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L is for Living Relatives

Dinosaurs could see in color. The EPB-living relative theory says so. Picture by Sergey Krasovskiy.

EPB. Remember those letters when you think of dinosaurs. They’re hard words–extant phylogenetic bracket–which I will define shortly. But they are like a magic wand for paleontologists and paleobiologists. EPB lets scientists looking at fossil bones, those 100-million-year old rocks, tell what kind of muscles they had, whether their blood vessels were strong, and whether they could see in color. Scientists can tell all sorts of things about the soft tissues inside those bones because they can compare them to the closest Living Relative. (I was going to include this under letter E, but I had to talk about extinction, so I’m slipping it in here under L. By inference, which is how EPB works.)

EPB: Big Words, Brilliant Idea

Let’s break this acronym down. Extant is the opposite of extinct, so that refers to something living, in particular a species or group of animals (remember C for Clade). Phylogenetic is a mouthful. Phylo means group and genetic refers to a group. Bracket also means group.

extant (living) + phylogenetic (group evolutionary tree) + bracket (group) = EPB

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K is for the K-Pg Boundary

An image from a simple Google search for “dinosaurs.” From earthspacecircle.

You probably have heard about the asteroid. Big BOOM. You can’t really look at a generic picture of dinosaurs on the Interwebs without seeing them fleeing from hellfire and brimstone. But the asteroid involves two parts. The latter part is what happened after the BOOM, and I’ll tell that story toward the end of the alphabet. You’ll have to guess what letter.

But the first part of the scientific part of the story is how did they know? How could scientists tell that there was a big giant asteroid that eliminated all the dinosaurs? Maybe they could figure out from the fossil record that the dinosaurs disappeared. But how did they know it was caused by an extraterrestrial event? Particularly when the impact crater was, as it turns out, deep under water?

They didn’t know at first. The scientific method triumphed in the end. And fathers and sons.

The Old Ideas of Catastrophe

Before 1980, paleontologists did know that dinosaurs disappeared, around 64 million years ago, in fact. The end of the Cretaceous period was set at 64–and not 100 or 150–precisely because that was when all the dinosaur fossils disappeared.  It was somewhat handy that it happened during a chalky geological period since that made it easy to spot on the sides of cliffs.

The layers of geology. White is the KT boundary. Graphic from geowyoth.
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J is for Jurassic

Jurassic Park OG Velociraptor, photo from Filmexperience.net.

Scientists are actually preoccupied with accomplishment… focused on whether they can do something. They never stop to ask if they should do something.

Ian Malcolm, Jurassic Park

Chances are that you have seen Jurassic Park or one of its sequels. Chances are that you found some part of it exciting. Perhaps you found other parts to strain credulity. That’s ok. The Jurassic Park franchise is not entirely accurate. At first, I thought it was too pandering, too dumbed-down to create realistic dinosaurs. But I was wrong. At least about the relative realism of the dinosaurs.

No, they weren’t exactly Jurassic. The dinosaurs named and depicted did not completely act like their namesakes should have acted. The velociraptor and the dilophosaurus in the first movie were particularly off. But Spielberg got a lot of other things right. And he made dinosaurs really popular, which probably led to more people studying dinosaurs and more funding for dinosaur studies. Well played, Mr. Spielberg, well played.

Not Especially Jurassic

So what exactly is Jurassic? It’s a geological time period. Geologic time is divided up into eras and periods, chiefly to provide names for future geologists and paleontologists to memorize. Also, it’s shorter to write Jurassic than it is to write 200 to 145 million years ago. The entire era of the dinosaurs is called the Mesozoic, which means the middle (meso) era that had animal fossils (zoic), as opposed to the Paleozoic, which means older time of fossils, and the Cenozoic, which is the recent era, i.e. now.

The Mesozoic also had three divisions: Triassic, Jurassic, and Cretaceous. Triassic was called that because the Germans wanted that time period to have another three categories that they called the Trias. Kind of like the basic rule of magic; if you say a thing three times, then it becomes real.

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