Jaw Fragments and Shoulder Girdle

Jaw Fragments and Shoulder Girdle

We have for your viewing pleasure a couple of unrelated items. Back in July I posted about a jaw fragment with teeth that we found. We now have a second jaw fragment, with tooth sockets. These two jaws are not from the same type of animal. In one, the teeth are in separate sockets  - called "Thecodont". The other, the teeth (now missing) are in a groove with equal sides - called "Aulacodont".

The Aulacodont is most typical in Ichthyosaurs except for the Triassic varieties of Shonisaurus and Cysbospondylus which are Theocodont. The giant amphibians have teeth that are in individual sockets - Theocodont. So who's jaws do we have above? 

The skull we have, amphibian, has teeth present but the details of the jaw are not clear since they haven't been prepared yet. The teeth in the jaw look like the teeth in the picture above.  So I'm betting the jaw fragment with teeth belong to the amphibian, and the jaw with the groove is from the Ichthyosaur. This contradicts my posting of July 26th where I thought we had the Ichthyosaur jaw. We keep learning new things and finding new bones all the time with this specimen! 

As a second item, we have now fully prepared what looks like a Scapula. Previously we had two bones that I believed to be Coracoids. We also have a humerus, or upper arm bone. We can fit all four bones together as they would have been in life. This scapula is thick at the part where all three bones fit together (the Glenoid Process) where the limb rotates. Otherwise, it is very thin about 1-3mm thick. This bone required a full plaster backing to complete the preparation. It came out very nicely - a great bone!. 

 We are still missing the clavicles (collar bones) but one bone is a strong candidate. 

We'll have it out in a couple of days so we should be able to see if it really is a clavicle. 

Humerus, Femur and Scapula

Quick posting - Humerus and Femur and Scapula

I have finished preparing a second upper (proximal) limb bone. Back in the spring I prepared out what I considere to be a Humerus based on one wide end. I now have a second bone that is the same shape, only a little smaller. It also is a mirror image, so it probably came from the other side of the body. I think we have a Humerus (larger bone) and a matched Femur (smaller bone) from the same animal. Both bones have hollow ends, indicating they both came from a subadult animal. The simplest explanation is that we have fore and hind limb bones from one animal. The other explanations (a pathological specimen or bones from two individuals) are always possible but not probable. Here's the pictures (camera didn't focus too well):

I also have the first Scapula removed from the large block and being finished. The front side has all the matrix removed, and the back side has most of it removed. Since it is a very thin bone (about 2mm in places) it would break badly when removing the last of the backside matrix. So I've coated it with Latex and bedded it on a plaster backing. This will provide enough support to remove the remaining matrix. I should have it done next week or two. I used this same technique while preparing a coracoid and it worked really well. I promise to post pictures of the scapula, the humerus and the two coracoids together when they are all done so we have a size comparison. 

Merry Christmas one and all. 

Sincerely, Greg Carr

Proof of multiple skeletons - another type of backbone

It looks like we have some proof of a second type of animal's bones in our specimens. So the dilemma of the week is: what do we call this pair? Bernie and Ernie? Bert and Ernie? Bernie and Bertie?

We have prepared a second type of backbone that is very different from the squished hockey-puck centrums typical of Ichthyosaurs. We have quite a few of the latter type which is what led us to believe we had an Ichthyosaur in the first place. It is about 57mm long by 44mm wide. No processes (spurs) are evident, and I don't see where they would have been if they got worn off. It does have very nice zygapophyses, the interlocking parts between the backbones. There is a large crack across the bone, filled with substrate(coarse sandstone& chert chips) , so it broke during burial. This crack is evident as a broad curved line in picture #1. The squares on the card are 1/4 inch.
Here's the pictures:

Ichthyosaur-type backbone for reference:

 At this point I'll predict that the new type of backbone belongs to the skull, which doesn't look like an Ichthyosaur either. Hopefully we'll have some more backbones of this second animal as we go. Some of the limb bones might be from this second animal as well. The limb bones prepared to-date have hollow ends, indicating the animal was not mature. However we have at least two bones in the matrix that have rounded ends that are not hollow. These would go with the second animal, I believe.

On the original animal, we have previously prepared a Humerus  (or Femur). We now have a second similar bone that is slightly shorter. It also has an interesting ridge across one end that the first bone does not have. So I'll predict that we have the Femur to go with the original Humerus. This means the Ichthyosaur-type animal had 4 distinct limbs, like a lizard-shaped Ichthyosaur like Cymbospondylus. It's not completely prepared, so I'll post pictures of both bones next time.
Have a happy Thanksgiving for those in the US!
Sincerely, Greg Carr

Multiple Skeletons?

Bernie the Ichthyosaur - Possibly multiple skeletons?

The last couple of weeks have seen us remove a lot of fairly barren rock (not a lot of bones) from around the skull. We have exposed a very interesting backbone / neural arch that does not look like any bone we've recovered yet. And we have a miniature vertebrae that may be from a very young Ichthyosaur!These finds may be telling us that we have multiple skeletons, not just one. 

First of all, the interesting backbone. The bone is located adjacent to the snout of the skull. It has very prominent pre or post zygapophyses (I can't tell the difference yet). Yes, I had to look it up too - certainly qualifies for the word of the day! .  These are the parts of the neural arch that rub on the preceding or following neural arches. The difference between the porous bone, where the cartilage pads were, and the smooth bone where there is no cartilage is very clear - excellent preservation!There is another bone immediately under the neural arch that will have to be co-excavated to prepare it. So far, it doesn't look like an Ichthyosaur backbone, so it may be from another type of animal. This strengthens the case that we have multiple types of animals in this block, as unlikely as that seems. 

So indeed we may have Ichthyosaur bones and other bones in this block. Now, how about two Ichthyosaurs? 

During this preparation we have been finding very small, fragmentary bones that resemble cylinders 1 or 2 mm in diameter. These are short, about 1-2cm long. We don't know what they are, but they certainly seem out of scale for the other bones we've been finding. Here's a couple pictures of the bones partially excavated (too fragile to remove completely) . One is on the Coracoid with a scale for reference. 

And here is one for a normal rib for comparison. 

However, about 3 weeks ago we excavated a perfect Ichthyosaur centrum, about 6-7 mm (1/4 inch)  in diameter and length! These photographs are taken through a preparation microscope eyepiece, and the circle diameters are 6 and 7mm respectively. The centrum even has the flattened facet for the neural arch (shown in the pictures). 

So - do we have an infant, or is this a bone from the very end of the tail? I don't know but it's very interesting. 

We also removed a bone that appears to be part of the snout, again located close to the snout of the skull. It needs significant preparation under the scope. Apparently there are no teeth. There are two Ichthyosaur centrums under it to be prepared as well. 

Sincerely, Greg Carr

Geological setting and Tools of the Trade

Geological Setting and Tools of the trade

The rock that Bernie is found in was a large sandstone lens found in a shale formation. Sandstone lenses like this are commonly found layers between shale because of turbidite flows. Turbidite flows occur when an unstable slope underwater begins to move downslope, the moving material becomes fluidized, and the mass of water&solids moves downslope due to it's greater density. They commonly occur in deltas where sands and gravels are deposited at the mouths of rivers, creating over-steepened slopes that are unstable. Small triggers such as storms or earthquakes can cause these 'landslides' to occur. Some references are Wikipedia " http://en.wikipedia.org/wiki/Turbidite " and " http://en.wikipedia.org/wiki/High-density_turbidity_currents " .  To see how the Suplee/Izee area developed geologically during this time you can check out this article: http://pages.uoregon.edu/rdorsey/BM/LaMaskin_Intro.pdf " Bernie was found in the Izee terrane, the Brisbios member of the Vester formation. This formation has been dated as Carnian Triassic.

Here's a picture of a formation with repeated turbidite flows. 

The sandstone Bernie is in was initially laid down in a near-shore environment, possibly where the influence of waves could still be felt. The sand is rather course, and there are scattered pre-existing rocks (clasts) scattered among the bones and shells. Some of the clasts are mudstone, limestone and chert. The limestone and chert were probably eroding out of Permian-age limestone hills of the Coyote Butte formation on land. These clasts also provide some challenge to discerning what is matrix (rock surrounding the fossils) and what is bone. In addition, there are lots of shells embedded in the matrix. Most are just broken-up shells which are not worth saving. However, some are fairly whole shells that are complete enough that we want to save them. We have recovered ammonites, gastropods, nautiloids, brachiopods, belemnites and a couple of bivalves. These invertebrates all have to be classified and should provide a good verification of the age of the formation.

This turbidite flow may help explain the dis-articulated nature of the bones - they are all mixed up. However, they can't have been moved very far since they are still close together. Perhaps they were formed in a delta environment, where overflows from a river bank can carry sediment a few yards and then bury it. Scattering and disarticulation by scavengers and wave action are also possible. 

The sandstone is hard and well-cemented together. It is all cemented together by calcium carbonate. Acids erode the bone faster than the matrix so a chemical preparation is not possible.  It requires power tools to remove it - hand tools just won't do the job. The main tool we use are air scribes, modified for fossil preparation. OMSI has several types of tools including Paleoscribe #5 and #2. I prefer to use my Chicago Pneumatic which I've modified to have different tips. The tips are made out of Tungsten Carbide drill bits with a stop brazed on and the pointy end sharpened on a diamond grinder. Here's some of the points. Conical points seem to work best on this matrix.

The larger tip, which is 1/8th inch in diameter (3.2mm) is used for aggressive removal. I consider it my "Destructo" tool. Here's a video of my larger tip in action:

The smaller tip (1/16th inch - 1.6mm) is used when working right up to the bone or shell surface. It doesn't remove rock so fast, but you can be more delicate and it has less percussive action. I find that keeping the tips very sharp helps immensely to speed up the  process. I generally sharpen by bits at least once a day, and whenever I feel that I'm 'pushing' the bit into the rock instead of letting the tool do the work. The drawback to keeping the tool sharp is that it wears out faster - my 1/16th inch bits only last about 8 hours or so. But that's OK since I make my own and they only cost me about $10 or so. Here's how I sharpen them - the smaller bits take about 5 seconds!

There are generally three techniques I use. All the techniques use the fact that rock is weak in tension and strong in compression. The trick is use the weakness - the matrix must have a direction to flake off into open air. Pushing a tip straight in is like compressing the top of an arch - the matrix is all in compression and doesn't break. Putting the tip into the matrix about 1/16th or 1/8th inch beside an edge, and flaking the matrix off into the free space next to the edge works well.

For fast removal with little danger of bones I put the larger tip against the matrix held at about 45 degrees and push it into the matrix so as to create a groove. I generally follow parallel to other grooves. I have to keep constant attention for hidden bone. If I see a change in color or breakage pattern I stop and look carefully for the cause. Sometimes it's just a broken shell. If it's black I have to determine if it's a bone or a piece of black chert. The chert is harder than bone & the other matrix and it changes the sound or 'feel' of the tool action. Sometimes I just work around the black object to see the shape and size - the chert flakes are generally small while bone continues to a larger size.

For working on the bone surface there two techniques. Both require very small tips - the Paleo scribe #5 or #2, or my  tool with a 1/16th inch bit. One technique I call the punch & flake. In this technique, I remove the matrix down to a layer about 1mm thick across the surface of the bone. Then I push down about into the matrix about 1mm from the edge of the rock. This puts sideways force on the small section of matrix and causes it to move sideways, fracturing off sideways from the bone surface. This cleans the bone surface well, and works best on dense bones with a solid surface. The tricky part is pressing down with the tip about 1mm from the surface, yet stopping the downward motion of the scribe before it touches the bone surface and leaves a pit. Total movement is generally 1/2 mm or less. I generally rest the heel of my palm on the specimen and rock my hand in & out (back & forth) to achieve this fine control.

The second technique works best where the bone surface is indistinct or gradually transitions from full matrix to full bone, sometimes over a depth of several mm. Imagine an broken and eroded end of a bone, the small internal structures sticking out but the solid bone surface missing. If you fossilize this, the outer edge of the bone is not distinct but is a gradual change from no bone to full bone. I hold the tip so that the tapered edge lies flat on the surface of the specimen and sweep it back & forth in an arc. The tip gradually sands away the matrix, allowing you to remove small layers of matrix less than 1/10 mm at a time in a controlled fashion. Remove matrix until enough bone structure shows up that you have the rough shape of the bone prepared. Remember, there is no distinct surface - this is a judgement call!

Sometimes, working in a matrix loaded with fossils, you have to be careful to remove them in an order that minimizes damage to underlying fossils. Here is a typical dilemma:

Generally I work around the bone undercutting it as deeply as I can while watching out for other bones appearing as I remove matrix. I remove as much matrix as I can, though sometimes you can't get it all out. Even using my finest bit, if bones are actually touching there is only so far you can go before you begin eroding one or the other. When I've taken as much as I can and it still doesn't come off I take a hammer and use a cold chisel as a wedge to try to break the upper bone up off the rock. Generally bones will separate along their natural surfaces if under tension. If they don't separate clearly, you work off the parts that remained and glue them back together! 

More to come - Greg Carr

We have the skull with teeth - but is it an Ichthyosaur?

The mystery of the 'mystery bone" has been solved - it definitely is the skull with teeth in place in the upper jawbone! 

The big bone we've been chasing out for over a month is definitely the skull of the animal. Just Wednesday (9/25/13) we uncovered three, possibly 4 teeth in place in the end of the upper jaw. Uncovering the others will need to be done under a 15 power scope as it's just too nerve-wracking to try to do it with a 3 power head-mounted magnifier. This is because the teeth are the exact same color and texture as the small chips of chert common in the matrix, and you can't tell the difference without significant magnification. So we'll rig up the boom microscope over the big block and go for it next week. 

The smaller pointed bone to the right of the snout is a neural arch, not part of the skull bone. It looks like the skull is mostly intact (the right side, at least) although the snout is broken it is nearly in position. It appears to be quite broad toward the back, over 200mm (8 inches) wide as over 50mm are already exposed and we're somewhere toward the mid-line of the skull. It's about 300mm  (12 inches) long as exposed. It will take us several months to get the skull out, as there is lots of rock to pulverize and remove to get it out. A nice Christmas present maybe. 

Stepping back from the excitement, this skull and the other bones, taken as a whole, present a great dilemma and discovery. The skull does not look like an Ichthyosaur - more like a crocodylomorpha (triassic crocodile ancestor)  It has relatively small eyes. I'm not sure which hole is the orbit (eye socket), but it looks like the closed hole in the middle is the best guess, and the curved arc in the back would be the rear of the skull. Whichever hole it is,  this animal did not have large eyes like Ichthyosaurs. The shape of the skull is more like Croc. The arm ones are long, again more like a Croc than an Ichthyosaur. Countering this, the backbones and ribs are very much like an Ichthyosaur, not at all like a Croc. There are no scutes (ostoderms) - bony plates armoring the skin of Croc. The teeth are like an Ichthyosaur. We probably don't have two mixed skeletons. All the visible backbones on all the blocks (not just this first block) are like Ichthyosaurs. My guess at this point in time is that we have a new, very basal Ichthyosaur showing many characteristics of ancestors less adapted to fully marine life. On the other hand, it may be a marine Crurotarsans, or very early sea-crocodile like Thalattosuchis, although they are known from the Jurassic and Cretaceous. This would be earlier than that, as it's Triassic!

Quoting from Wikipedia "Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Crocodilia."

Here's a triassic Sebecus icaeorhinus -Crocodylomorpha  - some simularities are obvious.  

Here's an animation taken from still photographs showing the skull excavation. It shows the block before any of the skull was exposed and ends up with the above large picture. I've had to make it small to be uploaded, it's still 80 megs so please be patient. 

Stay tuned for more updates. I'll be posting about the 'tools' of the trade soon, telling you how we actually do the preparation.
Sincerely, Greg Carr

Mystery bone gets larger, one strange bone possibly identified

Another quick update about Bernie. We have been working for several weeks to get a bone and ammonite out from between the large Nautiloid to the left (bottom in this picture) and the large unknown bone, probably part of the skull, to the right (top in this view) of a large gap between stuff in the center of the main working face.

Well, we finally have them removed. The bone that was removed is very interesting, It resembles a folded premade taco shell, with smooth bone surface as the tortilla and a filling of bone and matrix with a hollow surface. It has hole through it. It is roughly square about 6 cm on a side and about 2 cm thick. One side is a curved bone surface from front to back. The other 3 'sides' look like the hollows found on the ends of the long bones - hollow cavities with knife-thin edges of bone lining them. What I think we have here is a fused ischium/pubis bone like that found in an Ophthalomosaurus (Handbook of Paleoherpetology,m Vol 8, pg 40) with the edges facing other bones incompletely ossified. 

This bone will require some more cleanup on the incompletely ossified sides, but is certainly one of the more interesting ones! The bone along the rim of the 'taco shell' is less than 1mm thick!

This has exposed much more of the very large bone that I suspect is part of the skull. We have 'chased out' the bone along the larger axis, and found it connects to a hollow on the original outer surface of the concretion that had bone showing. It stretches the full width of this picture - over 30cm long. It is well over 10 cm wide and we haven't found the inside edge. Jerry and I both have spent a full day excavating barren matrix from the outside edge of the block, and we'll have several more weeks removing it. This matrix (here at the top of the picture) will all have to be removed to get at the 'outer' edge of the large bone, and eventually behind it. There is one centrum (backbone) at the right end, and another Nautiloid is appearing at the left end, both to be watched and removed as possible. The top of the larger Nautiloid was removed to allow us access to remove the ischium/pubis, and it's being kept safe for re-attachment (probably this next week). 

Several other smaller bones have been removed and need to be cleaned up as time permits. 

More updates. As I tell folks, the work is meticulous, but not tedious - it's always a challenge and very interesting. Sincerely, Greg Carr

Mystery Bone

August Update

Today's post will be brief as no work was done on Bernie in August. Both myself and Jerry, the two OMSI volunteers working on the beast, went to Como Bluff Wyoming on a week-long dig for the Tate museum in Casper, Wyoming. There was 8 or 9 people at the dig (depending on the day). In total we removed and packaged 22 bones. One my be an Allosaurus brain case or Camarasourus jaw. We won't know for sure until it's prepared. We also got Stegosaurus ribs, several partial teeth, and several unknowns. Also I spent a week on Vancouver island, BC, gathering Cretaceous plants and ammonites, and collecting trilobites from the Spence shale in Idaho and fossil fish at Kemmerer, Wyoming (Green river formation). So most of my time was field collecting work, not inside in the lab at OMSI.

Back to Bernie. We have been working on clearing matrix from around a rather large bone that may be part of a skull. It's rather hard to visualize what it is, but a semi-circular notch on the right side may be a partial eye orbit. Here's a couple of pictures.

It is over 165mm (6 1/2 inches) long, 85mm (3 1/2 inches) wide, and very thick in places. I still think it's part of the skull, though I can't place it. 

Can you?

There is another bone on top of it that may be a skull part, too - bottom left in the picture. Also bundled in there is the large Nautiloid, a medium sized centrum, a partial rib, and another bone directly under the bone on top of it. These are all touching each other at some point!

So we have a large mystery bone. It will be several months before it's out, what with moving all the bones on top of it and removing about 2 Liters (1/2 gallon) (minimum) of rock to get access behind it. And we still have to get behind the scapula and a long bone to get them out, too. 

All - in - all, good work to look forward to. 

Sincerely, Greg Carr

An Embarrassment of Riches

5th Update - an Embarrassment of Riches

This report covers from June 18th to July 22nd. 

We continue to uncover many more bones in the block. Most of them are relatively large, and many are touching each other. While this makes it difficult to remove them totally, we have such an embarrassment of riches! First of all, we have removed two touching vertebrae (centrums) one of which still have part of the neural arch attached. 

There are another 3 centrums underneath those, and a wonderful shaped bone that may be part of either a hind limb or a front limb:

We have a large curved bone with a hole in it. I'm betting it is part of the skull. 

There is another large curved bone with a rougher surface (no, it's not preparation mistakes). Possibly another part of the skull.

I uncovered the scapula mentioned in the previous entry. This will be definitely hard to remove, as there appears to be another long arm bone immediately behind it. The long bone has the typical hollow end we've come to expect, caused by the animal being immature.

We have other animals as well - a wealth of Nautiloids (Chambered Nautilus). In this small part of the first block we have already identified 5 of them, the largest about 11cm across. This is an high concentration - generally Nautiloids are rare in the fossil record. My theory is that they were scavenging the carcass as it lay on the bottom, and all were buried together in a landslide (turbidite flow)

Here's one of the other volunteers at OMSI - Jerry Dodson. You can tell our working conditions are just fine - casual attire! Jerry's a retired accountant, and I'm a retired engineer . You don't have to be a graduate paleontologist to learn to prepare fossils!

Last of all, here's a new display case to display the larger bones as they have been prepared. We'll keep adding them as they are ready. Smaller fragments will  stay in plastic bags so they don't get lost. 

4th Update - Bernie's Got Teeth!!

Bernie’s got Teeth!!! – and other finds

This report covers the period from May 18^th to June 17^th, 2013

The highlight of this period, as noted above, is that a fragment of jaw with imbedded teeth has been found! This means that we do have some of Bernie’s skull, even if in fragments, and the teeth are certainly diagnostic.  The teeth are imbedded in their own individual sockets . This dental structure is termed Ichthyosaur Thecodont (R Motani) . We don’t know if the teeth are fused to the jawbone at the bottom or not – it will take an X-ray or CAT scan to determine that.. This is unusual for Ichthyosaurs, where the teeth are usually imbedded in a long groove along the jawbones especially for all Jurassic and Cretaceous Ichthyosaurs. The broken face of the bone was actually exposed on the surface of the concretion, so we know it’s long gone. In the picture below, the left side of the jaw is the distal end of the jaw – end furthest away from the skull.

Having the teeth in individual sockets limits Bernie’s families to the known Cymbospondylus and Shonisaurus or an unknown lineage. Both of these are found in Triassic Nevada though the Cymbospondylus has not been found in the Carnian age, which Bernie’s formation is dated.

One side of the jaw has some funny-looking bone, rather porous and irregular. It may be some preserved cartilage or who knows – old injury site perhaps? 

Other great finds worked on this period is a possible Graphaea, or oyster-like animal. However, this shell has two ‘wing’ projections out the side where all the descriptions of Graphaea do not show these. Perhaps it's a pearl oyster instead - Dr Retallak at the U of Oregon gave this suggestion - Your bivalve is not Gryphaea, but more like Pteroperna cf. P. plana (a common species in the Pliensbachian Robertson Formation)

We are starting to work out this thin blade of bone. Further work (see the next entry) shows this is a very complete scapula. The notches on the edge are from some bone that broke off with the covering rock, which came away in one piece. We have them & will re-glue them back on. Number one rule in Paleontology - KEEP ALL THE PIECES!!!!!

Further work (see next post) suggests this may be part of the skull - 

Last, we have a great Nautiloid starting to be removed. It’s over 11 cm in diameter, and one side is apparently uncrushed. It’s going to be beautiful:

It’s hard to get a full picture as it’s very close to one of the shoulder girdle bones shown above This block contains three other incomplete Nautiloids, and part of another one that could be complete – the rest is in another block. I still think the Nautiloids were eating Bernie’s carcass when they were all buried – this may explain why we have so many in one small spot.

More to come……..