Wednesday 2 October 2013

What neck-biting Tyrannosaurus sex tells us about speculation in palaeoart

Head and neck biting sexual behaviour in Tyrannosaurus rex. A novel, brutal and undeniably speculative reconstruction for tyrannosaurs, sure, but is it the result of pure, unbridled palaeoartistic license, or is there something more to it?
It seems that "speculation" is the current word on everyone's lips in palaeoartistic circles. Thanks largely to the enormous success of All Yesterdays, and the recent unveiling of its sequel, All Your Yesterdays, palaeoartists across the internet have been buzzing with excitement over the possibilities opened by speculative leaps of logic. This is undoubtedly a Good Thing. I wrote almost a year ago about why I thought All Yesterdays and the ideas it embodied were great, and a must-see for anyone interested in vertebrate palaeontology or palaeoart. I stand by that, and am certain that many of us in the palaeoart community have be positively influenced by this project in the way we recreate extinct species. All Yesterdays revelled in speculation about prehistory, arguing that we were not being open-minded enough about our depictions of animal appearance and behaviour. The crux, as anyone reading this probably knows, is that many 'traditional' palaeoart concepts are likely erroneous by being overly conservative, and thus 'fail' at both restoring ancient life and producing convincing looking animals. In addition, All Yesterdays highlighted a number of conventions which had become tropes within palaeoart, and argued palaeoartists produce far more accurate studies of extinct life when these clichés are broken, not to mention more interesting ones. What gave All Yesterdays such a strong message was that it, for the most part, was scientifically sound, cleverly turning conventions on their head or showing us logical, plausible ancient phenomena that we'd not imagined before.

For the All Yesterdays sequel, All Your Yesterdays, we see a minority of palaeoartists reaching further than it's predecessor dared, showing some very elaborate anatomies and lifestyles which may, in my opinion, go further than reasonable inference, even enhanced with speculation, may allow. Before we get any further, I want to stress that this post is not a review of All Your Yesterdays. I enjoyed the book, and think it's well worth seeking out for a look at for some excellent and thought provoking imagery. But yes, it does contain a few images which made me question this newfound speculative approach to palaeoart. We have to bear in mind that All Your Yesterdays was crowdsourced, the result of a contest for "original, creative concepts that are at least partially in-line with our current understanding of extinct animals" from Irregular Books. This is naturally going to draw a range of knowledge bases, some of which may be more comprehensive than others, and it may be that some of the more eyebrow-raising images therein are simple mistakes. I'm not going to name names here, because I gather the artists behind All Your Yesterdays were not aware that their work was going to be showcased as a 'significant' addition to the All Yesterdays canon, but I'll hint that molluscan salinity tolerances, the nesting habits in pterosaurs, the soft-tissues of spinosaurids, hadrosaurs and thyreophorans, and the evolution of viviparity were just some things which prompted this post. It's important to stress that problematic 'overspeculations' are not confined to a few pieces in All Your Yesterdays, but a small but noticeable chunk of post-All Yesterdays palaeoartworks which, arguably, jump the palaeoart shark. It's these artworks I want to focus on here.

Getting introspective with speculation
Chiefly, some artwork inspired by All Yesterdays seems to take license for increased palaeoartistic speculation as a sign that 'anything is possible in nature', without any real consideration for how likely some possibilities are. Other pieces showcase strange anatomies for the sole purpose of contrasting with more traditional standard depictions, without considering why such reconstructions are common in the first place. These works, presented as part of a movement that I think I understand and agree with, have gone beyond the science which has to underpin any recreation of an extinct being. The question is, how much speculation we can use before our work stops being palaeoart and starts being fantasy images starring extinct species?

Detail of neck biting Tyrannosaurus. I'm sure he's got a great personality.
Of course, I'm not the first person to ponder this. Indeed, the inspiration for this post, All Your Yesterdays, muses on this same issue:
"In short, speculation in palaeoart should be seen as a sliding scale. At which point does a speculation render itself too extreme? And is it even possible to reach said extreme given the ridiculous soft tissue structures and absurd behaviours present in the modern world? It is, in fact, surprisingly difficult to come up with a speculative piece of palaeoart that is unconditionally ridiculous (at least, so long as the basic rules of anatomy, biology and physics are applied, as they are in science-based reconstructions)."
All Your Yesterdays, p. 7  

These words contrast with a few comments online. Amid the near-universal acclaim for All Yesterdays, one or two (and three, four, five) folks have made about palaeoartistic speculation running away with itself, a far cry from the suggestion that palaeoart can never, so long as basic science is followed, be too ridiculous. It seems there's some need, then, for discussion about the appropriateness of speculation in palaeoart: how it should inform our work, how far we can take it, and whether all speculations are equal. After ruminating on this for a couple of days, it seems that the best way to tackle this is by dividing palaeoartistic speculation into three categories (as with any classification of an organic, creative process, are best perhaps viewed as major points a continuum), which I'll call primary, secondary and tertiary. These distinctions effectively denote how far depicted ideas stray from actual data. We'll outline these types of speculation first, and then discuss their use below.

Primary speculations
Speculations directly based on fossil data, whereby the evidence for a behaviour, event or anatomical feature is reasonable, but details may be murky and require some imagination to restore. Gut content, pathological bones and complex track sites are good examples of evidence which can be used to inspire palaeoart using primary speculation. We may not know the entire truth behind these fossils, but we can whittle it down to a few very likely possibilities. Basic elaboration of predicted integument of an animal - making fluffy integuments long or short, altering distribution and so forth - would be an example of primary speculation on anatomy, as would adding things like wattles, skin-folds and other likely anatomical details to reconstructions. With primary speculations, we can be more-or-less entirely confident that we're displaying a degree of truth in our work.

Secondary speculations
Speculations not directly supported by fossil data, but operate within our spectrum of knowledge to maintain a degree of plausibility. This may include extrapolation of common behaviours and, to a limited extent, elaborate anatomies from closely related animals to reconstructed species. Extrapolating some behaviours from or close ecological, anatomical or biomechanical analogues may fall into this camp too. Ritualised behaviours (below), unusual ways of dying and foraging on unexpected food sources are good examples. Depicted behaviours may serve to show the function of prominent anatomies. Slightly unusual interpretations of integument and other body tissues (perhaps as responses to climate, seasons, sexual selection etc.) probably fall into this category, so long as they are consistent with the integuments known within a 'reasonable' phylogenetic bracket. In short: speculations which adorn fossil species with features so fundamental to animal existence that, even in the absence of fossil data, we can be confident they occurred in deep time.

Ritualised courting chaoyangopterid pterosaurs, Lacusovagus magnificens. Did pterosaurs do this? There's no direct fossil evidence for it, but the abundance of ritualised mating behaviour in modern animals suggests we can be relatively confident that they, and other fossil species, used complex ritualised behaviour. This undoubted speculation gains indirect support from the broad array of sociosexual devices we see on many fossil species, and hints of ancient sexual dimorphism, both of which indicate sexual behaviours were as complex and sophisticated in prehistory as they are today. Image from Witton (2013).
Tertiary speculations
Speculations operating completely outside, and sometimes contradicting, fossil data. May rely entirely on application of very specific modern animal behaviours and anatomies to fossil species, often transferring rare, sometimes highly specialised lifestyles to fossil animals. There is no particular logic or reason behind these applications: they are entirely arbitrary. In other cases, complex biologies and life histories are invented for fossil taxa. Creation of soft-tissue anatomies without, or in spite of, consideration of underlying musculoskeletal system and/or soft-tissue fossil data. Reliant on the absence of data concerning fossil species, because 'anything is possible'. Hypothetical examples of such speculations are things like lactating dinosaurs, notosuchians with trunks, an egg-laying Deinotherium, hadrosaurs with antler-like structures growing atop their crests. Jaime Headden's woolly ankylosaur, his cautionary 'mess of speculation', is a knowing graphic example of tertiary speculations gone mad.

Speculations, what are they good for?
If these are the tools of the speculative palaeoartist, what are their application? Anyone familiar with palaeoartistic practises will recognise that the former two grades of speculation are standard tenets of palaeoart. Such speculations provide our leaps of logic into prehistory and, without them, palaeoart would be an pretty limited endeavour, probably entirely formed of musculoskeletal reconstructions. It's important to recognise that such speculations were not originated by All Yesterdays, as primary and secondary speculations have always been used in palaeoart. The masterstroke of All Yesterdays was to show how primary and secondary speculations could be bolder and more imaginative than most mainstream palaeoart suggested. The result is artwork which is both interesting, unique and supported by actual data.

The image at the top of this post is the result of such an inference. It's well known that many large theropods engaged in head-biting behaviour, and some specimens of Tyrannosaurus (including BHI 3033, better known as the common T. rex museum mount 'Stan') bear particularly extensive damage to their posterior skulls. The inference made here is that Tyrannosaurus engaged in aggressive head and neck biting during copulation, a widely seen behaviour among vertebrates that can often involve substantial damage to the head and neck of the female, sometimes leading to death. I'm not the first to envision this behaviour for tyrannosaurids. Tanke and Currie (1998) suggested nuptial biting as a cause of tyrannosaurid head pathologies but suggested it was refuted by the apparent small size (50% of full size) of many tyrannosaurids with head wounds. Of course, it now seems that dinosaurs became sexually mature when only half grown (Erickson et al. 2007), so this hypothesis may be back on the table. The resultant image is a radical and speculative depiction of Tyrannosaurus behaviour, but one that has a foot firmly set in science.

Cast of the skull of Tyrannosaurus 'Stan', BHI 3033, at in the Oxford University Museum. Stan's skeleton is particularly damaged around the posterior head and neck region, with a probable tooth wound penetrating it's braincase, a smashed postorbital bar (a dorsal projection of tyrannosaur skulls which anchored neck muscles) and broken neck vertebrae. Photograph by Marc Vincent, from Love in the Time of Chasmosaurs.
The same cannot be said for tertiary speculations. Some inferences made at this level are so far removed from actual data that they have little or no evidence to support them, and thus abandon the scientific basis which should underpin any palaeoart. Others may disagree, but I think good palaeoart, like good science, is led primarily by evidence, not speculation. This most obviously impacts tertiary speculations which arise, it seems, for the sole purpose of overturning convention. "This animal is always shown like/doing this... what if it looked like/did THIS SHOCKING THING?!??" While there's nothing wrong with trying to keep palaeoart fresh, we should remind ourselves that not everything common in palaeoart is a trope or meme, or the product of unimaginative artists. Sometimes, that's just how animals were, and conventions are based in very sound evidence. Deviating from these conventions is a move away from data, which is the exact opposite of what we want to be doing here.

Other tertiary speculations apply highly unusual behaviours borrowed from modern animals, or those which are entirely made up, to fossil species for no clear reason. This can be effective on occasion, presenting a fossil species in a radical light which may make us reconsider our preconceived notions of that species, but I'm generally not a fan. Why, of all the behaviours that we can imagine or observe in in the modern day, should we chose that specific animal as a model? And do we really expect the rarest, most elaborate and weirdest behaviours to be present in specific fossil animals? Are we actually predicting that extinct animals behaved (often adorned with the same colour schemes and patterns) exactly like these aberrant modern animals? We'll score far more science points if we apply more widespread behavioural phenomena to our palaeoart. This doesn't mean we have to confine ourselves to dull behaviours like travelling and foraging, because we can also rely on primary and secondary-level speculations to give us behaviours like resting, taking care of personal hygiene, reproducing, interacting with one another and so on. Likewise, lots of interesting anatomies can be extrapolated from the fossil record itself. In sum, while we should take inspiration from modern taxa, arbitrarily 'transforming' fossil animals into ancient versions of modern species stretches credibility quite far, and is perhaps a rather unscientific approach to our work (this point echoes one made earlier, also in response to some art in All Your Yesterdays, at Laelaps).

A counterargument could be made that tertiary speculations allow us to imagine how sophisticated and complex ancient worlds were but, again, I question this. Like any guesswork, they're of questionable significance. Unknowns are unknowns. Tertiary-grade restorations are as likely to be incorrect as accurate. These depictions may fire the imagination briefly, but the flames are tiny compared to those fuelled by cool ancient behaviour derived from actual evidence. It's one thing to see a shocking piece of palaeoart, but quite another to realise that there's actually tangible evidence behind it. Rather than pondering the great unknowns of deep time when confronted with a tertiary speculation, I frequently react with the opposite approach, thinking about what we can actually deduce about a given issue, and what a more likely interpretation may be.

Why I find tertiary speculations frustrating. The fossil record is full of interesting animals with known interesting behaviours, like these burrowing Oryctodromeus, and yet they are frequently overlooked in palaeoart for entirely speculative renditions of familiar taxa. Check out this post for more on this animal and it's need for a PR campaign.
This brings us to a more pragmatic bugbear about tertiary speculations. Extremely speculative palaeoartworks are actually fairly common, at least online, while innumerable cool palaeontological topics with a significant factual basis are completely ignored. Why use art to make rather hollow points about unknown topics when there's plenty of art to be made concerning subjects we do know about? Even familiar animals have unusual, rarely-depicted behaviours which we can infer from fossils with minimal amounts of speculation (such as the tyrannosaurs above), not to mention the shedloads of fossil species which are wholly unrepresented in art (and yes, I'm well aware of the hypocrisy of saying this in a post featuring Tyrannosaurus), many of which are also known to have interesting and unusual behaviours. Heck, it's common knowledge that palaeoart is heavily biased towards a few taxa, so just showing some of these rarely seen animals would be a thought-provoking, cliché-busting achievement in itself. Is it not better, as scientific illustrators, to base our work on what we know rather than what we don't?

Which leads to...
So, yes, despite being an advocate of using speculation in palaeoart, I'm not a huge fan of the extreme and uncontrolled speculation we're seeing creeping into modern portfolios. This may sound like I'm jumping off the All Yesterdays bandwagon, but I don't think I am. Most of our best palaeoartists - including those behind All Yesterdays - use speculation of primary or secondary grade, and are more notable for avoiding clichés and artistic conventions than they are for presenting highly speculative lifestyles and anatomies in fossil species. They elaborate existing knowledge to create more convincing depictions of fossil animals, and apply detailed research of the fossil record to show us sights we've never seen before. Some of their work may seem outlandish and brash, but it's actually far more measured than it looks.

I'm sum my point up as this. While we should be using speculation to push palaeoart to its limits, we need to know both which bits we can push, and when to stop before our speculations get the better of our work. This doesn't deny us licence to make our reconstructed ancient worlds amazing and interesting and, in fact, it may make our work more striking. It's one thing to see an outlandish reconstruction of the past, but all the more poignant when we realise the weird, strange or even shocking visage before us is based on truths, and not just imagination.

  • Erickson, G. M., Rogers, K. C., Varricchio, D. J., Norell, M. A., & Xu, X. (2007). Growth patterns in brooding dinosaurs reveals the timing of sexual maturity in non-avian dinosaurs and genesis of the avian condition. Biology Letters, 3(5), 558-561.
  • Tanke, D. H., & Currie, P. J. (1998). Head-biting behavior in theropod dinosaurs: paleopathological evidence. Gaia, 15, 167-184.
  • Witton, M. P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.


  1. Great Post, Mark. I 100% agree with what you've stated here. I'm all for speculation as a form of hypothesis and expanding our perspective when looking at evidence, but when people start doing outlandish things JUST to be outlandish, or just because other (often specialized) modern animals do similar things, it takes me out of it.

    I fully suspect that many extinct animals did some really weird things, or had strange structures and goofy appearances, many of which we will never ever know about, but I highly doubt a lot of them were these exact duplicates of specialized modern animals.

    While I think the first "All Yesterdays" did a pretty great job, and only found myself thinking "eeeeh, i'm not sure about that..." for a few illustrations, I found myself thinking this much more often with "All Your Yesterdays." There are definitely some excellent works in that collection as well, and some people definitely get it, but others seem to have depicted weird things for the sake of it. What I wonder is, if the extreme speculation in some of these pieces was prompted by the illustrations being the result of an art contest? There may have been more of a push for weird/unusual to stand out among the other contestants.

  2. I agree wholeheartedly with this post as well. I think that the All Yesterdays movement is really valuable for getting people to think more "outside the box" and get away from tired paleoart tropes, and the original book was wonderful. I quite like the new one as well, but I suspect the movement for a lot of people has become a challenge to find the most outlandish thing possible, or to just copy the appearance or behavior of a number of extant birds. I very much prefer "primary" and "secondary" speculation in my own art, which is the umbrella that my three submissions to AYY fell under. Primary speculation is probably my favorite area to dabble in, because it always holds the promise of a possibility of being proven "right" someday.

    1. Something else to keep in mind is that really robust primary and secondary (especially primary) speculation requires a deeper knowledge of paleontological research and information than tertiary, which not everyone has access to.

    2. That's a very good point, Emily. I'd imagine there are people who think up their concepts before researching specifics on the animal being depicted, or after having a concept, might not put the time to find an animal that could more plausibly match said concept.

      Basically, one should at least have a certain baseline understanding of animal anatomy, behaviour, and evolutionary phylogeny before attempting to rock the paleoart boat.

      Of course then you get into the issue of availability and distribution of information and whatnot, which we all know is a whole other can of worms... but if one is truly serious about paleoart then (s)he will find a way.

    3. Thanks for the comments, chaps.

      "Something else to keep in mind is that really robust primary and secondary (especially primary) speculation requires a deeper knowledge of paleontological research and information than tertiary, which not everyone has access to."

      Yes. I actually mentioned this in a draft of the post, but removed it in a futile attempt to keep things short. While this is a problem, things are getting better with Open Access publishing, some kickass palaeo blogs, and some top-notch recent books which are very handy for artists. The situation is far from ideal, but it's better than it was, and still improving.

      "Basically, one should at least have a certain baseline understanding of animal anatomy, behaviour, and evolutionary phylogeny before attempting to rock the paleoart boat."

      Yes to this.

  3. I agree (even though I was guilty of making what is probably a tertiary reconstruction myself that's in the new book!). I make sure to stress alongside it that there is currently 0 evidence supporting the reconstruction. I think most of my reconstructions tend to be on the conservative side, actually. I appreciate when paleo-art is interesting and new but it should still be logical!

  4. A nit: "All Your Yesterdays was open-sourced". I think you mean crowdsourced.

  5. Hmm. I'm not sure how much I agree here. Of course speculation can extend to the point where it's completely unsupported. But I'm quite happy seeing specific modern-animal behaviours depicted in ancient animals. After all, the alternative is that they not be depicted, which implies they never happened, which is almost certainly false. Yes, it's unlikely that any given taken engaged in a given strange behaviour -- say, the play depicted for Ambulocetus, or the tree-pushing depicted for Tyrannosaurus; but it's likely that something did these things, and I'm not going to argue that the behaviour must go unillustrated because we can't reliably guess which animals did what.

    The few places where I do lose patience with All Your Yesterdays are where it veers off and depicts animals that never existed at all, like Simon Roy's Cyclops and retro-dinosauroid tribesmen. Saying nothing about the artwork involved, I think AYY would have been stronger without such pieces. (We could term those quaternary speculations).

    1. Thanks for the correction and comment, Mike. I guess my concern is that art which even only stands as a 'representative' for highly specific modern behaviours is that it robs uniqueness from both species. For all we know, some behaviours are completely unique to extant species. I emphasise that my interpretation of 'secondary' grade speculation does allow for a broad remit of behaviours. My problem is when we show those behaviour imitating the precise details of similar acts in modern taxa, rather than giving room for the uniqueness of both species to shine through.

      And yeah, the entirely fanciful reconstructions in All Your Yesterdays did jar with the rest of the book. A project dedicated to some of the truly archaic, incorrect and just plain crazy renditions of ancient taxa may be fun, though.

  6. Damn it Mark, I was hoping to stick my blogging oar in on this one, but you've not only made such a post completely redundant, you've used one of my photos to boot ;)

    Agreed on all counts, I think. What struck me particularly was that some of the soft tissue reconstructions were just as silly as the 'trunked sauropods' that a certain D Naish spent so many words deconstructing.

    1. Excellent: my plan to completely undermine your future post has succeeded. Stealing imagery was just to rub salt in the wound, of course (and, er, because all my photos of the same museum display are a bit rubbish).

      "What struck me particularly was that some of the soft tissue reconstructions were just as silly as the 'trunked sauropods' that a certain D Naish spent so many words deconstructing."

      Yup. Without singling out any particular imagery, there's definitely some artworks in All Your Yesterdays which don't meet the criteria mentioned at the start of the book, which is that they all obey basic rules of anatomy and biology.

  7. I apologize in advance if this question doesn't contribute much to this discussion, but where do you think the idea of Quetzalcoatlus northropi being able to skewer its prey on its beak would fit into this spectrum of speculation? It seems like it would be somewhere in between primary and secondary speculation, because while there is no direct fossil evidence of this happening, the beak of Quetzalcoatlus sp. does taper to a very sharp point. Some species of heron are known to be able to skewer their prey on their beaks, and their ecological niche is somewhat similar to what Quetzalcoatlus' niche may have been, herons being wading birds notwithstanding.

    1. The question here is kind of relevant actually, because it's a scientific question being asked in a palaeoartistic context. In that respect, it mirrors the way that many, if not most, ideas for palaeoartworks are generated. To assess how speculative a picture of prey-skewering azhdarchids would be, we need to look at a couple of bits of fossil data, which would be the next step in constructing this hypothetical bit of palaeoart.

      First up, we have the skull shapes of azhdarchids. The beak tips of Quetzalcoatlus aren't terribly well preserved, but they probably do taper to a relatively fine point. They aren't quite as robust as those of herons, though, with the lower jaw particularly slender, particularly around the back end where the impact forces will be transmitted to. My hunch is that the mandible wasn't really up to violent actions like skewering, because it's pretty dainty. Some other azhdarchid jaws appear proportionally more robust, but they're also not as pointy and spear like. Note that we don't know anything about the jaw tips for Q. northropi, because we don't have any skull fossils for this species.

      The skull is only one thing we need to look at, however, because the neck will be delivering the force required to penetrate the prey animal. Azhdarchid necks are pretty inflexible (see images and discussion in this post for details), which contrasts starkly with the uber-flexible and specialised necks of herons. Herons, like many birds have segmented necks with a specialised 'hinge' vertebra at their mid point, which permits the formation of that classic 'Z' neck profile. It also allows the neck to be used for precision, high-velocity strike feeding, the neck uncoiling under the same functional principle as a striking snake. The speed afforded by this strike, as you point out, is sometimes forceful enough to spear prey rather than merely grab it (which, I believe, is more often the intent). The limited motions of azhdarchid necks aren't going to allow for such precision strikes or accelerations, and appear poorly adapted for heron-like strike-feeding. Moreover, azhdarchid necks connect with the underside of their skulls, whereas heron necks attach at the back. This turns the head of a heron into an effective spear, projecting forward in line with the uncoiling neck action. Azhdarchid heads on top of their 'striking' necks, by contrast, would act like crude pickaxes.

      Of course, these are only hunches, but I would say that the anatomical similarities between herons and azhdarchids are only superficial, and differ in critical ways when comparing foraging techniques. If I'm right, this would imply that the proposed palaeoart is not really supported by fossil data, and that any rendition of it would be tertiary speculation.

  8. Mark, I was wondering where you place your muskox Pachyrhinosaurs under this system. For the most part they seem to fit comfortably under secondary speculation, but you do make a point about applying modern-day appearances and behaviors to extinct species.

    1. Far end of secondary speculation, I reckon, for two reasons. On the appearance front, I don't consider the animals in that image to be honorary muskox. There are similarities, sure, but there's only so many looks a shaggy, big-headed quadrupedal animal standing in the snow can take. I guess I could have changed the colour of the fuzz to something less muskox-like, but the colouration of the heads and limbs, and the flash of white along their flanks are features not seen in muskox. The fact we can see all the pachyrhinosaurs end-on doesn't help, I suppose, because that's probably the view that they'll look most like muskox in.

      Secondly, I think there may be confusion of 'behaviour' with 'adaptation' here. The image doesn't show pachyrhinosaurs specifically living like muskox so far as I can see. They share adaptations to a cold climate because developing a insulating coat is a common adaptive response to colder conditions in amniotes, but that's about it.

  9. Since I got name-dropped (after a sort) I'd like to point out that elaboration of features which don't readily fossilize, or cannot be directly inferred belong on the secondary speculation angle. This includes wattles, or the general bagginess of portions of skin in general, as well as eye color, nostril size (the fleshy portion), and even precise coloration with yellows and reds, colors deriving from pigments rather than melanosome shapes/frequencies. I might speculate that the little "abelisaurid" Kakuru kujani was colored as brightly as a bird-of-paradise, but that won't make it possible for me to qualify this.

  10. The mating T. rex picture is beautiful, as was your previous one of the red rex standing on its own. It's great to see the gross morphology of T. rex depicted accurately, especially the head shape; makes a nice change from most of the book illustrations I grew up with. The one thing I'm struggling with is the position of the mating rexes, with the female supporting so much weight with her legs. I would find the image a lot more believable if she was lying on her front, as female ostriches do when mating. I'm not claiming any knowledge of T. rex leg strength or the positions they could get their bodies into, it's just my gut feeling looking at the image.

    1. Thanks for the nice words Ictonyx. I didn't know ostriches assumed that posture when mating: very interesting. If my estimates of proportions are correct, the male here can just about reach the floor with its right foot which may help take some of the weight off the female and, though it's not a 'nice' thing to do, here head is being forced to the floor here: maybe that can absorb some weight too. In my mind, though, the actual act is still being arranged, as it were: there's still a bit of jostling to be done before these two get comfy. But yes, it would be interesting to leave the 'standard' poses of mating dinosaurs to explore other possibilities suggested by modern animals.

    2. As usual, I'm relatively late to the party. Anyway, I have 2 questions:

      1stly, what do you think of my "Anting Alvarezsaurid" (,1720.0.html ), speculation-wise? I like to think that my reasoning is, at the very least, secondary, but wanted to run it by you.

      2ndly, would neck-bite mating work for a species in which the female is larger than the male? I ask b/c, among the animals I've heard of neck-bite mating, the male is larger than the female. I figured this would be important for paleoartists to consider, given the probability of hypercarnivorous predatory dinos (like hypercarnivorous predatory birds) having reverse sexual size dimorphism.

      BTW, in reference to what Ictonyx said, I thought I'd share the following quote & this image:


      Quoting Larson/Donnan ( ): "Sue has a pathology on the top side of her tail — several bones are injured and healed, even almost linking together because of an injury. I think this injury might be due to how T. rex had to mate! The male would have rested on her tail, and he would have been very heavy!"

    3. Hi Raptor_044,

      Nothing wrong with ant-eating alvarezsaurids in my view. Probably would be a secondary tier speculation, but so are most things in palaeoart.

      I'm not sure that reverse dimorphism will really affect neck biting behaviour that much, although I'd have to check. I would, however, be wary of saying that predatory theropods 'probably' have reverse sexual size dimorphism. This is nowhere near as clear cut as some suggest. Our ability to identify gender in fossils is poor, as is our understanding of intraspecific variation in a lot of species. For example, we cannot distinguish between effects of dimorphism and geographic/temporal variation in species morphology for most theropods. Mostly, we collect individuals of the same species from distinct horizons and locations, which means we're probably not looking at the same population of animals, and therefore that we're hard pushed to tell dimorphism from other effects on morphology. Note that these problems affect claims for dimorphism in Tyrannosaurus as much as anything else, along with disagreements about the influence of crushing and pathologies on key 'robust' and 'gracile' specimens. Moreover, the analogy of theropod and predatory bird dimorphism is questionable. The latter seems to be related to flight more than anything else, and, moreover, ignores the fact that many terrestrial carnivores show 'standard' dimorphism.

    4. No worries, I know what you're saying about geographic/temporal variation. To be fair though, RSSD probably isn't closely related to flight ("Small fleet prey, aerial or terrestrial, are more abundant than large sluggish prey, so that over time smaller male bird-eating raptors would be favored over larger, less agile ones, because they would be better providers": ). Ehrlich et al. further describe the most plausible hypothesis for the size difference & explain why the females in particular are larger, the reason for which is irrelevant to mammals (I.e. "Many terrestrial carnivores").

      Sorry for getting side-tracked from the original topic. I'll just add that, among other things, it's too coincidental that coelophysids & tyrannosaurids (I.e. The dinos for which there's evidence of RSSD) seem to be dimorphic in the same ways as said birds (I.e. The robust morphs are larger w/more robust hips & limbs).

      BTW, many thanks again for your AY help. When I 1st got the idea for the LITC contest, I was genuinely surprised no 1 had ever thought to draw "anting" behavior in feathered dinos.


    5. P.S. I said "it's too coincidental", but I meant "it seems too coincidental". Sorry about that.

  11. Thanks for the reply; I didn't realise he might still have toes on the floor, but when I look back at the picture now and imagine his right leg fully extended, the whole operation seems much more doable.

  12. This is naturally going to draw a range of knowledge bases, some of which may be more comprehensive than others, and it may be that some of the more eyebrow-raising images therein are simple mistakes. More interesting facts here

  13. I've always imagined Tyrannosaurs giving hickeys while mating. Don't know why.