL under similar conditions, SOMETHING's gonna get bigger in TTL's Jurassic and Cretaceous. Whether it will be as competely dominated by the Dinosaurs as in OTL is unlikly however with existing taxons out competing each other for the same resourses.We might see one group dominate, or we might see the groups balancing out in some manner, with all the megafuana niches being split between the six groups (agian, Large Therapsids, including mammals, Dinosaurs, Pterosaurs, Crocodillians, and other Archosaurs) all growing to Dinosaur size, and without a KT extinction, continuing uptil the paleogene. If the iceages and thermal maxiums happen as OTL, you can see a world favoring warm blooded, so mammals, possibly therapsids, and possibly dinosaurs and other archosaurs. As for plants, this POD may butterfly away grasses and flowering plants, in which case you'd see old school Triassic plantlife continue to dominate the landscape. I very much doubt humans as we know them could evolve in any of these timelines though, because they all significantly impact mammal evolution. However if a bipedal intelligent animal does evolve it's about as likly as to be a Theropod Dinosaur as a Mammal of somekind.
 
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yourworstnightmare

Banned
Donor
Archon of Thessaly said:
But wait a moment....... wouldn't the changes needed to make certain animals more domestic able or give Australia agricultural plants completely beyond the control of man and linked to geology? Surely that would make them ASB.......
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Evolution is an iffy thing, it still has to do with living creatures, just not man. Still, I'd demand a damn good non ASB explanation to why these animals have evolved to become domesticable to accept it.
 

ArKhan

So if a bipedal humanoid mammal evolved from some kind of mammal in a sceanario where niether the TJ nor the KT extinctions happened, how many mammals, therapsids, dinosaurs or other archosaurs could they potentally domesticate.
 
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Snowstalker

Doubt it. Dinosaurs were already clearly on the rise before the extinction event due to superior build and metabolism; that just sped it up.
 

ArKhan

Snowstalker said:
Doubt it. Dinosaurs were already clearly on the rise before the extinction event due to superior build and metabolism; that just sped it up.
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That is true. However, I can see them spliting the megafuanal niches with Therapsids and other Archosaurs. That seems more likely than them simply completly taking over as in OTL.
 

Imladrik

ArKhan said:
An object in motion stays in motion unless acted upon by an outside force. For an asteroid to change it's course it would need to be pulled by the gravity of another body.
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Actually as we understand it, asteroid trajectories are pretty chaotic (that why with every asteroid close encounter you have a probability of encounter (mainly because we can't calculate every force on the asteroid, especially the small ones), but I think a case could be made about asteroid near miss hitting the Earth or asteroid hitting the Earth missing. Or the asteroid breaking into smaller parts due to tidal forces near the earth and having several small asteroid impacts instead of a big one. For asteroids i don't think it is as ASB as for volcanoes eruptions for example.
 

ArKhan

I have to say that the Triassic is, by far my favorite geologic era. In many ways it is to vertibrate megafuana what the ultimate showdown of ultimate destiny is to fictional characters. Creatures with the Heamatotheria "package" of traits (four chamber heart, semi-erect or fully erect hip postures, brains with cerebral cortexes, and advanced child rearing behavior, all traits found in the Heamatotherian animals, which include archosaurs, therapsids, and their decendents such as crocodillians, dinosaurs, birds, and mammals, but not in any other amniote animals) Have dominated land virtutally non-stop since the Permian era, however, it was only in the Triassic that ALL the clades of Heamatotheria (with the expection of birds, depending on if you count their dinosaur ancestors) ever to "rule" in any geologic era co-existed in the same place at the same time. We have the last Therapsids left over from the Permian, we have the first dinosaurs that wouldn't take over completly until the Jurassic, and the first mammals that wouldn't take over until the KT extinction. We also have a large number of novel archosaur clades that died out in the TJ extinction. Not to mention the first pterosaurs and crocodillians. Durring the Triassic it's obvious that the closely related Heamatotheria clades would continue to dominate land until this day, and the fact that all these clades are closely related, something that wouldn't be as obvious in later eras, was much more obvious in the Triassic. The great thing about Triassic PODs is that evolution really could have gone anyway. Therapsids? Mammals? Dinosaurs? Some other group of Archosaurs? All of the Heamatotheria clades had the potental to produce megafaunal greatness as we know from the fossil record. The strange thing is that in OTL only one group of animals, namely the dinosaurs was able to take over in the Jurassic. But if the TJ extinction is averted, things are a lot more even for the Heamatotheria. If all the Heamatotheria clades survived into to modern day, then OTL's classifications of "bird" "reptile" and "mammal" become non-sense, as it would be rather difficult to say where one ends, and another begins.
 
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The Professor

The Professor

ArKhan said:
Most likly egg laying monotremes. Placental and Marsupial mammals didn't evolve until later in the Mesozoic. That might still happen, or it might be butterflied away,
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ArKhan said:
I have to say that the Triassic is, by far my favorite geologic era. In many ways it is to vertibrate megafuana what the ultimate showdown of ultimate destiny is to fictional characters. Creatures with the Heamatotheria "package" of traits (four chamber heart, semi-erect or fully erect hip postures, brains with cerebral cortexes, and advanced child rearing behavior, all traits found in the Heamatotherian animals, which include archosaurs, therapsids, and their decendents such as crocodillians, dinosaurs, birds, and mammals, but not in any other amniote animals) Have dominated land virtutally non-stop since the Permian era, however, it was only in the Triassic that ALL the clades of Heamatotheria (with the expection of birds, depending on if you count their dinosaur ancestors) ever to "rule" in any geologic era co-existed in the same place at the same time. We have the last Therapsids left over from the Permian, we have the first dinosaurs that wouldn't take over completly until the Jurassic, and the first mammals that wouldn't take over until the KT extinction. We also have a large number of novel archosaur clades that died out in the TJ extinction. Not to mention the first pterosaurs and crocodillians. Durring the Triassic it's obvious that the closely related Heamatotheria clades would continue to dominate land until this day, and the fact that all these clades are closely related, something that wouldn't be as obvious in later eras, was much more obvious in the Triassic. The great thing about Triassic PODs is that evolution really could have gone anyway. Therapsids? Mammals? Dinosaurs? Some other group of Archosaurs? All of the Heamatotheria clades had the potental to produce megafaunal greatness as we know from the fossil record. The strange thing is that in OTL only one group of animals, namely the dinosaurs was able to take over in the Jurassic. But if the TJ extinction is averted, things are a lot more even for the Heamatotheria. If all the Heamatotheria clades survived into to modern day, then OTL's classifications of "bird" "reptile" and "mammal" become non-sense, as it would be rather difficult to say where one ends, and another begins.
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Indeed. Especially if we add in vivipary/viviparity (the bearing of live young as opposed to eggs)
 

Staten-John

Greetings....first post.
All the comments that have been posted indicate that you all are very knowledgeable about the Triassic-Jurassic extinction. I would like to make you aware of a theory that is able to explain this extinction and all other mass extinctions because the theory attributes the initial cause to be the same. And, as unbelievable as it might seem at first glance, there is ample evidence to support the theory. A summary of The Gravity Theory of Mass Extinction can be found at:

http://www.dinoextinct.com/page13.pdf

Regarding the T-J extinction, this theory (the GTME), has the following explanation:
After the P-T extinction, as Pangea’s center of mass moved well north of the equator, surface gravity gradually lowered (see pdf above for explanation of conservation of angular momentum). This lowering of surface gravity allowed all fauna to increase in size until Pangea reached its highest latitude about 201mya when it reversed direction and started moving south, initiating a rapid pulse of increasing surface gravity.

All lifeforms, both terrestrial and marine, were affected by this. On land, the massive crurotarsi went extinct because their splayed leg structure would no longer support them, opening the door for dinosaur gigantism. The same is true of the large amphibians. In the sea, any lifeform, large or small, that was calcium-heavy, such as conodonts, suffered.

GTME also explains why massive flood basalt volcanism, the CAMP in this instance, always follows the initial extinction phase of all mass extinctions.

Methane from the sea bottom was released because the sudden massive sea level drop (which is explained by the theory) coupled with the higher pulse of surface gravity (but still relatively low compared to today) resulted in very low water pressure on the sea bottom. The combination of generally warm ambient temperature, which increased after the CAMP eruptions, the lowered sea level and relatively low surface gravity provided the two conditions needed for the release of the methane, i.e., warm sea temperatures and low pressure.
 

Archon of Thessaly

Staten-John said:
Greetings....first post.
All the comments that have been posted indicate that you all are very knowledgeable about the Triassic-Jurassic extinction. I would like to make you aware of a theory that is able to explain this extinction and all other mass extinctions because the theory attributes the initial cause to be the same. And, as unbelievable as it might seem at first glance, there is ample evidence to support the theory. A summary of The Gravity Theory of Mass Extinction can be found at:

http://www.dinoextinct.com/page13.pdf

Regarding the T-J extinction, this theory (the GTME), has the following explanation:
After the P-T extinction, as Pangea’s center of mass moved well north of the equator, surface gravity gradually lowered (see pdf above for explanation of conservation of angular momentum). This lowering of surface gravity allowed all fauna to increase in size until Pangea reached its highest latitude about 201mya when it reversed direction and started moving south, initiating a rapid pulse of increasing surface gravity.

All lifeforms, both terrestrial and marine, were affected by this. On land, the massive crurotarsi went extinct because their splayed leg structure would no longer support them, opening the door for dinosaur gigantism. The same is true of the large amphibians. In the sea, any lifeform, large or small, that was calcium-heavy, such as conodonts, suffered.

GTME also explains why massive flood basalt volcanism, the CAMP in this instance, always follows the initial extinction phase of all mass extinctions.

Methane from the sea bottom was released because the sudden massive sea level drop (which is explained by the theory) coupled with the higher pulse of surface gravity (but still relatively low compared to today) resulted in very low water pressure on the sea bottom. The combination of generally warm ambient temperature, which increased after the CAMP eruptions, the lowered sea level and relatively low surface gravity provided the two conditions needed for the release of the methane, i.e., warm sea temperatures and low pressure.
Click to expand...

An interesting theory-it does offer a plausible explanation for the rise in ethane/ CO2 levels at the end of this period from the Atlantic basalt that caused the catastrophic climate change.

Just a few things though: firstly, how does it explain the Cambrian and Devonian mass extinctions, that have often been attributed to gamma rays radiation, Bolide impacts caused by a meteorite strike, the evolution of plants which pumped the rivers with high levels of nutrients ( hence the high levels of anoxia which may have smothered fish and sea life.

Another thing to consider is that this mass extinction happened fast-could GTME really cause such a major change in climate so quickly?
 

Staten-John

GTME posits that every mass extinction is accompanied by at least one massive drop in sea level which, by geologic timescale, is rapid. This happened, perhaps several times during the Devonian Period.

From Wikipedia,
"Leading theories include changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism."

"There is good evidence for high-frequency sea level changes around the Frasnian/Famennian Kellwasser event, with one sea level rise associated with the onset of anoxic deposits. The Hangenberg event has been associated with sea-level rise followed swiftly by glaciation-related sea-level fall."

Wikipedia suggests glacioeustasy as the cause of the drop in sea level, but they might be mistaken. I assume they attribute the sea-level rise to glacioeustasy also but can that account for the magnitude of the sea-level changes? GTME explains the transgressive-regressive couplets as being caused by the lowering/increasing of surface gravity caused by the core movements which are linked to the latitudinal movement of continental mass.

The following link addresses the continental movement during the Devonian, which is complex because their were collisions, rotations and latitudinal movements.
http://www.geologyclass.org/cambrian_concepts2.htm

The severest extinction was in the tropics. With core movement away from the hemisphere with the continental land masses, within the equatorial plane, the greatest increase in surface gravity (according to the GTME) would be in the equatorial region of the land masses.

The armored fish, the Placodermi, originated in the Devonian and went extinct by the end of that period. These massive fish would be expected to suffer if surface gravity increased.
　
 

Forbiddenparadise64

Sorry to bump this, but I just wanted to add some detail to this.

  • At the time of the T-J extinction, the fauna was a mix, while it was mostly dinosaur afterward. Without the extinction, niches are going to be much more varied.
  • Research seems to suggest dinosaur dominance wasn't guaranteed- crurotarsans (inc aetosaurs, rynchocephalans, plus various others) were evolving at the same rate as the dinosaurs, and with much more variation in forms. The extinction changed this, so these groups would still be around.
  • Conodonts continue in the oceans
  • continuations on phytosaurs, placoderms,
  • Synapsids will still be around in various forms, though their forms will be significantly change in response to competition.
  • Due to different evolutionary paths and competitors, birds are butterflied, and most mammal groups too (though different ones will appear).
  • Overall, fauna will be much more varied in forms, and dinosaurs will be one group among many.

There are projects on the web that discuss pods like this, so look at some of them for advice.
 

edvardas

Speaking of the ocean, the straight-shelled nautiloids went extinct after 20o million years. If michelinoceras were still around, it would be cool
 
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