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.


Maisch IV, H.M., Becker, M.A. and Chamberlain Jr, J.A. 2020. 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. Ichnos 27(2): 122-141.

Cast (white) and fossil (gray) great white shark teeth, lingual (tongue) sides.

Something cool came in the mail today: a fossil tooth of a great white shark, Carcharodon carcharias. The root is a bit eroded, but the enamel-covered crown is in great shape, and it’s almost exactly the same size as my cast tooth from a modern great white.

The labial (outer or lip-facing) sides of the same teeth.

I got this for a couple of reasons. One, I wanted a real great white shark tooth to show people alongside my megalodon tooth (for which see the previous post). Extant great whites are quite rightly protected, and their teeth are outside my price range when they are available at all. Fortunately there are zillions of fossil great white teeth to be had.

Also, the cast great white tooth has been kind of a disappointment. It’s so white that it’s actually a letdown, visually. Tactilely it’s great, with all kinds of subtle features on the crown especially, but those features are almost impossible to see or photograph. In the photo above, you can make out some of the long, smooth wrinkles in the enamel of the cast tooth, but the median ridge, which is dead obvious on the fossil tooth, only shows up under very low-angle lighting on the cast. The fossil tooth is just a more interesting and more informative specimen, material and origin aside. Now that I have it, I might try either staining or painting the cast tooth, to see if I can rehabilitate it as a visual object.

This fossil tooth is also noticeably thicker than the cast tooth. I don’t know if that’s serial, individual, population, or evolutionary variation. In the last post I contrasted the proportional thinness of the cast tooth with the robustness of the megalodon tooth; this fossil tooth might fare a little better if subjected to the same comparison. I should have thought to do that when I was taking these photos.

Speaking of comparisons, here’s megalodon to remind everyone who’s boss. There’s no scale bar here, but the cast great white tooth is 65mm from the tip of the crown to the tip of the longer root, and the meg tooth is 155mm between the same points.

Now I have a gleam in my eye of assembling a couple of sets of fossil teeth: one to illustrate the evolution of the modern great white from its less-serrated ancestors, like this diagram from the great white Wikipedia page, and one to illustrate the evolution of megalodon from its side-cusped ancestors, like this diagram from the megalodon page — presuming that current hypotheses for the two lineages are accurate. If I ever get either set done, I’m sure I’ll yap about it here.


I got this thing a while back. I’d always wanted one, and it really does spark joy.

First up: what should we call this critter? AFAIK, the species name has never been in doubt, it’s always been [Somegenus] megalodon. That genus has variously been argued to be Carcharodon (same as the extant great white shark, Carcharodon carcharias), Carcharocles, Otodus, Megaselachus, and probably others. From my limited reading, the current consensus seems to be converging on Otodus, for reasons that seem reasonable to me, but I’m hardly an expert on this problem. It’s not that I think it’s unimportant, more that the generic identity of [Somegenus] megalodon has been historically labile, and as a non-expert I hesitate to come down firmly behind any of the hypotheses. If it’s still Otodus megalodon in another decade, I might take a stand. If you want to do a deep dive on this, check out Kent (2018: 80-85). In the meantime, I’m going to refer to it informally as ‘megalodon’, without italics. Although the actual genus name Megalodon was tragically wasted a fossil clam (true story), I’m confident that no-one, scientist or layperson, will misunderstand when I refer to the humongous extinct megatoothed shark as megalodon.

With that out of the way: wow, that’s a big freakin’ tooth! Here it is again with a scale bar.

The serrations on the sides are very cool. The edges are worn a bit in places, and that plus the visible notch on one side of the tooth (upper left in the photo above) suggests that this tooth was used, as opposed to being a replacement tooth that rotted out of the jaw before it ever had a chance to be deployed. Where ‘used’ means ‘used to punch and then tear immense holes in other animals’. Pretty wild to think about ancient whales dying on this very tooth.

I use this thing at outreach events, and I got a cast tooth of a modern great white shark for comparison. Those great white teeth are 10 bucks at Bone Clones, so I got a bunch of them and gave them to nieces and nephews as stocking stuffers.

Here’s a labeled version. From what I’ve been able to determine (i.e., shark people, please correct me if I’m wrong!), most shark teeth ‘lean’ away from the body midline. Upper teeth of megalodon tend to be very wide, with wide, shallow angles at the base, whereas lower teeth are more dagger-shaped and have a more pronounced basal angle. I’m pretty sure this meg tooth is a lower, and we’re looking at the lingual (tongue) side in this photo (more on that in a bit), so the tooth is facing the same way we are. I think that makes it a left lower tooth. The great white tooth is a probably a left upper, although great whites apparently have one tooth position that leans mesially instead of distally, so I could have that one wrong-sided. The ‘bourlette’ is an area of exposed orthodentine between the root and the enamel that covers the tooth crown (Kent 2018: 86). This tooth is not in perfect shape, there’s been some peeling of the enamel just above the bourlette. 

I think this photo makes the size-comparison point even more clearly.

Worth noting: if the hypothesis that megalodon belongs in Otodus is correct, the similarities between megalodon and the great white shark are convergent; megalodon teeth are Otodus teeth that lost their side-cusps, and great white teeth are basically wider, serrated mako teeth. That level of convergence shouldn’t be surprising to anyone who has seen a thylacine skull. Still, this photo makes it very obvious why Louis Agassiz assigned megalodon to Carcharodon, the great white shark genus, when he named the species back in 1843: the two look a lot alike. (Also: Agassiz didn’t have all the transitional fossils that we do now.)

Boomerang thought, added in post: at least, megalodon teeth look a lot like the upper teeth of great whites. The lower teeth of great whites are much narrower and more mako-esque. 

A couple of features worth noting here. The mesial margin has a little wrinkle, which cannot be damage because the serrations follow the in-folded contour. This seems to be a minor developmental anomaly that is pretty common in megalodon teeth. The distal margin has a distinct notch, also mentioned above, which probably represents feeding damage sustained in life.

Arguably this side-view is even more striking; the megalodon tooth is 2.38 times the length of the great white tooth (155mm vs 65mm on the long side), but more than three times as thick (29mm vs 9mm max thickness), and the blade of the tooth stays proportionally thicker over more of its length. This tooth was built to do some work.

Am I fanboying here? Sure, a little (and not for the first time). Giant extinct monsters are exciting, and I’m happy to celebrate that while also wanting to know more about how they lived.

The thing that surprised me the most while reading up on shark teeth is how they are oriented in the jaws. I’d always assumed that the convex faces (toward the bottom of the above photo) faced outward (labial or lip-facing), and the flat faces (toward the top of the above photo) faced inward (lingual or tongue-facing), but it’s actually opposite. In the photo above, the labial or outward faces are up, and the lingual or inward faces are down. I’m sure this is old hat to shark people, but it hurts my head. Most teeth I know of have their convex faces outward, like human incisors and tyrannosaur premaxillary teeth. Plus, instinctively it seems like predator teeth should curve toward the back of the mouth, but with their flat labial faces and convex lingual faces, most shark teeth seem to curve toward the front (I realize that they may have been placed in the jaws so that they still pointed backwards overall). I was so surprised by this that I did a lot of checking before bringing it up in this post, but it’s clear even in really good photos of live great white sharks with their mouths open. There’s no bigger story here, just me confronting my own misapprehension about animal morphology. Still seems weird.

If you want to know more about how megalodon lived, I’ve included links below to some papers on its size (Shimada 2019, Shimada et al. 2020, Cooper et al. 2020, 2022, Perez et al. 2021), breeding habits and life history (Miller et al. 2018, Shimada et al. 2021, 2022), evolution (Shimada et al. 2016, Kent 2018, Perez et al. 2018), and paleobiology (Maisch et al. 2019, Ballell and Ferron 2021, Miller et al. 2022, Sternes et al. 2022). This is a highly idiosyncratic collection based on like one evening of messing around on Google Scholar. I’m sure I missed tons of important work, so feel free to recommend more refs in the comments.

Oh, like virtually everything else on this site, these photos are freely available under the CC-BY license, so if you want to use them, modify them, etc., go nuts.


FMNH P13018 with me for scale. Photo by Holly Woodward.

Some of the Burpee Museum folks and PaleoFest speakers visited the Field Museum of Natural History in Chicago after the 2020 ‘Fest. I hadn’t been there since 2012, and a lot had changed. More on that in future posts, maybe. Here I am with FMNH 13018, a right femur referred by von Huene (1929) to Argyrosaurus superbus (note, though, that Mannion and Otero 2012 considered this specimen to be Titanosauria indet., hence the hedge in the title of the post). It’s 211cm long, which is pretty darn big but still well short of the record.

Speaking of the record, here’s a list of the largest sauropod femora (as always, updates in the comments are welcome!):

  1. 250cm – Argentinosaurus huinculensis, MLP-DP 46-VIII-21-3 (estimated when complete)
  2. 238cm – Patagotitan mayorum, MPEF-3399/44
  3. 236cm – Patagotitan mayorum, MPEF-PV 3400/27
  4. 235cm – Patagotitan mayorum, MPEF-PV 3400/27
  5. 235cm – “Antarctosaurus” giganteus, MLP 26-316
  6. 214cm – Giraffatitan brancai, XV1
  7. 211cm – cf. Argyrosaurus superbus, FMNH P13018
  8. 203cm – Brachiosaurus altithorax, FMNH P25107
  9. 200cm – Ruyangosaurus giganteus, 41HIII -0002 (estimated when complete)
  10. 191cm – Dreadnoughtus schrani, MPM-PV 1156

The list is necessarily incomplete, because we have no preserved femora for Puertasaurus, Notocolossus, Futalognkosaurus, or the largest individuals of Sauroposeidon and Alamosaurus, all of which probably had femora in the 210-250cm range. For that matter, most elements of the giant Oklahoma apatosaurine are 25%-33% larger than the equivalent bones in CM 3018, which implies a femur length of 223-237cm (scaled up from the 178.5cm femur of CM 3018). I’m deliberately not dealing with Maraapunisaurus or horrifying hypothetical barosaurs here.

In any case, it’s still a prodigious bone, and well worth spending a moment with the next time you’re at the Field Musuem.


  • Mannion, P.D. and Otero, A., 2012. A reappraisal of the Late Cretaceous Argentinean sauropod dinosaur Argyrosaurus superbus, with a description of a new titanosaur genus. Journal of Vertebrate Paleontology, 32(3):614-638.
  • Von Huene, F. 1929. Los saurisquios y ornitisquios del Creta´ceo Argentino. Anales del Museo de La Plata 3:1–196.


The last time we saw the sauropod femur that Paige Wiren discovered sticking out of a riverbank, it had been moved into the prep lab at the Moab Museum, with the idea that it would eventually go on exhibit as a touch specimen for the public to enjoy and be inspired by. That has come to pass.

I was in Moab last month with Drs. Jessie Atterholt and Thierra Nalley and we stopped in the Moab Museum to digitize some vertebrae from SUSA 515, an unusual specimen of Camarasaurus that I’ve blogged about before, and will definitely blog about again. While we were there, we got to see and touch the Wiren femur. The museum folks told us that femur has been the first dinosaur bone that a lot of schoolkids and tourists have seen up close, or gotten to touch. As a former dinosaur-obsessed kid who never stopped being excited about touching real dinosaur bones–and as one of the lucky folks that got to rescue this particular fossil from erosion or poaching–that pleases me deeply. 

So, obviously, you should go see this thing. And the rest of the museum–as you can see from the photos above, the whole place has been renovated, and there are lots of interesting fossils from central and eastern Utah on display, not to mention loads of historical artifacts, all nicely presented in a clean, open, well-lit space that invites exploration. Go have fun!

I have the honor of giving the National Fossil Day Virtual Lecture for The Museums of Western Colorado – Dinosaur Journey, next Wednesday, October 13, from 7:00 to 8:00 PM, Mountain Daylight Time. The title of my talk is “Lost Giants of the Jurassic” but it’s mostly going to be about Brachiosaurus. And since I have a whole hour to fill, I’m gonna kitchen-sink this sucker and put in all the good stuff, even more than last time. The talk is virtual (via Zoom) and free, and you can register at this link.

The photo up top is from this July. That’s John Foster (standing) and me (crouching) with the complete right humerus of Brachiosaurus that we got out of the ground in 2019; that story is here. The humerus is in the prep lab at the Utah Field House of Natural History State Park Museum in Vernal, and if you go there, you can peer through the tall glass windows between the museum’s central atrium and the prep lab and see it for yourself.

If you’ve forgotten what a humerus like that looks like in context, here’s the mounted Brachiosaurus skeleton at the North American Museum of Ancient Life with my research student, Kaelen Kay, for scale. Kaelen is 5’8″ (173cm) and as you can see, she can just get her hand on the animal’s elbow. The humerus–in this case, a cast of the right humerus from the Brachiosaurus altithorax holotype–is the next bone up the line. Kaelen came out with us this summer and helped dig up some more of our brachiosaur–more on that story in the near future.

Want more Brachiosaurus? Tune in next week. Here’s that registration link again. I hope to see you there!

What a dream I had!

January 31, 2021

Oh, hey, so you know how the most tedious thing you can ever hear is someone recounting one of their dreams? I want to tell you about a dream I had last night.

Brian Curtice’s grandfather was in a position of authority to express condemnation of a group of people who had lost the electronic archives of the Daily Telegraph, but declined to do so. So I became part of a woke mob that went to Curtice’s house to express our displeasure to him. I got distracted by an outbuilding when we arrived, went in, and found that it contained the Sonorosaurus type material, which for some reason included two really nice scapulocoracoids. At that point my Index Data colleague Wayne (also part of the woke mob) wandered in and I expressed to him that I was having second thoughts about this whole protest and that my first concern now was protecting the holotype against the more indiscriminate members of the mob. But I kept thinking to myself “Why is this material even here? If anything, it should be in an outbuilding at Kevin Ratkevic’s house.” Then Wayne and I spotted a bunch of computer monitors running software that Curtice had written earlier in his life, and it became apparent that he was the creator of a Commodore 64 adventure game called Pilgrim for which the publishers had ripped off an 8×8 old-English-style character set that I had used in a game I’d published with them.

Ratkevic (1988:figure 4).Lower hind limb including tibia, fibula, and nearly complete left pes of Sonorasaurus thompsoni holotype ASDM 500. Elements found associated but not articulated. Entire assembled length 137 cm. Photo by Jeanne Broome.

So. I never remember dreams in this kind of detail. The fact that I did on this on occasion is strange to me — but then, these are strange times. A quick run-down of what is and isn’t true:

  • So far as I know, the Daily Telegraph archives have not been lost.
  • Brian Curtice is a sauropod palaeontologist, maybe best known for his work reassessing Jensen’s Dry Mesa sauropods (e.g. Curtice et al. 1996, Curtice and Stadtman 2001); I have no idea if he has a grandfather and whether he has any involvement with archives.
  • I do not know where Brian lives, or whether he has any fossils at his house. I highly doubt he has holotypes.
  • The holotype of Sonorasaurus does not include any shoulder-girdle material, but it was indeed described by Ratkevich (1988) — but Ron, not Kevin.
  • There really was a Commodore 64 adventure game called Pilgrim, published by CRL, and they really did re-use — without my permission — the character set I had defined in The Causes of Chaos, which I had published with them not long before.
  • But Pilgrim was by Rod Pike, and I very highly doubt that Brian Curtice, even if he was a C64 programmer in the early-mid 90s, ever published any games with a UK-based software house.

Matt’s response when I told him about this dream:

Just got to the scapulocoracoids and LLOL
“my first concern now was protecting the holotype against the more indiscriminate members of the mob.” LLOL x infinity
Well, I gotta tell you, that was a ride.
Jurassic-Park-style, through your hindbrain.
It had everything!
Woke mobs, holotypes, old school adventure games, intellectual property (at the start and at the end)
lost archives
this is so specific in so many weirdly-specialized areas that whole schools may spring up to interpret it. You might accidentally found a new religion.

All right, folks: interpret for me!


  • Curtice, Brian D., Kenneth L. Stadtman and Linda J. Curtice. 1996. A reassessment of Ultrasauros macintoshi (Jensen, 1985). The continental Jurassic (M. Morales, ed.): Museum of Northern Arizona Bulletin 60:87–95.
  • Curtice, Brian D. and Kenneth L. Stadtman. 2001. The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae. Western Association of Vertebrate Paleontologists and Mesa Southwest Museum and Southwest Paleontologists Symposium, Bulletin 8:33–40.
  • Ratkevich, Ron. 1998. New Cretaceous brachiosaurid dinosaur, Sonorasaurus thompsoni gen et sp. nov, from Arizona. Journal of the Arizona-Nevada Academy of Science 31:71–82.

These things just catch my eye, I can’t help it.

Left: Oddbins corkscrew, circa 1997. Right: left femur of Patagotitan mayorum, circa 100,000,000 BC.

Note that the corkscrew features a distinct medially directed femoral head, the bulge in the lateral margin of the proximal portion that is characteristic of titanosaurs, and a straight shaft. OK, it’s missing tibial and fibular condyles at the distant end, but you can’t have everything.


Here’s one of my most prized possessions: a cannon bone from a giraffe. I got it last fall from Necromance, a cool natural history store in LA. Originally they had a matched pair on display in the front window. Jessie Atterholt got one of them last summer, and I got the other a few months later.

The cannon bones of hoofed mammals consist of fused metacarpals (in the forelimbs) or metatarsals (in the hindlimbs). In this case, the giraffe cannon bone in the top photo is the one from the right forelimb, consisting of the fused 3rd and 4th metacarpals, which correspond to the bones in the human hand leading to the middle and ring fingers. Only my third metacarpal is traced in the top photo. For maximum homology goodness I should have traced MC4, too, but I’m lazy.

I didn’t know that this was a right forelimb cannon bone when I got it. In fact, I only figured that out this afternoon, thanks to the figures and text descriptions in Rios et al. (2016), which I got free through Palaeontologia Electronica (you can too). The weirdly large and perfectly circular holes at the ends of my cannon bone were clearly drilled out by somone, I guess maybe for mounting purposes? At first I thought it might have been to help the marrow cook out of the shaft of the bone during simmering and degreasing, but none of the drilled holes intersect the main marrow cavity, they’re just in the sponge of trabecular bone at the ends of the element.

This post is a sequel to one from last year, “Brachiosaurus and human metacarpals compared“, which featured metacarpal 3 from BYU 4744, the partial skeleton of Brachiosaurus from Potter Creek, Colorado. I know what everyone’s thinking: can we make these two high-browsing giants throw hands?

Yes, yes we can. The giraffe cannon bone is 75.5cm long, and the brachiosaur metacarpal is 57cm long, or 75.5% the length of the giraffe element. I scaled the two bones correctly in the above image. My hands aren’t the same size because they’re at different distances from the camera, illustrating the age-old dictum that scale bars are not to be trusted.

The Potter Creek brachiosaur is one of the largest in the world–here’s me with a cast of its humerus–but ‘my’ giraffe is not. World-record giraffes are about 19 feet tall (5.8m), and doing some quick-and-dirty cross-scaling using the skeleton photo above suggests that the metacarpal cannon bone in a world-record giraffe should be pushing 90cm. So the giraffe my cannon bone is from was probably between 15.5 and 16 feet tall (4.7-4.9m), which is still nothing to sniff at.

I don’t know how this bone came to be at Necromance. I assume from an estate sale or something. I only visited for the first time last year, and at that time they had three real bones from giraffes out in the showroom: the two cannon bones and a cervical vertebra. They might have put out more stuff since–it’s been about six months since I’ve been there–but all of the giraffe bones they had at that point have been snapped up by WesternU anatomists. Jessie and I got the cannon bones, and Thierra Nalley got the cervical vertebra, which is fair since she works on the evolution of necks (mostly in primates–see her Google Scholar page here). I don’t know if there are any photos of Thierra’s cervical online, but Jessie did an Instagram post on her cannon bone, which is nearly as long as her whole damn leg.

There will be more anatomy coming along soon, and probably some noodling about sauropods. Stay tuned!


Ríos M, Danowitz M, Solounias N. 2016. First comprehensive morphological analysis on the metapodials of Giraffidae. Palaeontologia Electronica 19(3):1–39.



Credit: anonymous tattoo, Grant Harding for the caption.

Update. Here is the Instagram post that Grant got this from. Unfortunately it seems to be from an account that specialises in reposting others’ work without attribution, so we don’t know where the tattoo photo originated.