Today Peter Falkingham, fresh from finishing his PhD (congratualtions by the way), tells us about his work on dinosaur footprints. Some prints are rather enigmatic and Peter has been working on how they might have formed:
Archive for June, 2010
Tags: Brachiosaurus, dinosaur, Diplodocus, sauropod
Pterosaurs really do seem to have become the theme here of late, and I’m hardly one to miss a chance to talk about them. This time it’s the last bone of the wing finger, less well known as phalanx IV-4 since it is the 4th bone of the 4th digit. It might seem like there is little to say, but there are some features of this bone that are worth noting.
For a start, it tapers to a point which is not seen much even in animals where there is no ungual (claw) bone. It does happen, but not often to this degree. This is actually a little odd since, while strain on the wing will be less at the tip than the centre, the tapering extends over the whole length of the bone rather than only really being concentrated at the very end as you might expect. Certainly it’s not like the whole wing finger gets progressively thinner down it’s length as a result of the ever decreasing forces, so why taper the 4th phalanx alone. I’m not aware of any obvious mechanical reason (though my knowledge of aeronautics is not that great, I know enough to find it odd) and I can’t recall any explanation having turned up in the literature.
This bone is also generally the shortest of those in the flight finger, but not always. It is always the shortest in the pterodactyloids, but a couple of basal forms have a IV-4 that is bigger than 3 or 1. Incidentally, it’s also proportionally longer in the rhamphorhynchoids than the pterodactyloids (i.e. it makes up more of the wing).
Finally it often has a slight pathology (as seen here) of the tip curving to point slightly (or occasionally, very) posteriorly. This is a pathology and not an evolutionary adaptation since it is rare and never seen consistently on taxa or (to my knowledge) individual specimens. In other words, while some wings and odd bones show it, you don’t see all members of a single species with it and I don’t think I have ever seen it on both wings of a given specimen. However, what causes it is another matter – it could be a developmental problem where the bones are deformed during growth or the effect of stresses and strains of flying causing the bones to bend and twist. There’s no direct evidence either way, but given that you don’t see the other bones of the wing distorted in this way then I suspect the latter rather than the former as otherwise all the bones would be affected and not just the tips.
One final entry on pterosaur heads, and once more it’s from the Oxford Museum. This time out it’s Ornithocheirus. Or Anhanguera. Or, well something. This is quite a common issue with the identity of some models or artworks of certain extinct organisms. Not only is the taxonomy of Ornithocheirus and its closest relatives controversial, but the identification of various specimens is perhaps incorrect (even taking into account the taxonomic confusion). To cap it all, most of them probably looked more or less the same once the flesh has been put back on the broken bones.
Sure, there are important characters here based on tooth shape and position and the size and shape of the crests. But by the time you have made allowances for natural variation and ontogeny and the issues above, it’s probably not unreasonable to call this particular model any of half a dozen species names in two or three genera with good reason and no obvious or especially tricky contradictions. I’m happy to call it Ornithocheirus as it was labeled as such in the museum and presumably was based on material listed under that name, but the main thing is that it is a beautifully crafted model with much going for it in terms of aesthetics and accuracy.
It seems that I have drifted into pterosaur model week on the Musings what with all the goings-on in London. With that in mind I thought it nice to carry on in the vein with a couple of nice pterosaurs from the Oxford Museum.
I should add that in addition to all the backlog of work
As promised here are some behind-the-scenes images of the new open display in London on pterosaurs. My thanks to Mark Witton for letting me post this and my congratulations to Mark and his team on their achievement. Sadly I won’t get to see this but I know more posts are coming on other blogs so that will have to do for me and those of you who can’t make it. Enjoy.
Those keeping up with events on the Pterosaur.net blog and elsewhere will know that Mark Witton has long been engaged manufacturing a whole bunch of life-sized pterosaur models and busts for a major exhibit in London as part of the celebrations for the 350th anniversary of the Royal Society. That will formally open tomorrow and I have some nice behind-the-scenes photos lined in as part of this. In the meantime though, here is a non-sneak preview from Portsmouth where Mark is based. I’ll be out of the country while the exhibit is open so on my recent trip to the UK I dropped in to see the models, Mark himself, Darren Naish and other friends and colleagues in Portsmouth. Hanging in the foyer of their department is this rather nice Pteranodon model that used to hang in the galleries of the Natural History Museum in London. It seemed appropriate to use this then as an introduction to the exhibit and wish Mark good luck with the event.
Or to put it in less complex terms, the natural variation seen in a species. This is a slightly timely post following on from that of yesterday on natural selection. Here is a concise demonstration of the variation seen which nature can then act on. In this case it’s the coat colour of fallow deer. These individuals live in a London park and as such are not exactly open to the full rigours of natural selection, but the variation is certainly natural and that’s what we are interested in.
Fallow deer normally look like the individual on the far left – a light-medium brown with a lighter underside and white dapples down the body. However, you can also see a near spot-less animal on the far right (fewer spots and much more faint than usual), a much darker and spotless animal and behind that and to the right, a near black one. Over on the left at the rear (though not very clear) is a nearly all-white stag. Thus while obviously part of a continuum, we can see white, light, normal, dark and near black forms in this small herd. Natural variation has generated quite a choice and it’s easy to extrapolate a little and see that heavy snow over a number of years might select for a better camoflaged white gene to dominate or a new nocturnal predator to have trouble spotting black individuals at night. The variation is there, it just needs some selection to drive it one way or the other and a profound change might rapidly be evident in the population.
Tags: evolution, natural selection
I have a number of science literate friends who, while they are perfectly happy to accept that evolution is true, don’t know the real fundamental of what natural selection implies or how it was derived. This is not a criticism of them, as I have argued before, not all ‘argument from authority’ is invalid (in context) and indeed those arguing against something without understanding are not really helping the situation. However, it seemed like a fun challenge to try and explain the very fundamentals of evolution by natural selection and the evidence (or at least examples of it in action) in as few words as possible. Explanations of evolution tend to run to a line or two, or entire pages or even book chapters and there seemed to be a spot on the market for something in between. A couple of minutes reading that includes as much evidence, theory and explanation as possible but in a compact paragraph. It might well be of interest and of use to some, so here goes.
Evolution by natural selection is the process where, over numerous generations, organisms adapt to changing environments. The environment can mean climate, geography, competition from predators, prey, or others of the same species etc. Traits (like size, colour, stamina, resistance to diseases etc.) are inherited by offspring from their parents (you do after all, look like your parents, and they like their parents). However, changes also occur between generations, both from the mixing of genes through sex, or novel mutations (you don’t look exactly like your parents, or your siblings). Nature provides the selection of which genes are the most suited to keep the individual organisms alive and to prosper. If there is a heavy winter, those with more fat or thicker fur will be more likely to survive, if there is a drought, those best at retaining water will do best, if predators get faster, the fastest prey will most likely survive. Since traits are inherited, those animals which survive best or have the most young will be the ones to pass those traits onto their children. Over time then, certain traits (like thicker fur, or bigger bodies or longer legs) will become more common as the organism adapts to an ever changing world and the species as a whole evolves. This can be seen in the fossil record as organisms change over time (like the appearance of limbs and fingers in fish as they evolve into amphibians, or the change from five toes to three to one in fossil horses). This can be seen in the genes of organisms in the lab as they are forced through mutations and changes by scientists. This can be seen in the wild as pests evolve immunity to poisons or bight fish grow dull when new predators appear, or beaks change in finches to feed on different seeds during droughts. This all adds up to a convincing single picture as nature selects the best adapted individuals and they pass on their traits to their offspring and so over time the species adapts and evolves.
Well that’s a shade under 350 words. More than I had hoped, but less that I had feared and it does (I hope) combine the basics of the theory with easy to understand examples and real evidence, as well as avoiding jargon or complex terms. If I wanted to keep it really short, the latter 3/4 of the last sentence could be considered enough as it does give the very bare essentials. Still, I hope it does a decent job given the intended compaction of a hundred and fifty years of theory and research into a single long paragraph. I’d certainly welcome other efforts in the comments or on other blogs.
A little off kilter for a normal Musings post, but with me being on holiday anything might be a welcome release for those of you who are desperate, simply *desperate* for a bit of Archosaur goodness to fill in the vacant hours till I start blogging properly again. Still, this is an extinct theropod so it’s not too off topic. Here are various image of the dodo as painted and drawn by various artists over the years. I’m afraid I did not take the names and dates down as I was mostly interested in the variety on show. While some are clearly more accurate than others, they are all obviously dodos at heart and as much a product (I suspect) of differing techniques and styles as the varied ability and information available to the artists (I suspect not all have ever seen one). All are photos of originals or prints on display at the Oxford University Museum of Natural History (more to come from there) as part of their celebrations of their 150th anniversary, home as they are, to some of the few dodo remains anywhere.
Tags: Science Communication
This is a very nice opinion piece from Robert Winston. Short, to the point, lucid and clear. He emphasises the importance of science and technology in the modern world and by extension covers the critical nature of science communication and the public understanding and appreciation of science. Well said, and words that need to be said more often.
Despite the often very theropod-centric nature of the Musings, some groups still end up rather unrepresented. While I did try to cover the ornithomimosaurs in more detail a few months back, they have still never had much of a look in on here. Following on from the popularity of the Triceratops post then and with more photos from the Oxford museum, here’s some details of Struthiomimus.
Following a trip to the superb Oxford Museum of Natural History (much more to come from there with time) I have some nice collections of archosaur based photos which I can share. Many specimens were laid out in such a way that taking multiple close-up photos was easy and effective. I don’t known which specimen of Triceratops this was a cast of, but it was beautifully done and in superb condition. I thought therefore that despite the regularity with which this genus is on display in museums, many might appreciate a few details from up close so here they are.