Let's talk about lesser-known prehistoric critters.

That is, stuff other than T. Rex, Smilodon fatalis (other sabertoothed cats are fine), dromaeosaurs, etc... Any time period is fine...and don't worry about being lazy on italics. Quotes taken from Wikipedia unless otherwise stated.


"Teratornis merriami (Miller, 1909). This is by far the best-known species. Over a hundred specimens have been found, mostly from La Brea Tar Pits. It stood about 75cm tall with estimated wingspan of perhaps 3.5 to 3.8 metres, and weighted about 15kg; making it slightly bigger than extant condors. It became extinct at the end of the Pleistocene, some 10, 000 years ago. Teratornis is Greek for 'monster bird'." Pictured here briefly on the ground.


Phorusrhacos longissimus was roughly equivalent to Diatryma in size, but it was a simple case of parallel evolution. The two did not share a common ancestor. Phorusrhacos evolved much later-the earliest members of the genus date to the Miocene, about 27 million years ago. Phorusrhacos evolved to take advantage of the wide open South American pampas (steppe-like terrain). They quickly became the dominant predators in this biome.

When North and South America were linked again via the Central American land bridge, saber-toothed cats moved down into South America, displacing Phorusrhacos longissimus from the top of the food chain. However, the cats didn't drive it into extinction. Phorusrhacos stayed on as a lesser predator and scavenger. It is thought that a signifcant number of the birds gradually moved north, eventually diverging enough from their southern cousins to become the Titanis genus of terror birds found in Texas and Florida. Humanity finally killed off Phorusrhacos around 15,000-10,000 years ago.


"Argentavis magnificens (Campbell & Tonni, 1980). A partial skeleton of this enormous teratorn was found from La Pampa, Argentina. It is the oldest known teratorn, dating to late Miocene, about 6 to 8 million years ago, and one of the very few teratorn finds in South America. Initial discovery included portions of the skull, incomplete humerus and several other wing bones. Even conservative estimates put its wingspan between 6 and 7 metres, and it may have been as much as 8 metres. Weight of the bird was estimated to have been around 80kg. Estimated weight and wing area rival those of the largest Pterosaurs."


"Diatrymas consist of four extinct species of large flightless birds. Fossils aged 65 to 55 million years (Paleocene to Eocene) have been found in North America, France, and Germany.

The birds stood over two metres tall, and had unusually large skulls in proportion to their bodies (nearly 50 cm long, including a beak over 20 cm long.) They weighed about 100 kg. Diatrymas bear a superficial resemblance to phorusrhacids, but there is not a close relationship.

There has been debate about whether diatrymas were carnivores or herbivores, using their large beaks for cracking nuts, as parrots do. Lawrence Wittmer and Kenneth Rose (1991) concluded from an analysis of the biomechanics of the jaw that the birds were carnivorous, hunting and eating small mammals."

The taxonomy has recently shifted to Gastornis, but that doesn't sound nearly as cool.



Tylosaurus, a Late Cretaceous mosasaur-related to both modern monitor lizards and snakes, if I'm not mistaken.


Carcharodontosaurus saharicus-slightly outclasses T. Rex in terms of length. Believed to be the same species as the South American Giganotosaurus.


Spinosaurus aegypticus-Jurassic Park 3 may have put it in the spotlight, but since the best Spinosaurus skeleton ever found was destroyed in the WWII bombing of Munich, most of our knowledge consists of educated guesses and limited data gathered before the bones were destroyed. In case you didn't know, the sail regulates body heat.



Sarcosuchus-50 feet of gigantic, gharial-esque crocodile versus Suchomimus, an Early Cretaceous spinosaurid.



Liopleurodon, a Jurassic pliosaur that compares quite favorably in size with many whales.



Helicoprion, a form of bizarre primitive shark. The only major thing scientists have found is that strange jaw with its spiraling teeth.

Love the Argentavis Magnificens! Some crow! :D

Love wooly rhinos.

And yeah, Argentavis magnificens really deserves the name.

Kick for paleo-ornithology!

I think that was the title, and it had such creepy stuff! Seven foot sea scorpions and giant spiders. How did people stand it? ;)

...but I've seen that show-wasn't half bad. Remember Arthropleura, the 8-foot millipede?

Yech!

Really though, those critters are pretty amazing.

does anyone have a legit theory on why prehistoric animals are so gigantic or is there some explanation? I have often wondered why
the dino's got so large. I am awestruck by sabertooth tigers etc.,

Is it simply that these giants are the ones that get attention?

I was reading about ligers and tigons...how one of these is giagantic.

Just imagining those birds gives me chills. Destroyed by humans...
excellent...I wonder what that felt like to fight one of these giant
birds.

...I seem to remember hearing that the atmospheric oxygen content was slightly higher during the Mesozoic era (not as high as the Carboniferous), which might explain the freakish size of some of the sauropods, and I think being warm-blooded rather than cold-blooded helped account for the size of the general larger dinosaurs as well.

But the small guys don't get enough attention-the human "bigger is better" mentality. Velociraptor, despite the popular myth promoted by Jurassic Park (their raptors were somewhere between Deinonychus and Utahraptor in terms of size) was pretty small.


Coelophysis was small too, a little shorter than an adult human, and it was the common ancestor for the vast majority of the larger theropods.


Troodon was small, and had a freakishly large brain for its size. Scientists speculate that had the KT event not happened, Troodon or a similar species would have evolved to become the Earth's sentient species.

Ornithomimosaurs were medium sized, and were the fastest things on the ground. These boys (of which I don't have a picture) could leave any dromaeosaur in the dust.
***

Same goes for the mammals, birds, and Cenozoic reptiles-there are plenty of interesting small-to-medium ones (Miacis, the common ancestor for dogs and cats springs to mind, as does Eohippus and Phorosrhacos' chicken-sized ancestor), but it's the dramatic ones that get our attention. Mammoths, mastodons, wooly rhinos, terror birds, teratorns, Haast's eagles over in New Zealand, saber-toothed cats, short-faced bears, Megalania priscea from Pleistocene Australia, North American lions, Rhamphosuchus lurking in the swamps of Miocene India, etc... If any of these interest you, ask me tomorrow and I'll do some research-I love this stuff.

***
As to what it would be like to face Phorosrhacos' North American variant, imagine this:

It's summer in West Texas, 10,000 years ago. It's fucking HOT. You're tired. You've been hunting since dawn, because the whole damn tribe's hungry. Almost all the other men are doing the same-they left a few people to guard the women, children, aged, and infirm. You're looking for something, ANYTHING that you can bring back. Rabbit will do. Deer would be great. You'd even be willing to settle for an armadillo.

All of a sudden the wind shifts, and you can smell the blood and shit smell of a freshly killed animal. It's strong-there's a lot of blood, and almost as much shit. Something big is dead. If you can drive off whatever killed it, there's a lot of meat for the tribe there. You don't stop to go find another tribesman or two. Every minute you wait is more meat that the tribe needs going down something's gullet. So you heft your stone-headed club and start moving toward the smell. You'd been moving cautiously before-now you're like a ghost. Time passes slowly.

And then you see the deer. It's a big buck-enough meat to feed the tribe for a week. There are gaping wounds in the hindquarters, the forequarters, and the neck. Blood has sprayed everywhere, and there's a trail of blood and shit leading off a good ways. There's nothing standing over it. No sabertooth with fangs the size of your forearm, no jaguar, no lion. Whatever killed the buck must have heard you or smelled you and run off. You start to move toward the deer, and then you see a mottled flash burst out of the bushes. Time seems to slow. You can see the wide-spread talons, the breast-feathers coated in crimson. The great bloodstained beak opens in a screech of rage as the terror bird charges, and wet red scraps of deer flesh fall out. The mad yellow eyes are glaring at you, and the only thing you can do is hope you can get your club up in time to strike...

It is theorized that during the Carboniferous period, the oxygen content was close to if not above about 40 percent. This lead to a proliferation and dominance of invertebrate life, arthropods mostly, on land, and also possibly lead to them being so large, some growing as large as 20 feet long. The restriction of arthropods to smaller sizes than vertebrate animals is because of two factors, one is the lack of lung development in arthropods, and the second is because of the exoskeleton. The thing is that the exoskeleton isn't as limiting a factor as many people believe, but since air breathing arthropods only absorb oxygen straight from the air rather than suck it in, it was inefficient at best. This is but one theory for arthropod size differences between today and in the past.

Another interesting theory has to do with end of the Permian extinction, the most dramatic of all extinctions(95% of species at the time became extinct). The extinction, as far as they know, was only triggered through somewhat gradual climate change, the most dramatic effects were the drying of the land, a drought, and the plummeting of oxygen levels to possibly as low as 20% or lower. The interesting effect of this climate change was in the adaptation of species, namely reptiles, which branched off into two different other branches, Dinosauria and Mammalia. OK, less oxygen means either less activity, and possible extinction, or adaptation and survival. Dinosauria developed lungs that were two chambered, so during exhalation there was still fresh air contained within them so they can still extract oxygen from that air. This feature is still present in modern day birds, in fact, this adaptation may have made it easier for land bound Dinosauria to develop flight.

The second adaptation was in another group of reptiles that had some ribs disappear from their abdomens entirely, and the development of Diaphragms to allow their lungs to suck in far more air than was previously possible. These mammal like reptiles also had a somewhat odd ability of being able to lay on their sides, half turned, this may not seem significant, but look at a nursing Cat and you would see it plainly how this would make it easier for mammal like reptiles to develop mammary glands to nurse their young. Now try to imagine a lizard in the same position, you can't, they cannot physically be able to be put in such a position.

Now, another subject I wanted to bring up, the Troodon is a very interesting creature for various reasons. First, you mentioned the large brain for its size, comparable to modern birds if not primates. A few other interesting things about it were that is was both Omnivorous and it actually had an opposable thumb, if only partially evolved. In fact, given it was bi-pedal, had a large brain, and opposable thumbs, in addition to a varied diet, it seems to have almost all the features of a hominid species, except for the fact that it was not a mammal. If the climate on Earth was changing to be more hostile to Dinosaurs in general, as is theorized was happening before the asteroid struck, then perhaps the conditions were right, minus the asteroid, of course, for Troodon to have become the first sentient species to evolve on the planet. BTW: here is a picture of Troodon.

Pictures, then text. ;) The CGI image in the post you replied to was supposed to be a Troodon. You found a much more interesting picture, though. And I hadn't heard about the opposable thumb. That is extremely interesting.

I also hadn't heard much of anything beyond the broadest details about the things you mentioned paragraphs 2-3, so thank you for enlightening me. Although I'd always heard 90% extinction rate for the Permian extinction, not 95%-mind sharing where you got that statistic?

Also, I was aware of the Carboniferous, its freakish arthropods (I can never remember the species name of the most well-known giant dragonflies; Mega-something), and why they couldn't hit huge sizes, but thank you on behalf of the people who weren't.

I watched a Science or Discovery channel series that concentrated on what type of species existed BEFORE the Dinosaurs for once. They showed a Centapedal species that, at the time, was 20 feet long and could rear up its front section of its body to a full 6 or 7 feet. As for my estimation of the Permian Extinction, some books and sources say 95% others 90%, the only thing anyone can actually agree on is that it was an EXTREME extinction, not even the KT event can compare, even though the Permian extinction was less abrupt. I just used the higher estimation, its hard enough to figure out how many species actually became extinct, fossilization is a rare process, who knows how many species ACTUALLY existed back then, how many survived, and how many did not. Its a crapshoot at best, and 5% variance is actually a GOOD sign at how accurate they are getting.

By the way, I know about that Dragonfly species you are talking about, I forget the name too, but it had a wingspan of an Eagle, about 2 meters, thats freakin HUGE.

Didn't Moses have a few of these on the Ark? :P

and you should have seen her momma...

Thanks. And one of the phrases in that second article made me bust out laughing. Points if you can figure it out.

I think what the name of the bird means is funny.

:D

Wiwaxia


Charnia


Marella


Kimberella


Anomalocaris


Dickinsonia


Pikaia


[link:en.wikipedia.org/wiki/Tribrachidium|Tribrachidium