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| Terra Phytosauria | |
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| Topic Started: Nov 17 2010, 12:10 PM (765 Views) | |
| Carlos | Nov 17 2010, 12:10 PM Post #1 |
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Adveho in me Lucifero
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Before the crocs there were the phytosaurs, which sadly became extinct in our world, being very affected by the Triassic extinctions, although managing to survive as marine gharial like forms for a while in the early Jurassic. But what if phytosaurs came out triumphant of the Triassic? This is a mini-project that speculates the evolution of phytosaurs if they had not disappeared in the early Jurassic, but if they instead had diversified, regaining their Triassic diversity. This has an impact on aquatic reptile evolution for the following 199 million years. As I said, this is a mini-project, because it only really deals with a few clades. Nonetheless, I find it entertaining. History of events Jurassic: After the Triassic/Jurassic transitions, phytosaur diversity was quite shaken. However, enough genera managed to survive, and they quickly expanded ecologically. The seas were now devoid of many linages of aquatic sauropsids, like nothosaurs and thalattosaurs, thus allowing phytosaurs to explore marine environs. The survivers were forms akin to Mystriosuchus, already convergent with our teleosaurids, dyrosaurids and gharials, and they quickly developed forms akin to metriorhynchids. Others returned (or remained) in freshwater habitats, where crocodile snouted forms similar to the Triassic Smilosuchus or Redondasaurus evolved, now preying upon the now very diverse herbivorous dinosaurs that came to drink on river margins. Crocodillians ventured into aquatic niches briefly as otter analogues (essencially caiman/dwarf crocodile like forms), but choristoderes and sphenodontians are also occupying similar niches, and they quickly vanish. Meanwhile, placodonts also survive, restricting turtles to freshwater habitats. Cretaceous: Phytosaurs keep diversifying. During the Turonian, several linages disappear, but are quickly replaced. Unlike crocodillians in our world, they don't vanish from the seas for a period of time, instead always have a foot there, at the expense. However, the Cretaceous mini extinctions still allow the evolution of neochoristoderes (champsosaurs and simoedosaurs), the gharial/crocodile like champsosaurs, which prove to be very competent adversaries. Crocodiles are still incapable of colonising aquatic niches, other than a few caiman like forms. Placodonts begin receiving competition from turtles in their marine habitats, as the Turonian extinctions made them decline somewhat. Cenozoic: Crocodillians disappear, aside from a few gondwannan forms, mostly descendent of the few caiman like forms; in South America and India (which colides with Asia in the Eocene), their Pristichampsus like forms become dominant predators for a short period of time, until mammals and birds prove themselves to be better terrestrial predators. On Australia forms that resemble the mekosuchines expand both on land and on freshwater, the later declining in the Neogene as Australia dries up, and the availiable aquatic environments are mostly taken by phytosaurs. In Madagascar, crocs manage to form a stronghold, but again aquatic niches are taken by phytosaurs. Phytosaurs have indeed a monopoly over crocodile like niches, having merely to compete with choristoderes. Marine ecosystems are in the middle Cenozoic taken by champsosaurs and phytosaurs much like gharials did in our world, but both linages decline both on salt and freshwater as the Pliocene cooling occurs. Nowadays, about 18 phytosaur species remain, along with 7 champsosaur species. Meanwhile, placodonts lost their war against turtles, the last ones gone by the end of the Eocene. |
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| Cephylus | Nov 17 2010, 08:37 PM Post #2 |
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Torando of Terror
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interesting project. So phytosaurs and champsosaurs replace almost all semi-aquatic crocodilians? |
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| The Dodo | Nov 17 2010, 08:46 PM Post #3 |
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Prime Specimen
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It seems so. How about some terrestrial phytosaurs, I think they would be interesting if the evolved from species like Nicrosaurus. |
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| Carlos | Nov 18 2010, 02:59 AM Post #4 |
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Adveho in me Lucifero
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Indeed there will be some, although they will not be as common as land crocs were on our world |
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| spartan | Nov 18 2010, 07:12 AM Post #5 |
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DoomSlayer Wanderer
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Interesting. I know a little about this crocodiles. But I never think their triumph. So I will check this:) |
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| Carlos | Nov 18 2010, 10:38 AM Post #6 |
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Adveho in me Lucifero
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Phytosaur clades During the Mesozoic, phytosaurs diverged over several clades, some replacing each other over the course of their evolution. The vast majority of post-Triassic phytosaur diversity evolved from Mystriosuchus like forms, but not all did. Nicrosauridae Nicrosaurids were the exception to the rule. Along with their marine relatives, these forms survived the Triassic extinction event, and during the Jurassic they kept the same ecological role. The key external feature are their jaws; while they are thin, the upper jaw is quite deep, thus allowing it to distribute the pressure of their extremely strong bites while keeping the jaws thin, which has the side effect of having more concentrated biting pressure. This is very similar to the situation in several rauiusuchians and theropod dinosaurs. Later forms also lost the anteorbital frenestra for this effect. These phytosaurs were among also the most adapted to terrestrial locomotion, having stronger limbs, longer metatarsals and special adaptations in the pelvis for this effect. Still, they were vastly inferior to crocodillians in this respect, and these forms only occured where predatory land crocs were rare. As the Jurassic ended their aquatic relatives began pushing them off aquatic niches, ence they were forced to become more terrestrial. For a while asian terrestrial forms managed to survive, disappearing during the Campanian. Armadillong One of the last nicrosaurids, this creature lived in the early late Cretaceous of Mongolia. It was well adapted to terrestrial life; its tail was now more cilindrical in shape unlike the deep, laterally flat tail of other phytosaurs, its legs were robust and its pelvis had very flexible joints. It was among the most heavily armoured of all phytosaurs, similar to Armadillosuchus in terms of its exoskeleton. It was a good digger, and it most likely ambushed prey in the forest undergrowth, when not scavenging the kills of theropods. It seems to have had parental care, as adults have been found in a protective position around nests. Mystriosuchoidea The main clade, which includes nearly all post Triassic phytosaurs, as well as all Cenozoic species. Eopseudochampsidae Some linages of mystriosuchoids abandoned the fish hunting diet of their ancestors and specialised in killing larger prey. This occured several times in the evolution of derived phytosaurs, leading to many cases of convergent evolution. The earliest case of this is are the eopseudochampsids. These phytosaurs strongly resemble Triassic forms like Redondasaurus, having wide, crocodile like snouts with dagger like teeth. Having evolved shortly after the Triassic, these creatures spread across the landmasses, and later successfully invaded marine habitats as well; this is quite well noted for the presence of quite large anteorbital fossae, which in life housed salt glands. This linage is notable for having produced among the largest phytosaurs of all time, some of which inspired terror even among large marine sauropsids such as pliosaurs and mosasaurs. The Turonian, however, was not very kind to these animals, and they disappeared, with one genus surviving until the end of the Cretaceous; other predatory phytosaurs would reach large sizes as well, but they would be fewer and far between. Titanophytosaurus The largest of all eopseudochampsids was also the last. Living as late as the Maastrichian in Africa, South America and Madagascar, this monster reached as much as 14 meters long and likely was as heavy as 10 tons. So big as it was, it is unknown if it was even capable of moving on land, although the females (generally smaller than males) certainly did for it layed eggs. Unlike its equivalent on HE, Sarcosuchus, there is little controversy regarding its feeding habits, as it was just as adapted to prey on the very large sarcopterygians which shared its habitat with as it was to kill dinosaurs. Because it occurs in marine habitats as well, prey like turtles, plesiosaurs, sharks, marine phytosaurs and mosasaurs were on its diet as well. A tooth found in the Campanian of Kansas suggests that this animal has at some point colonised north american shores, although it seems to have not stayed permanently. Allothalattosuchia While several phytosaurs conquered the sea, this linage took specialisation to a marine lifestyle to its logical conclusion. These critters were essencially the phytosaur answer to metriorhynchids, except that they had somewhat more success than their HE analogues. They completly lost their osteoderm covering, and their limbs became flippers, while their tail became shark like 8only with the lower lobe being the one supported by the skeleton instead of the upper one, as in metriorhynchids and ichthyosaurs). Whereas they came ashore to lay eggs or not is unknown, but they lasted for longer then metriorhynchids, and explored niches they haven't explored, like that of large filter feeders. The Turonian eventually ended most of them, except for the filter feeding forms, which survived until the Maastrichian. Eupelagochampsus A genus of several species that lasted from the late Jurassic to the very beginning of the late Cretaceous. These animals were essencially the phytosaur answer to a dolphin or a marlin/swordfish, ranging from 2 to 4 meters in length and having a crescent shaped tail (more perfect in later species obviously) and long, thin jaws; it seems that at least later species also had a small dorsal fin. Whereas it came on land to lay eggs or not is unknown, but the part of the tail that supported the lower lobe had at its base an articulation in the vertebrae that allowed it to bend upwards to an almost vertical position, which seems to imply they in fact did so. Paradakosaurus As the name implies, rather than a fish hunter this animal, with a short, deep and broad snout, was something of a white shark/orca analogue. Indeed when it was first discovered it was though to be a marine eopseudochampsid, before more complete remains were found. It lived in the early Cretaceous, and it did co-exist with a few marine eopseudochampsids, as well as with large pliosaurs like Kronosaurus. Pelicanochampsus Filter feeding allothalattosuchids evolved in the middle early Cretaceous, and lasted longer than their relatives. Much like baleen whales, their "baleen" (in this case very thin, long teeth) were located in the upper jaw, and they developed pouches on their lower jaws. Feeding on crustaceans and small fish, these animals occured on both fresh and salt water, and took the place of our world's stomatosuchids. This particular genus is the largest phytosaur to have ever lived, adult males up to 15 meters long and weighting 10.8 tons. It occured across the northern hemisphere, on both North America and Europe; it seems to have been a pelagic animal, although it might have returned ashore to lay eggs, as females are significantly smaller than males. Neophytosauria Having evolved in the Cretaceous, this clade includes both modern species and several of their late Mesozoic relatives. Having began as gharial like fish hunters, the Turonian allowed them to diversify as the other main clades declined. Soon they produced eopseudochampsid like forms, and surviving the KT event they, alongside champsosaurs, later entered the seas, competing with early whales, although they never became as specialised as allothalattosuchids. Currently several species still exist, and while very conservative they are still slightly diverse. The main feature of this clade is that the anteorbital frenestra/fossa fused with the orbit, a situation convergent with that of neornithe birds. Species examples will come later. |
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| The Dodo | Nov 18 2010, 05:12 PM Post #7 |
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Prime Specimen
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Great list. With the Nicrosauridae their ancestors had different teeth for different purposes, with larger teeth up the front and smaller ones up the back. As they evolve they could build on it and evolve more specialized teeth. |
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| Carlos | Nov 18 2010, 06:07 PM Post #8 |
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Adveho in me Lucifero
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True, but for a terrestrial carnivore I don't see much the use for an heterodont dentition. |
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| colddigger | Nov 18 2010, 07:04 PM Post #9 |
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Joke's over! Love, Parasky
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Perhaps to give them a wider variety in their diet? Molaresques to crack bone and get marrow, more blade-like teeth for slicing, and sharp, more peg-like, teeth at the front to grab prey? Although the peg teeth might get ripped out...hum... |
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Oh Fine. Oh hi you! Why don't you go check out the finery that is SGP?? v Don't click v Spoiler: click to toggle | |
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| The Dodo | Nov 18 2010, 07:18 PM Post #10 |
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Prime Specimen
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They can grow them back can't they? |
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| Carlos | Nov 19 2010, 02:55 AM Post #11 |
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Adveho in me Lucifero
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Of course, much like other sauropsids (I don't know if that happened in pterosaurs though) |
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| Cephylus | Nov 19 2010, 03:01 AM Post #12 |
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Torando of Terror
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I love this mini-project. What about alligator-like phytosaurs, with crocodilian body shapes, a semi-aquatic predator of large prey but also feeds on fruit and floating water plants. |
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| Rick Raptor | Nov 19 2010, 10:26 AM Post #13 |
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Adolescent
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What about Carnivora? Lions, hyaenas, dogs... they all have heterodont dentition despite them being (mostly) carnivorous. |
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| Carlos | Nov 19 2010, 12:25 PM Post #14 |
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Adveho in me Lucifero
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Well, thats because their ancestors were heterodont. In sauropsids like tyrannosaurs, the appearently simple shaped tooth alone could have all the functions of a molar, incisor or canine, both by ripping off and cutting flesh and, if wide enough, breaking bone. Nicrosaurids had tyranossaur style teeth, ence not much specialisation would be required |
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