I said I wouldn't do any conferences this year. But I lied, and have recently returned from the 58th Symposium on Vertebrate Palaeontology and Comparative Anatomy (SVPCA), this year held once again in Cambridge, UK. Compared to the enormous, sprawling SVP (= Society of Vertebrate Paleontology) meeting with its numerous concurrent sessions (last year held in England, but usually held in North America), SVPCA is tiny and tidy. So, ok, there's less content, but at least you get to talk to everyone you want to, and to go to all the talks. As usual, I had an excellent time and extend warm thanks to the friends and colleagues who made it both fun and interesting.
Here, then, are just a few comments on some of the personal highlights. I'll go through them in approximate chronological order (as in: Palaeozoic, Mesozoic, Cenozoic). First of all, it goes without saying that we spent a lot of time at the University of Cambridge's Museum of Zoology. It's outstanding, housing hundreds of skeletons and preserved specimens of everything from caecilians and lungfishes to indricotheres, giraffes and beaked whales. I took a lot of photos, one or two of which are shown here [Mirounga leonina shown below... wow]. Anyway, to business...
Tim Smithson and Stan Wood discussed an assemblage of new small stem-tetrapods discovered in sediments dated to the Tournaisian, and hence to the infamous 'Romer's Gap' (a latest Devonian-early Carboniferous span of time, (mostly*) mysteriously devoid of tetrapod** fossils). Evidence for terrestrial arthropods was found in the same deposits. The discovery casts doubt on the hypothesis that terrestrial tetrapods and arthropods didn't exist in Romer's Gap due to low atmospheric oxygen content (Ward et al. 2006).
* But not entirely. See Clack (2002) and Warren (2007).
** The term Tetrapoda is used by some authors for the crown-clade that includes all extant tetrapods (and all descendants of their most recent common ancestor). If this is followed, the limbed sarcopterygians outside crown-Tetrapoda are termed either tetrapodomorphs or stem-tetrapods. Tetrapod in the phylogenetic sense is not necessarily, therefore, synonymous with tetrapod in the morphological sense.
Sauropods were comparatively well represented at the meeting with something like seven talks. Four of these were on neck posture and evolution, prompting John Hutchinson (the session chair) to refer to Neck Wars. Two talks were a direct response to the paper Mike P. Taylor, Mathew Wedel and I published last year (Taylor et al. 2009). Awesome: this is how science works [one of the figures from Taylor et al. (2009) is shown here. X-ray data shows elevated necks and neck bases in squamates, crocodilians and turtles: not just in mammals and birds].
In the first of those talks, John Martin looked at neck posture in extant animals. He aimed to show that some living animals do indeed adopt poses resembling those that emerge from osteological neutral pose (ONP). He therefore argued that ONP might really be a useful guide to 'habitual pose' or 'characteristic pose' (as in, the pose an animal is often seen to adopt). But I don't agree, for two reasons. (1) 'Habitual pose' as used by Taylor et al. (2009) and preceding authors means alert pose (the pose an animal adopts when unrestrained, awake, and unengaged in any particular behaviour), not feeding pose, or running pose, or anything like that. Even if sauropods did hold their necks low or horizontally when feeding or drinking (something that everyone thinks they did), it does not follow that their 'habitual pose' was also low or horizontal. (2) John used photos of numerous museum-mounted skeletons to demonstrate that ONP replicates life posture. But mounted skeletons (which are posed with their necks held at the same angle as those of living animals) do not depict life posture at all (you need x-rays to determine this: remember that actual neck skeleton posture is more elevated than the soft tissues seem to imply), nor are they in ONP! The last point was well made in Taylor et al. (2009): when you plug vertebrae together to reproduce ONP, you do NOT get 'habitual pose'.
In a related talk, Kent Stevens took issue with various of the statements made in Taylor et al. (2009), and used new (and excellent) CG models to depict possible neck postures and ranges of motion. He still regards sauropod neck pose to be more horizontal than we do, and his models permit less range of motion between the vertebrae than we consider likely. One of Kent's points was that - even with a near-horizontal neck - a sauropod like Apatosaurus is still capable of reaching upward somewhat by bending the front part of its neck up above the height of its shoulders. But the possibility of an elevated neck base still seemed disallowed, and this is an obvious point of contention. Kent says that sauropods preserved with such neck bases are in death poses and exhibit extreme opisthotonic postures, whereas other people refer to evidence indicating that such postures were definitely 'habitual' in life. We made a point of showing (Taylor et al. 2009) that elevated neck bases are present in squamates, testudines, crocodilians* and neognathous birds (not just ostriches!!), so Kent's implication that we only used rodents, rabbits and cats was a bit misleading.
* And we didn't get x-ray data on the most erect-necked of crocs.
Andreas Christiansen and Gordon Dzemski used neck biomechanics in an effort to analyse neck posture and concluded that erect neck postures were likely for Euhelopus and brachiosaurids. In fact, they found that - when resources were far apart - maintaining the neck in an erect pose was more efficient in term of energy expenditure than were other postures. Andreas also noted that the anatomy and range of movement present in sauropod necks makes low habitual postures unlikely, and he was amusingly critical of the Stevens & Parrish (1999) horizontal-necked hypothesis (as shown in Andreas's cartoon, used above).
To prove that we're all still friends and get along fine, we all went to dinner together, though the ensuing discussion ended in a brawl after Mike made an offensive comment (see adjacent photo, kindly taken by Adam Smith). Further thoughts on the Neck Wars can be seen here on SV-POW!
Mike P. Taylor examined necks as well, but he was more interested in working out why sauropods have been so good at evolving tremendously long necks while other terrestrial tetrapods have never been able to get beyond a 'glass ceiling' of c. 3 m. Pneumaticity, quadrupedalism, reduced reliance on oral processing and other factors combined to allow the evolution of extreme necks in sauropods: the absence of some or all of these factors have seemingly prevented giraffes and other non-sauropods from becoming quite so ridiculous.
OK, gotta stop there. More in part II!
For more on sauropod necks, see...
- Junk in the trunk: why sauropod dinosaurs did not possess trunks
- Sauropod dinosaurs held their necks in high, raised postures
- Thunder-Lizards: the Sauropodomorph Dinosaurs (a book review)
Refs - -
Clack, J. A. 2002. An early tetrapod from 'Romer's Gap'. Nature 418, 72-76.
Stevens KA, & Parrish JM (1999). Neck posture and feeding habits of two jurassic sauropod dinosaurs Science (New York, N.Y.), 284 (5415), 798-800 PMID: 10221910
Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.
Ward, P., Labandeira, C., Laurin, M. & Berner, R. A. 2006. Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization. Proceedings of the National Academy of Sciences 103, 16818-16822.
Warren, A. 2007. New data on Ossinodus pueri, a stem tetrapod from the Early Carboniferous of Australia. Journal of Vertebrate Paleontology 27, 850-862.
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There was a traveling dinosaur exhibit at the San Diego Natural History Museum (by the AMNH). They had a 'skeleton' of the 'Parrish et al' model of a sauropod. Next to it was 2 cervcials of a small Apatosaurus. They had them disarticulated. What impressed me was the size of the ball and socket, it was huge. To me this would mean they were very mobile. Not that does anything for the debate of neck posture, but the neck to me was very mobile and could turn/raise greatly.
Complete critters? Scrappy bits? New and novel stuff? Inquiring minds wish to know more.
You tantalized me with the mentioning of Romer's Gap in the title and hooked me into reading the blog post, but then left me starving with the meager tidbits you gave on this new material. :(
Speaking as a plant ecologist, I'm still trying to get my head around the environment that these sauropods were maneuvering those enormous necks and tails in. This makes moving a grant piano into an upstairs Victorian flat look trivial.
I'd suggest that the appropriate study, is to rent two boom lifts (those four-wheeled devices with an extendable boom on one end, with driver in the basket up top), secure them end to end, and try driving them through various landscapes, from dense forests to open fields. For real participatory science, have noted anatomists at the front end dodging branches and driving the whole rig. Two boom lifts are needed so that the front can be the neck emulator, and the back can be the tail emulator.
Just on first principles, I'd expect huge long necks to be extremely flexible, both to feed and to move. However, a high posture only works if there are few or no trees around to walk through.
AnJaCo and Nick: sorry to be so disappointing. Originally my article included a link to the abstracts themselves, but this got moved to part II when I split the article in two. The fossils themselves weren't fantastic - I only recall three incomplete jugals, all small (compared to taxa such as Acanthostega) and evidently representing distinct taxa. Some other material seemed to represent two additional taxa, similar in size to Pederpes. The abstract is here, but for the full story I guess we have to Wait For The Paper.
Heteromeles: sauropods were around for tens of millions of years and lived worldwide, so making generalisations about their habitat choice is not easy. Many better known forms (like the Morrison Formation taxa) apparently did inhabit open, parkland-type habitats. I'm not sure we can be confident that any species actually lived in dense forests. But they probably did, and you're right that neck and tail flexibility would be required for this to be possible. However, any conclusions we make about range of motion and flexibility is likely going to come from elsewhere.
I am not a paleontologist, but as an outside observer I am always disappointed by the way people talk about sauropods. They were unique in so many ways - size, growth rates, neck length, tiny heads - and still everybody seems to think of them as of some giant aberrant iguanas. To me it is obvious that their uniqueness can only be explained by unique lifestyle, that we are missing some critically important parts of the picture and can't think out of the box. Did they feed on some abundant fleshy food that didn't require chewing? Some fruit that didn't get preserved in the fossil record because it was so soft and tender? Mushrooms, may be? Or may be something really crazy, like sucking in algae-filled pond water, filtering it through some structure in the stomach and spitting it out? Also, did they use their necks to produce infrasound? There has to be something that nobody's considering.
Hey, what about flightless azdarchids? You promised them in this article's title. I demand flightless azhdarchids :D!!
Eh? Am I missing something, or is that some kind of goal-post-shifting way of saying that the giraffe doesn't really have a long neck? To me, it seems a bit offhanded (and, frankly, unfair) to suggest that, from an evolutionary point of view, absolute neck length is something more interesting and/or important than relative neck length.
Regarding the 'Why have sauropods been so good at evolving tremendously long necks' question: Correct me if I'm wrong, but the extra-long neck only evolved once during sauropod evolution, and those Jurassic and Cretaceous sauropods that we all know and love have evolved from ancestors that already had long necks, right? Thus, shouldn't the question rather be why virtually all sauropod lineages retained that long neck?
Vladimir (comment 6): sauropods are indeed a puzzle, but it's not as if palaeontologists aren't interested in, or talking about, these problem areas. Suggestions that they fed on carrion, bivalves, or soft waterplants, or that they filtered small animals from water have all been made, but all are speculative and contradicted by the extensive macro- and microwear typically present on sauropod teeth. This tooth wear (see, for example, Fiorillo 1991, Barrett & Upchurch 1994, 1995, Upchurch & Barrett 2000) shows that sauropods fed on relatively coarse plants, including conifers and ferns, though where they fed within the available vertical range remains contentious.
As for sauropod necks and infrasound, the possibility that sauropods used their super-long tracheae to produce infrasound has indeed been considered (informally) quite a bit: I've discussed it at length with someone who works on emu infrasound, and if you look at the comments appended to this article on bird tracheae you'll see many mentions of sauropod necks. I know of one discussion of sauropod infrasonic capabilities in the technical literature, but the publication concerned was only an abstract.
Frank (comment 7): flightlessness in azhdarchids coming next. As I said, all the SVPCA stuff was originally in one article but I then decided to cut it in two when it became too long.
Dartian (comment 8): I'll leave Mike to elaborate (he was, of course, being facetious), but even the biggest giraffe necks are short compared to typical sauropod necks. It's true that (so far as we know) the long sauropod neck evolved only once (and this must have been outside of Sauropoda, as sauropods are hardly the only long-necked sauropodomorphs). However, comparatively short necks evolved at least twice within Sauropoda (in dicraeosaurids and rebbachisaurids).
Refs - -
Barrett, P. M. & Upchurch, P. 1994. Feeding mechanisms of Diplodocus. Gaia 10, 195-203.
- . & Upchurch, P. 1995. Sauropod feeding mechanisms: their bearing on palaeoecology. In Sun, A. & Wang, Y. (eds) Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers. China Ocean Press (Beijing), pp. 107-110.
Fiorillo, A. R. 1991. Dental microwear on the teeth of Camarasaurus and Diplodocus: implications for sauropod palaeoecology. In Kielan-Jaworowska, Z., Heintz, N. & Nakrem, H. A. (eds) Fifth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Extended Abstracts. Contributions from the Paleontological Museum, University of Oslo, 364, 23-24.
Upchurch, P. & Barrett, P. M. 2000. The evolution of sauropod feeding mechanisms. In Sues, H.-D. (ed) Evolution of Herbivory in Terrestrial Vertebrates: Perspectives from the Fossil Record. Cambridge University Press (Cambridge), pp. 79-122.
Sauropods also absolutely annihilated giraffes in terms of neck:torso length ratio. If you don't believe me, compare for example the Omeisaurus skeleton at http://svpow.wordpress.com/2008/08/28/omeisaurus-is-just-plain-wrong/ with any of the many giraffe skeletons you can find in Google Images.
Still, just in case it wasn't obvious to you, I suppose I should explicitly state that the title of my talk was not really intended so much as criticism of giraffes as praise of sauropods. (The full title, as revealed in the second slide, was "Why giraffes have such short necks ... and how sauropods got it right".
You're wrong :-) Ancestral sauropods had longISH necks, yes -- up there with those of giraffes -- but super-long necks (i.e. four times as long as that of the world-record giraffe) evolved in at least four widely separated sauropod linages: mamenchisaurs, diplodocids, brachiosaurids and titanosaurs. What I tried to bring out in my talk was that the anatomical prerequisites (pneumatic system, large size, distinctive vertebral anatomy, etc.) must have evolved in basal eusauropods, if not before, but that different lineages carried these features forward in very different ways.
Granted, but given the difference in body size between giraffe and sauropods, isn't that pretty trivial? I mean, everything is relative; for example, an adult Triceratops probably had, in absolute terms, a longer neck than the largest swan or the largest flamingo. But how informative would it be to refer to ceratopsians as 'long-necked' animals, and to swans and flamingos, respectively, as 'short-necked'?
Is that true for sauropods in general, or only for the most extremely long-necked taxa? Are there any quantitative studies on this?
I was perhaps a bit too hasty in rushing to the defence of my fellow mammals. I'd like to point out, however, that over at SV-POW, you do tend to refer to 'stinkin' mammals'...
And you can't spill any details beyond the abstract? :-( I'd be particularly interested to know if there are temno- and/or lepospondyls in there.
But thanks for alerting me to this in the first place. Last year at the SVP meeting, there was a talk by Anderson et al. on Tournaisian sites from eastern North America and the pretty wide variety of limbed vertebrates in them (basically, everything except temno- or lepospondyls, plus trackways by a small terrestrial animal), and Smithson had another on his new ?whatcheeriid of the same age. There won't be such talks this year, except if Wood has one (haven't searched the program for his name yet).
A vertical stiff neck would work a lot better in a dense forest than a horizontal stiff neck.
David: so far as I recall, Smithson didn't proffer any possible identifications for the several taxa represented (and I couldn't tell you whether the figured jugals looked specifically like those of temnospondyls or lepospondyls, or indeed whatcheeriids or anything else). He did allude to the material from eastern North America that you refer to.
Re: sauropods and forests: The neck of adult Brachiosaurus looks thick enough to push away rather big branches.
Today rainforests are made impenetrable mostly by angiosperm lianas/creepers, but they have not yet evolved in Jurassic? Are there abundant fossils of Jurassic creepers eg. ferns?
Side question - similar plant-related question could be made about tapejarids and oviraptorids. Tapejarids are often interpreted as toucan or hornbill-like, but I never heard about fleshy fruits from Cretaceous. Oviraptorids are sometimes reconstructed as parrot-like seed crushes, but were there any hard seeds back then?
One sauropod puzzle is how hatchlings grew to adult size within few years. They had the rate of growth comparable only to whales. But whales eat high-energy krill and fed their young on high-energy milk, and sauropods are supposed to eat low-energy coarse plants.
I suspect sauropods cared and fed their young somehow - by some means which left no trace in skeletons. Maybe they regurgitated food like birds, or evolved a different method altogether.
Darren: Thank you for the answer. I just can't see how such a huge amount of coarse conifer branches could be pushed through such a long narrow tube. What if tooth wear has nothing to do with the actual food item? Brown bear teeth sometimes show wear from shrub branches, but this wear happens as bears "filter" berries from branches, or bite off and crush Japanese stone pine cones to get seeds. Even now there's plenty of conifers with fleshy fruit - yews, podocarps, cycads - though almost nobody specializes on eating them nowadays. It is reasonable to assume that in absence of birds, trees relied on dinosaurs for seed dispersal, and produced fruit of sufficient size and nutritional value. But finding (and recognizing as such) a big fleshy fruit in the fossil record would be difficult.
I've read somewhere that dung beetles didn't feed on dung until Angiosperms became widespread, so it looks like there wasn't much around. If sauropods munched on conifer branches, they would have to produce quite a lot.
Jerzy - The whale model of sauropod growth has since been discounted (Erickson et al 2001, Lehman & Woodward 2008). Sauropods took a lot longer to reach adult size than whales (around 40-80 years), though sexual maturity would have happened earlier than that (probably around 20-25 years).
Erickson, G.M., K. C. Rogers, and S.A. Yerby. 2001. Dinosaurian Growth Patterns and Rapid Avian Growth Rates. Nature 412: 429-433.
Lehman, T.M., and Woodward, H.N. 2008. Modeling Growth Rates for Sauropod Dinosaurs. Paleobiology. Vol. 34(2): 264-281.
Since you're on the topic of Sauropod neck and other oddities I also have a question that floats in the back of my head everytime I see a picture of them. Just how efficient could their breathing have been. Their trachea was a mightly long breathing tube, and no matter how large the lungs, I'm just not altogether sure it was all that practical a setup. As a teenager I once tried out an experiment on that by trying to breath through about a meter-long hose. It wasn't long before I started feeling quite dizzy. I can't picture anything living 24-7 under such conditions. Did sauropods have air sacks? (once again not a scientist here, just a layman) Did they make that big a difference in breathing efficiency? What's the current wisdom on the topic?
Jura, did Lehman and Woodward demonstrate that Sander (2000) was in error when he plotted the life history of a Janenschia individual (fig. 10) based on growth lines, showing its attainment of sexual maturity after 11 years and full adult size at 26?
(Yes, that's a slower than whales; but still constitutes putting on mass as quickly as anything alive on land today.)
Mike - Lehman and Woodward did use Sander's work with Janenschia as it was (and may still be) considered to preserve the most complete record of growth for any sauropod. Sander didn't give any weight, or growth curve estimates in his paper, but the data they did provide was enough for Lehman and Woodward to extrapolate an adult mass of around 7 tonnes. Their results matched up pretty well with Sander's results (estimated age at adult: 20-30 years), and agreed well with Sander and Tuckmantel 2003 (age at adult of 19-35 years).
It is still an impressive growth rate. I think a comparison to whales is kinda misleading anyway. Whale babies receive all their nutrition from their mother, and they get an aqueous medium to hold their bodyweight. This frees up a lot of resources that can be directed strictly to growth. Sauropods had none of these options, and yet were still able to pack on the pounds at a pretty impressive rate. If anything, I'd say whale growth is anomalous.
Mike P. Taylor wrote:
"You're wrong :-) Ancestral sauropods had longISH necks, yes -- up there with those of giraffes -- but super-long necks (i.e. four times as long as that of the world-record giraffe) evolved in at least four widely separated sauropod linages: mamenchisaurs, diplodocids, brachiosaurids and titanosaurs."
This seems irrelevant. The determination of neck-elongation evolution is relative to the ancestors of the group in question, NOT an unrelated taxon. In this case, pre-sauropod sauropodomorphans, like melanorosaurs and anchisaurs (for example), have necks only slightly longer than their dorsal series, which must be related to the lineage that follows; if this lineage shows the trend to elongation, which is further elaborated in further clades from which shorter necks are known in ancestral forms, then and only then can one argue that "long necks evolved more than once in sauropods" (paraphrased). It seems instead that long necks evolved ONCE in sauropodomorphans, increased in length in basal Eusauropoda, and then multiple clades further increased this length. What you imply is that "long neck" refers only to the super-long necks of the four clades in question, but NOT to taxa like Shunosaurus lii or Cetiosaurus oxoniensis.
So, are the photos at the top just random snaps from the Cambridge Museum, or do they represent taxa that were talked about at the meeting? I'd love to here the latest news about Indricotheres(*) and Desmostylians(**)!
(*)Top right. There is a very similar skull on display at the AMNH in New York: is Paracerabaluchindrico known from two well-preserved skulls, or is one of these a cast of the other?
(**)Top center. I have moderately confident guesses about the (Genus-level) identity of three of the others, but the one at bottom center is some sort of Sauropsid, and I don't know them as well.
Isn't that the skeleton of an aardvark?
What must have evolved in that common ancestor of sauropodomorphs was a full complement of neck hearts. After that, insanely long necks were easy, even if not always necessary.
What good is a long neck? Wrap it around and around a tree, like a snake, and then LIFT to expose tasty roots.
>>Sauropods took a lot longer to reach adult size than whales (around 40-80 years),
How long did they *live* then???
>>Lehman and Woodward did use Sander's work with Janenschia as it was (and may still be) considered to preserve the most complete record of growth for any sauropod.
So then how did they go from 26 years to 40-80? Because Janenschia was pretty small as sauropods go?
So many things to respond to, so little time.
-- Mesozoic fruit (comment 14): from about the middle of the Cretaceous onwards, fruits are fairly abundant, though they are mostly small and berry-like. We don't know how heavily they were exploited by pterosaurs or dinosaurs, though gut contents and coprolites show that at least some ornithischians were eating them. As for the impenetrability of rainforests, remember that most sauropods were animals of open, parkland-type habitats, conifer-dominated woodlands etc.
-- Valagos (comment 18): sauropods (and other saurischian dinosaurs, and pterosaurs, and perhaps some other archosaurs) had pneumatised post-cranial bones. Use the search box (put in 'pneumaticity') or go over to SV-POW!
-- Sauropod growth rates: the relatively slow rates proposed by Lehman & Woodward may be erroneous - I heard that they incorporated a computational error, though I don't know if a correction for this has yet been published. Data from other specimens/studies indicates that giant sauropods took about 30 yrs to reach full size. Some of this was covered on Tet Zoo before: see the many comments attached to this pterosaur article.
-- Allen (comment 22): the skeletons are, indeed, just a random assortment of some of the ones on display. Dartian is right about the aardvark, sorry. And I'm pretty sure that the Paraceratherium skull is a replica of the AMNH one. Desmostylians will get some coverage in the next article.
Arteries are already contractile; the only innovation that seems necessary is valves in the carotid arteries (valves already exist in many veins, and their number and distribution is subject to individual variation in humans).
Only because of the air-sac system which made breathing through such a neck possible.
Completely impossible for sauropods -- their necks were way too stiff for that.
In Saurischians, were very long necks somehow linked to development of herbivory, or at least some degree of "non-hypercarnivory"? Prosauropods had slender necks, and evolved to herbivores; Therizinosaurs, Oviraptorosaurs and ornithomimosaurs too. Hypercarnivores usually had bulky heads with shorter snouts (the "carnosaur" type).
Although I oversimplified with the few years, more like 10-25 years, but sauropod growth is still impressive.
Am I right that no modern animal achieves growth rate of sauropods on a diet of plants? Elephants are born at least 10 times heavier than hatching sauropods and are fed on milk for several years.
It's worth considering not just how sauropods may have managed to move in a tree filled environment, but how they might have affected such an environment. Elephants have a heavy impact on their environment, including vegetation patterns, and they are quite a bit smaller than most sauropods. If nothing else, game trails in the mesozoic must have resembled roadways, not narrow paths.
Darren (re #26)-- thanks for the Desmostylian news in the next post! While I cringe with shame about mis-identifying the skeleton in the top center of your top photo: I should have looked harder and thought about the implications of the long and heavy tail!
Mirounga leonina reminds me of that "walking seal" virtual reconstruction (Puijila darwini). Just the low stance, I suppose.
I don't know about other countries, but in Canada if a conference has a single stream, you can count it as an educational event and include the fee in your tuition tax deduction; if it has multiple streams so no one knows what you're attending, you can't. It might be worthwhile to look up the educational status if you can deduct professional memberships and tuition.
Is the vagus nerve loop a constraint on neck growth, e.g. in giraffes? Is it a constraint across all tetrapods, and did sauropods somehow solve it?
Is the vagus nerve loop a constraint on neck growth, e.g. in giraffes? Is it a constraint across all tetrapods, and did sauropods somehow solve it?
It's probably not a constraint, because the nerve fibers elongate as the neck develops. There are no a priori reasons to expect that they would hit a limit. All tetrapods have recurrent laryngeal nerves, even long-necked things like giraffes and ostriches, so the null hypothesis would certainly be that they were present in sauropods.
I'm happy to say that if you want more than that on the topic, please see my forthcoming paper (not for a few more months, unfortunately).
Considering the extent to which so many mammals use scent signals, often rather repellant to us humans, I think "stinkin' mammals" is a fair cop.
And they're not that discriminatory, because some SV-POW! posts are also labelled "stinkin' heads".