Last week I took a very brief trip to Germany to do a round of several museums and collect some data for various projects I am working on. As well as catching up with some old friends (human and fossil) I got to see some new ones (human and fossil). I’ve been filling in the pterosaurs over on Pterosaur.net (including this guy which is an absolute must-see) but here I thought it would be best to bring back Sciurumimus. This little theropod did make an appearance on here when first described, but now I have a couple of pictures of my own (the specimen is currently on display in the Solnhofen Museum) it seemed time to bring it back. So here’s a couple of additional images of this outstanding little theropod.
Archive for the 'Dinosaurs' Category
Tags: archaeopteryx, bird, evolution
Continuing my collection / database of Archaeopteryx images, it’s time to increase it a little further. Last week I helped out at the Natural History Museum’s ‘open evening’ called “Science Uncovered”. I was there basically to be a scientist for people to talk to, but there were whole stands from other universities with research connected to the NHM and of course a raft of curators, researchers and other staff bringing the behind-the-scences stuff to the front of house. One special had been laid on that really drew the crowds – the 11th Archaeopteryx specimen.
Although it has appeared on here before, this is the first time I had seen it and was able to take some notes of features and indeed get a few photos. The lighting was absolutely nightmarish, but between tons of photos and a bit of tweaking of balance levels I have produced at least a few that are not too terrible, though at not very high resolution and mostly taken at a pretty low angle. Enjoy (as far as you can).
Tags: Dinosaurs, evolution, palaeontology, sexual selection
Those with an interest in dinosaur cranial crests and exaggerated structures (which should really be everyone since they turn up in pretty much every major lineage one way or the other) will probably be aware of the exchanges going on in the literature over these features. Although myself and colleagues have been advocating that sexual selection (and or socio-sexual signaling: the two can be hard to separate) is a likely strong candidate as the prime driver for many of these features, others have been advocating that this is not the case and instead the answer lies in species recognition. The latest to delve into this area is a paper I’ve done with Darren Naish and is the first time we’ve addressed this issue directly. While we have written or contributed to a number of efforts looking at support for sexual selection in dinosaurs, this is the first time we have tackled the other side of the problem.
The paper originally started as a long section that was included in our paper on mutual sexual selection with Innes Cuthill, but as we were later forced to cut down the length of the submission, this was a section that was relatively easy to prune as tangential to the main issue. However, we felt it needed saying and with new data coming out and the discussion ramping up, we revived and revised the work and it is now out. (Well, it has been in press and available for a while but is now properly out).
This is an important area for discussion – after all, the horns, crests, frills, plates, bosses and the rest (not least feathers) are key features and adaptations in various dinosaur lineages and trying to work out how they might have been used and what this means for evolutionary drivers and patterns is going to be a major issue. It’s hard to really understand stegosaurs or ceratopsians say if you can’t say that much with confidence about their ‘bonus’ features. While obviously each clade, or even each genus / species probably needs to be taken on a case-by-case basis when it comes to detailed analyses, some gross patterns can be seen or at least discussed. In the case of species recognition, is it even an actual ‘thing’ when it comes to exaggerated structures, and if it is, how is it supposed to work. The hypothesis has enjoyed some support in the literature for some unusual dinosaur features so it’s well worth examining.
Species recognition (in the context of exaggerated structures) for those who don’t know, is the idea that individuals of a species use these features to help them recognise cospecifics with to ensure they mate with the right species, or to maintain herd coherence. In short, carry round a key feature and you should be able to make it easier to stay in touch with the right animals and avoid the wrong ones. Various lines have been put forward to support this idea (in general and specifically towards dinosaurs) but we feel that none of them actually stack up and some have some serious problems.
First off is a pretty big issue – to our knowledge there is no evidence of any living species using some form of crest or exaggerated structure for species recognition. Individuals of species do recognise each other (not a big shock) but actually things like antlers or casques don’t seem to form part of the pattern that conspsecifics recognise. This may not be a big shock, after all, you can recognise a species by the overall appearance (size, shape, colour), their smell or specific sounds they make, behaviour, and other features. On top of this, some species are very varied in appearance for the big features (antlers of deer look very different as they grow, and are different between males and females and between juveniles and adults etc.) so relying on one feature is a bad idea at best, and a plastic one an especially bad call.
Plus of course, you often get closely related taxa that are sympatric. Is some big set of horns going to help you correctly identify conspecifics if there are half a dozen similarly-looking species also in the area? Look at things like African antelope and gazelle, or more extreme examples like tyrant flycatchers. We have trouble telling them apart sometimes based on their morphology, yet they seem to have no trouble. If this is so critical to dinosaurs, why to the iguanodonts seem relatively free of crests, but the hadrosaurs go nuts with them? And why are they all so similar in general form between species when they are supposed to help separate them out? Surely they should be divergent, not all similar in appearance. And why do we see things like Wuerhosaurus or Spinosaurus running around with all this weight to make sure they don’t mate with the wrong species when there are no other members of their clade to get confused with?
In some cases we see both issues coming together. If we look at the various small protoceratopsians of China / Mongolia, we see disagreement between researchers as to how many species (or genera) there may be. What is notable however, is that the characters being used to separate them out don’t typically involve the frill or bosses of the skull, and where they do, may be things that are not externally visible (e.g. the width of the media bar in the frill). In short – if there are multiple species here, the frills are apparently similar enough that we can’t separate them and so are unlikely to be part of the identity concept of the animals. If however, there is only one species present, then we are back to the paradox of a large frill being carried around but with no other species that could confound any signals.
On top of that, is it really worth it? After all, while you do want to stay in touch and make sure you mate with the right species, bolting on a good few kilos of bone to your head, and then the extra muscle to support it, and then lugging that around for your entire life is a lot of effort. When you can probably already identify conspecifics by their colour, patterns, scent and calls (of simply because nothing else like them at all is on the same continent) surely these would experience strong negative selective pressures if they didn’t have any other support.
Furthermore, how would such features ever evolve? If the populations / species were allopatric then we return to the situation of them not having another group to get confused with and crests are unnecessary for recognition. If they were sympatric though, how would this work? Pretty much the definition of a natural biological population is one that is breeding within itself, but here we’d have to have a population diverging because some don’t recognise each other as conspecifics even though we would expect, pretty much by definition, there not to be too much difference in structure shape between them (e.g. a tiny crest vs no crest). Now some animals might prefer each other, but that’s mate choice, not recognition, and there would have to be enough individuals for this to work – one mutant with a crest when no one else has one is not going to start forming a new species, and if there were a bunch of the with the new crest they’d also have to identify each other as different and avoid mating or hanging around with the others. So how would a large feature that’s for correct recognition allow a population to split in this way? To us at least it appears most unlikely to occur at all, let alone repeatedly.
In addition to this, there is rampant hybridization of closely related species in the natural world (and indeed in captivity). Even extravagantly ornamented species like pheasants with numerous adornments and bright colours and patterns hybridise regularly – clearly no matter how extreme the cue, at least some animals regularly have problems with them or are indiscriminate, but either way they are not that effective.
While some data like the apparent rapid growth of structures late in ontogeny has been used to support the idea that they are characteristics involved in socio-sexual signaling, it’s also a problem for the herd coherency part of the model. After all, lots of juvenile dinosaurs are known from aggregations suggesting they spent a lot of time together, even when the adults did not appear to. If these features were key, we’d expect juveniles to have them, and adult perhaps to shun them when they were no longer needed, but instead the opposite is true. In general the herd coherency argument is a bit odd anyway, again you have lots of ways of identifying and keeping in touch with conspecifics and some are clearly better than visual aids. Scent can have a temporal component, and vocalizations can be interactive beyond line of sight (especially useful in forests, or when things are behind you, or you are foraging and looking down etc.). No matter how big they are, visual structures are not always going to be that useful, even if they are unique.
In the increasingly infamous issue of Torosaurus and Triceratops, if these animals are truly conspecific then for a start we are back to the issue of ‘lone’ taxa (I don’t think Leptoceratops is going to be much of an issue here) and the pointlessness of crests where none are needed. On the other hand, this is also potentially a problem for the mate recognition idea. We know that at least some dinosaurs were sexually mature before they were osteologically mature and this could be the case for these animals too. If so, then the alleged transformation between one morph and the other would create confusion – both the Triceratops morph and the Torosaurus morph (or indeed anything in between) would be viable mates.
In short, we really have no clear evidence for species recognition in any living species, and that alone should make it unlikely to have been a key player across dinosaurs for the whole Mesozoic. Such structures would be costly, and yet not necessarily do the job it is supposed to with other signals being cheaper and just as effective, or more effective in many circumstances. It’s not clear why it should be so important for some clades and not other similar forms (iguanodotids vs hadrosaurs for example) and is clearly either redundant for some taxa, or would not actually reduce confusion. Nor is it clear quite how this would evolve in the first place, or why it would be sustained, and hybridization suggests that crests alone would not even prevent incorrect matings. Put this all together and we feel that there really is no good support for the idea of crests and other structures being primarily used in species recognition. They did of course likely have an effect – it would be odd if Stegosaurus or Corythosaurus didn’t use their respective features as part of how they identified one another. But that does not make them the prime, or only, driving force of all these different features in all these different lineages.
There was a fashion in dinosaur palaeo to write off any odd structure as simply sexual selection and leave it there. This was rightly railed against, but what was often criticised was the fact that sexual selection seemed undiagnosable in the fossil record and so the problem was that it was untestable rather than the fact that such throwaway remarks devoid of context or explanation do little for the subject. Now we are in the odd position where rarely you see very similar comments (in terms of their style) about species recognition popping up in the literature about exaggerated structures despite the lack of support for it, and the now (well, we think), strong cases made for sexual selection, or at least it’s assessment. Although previously the case for sexual selection was pretty weak, it is at least an extremely common phenomenon in living taxa and with obvious powerful effects on anatomy and behaviour. Species recognition has not yet even been shown (in relation to exaggerated structures) in any living clade, and while offhand one-line explanations are not the way to go, it seems odd that one has been replaced with the other.
Tags: dinosaur, theropod, tyrannosaur
Gorgosaurus has had a lot of love on here thanks to the huge series of posts on the preparation of a specimen by Darren Tanke, but also with this recent effort. Despite the awesome quality of those, this one is arguably better. While not complete (almost no tail dang it) and with a little bit of squishing to the skull, this one clearly retains an awful lot of the 3D relationships between bones and it overall rather uncrushed. This is a rarity to say the least and really helps show just how, well, big these things were. As you can see from the images, the animal is really barrel-chested and chunky. Obviously restoring muscles and fat layers etc. is another issue entirely, but I think it’s fair to say that this animal should really not be slim.
Obviously there’s a ton of just beautiful detail here and some lovely nuances (like the interlocking gastralia, the massively retracted left leg, the ilia tight to the neural spines of the sacrum, and the rugosities on the snout). It may not have quite the visual impact of the last one, but there’s really a lot to be gained from this and palaeoartists out there should be (t0 quote a friend of mine) onto this like a starving chihuahua on a pork chop.
Tags: blogging, outreach, tyrannosaurus
The next few days are likely to be very busy for me and this weekend I’m off on holiday, so I very much doubt I’ll be blogging on next Monday. This is a bit of a shame as those who occasionally glance at the bottom half of the sidebar on the Musings will realise that it pretty much marks the 5th anniversary of the blog. Of course very longtime readers will know I was going for some months on the old Dinobase site before cranking up this version on wordpress, but this has for most people always been the home of my pronouncements, even if there is also now Pterosaur.net, the Lost Worlds, and various bits on other parts of the web too.
So I’m naturally really rather pleased to have reached this mark, having also not too long past gone over 1.25 million hits and 1250 posts on here. It has, obviously, been a lot of work. While naturally there have been plenty of short posts (even one liners, and those of just a single image) and a fair number of guest pieces, I’ve obviously poured a huge amount of time and effort into this over the years, and I’d like to think it’s made a fair impression on a goodly number of people. Plenty of great dinosaur blogs by interesting and talented researchers seem to have fallen by the wayside, so if nothing else I can claim a fair bit of persistence.
Right, well to ‘celebrate’, here’s some pictures of a Tyrannosaurus mount from the Tyrrell that I was going to post anyway (so hardly the greatest party ever thrown really). Still, it’s hardly an inappropriate thing to include as I have done my share of tyrannosaur work and this is a neat mount. Oddly, I wasn’t too happy with the photos originally, you can’t see too many details, but I rather like the way this looms out of the murk with the animal trailing off into darkness.
Although the skull looks great from either side, once you get a shot up the nose, it’s rather clear how distorted this is. There’s quite a bit of difference between the two sides and it’s obvious there’s been a fair amount of squishing to the bones to give this rather asymmetric appearance.
Well, that’s it for now. Not sure if there will be another 5 years, but I’m not planning on stopping just yet and I’ll be annoyed at least if I don’t reach 1500 posts having gone this far, though with my other commitments, it may take a good long while yet.
Elaphrosaurus last got a mention here way back in 2009 when Limusaurus came out. In the phylogeny accompanying that paper, the two were recovered as sister taxa which hinted at the possibility that Elaphrosaurus was also herbivorous. Given that there’s no known skull, that’s not as outrageous as it sounds alongside this image – the head was reconstructed before Limusaurus was known. Whichever way it cuts though, this is a great specimen in great condition and a lovely mount that shows off the material. You can also spot a really quite hefty theropod femur in the case behind it as well – this might be the only vaguely-complete theropod from Tendaguru, but it’s far from the only theropod known.
I’m badly behind on the blogging here and especially covering my January trip to Berlin owing to a combination of illness, work and the Daspletosaurus project (only 3 weeks left!). Still, while there’s much more to come, I’ll grab a few minutes and post a little about the big bone store in the basement in Berlin featuring these wonderful containers (if you don’t know what they are, feel free to guess, answer at the bottom below the fold).
As briefly mentioned before, I’m just back from a week long trip to Berlin and the Museum fur Naturkunde (better, but now incorrectly known as the Humboldt museum). The last time I was there was around 2007 and the main dinosaur hall was empty with the material having been taken apart for remounting. So while I was there to dig into the collections and check out the material available, it was a chance to see how the new exhibits (plenty more than the dinosaurs have been done) look. I’ll stretch it out a little and break this up into various small slots covering different aspects of the exhibits and first off let’s not sidestep the obvious – they have a full sized, mostly real bone, mounted Giraffatitan. Yes this is a far from tiny mount, it’s absolutely colossal and that’s most apparent when you see that it’s next to Diplodocus (also shown at the top) – the sauropod that most people have probably seen in a museum and are most familiar with. Giraffatitan simply *towers* over this and in every dimension except total length is clearly a much, much larger animal.
The remounting here gives both of these animals a more ‘modern’ look and less tail-draggy and generally upright. One really nice addition is the cervical ribs being added to the G. mount, giving it a much more accurate neck and showing off this often missing (or badly handled) feature of sauropod necks. The third in the sauropod trio is the fascinating and short-necked Dicraeosaurus. Indeed, between the three, you have a really classic in Diplodocus, a real giant in Giraffatitan (and a very upright one to boot), and then a relatively small and short-necked animal in Dicraeosaurus. This guy does have a short neck, but look at the height on the cervical nerual spines and that lovely bifurcation into pairs of spines.
And finally as a little bonus, I took this one as it looked like a nice novel view, but on reviewing it in hindsight, it’s clearly in ‘Luis-Rey-O-Scope‘.
I’m just back from a quick visit to Berlin and so once I’ve caught up with all the usual stuff that gets behind from being away there’ll be some blogs coming on the exhibitions, Berlin Tier Park and others. Meantime though, here’s the Berlin Archaeopteryx. I have seen this magnificent and legendary specimen a couple of times before and have some old analogue photos, but now have some nice shiny digital ones to put up here. Oddly this is the one obvious specimen that’s been missing from my ‘collection‘. It has been on here before thanks to Heinrich Mallison, but now I can add my own shots to flesh this out with a couple more.
Today Scott Persons returns to the Musings to talk more about theropod tails, their musculature and possible uses. This time around, it’s the oviraptorosaurs:
Previously on Archosaur Musings . . .
After my first post on dinosaur tails (which was mostly focused on the rear-ends of tyrannosaurs), I was asked a seemingly innocent question in the comments section by archo muser “Lucy”. She wrote:
“So what about oviraptorids and their reduced tails – do we assume they went the same way as emus? And do we know anything about the other maniraptors (I’m particularly thinking of dromaeosaurs and their famously odd tail design)?”
I suspect no malice on the part of Lucy and her question, but her inquiry had inadvertently put me in a corner. She had asked a good question . . . so good that I had already devoted two chapters in my master’s thesis to thinking about it and had two papers addressing the question in the works. So, I had the wherewithal to answer it, and that was my dilemma.
I am of the opinion that science should not be a covert affair. New scientific discoveries should not be closely guarded secrets. By its very nature, science benefits from transparency and from the unobstructed flow of ideas. And yet, in the modern system of journal-based publish-or-perish scientific academia, a certain level of discretion and intrigue is prudent.
Otherwise, you might get scooped. You might prematurely tell one too many colleagues what you are researching and what your results are, and, next thing you know, those ideas wind up in someone else’s publication. Maybe that someone else was already thinking the same thing and, upon hearing that they are not the only one following that particular line of thought, they rush to publish first. That leaves you with an outdated thesis and nothing new to report (and the best academic journals don’t do reruns). Consider, as an extreme example, what Alfred Russel Wallace’s place in the history books would be if he had kept his ideas to himself until going to print and hadn’t sent a certain letter to a certain long-bearded British naturalist. And sometimes, of course, the scooping can be downright nefarious.
Not that dino tail research is a ticket into the history books (I am just happy when I get asked to do a guest blog), but what seems like your own quiet little corner of paleo research can get scooped out from under you. It has happened to some of my friends. So, I did not want to tip my hand and give Lucy the answer that her question deserved. Instead, with all the aggravating crypticness of a magic eight ball, I gave what I’m sure was a dissatisfactory answer. I said, in effect, “Why, yes, dromaeosaurid and oviraptorids do have unusual tails, and, yes, I do think they were specialized for unusual functions. I am going to publishing on those topics soon. Ask again later.”
Both raptor tail papers have come to academic fruition, and I am now free of my research paranoia. The paper on dromaeosaurids (coauthored with my graduate supervisor Dr. Phil Currie) has been published in a special volume of Acta Geologica Sinica, and the paper examining oviraptorid tails (coauthored with Dr. Phil Currie and Dr. Mark Norell) is now available for early view in Acta Palaeontologica Plonica. If you are interested in what I think was going on with dromaeosaurid tails (and I think a lot was going on), then you can checkout the guest post that Dave asked me to do over at Pterosaur.net. That leaves us with the tails of oviraptors . . .
“Do we assume they went the same way as emus?”
Oviraptors have short tails (both in terms of the total number of vertebrae in their tails and in terms of tail length relative to body length). It has been argued that such short tails are evidence that the group did go the way of the emu — i.e., the ancestors of oviraptors had reduced tails for the purpose of flight and that this reduced-tail condition was retained after the group had become secondarily flightless. In fact, it has been argued by various scientists that many groups of fully-terrestrial dinosaurs may have descended from flight-capable ancestors. It is my opinion (though many wise and respectable scientists would disagree) that some of these arguments for secondarily-flightless dinosaurs are probably valid. However, in the case of oviraptors, I don’t think that the tail lends much support to the secondarily flightless hypothesis. Let me tell you why.
Those readers who made it through my first tail post will recall that I am interested in the musculature of dinosaur tails (as inferred through digital reconstructions based on skeletal attachment sites and comparative dissections of modern animals). In particular, I am interested in the caudofemoral tail muscles. Caudofemoral muscles are part of the locomotive system. They attach via tendon to the femur, and their retractions helped to propel a dinosaur forwards when walking and running.
In birds, the caudofemoral muscles are tremendously reduced and sometimes completely absent. That makes sense. To fly, a bird benefits from weight reduction, and what better weight could a bird reduce than that of a big muscle dangling off the rear that functions in land-based locomotion. Emu’s have reduced caudofemoral muscles (they compensate for this, as many birds do, by placing less emphasis on femoral retraction when they walk and run), but there is every indication that oviraptors did not have reduced caudofemoral muscles.
Readers of my past post may also recall that caudofemoral muscles do not extend too far back towards the tip of the tail. Instead, most of their mass is located near the tail base (by the hips and legs). The shortening of oviraptor tails appears to have been restricted to the post-caudofemoral region of the tail – that is, vertebrae near the tip were lost — and I found no evidence that the caudofemoral muscles of oviraptors were reduced. Oviraptor tails were shortened, but not at the expense of muscles that helped them to move on the ground. Not like an emu.
Curiouser and Curiouser
What about the other tail muscles, are they reduced? Yes, and no. The other muscles of an oviraptor tail are considerably reduced in relative length, but not in relative mass. Wide caudal ribs (transverse processes), among other features of the tail skeleton, affirm that oviraptors had unusually robust tail muscles. Oviraptor tails were short, but stocky.
In an oviraptor tail, the individual vertebrae were short and the vertebral articulations suggest a high degree of flexibility in between the vertebrae. So, oviraptors had a lot of flexor points crammed into their short stocky tails. Per unit of tail length, an oviraptor tail may have rivaled all other theropods in its flexibility.
Then, we come to the very tip of the tail, and that’s when things really get strange. Back in 2000, it was announced that the oviraptor Nomingia had a tail that terminated in a series of fused vertebrae. This fused terminal tip was termed a “pygostyle”. Pygostyles are found in the tails of modern birds and are thought to be associated with anchoring a bird’s fanning tail-feathers. Did Nomingia have a tail feather fan? It seems likely. Direct proof that some early oviraptors had tail-feather fans comes from exquisitely preserved specimens of Caudipteryx and Similicaudipteryx, which actually have fossilized feathers preserved.
In our oviraptor tail paper, my coauthors and I announced the discovery of three new oviraptor pygostyles. One of these was from a second specimen of Nomingia, one was from Citipati, and one (the smallest of the three) was from Conchoraptor. These new pygostyles suggest that Nomingia may have been the rule, not the exception, and that pygostyles along with their accompanying feather fans were probably common features of oviraptors.
If You’ve Got It, Flaunt It
Muscular, flexible, and ending in a feathered flourish, what were oviraptor tails doing? I think they were flirting.
What good are tail feathers if you cannot fly? A lot of modern birds make use of tail-feather fans when they are on the ground. Think about a tom turkey or a peacock. Such birds use flamboyant feather-fans as display structures, most commonly, as courtship display structures. Now, imagine if the avian ancestors of peafowl and turkeys had not been forced to abandon the longer and muscular dinosaurian tail for the sake of aeronautics. What sort of a tail might these birds “want” in order to best woo potential mates and to wield their feathery instruments of seduction? Flexible, strong, and muscularly dexterous tails.
Lucy, I want you to know that this follow-up blog post was unsolicited. I trust that Dave humors me and posts it, and I hope you are satisfied with the answer. Sorry for the delay.
Tags: claws, Dinosaurs, ecology
In the last couple of weeks I’ve had two papers come out in PLoS ONE tackling different aspects of dinosaur ecology. In rather different ways both look at the morphology of various living clades and use that to build up an idea of what patterns are present and how dinosaurs fit into this.
The Musings is set more or less to idle these days, so I don’t want to say anything too extensive here, not least when I have blogged the most recent paper already on the Lost Worlds and Darren Naish has some very extensive coverage of the first one. Still, I don’t want this one to dry up entirely and with a dinosaur-keen audience, it seemed a good idea to get up at least a quick post on the two.
First off there’s a paper on claw shape and how this might, or might not, relate to possible climbing functions. The major results are somewhat equivocal. Perhaps unsurprisingly, there is a lot of variation in claw shape (curvature and midpoint dorsoventral height) and that means the boundaries are blurred between those animals that climb from those that are predatory or based on the ground. In short, for most it’s hard to make any kind of confident predictions off of our analysis at least, but there is a lot of scope for further work, and at least some dinosaurs plot out clearly in one behavioural category and well away from the others.
Second, there’s the piece on dinosaur body size distribution. Here non-avian dinosaurs are shown to have a different pattern of body size distribution to various vertebrate clades both living and extinct, with dinosaurs having relatively few small species and a high number of large ones. This nicely fits with the idea that dinosaurs filled multiple niches as part of their ontogeny, with niches for small species being filled by juveniles.
I’ll keep it short and sweet with both being freely available to read as obviously all the details are in there.
Birn-Jeffery, A.V., Miller, C., Naish, D., Rayfield, E.J. & Hone, D.W.E. 2012. Pedal claw curvature in birds, lizards and Mesozoic dinosaurs – complicated categories and compensating for mass-specific and phylogenetic control. PLoS ONE, 7: e50555, 11p.
Tags: evolution, fossils, palaeontology, review, sexual selection
Regular readers will know that for the last few years I’ve been slowly building a research profile concentrating on the behaviour and ecology of dinosaurs and pterosaurs. While the various papers on feeding behaviour, stomach contents, predation and niche partitioning in theropods has been the more high profile, I think the work on sexual selection is arguably more important as it potentially has profound implications for how we interpret all manner of fossils and how they may (or may not) relate to one another. After all, there’s a major ecological and taxonomic difference between identifying two species of a clade, and one species that exhibits major sexual dimorphism.
My colleagues and I have already looked at the idea that sauropod necks were driven by sexual selection, and after much strife, finally got a paper published discussing mutual sexual selection and the implications that has for diagnosing taxa in the fossil record and what it might mean for parental care and other aspects of behaviour. There’s more to come in these areas as I have further work planned and am involved in some other areas linked to this, so the area is growing rapidly and, I hope, ripe for a general revisit in the literature. However, while these papers have in large part being about drawing out some false assumptions in the literature and providing new hypotheses about sexual selection that could be looked at in the fossil record, they were a bit short on how this could be done, and were if anything, narrow in focus (not that Ornithodira is a small group, but its got nothing on Animalia).
So then to a paper in TREE that came out yesterday online. Led by entomologist Rob Knell, it also includes Darren Naish and myself and attempts to provide a review of the entire question of sexual selection in the fossil record. We look at ways in which this could be diagnosed, some false dichotomies and assumptions that have been put forwards in the past, try to identify some key features that may help diagnose sexual selection and look at some of the more convincing cases for this that have been put together to date. Clearly there’s a limit to what we can get into under 10 pages for what is supposed to be a review, but I think there’s some nice synthesis in there and a bit more “we can try doing this”-type stuff, that just covering what has been said before. Anyway it’s out and available (though behind a paywall, sorry) so go take a look.