Sunday, October 28, 2007


Not everyone can be the giant of their era - and this diminutive reptile is proof. The biggest Captorhinus was only about a foot long; runts topped out at about 7 inches.

This field sketch of a Captorhinus shows it much closer to a Dimetrodon that it would have wanted to be, in order to illustrate its small size. (c) Robert T. Bakker

In addition to being teensy, the Captorhinus was also extremely primitive. As Dr. Bakker describes it, "If you started as a Captorhinus, you could end up evolving into just about anything." This species is close to the base of almost every modern species' family tree.

If you saw one today, it would look like a chunky lizard with a pointy snout. It also had two complete rows of teeth, for cracking and eating something small and hard, like snails or millipedes.

The HMNS team have found dozens of Captorhinus fossils at the site, including vertebrae, ribs, legs and several examples that are almost complete skeletons. Shed Dimetrodon teeth have been found with these fossils, proving yet another species had a reason to run when the Texas Finback lumbered on the scene.


It would be a good idea to write this down, because I'm definitely not going to be able to spell it twice - Trimerorhachis is an amphibian that looks just like a modern mudpuppy, except that it comes equipped for battle. We think of frogs and salamanders as having soft skin, but this species is covered in bony armor.

As it turns out, nearly all of the amphibians found in the Texas Red Beds are similarly battle-ready, covered everywhere with armor. As Dr. Bakker puts it, "You could hit them repeatedly with a hammer and not slow them down." Why? What did they need this protection for? And what made modern amphibians get rid of it?

Fossils from this species are surprisingly rare at the dig teams' site, though they have found pieces of a skull at the main site.

Diadectes: Giant Amphibian

At 10 feet long, Diadectes was a formidable amphibian. It was also one of the first known plant-eating vertebrates - meaning that despite his impressive size and heavy bones, it was still Dimetrodon food.

Diadectes was strong - perhaps the strongest species of the time. It had shortened jaws and blunt teeth for grinding plants - but it also had shovel-shaped incisors, an example of which is shown above, found at the Seymour site. In addition, its wide, strong claws would have used for digging - to hide, or to look for roots to eat during the dry season.

Fossils from this species have been surprisingly rare in the main fossil bed the team is working on - only one or two examples per thousand. This is a mystery, as Diadectes would have been the main prey for Dimetrodon. The site is littered with Dimetrodon remains - so if not Diadectes, what was it eating?

A field sketch of Diadectes. (c) Robert T. Bakker.

That Daffy Edaphosaurus

Warmly called "Daffy" by many who study this species, Edaphosaurus looks like a Dimetrodon with a weight problem - which seems unfair, since this species was a vegan. The original vegan, in fact - along with Diadectes, Daffys were the first species to eat plants on land, striking fear in the hearts of conifers everywhere.

Field sketch of Edaphosaurus. (c) Robert T. Bakker

Daffys had a tiny head on a huge body, with legs that are also much shorter than its cousin, the Permian king of the food chain.

That massive body needed a lot of water, and the team has found bits and pieces - such as big vertebra and leg fossils - of this species near the lakebeds on their site. Surprisingly, they've also found a site that may have a nearly complete Daffy - in a dry bed. (The redder the sediment, the drier the local climate; also, amphibian species can't live without constant access to water, so their presence indicates water in the environment.)

What was our Daffy doing so far from water? This week, the team will continue digging this dry site and looking for more clues.

Eryops - Permian Jaws

Eryops was the Permian Jaws - a seven to eight foot chunky amphibian, covered with armor, and with a head like an alligator, including the dangerous, strong jaws. Despite Dimetrodon's place as king of the Permian food chain, a smart one wouldn't go too close to the water's edge. Eryops could take out a juvenile Dimetrodon, no problem, and even a mature Dimetrodon might find himself on the business end of a row of razor sharp teeth. Kind of like Godzilla vs. King Kong.

Eryops was the top water-based predator of the time, and would have eaten anything in and around the water's edge. If not for later Triassic amphibians, he would have bragging rights for largest amphibian ever. As a cold-blooded amphibian, he would have grown slowly and lived to terrify fish and other aquatic species for a very long time - perhaps 100 years. In Seymour, the team has found fragments of Eryops skull and jawbone.

Lysorophian attacks!

The mighty Dimetrodon was the biggest, scariest, most massive thing to walk the Permian, the size of a modern-day tiger. But what teeny-tiny little creatures scurried around between its toes?

Look at any environment today, and you'll see that most things are small - like the hundreds of species of frogs that inhabit the rainforest or the hundreds of thousands of species of beetles living all around the world. And while it's easy to be wowed by the biggest and the meanest - it's often the smallest of the small that have the most to tell us about what life was like when they were alive.

Though the small critters have the advantage of numbers - it's the big guys that are most likely to stick around long enough to get fossilized. Small bodies are easy prey for scavengers and tiny skeletons often don't have what it takes to survive the elements long enough to be buried and preserved.

And so our knowledge is skewed to the super-sized - the Megalodons and Titanosaurs. But the pint-sized are much more sensitive to their environment - like the frogs or salamanders of today - and can tell us much more about conditions in a given era.

For this reason, the HMNS dig team has been thrilled to find many fossilized Lysorophians - which grew to only about a foot long - at the site.

(c) Robert T. Bakker

Though small, this species was armed to the teeth:

"The jaw bones were thick for such a little animal and carried strong, slightly curved fangs...Most astonishing was the body form...The torso went on and on and on. And on, a total of nearly a hundred vertebrae, so the distance from neck to hips was thirty times the head length. The ribs were long, curved and of exceptional thickness and strength. In other words, the design was emphatically like a chunky snake’s."

Though they resemble thick-bodied vipers, Lyserophians are in fact amphibians - evident from four stout bones in their throats that supported gills, something no reptile ever has. And they used this as a weapon, too:

"Gill slits aren’t just for breathing in the water. They’re for hydraulic ambushes."

In theory, the Lysorophian would have explosively widened it's mouth, sucking in water and prey, clamped the jaws shut to impale the prey, and then sent the water rushing out of the gills. In addition:

"The jawbones of lysorophians were stouter than what most amphibians have today, so the killing bite must have been stronger...Plus – the immense strength of the ribcage could have pinned prey within the body coils."

Permian small(er) fry had much to fear from the Lysorophian. But what, in turn, killed them in such numbers in the Texas Red Beds? Hundreds have been found, each of similar size, and all curled into a ball, with the head tucked between the torso.

As it turns out, drought doesn't care how strong your jaws are. And in the Late Carboniferous-Early Permian, the world was hit with one of the greatest killing-drought cycles of all time. As an amphibian, Lysorophian needed water - and lots of it. To survive the drought, it learned to hibernate.

"The rainy season would mean a flush of greenery and prey everywhere. Lysorophians ate their fill and grew fast, courted mates and reproduced. Then, when drought returned, the entire generation went down into their burrows together...The Amphiuma of today’s ponds curl around their eggs to keep them moist and safe. Maybe the bomb-shelters of the Sleeping Serpents were maternity wards."

On the HMNS site in Seymour, the team has found five complete skeletons, in the same grouped pattern. The team has also found Gnathorhiza (Permian Lungfish) - also burrowers - nearby. Dr. Bakker theorizes that "Perhaps they were waiting for spring rains that never came." Like the amphibians of today, they are important environmental indicators - whenever a large number are found together, you know that something happened to kill them off.

(Quotes and information excerpted from The Sleeping Serpents of the Texas Redbeds by Dr. Robert T. Bakker.)