1. How Much Do You Really Know About Dinosaurs?
Sure, everyone knows that dinosaurs were really big, and that some of
them had feathers, and that they all went extinct 65 million years ago.
But how deep does your knowledge of dinosaurs, and the Mesozoic Era,
really go? On the following slides, you'll discover 10 basic facts about
dinosaurs that every scientifically literate adult (and grade-schooler)
should know.
2. Dinosaurs Weren't the First Reptiles to Rule the Earth.
The first dinosaurs evolved during the middle to late Triassic
period, about 230 million years ago, in the part of the supercontinent
of Pangea that now corresponds to South America. Before then, the
dominant land reptiles were archosaurs ("ruling lizards"), therapsids ("mammal-like reptiles") and pelycosaurs (typified by Dimetrodon), and for 20 million or so years after dinosaurs evolved the most fearsome reptiles on earth were prehistoric crocodiles. It was only at the beginning of the Jurassic period, 200 million years ago, that dinosaurs truly began their rise to dominance.
3. Dinosaurs Prospered for Over 150 Million Years.
With our 100-year-max life spans, human beings aren't well adapted to
understanding "deep time," as geologists call it. To put things in
perspective: modern humans have only existed for a few hundred thousand
years, and human civilization only got started about 10,000 years ago,
mere blinks of the eye by Jurassic time scales. Everyone talks about how
dramatically (and irrevocably) the dinosaurs went extinct, but judging
by the whopping 165 million years they managed to survive, they may have
been the most successful vertebrate animals ever to colonize the earth!
4. The Dinosaur Kingdom Comprised Two Main Branches.
You'd think it would be most logical to divide dinosaurs into herbivores
(plant eaters) and carnivores (meat eaters), but paleontologists see
things differently, distinguishing between saurischian ("lizard-hipped") and ornithischian
("bird-hipped") dinosaurs. Saurischian dinosaurs include carnivorous
theropods and herbivorous sauropods and prosauropods, while
ornithischians account for the remainder of plant eaters, including
hadrosaurs, ornithopods and ceratopsians, among other dinosaur types. Oddly enough, birds evolved from "lizard-hipped," rather than "bird-hipped," dinosaurs!
5. Dinosaurs (Almost Certainly) Evolved into Birds.
Not every paleontologist is convinced, and there are some alternate
(albeit not widely accepted) theories. But the bulk of the evidence
points to modern birds having evolved from small, feathered, theropod dinosaurs
during the late Jurassic and Cretaceous periods. Bear in mind, though,
that this evolutionary process may have happened more than once, and
that there were definitely some "dead ends" along the way (witness the
tiny, feathered, four-winged Microraptor,
which has left no living descendants). In fact, if you look at the tree
of life cladistically--that is, according to shared characteristics and
evolutionary relationships--it's completely appropriate to refer to
modern birds as dinosaurs.
6. Some Dinosaurs Were Warm-Blooded.
Modern reptiles like turtles and crocodiles are cold-blooded, or
"ectothermic," meaning they need to rely on the environment to maintain
their internal body temperatures--while modern mammals and birds are
warm-blooded, or "endothermic," possessing active, heat-producing
metabolisms that maintain a constant internal body temperature, no
matter the external conditions. There's a solid case to be made that at
least some meat-eating dinosaurs--and even a few ornithopods--must have been endothermic,
since it's hard to imagine an active lifestyle being fueled by a
cold-blooded metabolism. (On the other hand, it's unlikely that giant
dinosaurs like Argentinosaurus were warm-blooded, since they would have cooked themselves from the inside out.)
7. The Vast Majority of Dinosaurs Were Plant Eaters.
Fierce carnivores like Tyrannosaurus Rex and Giganotosaurus
get all the press, but it's a fact of nature that the meat-eating "apex
predators" of any given ecosystem are tiny in number compared to the
plant-eating animals on which they feed (and which themselves rely on
the vast amounts of vegetation needed to sustain such large
populations). By analogy with modern ecosystems in Africa and Asia,
herbivorous hadrosaurs, ornithopods and (to a lesser extent) sauropods probably roamed the world's continents in vast herds, hunted by sparser packs of large, small and medium-sized theropods.
8. Not All Dinosaurs Were Equally Dumb.
It's true, some plant-eating dinosaurs (like Stegosaurus)
had brains so tiny compared to the rest of their bodies that they must
have been only a little bit smarter than giant ferns. But meat-eating
dinosaurs large and small, ranging from Troodon
to T. Rex, possessed more respectable amounts of grey matter compared
to their body size, since they required better-than-average sight,
smell, agility and coordination to reliably hunt down prey.
9. Dinosaurs Lived at the Same Time as Mammals.
Many people mistakenly believe that mammals "succeeded" the dinosaurs 65
million years ago, appearing everywhere, all at once, to occupy the
ecological niches rendered vacant by the K/T Extinction Event. The fact is, though, that early mammals
lived alongside sauropods, hadrosaurs, and tyrannosaurs (usually high
up in trees, out of harm's way) for most of the Mesozoic Era, and in
fact they evolved at around the same time (the late Triassic period,
from a population of therapsid reptiles). Most of these early furballs
were about the size of mice and shrews, but a few (like the
dinosaur-eating Repenomamus) grew to respectable sizes of 50 pounds or so.
10. Pterosaurs and Marine Reptiles Weren't Technically Dinosaurs.
It may seem like nitpicking, but the word "dinosaur" applies only to
land-dwelling reptiles possessing a specific hip and leg structure,
among other anatomical characteristics; here's an article explaining the
scientific definition of a dinosaur. As large and impressive as some genera (such as Quetzalcoatlus and Liopleurodon) were, flying pterosaurs and swimming plesiosaurs, ichthyosaurs and mosasaurs
weren't dinosaurs at all--and some of them weren't even all that
closely related to dinosaurs, save for the fact that they're also
classified as reptiles.
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