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Tuesday Tetrapod: Elgaria coerulea

Posted by tigerhawkvok on July 01, 2009 16:12 in tuesday tetrapod

For this week's Tuesday Tetrapod, here is an Elgaria coerulea, or Alligator Lizard, picked up by Rachael's cat last week:

E. coerulea, side

Note the smooth, evently lined-up scales.



E. coerulea, dorsal

Note the dark eyes and dark banding, diagnosing it from E. multicarinata

Note the smooth scaling, which helps protect it. There is a fold of loose lateral skin along its side to let its body expand while it breathes, but still enabling it to be well-protected. Lizards are pretty robust, and this guy later dropped his tail. No idea if he survived, though.

Sorry for the late post, and its brevity!

Edit: Looks like the ID on this is ambiguous. The belly scales are not quite distinct, though possibly mid-scalar; the dorsal patterning is not quite as definitive as it might be. So lets call this "Elgaria spp."

Apparently, R&D is a myth.

Posted by tigerhawkvok on June 26, 2009 15:35 in General , news

So I was reading an article on the WSJ, and, well, I feel it fundamentally misses the point of a cap and trade system. The key mistake in the bill lives here:

[...] As the cap is tightened and companies are stripped of initial opportunities to "offset" their emissions, the price of permits will skyrocket beyond the CBO estimate of $28 per ton of carbon. The corporate costs of buying these expensive permits will be passed to consumers. [...]

This takes place in the context of post-2020 restrictions on CO2 emissions in the proposed Waxman-Markey bill. However, this has the fundamental assumption that overall CO2 emissions will not markedly decrease, and thus there will be fees passed onto the consumer. This is incorrect. The purpose of a cap and trade system is to allow corporations to optomize at their own rates, and those that cannot reduce CO2 emissions in a timely manner can "buy" emissions from other companies that have. However, the fact remains that companies will reduce their overall CO2 emissions. A cap and trade system must have caps that eventually impose exorbitant fees in order to make the R&D of finding more efficient processes the financially responsible one. These R&D fees will briefly be passed onto the consumer only at the end of the cap and trade cycle. Those that invest early in R&D will be able to pay their R&D fees by selling their own CO2 quotas.

I'm not sure how the WSJ missed this point and instead claims:

The hit to GDP is the real threat in this bill. The whole point of cap and trade is to hike the price of electricity and gas so that Americans will use less. These higher prices will show up not just in electricity bills or at the gas station but in every manufactured good, from food to cars. Consumers will cut back on spending, which in turn will cut back on production, which results in fewer jobs created or higher unemployment. [...]

No no no. And then it took its analysis from the Heritage Foundation, a self-identified "conservative think tank"? They too missed the whole point that the only losers in this game are the laggards that fail to innovate, and thus, should fail in a free-market system anyway. Those who innovate too slowly are left holding the bill, while those that did so earlier are already selling products to customers. In any reasonable sense of competition, this also means that if in a given niche one company innovates before the other, the innovator is able to offer its product at lower rates if the competitor takes too long to develop their own methods of reducing CO2.

Sigh. A cap and trade is probably the most economically neutral kick-in-the-pants possible, but some people just don't want it for strict party-line reasons, it seems. I've really not heard a credible response that doesn't put blinders on and ignore R&D / the scientific community.

At a Ren Faire this weekend in Fair Oaks, then work at LHS begins on Monday. Good times.

Definitions, philosophy, and time

Posted by tigerhawkvok on June 23, 2009 13:24 in General

So, a tweet of mine from yesterday has generated a fairly long discussion thread on Facebook. So, I've compiled the entire thing here, for further discussion and for anyone else to weigh in. The tweet in question? "I just realized that while "before" is not defined for "what came before the big bang?", neither is "what", since energy is not defined!" This kicked off with my cousin Michelle:

Interesting philosophy... although I would say you have it wrong. What and before can be defined... it's "came" that I have a problem with.

Dwayne also commented:

No, "before" is defined. However, the definition of "before" depends on the definition of "time", and time is only defined starting from the beginning of the universe. It's more accurate to say that the question is meaningless rather than that the words within the question are undefined.

Then again, I'm not an astrophysicist, so what do I know?

 (More)

Tuesday Tetrapod: Sphenodon spp.

Posted by tigerhawkvok on June 22, 2009 18:17 in tuesday tetrapod

A little bit early, but I have time today! Having covered caudata, avialae, non-avian saurischia, and squamata in the past two weeks, today's post is on the only surviving non-squamate lepidosaur still around: Sphenodon spp., or the Tuatara.

Sphenodon spp.

Sphenodon spp. by Flickr user digitaltrails.

Sphenodon has an interesting history and interesting set of skeletal characterisitcs. One of the most obvious differences is the presence of two, clear, temporal fenestrae, a basal diapsid condition compared to the skull modification of avians and that of squamates, who have lost the lower temporal bar to allow for greater skull kinesis.

Additionally, Sphenodon teeth are acrodont, where the teeth are fused to the jawbone. Thus, its teeth appear as projections of bone from the maxilla and dentary that fit within each other, and terminate at the premaxilla with a beak-like structure, thus the order name "Rhynchocephalia" (beak-head). This beak structure is an outgrowth of bone that replaces the premaxillary teeth during ontegeny. Also notable is the fact that teeth are present on the palatine bones, which is not true for squamates.

Recently, there has been a push to use a new ranked order of "Sphenodontia", though usage is still mixed. There are only two extant species, S. puncatatus and S. guntheri. Their common name, "tuatara", is based on Maori wods for "spines on the back".

The earliest Sphenodon finds are known from the Triassic, where up to nine genera lived in what is now Britain. Significantly for phylogenetic systematics, Triassic sphenodontians show lepidosaurian characteristics such as a thyroid fenestra, fused astragaclus and calcaneum, and a hooked metatrsal 5. The group was diverse through the Mesozoic, but became extinict in Asia and Laurasia by the mid-Cretaceous, and are virtually absent from Cenozoic deposits. Tuatara are classified as ICUN "Vulnerable", with invasive mammals intruding on their niches and consuming their eggs, which is a large hazard. Sphenodon mate about every four years, leaving 5-15 eggs incubating over 11-16 months. Sphenodon utiilize temperature-dependant sex determination, or TSD.

Sources:

  • Benton. Vertebrate Paleontology, 3rd edition. 2005. ISBN 0-632-05637-1.
  • Pough et al. Herpetology, 3rd edition. 2003. ISBN 0-13-100849-8.

Read more about temporal fenestration: The Tree of Life

1 Week Later

Posted by tigerhawkvok on June 20, 2009 19:53 in bliteotw , zombies

So we've been holed up at LHS for a week. There have definitely been arguments; only a few of us have sleeping bags and such pepared, but we have lots of food. The internet has been surprisingly resilient. I think most of the datacenters have essentially no people, and they're running OK. Updates to news reports and such have been getting slowly more sparse. We've made improvised explosives, projectiles, etc. We've been able to pick off the few things that came up this way, but food will be a problem soon. There are probably 50 people here? More? A few of us that came here with the intent of hiding out have weapons, but most are relatively ineffectual. There's been some talk of setting up hunting parties, as barbaric as that sounds. There are some turkeys on the hill, some foxes, etc. There are rabbits and pigeons in the Animal Lab, though none of us has had the courage to cook something that's named yet.

Looks like Kit and Rachel are OK. My folks and sister have holed up at my old high school. They text intermittently. They weren't able to bring much in the ways of chargers so they've ha to cycle through phones being off to preserve the length of their batteries. Looks like they're doing mostly OK, though I'm fuzzy on their situation.

It's not all been good. A couple of the kids went out while we weren't watching. We don't know what happened, but they were pawing ineffectually at the door when we saw them next.

One of the others couldn't deal with it. They took a running jump off the side of the hill. It was a minor favor. Surprisingly long-sited, all things considered.

We definitely didn't talk much that day.

We've set up a sign on the roof. "Survivors as of", with a date spelled out of cans. They know that it's recent, that way.

We're hoping for help, but if not, we have o idea how long holding out here is practical. We're too many people in too little space in a stressful situation, and the bickering will get bad. Its a minor miracle no one is highly religious here. There have been a lot of crazy posts online. I hope we get through this.

More posts later.



That's it for a one-week late "Blog Like It's the End of the World" entry. Hopefully I'll remember next year and follow up this storyline ... it was fun to write! Be sure to read my backdated entry for the initial infection dated on the "real" BLITEOTW date. See this, this, and this for some other stories and background.

Ensatina, Taricha, and TTX Resistance

Posted by tigerhawkvok on June 19, 2009 03:17 in evolution , biology , herpetology

Rather than a longish comment on Rachael's latest post, I thought I'd write up a brief entry on Ensatina.

First, the picture:

Ensatina eschscholtzii eschscholtzii

Ensatina eschscholtzii eschscholtzii, or Monterey subspecies of E. escscholtzii. The "Monterey Salamander", found near Monterey, CA.

Ensatina are an interesting species of salamander in that they are a "ring species", or, they have a sequence of morphotypes that gradually change regionally, and these morphotypes overlap but do not interbreed. There are two terminal morphotypes that are too distantly related to be capable of interbreeding (see Wikipedia's discussion of the subject). The beauty of ring species is that they provide a living sample of speciation and evolution.

In particular, Ensatina in the Bay Area differ from the Monterey morphotype in that they are very morphologically similar to the non-terrestrial stage of Taricha torosa, which are highly toxic to ingest. The tetrodotoxin they produce is a neurotoxin that is potent enough to kill most vertebrates (though some Thamnophis (Garter snakes) have evolved modified sodium channels to enable consumption of them as prey items; see this paper and others for more) (DOI: 10.1007/s10886-005-1345-x). Thus, Ensatina in the Bay Area mimic Taricha presumably to avoid predation.

For those of you curious about the diagnostic differences, an Ensatina is generally smoother than a Taricha, with more prominent costal grooves (the grooves along the side), has nasolabial grooves, and has a constricted base at its tail. The Monterey specimen here lacks the yellow eyes of Taricha, though the Bay Area ecomorph has eyes that are quiet similar to those of Taricha.

Suggested Thamnophis/Taricha studies:

On Parrots

Posted by tigerhawkvok on June 17, 2009 18:59 in General

First, a minor aside: the DMV always sucks, and it sucks more when someone who doesn't speak proper English gives you incorrect instructions, and as a result, you can't take your driving test.

African Grey Parrot, 1

Photo by Flickr user Another Seb

Now, to the main thrust of the post. I have been recently very strongly thinking about adding a pet and picking up a Psittacus erithacus ssp., or an African Grey Parrot. It's a lifetime commitment — they can live to be 50-65 years, with some becoming much older than that.

African Grey Parrot, 2

Photo by Flickr user devlon duthie

As a pet, however, the African Grey (at this very preliminary stage, I'm leaning toward the timneh subspecies) is highly intelligent, and, in theory, are capable of identifying objects, their qualities, and comparisons between them. They are comparatively high maintenance, needing frequent handling (but I would be fine with that), but should be a good next animal in my progression. I promised myself I would not get a dog until I own a house with a backyard, to be fair to the animal ... and though I don't see him frequently anymore, I still have Pharaoh!

African Grey Parrot, 3

Photo by Flickr user Retrolusionary

Challenges to this Grand Plan at the moment? First, the bird and the equipment will start around $1000 from a pet store, and I may want to hunt around for breeders, etc. Then, of course, I'll need to look at how climby Sasha is, so the feasibility of having a bird around a cat in San Diego. I'm hopeful, though ... maybe I'll be able to pull this off within a year.

I'd intended to embed more science and technicality into this post, but it got a bit obscured by parrotly musings. Oh well. Here's something: when I do this, I'll have pets in archosauria, lepidosauria, and carnivora, with periodic rodent interlopers.

Edit: Of course, the auto-Twitter plugin didn't compress the URL of this post first. I think adding the word-wrap property should have fixed the issue, but let me know if the Twitter links (or any others) are spilling out of boundary boxes).

Tuesday Tetrapod: Diplodocus spp.

Posted by tigerhawkvok on June 16, 2009 21:16 in tuesday tetrapod

Today's Tuesday Tetrapod will shake things up a bit. Did I ever say they had to be extant?

Diplodocus_stitch

Diplodocus carnegii from the London Museum of Natural history

I've already talked a bit about sauropods before, but this is beyond a doubt the actual species I have worked on the most. Diplodocids were a group of long-necked saurischians, and include other well-known specimens such as Apatosaurus and Amargasaurus, as well as a few oddballs like Dicraeosaurus. The type species, D. longus was found by OC Marsh in 1878. Approximately 28 m in total length, mass estimates range from around 10 to 12 tonnes, with the torso accounting for as much as 80% of this mass.

The generic name derives from the Greek roots diplos and dokos meaning "double beam", based on the dual cheverons in its vertebrae.

I could spend a lot of time talking about posture, but as I agree with for Taylor et al (2009) for the most part, I'll direct you there, as many of my comments have already been published.

Additional information:

Key references:

Other references available in bibliography of my paper draft.

Warp Drive in the Headlines

Posted by tigerhawkvok on June 15, 2009 15:05 in physics , news , sci-fi

Alcubierre metric

Alcubierre metric. (CC-BY-SA) Allen McC.

Slashdot brings up another resurgence of Warp Drive in the media. While it'd be amazing, it's still at the theoretically interesting stage. Though the theory is good, it requires a lot of energy. While before it required energies similar to that of the universe, now it seems like it will need only about 1045 J. This is in the ballpark of about 5.9 jovian masses. So, better, but still pretty impractical.

The figure at the right pretty cleanly describes the effect. In essense, spacetime is compressed and expanded around the ship so it can "surf" on a wave of expanding spacetime, which itself "moves" faster than c=299792458 m·s-1, but the spaceship itself remains stationary and thus violates no physics. It is, in a fairly literal sense, a warp drive. It is perfectly valid for space to have superluminal expansion rates; distant objects in our Hubble Volume recede from us at apparently faster than light, and the hyperinflationary epoch was defined by an incredible, superluminal spacetime expansion.

The whole thing is based on the Alcubierre metric, described by

Alcubierre metric

Alcubierre metric. Variable definitions as used by Alcubierre available at Wikipedia

In a very technical sense, this is not a solution to the Einstein Field Equations, but rather has ADM forms that can be adapted to various observers that are actually not physically distinguished from each other. However, as a Hamiltonian formulation, the solution is not exactly one to the EFEs, but is much easier to work with and is often used in practical and theoretical studies.

This was probably one of my "denser" posts, so for those of you that understood it, I give you an icon to use:

On Denialism

Posted by tigerhawkvok on June 15, 2009 14:48 in General , anti-science , misc science

Sometimes, I think we were too successful in doing our part to fix certain problems, such as the major elimination of DDT sources and reduction in CFC use. The rebound associated with these, such as the Bald Eagle from the brink of extinction, and reformation of the ozone layer from dangerous levels, really leads us to have the impression we can do whatever we want to the brink of disaster and rebound.

The global fish stocks are a symptom of this mentality. To a lesser extent, climate change is in there, too — though, I feel like the term "global warming" that isn't (i.e., some places will cool, which certainly makes it nonglobal and not warming) provides fodder for denialists.

This is my rebuttal to everyone who wants to look away, or wait: realize that the ecosystem is precisely that, a system. It is finely balanced, and virtually all changes take place on a century pace at the most breakneck. This means that the extirpation of wolves from Yellowstone increased erosion, shrink forests, and decrease water quality [ no wolves -> increased prey items, such as elk -> destroy young trees & feed more by the river, loosening dirt ]. It means that Bufo marinus causes snakes to shrink (DOI: 10.1073/pnas.0406440101) and an increase in Crocodylus porosus populations but a decrease in C. johnstoni populations (DOI: 10.1016/j.biocon.2008.04.031). Three degrees of climate change to the barrier reef could collapse bird and turtle populations.

These are things that affect us, too. We don't live in a vacuum. For example, sensitive phytoplankton provide about half the oxygen generation of the planet. You can argue about hippy-ness, tree-hugging, whatever you want ... but the fact of the matter is, if climate change proponents are wrong, you're just being a bit less wasteful and more efficient if you follow their advice, at the expense of a few dollars and a little time.

If denialists are wrong, and we follow their advice, we have environmental collapse, and in the worst-case scenario, mass extinctions a planet not quite so hospitible to humans. Life, even tetrapod life will do fine; it has adapted to dramatic changes in oxygen content before. We, however, would be in a much worse position.

Think of it this way: it's like Pascal's Wager, except, you know, real.

Gravewalkers

Posted by tigerhawkvok on June 13, 2009 09:50 in bliteotw , zombies

So I'm not sure when it first happened, but well, at least Night of the Living Dead was closest. Imagine if 28 Days Later was right, and you had to fear a disease, or ifResident Evil or Left 4 Dead had it right and some of the dead ... transformed.

I suppose this makes our crazy plans for the Zombie Apocalyse, well, less insane. Google spammed the internet with the news. All of their AdWords bits became info links for what to do with the Walking Dead

Wow, that sounds horribly dramatic.

For right now, Natasha, Rob, Alyssa and I are holed up at my place. We're contemplating the rescue of Boris and Winnie. We see a few zombies walking the street, but we think we can get to the cats if Rob drives, and we do it soon.

Update 1:37 PM: Success at rescuing the kittens. After crashing through two zombies, we claimed a bunch of Natasha's stuff, food, and are back at my place debating zombie strategies. Kit says over IM that higher ground is better ground, an I think that barring someplace up on the hill, Etcheverry would be best. Natasha thinks her place might be a good hideout, and we've yet to reach an agreement. I wonder how feasible hauling computers is.

Update 3:12 PM: OK, I'm glad we didn't do Etcheverry. The streets were getting much fuller very quickly, and people next door were drunk, tried to whack some zombies with bats, and were killed and game back. It was gruesome. It's been a chore keeping the cats apart. The current consensus is try to shove the computers in the car, shove some supplies, the snakes, and the cats, and haul up to LHS. Should be enough food, up near the top of the mountain, and I think we might be able to haul up to LBL if necessary.

Update 5:50 PM: Got to LHS. Many more zombies on the way than we were expecting. Rob's car stalled on the way up, and we had a hard time driving past a pile of zombis up by the stadium. Looks like Kit and Rachael's "diffusion hypothesis" was right. There's a relatively low zombie density up here, and LHS has stashes of food, and not too many exits, but enough. We have a hill on one side ... I think we'll be OK here for a little bit. We have wireless, so we should be able to keep tabs on the internet. More some time later, today has been intense.

Tuesday Tetrapod: Phyrnosoma platyrhinos

Posted by tigerhawkvok on June 09, 2009 23:08 in tuesday tetrapod

Today's Tuesay Tetrapod is another California herp: Phyrnosoma platyrhinos:

< !-- Modified Flickr Code --> IMG_5815

P. platyrhinos, photographed in Death Valley, CA

The desert horned lizard, it is very similar diagnostically to P. coronatum, or the Coast Horned Lizard. It is diagnosed primarily by only one row of well-developed spikes along the sides of its body. Phyrnosomatids include the famous ability to squirt blood from their eyes as a defense mechanism, in addition to the spikes and spines around them.

As far as relationships among squamates, they are iguanians, part of the massive, ill-resolved polytomy that is Iguania. The node Phrynosomatinae (its rank varies) is possibly paraphyletic, including diverse genera from Callisaurus, Uma and Uta, and of course Phyrnosoma.

Sources:

  • Pough et al. 2004. Herpetology, 3rd edition.
  • Stebbins, RC, 2003. Western Reptiles and Amphibians, Third Edition.

Journals and Publishing

Posted by tigerhawkvok on June 08, 2009 13:37 in research

I have some ideas for blog posts on the docket, but I've had a bit of writer's block the past few days. As journals have been high on my mind recently, I thought I'd just link off to SV-POW about "LOCKSS" and choosing a journal to publish in. I'm working with JVP for my paper, and they've been incredibly helpful, and definitely have some prestige that I'm looking for — I wish that they were open access officially, but most importantly to me, I keep copyright on my work. Or, as the case will be — "copyleft".

Tuesday Tetrapod: Ceratotherium simum

Posted by tigerhawkvok on June 02, 2009 18:00 in tuesday tetrapod

Noticing I was a bit lacking in the mammal department, I bring to you the first mammal contestant in Tuesday's Tetrapods: Ceratotherium simum, or the White (or Square-Lipped) Rhinoceros

DSCF5221

C. simum

The generic name is derived from Greek keras meaning "horn" (think "ceratopsian", as in Triceratops), and therion, meaning "beast" (think "theropod", meaning beast-foot). The specific name derives from simus, meaning "flat-nosed", referring to its large square lips, clearly visible in the photo.

Rhinoceros have the interesting position of being one of only three extant perissodactyls (odd-toed ungulates), and being one of the few remaining true megafauna. Perissodactyls were once much more common (and included giants like brontotheres, and the largest land mammal on record, Indricotherium at 5.4 m / 15 tonnes), but have slowly ceded niches to artiodactyls. The perissodactyl foot structure comes from a mesaxonic foot structure, which runs the symmetry and primary weight-bearing of the foot through the third toe, and remaining toes atrophy around that axis, leading to the odd toed hoof.

Perissodactyls are a sister group to (carnivora + pholidota [pangolins]). You can view their phylogeny here.

Sources:

  • Benton 2005. Vertebrate Paleontology
  • Honolulu Zoo (Specimen photographed)

Sauropod Postures, and Low-Slung Diplodocids

Posted by tigerhawkvok on May 31, 2009 17:08 in biomechanics , sauropods , biology , research , paleontology

Recently, Taylor, Wedel, and Naish published a paper on sauropod postures (SV-POW, TetZoo), which challenges a paradigm established by Stevens and Parrish's paper on DinoMorph modeling which states that based on the way the cervical vertebrae articulate together, certain postures are prohibited and thus you get the current model of low-slung necks for the majority of diplodocids. This works out nicely with authors who worry about the blood pressures required to pump blood up to a neck that is elevated so high off the ground. Now, given that only a few posts ago I talked about phylogenetic bracketing and its usefulness, it's appropriate that I talk about the problems in overusing it, and step into dangerously clichéd territory while talking about the paper I am working on.

< !-- Sauropod up image --> Neck held up

First, right off the bat, I want to say that I think this is an excellent piece of work. I think it has a good place in the literature, and that more than studies of giraffe blood pressure is needed to be convincing about the blood supply issues for diplodocids (I am pretty sure I've talked about this before, but if nothing else, let me reiterate that mammals are not necessarily a good model for archosaurs). The crux of Taylor et al's argument is that extant tetrapods from all groups have strongly inclined cervical vertebrae, and that in modern animals, yes, the most favorable position is in fact a horizontal neutral one. However, soft tissues mean that this is actually not the most neutral position, and only using the vertebrae is misleading. Absolutely true, good work, and I'm amazed this hasn't been looked at before. I've even worked with Matt Wedel in writing up my paper (though I'm sure he doesn't recall by now), and I value his opinion.

So, the argument goes, based on phylogenetic bracketing, you would expect sauropod necks to not be held horizontal, regardless of what the cervical vertebrae show. While this might be largely true, I will attempt to briefly, in this blog entry, illustrate why this doesn't have to be true, and give a bit of a preview into my work-in-progress (post-editor revisions) to demonstrate why I don't think this is true for diplodocids (without spoiling my paper. Sadly, something I must take care not to do).

First, it is important to note that phylogenetic bracketing can never tell the whole story. We are the only extant tetrapod that is fully bipedal with an entirely erect vetebral column, and possibly the only one that has yet evolved. No number of examining outgroups will tell you that Homo sapiens bones should be this way; this has to be inferred from our morphology. This is a fact of essentially all novel traits. Just relying on phylogenetic bracketing prohibits you from inferring novel postures based on morphology that have no extant representatives. Second, it's possible that there was something completely bizzarre going on that we just don't know about. As Matt's SV-POW entry very clearly demonstrates, finding the fossil of, say, a budgie 200 MY from now, with no birds, you might guess it has a crazy neck like a flamingo. Sometimes, you just can't tell. That is not to say it is a very good guideline, that is very often right and instrumental in a lot of work; but it is not perfect. They even address this fact:

Can the habitual posture of extant amniotes be expected to apply to sauropods? Phylogenetic bracketing strongly supports this hypothesis as the neck posture described by Vidal et al. (1986) is found in both Aves and Crocodylia, the nearest extant outgroups of Sauropoda, as well as in the increasingly remote outgroups Squamata, Testudines and Lissamphibia.

However, some authors have postulated that the necks of sauropods, rather than representing an extreme development of mechanisms found in other vertebrates, were anomalous structures maintained using novel mechanisms. If this were so, then it would not be surprising if the habitual posture of sauropod necks was different from that of other vertebrates.

Now, it is my personal opinion that Taylor et al. is probably right in the majority of the cases. Among other things, the construction of, say, Brachiosaurus would suggest strongly inclined necks, and I suspect that all sauropods would be able to list their heads like this, at least for moderate periods — it seems the obvious, niche-opening thing to do. Even in diplodocids, it seems that a completely flat neck is not necessarily correct, and I personally favor a slightly cantilevered position (this partially addresses their comments about the orientation of semicircular canals, by coincidence). However, according to their paper:

In all four sauropodomorphs figured by Sereno et al. (2007: fig. 1G), the occipital condyle is directed postero-ventrally when the HSCCs are horizontal. If the HSCCs were inclined upwards, as in most birds and mammals, the down? ward tilt of the occipital condyles would be even greater. Therefore, even if the cranio-cervical joints were held in ONP, the anterior part of the neck would be inclined in all four taxa.If the cranio-cervical joints were flexed as in extant terrestrial amniotes, the anterior portion of the neck would need to be even more steeply inclined in order to hold the HSSC horizontal, and would possibly have approached vertical in Camarasaurus and Diplodocus (Fig. 4B, C). Taylor et al. 2009

< !-- My image --> Suspension Model

My own paper works on estimating the sizes of diplodocids, with biomechanical parameters based on the assumption that they held their necks roughly horizontal, as estimated by Stevens and Parrish's work in line with the accessible ranges in Stevens and Parrish's work. Most accurately, the level of the "bridge" is the same as the level of the acetabulum (thanks to Matt for pointing out the error in this statement). The upshot of this is, when you assume this for diplodocids, you get the correct length popping out of the math. This is very strong evidence, in my opinion, that for at least that clade the neutral position was holding the neck horizontal. This model, in fact, pulls within 4.3% of of current restoration lengths.

Now, I really want to write more — but it probably lives somewhere in that mystical realm where Bad Ideas come from. I'm slowly working on an extensive rewrite of my opening, which does not lead to quick work! But with luck, the pace will pick up soon. I should talk to Matt and see if he is interested in taking a look at what I have so far — and if Darren or Mike is interested, as well. Hopefully I can revisit this in a few months, and talk about it more!

 
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