Easty, resident Terrapene carolina triunguis at Casa Adams Wedel, sometime gnawer of rat skulls, whose recent exploits will be detailed in future posts.
In Archie Carr’s encyclopedic “Handbook of Turtles: The Turtles of the United States, Canada, and Baja California”, first published in 1952, he quotes favorably and at length the observations of “Mrs. Knowlton” on the behavior of wood turtles (Clemmys insculpta) and box turtles (Terrapene carolina). The source given in the references is:
Knowlton, Josphine Gibson. 1943. My Turtles. Privately printed. Pp. i-xxxvii, 39-222, 22 figs.
Who was Josephine Gibson Knowlton? She was the author of a few other books, including “The Innocent Cause” and “Roma”; the younger sister of illustrator Charles Dana Gibson and possibly one of the models for his iconic “Gibson Girl” illustrations around the turn of the 20th century; and she married Daniel Knowlton, who played football for Harvard and was later the legal counsel for the Interstate Commerce Commission. Importantly for our purposes, and for Archie Carr’s, she wrote and privately published a whole book about the turtles in her backyard. At least at the time that Carr was writing in the 1950s, Knowlton had cornered the market on observations of wood turtle mating behavior. For all I know, her observations on the topic are still the most detailed available; lots of people write about where turtles are found, but few take the time to sit like Jane Goodall and watch them go through their stereotypically protracted mating sessions.
It sure as heck looks like Josephine’s quite famous older brother illustrated her turtle book; there are interior illustrations in the same style.
Archie Carr was utterly omnivorous in collecting information on the ranges, life history, and behavior of turtles, and his book cites all kinds of sources, from august scientific journals to newspaper clippings. It’s fascinating just to page through the bibliography. Anyone with more than one citation is almost certainly a professional biologist or scientist of some kind, but a lot of the one-hit-wonders, especially from the 1800s, are regular folks. This is directly relevant to a recent comment by Allen Hazen, in which he asked, “Is it worth trying the ‘experiment’ of comparing articles in the same journal published decades apart?” What follows is the example I promised to post.
While reading Carr, I was intrigued by a reference to Fisher (1887) on Muhlenberg’s turtle at a lake in New York, so I tracked it down. The account appears in the Zoology section of the “general notes”, on pp. 672-673 of the 1887 volume of The American Naturalist. Fisher was an MD, not a herpetologist, and he was just reporting on some turtle shells he found stomping around the edges of a lake. Here’s the whole publication (note that nowadays we’d call it Muhlenberg’s turtle, Glyptemys muhlenbergii; when I was a kid it was Clemmys muhlenbergii):
I really admire this little paper — in 165 words, Fisher laid out his methods, described his findings, raised a taphonomic mystery, tied in ornithological and botanical observations to make a biogeographic point, and cited a source, and it’s written like it was meant to be read by humans (curious non-specialists, even) and not merely to pass an editorial gauntlet. This reinforces my strong feeling that conference abstracts can and should be fully-fledged miniature papers, in conception, execution, credit received, and citeability. I will aim to hold my future abstracts to the Fisher standard.
Still, it is wild to me that American Naturalist is now one of the most prestigious journals in ecology and evolution, such that publishing one paper in “AmNat” can be a career-maker for an up-and-coming biologist, and this has been true for some decades already. But 140 years ago they were publishing letters from randos on dead varmints they found down at the lake.
More on that shift — which was certainly not unique to AmNat, and has happened at other journals within my lifetime — in a future post.
About that Saurophaganax paper
December 22, 2024
Newly out in VAMP:
Danison, Andy D., Wedel, Mathew J., Barta, Daniel E., Woodward, Holly N., Flora, Holley M., Lee, Andrew H., and Snively, Eric. 2024. Chimerism of specimens referred to Saurophaganax maximus reveals a new species of Allosaurus (Dinosauria, Theropoda). Vertebrate Anatomy Morphology Palaeontology 12:81-114.
Oh man, there is soooo much to say about this paper, which is a free download here. The short, short version is that OMNH 1123, the holotype specimen of the giant allosaurid Saurophaganax maximus, does not definitely belong to a theropod and may actually belong to a sauropod, and the same goes for some of the referred material, namely the atlas and chevrons. Since neither theropod nor sauropod material could be confidently assigned to Saurophaganax, we consider it a nomen dubium. That leaves a big ole pile of fossils from the Oklahoma panhandle that really do belong to a giant allosaurid, which we think is sufficiently distinct from Allosaurus fragilis and Allosaurus jimmadseni to warrant naming a new species, Allosaurus anax. If you want all the evidence and technical details and scientific reasoning, it’s in the paper, and some of it may make it into future blog posts. If you want to know what a weird ride this project has been, read on.
Who even are you?
The first point I want to make is that I myself have had just about every possible conflicting thought about the identity of OMNH 1123, the Saurophaganax holotype. I think chronologically I’ve gone through the following stages in this order:
- thinking it belongs to a theropod, for essentially all of my life before Andy Danison contacted me and invited me onto the project;
- thinking it belongs to a sauropod, after Andy showed me how similar it is to the vertebrae of known juvenile sauropods;
- thinking it belongs to a theropod, more or less in a panic after I published my last post about Saurophaganax and then worried that we were wrong and we were going to make fools of ourselves (or, more flatteringly, I made the strongest case I could for a theropod identity to stress-test our hypothesis, which an accurate description of the outcome but a lie about my motivation);
- thinking it could plausibly belong to a sauropod, after Andy countered every point I raised in my “Saurophaganax is a theropod after all” push with photos of the same characters in the vertebrae of juvenile sauropods, which led to me agreeing with Andy and the other authors that designating Saurophaganax as a nomen dubium was the best move — this is the point of view that is crystallized forever in the new paper.
Also, I believe that at various points during the study the author team considered just about every possible scenario for dealing with the name Saurophaganax maximus, from thinking that it was a valid theropod genus and species, to thinking that it might be a valid sauropod genus and species (put a pin in that thought), to thinking that it was potentially valid but not definitively referrable to either Theropoda or Sauropoda, to realizing that if we couldn’t be certain if it was a theropod or sauropod, then no-one would be comfortable referring either theropod or sauropod material to it, which pushed us toward designating it a nomen dubium. We also considered a lot of potential taxonomic acts, including naming a new genus, naming a new species, or not naming the giant Oklahoma allosaurid and leaving it as Allosaurus sp. In the end, we decided a new species best captured our thinking about the material, and was most likely to be stable over the long run.
Am I sure about this?
Heck no! I’m the same guy who thought the Saurophaganax holotype was definitely a theropod, and definitely a sauropod. I remember the logic and evidence I used to reach each of those conclusions; I remember the certainty I felt in each one of those states; I remember the confidence that certainty gave me. But I think now that it was false confidence. I’m happy with the work we did in this paper, and I’m proud of it, and I think we came to the least-bad solution. But I’m sure this will not be the last word on Saurophaganax, and future authors may discover things we overlooked, or come back with a new perspective when and if new material of the giant Oklahoma allosaurid comes out of the ground.
Here’s what gives me pause: the accessory laminae in the Saurophaganax holotype are pretty much dead ringers for the spinoprezyg laminae (SPRLs) in the giant Oklahoma apatosaurine. I didn’t figure that out, Andy Danison did, and it’s one of those things that has just kept growing and growing in my mind, even after the paper was finalized. No other allosaurid or allosauroid or theropod of any description that I know of has prominent bars of bone in the same place, but they’d be expected in the neural arch of a juvenile diplodocid. And at this point I think it’s bordering on special pleading to argue that the giant Oklahoma allosaurid just happens to have these bars of bone, unique among theropods, that look identical to the SPRLs of a juvenile diplodocid, in a quarry dominated by diplodocids. So as of this evening/early morning, sitting here writing this post, I’ve about talked myself back around to thinking that the Saurophaganax holotype belongs to a sauropod, and possibly to a juvenile of the giant Oklahoma apatosaurine.
The most obvious argument against is that whatever OMNH 1123 is, it had strongly-up-tilted transverse processes, like Haplocanthosaurus and a lot of theropods (see the Discussion in Boisvert et al. 2024) and very much unlike, say, OMNH 1366 and other dorsals of adult diplodocids. But I now think this is ontogenetically plastic — the juvenile Barosaurus specimens described by Melstrom et al. (2016) and Hanik et al. (2017) also have strongly up-tilted transverse processes. And in case I get hit by a bus before I can explain this more fully, it’s pretty clear that the neural arch telescopes in the dorsoventral direction over the course of ontogeny, and someone should work on that, too.
Anyway, the specter of Saurophaganax as a sauropod is a good segue to the next section.
What if we’re wrong?
I wrote up above about the comforting certainty of thinking that the Saurophaganax holotype definitely belonged to a theropod, or definitely belonged to a sauropod. I think that was in part because the intermediate idea, that OMNH 1123 could be either thing, feels inherently unstable to me. Surely someone will come along and point out some feature or combination of features that makes OMNH 1123 either definitely theropod or definitely sauropod. What then? Here are the possibilities I’ve thought of:
- OMNH 1123 definitely belongs to a theropod, and it’s diagnostic enough to hang a species name on: then it goes back to being Saurophaganax maximus or Allosaurus maximus depending on how people calibrate their genericometers, Allosaurus anax becomes a junior synonym, and we were just flat wrong (see our discussion of this possibility on p. 107 of the new paper).
- OMNH 1123 definitely belongs to a theropod, but it’s not diagnostic enough to hang a species name on: Saurophaganax remains a nomen dubium, just a nomen dubium with a home, and Allosaurus anax remains the valid name for the giant Oklahoma allosaurid.
- OMNH 1123 definitely belongs to a sauropod, but it’s not diagnostic enough to hang a species name on: Saurophaganax remains a nomen dubium, just a nomen dubium with a home (in Sauropoda or Neosauropoda this time), Allosaurus anax remains the valid name for the giant Oklahoma allosaurid, and the giant Oklahoma apatosaurine remains unnamed.
- OMNH 1123 definitely belongs to a sauropod, and it’s diagnostic enough to hang a species name on: well, Allosaurus anax remains the valid name for the giant Oklahoma allosaurid, and the implications for the giant Oklahoma apatosaurine are…real interesting.
I don’t think #1 is likely, but I don’t think it’s impossible. Option #2 seems the least likely to me: if OMNH 1123 belongs to a theropod, surely the unprecedented accessory laminae would make it highly diagnostic — this was the cornerstone of Dan Chure’s case in his 1995 paper naming Saurophaganax. Option #3 seems the most likely to me, for reasons explained above; instead of accessory laminae that are unique among theropods,* the weird bars of bone in OMNH 1123 would be bog-standard SPRLs, and the specimen could plausibly belong to any of several diplodocids known from Oklahoma Morrison.
* To be clear, the fact of some accessory laminae somewhere would not be unique to OMNH 1123 among theropods, but accessory laminae that mimic sauropod SPRLs would be.
It’s not super obvious which of these critters — if either — the name Saurophaganax might apply to. Gotta say, I did not have that on my bingo card before this year. Clash of the Titans exhibit at the Sam Noble Museum (OMNH).
Option #4 doesn’t seem very likely to me, but it is fascinating to consider the implications. I’ve long suspected that the giant Oklahoma apatosaurine represents a new species at least, based on a bunch of characters I’m not going into in this post, but I’ve never done the thesis-equivalent of work that it would take to persuasively demonstrate that. There is a scenario in which OMNH 1123 might be shown to belong to Apatosaurinae, in which case the combination Apatosaurus maximus could be on the table. Or Saurophaganax might become the third genus of apatosaurine alongside Apatosaurus and Brontosaurus, which seems insane, but there’s a plausible path to that result. OMNH 1123 wouldn’t be my first pick of holotype for the giant Oklahoma apatosaurine, and it could belong to a non-apatosaurine diplodociod, in which case no issues would arise for Apatosaurinae. Still, by lobbing the specimen vaguely (but not definitively!) sauropod-wards we may have created future headaches for sauropod workers in the Oklahoma Morrison. But we had to slay the dragon in front of us, not all the dragons everywhere forever.
Also, I should note that I’m a firm nominalist: to me names are hypotheses, and we should keep them around as long as they’re useful. I’m betting that Allosaurus anax is going to be a better fit for the giant Oklahoma allosaurid, but time will tell. And speaking of the name…
The name
I love the name Allosaurus anax. I didn’t come up with it, Andy did. Here’s why I like it so much:
- Most importantly, although we came to different conclusions than Chure (1995) about the identity of OMNH 1123, we like and respect Dan Chure and his work, and we didn’t want the new paper to be seen as a criticism of his work. I always thought Dan showed a lot of generosity of spirit in creating the name Saurophaganax maximus, honoring J. Willis Stovall and salvaging Stovall’s intent with the original, defunct name Saurophagus maximus. Similarly, I thought it was just perfect that Andy wanted to honor Chure’s work and salvage his intent by creating the species name Allosaurus anax.
- The species name anax means “king”, and there’s a nice parallel there to Tyrannosaurus rex. Allosaurus rex would sound derivative. I’m hardly unbiased here, but to me Allosaurus anax sounds wicked awesome.
Did someone say wicked awesome?
Our reviewers
If I could have picked any two peer reviewers in the world for this paper, I would have picked Jerry Harris and Tom Holtz. Jerry because he’s described skeletons of an allosauroid (Acrocanthosaurus, in Harris (1998) and a diplodocoid (Suuwassea, in Harris & Dodson 2004 and numerous subsequent papers), so he has experience with all of the clades where OMNH 1123 might land, and because he consistently gives very careful, constructive reviews. Tom Holtz because he’s extremely sharp on theropod morphology but knows a thing or two about non-theropod dinosaurs, too, and also provides very thoughtful reviews. In the actual event, we got them both, and I couldn’t be happier.
My coauthors
Wow, what a great team this was to work with. I went to grad school with Andrew Lee, but we never managed to publish together before this. I’ve admired Eric Snively’s work for years but never published with him before either, ditto for Holly Woodward and Danny Barta. Funny true story: the authorship order of the paper is different from that of the SVP abstract because Holly thought that she hadn’t done enough to earn second author status, and she wanted someone else to take it. But Danny and I both felt that way about our own contributions. In the end I let them persuade me, but I still feel odd about it — so much of what I did on this paper was just get schooled by Andy Danison. At best I think I was the whetstone to his blade, but he did all the cutting.
And that brings me at last to Andy. Good heavens, he worked his butt off on this project, in museum collections and in the literature, finding stuff I’d never noticed and making connections that had escaped me, and then explaining his findings to us with piercing clarity. It was humbling but also exhilarating, because I got to learn new stuff about sauropod vertebrae. I hope to get some of that stuff into a future post, but for now it’s way late and I must sleep. Congratulations, team! It’s been satisfying to work with each of you.
Parting shot: it’s beginning to look a lot like S’naxmas
Jenny and I were talking tonight about some of the big Jurassic Park/Jurassic World dinosaurs we have around the house, and I discovered that the Jurassic World Super Colossal Allosaurus was a thing. What could be better for a dinosaur-obsessed guy who just helped rename the real world super colossal Allosaurus? Jenny got online and found it in stock at the local Target, and I ended up racing through the store in the last five minutes before they closed to score one for myself.
I hope to do some more blogging about this project. We didn’t go into it in a lot of detail in the paper, but some of the stuff Andy found has wild implications for Morrison sauropods. And it would be kinda cool to do a post-mortem on why I was certain that OMNH 1123 was a sauropod, then a theropod, and now maybe sauropod again. And talk about the referred specimens. And about pneumaticity. Just maybe not until after Christmas. Then again, who knows. I’m publishing on stinkin’ theropods now, so anything is possible. Watch this space.
Previous posts on Saurophaganax:
- About that Saurophaganax abstract (October 20, 2024)
- Friday phalanges: Megaraptor vs. Saurophaganax (April 19, 2013)
References
- Boisvert, Colin, Curtice, Brian, Wedel, Mathew, & Wilhite, Ray. 2024. Description of a new specimen of Haplocanthosaurus from the Dry Mesa Dinosaur Quarry. The Anatomical Record, 1–19. http://doi.org/10.1002/ar.25520
- Danison, Andy D., Wedel, Mathew J., Barta, Daniel E., Woodward, Holly N., Flora, Holley M., Lee, Andrew H., and Snively, Eric. 2024. Chimerism of specimens referred to Saurophaganax maximus reveals a new species of Allosaurus (Dinosauria, Theropoda). Vertebrate Anatomy Morphology Palaeontology 12:81-114.
- Hanik, Gina M., Matthew C. Lamanna and John A. Whitlock. 2017. A juvenile specimen of Barosaurus Marsh, 1890 (Sauropoda: Diplodocidae) from the Upper Jurassic Morrison Formation of Dinosaur National Monument, Utah, USA. Annals of Carnegie Museum 84(3):253–263.
- Harris, J.D. 1998. A reanalysis of Acrocanthosaurus atokensis, its phylogenetic status, and paleobiogeographic implications, based on a new specimen from Texas. New Mexico Museum of Natural History and Science 13:1−75.
- Harris, J.D. and Dodson, P., 2004. A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA. Acta Palaeontologica Polonica, 49(2):197-210.
- Melstrom, Keegan M., Michael D. D’Emic, Daniel Chure and Jeffrey A. Wilson. 2016. A juvenile sauropod dinosaur from the Late Jurassic of Utah, USA, presents further evidence of an avian style air-sac system. Journal of Vertebrate Paleontology 36(4):e1111898. doi:10.1080/02724634.2016.1111898
Five questions from Tom Redd
October 24, 2024
Three years ago, Tom Redd made a very generous commitment to the SV-POW! Patreon, and he remains our most generous donor in total. When I wrote to thank him his reply included “I have thousands of questions about apatosaurus that I would like to ask you some day.”
It seemed only fair to invite him to ask some of those questions, so we asked him to give us five and said we’d try to answer them. When the questions came through, some of them were hard — not really in our area of expertise. But I promised we’d take a crack, and that we’d invite commenters to chip in where we get something wrong or leave something out.
Then a bit more than three years slipped past. Now, finally: here we go!
Question #1:
Do you think sauropods could have evolved long necks as a defensive strategy? (Better to see your enemies from a long way off). The sigmoid curve and the neutral position is another issue!
I recently read a couple of research papers where the researcher used “radiological imaging” to determine the neutral position of the cervical vertebrae. The result was a gently downward curving neck beginning at the pectoral girdle, with the skull only 2 meters off the ground. (I agree with Matt that this would be an ambush predator’s delight!)
Also, could compressive or tensional forces of cartilage and ligaments affect the neutral position of the cervical vertebra? (I believe Matt also alluded to this condition.)
This is the longest question, but maybe the one I’m best positioned to comment on.
First of all, the perennial question of what sauropods’ long necks were for. There are a few candidate explanations out there. The obvious one is that they enabled high browsing, and on the whole we feel that’s the strongest single explanation. Another candidate factor is sexual selection — that sauropods were particularly attracted to long-necked individuals of the opposite sex — but we don’t feel that is a strong explanation for reasons explained in our 2011 paper (Taylor et al. 2011). Predator avoidance would certainly have been aided by the long visual distances allowed by elevated heads, and we are confident that at least some sauropods used their necks in combat — primarily in intraspecific combat (Taylor 2015) but no doubt also against predators when the occasion arose. And we may well have missed other good uses for long necks.
In reality of course all these factors likely played a role: structures do not always, or even often, evolve for a single reason. When people who know much more about ceratopsians tell me “The horns of Triceratops were for intraspecific display and combat”, I don’t doubt them. But I also don’t doubt that, whatever the primary purpose of the horns, a Triceratops confronted by a Tyrannosaurus would do its damnedest to stick its horns into it. In the same way, while high feeding seems like the strongest driver of sauropod neck elongation, the other factors will surely have played in, too.
I’m not sure what radiological imaging papers you have come across, but the one I know about is Berman and Rothschild (2005) in the Thunder Lizards edited volume. This paper rather questionably partitions all sauropod cervicals into two bins, “robust” and “gracile”, and concludes, based on functional stress analysis, that “the robust-type centrum supported a neck held in a vertical, or near-vertical, pose, whereas the gracile-type centrum supported a neck held in a horizontal, or near-horizontal, pose”. If this is right, and their categorization holds, then Camarasaurus and an unidentified titanosaur had vertical necks; and Diplodocus, Apatosaurus, Haplocanthosaurus, Barosaurus and Brachiosaurus all had horizontal necks. We find every part of this unconvincing. At some point we should explain why in detail; but it is not this day.
Finally, yes, compressive and tensile forces in cartilage and ligaments definitely did affect neutral posture. My 2014 paper (Taylor 2014) shows this rather dramatically.
What we’re seeing here is what the neutral posture would be if cartilage is added to a neck that is otherwise articulated in horizonzal pose. The importance of intervertebral cartilage has often been overlooked, but can make a dramatic difference to neck posture.
Question #2
I recently read a report that indicated Apatosaurus survived at the species level for a period of approximately 8 million years ! So is this a success, average, or a short run?
I’m not sure where you read that, but the problem here is that no-one really knows what Apatosaurus means. We have the type species Apatosaurus ajax, sure, and the referred species Apatosaurus louisae, and the genus Brontosaurus based on the species Brontosaurus excelsus which is sometimes but not always synonymised with the genus Apatosaurus yielding the combination Apatosaurus excelsus, and don’t even get me started on Apatosaurus parvus, Apatosaurus laticollis, Atlantosaurus and whatever the heck AMNH 460 is.
So if we say that Apatosaurus survived for 8 million years, what exactly are we saying? That Apatosaurus ajax is known from sediments that differ in age by 8 million years? That would be interesting if true, but it’s very hard to establish because the referral of any given individual to a particular sauropod species tends to be very uncertain — largely because most specimen are so fragmentary and distorted. And if all we mean is that 8 million years separate the oldest and youngest specimens that have been referred to the genus Apatosaurus — well, that statement is all but meaningless, given the huge uncertainty about what is and is not part of that genus, if indeed genera even really mean anything.
Putting it all together, I’m not confident that there is any reason to think that Apatosaurus was particularly longer lived than other sauropods. Probably Camarasaurus outlasted it if you include all the taxa that have been referred to Camarasaurus. But then I’m far from convinced that that’s the right thing to do, too.
Question #3
Why so many heavy predators during the age of apatosaurs? Predator to prey ratios were in the 6 to 8% range as compared to modern ratios of 2 to 3%!
I’m not sure I can say much about this without knowing the source of the figures, but I assume that what’s being counted here is the number of individuals represented in the fossil record, and the ratio of a predator species to prey species. The problem is that there is a huge amount of vagueness in these numbers, but it’s not obvious that the apatosaur-age figures are comparable to the modern ones.
Consider first the modern ratio. Which animals are counted in each category? In the Serengeti, lions prey on zebras. So far, so simple, but there are also dwarf moongooses, which are predators — but they don’t hunt zebras. So do we count them in the numbers? If so, do we count their prey animals, too? Including invertebrates? And if not, then where do we draw the line between predators that we consider do and do not hunt the prey animals that we’ve decided we’re interested in?
Then there’s the matter of which animals get counted. If you do your Serengeti counts on dead animals, you might find disproportionately many predators because prey animals tend to be consumed. Or you might find disproportionately many prey animals because they tend to die in areas where the corpses are more easily found and counted. You might be able to do better by counting live animals, but then you might easily undercount secretive predators, or perhaps overcount predators because they stand fearlessly around to be counted.
Now consider trying to measure the predator/prey ratio in the Morrison formation. You have all the problems I already mentioned, plus a bunch of others. If you only count complete-ish articulated skeletons then your sample size is too small to be meaningful. If you count isolated elements, you’re at risk of registering multiple instances of the same individual. Counting individuals represented in bonebeds is difficult because of these problems. Assigning an element to a taxon is error-prone (though should generally be OK at the high level of sauropod vs. theropod — or are you?). Bones of different taxa may survive taphonomy better or worse than others. Life history differences will mean that the fossils of long-lived taxa under-represent their live populations. And so on, and on, and on.
Putting it all together, I would tend to be very sceptical that a difference in ratios of 6–8% to 2–3% is necessarily telling us anything.
With all that said, it’s perfectly possible that the average predator:prey body-size ratio was closer in the Morrison than in modern ecosystems. But we’d do better trying to measure that directly from body-fossils than to infer it from population densities.
Question #4
Are all apatosaur tracks on emergent surfaces? (Some depth of water over the prints)
This I don’t know. But then I wouldn’t know how to pick out apatosaur tracks from those of other diplodocids, and I bet no-one else does, either. Tracks are notoriously variable in shape, and can very wildly from the that of the feet that made them. Given that diplodocid feet were mostly pretty similar anyway, I would not be easily persuaded that any track can be confidently identified down to the genus level.
One other thing to be aware of is that there is often not agreement on the conditions under which a given track is made. One palaeontologist may think a given a track is a direct print, another will think it’s an underprint. I don’t mean to say that it’s hopeless and all we can do is throw our hands up in despair — good work is being done on interpreting tracks, but we have a long way to go. And this is not an area that I’m at all expert in.
Question #5
I read recently that in order for a skin impression to be made the Dermal tissue must undergo a type of chemical alteration! Do you think this is what allows the impression to be made?
That doesn’t sound right to me. The first thing that has to happen for an animal to be fossilized is that it needs to be buried in sediment really fast after it dies — before it’s eaten by scavengers. For something as fine as skin impressions to be preserved, that sediment needs to be very fine — which sadly tends to conflict with the first condition, since course sediments can be deposited more quickly than fine ones. It’s really hard for enough fine sediment to be laid down quickly enough to cover an animal of the size of a sauropod, which is why we don’t have sauropod specimens like those gloriously preserved theropods from the Yixian Formation in China(*). So sauropod skin impressions are pretty rare.
(*) Alternatively: there are spectacularly preserved partial sauropod specimens in the Yixian, but Chinese researchers can’t be bothered to write them up because they’d rather spend their time getting a slam-dunk Nature paper out of yet another little feathered theropod. Unduly cynical? Maybe. But I continue to live in hope.
Well, that about wraps up the five questions — to the best of my ability at least. But I’d love to hear from people who know more than I about these topics: leave a comment, and fame and glory could be yours!
And finally … if you, too, would like to have us answer five questions on the sauropod-related topic of your choice, quite possibly in the less than three years, you should consider getting yourself across the The SV-POW! Patreon and making an unreasonably extravagant financial commitment.
References
- Berman David S., and Bruce M. Rothschild. 2005. Neck posture of sauropods determined using radiological imaging to reveal three-dimensional structure of cervical vertebrae. pp. 233–247 in: Virgina Tidwell and Ken Carpenter, Thunder-lizards: the sauropodomorph dinosaurs. Bloomington: Indiana University Press.
- Taylor, Michael P. 2014. Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs. PeerJ 2:e712. doi: 10.7717/peerj.712
- Taylor, Michael P., David W. E. Hone, Mathew J. Wedel and Darren Naish. 2011. The long necks of sauropods did not evolve primarily through sexual selection. Journal of Zoology 285:150-161. doi: 10.1111/j.1469-7998.2011.00824.x
- Taylor, Michael P., Mathew J. Wedel, Darren Naish and Brian Engh. 2015. Were the necks of Apatosaurus and Brontosaurus adapted for combat?. p. 71 in Mark Young (ed.), Abstracts, 63rd Symposium for Vertebrate Palaeontology and Comparative Anatomy, Southampton. 115 pp.
Sauropod Vertebra Picture of the Week 