Dimetrodon Gives us a Nod

Model of a Dimetrodon
Creative Commons License photo credit: kaurjmeb

Our new Fossil Hall will feature a trio of fin-backed predators from 285 million years ago, dug from the famous Red Beds of north central Texas. (If you would like to learn more about our expansion and how you can donate to the HMNS’s second century of science, click here.)

One of our Dimetrodons is a monster – as big as they get – with a live weight as big as a Siberian Tiger. That’s 500 pounds.

We’ve got parts from the head end, the rump, the shoulders.  But up till now we didn’t have a perfect head-neck swivel joint, known technically as the atlas-axis complex. This is where the skull meets the neck vertebrae, and it’s the most complicated anatomical unit in the entire backbone.

Just a few week ago we scored the entire swivel apparatus. The bones come from a brand-new site where a single Dimetrodon was buried by a spring flood. The bones are beautiful. Each vertebra is complete and the rock is so soft it can be removed with the judicious use of a fingernail.

Head-Neck Muscles

The head-neck bones tell us secrets about how Dimetrodon acted in life. Here’s a basic diagram for a giant D’don, taken from the superb skeleton at the Smithsonian. The head-neck swivel complex in red. Check out the big prong sticking straight up – that’s the neural spine of the axis. And here’s a close-up of the bones. The neural spine of the axis is the biggest component.

There’s a thick muscle attached to the neural spine that runs forward to connect to the back of the skull.

Reach around and touch the back of your own neck – you’ll feel the muscle. Technical name: rectus capitis posterior (meaning: “pulls the neck straight back”). The great height of the neural spine in our D’don means an exceptionally powerful action in pulling the head back and up. That would be useful when grabbing big, struggling prey.

There is a second set of thick muscles that’s attached to the neural spine and runs outward to the outer corner of the back of the skull. Technical label: obliquus capitis. Meaning: “Muscle that pulls the head obliquely.” This muscle turns the head sideways – also useful when wresting with prey.

Joint Mechanics

Now let’s investigate how the joints operate. The first vertebra behind the head is the atlas. The name comes from a fancied resemblance to the Greek hero, Atlas, who held the globe in his muscular arms. The  atlas vertebra has two parts, one above the other, that together make a cup. Into the cup fits a ball on the rear of the skull.

Check out the cup in our specimen.  We’ll exhibit the neck  bones in a special case, so visitors can get a sense of how the living D’don was an active, dynamic bio-machine.

D’don is very close to the direct ancestry of warm-blooded, hairy mammals, including us humans (we are all warm-blooded, though some of us are hairier than others). We will exhibit a cast of a human neck joint next to the D’don to demonstrate how much evolution has taken lace since Red Beds times, nearly 300 million years ago.

If you enjoyed my post on Dimetrodon bones, be sure to check out my recent posts on the skull of the Ceratosaurus and Archosaurus.

Texas Redbeds – Another 100 Year Anniversary to Celebrate!

Today our guest blogger is Kathy Zoehfeld. She is writes children books on dinosaurs, is very knowledgeable about paleontology, and often accompanies our very own Dr. Bakker and David Temple into the field.

Another 100 Year Anniversary to Celebrate!
November  2009–One Hundredth Anniversary of the Craddock Bone Bed

In November 1909, exactly one hundred years ago, a paleo team from the University of Chicago, led by Professor Samuel Wendell Williston, was exploring the Permian outcrops of Baylor County, Texas, looking for fossils.  That was banner month for the team, because one of Williston’s students, Lawrence Baker, discovered a rich pocket of red mudstone absolutely crammed with bones of the big fin-backed monster, Dimetrodon.  This productive quarry soon became known as the “Craddock Bone Bed”– named after the Craddock family, the owners of the land.

In this same spot, in 1917, fossil hunter Charles H. Sternberg and his sons, Levi, Charles M., and George uncovered what was then the world’s best Dimetrodon skeleton ever found.  It stands today in the Smithsonian’s National Museum of Natural History in Washington D.C.

Texas redbed 3
A rare photo of the
Sternberg brothers in the field (in Wyoming).

For the past several years, the HMNS paleo team has been uncovering even more dazzling fossils at this historic site—more than anyone had ever dreamed!  With awls, brushes, dental picks, and steady hands, we’ve removed about one third of this historic hillside, layer by layer—discovering bones at nearly every level.

Texas redbed 1
Members of the HMNS paleo team
at the Craddock Bone Bed.

Sternberg and his sons came here to get a big skeleton for the Smithsonian.  We too will soon have a big beautiful Dimetrodon skeleton for the HMNS.  But we’ll have so much more!  Unlike the paleontologists who worked here one hundred years ago, we are carefully photographing and mapping the bones in place at every deposition level before we even begin to excavate them and jacket them for transport to the museum.  The data we record and extract will help us understand this fascinating Permian ecosystem and the changes that occurred here over many seasons of drought and plenty.

So, we celebrate one hundred years of fossil hunting history. The HMNS paleo team is thrilled to be part of that history, thanks to the generosity of ranch owners, Bill and Judith Whitley—descendants of the Craddocks who first welcomed Dr. Williston and Charles H. Sternberg.  As we follow in the footsteps of these great explorers, the red and gray sandstones and mudstones under our feet are silent.  But we know that, like books still waiting to be opened, those rocks are full of exciting stories about the Dimetrodon, the poison-spined sharks, the boomerang-headed amphibians, and all the strange creatures that lived and died here over 280 million years ago.  One hundred years from now, paleontologists will still be hunting fossils and unlocking more mysteries on this extraordinary north Texas ranch.