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April 1, 2010
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:iconeurwentala:
Some examples of the diversity of the crocodile-line archosaurs or Crurotarsi. This group was very common and diverse in the Triassic, and only a bit less so in the Jurassic and Cretaceous. Many of them were highly specialized and seem to have been active, possibly even warm-blooded animals. The group has many interesting examples of convergent evolution with dinosaurs and other groups. Now only the modern crocodiles remain.

In this picture, from top to bottom:
Saltwater Crocodile, Crocodylus porosus. The largest modern species of crocodile. An opportunistic predator that can eat anything from water buffalo to sharks.
Yacarerari. Belongs to the Cretaceous group Notosuchia. It was a cat-sized animal with very unusual mammal-like teeth.
Metriorhynchus. Member of the completely aquatic group Thalattosuchia. It had a tail fin and it's limbs were modified into flippers. It might have been viviparous, since it's body plan sure doesn't look suitable for laying eggs on dry land. Thalattosuchians are strongly convergent with ichthyosaurs and dolphins.
Terrestrisuchus. A small, obviously cursorian Sphenosuchian that could have weighed around 15 kg. It might be a juvenile specimen of Saltoposuchus.
Postosuchus. A member of Rauisuchia. It might have been partly or completely bipedal, since it's front limbs are small and weak. It was a large predator that had very similar head and teeth as the tyrannosaurid dinosaurs.
Effigia. Another dinosaur-like rauisuchian. It was a fast-running, bipedal animal very similar to ornithomimosaurs (the ostrich-mimic dinosaurs). It even had a toothless beak.
Desmatosuchus. A triassic aetosaur with very impressive armour. It was a herbivore with a surprisingly pig-like head.
Rutiodon. A crocodile-like phytosaur. Despite their appearance, phytosaurs were not closely related to the modern crocodiles. They seem to be another example of convergent evolution.
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:iconmechatherium:
~Mechatherium Feb 17, 2012
As for Metriorhynchus being viviparous, if hard evidence of that was found it would be fascinating. That would make it the only archosaur I know of that ever was.

--
"I am human . . .

. . . mostly . . ."
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:iconeurwentala:
*Eurwentala Feb 24, 2012
Yes, it would be really fascinating, though unlikely. I'd think that if viviparity was easy to evolve in archosaurs, it would have happened at least a few times, if not more than a hundred, as it has in squamates.

--
"Why do you necessarily have to be wrong just because a few million people think you are?"
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:iconill-fated-jedi:
Mood: Thrilled ~Ill-Fated-Jedi Oct 22, 2011
Great work. I wish you had included Stomatosuchus and Quinkana for a bit more crocodilian diversity, but I love your Notosuchid. Also I've heard rumours that we can't call them all Crurotarsi anymore because of the deviant nature of phytosaurs. [link]

--
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"Good and evil are names for what people do, not how they are."--Mary Malone, The Amber Spyglass
"Me? I'm always alright"--The Doctor
"But I think the best way to know God is to love many things"--Van Gogh
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:iconeurwentala:
*Eurwentala Oct 23, 2011
I read it too. It's a shame. Crurotarsi is a lot better name than Pseudosuchia. And Pseudosuchia doesn't make any sense anyway.

Maybe someone could just redefine Crurotarsi as anything that's closer to crocodiles than birds. Though I don't know enough about taxonomy to sya if it's possible.

These were drawn for a family tree published with an article about modern crocodile physiology, and so couldn't include all the cool cruro... umm, pseudosuchians, but I might do a larger family picture later. Stomatosuchus is especially interesting, and there are plenty of freaky notosuchids and baurusuchids too. And the sail-backed guys are missing also.

--
"Why do you necessarily have to be wrong just because a few million people think you are?"
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:iconill-fated-jedi:
~Ill-Fated-Jedi Oct 23, 2011
Sadly I think the problem is that Phytosaurs have been found to be outside the archosaur branch, but being more of a bird person I'm not entirely certain of the technical issues to resolve.

It would be awesome if you could expand to include some of the wierder Cenozoic and later Mesozoic crocs, because apart from Arizonasaurus these are most of my favourites from the Triassic era and of course the salty for comparison.

Cheers

--
.
"Good and evil are names for what people do, not how they are."--Mary Malone, The Amber Spyglass
"Me? I'm always alright"--The Doctor
"But I think the best way to know God is to love many things"--Van Gogh
||
||
||
=====
|| humility
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:iconeurwentala:
*Eurwentala Oct 23, 2011
Yes, and since the original definition or Crurotarsi is based on phytosaurs, Crurotarsi now techically includes everything that branches after phytosaurs, including dinosaurs and pterosaurs, and that's not exactly useful.

If Crurotarsi was defined again to include everything closer to crocodiles than birds, it would include the branch of the tree everybody wants it to include. Much like theropods are defined as everything closer to Allosaurus than Saltasaurus.

Taxonomy has a complex set of rules, though, and I'm not at all sure if names can be simply redefined like this.

--
"Why do you necessarily have to be wrong just because a few million people think you are?"
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:iconill-fated-jedi:
~Ill-Fated-Jedi Oct 23, 2011
I think the latter sentiment will win out, in the end, and we will have to content ourselves to the akward-sounding Pseudosuchia. Alternatively, a new name could be proposed for the group. However, there are exceptions, as taxonomists still prefer to call Megapnosaurus Synatarsus because Synatarsus is more serious even though it shares its latin name with a beetle species.

--
.
"Good and evil are names for what people do, not how they are."--Mary Malone, The Amber Spyglass
"Me? I'm always alright"--The Doctor
"But I think the best way to know God is to love many things"--Van Gogh
||
||
||
=====
|| humility
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:iconthemorlock:
~TheMorlock Sep 23, 2011  Student General Artist
Effigia is one strange creature.

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Check out my gallery: [link]

I am about 99% sure that Judas wasn't thinking of evolution when he betrayed Jesus.
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:iconeurwentala:
*Eurwentala Sep 24, 2011
It sure is. No wonder it was first described as an ornithomimid dinosaur, even though it lived tens of millions of years before them.

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"Why do you necessarily have to be wrong just because a few million people think you are?"
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:icondotb18:
*DOTB18 Sep 15, 2011
Personally, I'm enclined to think that metriorhynchids were ovoviviparous for the simple fact that, so far, there hasn't been a documented example of vivipary in any known archosaurs, extinct or otherwise. So until someone finds a fossil of a Metriorhynchus that died while it was pregnant or in labour, I'm going to envision them writhing up beaches and laying thier eggs in the sand like sea turtles.

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"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" ~Douglas Adams
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