I have just been told that the Musings has made this list of the top 100 blogs for earth scientistis. Given that only a short part of this is given over the palaeo based blogs, I’m delighted. This is my first ever recognition / award / list thing so that’s made my day. Many of the palaeontology blogs will be familiar to regualr readers, but soem of the others might be of interest, so head over there and have a look around.
Archive for December, 2008
The Musings are pretty text intensive at the moment with all the taxonomy and systematics posts flying around, so I thought it was time to bust out a few more pretty pictures of this summer’s fieldwork. I’ll stick up some more stuff from China tomorrow, but today I’ll deal with Mexico.
With the Wellnhofer volume now with the printers (not long now people – please spread the word) it seemed an appropriate time to revisit some of the basics of science publishing that I began with advice on how to publish a paper and complete a PhD. Now let’s take a look on the other side of the fence from the perspective of the people who deal with those papers. Coming soon will be my take on how to review a paper, but we will start with how to edit a volume.
Tags: archosaurs, Dinosaurs, Pterosaurs
This whole ‘Science Basics’ thing is not as easy as you might think. Even simple concepts take in several different branches of biology that some readers probably don’t know at all so while I can try and build up ‘A’ from scratch, it’s still quick tricky without a bit of background in ‘B’, which requires some knowledge of ‘C’, which is reliant on at least a partial understanding of ‘A’. And on and on and on. That is not to denigrate my audience, but I have to assume that at least some people reading this really don’t know much or any biology or palaeo at all, and since I’m not writing a straight through ‘what is biology’ series, but cherry-picking ideas I want to expand on, or I think are especially important or interesting, I can’t just do ‘A’ now, ‘B’ next week and ‘C’ the week after and hope the audience follows the thread. So, with that in mind, I’ll try to keep everyone on board and not bore the “experts” as I delve into the world of archosaurs.
Time to get beyond archosaurs a bit and move into evolutionary patterns and adaptation. Here we were asked about the acquisition of new characters, and more specifically about the origins of lungs. As ever, if you want to see what we saidthen here are the answers.
Normally on here the word ‘archosaur’ is pretty much synonymous with ‘dinosaur’ and ‘pterosaur’, since that is primarily what I work on and what I am most interested in and thus know most about. However, there is the odd occasion when I can bring something different and a bit more generally archosaurian. So here is a mediocre photo of a mediocre specimen (though admittedly it is the holotype) of Sarcosuchus, the giant crocodilian for the North African Cretaceous. This specimen is on display in the fantastic Muséum National d’ Histoire Naturelle in Paris, a place well worth a few hours of anyone’s time, and is quite a small one at just 4m or so, these things got really big (though just how big is another question entirely).
Tags: Pterosaurs, taxonomy
Now that I have managed to introduce taxonomy to you all, I can now go and play with some specific areas or examples to expand on the subject. While pterosaurs were always going to feature sooner or later, they genuinely do provide a good example of the difficulties inherent in taxonomy in palaeontology, so hopefully I can make good use of them and cover some real pterosaur issues and ones of taxonomy too.
Having written about paraphyletic groups and the use of the term ‘rhamphorhynchoid‘ when talking about pterosaurs I thought it wise to discuss the issue in a slightly broader context and highlight the problem of such names. As I mentioned, I think ‘rhamphorhyncoids’ is a perfectly acceptable term as long as it is made clear that this is a paraphyletic group. But assuming you don’t want to do that (which is an understandable position), what are the alternatives?
First off some researchers prefer to use the term long-tailed pterosaurs and short-tailed pterosaurs for the rhamphoprhynchoids and pterodactyloids respectively. There are immediate and obvious problems with this approach. Firstly it is longwinded, and while clarity is to be valued in science communication, so too is brevity. Secondly, by using what are effectively colloquial terms it does not make clear the monophyly of pterodactyloids, since the both are given non-technical names. Thirdly and most obviously are the problems of the anuroganthids and Pteranodon since the former have a short tail unlike the rest of the rhamphorhynchoids, and the latter a long one. Thus the anuroganthiuds are then short-tailed, long-tailed pterosaurs and Pteranodon becomes a long-tailed, short-tailed pterosaur. Thus the use of long- and short-tailed is neither clear nor concise. Other variations (I guess you could point to the 5th toe, or the neck length) run similar risks.
Next we can use a nice general term such as ‘basal’ and ‘derived’ to refer to them. However, as above this suffers from ambiguity, since Rhamphorhynchus for example is a very derived rhamphorhynchoid and thus is a derived basal pterosaur, and equally Pterodactylus could be called a basal derived pterosaur. You would have to be explicit every time you used the word basal or derived and again this gets confusing and requires you make exact statements about what context you are using the words in each time you want to refer to a taxon.
Next you have the use of replacement words or phrases such as non-pterodactyloid pterosaurs, or basal clades, or others. These I do not have a problem with, again as long as they are clear (as non-pterodactyloid pterosaur certainly is). However, again, I do not think these terms are especially nice to use (rhamphorhynchoid is so much more succinct, and its worse in other groups – compare ‘prosauropods’ to ‘non-sauropodan sauropodomorph’) and they are hardly ‘time saving’ in as much as in any paper where you refer to them you will still have to include a sentence along the lines of “the non-pterodactyloid pterosaurs are a paraphyletic collection of basal taxa” just as you would when defining the rhamphorhynchoids.
Overall I find the putsch against paraphyletic terms annoying. I can’t see the harm in using them when they are clear and succinct and are carefully defined (and that is the case here). I don’t see icthyologists putting the word ‘fish’ in quotes constantly or writing about ‘non-tetrapod vertebrates’ (or if they are, I have missed it). People will even still use ‘reptile’ in its polyphyletic sense (i.e. not including birds or mammals) when convenient to do so (admittedly rarely), without problems. The only time this approach is problematic is where one term is synonymous with two different things (like dinosaurs can mean, well ‘dinosaurs’ [i.e. non-avian dinosaurs] or all dinosaurs including birds) and here distinction is necessary. For pterosaurs though, this is not the case. ‘Rhamphorhynchoids’ are paraphyletic, everyone knows they are and accepts that they are, so why replace one term (rhamphorhynchoid) with another longer one (e.g. non-pterodacyloid pterosaur) that still represents the exact same paraphyletic assemblage and still requires the same clarification?
As I recently wrote in a technical note on this issue in a paper “I prefer therefore the systematic term ‘rhamphorhyncoid’ which, despite being paraphyletic, is succinct, accurate and unambiguous”. I find it hard to fault that statement (even if I wrote it).
Woo-hoo I’m on a new dinosaur paper. I have got plenty of papers done (I think) but I have yet to be on one naming a new dinosaur so I’m really quite pleased about this, even if I didn’t actually do too much on the paper. This one is coming out in the Chinese Science Bulletin but the paper is already up online so I’m happy to shout about it now before the thing is formally published in the January issue.
Given the sheer number of pterosaur-based posts on here, I really should have got around to this issue sooner. It was alluded to very briefly in the pterosaur basics post but really deserves a more thorough examination, if only at a still relatively superficial level (since I don’t want to get bogged down in anatomical details). If nothing else, it is certainly worth mentioning a few misconceptions and reversal that occur between the two clades, including one hugely significant one that almost everyone seems to ignore. Let’s take a look:
Having dealt with the basics of taxonomy, we can now begin to delve deeper into the field, and there are some common issues, terms and quirks that should be brought struggling into the light when possible. In time I’ll try and deal with priority, the binomial system as a whole, higher order taxonomy, and those beastly nomen dubia, numen nuda and the rest. However here I want to deal with one of the most vexing and controversial is the near age-old issue of lumping and splitting that comes up again and again*, and causes all kinds of problems and, it should be noted, feelings often run deep.
Naming taxa, and especially species, can often be somewhat subjective. In fossils particularly it can be hard to account for individual variation (obviously not all individuals look exactly alike), possible sexual dimorphism (differences between males and females), and even ontogentics (changes in shape as a result of growth and maturity) when working with a morphological species concept. Combine this with early practices that tended to favour naming any old bits of bones as a new species and you can understand why many people think that some species have been named unnecessarily, and that these should be brought together. This is the practice of lumping – quite literally lumping several species (or other ranks of taxa, though it is obviously most common and the species and generic levels) together under a single name because there is not enough variation to justify the extra names and divisions. The opposite of this is of course splitting – pulling apart one genus or species to make two or more. But of course there is more to it than just this.