Thursday, October 25, 2007

Dimetrodon: NOT a dinosaur

Despite constantly being lumped in with T. rex and stegosaurus in the world of plastic dinosaurs - Dimetrodon was actually the top pre-dinosaur predator. Actually, it was the only predator around before the dinosaurs showed up - the first king of the food chain, and the first evidence we have of the formation of a land ecosystem.

This species ruled in the Permian Period – the time just before dinosaurs showed up that ended with history’s most massive known extinction. Discoveries from this period help answer the question “Where did dinosaurs come from?”

Dimetrodon were 7 to 14 feet long, weighed up to 600 pounds and had 4-foot tall fins on their backs. According to Dr. Bakker, you would not want to meet one in a dark alley – “If they were alive, they would look upon you as a food item.”

(c) Robert T. Bakker

Fearsome they may be, but few extinct species are as important than Dimetrodon – its existence represents a key step in earth history. Dimetrodon dominated its world, the largest meat-eater that had ever evolved up to the time. It was strong enough to kill any other land animal.

When Dimetrodon ruled, lizards hadn’t evolved yet, nor turtles, nor snakes. There weren’t any crocodiles, gators, frogs, salamanders, or even flowers. The only plants around were ferns, horsetails or other primitive conifer with dull green leaves.

Dimetrodon femur found by the team in Seymour, TX. Additional objects present for scale.

In fact, it's so old that Dimetrodon has a special spot in human evolution. The Texas Finback is located very close to the base of the mammalian family tree that includes all ‘possums, dogs, and cats, monkeys, apes and humans. So…you can put a portrait of the Texas Finback up on the mantel, next to Grandma and Grandpa.

This plaster jacket covers and protects an associated Dimetrodon skeleton found by the team in Seymour, TX. It has since been removed from the site and taken to the Museum for study.

"Where's the beef?"

There's a mystery paleontologists have been puzzling over for decades that's pretty well summed up by everyone's favorite Wendy's ad.

Dimetrodon vertebrae found at HMNS site; additional object present for scale.

The Permian Red Beds in North Texas have turned up hundreds of Dimetrodons - the top predator of the era - but only a few fossils of the plant eaters they would have munched on. Without evidence of enough meat for this species to survive, how did they flourish for so long?

Dimetrodon ribs found by HMNS team.

In other words, Where's the beef?

About 50 years ago, E.C. Ulson, UCLA, hypothesized that Dimetrodons didn't eat plant eaters very often - because they were eating sharks.

Xenacanthus sharks of the era were unlike anything we've seen today. While the front of this prehistoric shark resembles modern species, it's back was shaped like an eel, and it had a long, poisonous spine coming out of its head. Most importantly, these were freshwater sharks that lived in the shallow, swamp-like habitat that was also populated by Dimetrodon 290 million years ago.

Evidence found by the HMNS paleo dig team supports this theory. For example, the team has found lots of Xenacathus teeth and poison spines at the site - but comparatively few examples of Xenacanthus coprolite (or shark poop). If the teeth were lost in the act of eating something, there would be coprolite around to prove it. Instead, the team has found lots of chewed-up shark skull.

An example of coprolite found at the site.

Something was eating the Xenacanthus at this site. Dimetrodon is the only species in the same weight class.

So, mystery solved?

Regarding image use and copyright

The HMNS paleontology dig team is thrilled to bring you as many pictures as we can of what's happening this week in Seymour.

Please note that all drawings, illustrations and diagrams posted to this blog are (c) Robert T. Bakker. Educators are encouraged to download these images for use in their classrooms under the Fair Use guidelines of the U.S. Copyright Office.

All other photos and images are (c) Houston Museum of Natural Science.

Erin Blatzer, blog editor

Erin is a science geek with a communications degree that lucked into the world's best job - which is mainly composed of talking, writing and now, blogging about the amazing variety of cool stuff that happens at The Houston Museum of Natural Science every day.

She's twice narrowly escaped heat stoke while digging with the team in Seymour - and loved every minute. She also has experience handling snakes, eating bugs, transporting chickens, frogs and other live animals, and generally discovering how many fascinating stories there are to tell about the fine people she works with. She's excited to have the chance to help the team share their story with you this week, and hopes you'll visit the blog often to catch up on their exploits.

Chris Flis, Museum Team Member

Officially, Chris Flis is a site manager for The Woodlands Xploration Station, a satellite facility of The Houston Museum of Natural Science that houses more than 10 dinosaurs, an impressive collection of giant minerals, live bugs and much more - and he's a paleontologist at heart. He's been traveling to remote areas to find fossils since he was a kid, and has had the pleasure of digging into ancient history in Ireland, Nova Scotia, and England. His current research includes identifying and cataloging Eocene marine species present in fossil-bearing areas near College Station. With the Museum, he's dug extensively in Seymour, along with other pre-historic sites in Texas, as well as Kansas and the Morrison Formation in Wyoming. He's also an enthusiastic fossil photographer and many of his photos are featured in this blog.

Johnny Castillo, Volunteer Team Member

Johnny Castillo is a long-time volunteer with the Museum's paleontology department. He has dug mammalian fossils in Nebraska, spent three dig seasons working with the Museum on a Triceratops, and this is his fourth time digging with the team in Seymour. He's also dug in Stone City and High Island.
"I was no different than any other kid, I guess. The top three things I wanted to do was dig for dinosaurs, go into Egyptology - I thought it would be really neat to go to Egypt and dig for treasure - or drive an ice cream truck. Getting to eat all the ice cream you want - that's a big thing for a kid."
This week, Johnny is working on removing a plaster jacket full of Dimetrodon fin spines and vertebrae from the site, and looking for the bones that could be underneath.

Kimberly Beck, Teacher Team Member

"Every rock has a story to tell!"

Kimberly Beck is the Chemistry and Integrated Physics and Chemistry teacher at Seymour High School in Seymour, TX. She first worked with the HMNS dig program in 2007 as part of the Museum's field program for educators, in which teachers work on a real dig site in order to bring that experience and enthusiasm - as well as real fossils - back into their classrooms.

But let's let her tell it:

"I have been learning alongside the Museum's team ever since my first dig last summer. Now, I dig on the Brazos River in Knox County every chance I get and have found everything from Permian arthropod tracks to Pleistocene mammoth tusk. I love working outdoors in the dirt and am fascinated with the natural history, anatomy and physiology, and investigative nature that comes with studying fossils. Every rock has a story to tell!"

Students from Beck's class will visit the team on site this week, and you'll hear all about their experiences digging fossils right here.

Beck earned a Biology Degree from Texas Woman’s University, with a traineeship with NASA at Kennedy Space Center in Cape Canaveral, Florida.

David Temple, Associate Curator of Paleontology

Associate Curator of Paleontology David Temple likes to say he's also the unofficial head of the Museum's "Department of Mysteries" - meaning that he's our Renaissance Man, the go-to guy when you've got a weird bug, strange goo, unusual fossil, mysterious substance or other generally unknown object you'd like to know what to do with.

Now in his 16th year at the Museum, David organizes the Museum's field program in Seymour. With a background in archaeology, he started here as a part-time teacher and wandered into paleontology by accident. David brings his background in archaeology to the process of digging for fossils - in which the entire context of surrounding each find is catalogued. He also has a passion for photography, and many of the images you will see on this site are David Temple Originals.

David is ready for all your paleontology questions. As well as your questions on bug cooking, squamates, space rocks, or almost anything else.