Archive for November, 2010



Darren Tanke’s Gorgosaurus preparation 8: removal and repair

This update covers November 15-16. The loose bone (the right postorbital) stuck in the antorbital fenestra was safely removed on the 15th. I needed a tool that was rigid, strong, small diameter, angled to a point on one end and had a very specific length, plus a very specific angled end on it. It needed a good “handle”. The space under the postorbital bone was such that a tapered tool would not do or fit. As these situations arise any preparator worth his salt will invent or modify a tool to work. Modifying a tool may work great, but then it may compromise its performance or safety later. So I tend not to modify tools for safety’s sake, but invent a single use throw away tool. In this case the choice was obvious- a paperclip modified to suit my needs. It worked great (for the 5 seconds I needed it), and cost nothing. It was needed to hook behind the bone and help lift it out. The postorbital will be fully prepared later. The tyrannosaur skull looks much better with the bone removed now.

Another thing I had to do was glue a paper-thin tiny piece of bone 2 X 1 mm back onto the palatine bone. I have seen many people try and pick such items up with tweezers only to have them: 1. get crushed in the tweezers jaws; 2. fall out onto the floor and get lost forever; or 3. the worst- they shoot (squirt) out of the tweezers jaws, flying directions and distances unknown. Impossible to find. What works for me is to put a small blob of glue on the main piece, then lick a finger tip, touch it to the small bone piece, then simply scrape it with a sharp knife blade onto the glue. From there it can easily be turned over (if needed) and moved into place. Once the glue is dry, excess can be cut away with a sharp scalpel blade.

At the end of the day on the 15th, a new bone was found that gave me hope of a major limb bone, but not enough was exposed to be sure. This morning more work was being done to expose this bone. It was determined to be a hadrosaur (duck-billed dinosaur) chevron; the slingshot-shaped bones on the underside of the tail. So that was disappointing. However, a little later, while digging around some more I found a major tyrannosaur limb bone and possibly another! We are certain we have the femur, but the other bones identity is presently unknown. It’s alignment is consistent with the fibula in a tyrannosaur in its “death pose” with the hind limbs pulled up towards the body. The femur is hollow and crushed so I am mixing 2-ton clear epoxy glue and pour this into the hollow spaces. This glue comes in a 2 barrelled syringe which dispenses the 2 part glue in a 50:50 ratio. It is squirted into a small mixing cup and thoroughly stirred with a wooden tongue depressor such as doctors use (but broken down to a more useful size). The glue is carefully poured in; sometime several batches are needed. I always leave extra glue in the mixing container to use as a gauge of what the glue is doing (is it setting properly?) inside the bone. For multiple batches, I number the mixing containers to see how one batch is curing compared to another. Bubbles rising in the glue are popped with a pin or sharp knife. Any glue that slops onto the bone surface is not wiped off (it will just smear), but allowed to set and is easily scraped off later.

I should also mention that I am keeping an eye of for any evidence of soft tissue preservation such as skin impressions, but nothing has been seen so far.

Late update: We can now confirm and femur AND articulated fibula on the Gorgosaurus, so a tibia is automatic, but what of the foot! There is enough room in the block for that too- fingers crossed.

Dave adds: This series has been going down very well so far and the preparation of fossils is something that gets very little attention. As a result there are, we suspect, quite a few questions ruminating in the minds of the readers and thought that a direct Q & A session might go down well. So if you have any questions about fossil preparation (on this specimen or in general) then add them here in this post. Darren and I will go over them and prepare some answers which will be posted next week. As ever more preparation updates to come soon.

All photos here and in the series are owned by Darren Tanke and the Royal Tyrrell Museum.

You are a scientist

Now obviously I just don’t get the anti-intellectualism thing or really any aspect of anti-science, pseudo-science schtick or anything like it. Part of this comes down to the fact that all people are, at the real heart of things, logical beings. Or at least they are capable of acting logically and of doing so completely unconsciously.

Science is really just a set of rules for producing logical deductions and assessing evidence. Obviously at the academic level it becomes rather complex and fiddly, but day to day life throws up all manner of situations where logic rules and the basics of science – testing ideas and eliminating possibilities is really at the crux of what is happening.

If your light goes out you check to see if the TV is still working. If it is, then the electricity if fine, but a quick check of the fuse box also shows nothing has blown). You get a bulb from another room which you know works and swap that with the other one. It still doesn’t work. To make sure you put that vacated bulb into the now vacant socket and it comes on. So the electricity is not the problem and the bulb is not the problem. It’s going to be the switch, so time to take that out and check it.

You don’t even thing about this, but these are hypotheses being tested one at a time (power, bulbs, switches) and keeping the others the same as a control. Some things are back-checked to ensure that there are no mistakes and to add more evidence. This is the scientific process in microcosm, so how people are unable to appreciate it at a simply larger scale is utterly beyond me. But it does beget a small crumb of smug satisfaction that I know that anyone who attempts to disparage science or claims not to understand it or that the process is flawed is, deep down, a scientist themselves.

Pterosaurs flew, who knew?

Well, almost everyone of course, but that hasn’t stopped some people claiming that they couldn’t. Or at least that some of the Cretaceous giants like Pteranodon and Quetzalcoatlus couldn’t. The main ‘offender’ of late was a paper I took to task for commenting on pterosaur flight while clearly written by people who didn’t know much about them and was not refereed by pterosaur workers either. If you are going to go out on a limb and talk about pterosaurs in a paper, it might be an idea to learn a bit about them first. If not, you run the risk of making some big errors and wasting other people’s time correcting something that shouldn’t need correcting.

In this case, Mark Witton and Mike Habib have gone out there and made the case for big pterosaurs being flight capable. They also talk about the problems of scaling the giant pterosaurs from rather fragmentary remains and of comparing birds to pterosaurs. So, if you want proof (if it really were needed) that pterosaurs were flying animals, then hop over to the Pterosaur.net blog where posts are coming, or PLoS One where the paper is freely available. Enjoy.

Oh, and the media have been all over this already, though primarily focusing on the ‘pterosaurs could vault?’ bit, which of course was published in 2008 and got plenty of coverage in 2009 thanks to this. Still, if you want the media side of things then you can see here, here, and here among others (warning: this may include pterosaurs being called dinosaurs. Again).

Dorygnathus

Rhamphorhynchus, Pterodactylus and Pteranodon tend to get all the press when it comes to pterosaurs as they are known from lots of good fossils. As a result, we have a generally good understanding of their anatomy and they provide fairly good representatives of (respectively) basal pterosaurs, basal pterodactyloids and derived forms. Others get good press because of exceptionally interesting features or soft tissues so Sordes, Jeholopterus and Tapejara are also well discussed.

However, there are quite a few other pterosaurs known from quite a collection of good material including Dorygnathus. This Lower Jurassic rhamphorhynchoid known from France and Germany is represented by more than 30 skeletons as well as numerous isolated elements. Pictured is just one specimen, well, a cast actually, inevitably from Oxford. The colours might look unusual but are quite accurate as the material comes from nearly black shales and so both the bones and matrix are pretty much at the dark end of very dark grey and this can make them tricky things to photograph, though up close the quality of preservation is really rather good.

A recent and massive redescription and revision of Dorygnathus by Kevin Padian has pooled and updated pretty much all of the available material and information into one convenient paper which really should help things along. Even so, this is one of a few underrepresented and under-discussed taxa when it comes to the pterosaur literature and by extension the wider world, so a little post on here was long overdue.

Phytosaur skull

I don’t tend to cover things like phytosaurs simply because I don’t know much about them, rather than that I don’t find them interesting. Writing posts at the rate I do (generally close to 6 a week) means I try to stick to things I know well to save me doing much (if any) background reading on the issue at hand. Still, I do get pangs of guilt about not delving into other archosaurian lineages and especially the wealth of interesting things from the Triassic like phyosaurs, aetosaurs and rauisuchians, though this is somewhat alleviated by the presence of blogs like Chinleana which tend to avoid saurischians and pterosaurs and favour these guys, so the information is out there.

Despite the name, phytosaurs were not herbivores or indeed anything like really, but crocodile, even gaharial, analogues. Long snapping jaws with numerous sub-cylindrical teeth made many species ideal piscivores and the rest of the body was very like that of modern crocodylians. Here is a classic phytosaur skull (though I’m sorry I don’t know which taxon it belongs to) on display in Stuttgart that was too nice to ignore, even if I can’t say much about it, or the group as a whole.

The PPC for 2010

The second annual Palaeo Project Challenge has been going very well and Andy Farke and I have had a ton of people sign up and pledge their efforts to getting papers and other projects finished by the end of the year. And has a full list running at his newly spruced up blog, so head over there and see who was honest / foolish / desperate enough to promise to get their work finished.

Actually I have a small confession to make. My pledge was for a paper on sauropod necks which was in the works with the SV-POW boys. Actually we got it turned around and submitted a few weeks ago (though as part of the mix I dropped to second author). This means that technically I didn’t finish it, and also it was done so early that it’s hardly worth counting it. I have actually started, written and submitted another paper entirely (it’s very short) since the PPC started, and everything else I have on the go either has a deadline attached already (which hardly makes it appropriate) or there is no way it can be done before the end of the year, so I’m actually left more or less pledge-less at this point, despite completing two papers already!

I’ve got to think of something else….

Darren Tanke’s Gorgosaurus preparation 7: safety first

This update covers November 10 and 12, the 11th being a holiday. Work has slowed down substantially on the Gorgosaurus project. At the beginning I was removing 4 trays of waste rock per day, now it is about 1 tray every 4 days. There are a number of reasons for this, all related to the specimen and, the matrix it is in, its fossilized condition.

1. I am finding the top and back of the skull is now what we call “punky bone”. Instead of being hard and well preserved (like most of the rest of the skull), it is now soft and has a consistency somewhat like rotten cork.

2. When the specimen was buried long ago, some tree branches were also buried with it. These in time fossilized into coal. This coal has now become loose so what is left is a hollow tube (representing the outline of the branch) with coal crumbs loose inside. Where a branch rested next to the skull, this means that now a hollow tube lies next to the skull. As you can guess, this is not very good support for the skull, so stabilization work proceeds slowly in these areas. Also cracks continue to be an issue, affecting much of the posterior half of the skull.

3. In other areas, the bone has shrunk away from the bone impression in the rock, so as you dig down, the rock suddenly collapses, exposing a hollow space. At the bottom of this hollow is the bone, sometimes OK, sometimes all jumbled up. In one area the jumbled pieces resembled a train wreck. What should have been a long smooth, continuous and slightly convex bone surface was now a jumble of pieces angled up and down and overlapping each other. Owing to shattered rock (and the bone) all I could do was glue the bone AND the rock so everything is one solid unit. Sometimes it is important to glue the rock too.

4. Palate bones and bones at the back of the lower jaws are paper to light cardboard in thickness. I can only expose about 1-5 mm at a time and glue that, then work elsewhere while that glue dries. Much work is accomplished daily, but it may not immediately appear so in the photographs posted over the past days. This is opposite to the pictures posted the first 3-4 days of work.

I am still trying to wiggle the errant, disarticulated right postorbital out. I am forced to dig down through the secondary fenestra in the maxilla (the smaller of the two holes) to exposed the end of the postorbital. One process of this bone is pinched between the two upper jaws but by micro-mining techniques I will be able to get it out. Soon I will begin to work my way down the neck and expose the vertebrae and neck ribs there.

One aspect of preparation I would like to cover in this posting is safety equipment, often overlooked. We at the Royal Tyrrell Museum take health and safety matters seriously. In the lab we provide all workers with eye protection, dust extractors, dust masks, hearing protection, and hand protection (padded glove) to protect against vibrations from the air scribes. We even have a corrugated rubber mat to stand on which help remove the strain of standing on a hard and cold concrete floor all day. We all have to wear steel-toed boots in the lab. Technicians use all or none of these safety items dependent on the work being involved. Different types of each are provided to suit their personal likes. There area also regular health and safety meetings (by a dedicated committee) and regular lab inspections.

More to come soon. All photos here and in the series are owned by Darren Tanke and the Royal Tyrrell Museum.

The iguanodontian opposable digit 5

It seems to be common knowledge that many iguanodontids had a spike-like thumb that consisted of just a single conical ungual. What is less well known is that the 5th digit in the hand (the little, or pinky, finger) was also modified. You can see it here on this cast of an Igunaodon hand. The 5th finger is smaller and separated from digits 2-4 which are appressed together and obviously bear the brunt of the weight when the animal walks quadrupedally. This offset angle allows the 5th digit to act something like a thumb – it’s a semi-opposable digit that can be used to grasp and hold things. The thumb might get all the fame, but selection has been acting on the whole hand to produce three distinct morpholgies and functional outputs. That’s pretty good for a manus in what is, effectively, a quadrupedal herbivore. Cows don’t do quite so well in comparison.

Darren Tanke’s Gorgosaurus preparation 6: a lucky break

The X marks the problematic scute (see the text for details).

This update covers November 8-9. Much more progress has been made on the Gorgosaurus skull preparation. The eye socket area is the worst crack-wise and will likely be left until the end. Too many converging cracks make this a weak area. Late last week the thin edge of a new bone was found above the gorgosaur’s snout. This was treated at first as a disarticulated gorgosaur skull bone, but further uncovering work revealed it to be an ankylosaur (armored dinosaur) scute or piece of bony armor. This was positioned atop the skull and slightly overlapped on one side. It was an ugly piece of bone and obscured anatomical details useful for tyrannosaur researchers so I decided to remove it.


First the snout of the gorgosaur was heavily glued as was the scute and both allowed to dry. Care was taken to not glue the rock in between as we wanted to remove that. Using a sharp scalpel with a new #11 blade and an airscribe with a long stylus (tip) I was able to dig down around the scute, isolating it from the skull and pedestalling it on the rock. I then airscribed under the scute as far as I could go from nearly every direction.

Airscribing around the scute

Various preparation tools

I regularly used an old dentists mirror to inspect my progress underneath and remove any rock pieces with long-jawed forceps. In one spot the glue had soaked into the rock, thus hardening it. Because the glue is solvent-based I simply squirted as small amount of acetone on it and soon the glue gave way and I could remove the gooey glue and sandstone mass as required. When I was about to pull the scute away, it broke on the end that covered the side of the gorgosaurs snout. This might be a tragedy to some (It broke! GASP!) , but it was truly what preparators and field workers call a “lucky break”. Not only did it give me more access with the scalpel and airscribe, but importantly, it exposed a previously hidden badly cracked and weak area of the snout. This could have shattered had I pulled the scute off prior. These new cracks in the snout were now fully exposed and thus could be repaired easily. The scute was then wiggled back and forth and some water squirted underneath until it came loose without any more problems.

The cracks in the bone under the scute

On November 9th it was confirmed that some of the gorgosaur skull has in fact become disarticulated. In the antorbital region in front of the eye socket I removed what looks like an epipterygoid (part of the braincase). Research papers are very useful at this stage to identify bones and plan for their extraction. Next to it was a large bone end which has been confusing, but was eventually identified as the right postorbital (bone forming upper half of eye socket). Curiously, 75 million years ago this fell off the back of the skull, moved forward to the middle of the skull and was flipped around so the top of the bone is now the bottom (and bottom is top) and flipped again so front is back and back is front. After all that it was then pushed somehow across the middle of the skull so this right skull bone is on the left side of the head! Water currents? Scavengers?

The skull as of the 9th of November

I will be removing the errant postorbital in the next day or so. I am also now finding some of the very thin palate bones. I can only expose a few millimetres at a time, glue the exposed bone, wait an hour or two and then repeat. It is very tricky work as the bone is as thin a rice paper. One wrong move and it is ruined forever.

More to come soon. All photos here and in the series are owned by Darren Tanke and the Royal Tyrrell Museum.

Compsognathus

OK, yet another life reconstruction from the Oxford museum, but this is, I think, probably the best of the lot. It’s a superb model of Compsoganthus, complete and life size. There is still a bit of a perception that all dinosaurs were massive (and obviously the general public like massive dinosaurs – not too many would necessarily be interested in an exhibit of ‘the smallest dinosaurs ever!”. This then does a great job of dialing back the scale and showing what a small dinosaur would look like and obviously contrasts well with the nearby model of Archaeopteryx which is of similar size and also from the Solnhofen of Bavaria but obviously rather more bird-like.

The astragalus ascending process

The astragalus is one of two major bones in the archosaurian ankle (and indeed the ankle is rather important when it comes to archosaur phylogenetics). The astragalus and calcaneum are generally two fairly small and blocky elements that lie between the tibia and fibula and the metatarsals. In the theropods, the astragalus has an ascending process – a flat, triangular plate of bone that sits in front of the tibia and actually sets into a recess of the anterior face of the tibia. (This is also seen in basal saurischians, but it’s not as exaggerated as in the theropods). In some cases it can be really big, reaching a considerable distance up the face of the tibia (as I recall, up to about a third of the way up).

This is a nice example, a Tyrannosaurs astragalus with the subtriangular ascending process clearly visible and set into (and indeed fused to) the tibia. This is one of those classic little quirks of anatomy that, if noting else, provide and excellent little systematic feature – if you find even a small fraction of a skeleton out in the field and it has this, then you know you have a theropod on your hands.

Is there anybody out there?

I’m coming over a bit Mark Witton here with a Pink Floyd reference in the title, but this will come round to palaeontology, honest. To stick with the Floyd years ago my brother gave me a book on them where a professor of music was analysing the music and discussing what he felt was the motivation and message behind the music. This struck me as utterly unnecessary and indeed likely to be confusing and incorrect. The author doubtless had a lot of experience and information and understanding of music and its creation – certainly far more than I do. But then, the musicians themselves were still alive.

Why bother to try and interpret their words and music when you could just ask them? They must know exactly what they were thinking, or at least can make sure you are going down the right path to your interpreted solution if you are going for the subconscious or what they might have forgotten.

This related to palaeo and science in general with something that does seem to crop up from time to time and I was reminded of this by a recent comment on the Musings. A discussion had blown up over what was intended by a rather cryptic sentence in a paper of mine. Did it mean one thing, or another, and was this intentional or a typo? To which the obvious answer is, why the discussion? Ask. The authors are all around and available and their contact details are on the paper which you obviously have access to. Ask them what they meant to say (here it was a typo), don’t waste hot air and start trying to interpret things when there is absolutely no need and the undeniably correct, and indeed only solution is available. To do otherwise is to waste your time and energy and not even necessarily get the right answer, or not know if you have it right when you do.


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