Mystery Bones Identified

When last we updated you, only Basilemys’ scapula had been extricated, but now the coracoid is free as well, thanks to volunteer Jim Duncan.  In this photo, the scapula is outlined in yellow and the coracoid in orange. Add to that the humerus (outlined in green), which Tylor temporarily placed in the coracoid socket to show how everything fits together, and you have the entire pectoral girdle assembly.  (See the February 14^th blog, “A Robust Bone,” for a refresher on the coracoid and humerus.)

 

 

 

To a paleontologist, that’s pretty darned exciting, but even more excitement has come to pass in the last few weeks! Once the bones in the girdle assembly were removed, Dr. Alan Titus went to work with the table saw to carefully remove more rock from some of the “mystery” bones seen in previous months to get a better look at them and figure out what they are.  Turns out they are four vertebrae, and they are articulated, which means they are still in pretty much the same position they were when Basilemys was alive.  It also means there’s a very good chance that more of them will be found as Dr. Titus and crew move deeper into the shell.

 

So here’s a photo of the findings.  The vertebra outlined in dark blue is the dorsal (back) vertebra that connects to the shell.  The light blue outlines show cervical (neck) vertebra #7; green is cervical vertebra #6.  The area outlined in red is shell, and the arrow points to the fusion of the dorsal vertebrae to the shell.

 

 

Up next:  The area within the black circle will be prepared, with the expectation that more articulated vertebrae will be found.  And the dream is that they will lead to a skull, which would be a monumental find, so to speak.  It would be the first basilemys skull found in the Monument, and the first in North America found in this age of rock (75 million years old).  A basilemys skull was found in Canada, but in newer rock (72 or so millions year old).

What makes the skulls such rare finds in these big guys is that the neck and limbs were the first things to fall off when they died, unless some external force — like a river current — pushed them back into the shell, or the tortoise was buried so rapidly its neck and limbs didn’t have time to detach before they were fossilized.

Meanwhile, back at the lab. . . .

Basilemys: Yesterday, Today, and Tomorrow

This is a picture of a tortoise that was found in the Grand Staircase-Escalante National Monument a few years ago and is now on display at the Natural History Museum of Utah.  You can see the similarities to our friend Basilemys, with the jumble of bones under the shell.

 

 

 

Here are a few of the elements in the Museum’s tortoise (click on the photo to enlarge it so you can see the outline colors clearly):

• What remains of the shell is outlined in blue.  Not having the entire shell actually gives the opportunity to see what was found inside this famous specimen.

• The bone outlined in red is the pelvis.

• Outlined in green is a limb bone.

• The shape outlined in purple is a vertebra.

• The items outlined in yellow are actually fossilized eggs, which makes this tortoise pretty amazing because it’s only the second one ever to be discovered with eggs inside of it.

Also on display at the Natural History Museum of Utah is a section of shell from a basilemys like ours.  This specimen is just the plastron (bottom shell) but is one of the more complete specimens for this type of tortoise thus far.  When our current basilemys is done, it will be even more complete than this one.  It, too, will be sent to the Natural History Museum for study and eventual (we hope) display.

We will have at least a few more installments to share with you before that happens, though. Stay with us for the rest of the journey and, unless a Museum staff person is following this blog, you’ll know before the Museum does what their new arrival will look like at the end of the road .

A Robust Bone

Even with having to pack up the paleo lab’s contents in the old building, and move, upack, and reorganize them in the brand new lab in the new BLM building, some great progress has been made on Basilemys.

The team decided to completely excavate each element inside his shell rather than leave them in place and be satisfied showing off the bones they had already partially exposed.  This allows them to explore the entire inside of the shell to find more bones, if there are any, and assure themselves they haven’t missed something good.  Removing all bones may actually provide the opportunity to learn more about Basilemys.

Here is a picture of our favorite tortoise taken a while back, before he was flipped over.  The blue outline indicates shell, the red may be a vertebra, the yellow is part of the coracoid (bone forming a joint between the shoulder blade and sternum), and the green is the elbow end of the humerus.

 

 

 

Flipping the tortoise allowed the team to positively identify some of these bones and, in some cases, see the entire bone structure. The humerus and small section of shell to the right of it were prepared, revealing what is shown in the photo on the right.  Outlined in blue is the shell, green shows the two ends of the humerus, purple is the shoulder blade, and yellow and orange are parts of the coracoid.

Removing the section of shell covering the rest of the humerus allowed the entire bone (outlined in green in the photo below) to be exposed.

 

 

 

 

 

 

By the end of the day the entire humerus was able to be lifted out. Left behind, for now (photo on right), are the shoulder blade (purple) and exposed coracoid (yellow).  The area in the circle shows where the first end of the humerus was exposed when Jim originally started working on it.

 

 

And here is the humerus in all its glory!

 

 

 

The first four photos, starting from the left, show all sides of the humerus with the shoulder socket on top and the elbow joint on bottom.  In the rightmost photo, on top is a view of the shoulder joint head on; on the bottom is a head-on view of the elbow joint.

You can see how robust the humerus was.  Its size and thickness mean it was definitely designed to bear weight.  Paleo lab manager Tylor commented, “If you handed just this bone to me, I would think it was not a turtle bone.”

Jim has started to prepare out the shoulder blade and the coracoid.  Right behind the coracoid is what is thought to be a vertebra.  Stay tuned to see what surprises Jim may uncover in the coming weeks.

What IS That Weird Flat Bone?

That’s the question Jim and Tylor were asking one another over the holidays.  And with the new year came the answer.

But let’s back up just a bit.  In late December, Balisemys was flipped over, the rock covering his shell was peeled away, and the weird, flat bone made its appearance in an area where the shell was missing.

Jim and Tylor went to work on it and were finally able to identify it – it was Basilemys’ left shoulder blade.

 

 

Look at the size of it!

 

The bone off to the side of the shoulder blade (circled in red in the photo below) is the coracoid (circled in green) which makes up the rest of the pectoral girdle (shoulder socket).  The area circled in blue is shell.

Tylor said of his and Jim’s handiwork, “We were amazed by the size of these bones inside the shell. If we were to find this bone in the field with nothing around it, our first assumption would be that this is a dinosaur bone not a tortoise bone.”

Since Jim outlined a good bit of the shoulder complex, he began to cut off some the excess rock on the side of the tortoise and lo and behold, there was another bone.  Given that it is near the shoulder blade on the bottom and a limb bone on the other side, it may be another part of the arm or leg (circled in red).  Jim will continue removing rock from the inside of Basilemys to find out.

A Look Back — Way Back!

On Tuesday, January 10, 2012, in Page, Arizona, Dr. Alan Titus, GSENM paleontologist, will talk about two new predatory dinosaur species named in 2011 from the Monument: the giant Teratophoneus curriei and the much smaller Talso sampsoni.   These two new animals have no direct ties to any species known from north of Utah, and are instead related to forms found in New Mexico.  Dr. Titus will explain how this single fact reshapes our view of North America as it was 75 million years ago.  His presentation, which starts at 7 p.m Mountain Standard Time,  is part of the 2012 free Glen Canyon Lecture Series being held at the Carl Hayden Visitor Center at Glen Canyon Dam.  To see a calendar of planned lectures and descriptions of each one, go the the Glen Canyon Natural History Association web site.