A most atypical stegosaur

i-ab9b24859ab3dba9e2d1ee2d2b82601d-the phantom menace 7-11-2007.JPG

Again, no time to complete any articles, sorry. Bloody annoying. Attended Witton pterosaur talk yesterday (it included revelations on winged hatchet-headed ptero-squirrels) as well as a Peter Burford talk on Gambian birds. Have found ten mins to post the above: fantastic pic from Matt Wedel (aka Dr Vector). Few quick factoids on Stegosaurus...

Stegosaurus is no longer unique to the USA (now known from Portugal too), it's not definitely the biggest stegosaur (European Upper Jurassic Dacentrurus might have been as big or bigger), it's possibly the only stegosaur that lacked parascapular spines (so far as we can tell, all other stegosaurs had big shoulder spikes), it was once involved in a bizarre hoax which claimed that it was an agile cursorial biped, and it's one of few stegosaurs to be decked out with plates along most of its length (most other stegosaurs seem to have had plates restricted to the neck and back only: the hips and tail were spiky). Recent work indicates that the plates had a keratinous horny covering (they were not just skin-covered): the idea that they functional primarily in thermoregulation isn't supported by their histology (Main et al. 2005), and - again in contrast to other stegosaurs - Stegosaurus was odd in that its plates weren't arranged in two parallel rows, but in a strange staggered arrangement. You could make a good argument that what is, ironically, the most familiar stegosaur is in fact the strangest and most atypical.

The idea that some Stegosaurus species, like S. ungulatus, had eight tail spikes has proved erroneous (Carpenter & Galton 2001). Evidence that the tail-tip spikes were used in a vigorous and offensive fashion comes from busted spikes that had apparently made jarring impacts with hard objects (McWhinnet et al. 2001), and from an Allosaurus caudal vertebra that bears a hole exactly matching a thagomizer spike in size and shape (Carpenter et al. 2005). And, yes, the spiked tail-tip is now generally known as a thagomizer. World's most incredible sauropod and frogs, frogs, frogs coming soon!

Refs - -

Carpenter, K. & Galton, P. M. 2001. Othniel Charles Marsh and the myth of the eight-spiked Stegosaurus. In Carpenter, K. (ed) The Armored Dinosaurs. Indiana University Press (Bloomington and Indianapolis), pp. 76-102.

- ., Sanders, F., McWhinney, L. A. & Wood, L. 2005. Evidence for predator-prey relationships: examples for Allosaurus and Stegosaurus. In Carpenter, K. (ed) The Carnivorous Dinosaurs. Indiana University Press, Bloomington and Indianapolis, pp. 325-350.

Main, R. P., de Ricqles, A., Horner, J. R. & Padian, K. 2005. The evolution and function of thyreophoran dinosaur scutes: implications for plate function in stegosaurs. Paleobiology 31, 291-314.

McWhinney, L. A., Rothschild, B. M. & Carpenter, K. 2001. Posttraumatic chronic osteomyelitis in Stegosaurus dermal spikes. In Carpenter, K. (ed) The Armored Dinosaurs. Indiana University Press (Bloomington and Indianapolis), pp. 141-156.

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Thanks for the 10 minutes! I could take 10 hours and do less.

I remember that poster on bipedal Stegosaurus! We were all wondering how it slipped by the SVP referees.

Someone had another joke poster at SVP this year, but unfortunately I missed it.

Did the actual poster contain any statement of it being a hoax? Who wrote it?

I remember seeing that abstract when the 2002 SVP program was first posted online, so I was 15 at the time. I didn't notice that the author was at a fake university, so I just assumed it was a weird, but real, study. Because why would I ever suspect the SVP of promoting a fake abstract? I struggled in class that day to draw Stegosauruses that were agile and bipedal, but I was unable to make them look convincing. :(

By Brad McFeeters (not verified) on 07 Nov 2007 #permalink

Hardly the first occassion when the 'type' member of a group turns out to be the oddball. Look at foxes - in the genus Vulpes, you don't get much more distinctive than Vulpes vulpes itself.

We were all wondering how it slipped by the SVP referees.

That was apparently the point: to show that the articles are hardly reviewed.

What was the joke this year? I'm reading the abstracts volume and haven't come across an obvious one so far.

World's most incredible sauropod and frogs, frogs, frogs coming soon!

And after the frogs the temnospondyl series will be continued...? :-)

By David Marjanović (not verified) on 07 Nov 2007 #permalink

Don't you think you should have given a cite for thagomizer (Larson, 1982)?

Stegosaurus is famed, as well, for a peanut brain and a bundle of nerves in its rear end (whatever happened to that idea?). Also, according to one TV show, it hates juvenile Diplodocus like heck.

R.I.P. the late Thag Simmons.

http://en.wikipedia.org/wiki/Thagomizer

I like this quote: "Discoveries of articulated stegosaur armor show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted." Whose bright idea was it to point them upwards?

By Nathan Myers (not verified) on 07 Nov 2007 #permalink

Now might be a good time to mention an appealingly cranky (not to say crackpot!) notion first bruited on Laelaps's site.

It's a commonplace among archaeologists that none of humanity's present physical culture will remain evident to their (procyonine?) successors a million years hence. Still, one human footprint won't be so easily eroded: the present mass, worldwide extinction, desolating terrestrial, marine, and aerial habitats alike. Arguably, a cross-habitat holocaust is, archaeologically, the defining signature of a technically capable sentient species.

So, now, just as a thought-experiment, suppose Dinosauria had brought forth a sentient form that thrived for a time. What would we expect? A mass extinction, sure, but what *kind* of mass extinction? Are there any features of K-T that presently defy explanation, but would be compatible with direct extermination? Didn't many of the larger species decline, sharply, well below the iridium layer? Didn't a few persist implausibly long above it? (And about that iridium layer: did that asteroid really fall, or was it *pushed*?)

This may seem to be going places well beyond cranky, but I'm seriously curious about how well the extermination model fits actual evidence. If the physical evidence can't rule out a hypothetical tool-using theropod, can the fossil record rule out its ever so predictable effect?

By Nathan Myers (not verified) on 07 Nov 2007 #permalink

On that infamous SVP poster... as David noted, it was (apparently) deliberately produced in order to show that SVP wasn't appropriately vetting conference submissions. The author was a T. R. Karbek (anagram of R. T. Bakker) of the Steveville Academy of Palaeontological Studies (no such place), the abstract was gibberish with no real scientific content, and the poster itself consisted of nothing more than re-oriented photocopies of Bakker's rearing Stegosaurus drawing (in the original drawing, the animal's long axis is at an angle to the ground, but in the 're-oriented' pics, the pic had been rotated so that the long axis was parallel to the ground: ergo, Stegosaurus could run bipedally).

New Scientist discovered that it was a hoax: their article is here... if you can't access this, the Geological Society reproduce it in full here. The published abstract is...

T. R. Karbek. 2002. The case for Stegosaurus as an agile, cursorial biped. Journal of Vertebrate Paleontology 22 (Supp to 3), 73A.

To this day I don't think that anyone has admitted that they were the perpetrator(s). But, come on, someone out there in the Tet Zoo readership must now - after all, the author(s) couldn't have put up the poster under cover of darkness or anything. Of course, Greg Paul did once suggest that Stegosaurus might really have been an obligate biped (albeit not a cursorial one), but that's another story.

A cursorial stegosaurus. How silly. Everyone knows they hopped and the thagomizer was there to give weight to the tail as an energy storage measure to improve their efficiency in hopping.

By Mike from Ottawa (not verified) on 08 Nov 2007 #permalink

Yes, there was another hoax poster at SVP this year, but it wasn't submitted as an abstract (at least I can't find it in the abstracts book), just pinned up in an otherwise empty area of the poster room.

And, by the way, it was one of the funniest things I've ever seen. Stupidly, I didn't think to take a photo of it, but surely someone out there did? If anyone has a copy, please push it my way, and I'll post it on my website for the rest of the world to enjoy.

That was apparently the point: to show that the articles are hardly reviewed.

ARGH! Abstracts, not articles!

So that SVP poster was a hoax? Sounds like a fun story there. Any more info on the motives and such?

Was mentioned on the DML! :-)

"Discoveries of articulated stegosaur armor show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted."

Just how horizontal they were is less clear -- probably they were somewhat oblique. Also note that I can't remember seeing a depiction of the spikes as vertical; more than 45° from horizontal, yes, but not vertical.

So, now, just as a thought-experiment, suppose Dinosauria had brought forth a sentient form that thrived for a time. What would we expect? A mass extinction, sure, but what *kind* of mass extinction?

The idea is not new. There's a pretty old joke: "Some of the more intelligent dinosaurs were concerned about the new iridium-enriched fusion reactor: 'If it goes off, only the cockroaches and mammals will survive.'"

Are there any features of K-T that presently defy explanation

Not that I know of.

Didn't many of the larger species decline, sharply, well below the iridium layer?

No, as a very large study in the 1990s showed. People just hadn't looked closely enough.

Didn't a few persist implausibly long above it?

No. Various fragments have been reworked ( = washed out of older layers and redeposited in younger ones), and others turned out to be misdated.

(And about that iridium layer: did that asteroid really fall, or was it *pushed*?)

That looks untestable, but it's unparsimonious, because a possible source for the asteroid and its trajectory has been identified.

By David Marjanović (not verified) on 08 Nov 2007 #permalink

In `A Land` by Jaquetta Hawkes, she describes the stagosaurus as "A childlike poet who has lost his wits, and, having hung himself with potlids and tea trays as protection from his critics, drifts though life eating ice cream and drinking creame de menthe."

An interesting theory of diet, eh?

David: Thank you. (Clearly, if the asteroid was pushed, parsimony says the cephalopods did it to clear out room for the mammals who would become their primary food source. Fthagn!) Has anybody explained why large marine reptiles disappeared at the same time?

Is there any evidentiary reason to have assumed the thagomizer spikes did not all lie horizontally? From a practical standpoint, vertical, near-vertical, and slanted spikes all seem about equally useless. Is this an example of the Millikan effect at work?

By Nathan Myers (not verified) on 08 Nov 2007 #permalink

I believe I do know the author of the cursorial poster.
However I have never gotten any confirmation of it, and have not had the nerve to ask the alledged individual if it was indeed them.

All I will say is that it was someone I do know professionally (which narrows it down a bit, but not much).

Fthagn!

Fhtagn!!!

Has anybody explained why large marine reptiles disappeared at the same time?

Oh yes. The whole upper layer of the oceans was sterilized. The plankton died so massively that the ammonites died out -- ammonites had planktonic larvae (known in the fossil record), so to kill off all ammonites you have to kill all of them at once globally. The slightest failure will result in a few surviving ammonite species diversifying wildly and filling the oceans again just a few million years later, as happened after the Devonian-Carboniferous, the Permian-Triassic, and the Triassic-Jurassic mass extinction.

The first few thousand years after the event record a "Strangelove ocean" almost devoid of life.

At the same time, the cheirolepidiacean conifers died out. They used to make up large forests, judging from the abundance of their pollen. So did several mammal groups, and so on.

Every attempt to explain why the dinosaurs (minus a few birds) died out by trying to explain why the dinosaurs died out must fail. The dinosaurs are a very small part of the victims.

---------

What is the Millikan effect?

By David Marjanović (not verified) on 09 Nov 2007 #permalink

Doesn't the chambered nautilus qualify as a surviving ammonite? Why didn't they radiate?

The Millikan effect, if I remember the details right (Google seems no help, and I'm near certain to have something wrong) refers to the long period between Millikan's original measurement of the electron charge, and ultimately correct measurements. Every published measurement in between over-estimated the value. No one wanted (or was allowed to?) publish numbers too far from his, so the published values followed a monotonic exponential-decay curve toward the correct value. Applied here, the effect would be thagomizer spikes gradually tending toward the horizontal, long influenced by the originally published (I presume!) spurious orientation.

By Nathan Myers (not verified) on 09 Nov 2007 #permalink

Doesn't the chambered nautilus qualify as a surviving ammonite?

No, the ammonites are more closely related to the squid/cuttlefish/octopus than the nautilus is. Nautiloids are an old group (Devonian... Silurian... I forgot) and were present but rare ever since the Carboniferous.

Why didn't they radiate?

Because they lay only a few eggs and brood them -- no planktonic larvae --, and because they have a very low metabolism. Great for surviving everything, but not for filling the world.

Thanks for the explanation of the Millikan effect -- I remembered it but not its name. It does seem to occur in paleontology, too, but I can't remember a specific instance. :-)

What's certainly going on is that fossils of that size are rarely preserved in 3D. One particularly complete and articulated* Stegosaurus specimen is even called the roadkill specimen.

* Means the bones are still more or less associated as in life.

By David Marjanović (not verified) on 11 Nov 2007 #permalink

Nathan Myers' idea is not quite new. I remember a science fiction story based on the same premise: "Small Game". Unfortunately I can't remember the name of the author (Asimov?). It was about a time-traveler going back to the late Cretaceous and finding a small, intelligent, theropod species that had just about exterminated all other (non-avian) dinosaurs, and were for lack of anything better to hunt, starting in on each others (the "Small Game" of the title).

In any case I strongly doubt that all trace of human artefacts would really disappear in a million years or even ten million years. Things like fragments of pottery, porcelain, stainless steel and some other alloys, not to mention gold and cut gems would surely survive for much longer than that, particularily in marine deposits.

To return to the SF theme Poul Anderson wrote a short story on that very subject: "Memorial". His conclusion (probably correct) was that Pioneer 10 and 11, Voyager 1 and 2 (and now also New Horizons) would long survive any other trace of humanity, and quite possibly even Earth itself.

By Tommy Tyrberg (not verified) on 11 Nov 2007 #permalink

I'm not interested in how old is the idea that the dinosaurs were done in by a sentient one of their own. I'm interested in what kind of evidence could distinguish its role from the very loud asteroid-fall signal. A coincidental asteroid fall would be cheating, so we must assume they (or the cephalopods!) dropped it deliberately, or accidentally. What remains is to distinguish evidence, just below the iridium layer, of big changes afoot. We have perhaps 10-30Ka to account for, between beginning development of language and physical culture, and the apocalypse. Geologically that's the blink of an eye, so nobody's to blame for missing it all. Probably, though, we must assume funerary practices tending more to exposure, or stewing, than mausoleums.

I also doubt that all trace of human artifacts would disappear in a million years, or 65, but I defy anyone to happen upon Voyager at such a date. If our hypothetical sentients did drop that asteroid, the best, albeit not cheapest, place to look for artifacts would be on the (other!) asteroids. I like to think we could tell the difference between a spanner meant to be operated by dinosaur claws and one meant for tentacles.

By Nathan Myers (not verified) on 12 Nov 2007 #permalink

In re science-fictional takes on the "nothing will survive of humans millions of years after we're dead" concept crossed with "so how do we know dinos didn't have cities?" one, I distinctly remember a story in Analog in the late-80s/early-90s that had a paleontologist at a dig, excavating a gorgeously well-preserved theropod, musing about these things in his head, and realizing that things like gold and gems would survive even if concrete didn't ... and when he got to the forelimbs, he found a simple, plain gold band ring encircling one of the theropod's fingers.

Wish I could remember author or title ...

A most intriguing creature, the stegosaur. With the back plates now thought to be staggered, the profile of the creature shows a solid wall of plates, with no spaces. Thus, I have reason to postulate that the plates were sense organs, designed to detect... something. That something may be scent, or pheromones, with the biggest plates situated near the highest point of the backbone, over the "second brain." Since the "second brain" is situated directly over the genitalia, I think this structure would be more like a gland, possibly like our pituitary, which controls hormones having a role in reproduction. Has anyone postulated this view already?

By Alan Javel (not verified) on 19 Nov 2007 #permalink

Has anyone postulated this view already?

No, because it doesn't work. Organs for smelling would have to evolve from something, they can't just simply appear somewhere on the body. The "second brain" isn't one; judging from birds, which have the same widening of the neural canal in the sacrum, the extra space was used to store glycogen.

The pituitary gland is common to all vertebrates (if not all chordates, I forgot); and because hormones are released into the blood, it doesn't matter where in the body a hormone gland is. Indeed, their arrangement is completely chaotic.

By David Marjanović (not verified) on 20 Nov 2007 #permalink

Thanks, David, for blowing my theory out of the water. Of course, I'll try to return the favor: Do you think nature or evolution would allow for something "completely chaotic?" For instance, the pancreas is where it is not only to squirt juices into the intestines but also to have insulin travel quickly to the liver.

By Alan Javel (not verified) on 14 Dec 2007 #permalink

Thanks, David, for blowing my theory out of the water.

It's neither yours nor a theory! :-)

(A theory is something much bigger.)

Do you think nature or evolution would allow for something "completely chaotic?"

Of course -- as long as 1) another arrangement wouldn't produce a fitness advantage and 2) said other arrangement is evolvable without, say, completely overthrowing the pathway of embryonic development and starting from scratch.

The latter point is the reason for much Stupid Design. It is, for example, why we vertebrates are stuck with eyes that work the wrong way around. Cephalopod eyes (which famously work the right way around) are an invagination from the skin, vertebrate eyes are an evagination from the brain; turning the retina, blood vessels, and nerves by 180° would require getting completely new eyes, and that isn't going to happen.

Insulin isn't only needed in the liver, is it? Glycogen is stored in muscles, too. The fact that Langerhans's Island Cells are situated in the pancreas looks like a coincidence to me.

By David Marjanović (not verified) on 15 Dec 2007 #permalink

Oops! Sorry! The speculation that the plates were sense organs is yours. Only the "second brain" hypothesis (on which it rests) isn't.

By David Marjanović (not verified) on 15 Dec 2007 #permalink

I had assumed that Stegosaurus' staggered plate arrangement carried over to other stegosaurs, too. Also, I thought Kentrosaurus and Huayangosaurus were the only "front half, plates, back half, spikes" stegosaurs known. Other stegosaurs I'm familiar with, like , Wuerhosaurus and Tuojinagosaurus have fully plated backs with four tail spikes, like Stegosaurus.

Same goes for shoulder spines. Doesn't seem like Miragaia has them. Now, granted, I'm not super-familiar with stegosaur diversity (I just rattled off all the ones I know).

hahaha, Stegosaurus in a nutshell.. what a treat!

Not being a subscriber to New Scientist, I can read the article about the cursorial biped hoax only up to the tantalising truncated line that reads: 'Bemused palaeontologists stared at the poster, saying they wanted to ...'
:-D

Contrariwise, in my opinion Stegosaurus habitually trundled along head down, tail held high. Re the notorious dorsal plates, I suggest they were united in life (in each row) by a partially-enclosing raised epidermal ridge; thus, together the two rows formed a distinctive dorsal 'trough' from tail to head. The elevated (and perhaps lightly-agitated) thagomizer, I intuit, served to dislodge ripe fruit from overhead branches. These would then roll down the trough to the head end, where they were eaten.

Stegosaurus thus was a highly-efficient fructivore, but the very inverse of a rearing browser. But we should thank those who earlier erroneously posited it as such, since the very wrongness of their reconstruction has served as an impetus, pendulum-wise, to its diammetrical oposite: this, my theory, the now correct understanding of this most singular creature.

By Graham King (not verified) on 13 Oct 2009 #permalink

Tengu posted

In `A Land` by Jaquetta Hawkes, she describes the stagosaurus as "A childlike poet who has lost his wits, and, having hung himself with potlids and tea trays as protection from his critics, drifts though life eating ice cream and drinking creame de menthe."

An interesting theory of diet, eh?

Wonderful, Tengu! That reminds me of the whimsical, lyricising, inventive (though impractical) White Knight whom Alice met Through the Looking-Glass.

By Graham King (not verified) on 13 Oct 2009 #permalink

David MarjanoviÄ wrote

What's certainly going on is that fossils of that size are rarely preserved in 3D. One particularly complete and articulated* Stegosaurus specimen is even called the roadkill specimen.

Gasp!! the intelligent saurians drove around in monster trucks?!!?

(Awed).. their civilization must have been so like ours.. it's uncanny.
"Plus ça change, plus câest la même chose."

By Graham King (not verified) on 13 Oct 2009 #permalink

Killjoy alert!

Tuojinagosaurus

That's probably an innocent typo, but just to make sure: five syllables: Tuo-jiang-o-sau-rus.

ripe fruit

Pinecones� The oldest known angiosperm trees are Cenomanian, IIRC.

By David MarjanoviÄ (not verified) on 13 Oct 2009 #permalink