After that hadrosaur the other day, I thought I’d stick up an unambiguous skull. This is of Lufengosaurus, a pretty small basal sauropodomoph (or ‘prosauropod’ if you prefer) from southern China. Actually I have a sneaking suspicion it’s the holotype but I don’t actually know for sure. It is part of an essentially complete and mounted skeleton that’s on display at the IVPP though the individual bones have taken quite a battering.
Prosauropods don’t seem to get much love in general. I suppose they don’t have the supersize of their cousins, aren’t predators like theropods or sport such weird and wonderful ornaments like most of the ornithischians. So it’s nice to give them a bit of coverage here and I have a raft of Plateosaurus photos I must get round to putting up, though that seems a bit redundant these days with Henrich Mallison now a blogger too. After all, what can I possibly say about this animal compared to what he’s already put up?
A couple of months back I posted this on the display of ceratopsian skulls in Tokyo and lamented that they looked great, but were several meters off the ground and thus their position was rather sub-optimal. What’s especially nice with the Carengie’s version is not only that these were nice and accessible, but are all different species to those in Tokyo so between the two, it’s quite a collection. Here then are are Carnegie heads:
The skull was then readied for jacketing. Prior to doing that, a small woden frame was measured up and assembled with glue and small nails. This frame will be incorporated into the skulls plaster jacket later on and provide both strength and allow the jacket to sit flat on a table, not rock back and forth.
Before the skull was jacketed, several things needed to be done. Any deeper low spots (gaps between teeth mostly) were packed with wet toilet paper, then dry sheets of same were put on the skull and dabbed with a wet paintbrush. This toilet paper layering is done until the brown bone coloration can no longer be seen. The toilet paper acts as a separating layer between the skull and the plaster jacket. If you don’t create a separating layer, you are putting plaster directly on to the bone which will have catastrophic results- it will be hard to remove the set plaster without damaging the fossil.
There were still a couple areas on the skull that were rather deep (antorbital fenestra in particular) so these were carefully filled in with solid plaster of Paris until the depression was flush with the rest of the skull. The plaster is mixed in a rubber cup which is easy to clean when finished- you just squeeze the cup and all the dried plaster cracks and falls out.
Tags: anatomy, Pterosaurs, skull
You might think that by now I’d have done Dsugnaripterus to death given the number of times I’ve covered or mentioned this taxon. However there is one last think (at least for now) well worth mentioning, and that’s the shape of the skull in dorsal view.The vast majority of pterosaurs are preserved without a good skull, or one that’s only seen in lateral view, or is rather badly broken or crushed. There are few that are complete and in near perfect 3D but I’ve never shown them before at least.
Here then is a pterosaur skull in dorsal view. Perhaps rather unsurprisingly, it’s more or less triangular with a long and tapering rostrum and a relatively squared off posterior end. While this might fit with your mental picture of the skull, it’s nice to actually see that it’s the case. Even so, the rostrum anterior to the nasoantorbital fenestra is rather narrower than you might expect and the bulges of the tooth roots seem to stick out a little to the sides which is interesting and you can see just how thin the midline saggital crest is. All good really.
The Gorgosaurus skull (left side) was finished on January 27th. A very close visual inspection was made over the entire skull and any remaining bits of bone-colored glue, rock or sand grains removed with a scalpel carrying a #15 blade which I reshaped to suit my requirements on an oilstone and resharpened every 10 minutes or so. A finger was then run over the the entire specimen. Any bumps, pointy bits, or rough patches were reinvestigated to comfirm they were actually bone. If not they were removed. Then a magnet was passed over the entire specimen and surrounding matrix. Magnets are not in a standard preparators toolbox but I use one at the end of each project. Several types of small wire brushes were used to carefully clean the bone surface over the past months and they do shed bristles, some quite tiny (2 mm). This specimen is to be CT-scanned by researchers in the next few months. I don’t want them coming back to me saying some foreign metal object compromised their CT-scan results. While I have kept the Gorgosaurus skull clean by brushing and careful vacuuming, I was still able to get about half a dozen metal brush bristles with the magnet.
I then washed the skull with tapwater and a standard toothbrush with firm bristles. The brush was made wet, then vigorously shaken out so it was only damp, not dripping wet. The bone surface was carefully scrubbed in a circular motion. The brush was then rinsed out in a clear container of tapwater. Each time the brush was rinsed this way, it was easy to see the water becoming more and more dirty as more of the clay particles and other minerals were removed from the bone surface. When the brush rinsed clean after each scrub it was time to stop. Then the skull was put under a desklamp with a floodlight bulb to warm up and evaporate any remaining water. The skull was then allowed to sit for an hour and cool down. This is important for the next step. A heated specimen, having more glue added to it, can have the acetone solvent “boil”, ruining the effect one is now trying to achieve.
A thin mnix of Acryloid glue and acetone was mixed and a thin layer brushed over the specimen and “scrubbed” into the bone with tight circular motions so it soaked in deeply. This glue seals any microcracks and holes. This is vitally important as the specimen is to be latex molded soon. Latex, being brushed on, gets into every nook and cranny. It can be pushed through a crack where it can expand a bit. When the cured latex is removed, the expanded bits of latex “grab” onto or anchor into the bone and require more force to pull out. This pulling action can damage the area involved and compromise the safety of the entire specimen. So it is best to seal over these potential problem areas now, rather than deal with breakage later. However, it is almost always inevitable that some breakage occurs during demolding. Once the entire skull and teeth were so treated and the glue dried within minutes, I was able to step back and get that feeling of a job well done, that every preparator experiences at the end of a project (in this case the skull only)I. I still need to finish off parts of the legs and ribs before molding happens. A molding meeting is happening the middle of next week to discuss how the molding/demolding will proceed. Hopefully in about 2-3 weeks the molding will begin- that process taking about 5 days.
[Dave adds: And now, here it is. The complete and final and finished version of the left side of the skull. Scale bar is 10 cm. And just a couple of months ago it still looked like this].
All photos here and in the series are owned by Darren Tanke and the Royal Tyrrell Museum.
Tags: Pterosaurs, skull
Just a photo-post this time out, with a picture of the skull of Anhanguera piscator from the Museum of Nature in Tokyo. Some may recognise it as the individual written up as a large monograph by Kellner & Tomida, and it is one of the best preserved and most complete 3D skeletons of a pterosaur out there.
This is a photo I took is a kind of half-scientific, half-general interest photo, since while it does show off the anterior teeth at a nice angle, it also shows just how proportionally long and thin the skull is as it disappears into the distance and soft focus. Too often you only see things like this side on, either in scientific illustrations, or life reconstructions which does not really give you the sense of scale or (obviously) three dimensionality to the animal.
I have had special permission to publish this image, so my thanks to Makoto Manabe in Tokyo, and as ever please don’t go using this without permission etc.