Shark week 4: megalodon tooth colonized by boring clams
November 9, 2022
Alert readers probably noticed that I titled the first post in this series “Matt’s first megalodon tooth“, implying that there would be other megalodon teeth to follow. Here’s my second one.
At first glance, this is a pretty jacked-up megalodon tooth. It is pocked with circular and ovoid craters, and has a big fat hole drilled right through it. Hardly collector grade! And in fact that’s what first caught my attention about this tooth — it’s a 6-incher that was being offered for an enticingly low price. But I got even more excited when I clicked past the thumbnail image on the sale site and saw precisely how this tooth was damaged. This is not random, senseless taphonomic battery (ahem); this tooth was colonized by a bunch of boring clams.
Like Adam Savage — and, I suspect, most collectors-of-things — I am fascinated by objects and the stories that they tell. And this tooth tells several stories. First, it’s a huge tooth from a huge shark, a truly vast, multi-ton animal heavier than a T. rex and longer than my house. Second, it’s a fossil that’s millions of years old, evidence of an extinct species from a vanished ecology, one where gigantic sharks and macroraptorial sperm whales hunted small baleen whales, early seals and sea lions, and manatees and sea cows. And third, it’s a relic of another, entirely different ecology, one in which this shed tooth sank to the sea floor and was colonized by a host of smaller organisms, including most obviously hole-boring clams. In effect, this one tooth was a miniature reef, supporting multiple species of invertebrates. The traces left by those invertebrates are themselves ichnofossils, so this tooth is a body fossil with ichnofossils dug out of it. It’s turtles all the way down!
Can we figure out what any of those invertebrates were? Just a few years ago that would have been a challenging task for a non-specialist, but fortunately in 2019 Harry Maisch and colleagues published a really cool paper, “Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay, North Carolina, USA: implications for processes of lag deposit formation”. That paper is very well illustrated, and the figures basically serve as a field guide for anyone who wants to identify similar traces in rocks or teeth of equivalent age. I will take up that sword in a future post.
Incidentally, this is now the biggest tooth in my little collection, just slightly — but noticeably — bigger than my first megalodon tooth: 157mm on the long side, vs 155mm, and 112mm max root width, vs 107mm.
Bonus goofy observation: I strongly suspect that no other megalodon tooth in the world beats this one in simulating a Star Trek phaser.
Reference
A six-year quest is finally complete! Almost all known sauropod necks are incomplete and distorted
January 24, 2022
Today finally sees the publication of a paper (Taylor 2022) that’s been longer in gestation than most (although, yes, all right, not as long as the Archbishop). I guess the first seeds were sown almost a full decade ago when I posted How long was the neck of Diplodocus? in May 2011, but it was submitted as a preprint in 2015. Since then it’s taken far longer than it should have done to get it across the line, and it is primarily with a feeling of relief that I see the paper now published.
In this quarry map for the Carnegie Diplodocus, does it seem to you that the vertebrae of the neck (in purple) are drawn unconvincingly, compared with the fairly detailed drawings of the dorsals? Does that suggest that maybe Reed — who drew this diagram years after the excavation was complete — didn’t really remember how the neck was laid out? How well does the textual description of the skeleton in situ match this map? These are the kinds of questions I was asking myself as I started thinking about what has become the paper published today.
In some ways it’s a really simple paper, pretty much summarised by its title: almost all known sauropod necks are incomplete and distorted. It started out as a formalised version of three posts on this blog (How long was the neck of Diplodocus?, Measuring the elongation of vertebrae and The Field Museum’s photo-archives tumblr, featuring: airbrushing dorsals), but somewhere along the line the tale grew in the telling and it’s ended up as 35 pages of goodness. In the process of review it acquired a lot of new material, including: a discussion of how to locate the cevicodorsal junction (summary: it’s complicated); a couple of ways to numerically quantify the degree of distortion along a neck; and a brief discussion of retrodeformation (summary: it’s complicated).
I hope this paper will be of use, especially to people coming into the field with the same unrealistic assumptions I had back in the early 2000s. Back then, I had in mind a project to determine the thickness of intervertebral cartilage in the neck of Diplodocus by measuring the radii of curvature of the condyles and cotyles of successive vertebrae — an idea that distortion makes unrealistic. I took the DinoMorph work at face value — something that seems incredible to me knowing what know now. The paper that came out today is basically the one I wish I’d been able to read in 2000 (but updated!)
By the way, when I was fine-tooth-combing the proof PDF a few days ago, I was delighted to be reminded that I got the phrase “rigidly defined areas of doubt and uncertainty” into the paper — a reference of course, to the words of the philosopher Vroomfondel in The Hitch-Hiker’s Guide to the Galaxy. I’ll file this alongside the Monty Python reference in my history-of-sauropod-research book chapter and the Star Wars paraphrase that opens a computer-science paper I lead-authored in 2005.
References
Can we distinguish taphonomic distortion and (paleo)pathology from normal biological variation?
February 12, 2021
Taylor 2015: Figure 8. Cervical vertebrae 4 (left) and 6 (right) of Giraffatitan brancai lectotype MB.R.2180 (previously HMN SI), in posterior view. Note the dramatically different aspect ratios of their cotyles, indicating that extensive and unpredictable crushing has taken place. Photographs by author.
Here are cervicals 4 and 8 from MB.R.2180, the big mounted Giraffatitan in Berlin. Even though this is one of the better sauropod necks in the world, the vertebrae have enough taphonomic distortion that trying to determine what neutral, uncrushed shape they started from is not easy.
Wedel and Taylor 2013b: Figure 3. The caudal vertebrae of ostriches are highly pneumatic. This mid-caudal vertebra of an ostrich (Struthio camelus), LACM Bj342, is shown in dorsal view (top), anterior, left lateral, and posterior views (middle, left to right), and ventral view (bottom). The vertebra is approximately 5cm wide across the transverse processes. Note the pneumatic foramina on the dorsal, ventral, and lateral sides of the vertebra.
Here’s one of the free caudal vertebrae of an ostrich, Struthio camelus, LACM Ornithology Bj342. It’s a bit asymmetric–the two halves of the neural spine are aimed in slightly different directions, and one transverse process is angled just slightly differently than the other–but the asymmetry is pretty subtle and the rest of the vertebral column looks normal, so I don’t think this rises to the level of pathology. It looks like the kind of minor variation that is present in all kinds of animals, especially large-bodied ones.
This is a dorsal vertebra of a rhea, Rhea americana, LACM Ornithology 97479, in posteroventral view. Ink pen for scale. I took this photo to document the pneumatic foramina and related bone remodeling on the dorsal roof of the neural canal, but I’m showing it here because in technical terms this vert is horked. It’s not subtly asymmetric, it’s grossly so, with virtually every feature–the postzygapophyses, diapophyses, parapophyses, and even the posterior articular surface of the centrum–showing fairly pronounced differences from left to right.
That rhea dorsal looks pretty bad for dry bone from a recently-dead extant animal, but if it was from the Morrison Formation it would be phenomenal. If I found a sauropod vertebra that looked that good, I’d think, “Hey, this thing’s in pretty good shape! Only a little distorted.” The roughed-up surface of the right transverse process might give me pause, and I’d want to take a close look at those postzygs, but most of this asymmetry is consistent with what I’d expect from taphonomic distortion.
Which brings me to my titular question, which I am asking out of genuine ignorance and not in a rhetorical or leading way: can we tell these things apart? And if so, with what degree of confidence? I know there has been a lot of work on 3D retrodeformation over the past decade and a half at least, but I don’t know whether this specific question has been addressed.
Corollary question: up above I wrote, “It looks like the kind of minor variation that is present in all kinds of animals, especially large-bodied ones”. My anecdotal experience is that the vertebrae of large extant animals tend to be more asymmetric than those of small extant animals, but I don’t know if that’s a real biological phenomenon–bone is bone but big animals have larger forces working on their skeletons, and they typically live longer, giving the skeleton more time to respond to those forces–OR if the asymmetry is the same in large and small animals and it’s just easier to see in the big ones.
If either of those questions has been addressed, I’d be grateful for pointers in the comments, and thanks in advance. If one or both have not been addressed, I think they’re interesting but Mike and I have plenty of other things to be getting on with and we’re not planning to work on either one, hence the “Hey, you! Want a project?” tag.
References
- Taylor, Michael P. 2015. Almost all known sauropod necks are incomplete and distorted. PeerJ Preprints 3:e1767. doi:10.7287/peerj.preprints.1418v1
- Wedel, Mathew J., and Michael P. Taylor. 2013. Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus.PLOS ONE 8(10):e78213. 14 pages. doi:10.1371/journal.pone.0078213 [PDF]
Things to Make and Do, Part 12: London’s mummified mouse
January 24, 2014
Here’s a nice thing: friends and relatives just assume (correctly) that I will want whatever dead animals they find. So I was not completely surprised when I got a call from my brother Ryan (pillager of the Earth) asking if I wanted a dead mouse he’d found mummified at the back of an unused cupboard. Happily this was over the holidays so I could get the specimen in person and not have to deal with mailing it.
This was not destined to be my mummified mouse, however. My son, London, has started a collection of his own. One of the first real skulls in his collection was that of a rat that we found dead in our front yard last year. I cut off its head and we boiled and cleaned the skull together (I still need to post about that). Then we mounted it in a clear plastic bottle that had previously contained toothpicks, so he could take it for show-and-tell. Last fall a second rat turned up dead in the yard; that one is still in the freezer, awaiting complete skeletonization. The mystery of the plague of dead rats was solved when we got home one evening and found our cat, Moe, in the front yard with only the hind leg of a third rat hanging out of his mouth. If I could just train him to kill them and not eat them, we could make a rat army…
Funny side-note: we keep Skulls Unlimited catalogs around for leisure reading. London was looking through one not long after we prepped his rat skull and he saw that you could get a fully-prepared natural bone skull for about twenty bucks. That price seems about right to me, given the amount of work and care that has to go into cleaning, but London was outraged: “Why would people pay TWENTY DOLLARS for a rat skull when they could just clean their own!?”
That’s my boy! I didn’t have the heart to tell him that some people don’t have a ready supply of rats lying around. He’s not old enough to understand that level of deprivation.
So, obviously the mummified mouse was going to show-and-tell. But I didn’t want it to get destroyed. My cheap and low-tech solution was to get a rigid plastic display box from the local hobby store ($5.99 for a two-pack) and stuff it with cotton balls. We cleared some of the cotton around the skull first so it would be more visible. Knowing how third-graders can be when exciting things get passed around, I also glued the lid on. The mouse and the cotton balls are completely immobile even when violently shaken, and hopefully they’ll stay that way indefinitely. I forgot to include a scale bar in either of these photos or to measure my damned murine, but the box lid is 5 inches on side. HeroClix Knifehead showed up because kaiju are notorious attention hogs.
Now, to see if Mousenkhamun can survive the rigors of third grade. I’ll keep you posted.
Well, not really really.
Appendicular skeleton of savannah monitor lizard Varanus exanthematicus, "Charlie", in dorsal view.
What we have here is of course the bones of all four feet of a lizard (plus the limb bones): “sauropod” means “lizard foot”, so lizard-foot skeletons are sauropod skeletons — right?
(Note that the hind limbs are arranged in a weird posture here, with the knees bent forward. Also that the left pes is missing one digit — possibly IV — which was presumably lost some time ago and healed.)
These are the bones of “Charlie”, a mature savannah monitor lizard Varanus exanthematicus, estimated as fourteen or fifteen years old at the time of death. I have his whole skeleton — cranial, axial and limb-girdles — in various states of preparation, and no doubt they will all appear here sooner or later. I was fortunate enough to encounter Charlie in the reptile house of a local kids’ activity centre with the boys, and he was not in a good way. Luckily, his keepers happened to come in as I was looking at him, we got talking, and I popped the question as tactfully as I could — would it be OK to take his body away when the sad day comes?
The sad day came, and I found a message on my answering machine. For one reason and another, it was a couple of days before I was able to drive out and pick up his mortal remains, but it was a proud day when I brought him home:
Savannah monitor lizard Varanus exanthematicus, "Charlie", recently expired, in left dorsolateral view. Scale bar for, uh, scale.
Charlie was a good-sized beast: 111 cm in length from snout to tail, and massing 3.4 kg. I tell you, it was quite a challenge getting him into that pot that you see top right.
Savannah monitor lizard Varanus exanthematicus, "Charlie", recently expired, in right anterodorsolateral view. Juvenile Homo sapiens "Jonno Taylor" for scale.
To prepare Charlie for the pan, I had to remove his tail — much, much harder than I’d been prepared for, as it was so difficult to locate the sacrocaudal intervertebral joint — and gut him. Unfortunately, by the time I opened him up, internal decomposition had set in, and he was not in a pleasant state:
Savannah monitor lizard Varanus exanthematicus, "Charlie", recently expired, in the unpopular right posteroventrolateral view.
(I have much more disgusting photos than this one, but it wouldn’t be tasteful to show them.) Anyway, I abandoned my initial plan of dissecting the organs out, and basically just removed and discarded them. I’ve actually had shamefully little experience with dead animals, so I don’t know how much the horrible state of Charlie’s guts is due to his final illness and how much to post-mortem decomposition.
Once I’d managed — just — to get him into the pot, Charlie was lightly simmered for a couple of hours (to Fiona’s delight), then dismembered, and the individual parts reboiled before I started picking the bones out of the various parts. There’s more to say, but that will have to wait for another time.
Things to Make and Do, part 1: Pig Skull (off-topic)
July 1, 2009
I know, I know: a pig skull is not a vertebra, and it’s not from a sauropod. On the other hand, it is a cool zoological object, and every home should have one. I’m going to show you, in glorious technicolour, how I made a pig skull in under 24 hours at a cost of £3 and some silver, using only implements I had lying around.
First, here is the finished article, just so you know where we’re headed:
Pig skull, cleaned and complete
To get there was a four-step process, which I was comfortably able to do in an afternoon and early evening. It all started as we were driving the boys back from swimming on the Saturday morning, and I stopped in a butcher’s shop in Cinderford to ask whether they had any complete heads. I got a hit straight away: they had a 20 lb pig’s head which they costed at 25p per pound for a total of £5. I ummed and ahed a bit, not because of the price but just because the thing was so darned big; while I was hesitating, the butcher said that, all right, he’d cut off the huge slabs of neck-fat and get the price down to £3. Great: apart from anything else, that made the head portable. So the deal was done, and I brought the only-slightly-mutilated head back home. Here it is on our patio:
Pig’s head, pretty much whole and complete
Now for the preparation, you need:
- A sharp knife
- A big cooking pot
- A teaspoon
- A Japanese-style chopstick (see below)
- A toothbrush that you don’t plan on ever using again
- An understanding spouse
About the chopstick: you want it to have a fairly pointed end so that you can go poking it in cracks and crevices, so a Chinese-style broad-tipped chopstick won’t do at all. If you don’t have a Japanese-style chopstick, simply visit a sushi restaurant and take the sticks home with you at the end of the meal.
Got your tools? OK, off we go!
Stage 1: defleshing
First, cut off all the excess soft-tissue that surrounds the skull. One reason is just to get rid of it up front so you don’t have to cook it off, but the main reason for me was just to get the head small enough to go in the pot — pig’s heads are big things. You do need a good knife for this, strong and sharp, and a strong stomach. At first it felt pretty icky to be slicing bits off a head, but before long I was sawing away merrily at the lips and I guess all told it took about twenty minutes to reach this stage:
Pig head, defleshed
In case it’s not completely clear, that is the head slightly to right of centre — you can see its teeth if you look carefully. To the left is the huge pile of fat that I’d sliced off the head. I could not believe what fat heads pigs have. The amount of actual meat is tiny in comparison: you can see it over on the right. Most of this was little fragments, with the only two half-decent chunks being from the cheeks. I guess they were about two ounces of meat each (50 g), based on the similarity in size to a vanilla McDonalds hamburger.
Stage 2: boiling
At this point, I threw away the fat, put the head in the pan, filled the pan with freshly boiled water until it covered the head, added some washing-up liquid (“dish soap” for you Americans) and left it to simmer for two hours. While that was happening, I fried the meat from Stage 1 and ate it as part of my lunch. Danny (my eldest son) had some; the other two didn’t fancy it.
After two hours, I poured away the hot water, filled the pan with cold water to cool the head, then took it out and started pulling off all the soft tissue. Two hours in the pot had made a big difference, and big slabs of gristle came away neatly from bone. Once I was done, the head looked like this:
Pig’s head, boiled and stripped
Notice the big pile of meat to the right — that’s what came off at this stage. By now the shape of the skull is apparent, but there is still plenty of soft-tissue left. In particular, the big jaw muscles inside the zygomatic arches were impossible to get out at this stage, thanks to a combination of strength and slipperiness. At this stage, the lower jaw could, just, be moved, whereas before it was solid with rigor mortis.
If I were making a movie about zombie pigs, this is the stage I’d film them at.
I took this photo before removing the eyeballs (this is where you need the teaspoon). Turns out that eyeballs are a lot tougher than I’d realised; so are the optic nerves.
Stage 3: reboiling
At this point I didn’t know how many boilings would be needed, but it turns out that the next one was the last. Into the pot it went again, with fresh hot water and washing-up liquid, for another two-hour simmer. When it came out, I drained and cooled it as before, and picked off as much of the remaining flesh as I could. Now the jaw muscles came away easily, and I was able to pull out the cartilage plug in the nose.
Pig’s head, reboiled and stripped
Again, there was a surprising amount of meat from this stage, but the skull was basically free of its fleshy encumbrance by this point. I rather wish now that I’d kept the fat from stage 1 and the meat from stages 2 and 3 so I could have piled it all up together and photographed it together with the skull.
By now, the mandible was cleanly separated from the cranium, and it was easy to rub away the remains of the cartilage covering the joint.
Stage 4: cleaning
By now, only small and tough bits of meat remained. Plenty of them could be scraped away using the Japanese chopstick: this was particularly useful for digging around in between the teeth. By far the hardest part of the cleaning, though, was getting rid of the brain and the cranial nerves. The problem is of course that you don’t want to crack the braincase open, and the brain is far too big to come out of the foramen magnum. Apparently the only way to do this is to swirl your chopstick around inside the braincase, then try to scrape the brain out bit by bit. This I did using several methods: I poked the cranial nerves back inside the braincase with my trusty sushi stick, smushed everything up, tried to hook bits out, ran water through the skull from nose to braincase and generally shook that baby around, getting little bits of brain out. This took a while and was, truthfully, not the most delightful time of my life.
But it was well worth it, because by the time I’d done, the skull looked like it does in the photo at the top of this post. And here is a more scientific composite, showing the cranium in five cardinal views:
Pig cranium in dorsal view (top row); posterior, right lateral and anterior views (middle row); and ventral (bottom row).
This image, together with a version on a grey background, is also available over on my website, next door to the turkey cervical.
Folks, a pig skull is a serious piece of kit. What I have here is the foundations of my very own museum of comparative osteology. Everyone ought to make one.
So am I done? Not quite — there is still …
Stage 5: final cleaning
There are a few bits and pieces of meat that I couldn’t get at, either because they were too firmly attached, tucked away in narrow crevices, or inside the braincase where I couldn’t see what I was doing. So it’s time to let invertebrates do their bit. The skull is currently out in the garden, under a bucket weighed down with bricks so a fox doesn’t wander off with it. Hopefully in a few weeks, insects will have dealt with the remaining soft-tissue. Then I can re-bleach the skull in dilute hydrogen peroxide to deal with the likely discoloration, and glue the loose teeth into the defleshed sockets, and then I really am done.
I leave you with a photograph of my two eldest sons, Matthew (9) and Daniel (10), with the partly prepared specimen.
Left to right: Matthew, Piggy the Piggy from Piggyland, Daniel.
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Obligatory sauropod-vertebra picture
Sacrum of Camarasaurus supremus, AMNH 5761, in left posterolateral view.
The enigmatic taphonomy of Sauroposeidon
July 24, 2008
This figure is stolen from Wedel et al. (2000:fig. 5). A shows the first 11 cervical vertebrae* of Sauroposeidon in articulation. B shows how the holotype specimen, OMNH 53062, must have disarticulated, and C shows it as it was found. Shaded vertebrae and bits of vertebrae were not found. The thickness of the cervical ribs is greatly exaggerated for clarity.
*We assume that Sauroposeidon had 13 cervicals like Brachiosaurus. It is not beyond the bounds of possibility that it had more, but it is unlikely that it had fewer. Sauroposeidon seems to be all about crazy neck elongation, and it doesn’t make sense to make some vertebrae longer while losing others.
Some facts:
- In life, the long cervical ribs formed overlapping bundles, just like the long neck tendons of birds, and that is how the preserved cervical ribs are arrayed–in vertically stacked bundles.
- Each cervical rib is about 4 cm in diameter where it attaches to its vertebra, and tapers to a point about 3 meters away. The last meter or so of each rib goes from being the diameter of a pencil to the diameter of a mechanical pencil lead. They just sort of peter out into nothingness.
- The fact that even the pencil-lead-sized wisps of the cervical ribs are still in articulation suggests pretty strongly that the neck was buried with the muscles intact.
- If the neck had simply been broken transversely (like a guillotine cut), the two most anterior vertebrae in the preserved block of four should have the cervical ribs of even more anterior vertebrae beneath them, and the cervical ribs from the two most posterior vertebrae would not stick out the back of the preserved block.
- The facts that the cervical ribs from the missing anterior vertebrae are also missing, and that the cervical ribs from the preserved vertebrae trail behind the articulated block, suggest that the neck was pulled apart lengthwise, as shown in B.
- None of the vertebrae have any teeth marks or any sign of mechanical damage, other than the missing neural spine from the third preserved vertebra. The front third of the first preserved vertebra was eroded away before the vertebrae were discovered in the field.
- Assuming that Sauroposeidon was built like Brachiosaurus, it must have had a body mass somewhere between 40 and 60 tons. Even if it was built more like Mamenchisaurus—hellacious neck tacked on fairly dinky body–it was still probably a 20-ton critter.
- After 14 years of subsequent erosion and fieldwork, no other sauropod bones have been discovered at the site.
Some questions:
- How did the neck get separated from the body? The body was presumably too big to move, and the neck is too well preserved to have been moved very far.
- What pulled the neck apart?
- How did the neck come apart without disturbing those little pencil-lead cervical rib ends?
I don’t know the answers to those questions, by the way. And I’m open to suggestions.
Here’s my best guess. I think the body stayed put, and the neck floated away. Not far–a few hundred feet would be enough to put the body outside the outcrop area at the holotype site, but not so far that the neck would be all beat up. I think it floated rather than being dragged (by an Acrocanthosaurus, for example) because the vertebrae are all in such good shape and none of them have any tooth marks. I think it floated in calm water because the preservation is so good. I think the neck muscles rotted enough to let the force of the current rip part of the neck away from the base, just like you can pull a cooked chicken neck apart lengthwise without messing up the articulations among the vertebrae in the chunk that breaks free.
All of that will suffice to get the neck separated from the body. What really bugs me is the separation of the anterior part of the neck from the preserved block of vertebrae. It is tempting to think that the anterior part never came off, and that those vertebrae simply eroded away before they were found, like the front third of the most anterior preserved vert. But that can’t be; if those vertebrae were in articulation and just eroded away, we should still have their cervical ribs below the first two preserved verts.
Who knows, maybe the scenario I outlined above is good enough to explain both breaks. For some reason it is just easier to image most of the neck coming off the carcass than to imagine one part of the neck coming off the other part of the neck. But maybe the anteriormost vertebrae were ripped off and floated away first, and then the preserved block came free and floated off on its own later. (The head probably exploded, as these things were wont to do.)
It is worth noting that there are probably only a handful of people alive who have any first-hand experience with how multi-ton animal carcasses are dispersed, and zero people alive who have ever seen a dead sauropod rot. So, like too much in paleontology, what seems plausible or reasonable to me may not line up with objective reality.
BTW, this post fulfills a promise I made in a comment thread here. If we promise a post, we deliver. (We just don’t specify a due date.)
Comments, suggestions, hypotheses, rants, and crank fringe theories welcome.
References:
Sauropod Vertebra Picture of the Week 
