The Saurocene

[ZoPteryx]

Okay, this one needs some explanation.  For starters, I figured this was more of a science than art related topic, so that's why I'm posting this in the Dinosaurs section, but mods feel free to move it if necessary.  

I've created, in my notebooks, a hypothetical Earth where the K/T collision event, which was the leading cause of the Cretaceous mass extinction, never occurred.  Therefore, dinosaurs and other previously extinct creatures have survived and evolved past the 65 mya mark.  All history prior to 65 mya is the same as our own.  All geologic features, positions of the continents, relative habitat distributions, etc, are the same as our home or Primary Earth (PE), except of course for the lack of a giant crater in Mexico and no global iridium layer.   Future humans from our timeline have figured out how to travel to parallel worlds and, amongst others, stumbled across this one.  Because it's so similar to PE (except for the fauna and some flora), it has been abbreviated as SE, Secondary Earth.  (Basically the plot is the same as the Speculative Dinosaur Project, but I've tried to make many of my creatures as different as reasonably possible.)

My goal with this thread is to get your opinions regarding the scientific accuracy and likelihood of evolving of the creatures that inhabit this world which I call the Saurocene (Saurocene being a replacement term for the Holocene).   Any other additional comments or suggestions are welcome!  I've got this world far more planned out than the brief intro here, so feel free to ask any questions you might have about anything! 

Renderings of the fauna will come shortly, but first, a basic introduction.

Non-Avian Dinosaurs:  The most studied group of SE vertebrates, dinosaurs are alive and mostly well in the Saurocene.  Some are easily identified; others look like nothing our Earth has ever seen.  As a general rule, the therapods are doing much better than the ornithsichians, even outcompeting them in some niches.  The sauropods are the worst off of all, clinging on only in the tropics.

Avian Dinosaurs:  Very abundant and successful, just like on PE.  The biggest difference being a few enantiorniths are still around, though they are generally rare.  Curiously, most groups of birds that evolved after the K/T boundary in our own timeline still evolved in the Saurocene.  The reasons for this are unclear, but it's a common phenomenon amongst smaller organisms on SE.

Pterosaurs:  While their continued existence wasn't confirmed until recently, pterosaurs are now known to be rather widespread.  All living species are descended from the azdharchid pterosaurs.  Most are pelagic predators that travel great distances, but a few are actually flightless.  Most pterosaurs in the Saurocene are very large; perhaps they were forced to become giants by increasingly abundant birds.

Crocodilians:  Doing well, more diverse than in PE, but not quite as widespread as in the Mesozoic.  Most are rather typical looking, with a few big exceptions.

Plesiosaurs:  Of this group, only the elasmosaurs have survived to the present.  Restricted primarily to the tropics, most have retained their typical body plan.

Mosasaurs:  The top predators in most of the world's oceans, they have evolved to become increasingly fish/shark-like.

Ichthyosaurs: Yes, you read that correctly, ichthyosaurs are a rare component of SE's oceans.  It appears that some time during the late Jurassic or early Cretaceous, a group of ichthyosaurs became hyper-specialized to deepwater environments, to avoid the increasing competition in coastal waters.  This is why their fossils have never been found past the early late Cretaceous.

Ultraichthyosaurs:  Descended from the ichthyosaurs, these are the most highly evolved aquatic tetrapods ever.

Other reptiles:  Snakes, lizards, and turtles are all vastly understudied, but are similar to their PE counterparts in most respects.  Sphenodonts enjoy greater diversity and range in SE, but are still not common.

Amphibians:  Mostly the same as those we are familiar with, but a few temnospondyls persist in the Australian region.

Mammals:  Very diverse and increasing.  Mammals took advantage of fluctuating dinosaur populations during the Cenozoic, some growing to considerable sizes.  Most modern mammal groups are present even if they don't look the same as those we're familiar with.  A big exception is bats, which are absent, apparently replaced by nocturnal birds.

Bony Fish:  The most numerous vertebrates, but severely understudied.   Most familiar groups, or equivalent groups, are present.  Most of the characteristic Mesozoic varieties have died out.

Cartilaginous Fish:  Sharks and rays are abundant.  With the exception of a few hybodont sharks, most are familiar.

Invertebrates:  Ammonites, belemenites, and rudists aside, the inverts of SE are almost identical to our own, some even down to the species level.

Flora:  While some plants and fungi may look peculiar, most belong to recognizable groups, although the distribution of these groups may be somewhat different on SE.

Well, I hope you've enjoyed this "little" introduction to the Saurocene.  A more detailed analysis will follow soon, but until then, I enthusiastically await your thoughts, questions, and suggestions!

[Yutyrannus]

Awesome!!!! I'm glad you finally revealed it! I would really like to contribute to this if I can.

[ZoPteryx]

Awesome!!!! I'm glad you finally revealed it! I would really like to contribute to this if I can.

Glad you like it!   I don't need any help at the moment, but if this ever turns into anything more I'll definitely seek you out!


Okay, it's time to meet some of the Saurocene's inhabitants, starting with our favorites, the dinosaurs!

Therizinosaurids:  These peculiar therapods have been very successful through the Cenozoic, even diversifying somewhat.  They can be found across the Northern Hemisphere and in parts of Africa and South America.  Four genera exist at the present (from top to bottom): Pachyonyx (Rooters) , Ursasaurus (Spearfishers) , Neotherizinosaurus (Greater Zinos), & Neofalcarius (Lesser Zinos).

- Rooters (3 species) can be found in Africa and southern Asia where they prefer semi-arid and savannah environments.  They use their robust claws to dig for roots and break into termite mounds.  They will also eat young leaves, fruit, and carrion.  Growing to 8 meters (24 feet) in length, Rooters live primarily solitary lives.
- Spearfishers (2 species) live in northwest North America & and east Asia.  They are amongst the largest living therapods growing to 12 meters (36 feet) or more in length.  Their scientific name is a reference to their diet, primarily berries, young leaves, fish, and small game.  Spearfishers are very territorial, except during the breeding season.
- Greater Zinos (at least 4 species) live across the Northern Hemisphere where they pursue a typically vegetarian existence, browsing high in trees.  Growing nearly 11 meters (33 feet) in length, herds of these beasts have few enemies.
- Lesser Zinos (at least 3 species) endemic to the Americas members of this genera are actually advanced therizinosaurs, despite being named after a basal genus.  They are small, mostly under 6 meters (18 feet) in length.  Lesser Zinos are almost strictly vegetarian and rely primarily on camoflauge and keen eyesight to evade predators.

Pavosaurids:  A peculiar group of small therapods native to south & southeast Asia, pavosaurids are true enigmas.  Until recently, they were classified as enantiornith birds, then as advanced maniraptors close to the scansoriopteryxids requiring a ghost lineage through the Cretaceous.  Recent DNA evidence contradicts both theories, placing them close to the alverasaurids, ornithomimids, and theriziosaurids; all basal manirpators.  The reigning theory now is that pavosaurids are descended from basal alverasaurids that lived in the Southern Hemisphere and arrived in the north via the Indian subcontinent.  Fossil evidence loosely supports this.  Two genera exist currently (from top to bottom): Pavosaurus (Pheaznots) and Pteracaudipteryx (Deltas).  Both are poorly known due to their nocturnal habits.

- Pheaznots (at least 4 species) can be found on the Indian subcontinent.  They are small, the largest species has a length of only 0.7 meters (2 feet), not including its long tail feathers.  Terrestrial or semi-arboreal, they use their dextrous beaks to eat seeds, nuts, fruit, insects, and small animals.  Pheaznots travel in small groups led by a dominant pair.  Males are far more colorful than females.
- Deltas (at least 4 species) can be found from west India to southeast Asia and on some Indonesian islands.  They get their name from their peculiar tails which actually serve as a lifting surface when fanned out, allowing these very small animals to glide between trees.  The front arms act as stabilizers and a rudder during this process.  As the landing zone approaches, they fold in their tail feathers, shifting the lift from their tail to their arms, the result being that they tilt upward; perfect for landing on tree trunks.  Living in pairs, the nocturnal Deltas are thought to be primarily insectivores.

Thoughts?

[Jetoar]

Amazing idea and wonderful draws. I like it. I have done figures with cly of mammals and reptiles that they follow other way of evolution  . I remember  books as Life after Man and modern dinosaurs  .

[Yutyrannus]

Awesome!!!! I'm glad you finally revealed it! I would really like to contribute to this if I can.

Glad you like it!   I don't need any help at the moment, but if this ever turns into anything more I'll definitely seek you out!


Okay, it's time to meet some of the Saurocene's inhabitants, starting with our favorites, the dinosaurs!

Therizinosaurids:  These peculiar therapods have been very successful through the Cenozoic, even diversifying somewhat.  They can be found across the Northern Hemisphere and in parts of Africa and South America.  Four genera exist at the present (from top to bottom): Pachyonyx (Rooters) , Ursasaurus (Spearfishers) , Neotherizinosaurus (Greater Zinos), & Neofalcarius (Lesser Zinos).

- Rooters (3 species) can be found in Africa and southern Asia where they prefer semi-arid and savannah environments.  They use their robust claws to dig for roots and break into termite mounds.  They will also eat young leaves, fruit, and carrion.  Growing to 8 meters (24 feet) in length, Rooters live primarily solitary lives.
- Spearfishers (2 species) live in northwest North America & and east Asia.  They are amongst the largest living therapods growing to 12 meters (36 feet) or more in length.  Their scientific name is a reference to their diet, primarily berries, young leaves, fish, and small game.  Spearfishers are very territorial, except during the breeding season.
- Greater Zinos (at least 4 species) live across the Northern Hemisphere where they pursue a typically vegetarian existence, browsing high in trees.  Growing nearly 11 meters (33 feet) in length, herds of these beasts have few enemies.
- Lesser Zinos (at least 3 species) endemic to the Americas members of this genera are actually advanced therizinosaurs, despite being named after a basal genus.  They are small, mostly under 6 meters (18 feet) in length.  Lesser Zinos are almost strictly vegetarian and rely primarily on camoflauge and keen eyesight to evade predators.

Pavosaurids:  A peculiar group of small therapods native to south & southeast Asia, pavosaurids are true enigmas.  Until recently, they were classified as enantiornith birds, then as advanced maniraptors close to the scansoriopteryxids requiring a ghost lineage through the Cretaceous.  Recent DNA evidence contradicts both theories, placing them close to the alverasaurids, ornithomimids, and theriziosaurids; all basal manirpators.  The reigning theory now is that pavosaurids are descended from basal alverasaurids that lived in the Southern Hemisphere and arrived in the north via the Indian subcontinent.  Fossil evidence loosely supports this.  Two genera exist currently (from top to bottom): Pavosaurus (Pheaznots) and Pteracaudipteryx (Deltas).  Both are poorly known due to their nocturnal habits.

- Pheaznots (at least 4 species) can be found on the Indian subcontinent.  They are small, the largest species has a length of only 0.7 meters (2 feet), not including its long tail feathers.  Terrestrial or semi-arboreal, they use their dextrous beaks to eat seeds, nuts, fruit, insects, and small animals.  Pheaznots travel in small groups led by a dominant pair.  Males are far more colorful than females.
- Deltas (at least 4 species) can be found from west India to southeast Asia and on some Indonesian islands.  They get their name from their peculiar tails which actually serve as a lifting surface when fanned out, allowing these very small animals to glide between trees.  The front arms act as stabilizers and a rudder during this process.  As the landing zone approaches, they fold in their tail feathers, shifting the lift from their tail to their arms, the result being that they tilt upward; perfect for landing on tree trunks.  Living in pairs, the nocturnal Deltas are thought to be primarily insectivores.

Thoughts?

Very cool! I wanted to ask if I can make Kato Polyclay (or other clay if need be) sculpts to go with the Saurocene (once I have the skill of course)? I would probably start with mosasaurs, ultraicthyosaurs, or elasmosaurs because I would definatly not be able to sculpt feathers for a while and I just want to start with marine reptiles for some reason.

[ZoPteryx]

Feel free Yutyrannus!  I'm very interested to see what you'd come with!  I'll have illustrations of some marine reptiles soon.

Some more stuff:

Troodontids:  While quite successful during the early Cenozoic, true troodontids began to decline in diversity during the Ice Ages, outcompeted by deinonychosaurids for meat and by ovirpatorids for plant matter.  One genus, Borealraptor (about 5 species, known as Feather-foots), exists today.  Completely feathered, it dwells in places too cold for most other predators where it subsists on small game, carrion, and berries.  Typically living in pairs, they can be found throughout the northern most Northern Hemisphere.


Grusasaurids:  Descended from the troodontids some time in the Oligocene, these peculiar crane-like dinosaurs live in a similar fasion to their bird look-alikes.  Capable of powered flight, the odd orientation of primary feathers on their hands means that to fully extend their wings, their hands must point forward, not parallel to the wing as in most winged dinosaurs.  They can be found throughout the world, except for Australia and Antarctica.  Two genera exist: Grusasaurus (top) and Microgrusasaurus (bottom).  They are known as Ranes (raptor + crane) and Microranes, respectively (the alternative name was Craptor... ).


Simioraptorids:  Descended from a common ancestor with the grusasaurids, these small arboreal dinosaurs are endemic to the Americas.  The fossil record indicates that they evolved in North America, but quickly spread to South America during the Pliocene, which now holds the the bulk of their diversity.  Some species glide using elongated feathers, but most prefer to leap from tree to tree as they search for insects, small animals, eggs, and fruit.  One unique feature is their ability to pronate their hands, an adaptation to leaping.  This is achieved not by crosssing the radius over ther ulna, as in primates, but by having greatly reduced upper hand bones and especially strong tendons in their place; their hands could be described as "free floating", free from the lower arm bones, making nearly 360 degree pronation possible.  Some species are solitary, while others are highly social.

From top to bottom:
Simioraptor (Leapers, about 10 species):  A widespread, generalist genus.
Chloronychus (Greenies, 3 species):  S. America only.  Named for its greenish plumage, caused by symbiotic algae.  Mostly frugivorous.
Florasaurus (Rainbow-Raptors, at least 10 species):  Widespread and often exoticly plumaged.  Generalist diet.
Colibrisaurus (Rainbow-Raptors, about 6 species):  Colorful genus found in the American tropics.  Feeds mainly on insects and nectar.
Neomicroraptor (Gliders, 6 species):  Widespread insectivores. They use their elongated middle finger to probe for insects.

Thoughts?  Scientific concerns?

[TheAllosaur]

HaHA! Sweet!
These are cool and it's a cool idea. I  think it is a very awesome project.
Ever considered Allosaurs? Like Giganotosaurus and Megaraptor descendants.

[ZoPteryx]

HaHA! Sweet!
These are cool and it's a cool idea. I  think it is a very awesome project.
Ever considered Allosaurs? Like Giganotosaurus and Megaraptor descendants.

I have actually.   I originally intended that Neovenatorids would survive as the top predators of Australia, but in the end I abandoned that idea because they would have very little large prey to hunt.  So both the Carcharodontosaurids and Neovenatorids are extinct in the Saurocene.  However, while I don't have any images to share, they do have any interesting evolutionary history!

Carcharadontosaurids:  These super predators did very well on all the southern (and a few northern) continents through the Paleocene and Eocene, but as the climate dried out later in Cenozoic, the big herbivores they relied on began to disappear, leading to their extinction everywhere, everywhere except South America.  Isolated, and still surrounded by their prefered prey (sauropods), they evolved into the most massive terrestrial predators Earth has ever seen, the Steroidosaurids.  As their name suggests, these titans resembled a version of their ancestors on steroids!  Massively robust skulls with jaw muscles so huge they stretched down the majority of the neck!  Giant, serrated, triangular teeth lined their jaws; leaving their tiny arms virtually useless.  The largest species grew to nearly 25 meters (75 feet) in length, about half of this was thick tail.  Despite their length, Steroidosaurs were relatively low slung with short robust legs and were probably quite slow.  Many species had a small sail over their hips, which may have helped strengthen their back and tail.  These monsters relied entirely upon the varied array of sauropods they shared their continent with for food.  During the American Faunal Exchange of the Pliocene, new varieties of herbivores arrived from the north and outcompeted most of the sauropods into extinction.  Without prey, the great Steroidosaurs soon followed suit.  The last species lived in central South America during the late Pliocene.

Neovenatorids:  While they never grew into giants, these predators led a similar evolutionary path to the Carcharadontosaurids.  Like them, they eventually became reduced to a single island continent, except that continent was Australia.  Here, they competed fiercely with the continents other relict group of therapods, the Spinosaurs.  During the dryer times, the Neovenatorids dominated; during wetter times, the Spinosaurs ruled.  As the Ice Ages approached and continent dried further, the Neovenatorids took over almost entirely, and then, in a span of only about 5 million years, they vanished.  Like the Carcharodontosaurids before them, it appears that a loss of their prefered large prey was the reason for their eventually extinction in the late Pleistocene.  Amazingly, the more varied diet of the Spinosaurs allowed them to surivive the climate changes.  During their reign, the Neovenatorids stayed relatively average-sized, generalist big-game predators.  A few short lived varieties specialized, such as the magnificently crested early Pliocene Hexalophosaurus.

[TheAllosaur]

Ah, well, at least they lived for a while.
Are you going to draw them? Cause they sound really cool!
It seems all the speculative dinosaur things out there are all killing off the Allosaurs. Not in mine (which I will, maybe, do shortly.) They might even take over the Tyrannosaurs. 

[Yutyrannus]

Anything new coming? Tyrannosaurs perhaps? Abelisaurs?

[ZoPteryx]

Anything new coming? Tyrannosaurs perhaps? Abelisaurs?

You want tyrannosaurs?  I give you tyrannosaurs!

Neotyrannosaurids: Among the most anticipated of the Saurocene's fauna were tyrannosaurs.  It didn't take long to find them, as they are among the most numerous of the Northern Hemisphere's top predators.  They appeared just as scientists had expected: large heads, bone crushing teeth, and a relatiely large size; their only quirk being their complete lack of arms.  It was decided that the loss of an appendage that was already greatly reduced was not a major change, so the living species were classified as tyrannosaurids, along with Tyrannosaurus and other famous giants.  However, the discovery of the peculiar Suchotyrannus led to doubts about this.  An anatomical reanalysis, combined with new paleontological data, has revealed a much more peculiar identity.  It was found that the great tyrannosaurids had died out in the late Oligocene, leaving their niche open to one of their relatives, the tyrannosauroid dryptosaurids.  Their modern descendents' physical characteristics are simply examples of convergent evolution, including their even more greatly reduced front limbs.  Two new groups were thus created, the Neotyrannosaurids (shown first) and the Suchotyrannids (shown second).

Neotyannosaurus (top)(Tyrants, 7 species):  Found throughout the Northern Hemishere, members of this genus are generalist big game hunters with some species reaching up to 36 feet (12 m) in length.  Most are considerably smaller.  They are not the top predators in most places, but they are the ones most likely to try and take down the largest of game.  These species typically live in pairs or are solitary.
Hyaenasaurus (bottom) (Gnashers, 3 species): Found only in Eurasia and Africa, members of this genus are primarily scavengers, using their relatively blunt teeth to crunch through bone.  They are solitary and territorial animals, the largest of which grows to 30 feet (10 m) in length.

Suchotyrannids:  This is an ancient monotypic family that probably dates back to before the dryptosaurid/neotyrannosaurid split (early Pliocene).  Specialized fish-eaters, they have always existed in Eurasia just as they do today.  Their long arms bear a single digit, armed with a large hook-like claw. These and their elongated and notched snouts and their many small teeth aid in their pursuit of fish.  Partially webbed feet give them stability while walking on mudflats and also aid in swimming.  A more extensive feathery coat than most other dinosaurs gives them the advantage in cold water and snow.

Suchotyrannus (Croc-Tyrants, 2 species): Fun Fact: They were originally mistaken for cold-adapted spinosaurs!

Coming next: the dromaeosaurids and their bizarre relatives!

[Yutyrannus]

Awesome. Also, are there moder-day spinosaurids in Australia in the Saurocene?

[TheAllosaur]

Or abelisaurs? i am in an Abelisaur stage right now, Majungasaurus' fault.

[ZoPteryx]

Both are present and will be revealed shortly!

[ZoPteryx]

As the Spinosaurs and Abelisaurs are still in progress, I thought I'd share the Saurocene's most widespread terrestrial predators, the "Raptors"!

Deinonychosaurids:  These cunning predators have never faultered through the Cenozoic and remain the most abundant predators in any given ecosystem they inhabit.  Of the four families of raptors present during the Late Cretaceous, the Unenlagines, Velociraptorines, Microraptorines, and Dromaeosaurines, only the first two have survived to the present day in a recognizable form.  They can be found all continents accept Australia and Antarctica.

(top - bottom, left -right)
Velociraptorines:
Hyperaptor (Demons, 2 species):  The fastest land animals, capable of speed bursts up to 65 mph.  Found usually in pairs, they can be found across the Northern Hemisphere where they frequent open areas.  The prey primarily on small game.  The hand streamers of males become hyperelongated during breeding season.  The largest species grows to 6 feet  (2m).
Neoraptor (Raptors, at least 8 species):  Found across Eurasia these are the typical "raptors".  Most species live in small family groups.  The largest species grows to 8 feet ( 2.5 m).
Terranychus (Raptors, 3 species):  The most powerful and dangerous raptors, these solitary predators can be found throughout the Americas and east Asia.  The largest species grows to 10 feet (3 m).
Retroraptor (Raptors, at least 5 species):  Named for their bizarre cranial crests, which often sport peculiar feathers.  Usually found in pairs, these small game hunters have strict territories and can be found throughout the Americas.  The largest species grows to 8 feet (2.5 m).
Unenlagines:
Corvuraptor (Corvutors, at least 4 species):  These two genera are probably direct descendents of Rahonavis.  Capable of limited flight, they prey on small game and scavenge.  This genus can be found throughout Africa, Madagascar, and southern Asia.
Egrettaraptor (Corvutors, at least 3 species):  Same info as previous genus, but found only in Africa and Madagascar.  Also preys mainly on fish.

Gigaraptorids:  Appearing in the fossil record during the late Miocene, the Gigaraptorids are the Saurocene's largest top predators in the Northern Hemisphere, even larger than the biggest Neotyrannosaurs.  They are probably descended from the Dromaeosaurines and their removal from the Deinonychosaurids is somewhat controversial.  Their inner toe is no longer hyperdextile, and the functional fingers have been reduced to just two.  The single genus, Gigaraptor, contains mostly modest sized species, but also a few monsters that grow to 45 feet (15 m) in length.  they are big game hunters that normal travel in small family groups.  They are surprisingly intelligent for such a large creature.  Their jaws and teeth are relatively delicate, so it's primarily their claws that dispatch large game.


Up next: Don't know yet, maybe some more raptors, maybe some marine dinos, maybe both!

[TheAllosaur]

Wow! Very cool!

[Jetoar]

Very nice, I like themes of speculative evolution  .

[Yutyrannus]

Anything new coming? Spinosaurs maybe (in case you haven't noticed, I really like Spinosaurs)?

[Brontozaurus]

Why aren't there any dromaeosaurids in Australia? Fossil teeth show that they existed here in real life, why haven't they survived?

[ZoPteryx]

Why aren't there any dromaeosaurids in Australia? Fossil teeth show that they existed here in real life, why haven't they survived?

Excellent point that I forgot to mention.  The only deinonychosaurs present in Australia by the Paleocene were Unenlagines, these were quite successful for a time but stayed relatively conservative in morphology (ie: fish-eaters).  As Australia dried out in the Quaternary, the raptors became more restricted in range and many had to become exceptionally specialized to compete with Australia's other fish eaters (crocs, spinosaurs, etc).  Then, in the late late Pliocene, a new group of fish eaters arrived in Australia, the "Sun-Herons" (the Saurocene's equivalent of herons and egrets).  These not only displaced the continent's true herons, but also apparently outcompeted the unenlagines into extinction. This appears to have all occurred quite rapidly, with no traces of Australian deinonychosaurs past the early Pleistocene.


And now, by popular demand, the spinosaurs!!!

Spinosaurids:   While there are no latest Cretaceous spinosaur remains known, Paleocene, Eoecene, and Oligocene spinosaur fossils are quite common in South America, Africa, Eurasia, and Australia.  During this time they apparently became quite diverse, with a wide variety of bizarre skull anatomies.  Past the Oligocene, however, they decline sharply until only spinosaurines are left in South America and baryonychines in Australia.  In South America, the spinosaurines maintain a conservative morphology and stay relatively inconspicuous (in an environmental sense, some were physically enormous!).  Today only a single species remains, but it is quite successful thanks to the Amazon River.  It was a different story in Australia.  The baryonychines quickly gave rise to a variety of bizarre lineages (collectively called the Ozspinosaurines), including abelisaur-mimics (true abelisaurs died out in Australia by the Eocene), mollusc-eaters with walrus-like tusks, mud-probers, saw-snouted forms, and many others.  Competition with the eventually doomed Neovenatorids prevented them from seizing the top predator niche however.  They even spread out of Australia, briefly recolonizing southern Asia during the Miocene.  Ultimately though, the drying out of the island continent and competition from an increasingly diverse array of crocodilians led to the extinction of all but 3 varieites, two genera in the saw-snouted group and one more typical looking genus.  All living spinosaurids have unusually long necks and tails, a trait that seems to have been aquired idependently in both main groups.

(top-bottom, left-right)
Spinosaurines:
Ardeaspinax (River Dragon, 1 species): The sole surviving spinosaurine, A. magnifiscens, can be found near large bodies of water from the central South America to southeastern North America.  Growing up to 55 feet (18 m) in length, it feeds primarily on fish and other aquatic game, but it will not hesitate to take any small creatures that come too close.  Males can be distinguished from females by their larger cranial crests.  They hold strict territories, but during breeding season the males' boundaries dissolve and they wander in search of females.  Females defend their nests, but the young are independent shortly after hatching.
Ozspinosaurines:
Pristiophorusaurus (Sawsnouts, 2 species):  The peculiar Sawsnouts can be found throughout northern Australia as well as a few islands further north.  Like sawfish, they use the outward projecting teeth of their upperjaw to dissable fish.  The teeth in the lower jaw are normal.  P. kakaduensis grows larger, up to 25 feet (8 m), and has a straight snout which it uses to fish in deeper water.  P. brevirostris growths of to 15 feet (5 m) and uses its upturned snout and a shorter lower jaw to fish in shallower water.
Spatullasaurus (Spooner, 1 species):  Restricted to northern Australia, S. elegans is a relatively small (to 12 feet (4 m)) species is quite common in marshy areas.  It uses the sensitive spoon-shaped tip of it upper and lower jaw to search for small aquatic organisms among vegetation.  Its teeth are slender and act a strainer.  Both this and the previous genus mate for life, take excellent care of their young, and are also unusual for their long toes and highly retracted nostrils. 
Microbaryonyx (Microspino, 1 species):  Found through most of the Lesser Sundas, M. insularis is a 9 foot (3 m) long generalist small game predator that exhibits a wide range of color and size variation.  Capable swimmers, there is gentic crossover between all populations.  Reports from coastal Queensland are probably of wandering strays.  Little is known of its behavior or breeding habits.