Tales of the Continental Divide: The Adventures of Mesosaurus

Mesosaurus was an unusual reptile. It looked kind of like crocodiles do today, with a long, thin body, eyes located on top of the skull, webbed feet, and an average length of about 16 inches. It also lived kind of like many crocodiles do today, in freshwater environments. Possibly one of the weirdest things about mesosaurus is that it did all of these things during the Permian period, 320-280 million years ago. That’s 130 million years before crocodiles (and dinosaurs as well) even existed!

 

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Mesosaurus, next to an Ichthyasaur of a much later age, photo courtesy in the Internet Archive Book Images

 

                In fact, Mesosaurus is was one of the earliest reptiles discovered to have made the transition back into a marine environment. The earliest reptiles appear in the fossil record around 340 million years ago, so it seems that after a mere 20 million years, this retile was done with terra firma. In fact, one of the mesosaurus skeletons that have been discovered is the earliest reptile found with amniote embryos fossilized with it, meaning these are one of the ealiest animals known to have laid hard-shelled eggs. So we’re talking about the early history of reptiles here.

 

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Lower Permian Mesosaurus, photo courtesy of elrina 753

 

But speaking of reptiles, it should be pointed out that mesosaurus is not like most of the reptiles we see today. Ancient reptiles can be divided into different categories, based partly on the number of holes they have on either side of their skull. Snakes and lizards are diapsids, defined by two particular holes on either side of their skull, but mesosaurus was an anapsid, which means that it lacks these holes. Anapsids are very primitive reptiles, and in fact some scholars classify them as “parareptiles”. The only species of anapsids living today are turtles and tortoises, who have a fascinating history of their own.

 

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Mesocaurus in matrix, photo courtesy of Museo Civico di  Historico Naturale Milano

 

The most common type of large reptiles found in the Permian were synapsids, like the dimetrodon in the Permian section of our Hall of Paleontology, and the Edaphasaurus in the great mural featured in that hall. The only synapsids that exist today are, well, all mammals. That’s right, that big, fin-backed lizard in our hall is more closely related to us than to a dinosaur. But of course he’s still a distant relative, like an old uncle.

 

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Recreation of a Dimetrodon, photo courtesy of Rick Hebenstreit

 

But back to Mesosaurus… There’s another reason that this animal is notable, and that’s the 7,772 mile journey some of its fossils made after their deposition! During the Permian, when mesosaurus was doing its thing, Pangea, the ancient Super Continent, was still forming. Pangea formed around 270 million years ago, ushering in the end of the Permian Period and the extinction of the great synapsids, and making way for the reign of the dinosaurs. It was actually the formation of Pangea and the resulting environmental changes (helped by volcanic activity and climate change) that caused this extinction, which was the worst extinction event in Earth’s history.

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Photo Courtesy of David Smith

 

Around 200 million years ago, Pangea began to break apart. The continents that are now called Africa and South America separated, drifting away from each other and carrying the already fossilized bones of Mesosaurus with them. In the early 20th century, Continental Drift was a hotly debated topic, and it was the fossils of mesosaurus that helped to validate the theory. The remains of this fresh water-dwelling reptile, can be found in Eastern South America and Western Africa, separated be 7,000 miles of ocean. We are sure mesosaurus lived in fresh water, because the rock that its fossils have been discovered in specifically forms in that environment. So, either some of these little guys hopped a tramp steamer, or they were dragged with their respective continents. This, along with numerous other bits of evidence, like the mid-Atlantic Ridge, have helped to validate the theory of Continental Drift.

 

A Study in Patience

Written by Jack Alger, HMNS Paleontology Intern

Jack Alger, HMNS Paleontology Intern

Jack Alger, HMNS Paleontology Intern

This summer I bring dimetrodons back to life.

No, life has not found a way, I’m not extracting DNA from inclusions found in amber; I work in the Houston Museum of Natural Science in Sugar Land. It’s a small brick building with a splendid collection of history both recent and prehistoric whose residents stand 30 feet tall and have razor sharp teeth.

Every weekday from 9 in the morning to 1 in the afternoon I sit behind a large table, stare through a lit magnifying glass, and with implements of dentistry I carefully extract the bones of Diego, a 280 million year old dimetrodon, from the hard north Texas rock.

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I am an exhibit.

Visitors of the museum who meander all the way back to the Paleozoic section have the opportunity to watch me work and to ask me questions about anything they please, thankfully usually pertaining to my work. One of the most common questions and comments I get deal with patience. “Wow, that seems really tedious” or “How do you have the patience for that? I certainly couldn’t do it” to which I grin and laugh politely with a “yes it is detailed work for sure”.

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After a few weeks of these comments I would like to make a few comments on the work myself and let you in on some of my secrets on being patient.

My first task upon arriving as the new Paleontology intern for the summer was to sift through the context dirt that once surrounded Diego and now filled a half dozen catering trays stored in a small closet in the museum. I would pick out a pile of dirt half the size of a golf ball and search for the microscopic bones hidden among the dirt often spending hours without finding anything. Now you may be saying “How could you keep your focus and stay patient when you had so much work to do?” To which I answer now “one rock at a time”.

I never thought about the amount of dirt in the tray nor in the closet, I just focused on my little pile, combing through it as if I might find a diamond or some other jewel (being an unpaid intern, this seemed like the greatest outcome) and after just a couple weeks I had finished looking through every single tray in the closet. This early lesson in discipline set me up perfectly for my real job, fossil prep. Now when I attack a bone I don’t think about trying to get all the rock off and reveal the entire bone. No, that would drive me insane. Instead I focus on pushing back the rock a micrometer at a time. Under intense magnification I watch flakes the size of a grain of sand that appear to me to be the size of paving stones come off in bunches. In rare cases large flakes of rock that covered half the bone come flying off in a single touch of my tools and I am filled with such elation that may surpass ever seeing the Texans win a Super Bowl from the sideline. My first lesson in patience is to focus on the little things, take small victories, microscopic even, so that when something big happens you are surprised and filled with joy.

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Now I would be a liar if I said my neck never ached and I never got frustrated with lack of progress, so this is my second lesson. When I begin to feel weary from hunching over the desk or when I become irate at the stubborn rock encrusting my precious Diego, I change my pace. I get up and stretch; I walk around the room and study the fossils on display. I get a drink of water, or I simply rotate the bone and take a different perspective on the situation, attacking at a different and hopefully more prosperous angle. I chuckle to myself every time I change the angle of the rock and where it was once impossible to cut through, large chips start to fly off the bone. Lesson two is when the impatience starts to creep in just take a deep breath, stretch, then change your perspective and you’ll be amazed at the result.

Four hours a day, that’s how long I work. It’s not a long time in the grand scheme of things, but those 360 minutes can feel like 3,000 if you get impatient and watch the clock. During my workday I try not to look at the time more than 4 times because nothing will drive you more insane than watching time slowly crawl onward. They say a watched pot never boils, well a watched clock never ticks. I have come to believe that a minute spent staring at the clock feels slower than an hour spent doing something. So next time it’s 4:30 on a Friday and you’re caught up with all your work don’t just sit at your desk and watch the little clock in the corner of your monitor, don’t even sit around, go clean the break room, go talk to someone in your office who is also done with their work, do something productive and engaging that you normally don’t do and next thing you know it’ll be 5 o’clock and your weekend has started.

Anyone can be patient and everyone can be impatient, patience isn’t something you’re born with its just something you do, like a sport you have to practice to get better. So next time you start to feel impatient just focus on the little things, change your perspective, and don’t look at the clock and you’ll start to notice life get just a little easier.

HIPS HIPS HURRAY! [Dimetrodon Fossil Update]

Your HMNS field crew and lab staff score the missing pelvis!

Willie the Dimetrodon continues to command the attention of your Paleo Dept. personnel. In May through June, David Temple led an intrepid crew who gently lifted the plaster jacket containing Willie’s torso, shoulder and rump. Local ranchers Donny Gale and Gary Max Coltharp once again generously donated their time and machinery – especially useful was the Coltharp front-loader named “Lola.”

But still – though Willie is among the very finest D’dons anywhere, he had a pelvic deficit. Check out this hip diagram.

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Willie’s sacral ribs are there, the parts of the vertebral column that hold the hips. However, the hip bones themselves are still missing. Probably some hungry scavenger came by and bit these meaty bits off (one rib was twisted out of place too  and the lower left shoulder had some bite marks).

“Locality Edge” comes to the rescue. Discovered by a local science teacher four years ago, Locality Edge is an awesome outcrop of badlands, full of tortuous arroyos, box canyons and spires of red rock. The strata here are just a bit later than our Craddock Bone Bed and about a mile away. We removed a pelvis and set it in a drawer.

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We did note that this set of pelvic bones was unusual – the shape was not distorted by the tons of rock that had buried it. Most of the time the burial layers flatten out natural curves of the upper bone, the ilium, and the wide lower bones, pubis & ischium. The Edge pelvis miraculously survived 285 million years under the rock layers. The lower bones kept the strong inward curve that the living animal had.

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The thought erupted in our minds: Could the Edge pelvis fit our Willie? Was it big enough??

Was it the correct species? We took the pelvis out of its museum tray and I brought it to the small but excellent prep lab at the Morrison Museum in Colorado (located a short drive from the famous Coors Brewery). The Morrison Museum generously opens its facilities for special Houston projects. Thirty hours of work later, with the assistance of three delicate pneumatic chisels, the outer form was cleaned of the rock (note the specimen in the skilled hands of a Morrison volunteer at right).

Superb!  And  when the inner surface of the ilium was placed next to Willie’s sacral rib, they clicked together precisely.  The size was perfect. So was the shape – the Edge specimen clearly came from the same species and the same body size.

Now, the pelvis is getting its final beauty-treatment at the skilled hands of volunteers at the Houston Museum prep lab.

Thus the contributions of a dozen volunteers and staff, plus two labs, has taken us one step further in getting Willie up on his feet, to delight and instruct  HMNS visitors.

Science in Action: Live Tweeting Fossil Snake Scanning Friday

Ever wondered where snakes come from? Why they’re poisonous? How they move so quickly? Or, how a a python could eat an alligator? Whether they freak you out or fascinate you, snakes are an ancient species with much to tell us about the process of evolution.

Enter Brazilian paleontologist Hussam Zaher and a one-of-a-kind, 50-million year old fossil snake from the Green River formation in Wyoming.

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Snake Eye by Care_SMC on Flickr

Zaher (professor and curator of the collections of Herpetology and Paleontology at the Museu de Zoologia of the Universidade de São Paulo) is currently in Houston to investigate this unique fossil, which is thought to be the evolutionary link between snakes who take a lot of small bites to eat their prey and snakes who swallow their prey whole (a la the famed alligator-hungry python linked above).

This Friday at 10 am, the fossil will undergo a 64-slice CT scan at The Methodist Hospital, giving Zaher a peek at the previously-unseen inside and underside. The cross-sectional images will allow him to examine the internal structure of the snake’s brain cavity to more accurately place it within the context of snake evolution.

We’ll be there to bring you the science as it is uncovered, by live tweeting (follow @hmns and #snakefossil) the scanning process on Friday morning. We’ll also be getting behind-the-scenes pictures for our Flickr photostream and a video reaction from Zaher once the fossil has been scanned that we’ll post as soon as we can.

Check out the blog tomorrow for a pre-scan post from Zaher. If you’ve got any specific questions you’d like answered, leave them in the comments!