Archive for May, 2009

Good days and bad days

Just a nothing little post this, but I rarely talk about my work or life as a researcher and I think amny people would find it interesting to learn a bit more about what we do. Actually, they probably won’t find it interesting, but rather enlightening as it’s probably rather diffeent to what they expect.

Anyway today was a vey mixed day in some senses as a lot of dispirate things kind of came together, both good and bad. On the bad front I found out a fellowship I had applied for has been turned down (kind of expected but still not good) and that several colleagues who I have not had the chance to see in a long time will be visiting the IVPP very soon – while I am in the field, so I almost certainly won’t see them. On the upside however, I have formally had a paper accepted today (one that has been dragging its feet and that I am rather proud of), managed to finish another (well, it’ll sink into the blackhole of co-authors next, but at least it’s off my desk) and managed to get approval on an erratum for a previous paper that I really should have done months ago but got held up by my not being able to contact the editor.

Well, that’s about it, a mixed day, but overall a very positive one. Now back to the grindstone of dinosaur behavioural ecology, sauropod necks and pterosaur wings. It’s a hard life. (Sometimes).

Dinosaur pelves – that ornithischian / saurischian thing

There are probably some people somewhere who have not seen a dinosaur book at some point in the last fifty years and not spotted that it beings by explaining the difference between an ornithischian and saurischian pelvis and what this means for dinosaur taxonomy. In case anyone has missed it, I’ll go over it here with my lovely assistants, Tyrannosaurus and Nanyangosaurus.

So here they are then the pelves of each of the two major dinosaur clades. The saurischian is to the left and the ornithischian to the right. In each case the animal would be facing to the left with the tail on the right. The three bones of the pelvis are indicated with the ilium in blue (top), the pubis in red (lower left) and the ischium in yellow (lower right).

In the modern field of palaeontology the pelvis alone does not form the defining characteristic of the ornithischians and saurischians but they are still a pretty fundamental part of how we separate and distinguish between the two clades. The names themselves relate to the morphology of the pelvis and how they appear either bird-like (ornithischian) or reptile-like (saurischian). As you can see here the critical part is the pubis, pointing to the front in the saurischian Tyrannosaurus and having been reversed to point to the rear in Nanyangosaurus. Even if you can’t tell which way is to the front on an isolated skeleton or partial picture like this you can still tell them apart with the pubis lying close to the ischium in the ornithischians and being well separated in the saurischian version.

Life however is a delightful continuum and the sheer variation in biology and it’s fantastic and persistent efforts to flout even the most basic of rules taxonomy that we as scientists try to impose on it make it a very difficult subject and thus inevitably there are some exceptions to this rule.

First off, the easier ornithischians. Plenty of taxa have a pubis that while it does extend posteriorly and lie alongside the ischium, they also have a process or even a kind of plate extending forwards from it that looks superficially like the pubis of a saurischian (smaller green arrow, middle left). You can still tell the two apart pretty easily, but it might take a second glance.

Onto the saurischians and a point that has been lost on at least a few people over the years – birds evolved from saurischian dinosaurs. Birds (and with them their bird-like hips) evolved from the dinosaurs with reptile-like hips. There are then, as you might have already guessed, a number of saurischians with bird-like hips and it will probably come as no surprise (to those who don’t already know) are those saurischians closest to the birds – the maniraptoran theropods.

While dromaeosaurs like Velociraptor are perhaps the most obvious and well known ‘bird hipped’ saurischians (given their close ties to birds) there are a number of others. The theirizinosaurs also have a rather reversed pubis as do the troodontids (another close bird relative). All three are still rather different to the ornithischians, since the pubis is not so much retroverted (facing backwards) as simply pointing downwards, or only slightly to the rear with an only mildly rear facing ischium. Indeed in this aspect they look much live very early birds (like Archaeopteryx) rather than the far greater reversal of the pubis in many modern birds which is where the ornithischian term came from. One can therefore fairly readily distinguish between these taxa and ornithischians, and of course when laid together one can see the progression of an increasingly rear facing pubis from a classic saurischian baupla to that of modern birds and demonstrate that birds are indeed saurischians.

Right, I’ve finally dealt with that one, now onto some more esoteric archosaurian musings, though of course it’s always worth covering old ground as well as possible for new audiences.

Big Mama – nesting dinosaurs

Many readers will probably be familiar with the fact that we do have good evidence for dinosaurs not only making, but also caring for nests, not least because in examples like this one, we actually have an adult dinosaur sitting on a nest of eggs. This is the famous ‘Big Mama’ specimen of an oviraptorosaur (this one is actually a Citipati, not an Oviraptor as is often said) sitting on a large nest of eggs. Actually, that’s not quite true, this is a really brilliantly made cast of the original, but you can barely tell that even from very close up, and regardless it’s still a famous specimen and not that often illustrated, so here it is. Well, after the page break, obviously.

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Making field jackets

IMGP2957Something genuinely practical for the ‘Practical Palaeontology’ section this time out, making palaeontological jackets. For those who don’t know, a ‘jacket’ is the name given to the bundle of plaster (or other materials) used to wrap up specimens to transport them. Whenever you see photos of palaeontologists working in the filed they are nearly always accompanied by large white blocks of jackets made up to protect the fossils that have been excavated to get them back to the lab safely. They can be time consuming and awkward to make and there is a certain art to their construction. I thought it would be useful for potential palaeontologists to have an idea of how to make these and perhaps be of interest to more general readers.
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Pterosaurs as dinosaurs, or not

The origins of pterosaurs have of course come up on here a number of times but one hypothesis remains largely untreated and that is the idea that pterosaurs might have been descended from theropod dinosaurs. Normally I would not go into the details of such marginal ideas (it has only ever been mooted once and that was not in a formal reviewed scientific publication) but the fame of the source makes it worth revisiting. That source is the legendary ‘Dinosaur Heresies’ of Bob Bakker, probably the most famous and influential dinosaur book (both to the general public and the scientific community as a whole in as much as it summarised many years of research) ever written. That is the reason I assume this hypothesis has survived and occasionally re-surfaces in popular writing and the internet.

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I’m rather pleased with soem of the odd requests we get on Ask A Biologist from time to time, it rather shows we are doing our job and providing a real service and of course the questions can lead you into soem intersting disucssions and unusual areas of biology. We have taken questions from teachers and students of course, but also specific ones from guys trying to settle bets, quiz masters, playwrights, authors and in this case, a game designer.  There is lots of good science fiction based on real science, or in this case specifically human physiology, and it’s an interesting concept – how could you modify a human to give them super endurance? As ever, the answer is here.

Bad luck when digging – taking a chance

I wrote the other day about making decisions in the field and how only luck and experience can save you from mistakes and sometimes not even then. I was specifically thinking of one incident that occurred to me during the recent dig in Henan which I thought I would relate…
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A quick note on referees / journals again

Ages ago I complained about two journals taking long times over reviews which led to my ‘landmark’ whinge about peer review and how journals handle authors. One journal did eventually get back to me after yet more confusion (the reviews were back and a decision made, they had just forgotten to send them to me). Today I actually pulled my paper from consideration from the second journal. Fourteen months after submission. While to be fair one editor had bailed out / been fired after the first six months with nothing having actually happened, another eight months later my paper was, apparently ‘still in review’ and the editor was unable to tell me when the reviews might be returned. Remind me again why we put up with this?

All dinosaur museums should have these

I’ve been away agin, ill again and have been having more issues with power and viruses and hence the posts have been a bit thin on the ground. Everyhting should be mopre or less back to normal, so expect proper service to resume. In the meantime, here’s a quick post going back to the excellent and fascinating dinosaur museum in Fukui, Japan. I just love the attention to detail here, I mean, if you are going to have a dinosaur museum you might as well commission specially designed and painted manhole covers for the entry points to your plumbing. Why not?


Measures of size

I’ve taken a stab or two at the whole ‘X was as big as Y‘ school of journalism for dinosaur sizes, and in fact my very first post ever (back on the proto musings before it even started on dinobase) was on mass estimates (later recycled here) for dinosaurs. So today I want to actually talk about what is on offer and why these things are actually useful. Its fine for journalists to promote the size of some of these animals (especially when selling a story as the biggest dinosaur / pterosaur / mammal) but there is actually a sound scientific reason for trying to establish just how big an animal was, and of course a variety of ways of doing it, or more pertinently here, expressing it. You often see things compared in terms of ‘size’, even in scientific publications, and let’s face it, this is pretty much useless unless you get something more specific – are we talking length, height, wingspan, weight or what? Some animals are tall, some long and some heavy, so words like ‘size’ or worse ‘bigger’ are pointless without a specific qualifier. I recently saw a pterosaur being described as ‘bigger than a car’ which must be one of the most inappropriate comparisons I’ve ever seen.

All of these concepts have problems in their measurement and calculation (not least the fact that you will rarely be working from a complete skeleton, and even if you are, the thing you want to compare it *to* might not be complete either). It is worth trying to calculate these things for a variety of reasons, mass estimates are important for looking at speed, thermal physiology (i.e. body temperature), and of course flight. Ecologically, it is useful to know how much an animal needed to eat, how many offspring it could have and how it could get its food, with height being key to the latter – was the animal competing with others or could it outreach them? Length is obviously less critical for these kinds of issues, but can affect the mechanics of swimming taxa and it is often the easiest metric to calculate and in that respect at least, the most useful.

Depending on what you want there are four ‘biggest birds’ – the ostrich is the heaviest and tallest, the great bustard the heaviest flying bird, the Andean condor has the largest wing area, and the wandering albatross has the greatest wingspan. All are the ‘biggest’ in one regard, but you can’t really compare them properly. Oh, and watch out for relatives too, the ostrich may also lay the biggest egg, but in relative terms (in this case body size) the kiwi’s egg is many times bigger. So in short watch out for ‘flat’ statements about size, and also about cross comparisons – you can’t compare wingspan, wing area and mass, yet this does occur. Good, now go and write out “I will not use the word biggest without a qualifier” 100 times.

Fieldwork as a costs / benefits analysis

It always seems to me that palaeontological fieldwork consists of a series of a constant stream of decisions that mirror classic cost-benefit analyses. While this is true of many jobs and many things in life, I don’t think I have ever quite experienced anything like it. Unless you have a huge amount of time, or resources, or both, you constantly have to make decisions based on relatively little information and constantly reappraise previous decisions as the situation changes.

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More on things that look like bone and aren’t

gyp1My post last year on “things that look like bone but aren’t” went down well, but certainly suffered from a lack of illustrations. This time out I had a camera handy and was able to take a couple of snaps of a few bits of gypsum on the surface (above) and weathering out of the rock (below) both of which have a great bone-like appearance thanks to the fine grain of the crystals that look very like the texture of bone and the white-ish colours.

If I see a few more examples of ‘not bone’ I’ll keep them coming.

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