Friday, December 4, 2015

Tail and WTF Bone - Redux!

This is an update on two parts of the project: Re-creating the tail of a Thalattosaur and preparing a very strange bone.

The tail is mostly finished - all the centrums+neural arches are printed and fastened to a mounting base. The 65 tailbones add up to just about 6 feet long (180 cm to those of you in the logical world). I am still missing the chevrons that go underneath the centrums, but I haven't printed any of them yet. It was an interesting exercise in modeling, printing with both 0.5 and 0.3mm nozzles, temperatures, etc. I ended up printing the 45 largest bones with a 0.5mm nozzle and 0.2mm layer thickness. The smallest 20 had to be done with the 0.3mm diameter nozzle at 0.1mm layer thickness to maintain sufficient resolution. The largest bone took about 4 hours to print: the smallest about 7 minutes! I really like how the tail gets blunt out toward the end, like a crocodile, rather than very thin like an iguana.

As for the very strange bone, it is almost finished - and I STILL DON"T KNOW what it is!

It looks like a limb bone. It doesn't look like any of the other thalattosaur limb bones. The bone is very convoluted, with a very prominent ridge down the side and two very deep hollows. The ends of the bones - the articulating surfaces - are different as well. Whereas the Thalattosaur limb bone ends are concave with conical depressions for the cartilage, this bone has rounded ends with only a hint of hollowness. I really suspect that is a humerus of a very different type of animal. Perhaps it's from one of the ancient marine amphibians that were still alive then, or a crocodile or turtle ancestor! Maybe Pat and Eric at the University of Alaska Fairbanks can figure it out

This shows how deep the hollow in the side is. My fingertip is sitting in it - about 3/4 inch (1.8cm) deep!
Anyway, If I don't write again before the Holidays have a great time!
Sincerely, Greg Carr

Sunday, November 15, 2015

WTF - "What's This Fossil" - Bone

So here we are again starting on a new block of rock containing a lot of bones. This block is what we call Block 3. In the original group of blocks it was a small block that crumbled between the larger blocks. In this photograph it's the one wrapped in foil to keep it together.

The reason it crumbles is because it's all full of bones. The largest Femur and the first Illium came out of this block and the ones next to it. I wanted to tackle something productive and new.

The first two bones are already not what I expected. The first on I expected to be a limb bone, and the second a small sector of a centrum. Big surprises on both of them!
Here is the one I first thought was a section of Centrum. However, a little excavation shows it is not a centrum, but is something else.

 After a little more preparation, a split or bifurcation starts to appear. Perhaps it's another skull bone!

 Maybe the back end of the skull, including a brain case and the arch going over to the quadrate.

More excavation reveals a bridge (concave) bone between these two sides. WTF?

A partial neural arch and centrum appear, tucked under the edge of the bone. Sometimes I feel like the bus driver who said "It's much easier to keep to the schedule when you don't stop to pick up passengers" In my case it's much easier to excavate bones when you don't have to work around other bones that you find!

 As we continue to excavate, it becomes apparent that the end of the bone is quite robust - not at all like a skull, much more like a limb. However, which limb bones have a very distinct C-shaped section?  We do have one such bone, which Eric & Pat have called an Ischium. A 3D printed copy is the brown plastic below.  This would be part of the Pelvic Girdle. However, this new bone is much more robust though not significantly wider.  
 One last picture as it stands at the moment. It certainly is a WTF (What's This Fossil). Once we get it out we'll be able to tell. The good part is that the other end of the bone is in the rest of the block, so we'll have it all eventually.

 In addition to this preparation, I've been printing out pseudo tail bones. I'm now up to 40 bones printed out of a total of 65. These last bones are getting small, so I'm going to try changing over to a smaller extruder nozzle (0.3mm instead of 0.5mm)  and printing in thinner layers (0.1mm instead of 0,2mm). Hopefully this will give us the needed detail. These will total up to be a tail over 5 feet long!
Sincerely, Greg Carr

Wednesday, October 7, 2015

Printing Lots of Bones

I've been getting ready for a big display about Bernie at the "Regional Show" here at the Washington county fairgrounds this weekend. This show consists of displays from 5 local clubs - lapidary, rock and fossils. We have this show every year at the Washington county fairgrounds in October. The NARG fossil club is one of the larger clubs exhibiting.

This year one of the advertised headlines for the show is Bernie "Older than Dinosaurs!". So I've been working to put together a good presentations. I'll have two display cases as well as bringing my 3D printer (and running it). I may also bring my 3D scanner as well, though we may be tight for desk space for it.

So for a good display I've been printing bones - Lots 'O Bones - though I haven't printed out all the bones we have prepared. For the bones that are centerline (brain cases, vertebra) I only have one of each. For the rest I've been printing out mirror images as well as the originals so as to recreate a full animal. Here is what I have to-date:
We have a full skull in white: the original half-skull below it. Skull roof pieces from two other skulls with their mirror images. Two premaxillas, one with a mirror image. Three braincases, and parts of a 4th and 5th. Some internal skull bones - probably related to the palate. Two humeri - we have other limb bones but I haven't printed them yet. A start of the tail - thirteen bones out of a total of 65 (see why I picked 65 later). These vertebra are 1,5,10 etc - the graduations between the adjacent vertebra are finer. And a 1/2 and 1/4 scale mason's hammer!

As you see, these bones are quite glossy. They are all printed in ABS and have been smoothed with hot acetone vapor. It is harder to print large pieces with ABS but the smoothing process makes it worthwhile. 

So here is the process I have followed to print out the graduated series of tailbones for a full size reproduction. 

1) Have a good bone to copy. In real life, a body vert is not like a neck vert is not like a tail vert. However, I have a really good centrum + neural process combination that I wanted to copy so I used that. Here's the picture taken during scanning: 
It is the best combo found to-date. 
2) Have a good know specimen to copy and get dimensions from. Since we don't have an articulated  specimen of Bernie, I have chosen to get dimensions from a wonderful specimen of Midentosaurus Brevis from China. This animal is about the same size as Bernie, the same age, and is wonderfully complete. Here is the reference article data: 

 Look at how complete this specimen is! This thing is 12 feet long!

Best of all, they have closeups of the tail so I can get accurate dimensions of all the tail verts! And they all have neural processes (probably to make a flattened tail to swim with) so my choice of a vert+centrum can be partially justified. Wait until I get the chevrons (the little Y-shaped bones under the verts) printed too. This animal had 13 neck verts, 25 body verts, 2 sacral verts and 65 tail verts (that's where the 65 comes from).

3) I took measurements of the length and diameter of the verts (minus the neural processes) and put them in a spreadsheet. I did a curve-fit on the data, and projected out the dimensions of each vert as a percent of the largest (number 1). My inner engineer is showing. 

4) A series of bones is then prepared in the Slic3r software. I can import the scanned bone:

Set it upright and duplicate it. My computer can only handle 6 copies at once, so I'll end up printing variations of this about 11 times. 

Now, each individual vert can be scaled according to the dimensions on the spreadsheet to gradually decrease in length and width as we go back the tail. The two dimensions do not scale at the same rate - the verts get smaller in diameter faster than they get shorter, so the verts become skinnier and skinnier. 

5) Last of all, the bones are printed, cleaned up and vapor-smoothed. I've printed up 13 but some will have to be done again as the initial scaling was incorrect. Overall they will be a tail about 50 inches long! 

This goes to show some of the real benefits of 3D scanning and printing instead of moulding and casting. Scaling objects and making mirror images is really easy using 3D digital techniques. 

Sincerely, Greg Carr

Monday, September 21, 2015

Mandible or Maxilla - it's complicated!

I posted a few pictures of a skull fragment and a piece of bone that I thought was a mandible. The mandible, of course, is the lower jaw. These both came out of block 1. Here is the skull piece:
Here is the other side, the probable inside

And here is what I thought was a mandible piece:

We also have a little more of this second bone that was in another block (block 2). It was prepared last year and the two pieces have now be re-united. Block 1 and block 2 broke naturally, and the bone spanned the gap across the two blocks. The smaller piece is closer to the body, so it is the proximal part. Fitting these two bones together we can clearly see the teeth at the  distal end of the jaw bone, while it apparently transitions to a groove without teeth on the proximal end:

After re-assembly is is clear that it is not clear how this bone - the supposed mandible - fits into the curved jaw. Thalattosaurs have weird jaws and tooth structures, but this is just plain not working. Here's a whole bunch of pictures from the web illustrating their strange mouths:





Mesosaurus and relatives


I told you their jaws were strange!

Worst of all, the best way it fits is as part of the upper jaw. This would make it another Pre-Maxilla, or the Maxilla. But is looks nothing like the two other pieces of upper jaw we have - one on the whole skull, one excavated last month! These pictures are taken of the accurate 3D printed copies as the originals have now been sent to Alaska for study.

However, I think this picture clears up some confusion. 

It is the inside of the front of the skull and the similar part of the unknown bone. They look very similar, except the new bone is smaller. There is a clear depressed notch on the right end (proximal) of the bones. I measured the distance from the left end of the bones to the beginning of this notch. The whole skull is 95 mm - the new bone is 85 mm. So we either have a younger animal, or the other sex. This might also explain the differences in profiles of the nose - sexual dimorphism? Age Progression? Natural Variation? 

With a Puzzled Perspective, Greg Carr

PS I sure like working with 3D printed reference materials - they don't break when I drop them!

Friday, September 11, 2015

Mandibles and scraps

I'm collecting pictures of all the mandible parts that we have found to date. A long time ago we found our first piece of mandible. This gave us the first clue that skull pieces would be found, even before the actual half-skull was found. Then we found an enigmatic piece which looks like an Ichthyosaur mandible piece, with a groove for tooth roots. I'm not sure now that is came from an Ichthyosaur since we have not found any other pieces like it. Here are pictures of both of them.

Here is the second definite mandible piece. It is split and the tooth roots are visible in the jawbone.

Latest, we have a more complete mandible in two pieces. One was excavated last year, the other piece a few weeks ago. They are both from the same bone, but were located in two blocks (block 1 and block 2) and were broken through when the blocks broke. This is the most complete fragment so far. It clearly shows that the front part of the jaw had teeth in sockets, but further toward the rear it transitioned to a grooved bone that may not have had teeth. Think of a horse, with cutting teeth in the front and molars in the rear separated by a vacant space. ( where the bit goes).  Other known thallatosaurs have weird tooth patterns so this is not surprising, I'd really like to find a whole lower jaw, or at least more toward the rear, but you get what you get on these beasts.

I wish you could see the detail in these teeth. They even have small pits in them. A retired dentist friend of mine ( Greg Gentry) from the NARG group says it's probably a case of the enamel wearing through and exposing the dentin, Since the dentin is softer, it wears away and forms a pit or depression. Anyway it's really cool and wonderful to think that these teeth were used 230 million years ago and were made the same way as current teeth, even though tey are reptile and our teeth are mammal.

 Last of all, I've been going through the back-log of bones removed from the block but not yet finished. This includes a lot of smaller fragments and backbones  - centrums. They don't tell us a lot scientifically so they have a lower priority, but we need to do them eventually. Here are a lot of rib fragments:

Ans here are a couple of centrums - the force-bearing part of the backbones. One of these is very unusual by being thin for it's diameter. We have one or two like this already. They both show the typical hourglass figure where the neural arch attached to them, so we know they are both from these thalattosaurs. 

Sincerely, Greg Carr