RANDOM THOUGHTS #278

Steve Cole ponders thoughts on dinosaurs:
       

1. The Triassic was the first (oldest) of the three dinosaur ages (250 to 200 million years ago). During this period, dinosaurs first appeared, but they hadn't taken over the planet until the end of it. Lots of other animals, families that lost the war for Earth to the dinos, are also found.
    

2. The Jurassic is the middle of the dinosaur era (200 to 140 million years ago). It was a very wet, lush, green time for Earth. This period includes stegosaurus, allosaurus, and the duckbills. It also includes a chicken-sized predator Coelophysis who was the ancestor of Tyrannosaurus.
  

3. The Cretaceous is the last of the three dinosaur eras (starting 140 million years ago), and ended 65 million  years ago when the big rock hit Mexico and the Deccan mega-volcanoes messed up the whole planet. This period includes most of the dinosaurs we know, including T-rex, raptors, Triceratops, Ankylosaurus (armored tanks on legs), and the crested duckbills.
   

4. Dimetrodon was probably in your toy dinosaur set. It looks like a lizard with a huge fin on its back (which is called a sail). It was also in the original Journey to the Center of the Earth movie. Funny thing is, Dimetrodon was not a dinosaur, but a mammal-like reptile that died out in the Permian, long before the first dinosaur was born. We humans actually have Dimetrodon in our family tree. Say hello to your great-great-great-great-great-great-grandpa.
   

5. Spinosaurus was as big as a T-rex but had a huge sail on his back like the Dimetrodon (but was not related). Spinosaurus was found in Morocco and Egypt. The first one found was accidentally destroyed when the US bombed (1944) the Berlin museum that housed his bones. About 15 years ago I was reading Dinolist and asked the dinosaur scientists "You know where he's from. Why not go there and drive around until you find one sticking out of a rock?" Many laughed at my naivete but one of them (perhaps not because of what I said) actually did just that and found another one (and a lot of other new dinosaurs). I count this as my contribution to dinosaur paleontology. Spinosaur teeth are a unique shape with unique serrations on the edges, and lots of related "spinosaurids" have the same teeth of various sizes. Since teeth are the most common fossils found, scientists have a pretty good idea of where these things wandered, including north Africa and Brazil.
        

6. Recently, scientists working in Mongolia found a bone bed containing a flock of Avimimus (bird-mimic), a kind of dinosaur from the branch of the meat-eaters that spawned birds. Bonebeds are great because you get partial skeletons (or whole skeletons) of a dozen individuals, in this case of the same species. Most dinosaur skeletons are found in a jumbled pile missing half or more of the pieces, and scientists have to guess about the missing bones from similar species. (For example, they found half of a tiger skeleton but could tell it was enough like a leopard that since they had a whole leopard skeleton they could guess the missing bits.) Bonebeds sometimes have complete skeletons laid out nose to tail (a bunch of dinosaurs died in one place), and sometimes have random jumbles of bones (a bunch of dinosaurs died somewhere else and their bones were washed into a big hole by the actions of a river).
       

7. Words mean things. The word "described" means (to dinosaur scientists) that someone wrote a scientific paper in a peer-review journal which gave lots of lots of details about known bones of some animal. In theory, anyone who finds a random bone checks every published "description" to see if his bone fits into a known critter before he publishes his own paper defining it as a new critter.
       

8. Tyrannosaurus, Brontosaurus, Triceratops, and Stegosaurus are not species (e.g., tiger) but genera (e.g., big cat). Tyrannosaurus rex is a species, as is Tyrannosaurus bator, the Asian cousin of T-rex. Many think that bator is actually in a separate genera, Tarbosaurus bator, but that argument is not yet settled.

        

9. On Earth today there are 6,199 different species of amphibians, 9,956 different species of birds, 30,000 different species of fish, 5,416 different species of mammals (about half of which are rodents), and 8,240 different species of reptiles. Consider that we know of less than a thousand species of dinosaurs and those cover a period of 170 million years. Assuming a species lasts about four million years, that means at best we know of 25 dinosaur species alive at any given time. Even compared to the 2500 "greater mammals" alive today, you can see that our picture of the fossil record is murky at best. It's more likely that you will win the lottery than become a fossil for some scientist of a new species to study 25 million years from now.

        

10. It is looking more and more like the extinction at the end of the Permian (before the Triassic, the extinction that destroyed the proto-mammals and opened the door for dinosaurs) was caused by massive mega-volcanoes in Siberia. These erupted for a million years, covered most of Siberia in lava, and totally wrecked the environment.