I was googling around some photos, confirming to myself that turtles don’t have cervical ribs, when I stumbled across this monstrosity (and when I use that word I mean it as a compliment):

Softshell turtle Trionyx spinifera, cervicodorsal transition in ventral view, anterior to right. Copyright © Mike Dodd, used by kind permission. Original at https://www.amanita-photolibrary.co.uk/animals/trionyx_spinifera_1496.htm

The specimen is from the collection amassed by Caroline Ponds, formerly a reader in Zoology at Oxford, who picked up most of her specimens as roadkill in Milton Keynes. She has donated this collection to WildCRU (Wildlife Conservation Research Unit) just outside Oxford, just 90 minutes away from me.

The hot news here is of course the zygapophseal articulation between what I am interpreting as the last cervical and the first dorsal. Let’s take a closer look:

As you can see the prezygapophyses of the first dorsal are cylindrical, wrapping smoothly around from a fairly traditional anterodorsal-facing aspect through anterior, anteroventral, ventral, and even posteroventrally-facing. There is no hint of inclination towards the midline as in sane prezygapophyses.

And, providing perfect mates to those prezygs, the postzygapophyses of the last cervical wrap around producing a negative cylinder that encloses the positive one.

This leaves me with questions. Lots of them. For example:

  1. Did I even identify the vertebrae right, or is that “first dorsal” really the last cervical, based on its not carrying a rib? It looks like it’s trying to bear a rib, but not quite carrying it off. (For now I will assume my identification is correct.)
  2. What is the centrum articulation like here? Sadly, it’s obscured in the photo. My guess would be positive cylinder on the front of the dorsal, and a small contact point on the back of the cervical — but it really is just a guess.
  3. Is this unique to Trionyx spinifera, or do all cryptodiran turtles do this to some extent?
  4. If this condition is common among cryptodires, are there  species that take it to an even greater extreme?
  5. What do pleurodire turtles do here?
  6. Why haven’t I spent more of my like looking at the cervicodorsal transitions of turtles?

Just to wash our mouths out after all the theropod-related unpleasantness yesterday:

What we’re seeing here, in glorious 3D, is the 7th cervical vertebrae of BYU 1252-18531. This is an apatosaurine at the Brigham Young University Museum of Paleontology which the museum has catalogued as “Apatosaurus excelsus” (i.e. Brontosaurus excelsus), and which Tschopp et al. (2015) tentatively referred to Brontosaurus parvus, but which I suspect is most likely good old Apatosaurus louisae.

It’s in the rarely seen ventral view, which really emphasizes the ludicrously over-engineered cervical ribs. Get your 3D glasses on and marvel at how they come lunging out of the screen at you, like giant insects in a 1950s B-movie.

So beautiful.

Over on Mastodon (sign up, it’s great!), Jim Kirkland posted a baby Utahraptor caudal vertebrae for #FossilFriday. Here it is:

And after a bit of virtual prep work:

My first reaction was just “That’s pretty!“. My second, which I admit should have been my first, was “Wait a sec — how the heck do those things articulate?

The issue is that both the prezygs and the postzygs overhang the centrum by so much. If we imagine three of these babies consecutively, there are basically two options.

First, the centra articulate closely, with what we might feel intuitively is a reasonable cartilage gap; and the zygs cross over:

Does something like this ever happen? Not in sauropods, for sure, but it could be correct — if the zyg facets are some way short of the tips of their processes, so that the most distal parts of each process are pre-epipophyses and epipophyses rather than prezygs and postzygs per se.

The other interpretation is this, with the zygs overlapping near the end as in sensible dinosaurs, and much more spaced out centra:

If this is right, then (in this respect) baby Utahraptor tails resembled camel necks in having big intervertebral spaces, which in life were filled with big cartilage plugs.

 

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SPOILER SPACE

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Have a think about this before reading on.

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SPOILER SPACE

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OK, here is the horrible truth.

Dromaeosaur tails do overlap their zyg processes as in the first mock-up above: but they do much, much worse than this!

Here is the truly perverted figure 37 of Ostrom’s classic 1969 monograph on Deinonychus — the publication that catalysed the whole Dinosaur Renaissance:

As you can see, the zygapophyseal processes are grotesquely elongated, and overlap in long stiffening bundles with those of successive vertebrae (part C of the figure). The actual zyg facets are small, and close to the origins of these processes (see parts A and B of the figure). And the chevrons are also hideously protracted beyond their natural length to form stiffening bundles beneath the tail that complement those above the tail.

To add insult to injury, the chevrons even face in the wrong darned direction, extending anteriorly along the tail rather than posteriorly as in all decent animals. Yes: in Ostrom’s illustrations, we’re seeing the vertebrae in right lateral view, i.e. anterior is to the right.

All of this confirms that I was so, so right two decades ago to focus so completely on proper dinosaurs instead of these nasty mutant ones. Ugh.

While I was thinking about Diplodocus atlas ribs, I was reminded of the ribs on the atlas of a diplodocine skull-and-three-cervicals exhibit that Matt and I saw at MOAL(*) back in the heady days of the Sauropocalypse.

And that reminded me that I have other pairs of photos from the MOAL visit, which I took with the intention of making anaglyphs. like the one I did of the diplodocine. So here is an anaglyph of a small bipedal ornithischian whose exact identity I evidently didn’t bother to write down:

Does anyone know what this is? Maybe Dryosaurus or something along those lines?

 


(*) When Matt and I visited this museum, it was known as the North American Museum of Ancient Life, or NAMAL for short. Since then, it’s dropped the “North American” and promoted the “of”, and it’s now the Museum Of Ancient Life, or MOAL for short. But we’re sticking with the existing category (see link below) for continuity with other things we’ve posted from there.

 

Last time, I showed you a photo of the head and neck of the London Diplodocus and asked what was wrong. Quite a few of you got it right (including Matt when we were chatting, but I asked him not to give it away by posting a comment). The 100 SV-POW! dollars, with their cash value of $0.00, go to Orribec, who was the first to reply that the atlas (cervical 1) is upside-down.

Here is again, from the other side:

The Natural History Museum’s Carnegie Diplodocus cast, skull and anterior cervical vertebrae in left lateral view. Photograph by Mike Taylor.

I noticed this — when it seems the people putting up the skeleton did not, unless this is a deliberate joke — because I happened to be particularly tuned into atlas ribs at the time. You can see what appears a tiny rib hanging below the atlas, but no neural arch above it projecting up and back to meet the prezygapophyses of the axis (cervical 2). In fact the “cervical rib” on this left side is the neural arch of the right side, rotated 180 degrees about the axis of the neck.

Here’s how this should look, from the Carnegie Museum’s own Diplodocus:

The Carnegie Museum’s Diplodocus mount, skull and anterior cervical vertebrae in left lateral view. Photograph by Matt Lamanna.

In this picture, the atlas seems to be pretty much fused onto the axis, as seen in Gilmore (1936: figure 6) which Matt helpfully reproduced in Tutorial 36.

(Digression 1: you might think that this atlas is the real thing, since the Carnegie’s mount is the one with the real CM 84/94/307 material in it. But no: the atlas does not belong to any of those, which all lack this element. It seems to be a sculpture, but we can’t figure out what it’s based on.)

(Digression 2: you might notice that the London and Carnegie skulls are rather different. That’s because the London cast still has the original skull supplied in 1907, which is a sculpture based on CM 622 (rear) and USNM 2673 (the rest), while the Carnegie’s mount at some point had its skull replaced by a cast of CM 11161 — though no-one knows when.)

(Digression 3: the diplodocine originally catalogued as CM 662, on which the rear of the skull was based, was named as the holotype of a new species Diplodocus hayi by Holland (1924), traded to the Cleveland Museum of Natural History in 1956 where it was numbered CMNH 10670, then traded on the Houston Museum of Natural History in 1963 where istbecame HMNS 175, mounted in  Houston in 1975, remounted between 2013 and 2015, and finally moved to its own new genus Galeamopus by Tschopp et al. 2015. Yes, this stuff gets complicated.)

In fact, it’s amazing how much stuff we actually don’t know about these classic specimens, including the source of the atlas for both the Carnegie mount and the various casts — which are not the same. If only there was a single definitive publication that gathered everything that is known about these mounts. Oh well, maybe some day.

Now everyone knows that all the Carnegie Diplodocus mounts around the world were cast from the same molds, and so they all have the same altas <SCREEEECH> wait what?

The Muséum National d’Histoire Naturelle’s Carnegie Diplodocus cast, posterior part of skull and anterior cervical vertebrae in left lateral view. Photograph by Vincent Reneleau.

Here we are in Paris, and the atlas has these two honking great ribs. I have not seen these in any other Carnegie Diplodocus. I know they’re absent from the Berlin cast (thanks to Daniela Schwarz), from the Vernal re-cast (personal observation) and of course from the London cast. I would welcome observations (or even better, photos) from anyone who’s in a position to look at the Vienna, Bologna, Moscow, La Plata, Madrid or Mexico City casts.

So where did these atlas ribs come from? As with so much of this, no-one really knows. It’s especially mysterious as the Paris mount is supposed to be completely unchanged since its initial mounting. But some clue to the origin of the ribs in this mount is found in Holland (1906:249–250):

Accompanying the elements of the atlas sent to the writer for study by the kindness of Professor Osborn  [i.e. AMNH 969] are two bones, undoubtedly cervical ribs. They are both bones belonging on the right side of the centra. They are reported to have been found at the same place at which the atlas was found. The writer is inclined to think that the larger of these two bones (Fig. 20), was probably the rib of the atlas and indeed it requires but little effort to see that it might very well have served such a function, and that the smaller bone (Fig. 21) was the rib of the axis. Were the stump of the rib which remains attached to the axis in the Carnegie Museum, and which Mr. Hatcher has figured, removed, this smaller rib might take its place and would undoubtedly articulate very neatly to the facet

In case you’re too lazy to go and look at Holland’s illustrations for yourself, here they are.

The atlas rib:

The axis rib:

Holland went on:

In case the view entertained by the writer is correct, the form of the atlas and the axis with their attached ribs would be as given in the accompanying sketch (Fig. 22) rather than as given in the figure which has been published by Mr. Hatcher. Such a location of these parts has in its favor the analogy of the crocodilian skeleton.

Here is that composite atlas/axis complex:

(This arrangement with closely appressed atlas and axis ribs should ring a bell for anyone who’s looked much at croc necks, as for example in Taylor and Wedel 2013:figure 19.)

The atlas ribs on the Paris mount look a decent match for the one illustrated by Holland (1906:figure 20), so it seems a reasonable guess that they were sculpted based on that element. But that only leaves us with two more mysteries:

  1. Why do we see these atlas ribs only on the Paris cast, not in the Carnegie original or any of the other casts (that I know of)?
  2. Why does this cast have atlas ribs based on one of Holland’s elements, but not axis ribs based on the other?

Anyone?

References

 

Last Saturday I was at a wedding at Holy Trinity Brompton, a London church that is conveniently located a ten-minute stroll from the Natural History Museum. As I am currently working on a history paper concerning the Carnegie Diplodocus, I persuaded my wife, my eldest son and his fiancée to join me for a quick scoot around the “Dippy Returns” exhibition.

Here is a photo that I took:

Something is wrong here — and I don’t just mean the NHM exhibition’s stygian lighting.

Who can tell me what it is? $100 in SV-POW! Dollars(*) awaits the first person to get it right in the comments.

 


(*) Cash value: $0.00.

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

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.

In a paper that I’m just finishing up now, we want to include this 1903 photo of Carnegie Museum personnel:

A few weeks ago I asked for help on Twitter in identifying the people shown here, and I got a lot of useful contributions.

But since then I have seen the Carnegie photo library catalogue for this image (it’s #1010), and it gives names as follows:

  • Far left, mostly cropped from image: field worker William H. Utterback
  • Seated, facing right: field worked Olof A. Peterson
  • Standing at back: preparator Louis Coggeshall (Arthur’s brother)
  • Seated, looking to camera: preparator Charles W. Gilmore
  • Seated at far table: field worker Earl Douglass
  • Standing behind far table: chief preparator Arthur S. Coggeshall
  • Sitting at far table, facing left: preparator Asher W. VanKirk
  • Seated: illustrator Sydney Prentice
  • Sitting on bench: John Bell Hatcher, whose description of Diplodocus carnegii had been published two years previously

Those of you who know a bit of history, do these identifications seem good? Some of the suggestions I got align well with these, but others do not. For example, a lot of people thought that the person here identified as Louis Coggeshall was his better-known brother Arthur.

I’d appreciate any confirmation or contradiction.

Couple of fun things here. First, if you’d like to play with — or print — 3D models of megalodon teeth, there are a bunch of them on Sketchfab, helpfully curated by Thomas Flynn, the Cultural Heritage Lead there. As of this writing there are 24 meg teeth in the collection (link), and by my count 14 of them are downloadable, 11 for free and 3 for sale. If you’re not already on the ‘fab, it takes like 2 minutes to create a free account, and then all you gotta do is click on the download icon next to each freely downloadable tooth.

Second, I obviously named this post series after Shark Week on the Discovery Channel, but the sad fact is that Discovery Channel documentaries long ago took a steep nose dive into being mostly garbage. I guess if you like seeing the same footage half a dozen times in a 40-minute documentary, being repeatedly beaten over the head with the same three very basic facts (or, too often, “facts”), and wondering which thing the creators have more contempt for, the actual science or you, the audience, then go ahead, knock yourself out.

If, on the other hand, you like non-repetitive, vibrant footage, non-repetitive, useful and informative narration, and coherent programming you can actually learn from, let me suggest the Free Documentary – Nature channel on YouTube.

“Rise of the Great White Shark – A History 11 Million Years in the Making” is excellent, with tons of great footage and some very nicely-done explanations of the sensory and thermoregulatory adaptations of great whites and other sharks — and, whaddayaknow, a fact-based, non-sensationalized, and still awesome segment on megalodon.

I also learned a lot from “Shark Business”, about the growing ecotourism business of boat- and scuba-based shark tours or shark encounters. Two things in particular stood out: first, because sharks don’t have hands, their exploratory way of interacting with objects in their environment is to give everything a test bite. The vast majority of shark “attacks” on humans consist of a single bite, with a quick disengagement and no pursuit of the human by the shark. It’s just that sharks have super-sharp teeth and incredibly powerful jaws, and even a comparative gentle (to the shark) test bite can leave a person severely injured or dead. That sharks most often don’t intend any harm is probably cold comfort to people who have been subject to test bites, but it’s a useful thing to understand if you’re genuinely interested in sharks.

The other thing that jumped out at me is the 50-second segment that starts at 7:45, in which a tour guide is shown pushing on the snouts of great white sharks with his bare fingers as they approach the boat. The sharks roll their eyes back, open their mouths, and seem to go catatonic for a bit. Although they don’t make this connection explicitly in the doc, sharks generally roll their eyes back when they go in for a bite, presumably to protect their eyes from the object they’re sampling. I wonder if the nose touch signals to the shark that it’s bite time, and it rolls its eyes back, opens its mouth, and waits for something to bite down on. It seems like a useful thing to be aware of in case a shark is ever coming at you — a gentle push on the snout might put the shark into zombie mode for long enough to get out of the way. On the flip side, if you push the shark’s snoot and don’t get out of the way, it might be super-primed to take a hunk out of you. Note: I am not a shark expert, this is not professional advice, and I assume no liability if a shark eats your arm off. I just thought it was an interesting bit of shark biology that could conceivably pay off in an emergency.

Is this really going to be a whole week of shark posts? Beats me! I’m making this up as I go. Let’s find out.

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.