Turkeys lie

December 18, 2018

We all know what turkeys look like, right?

Turns out that two thirds of that bird is a lie. Here’s a diagram produced for hunters on which part of the turkey to shoot. (It’s all over the Internet, and I can’t trace the original source, but I got it from here):

Bascially, if you fire an arrow at a visible turkey, there’s a 2/3 chance that it’ll pass straight through feathers and completely miss the actual bird.

Now, then: what do we think a theropod looked like in life? Probably not much like what skeleton reconstructions show as the flesh envlope, as for example in Scott Hartman’s Guanlong:

Instead, it might have looked like this:

(Note: this is not in any way a criticism of Scott’s fine work, which is a scientific restoration of the soft tissue, and does not address integument at all.)

And now that pterosaurs have feathers, too(*), we have to assume that they, too, probably had body outlines bearing little resemblance to the flesh-on-bone shapes we’ve been used to seeing.

 


(*) As Matt pointed out: “I can’t be bothered to write “integumentary structures” when I mean “feathers”. I realize they may be independently derived, but eyes evolved independently like 40 times and we don’t refer to the other 39 instances as “photoreceptive structures”.” (He actually wrote “I can’t be arsed”, but I changed it to “bothered” to make him appear more professional.)

 

Matt’s last post contained a nice overview of the occurrence of epipophyses in sauropodomorphs: that is, bony insertion points for epaxial ligaments and muscles above the postzygapophyseal facets. What we’ve not mentioned so far is that these structures are not limited to sauropods. Back when we were preparing one of the earlier drafts of the paper that eventually became Why sauropods had long necks; and why giraffes have short necks (Taylor and Wedel 2013a), I explored their occurrence in related groups. But that section never got written up for the manuscript, and now seems as good a time as any to fix that.

Theropods (including birds)

Most obviously, epipophyses occur in theropods, the sister group of sauropodomorphs.

Taylor and Wedel (2013a: figure 11). Archosaur cervical vertebrae in posterior view, Showing muscle attachment points in phylogenetic context. Blue arrows indicate epaxial muscles attaching to neural spines, red arrows indicate epaxial muscles attaching to epipophyses, and green arrows indicate hypaxial muscles attaching to cervical ribs. While hypaxial musculature anchors consistently on the cervical ribs, the principle epaxial muscle migrate from the neural spine in crocodilians to the epipophyses in non-avial theropods and modern birds, with either or both sets of muscles being significant in sauropods. 1, fifth cervical vertebra of Alligator mississippiensis, MCZ 81457, traced from 3D scans by Leon Claessens, courtesy of MCZ. Epipophyses are absent. 2, eighth cervical vertebra of Giraffatitan brancai paralectotype HMN SII, traced from Janensch (1950, figures 43 and 46). 3, eleventh cervical vertebra of Camarasaurus supremus, reconstruction within AMNH 5761/X, “cervical series I”, modified from Osborn and Mook (1921, plate LXVII). 4, fifth cervical vertebra of the abelisaurid theropod Majungasaurus crenatissimus,UA 8678, traced from O’Connor (2007, figures 8 and 20). 5, seventh cervical vertebra of a turkey, Meleagris gallopavo, traced from photographs by MPT.

Taylor and Wedel (2013a: figure 11). Archosaur cervical vertebrae in posterior view, Showing muscle attachment points in phylogenetic context. Blue arrows indicate epaxial muscles attaching to neural spines, red arrows indicate epaxial muscles attaching to epipophyses, and green arrows indicate hypaxial muscles attaching to cervical ribs. While hypaxial musculature anchors consistently on the cervical ribs, the principle epaxial muscle migrate from the neural spine in crocodilians to the epipophyses in non-avial theropods and modern birds, with either or both sets of muscles being significant in sauropods. 1, fifth cervical vertebra of Alligator mississippiensis, MCZ 81457, traced from 3D scans by Leon Claessens, courtesy of MCZ. Epipophyses are absent. 2, eighth cervical vertebra of Giraffatitan brancai paralectotype HMN SII, traced from Janensch (1950, figures 43 and 46). 3, eleventh cervical vertebra of Camarasaurus supremus, reconstruction within AMNH 5761/X, “cervical series I”, modified from Osborn and Mook (1921, plate LXVII). 4, fifth cervical vertebra of the abelisaurid theropod Majungasaurus crenatissimus,UA 8678, traced from O’Connor (2007, figures 8 and 20). 5, seventh cervical vertebra of a turkey, Meleagris gallopavo, traced from photographs by MPT.

In this figure from the 2013 paper, the rightmost images show cervical vertebrae of Majungasaurus (an abelisaurid theropod) and a turkey, both in posterior view. The red arrows indicate epaxial musculature pulling on the epipophyses. They are particularly prominent in Majungasaurus, rising almost a full centrum’s height above the postzygapophyseal facets.

The epipophyses are very prominent in the anterior cervicals of Tyrannosaurus, but much less so in its posterior cervicals — presumably because its flesh-tearing moves involved pulling upwards more strongly on the anterior part of the neck. Here’s a photo of the AMNH mount, from our post T. rex‘s neck is pathetic:

amnh-tyrannosaurus-is-pathetic

You can see something similar in the neck of Allosaurus, and the trend generally seems to be widespread among theropods.

Ornithischians

Note the very prominent epipophyses protruding above the postzygs in the anterior cervicals of this Heterodontosaurus in the AMNH public gallery:

Cast of AMNH 28471, Heterodontosaurus tucki, collected from the Early Jurassic Voisana, Herschel district, South Africa. Anterior to the left.

Cast of AMNH 28471, Heterodontosaurus tucki, collected from the Early Jurassic Voisana, Herschel district, South Africa. Neck in left lateral view.

Here’s the hadrosaur Corythosaurus:

AMNH 5338, Corythosaurus casuarius, from the Campanian of the Red Deer River, Alberta, Canada. Collected by Barnum Brown and P. C. Kaisen, 1914. Cervicals 1-4 in right lateral view.

AMNH 5338, Corythosaurus casuarius, from the Campanian of the Red Deer River, Alberta, Canada. Collected by Barnum Brown and P. C. Kaisen, 1914. Cervicals 1-4 in right lateral view.

The prominent vertebra is C2: note that is has both a modest blade-like neural spine and prominent epipophyses — but that already by C3 the epipophyses are gone. Here is that C2 postzyg/epipophyses complex is close-up, clearly showing anteroposteriorly directed striations on the epipophysis, presumably representing the orientation of the attaching ligaments and muscles:

As previous image: close-up of posterior part of C2.

As previous image: close-up of posterior part of C2.

Here’s a close-up of the neck of the boring ornithopod Tenontosaurus, also in the AMNH gallery. (I’m not sure of the specimen number — if anyone can clarify, please leave a comment).

AMNH ?3554, Tenontosaurus tilletti, cervcials 2-4 in right lateral view.

AMNH ?3554, Tenontosaurus tilletti, cervicals 2-4 in right lateral view.

The interesting thing here is that it its axis (C2) seems to lack epipophyses (unlike C3), and to have a tall blade-like neural spine, as seen in mammals. We don’t really see C2 spines this big in other dinosaurs — compare with the much more modest spine in Corythosaurus, above. The texture of this part of the Tenontosaurus specimen looks suspicious, and I wonder whether that neural spine is a fabrication, created back in the day by AMNH staff who were so used to mammals that they “knew” what a C2 should look like? Anyway, the epipophysis above the postzyg of C3 is very distinct and definitely real bone.

Pterosaurs

Things get much more difficult with pterosaurs, because their cervicals are so fragile and easily crushed (like the rest of their skeleton, to be fair). While it’s easy to find nice, well-preserved ornithischian necks on display, you don’t ever really see anything similar for pterosaurs.

As a result, we have to rely on specimen photographs from collections, or more often on interpretive drawings. Even high-resolution photos, such as the one in Frey and Tischlinger (2012: fig 2) tend not to show the kind of detail we need. Usually, the only usable information comes from drawings made by people who have worked on the specimens.

Here, for example, is Rhamphorhynchus, well known as the most difficult pterosaur to spell, in figure 7 from Bonde and Christiansen’s (2003) paper on its axial pneumaticity:

BondeChristiansen2003-axial-pneumaticity-of-rhamphorhynchus-fig7It’s not the main point of the illustration, but you can make out clear epipophyses extending posteriorly past the postzygapophyseal facets in at least C3 and C5 — in C4, the relevant area is obscured by a rib. (Note that the vertebrae are upside down in this illustration, so you need to be looking towards the bottom of the picture.)

I’m pretty sure I’ve seen a better illustration of Rhamphorhynchus epipophyses, but as I get older my memory for Rhamphorhynchus epipophyses is no longer what it used to be and I can’t remember where. Can anyone help?

But also of interest is the azhdarchid pterosaur Phosphatodraco, here illustrated by Pereda Suberbiola et al. (2003):

Pereda Suberbiola et al. (2003: fig. 3). Phosphatodraco mauritanicus gen. et sp. nov, OCP DEK/GE 111, Late Cretaceous (Maastrichtian), Morocco: (a) cervical five in two fragments, ventral and left lateral views; (b) cervical six in ventrolateral view; (c) cervical seven in ventral view; (d) cervical eight in left lateral view; (e) cervical nine in posterior view; (f) cervical six in anterior view. c, centrum; co, condyle; ct, cotyle; hyp, hypapophysis; nc, neural canal; ns, neural spine; poe, postexapophysis; poz, postzygapophysis; prz, prezygapophysis; su, sulcus; tp, transverse process.

Pereda Suberbiola et al. (2003: fig. 3). Phosphatodraco mauritanicus gen. et sp. nov, OCP DEK/GE 111, Late Cretaceous (Maastrichtian), Morocco: (a) cervical five in two fragments, ventral and left lateral views; (b) cervical six in ventrolateral view; (c) cervical seven in ventral view; (d) cervical eight in left lateral view; (e) cervical nine in posterior view; (f) cervical six in anterior view. c, centrum; co, condyle; ct, cotyle; hyp, hypapophysis; nc, neural canal; ns, neural spine; poe, postexapophysis; poz, postzygapophysis; prz, prezygapophysis; su, sulcus; tp, transverse process.

The cervicals of Phosphatodraco seem to have no epipophyses. So they were not ubiquitous in pterosaurs.

What does it all mean? This post has become a bit of a monster already so I’ll save the conclusion for another time. Stay tuned for more hot epipophyseal action!

References

  • Bonde, Niels and Per Christiansen. 2003. The detailed anatomy of Rhamphorhynchus: axial pneumaticity and its implications. pp 217-232 in: E. Buffetaut and J-M Mazin (eds), Evolution and Palaeobiology of Pterosaurs. Geological Society, London, Special Publications 217. doi:10.1144/GSL.SP.2003.217.01.13
  • Frey Eberhard and Helmut Tischlinger. 2012. The Late Jurassic Pterosaur Rhamphorhynchus, a Frequent Victim of the Ganoid Fish Aspidorhynchus? PLoS ONE 7(3):e31945. doi:10.1371/journal.pone.0031945
  • Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica, Supplement 7 3:27-93.
  • O’Connor Patrick M. 2007. The postcranial axial skeleton of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. pp 127-162 in: S. D. Sampson., D. W. Krause (eds), Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Society of Vertebrate Paleontology Memoir 8.
  • Osborn, Henry F., and Charles C. Mook. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, New Series 3:247-387.
  • Pereda Suberbiola, Xabier, Nathalie Bardet, Stéphane Jouve, Mohamed Iarochène, Baadi Bouya and Mbarek Amaghzaz. 2003. A new azhdarchid pterosaur from the Late Cretaceous phosphates of Morocco. pp 79-90 in: E. Buffetaut and J-M Mazin (eds), Evolution and Palaeobiology of Pterosaurs. Geological Society, London, Special Publications 217. doi:10.1144/GSL.SP.2003.217.01.08
  • Taylor, Michael P., and Mathew J. Wedel. 2013. Why sauropods had long necks; and why giraffes have short necks. PeerJ 1:e36 doi:10.7717/peerj.36

Illustration talk slide 35

Illustration talk slide 36

Illustration talk slide 37

Illustration talk slide 38

Link from second slide. Other posts in this series.

Reference:

Osborn, Henry Fairfield, and Charles C. Mook. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, n.s. 3:247-387, and plates LX-LXXXV.

Recently I had the opportunity to give a talk on photographing specimens and preparing illustrations in Jim Parham‘s phylogenetics course at Cal State Fullerton. Jim is having each student (1) write a description of a specimen, (2) run a phylogenetic analysis, and (3) do some kind of calibration on their tree. I think that’s rad.

Anyway, it was fun talk and I wanted to put it up for everyone, but Mike had the idea of posting a batch of slides at a time, to hopefully fire some discussion on different aspects of photography and illustration. So if you’re impatient to see the whole thing, blame him! I will post the whole talk at the end of the post series, and you can find all of the talk posts here.

And now, on with the show.

Illustration talk slide 1

Illustration talk slide 2

Illustration talk slide 3

Illustration talk slide 4

Illustration talk slide 5

Illustration talk slide 6

Illustration talk slide 7

Illustration talk slide 8

For a paper that I and Matt are preparing, we needed to measure the centrum length of a bunch of turkey cervicals. That turns out to be harder than you’d think, because of the curious negative curvature of the articular surfaces.

turkey-cervical-c7-white

Above is a C7 from a turkey: anterior view on the left; dorsal, left lateral and ventral views in the middle row; and posterior on the right. As you can see from the anterior, dorsal and ventral views, the anterior articular surface[1] is convex dorsoventrally  but concave transversely; and as you can see from the lateral view, the posterior face is concave dorsoventrally and convex transversely.

This means you can’t just put calipers around the vertebra. If you approach the vertebra from the top or bottom, then the upper or lower lip of the posterior articular surface will protrude past the centre of the saddle, and give you too long a length. If you approach from the side, the same will happen with the left and right lips of the anterior articular surface.

What are we trying to measure anyway?

But this raises the question of what it is we’re trying to measure. I said “we needed to measure the centrum length of a bunch of turkey cervicals”, but what exactly is centrum length? Why shouldn’t the upper and lower lips of the posterior articular surface count towards it?

What does centrum length mean?

The problem doesn’t only arise with bird cervicals. The same issue arises in measuring more sensible and elegant vertebrae, such as our old friend HMN SII:C8, or MB.R.2181:C8 as we must now learn to call it.

Janensch1950-fig43-sii-c8-MEASUREMENTS

Although the back of the vertebra is nice and simple here — it’s obvious what line we’re measuring to at the back — we have three choices of where the “front” of the vertebra is, and a case can be made for any of them as being “the length of the vertebra”.

The longest measurement (here marked “T” for “total length”) goes to the front of the prezygapophyseal rami. The next one (“C” for “centrum length”) goes to the anteriormost point of the condyle. The distinction is important: as noted recently, the longest vertebra in the world belongs to Sauroposeidon if we use total length, but to Supersaurus if we use centrum length.

But in life, most of the condyle would be buried in the cotyle of the preceding vertebra. So should it count towards the length of the vertebra? If you consider a string of articulated vertebrae, the buried condyles don’t contribute to the overall length of the neck. So Matt and I call the length from the posterior margin of the condyle to the posterior margin of the cotyle the functional length (marked “F” above), which I believe is a new term.

Another way to think of the functional length is the distance from a given point on a vertebra (in this case the posterior margin of the cotyle) to the same point on the adjacent vertebra:

Janensch1950-fig43-sii-c8-MEASUREMENTS2

For our current project, Matt and I are interested in how the lengths of individual vertebrae contribute to total neck length, so for our purposes, functional length is definitely what we want.

By the way, Janensch is the only author I know of to have even recognised the importance of functional length. The measurement tables on pages 39 and 44 have columns for “Gesamtlänge des Wirbels ab Vorderende per Präzygapophyse”, “Gesamtlänge der Wirbel-Körpers in 1/2 Höhe” and “Länge der Wirbel-körpers ohne Condylus in 1/2 Höhe” — that is, “Total length of the vertebra from the anterior end of the prezygapophysis”, “Total length of the centrum measured at mid-height” and “Length of the centrum minus condyle at mid-height”. This is typical of his careful and methodical approach. Kudos!

Hey! I thought this was about turkeys

And so it is. Here is the functional length measurement for a turkey cervical:

turkey-cervical-c7-white-MEASUREMENT

It’s the shortest anteroposterior distance between the two articular surfaces.

Measuring functional length

Matt and I chatted about this at some length, and I am ashamed to say that we thought through all sorts of complicated solution involving subtracting measurements from known scaffold length and suchlike.

It took us a stupidly long to to arrive at the very obvious solution, which is just to modify the calipers to have a “tooth” that can protrude into the concavity of the anterior articulation between its left and right lips. Easily done with a flat-ended screw and a blob of wood glue:

IMG_1000

With the measurements of all the vertebrae in my series, I can now fairly confidently expect that the sum of the individual lengths will come out at about the length of the complete neck.

You know, unless intervertebral cartilage turns out to be important or something.

References

  • Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.

 

Footnotes

1. Matt and I are so used to opisthocoelous sauropod presacrals that when we’re talking about vertebrae — any vertebrae — we tend to say “condyle” and “cotyle” for the anterior and posterior articular surfaces, no matter what their morphology. When talking about crocodile cervicals or titanosaur caudals, we’re even likely to say ridiculous things like “the condyle is concave and the cotyle is convex”. Nonsense, of course: condyle means “A rounded prominence at the end of a bone, most often for articulation with another bone.” What we should say is “the condyle is at the back and the cotyle is in front”.

I’ve measured a few necks in my time, including the neck of a baby giraffe. I can tell you from experience that necks are awkward things to measure, even if they have been conveniently divested of their heads and torsos. They have a tendency to curl up, which impedes attempts to find the straight-line length. Even when you manage to hold them straight, you want them maximally compressed end-to-end rather than stretched out, which is hard to achieve without buckling them out of the straight line. And then you need to measure between perpendiculars in a straight line.

Awkward.

Tonight, I needed to measure the mass and length of seven turkey necks. (Never mind why, all will become clear in time.) And I found a way to do it that works much better than anything I’ve done before.

Here’s the equipment:

IMG_0961-equipment

You will need:

  • Kitchen scales (for weighing the necks)
  • Small numbered labels (for the sandwich bags that the necks will go into for the freezer once they’ve been measured)
  • Pen and paper to take down the measurements
  • Translucent ruler
  • Saucepan full of turkey necks
  • Slightly less than one half of a birthday cake decorated like a map of Middle-earth [optional]
  • A Duplo baseboard (double-sized Lego) and about fifteen 4×2 bricks

Use the bricks to build an L-shaped bracket on the board — about half way back, so that can rest your hand in front of it.

IMG_0963-straightened

Now you can push the neck into the angle of the bracket. By keeping it pressed firmly against the back wall (yellow in my construction), you can keep it straight. I find the best way to get the neck exactly abutting the left (red) wall is to start with the neck in its natural position, with the anterior and posterior ends curving towards you, then sort of unroll it against the back wall, and finally push the posterior end into place with your little finger (see below). There is a satisfying moment– almost a click — as the back end pops into place and the neck slides along a little to right as necessary to accommodate the added length.

IMG_0966-blocked

Now use another brick (blue in this photo) as a bracket: slide it along the back wall from right to left until it’s solidly abutting the anteriormost vertebra. If you do this right, there is very little travel: the entire series of vertebrae is lined up and solidly abutted, with bone pushing against the left wall and your new brick. I find there’s less than half a millimeter of variation between the length under gentle-but-firm pressure (which is what I measured) and under the very strongest force you can exert without buckling the neck.

IMG_0967-measured

Once you have found the blue brick’s correct position, you need to hold it firmly in place and measure its position relative the the left wall. (It doesn’t matter if you let the neck re-curl at this point, so long as the blue brick doesn’t shift.)

You need a translucent ruler so that you can lay it across the neck and see where blue brick falls under the scale. (My ruler’s zero is, rather annoyingly, 5 mm from the end; so I needed to subtract 5 mm from the lengths I measured.)

IMG_0969-bagged

Finally, I bagged up each neck in its own sandwich bag, ready for the freezer. Each neck is labelled with a number so that when I take it out for dissection, I will be able to relate the measurements and observations that I make back to these initial measurements.

For the record, here are the measurements:

  • Neck 1: 154 g, 179.5 mm.
  • Neck 2: 122 g, 151 mm.
  • Neck 3: 154 g, 199.5 mm.
  • Neck 4: 133 g, 162.5 mm.
  • Neck 5: 142 g, 169 mm.
  • Neck 6: 80 g, 167 mm.
  • Neck 7: 70 g, 169 mm.

As expected, there is some correlation between neck mass and length; but not as much as you might expect. Naively (i.e. assuming isometric similarity) mass should be proportional to length cubed, but there is a lot of scatter about that line. I don’t know whether that is due to individual variation, or merely because the various necks — all of them incomplete — are different sections of the full neck. Hopefully I will be able to confirm or rule out that possibility when I’ve dissected down to naked vertebrae.

Here at SV-POW! we are ardently pro-turkey. As the largest extant saurischians that one can find at most butchers and grocery stores, turkeys (Meleagris gallopavo) are an important source of delicious, succulent data. With Thanksgiving upon us and Christmas just around the corner, here’s an SV-POW!-centric roundup of turkey-based geekery.

The picture at the top of the post shows a couple of wild turkeys that frequented our campsite in Big Bend in the winter of 2007. Full story here.

If you’re wondering what to do with your turkey, the answer is GRILL IT. I use the recipe (available on Facebook) of my good friend and colleague, Brian Kraatz, who has fallen to the Dark Side and works on mammals–rabbit tooth homology, even (Kraatz et al. 2010)–but still grills a mean theropod. (In his defense, Kraatz has published on extinct saurischians–see Bibi et al. 2006.) My own adventures in turkey grilling are chronicled in this post, which will show you the steps to attaining enlightenment, or at least a larger circumference.

While you’re cooking and eating, you might as well learn something about muscles. This shot of the fanned-out longus colli dorsalis muscles in a turkey neck was the raison d’etre for this post, and turned up again with different muscles labeled in one of the recent Apatosaurus maquette review posts. Mike and I ate those muscles, by the way.

After the meal, you’ll have most of a turkey skeleton to play with. This diagram is from my other ‘holiday dinosaur’ page, which I put together for the Lawrence Hall of Science and UCMP back in 2005. That page has instructions on how to turn your pile of greasy leftovers into a nice set of clean white bones. Tom Holtz is widely acknowledged as King of the Dino-Geeks, and in kingly fashion he took the above diagram and turned the geek-o-meter up to 11. Steel yourself, gentle reader, before checking out the result here.

Speaking of bones, here’s a turkey cervical from Mike’s magisterial work in this area, which first appeared as a tack-on to a post about the holotype dorsal vertebra of the now-defunct genus Ultrasauros. The huge version of the composite photo has its own page on Mike’s website, where it is available in three different background colors. The lateral view also turned up in one of my rhea neck posts.

From the serving platter to publication: when I was young and dumb, I used a photo of a broken turkey vert to illustrate the small air spaces, or camellae, that are commonly found in the pneumatic bones of birds and some sauropods (Wedel and Cifelli 2005:fig. 11F).

I made a much better version by sanding the end off a cleaned-up vertebra, and used that in Wedel (2007), in this popular article on pneumaticity (which has instructions for making your own), and way back in Tutorial 3–only the 12th ever post on SV-POW!

Finally, it would be remiss of me not to point out that turkeys are not only readily accessible, tasty sources of anatomical information, they are also pretty interesting while they’re still alive. Don’t stare at the disgusting freak in the photo above or you might lose your will to eat. Instead, head over to Tetrapod Zoology v2 for Darren’s musings on caruncles, snoods, and other turkey parts that don’t even sound like words.

That does it for now. If you actually follow all of the links in this post, you might just have enough reading to keep you occupied during that post-holiday-meal interval when getting up and moving around is neither desirable nor physically possible. If you’re in the US, have a happy Thanksgiving; if you’re not, have a happy Thursday; and no matter where you are, take a moment to give thanks for turkeys.

References