RANDOM THOUGHTS #272
Steve Cole ponders a few things about dinosaurs he thought he would share. This is by no means a systematic or even organized list, but it is a lot of things most people don't realize.
1. Most of what we "know" is a really a collection of guesses (that hold water) by large numbers of scientists. Somebody proposes an idea and if a lot of other scientists think it's probably right then it moves into the "fact" category. Actual hard "prove it in court" facts are few and far between. We know from the bones that a T-rex was 40 feet long, but there is a lot of dispute about whether those bones supported five, six, or eight tons of body. What we "know" changes over time. When I went to school in the 50s and 60s, we all "knew" that dinosaurs were stupid, slow, and cold-blooded. Now, we "know" that lots of dinosaurs were smart, fast, and warm-blooded.
2. There is no "Dinosaur Board" which rules on what is and what is not a fact; there is no "Dinosaur Election" wherein scientists vote what is and isn't a fact. There is only an ever-flowing consensus of a lot of opinions. What makes it worse is that dinosaur scientists are not in the habit of starting sentences with "My own theory is..." but instead just state their own theory as an established fact. There is the ICZN, which controls animal names so that no two scientists use the same name for different critters. (One dinosaur scientist had to add a letter to the name he picked for his discovery because another scientist had used that name for a beetle.) Often, a dinosaur gets a name based on one bone or one tooth. Sometimes, one scientist finds part of a dinosaur and another scientist finds a different part of another individual of that species, and nobody realizes that the two are the same until somebody finds another specimen which includes overlapping parts of both. The earliest one named becomes the official name. China doesn't recognize non-Chinese names and is constantly giving new names to well-known species. But at least half of dinosaurs are known from a single individual and usually even that is not complete.
3. Lots of things that people think are dinosaurs really aren't. Pterodactyls, plesiosaurs, pliosaurs, mososaurs, turtles, coelacanth fish, and alligators are sometimes called dinosaurs, but they're separate groups of unrelated animals.
4. One of the most important questions (which cannot be answered) is what the air was like during the dinosaur era. Most scientists think that the oxygen content was higher (up to 30%) than it is now (about 21%). Evidence for this is questionable. Air pockets in amber may or may not reflect original air, and calculations based on animal size and activity start with information that cannot be accurately ascertained.
5. The dinosaurs occupied three consecutive but very different time periods of Earth's history. In the oldest (Triassic) the dinosaurs were just one of several kinds of animals fighting for domination. The Jurassic was a very wet lush jungle environment. The Cretaceous was the last period and was much dryer. T-Rex was one of the last dinosaur species and is closer to us in time than to Stegosaurus, the one with the triangular plates down his back. (Speaking of Stegosaurus, at least one scientist originally thought that the triangular plates were horizontal and that the dino could glide from high places.)
6. We all know that a big rock fell out of the sky, landed in Mexico, and killed the dinosaurs 65 million years ago (i.e., the extinction level event). Except maybe that didn't really do it. The Deccan volcanoes in Indian went off for a few million years and really messed up the planet. Maybe the big rock caused the volcanoes, or maybe the big rock fell as the last of the volcano-ruined dinosaurs were trying to stay alive one more day. The big rock (Chixalub Crater) really messed up North America (which was covered in a shower of red-hot rocks and burned to the ground) but that didn't kill dinosaurs in Asia, Africa, and the random smattering of islands that was Europe. Any dinosaurs there had to have died from either a cometary winter type event or from those volcanoes in India.
7. Speaking of extinction events, the one at the end of the Cretaceous (the dino killing rock from the sky one 65 million years ago) was just the last of at least five. The End of the Permian extinction event was the worst, and allowed the dinosaurs to rise up and take over from (wait for it) the mammals that ruled before the dinosaurs. The Triassic and Jurassic both ended in major extinction events. Some of these may have been caused by big meteor impacts, but some may have been caused by supernova stars that exploded and killed most of life on Earth.
8. A lot of dinosaur research goes into figuring out the family try of the dinosaurs. Not long after dinosaurs first appeared in South America 235 million years ago, the tribe split into the two groups. The lizard-hipped group includes all of the meat eaters, the birds, the sauropods (Brontosaurus and so forth), and the pro-sauropods (which are kinda halfway between the meat eaters and the brontocritters (which split into four types that nobody can make sense of). The bird-hipped dinosaurs (which are not the ancestor of birds) included the iguanodons (which evolved into duckbills in the Jurassic and crested duckbills in the Cretaceous), the stegosaurs of the Jurassic which were the ancestors of the armored ankylosaurs of the Cretaceous, the various horn-faced dinosaurs leading to the final species (Triceratops), the boneheads, and a few smaller groups.
9. Fossil bones are not the only thing we have to go on. We have trackways (which can in theory give some idea of animal speed, even if no one knows if the speed of that dinosaur on that day was his maximum). We also have coprolites (fossil dino dung) which give some idea of what they ate (although connecting any given item to a species of dinosaur is hard to do). We have "skin impressions" (sort of like fossils) and "dinosaur mummies" (the entire dinosaur turned into stone, which provides only very limited detail about internal organs).
10. The names non-scientists know dinosaurs by are in fact the genera (general) name, not the species (specific) name. Consider that lions, tigers, jaguars, leopards, and cougars are all "panthera" while lions are "panther leo" and tigers are "panthera tigris." Stegosaurus, Allosaurus, Brontosaurus, Triceratops, and Tyrannosaurus are all genera names, not species names. While we're mentioning lions and tigers, the way scientists evaluate dinosaur skeletons is limited by the fact nobody has seen a living dinosaur (other than a bird, which is a dinosaur descendant). Let's say you gave a dinosaur scientist four skeletons (male tiger, female tiger, male lion, female lion). The scientist would not be able to see the lion's mane or the tiger's stripes and could go only by the bones. Evaluating the four skeletons, a modern scientist would 90% of the time put the two females in one species and the two males in the other, all four being in the same genera.
1. Most of what we "know" is a really a collection of guesses (that hold water) by large numbers of scientists. Somebody proposes an idea and if a lot of other scientists think it's probably right then it moves into the "fact" category. Actual hard "prove it in court" facts are few and far between. We know from the bones that a T-rex was 40 feet long, but there is a lot of dispute about whether those bones supported five, six, or eight tons of body. What we "know" changes over time. When I went to school in the 50s and 60s, we all "knew" that dinosaurs were stupid, slow, and cold-blooded. Now, we "know" that lots of dinosaurs were smart, fast, and warm-blooded.
2. There is no "Dinosaur Board" which rules on what is and what is not a fact; there is no "Dinosaur Election" wherein scientists vote what is and isn't a fact. There is only an ever-flowing consensus of a lot of opinions. What makes it worse is that dinosaur scientists are not in the habit of starting sentences with "My own theory is..." but instead just state their own theory as an established fact. There is the ICZN, which controls animal names so that no two scientists use the same name for different critters. (One dinosaur scientist had to add a letter to the name he picked for his discovery because another scientist had used that name for a beetle.) Often, a dinosaur gets a name based on one bone or one tooth. Sometimes, one scientist finds part of a dinosaur and another scientist finds a different part of another individual of that species, and nobody realizes that the two are the same until somebody finds another specimen which includes overlapping parts of both. The earliest one named becomes the official name. China doesn't recognize non-Chinese names and is constantly giving new names to well-known species. But at least half of dinosaurs are known from a single individual and usually even that is not complete.
3. Lots of things that people think are dinosaurs really aren't. Pterodactyls, plesiosaurs, pliosaurs, mososaurs, turtles, coelacanth fish, and alligators are sometimes called dinosaurs, but they're separate groups of unrelated animals.
4. One of the most important questions (which cannot be answered) is what the air was like during the dinosaur era. Most scientists think that the oxygen content was higher (up to 30%) than it is now (about 21%). Evidence for this is questionable. Air pockets in amber may or may not reflect original air, and calculations based on animal size and activity start with information that cannot be accurately ascertained.
5. The dinosaurs occupied three consecutive but very different time periods of Earth's history. In the oldest (Triassic) the dinosaurs were just one of several kinds of animals fighting for domination. The Jurassic was a very wet lush jungle environment. The Cretaceous was the last period and was much dryer. T-Rex was one of the last dinosaur species and is closer to us in time than to Stegosaurus, the one with the triangular plates down his back. (Speaking of Stegosaurus, at least one scientist originally thought that the triangular plates were horizontal and that the dino could glide from high places.)
6. We all know that a big rock fell out of the sky, landed in Mexico, and killed the dinosaurs 65 million years ago (i.e., the extinction level event). Except maybe that didn't really do it. The Deccan volcanoes in Indian went off for a few million years and really messed up the planet. Maybe the big rock caused the volcanoes, or maybe the big rock fell as the last of the volcano-ruined dinosaurs were trying to stay alive one more day. The big rock (Chixalub Crater) really messed up North America (which was covered in a shower of red-hot rocks and burned to the ground) but that didn't kill dinosaurs in Asia, Africa, and the random smattering of islands that was Europe. Any dinosaurs there had to have died from either a cometary winter type event or from those volcanoes in India.
7. Speaking of extinction events, the one at the end of the Cretaceous (the dino killing rock from the sky one 65 million years ago) was just the last of at least five. The End of the Permian extinction event was the worst, and allowed the dinosaurs to rise up and take over from (wait for it) the mammals that ruled before the dinosaurs. The Triassic and Jurassic both ended in major extinction events. Some of these may have been caused by big meteor impacts, but some may have been caused by supernova stars that exploded and killed most of life on Earth.
8. A lot of dinosaur research goes into figuring out the family try of the dinosaurs. Not long after dinosaurs first appeared in South America 235 million years ago, the tribe split into the two groups. The lizard-hipped group includes all of the meat eaters, the birds, the sauropods (Brontosaurus and so forth), and the pro-sauropods (which are kinda halfway between the meat eaters and the brontocritters (which split into four types that nobody can make sense of). The bird-hipped dinosaurs (which are not the ancestor of birds) included the iguanodons (which evolved into duckbills in the Jurassic and crested duckbills in the Cretaceous), the stegosaurs of the Jurassic which were the ancestors of the armored ankylosaurs of the Cretaceous, the various horn-faced dinosaurs leading to the final species (Triceratops), the boneheads, and a few smaller groups.
9. Fossil bones are not the only thing we have to go on. We have trackways (which can in theory give some idea of animal speed, even if no one knows if the speed of that dinosaur on that day was his maximum). We also have coprolites (fossil dino dung) which give some idea of what they ate (although connecting any given item to a species of dinosaur is hard to do). We have "skin impressions" (sort of like fossils) and "dinosaur mummies" (the entire dinosaur turned into stone, which provides only very limited detail about internal organs).
10. The names non-scientists know dinosaurs by are in fact the genera (general) name, not the species (specific) name. Consider that lions, tigers, jaguars, leopards, and cougars are all "panthera" while lions are "panther leo" and tigers are "panthera tigris." Stegosaurus, Allosaurus, Brontosaurus, Triceratops, and Tyrannosaurus are all genera names, not species names. While we're mentioning lions and tigers, the way scientists evaluate dinosaur skeletons is limited by the fact nobody has seen a living dinosaur (other than a bird, which is a dinosaur descendant). Let's say you gave a dinosaur scientist four skeletons (male tiger, female tiger, male lion, female lion). The scientist would not be able to see the lion's mane or the tiger's stripes and could go only by the bones. Evaluating the four skeletons, a modern scientist would 90% of the time put the two females in one species and the two males in the other, all four being in the same genera.
posted by Federation Commander at 4:08 AM
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