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Crurosauria; No Triassic-Jurassic Extinction
Topic Started: Jul 6 2010, 03:06 PM (3,320 Views)
Vultur-10


Introduction: In this alternate evolutionary history, the Triassic-Jurassic Extinction never happened. In our history, this cleared out a lot of the other archosaurs and some of the synapsids, giving the dinosaurs dominance. In this universe, those groups carried on, and so the ecological niches of large land animals have a much greater taxonomic diversity - dinosaurs, crurotarsans, and even some therapsids and a few other groups. (The name Crurosauria is a compound of Crurotarsa + Dinosauria, the two dominant groups of large land vertebrates.) Mammals exist, and are slightly more diverse and larger than in the real Mesozoic, but still nowhere near dominant. Pterosaurs are present, and fill more or less the same role they did in our Mesozoic, though the species are different. Pterodactyloid pterosaurs never develop, nor do birds.

The time periods are also different; the Triassic carries on till 183 Mya, including most of our Early Jurassic. A significant marine extinction occurs then, but it has little effect on land. The Jurassic runs from 183 Mya to around 110 Mya, when the rapid diversification of calcific ferns transforms the landscape dramatically. The Cretaceous continues until a hammerblow of massive volcanic eruptions circa 80 Ma.
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Carlos
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The original version of Terra Alternativa was sort like this, but I completly changed it.
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

My Patreon:

https://www.patreon.com/Carliro

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ATEK Azul
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I like the sound of this though I am wondering why the Cretacious ends early?

Also will this mean a higher diversity of Synapsids, Archosaurs and Pterosaurs after the Mesozoic?

And if Dinosaurs never take over, does this world have their ancestral forms until present day? And if so what features will they have evolved in convergence and divergence with Dinosaurs and Birds?
I am dyslexic, please ignore the typo's!
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The Dodo
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Different World was also like this.
On the subject of anapsids, they would have greater diversity seeing that Procolophonids wouldn't be extinct.
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ATEK Azul
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Awsome more Anapsids.

So what are you planing on surviving the K-T event?
I am dyslexic, please ignore the typo's!
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Toad of Spades
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If birds never develop and neither do pterodactyloids, does that mean Rhamphorhynchoids take their place? Or do rhamphorhynchoids stay as long lasting basal forms and something else evolve to take the place that would be occupied by pterodactyloids or birds? A flying crurotarsan or bat-like dinosaur would be interesting.

Also with no T-J extinction, do marine groups stay the same?
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The Dodo
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Marine groups would be different, conodonts might still be around since they were finally wiped out in the Triassic mass extinction.
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Vultur-10


JohnFaa
Jul 6 2010, 03:09 PM
The original version of Terra Alternativa was sort like this, but I completly changed it.
What did you do with the flora there?

On our earth, both the Cretaceous appearance of angiosperms and the Cenozoic development of grassland ecosystems changed the landscape pretty dramatically. Obviously Crurosauria will have *different* changes, but I do plan to have the flora changes be major drivers of animal evolution.

GENERAL TIMELINE - FIRST HUNDRED MILLION YEARS
Late Triassic (divergence until 183 Mya): Generally still fairly similar to our world's latest Triassic. Toward the end of this period several new groups which will play a major role in the Jurassic begin to emerge: primarily the longicolloids, polydentoids, and marisaurs. The pilocrocodilia also appear, and enjoy a brief flourishing in the extreme temperatures of interior Pangaea.

Early Jurassic (183 - 156 Mya): Longicolloids become the dominant land animals in marginal environments. Polydentoids and true mammals get off to a slow start, remaining small throughout this time. The pilocrocodilia fall into drastic decline and eventually become extinct as climate becomes moderate and warm, allowing crocodiles to push into their niches.
Marisaurs and ichthyosaurs dominate the seas. Marine turtles appear. At this period's end, an increase in volcanism causes minor extinctions, but more importantly raises the atmospheric CO2 level significantly.

Late Jurassic (156 - 110 Mya): CO2 levels become almost dangerously high, and the world's forests seemingly explode with rampant growth. The vast food supplies and relatively homogeneous environments allow for vast herbivores; the longicolloids grow to staggering sizes, as, in the seas, do the placodonts, till now an obscure and minor group, which develop massive filter-feeding forms including Aquatitan ingentios, the largest animal ever. Ichthyosaurs begin a slow decline as marisaurs develop swifter forms. This competition worsens as swifter sharks appear. Calcific ferns appear, and in the last five million years of this period, massive radiation of this group transforms the landscape drastically.

---

Will focus briefly on the late Triassic c. 190 Mya, but not much; then move up to about 160 Ma, then 120. If I haven't lost interest/gotten too busy, I'll continue in roughly 30-40 million year jumps.
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Vultur-10


ATEK Azul
Jul 6 2010, 05:50 PM
I like the sound of this though I am wondering why the Cretacious ends early?


Volcanic events are different in general; there just happens to be a really nasty, enormous one then.

Quote:
 
Also will this mean a higher diversity of Synapsids, Archosaurs and Pterosaurs after the Mesozoic?


Not by much. The synapsids lose out slowly during the Mesozoic to the various archosaurs, there aren't many left by the end-Cretaceous (arboreal and flying, basically), and the ones that do exist aren't as good at fast recovery as the end-Cretaceous mammals in our timeline. Archosaurs get the upper hand in that recovery. Then the Chicxulub impactor comes along 15 million years later and tears everything up again.

After everything settles down, what's left for land vertebrates are the flying synapsids ('owlaroos'), some land crocodilians and a few other crurotarsan types, little lizardy things (both actual lizards and lizardlike crurotarsans), and ... that's pretty much it, barring some relicts that don't amount to much. The comination of the two events is far nastier than even our K-T.

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And if Dinosaurs never take over, does this world have their ancestral forms until present day?


No, heavy competition in the early Jurassic pretty much weeds things down. Some non-dinosaurian dinosauromorphs might survive on an isolated island area -- Madagascar- or Australia-like -- but I think they're pretty much gone by Pangaea breakup.

In general, there is more 'high-level' taxonomic diversity among large land species in the alt-Mesozoic (with saurischian and ornithischian dinosaurs, crurotarsans, therapsids, and some other reptile groups all contributing) but fewer actual species and genera.

Most of the 'traditional' groups - true sauropods, coelurosaurian and maniraptoran theropods (thus no tyrannosaurs or raptors), pterodactyloid pterosaurs, etc. - don't develop, though the longicollids get pretty close to sauropods in the late Jurassic (more like sauropod-giant ground sloths, though).
Edited by Vultur-10, Jul 7 2010, 12:51 AM.
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Vultur-10


Toad of Spades
Jul 6 2010, 11:54 PM
If birds never develop and neither do pterodactyloids, does that mean Rhamphorhynchoids take their place?


At first. Then mammals get into the air (the Latiptera, 'owlaroos') and push the pterosaurs up to the bigger size ranges. At those sizes, the Cretaceous extinction hits them very badly, and the asteroid 15 MY later finishes the job (Mostly, anyway. I may stick a Cenozoic island of flightless pterosaurs out in the remote Pacific somewhere.)

Quote:
 
Also with no T-J extinction, do marine groups stay the same?


No. Conodonts carry on for quite a while, marisaurs (fully-aquatic phytosaur-descendants) appear and mosasaurs don't, plesiosaurs eventually fall by the wayside to some weirdo archosauromorphs (think Tanystropheus relatives) and odd marisaurs. Placodonts go crazy in the late Jurassic and get INCREDIBLY HUGE. Some weird cephalopods too, probably.
Edited by Vultur-10, Jul 7 2010, 12:58 AM.
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Carlos
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Quote:
 
What did you do with the flora there?


Nothing special actually; I used the late Cretaceous explosion of angiosperms as a method to replace most crurotarsan herbivores by herbivorous crocodilians. The Cenozoic still has several ancient flora like seed ferns, gingkos and horsetails, the latter two more diverse than on Earth
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

My Patreon:

https://www.patreon.com/Carliro

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SIngemeister
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Hmmm...interesting. Your focusing a lot more on climate than I did/am doing. I'm not that good at that sorta thing.
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Toad of Spades
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After the meteor hits, what kinds of creatures survive. Do enough small dinosaurs or small crurotarsans survive to recover and dominate again.
Sorry Link, I don't give credit. Come back when you're a little...MMMMMM...Richer.

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Vultur-10


Oops, true sauropods *do* exist, as they appeared before the T-J extinction. Rapidly outcompeted in this timeline by longicolloids though.

And on that note...

LONGICOLLOIDEA - This sauropodomorph group developed from forms similar to Efraasia. They range from 50-100 kg to several tons in the Latest Triassic, but achieve much greater sizes in the Jurassic. Longicolloids are mostly omnivores, especially the basal forms. They have five load-bearing toes on hindfeet, four load-bearing toes and a raised claw on forefeet, in basal forms, but the foot becomes modified in more advanced types. Longicolloids are notable in that their sexual dimorphism varies; in some genera the male is larger, in some the female.

Fin-Neck
(Protolongicollus superbus)
Size: 4-5.5 meters long, 300-800 kg (males slightly larger)
Diet: Omnivorous - leaves/fronds, invertebrates
Habitat: Moist coastal forests
Time: Latest Triassic (c. 190 mya)

The Fin-Neck is a moderate-sized basal longicolloid, rather stockily built. It is named for the huge, colorful fin on its neck, used as a display structure. However, the fin grows large and bright-colored only in the breeding season; it is smaller and drab at other times.

Fin-Necks feed primarily on leaves and fronds, but also claw open rotting logs to eat the insects and other invertebrates within. They will occasionally eat fresh carrion as well - sometimes chasing predators smaller than themselves from their prey.

Fin-Necks are territorial and quite aggressive. In the breeding season male Fin-Necks are very hostile to anything but females of their species. Few Triassic predators will challenge an angry bull Fin-Neck, though the largest might. Fin-Necks tend to lay 12-20 eggs per nest; eggs hatch in midsummer and hatchlings take three to four years to mature.



Swamp Dragon
(Palustridraco lacustris)
Size: 2.8-3.5 meters long, 50-100 kg (females slightly larger)
Diet: Omnivorous - fish/small reptiles, invertebrates, carrion, water plants, leaves/fronds
Habitat: Wetlands and riparian/lacustrine environments (shores of rivers and lakes)
Time: Latest Triassic (c. 190 mya)

The Swamp Dragon is a lightly built (long neck and tail) basal longicolloid. It is named for its favored habitat.

Swamp Dragons are rather more predatory, and have a higher-meat diet, than most longicolloids. Their heads are wide and their teeth sharp for this reason. They eat almost anything they can catch, and favor carrion -- they are quite resistant to most of the common bacteria of rotting meat. They do eat a large amount of plant matter, however.

Swamp Dragons nest on higher ground than the adults' favored environments, tending to lay 8-15 eggs per nest. Hatchlings migrate down to the wetlands in their late first year, maturing at two and a half to three years of age (males slightly earlier).


Edited by Vultur-10, Jul 11 2010, 05:58 PM.
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Vultur-10


Lake Wyvern (Palustridraco giganteus)
Size: 5.6-7.5 meters long, 700-2400 kg (females slightly larger)
Diet: Omnivorous
Habitat: Rivers, lakes, shores (riparian/lacustrine environments)
Time: Latest Triassic (c. 190 mya)

The Lake Wyvern is an aberrant longicolloid, and one of the largest longicolloid species of this period. A more herbivorous relative of the Swamp Dragon (likely due to its larger size and slower movements), it is still quite capable of killing large fish and the smaller phytosaurs, and quite fond of carrion. Their heads are somewhat narrower than those of Swamp Dragons, and their forefeet are webbed.

Like Swamp Dragons, Lake Wyverns nest on higher ground than the adults' favored wetlands. The female generally lays 15 to 20 eggs, though nests with 25+ eggs are possible. Hatchlings migrate down to the wetlands in their first year; Lake Wyverns mature at four to five years.

SAUROPODA

Ferngrazer
(Microsauropodus minimus)
Size: 3-4.5 meters long, 150-380 kg
Diet: Herbivorous, primarily ferns
Habitat: Open woodlands and fern savannas
Time: Latest Triassic (c. 190 mya)

In the world of Crurosauria, the sauropods never amounted to much. This species is one of the last sauropods -- tiny compared to its real-Earth relatives. Ferngrazers are restricted to small patches of habitat in northern Pangaea. In appearance, they are rather generalized sauropods, except for their size.

Ferngrazers lay 8 to 12 eggs and take two years to mature.

Next post: the largest animal of Crurosauria's Triassic!
Edited by Vultur-10, Jul 23 2010, 10:59 PM.
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