Wednesday, March 9, 2016

Spinosaurus Unauthorized III: Run, Spino, Run!! & An Anatomical Incongruity

Faster Spino!! Run-Run-Run!! by Duane Nash click image for larger view
I am not completely averse to Spinosaurus bounding around on two legs. You will note I did depict the spinosaurs here as ontogenetically immature and their bipedalism really just a mad dash towards the relative safety of the water as two Rugops have their eyes set on baby spino dinner. Because abelisaurids always seem to roam paleoart as duets - ever notice that? Cenomanian North Africa was not so much a large herbivore based ecology but a fish and fish eater based ecology. And Spinosaurus, especially the juveniles, potentially formed a large part of the prey base for the carcharodontosaurids and abelisaurids that - possibly to some extent - were temporally and environmentally coincident.

As the close-up here attests I put the little spino in a semi-contorted posture with the head and torso pulled back to bring the center of gravity closer to the hips. With each forward lunge the body is in danger of toppling forward as the larger individual in the mid-foreground is getting perilously close to doing so. But by pulling the torso and head back with each footfall at a rapid clip I can picture this locomotion working for the youngins. To help with balance the arms are splayed laterally like a tight-rope walkers balance pole.

I still maintain belly sliding takes care of that pesky center of gravity question and also allows them to negotiate the muddy/intertidal terrain they lived in. But the bipedal heritage of Spinosaurus can not be denied and I find it very probable that - like young/small crocodiles today - smaller spinos had much more liberty in terms of locomotory options on land than the more ponderous, gargantuan adults.

To take you into my minds' eye I think that they would somewhat resemble the quick bipedal sprint of basilisks (Jesus Christ lizards) and frilled lizards.

However some, or even many, of you reading this are not convinced of Ibrahim et al's proportions for Spinosaurus nor are you convinced that a novel adaptation such as some form of quadrupedalism or as I proposed belly sliding need be invoked for this animal(s). Consensus has been agnostic or equicocal concerning Ibrahim et al's proportions for Spinosaurus. Which leaves us in a funny place because renderings and depictions of Spinosaurus continue to come about and for the most part the professional paleoartists have gone into a sort of compromised position of depicting Spinosaurus having somewhat shorter legs than other theropods but still being a good ol' biped. The recent artwork depictions of Spinosaurus by Julius Csotonyi , Mark Witton, and Sergey Krasovsky all hedge their bets towards a longer in body, shorter legged, but still fundamentally bipedal Spinosaurus. I call this compromised sort of depiction of Spinosaurus the true "chimera" in all of this for reasons I will elaborate later.

To what extent was Spinosaurus bipedal? Most would say "we need more data", I say we have enough already to dismiss Spinosaurus as a less than ideal biped on land.  An anatomical incongruity has been rather summarily dismissed or just glossed over in discussions which I will highlight later. 

To me everything circles back to one fundamental question we should ask when settling on the interpretation of an animal: does this animal make sense as an evolutionarily successful animal in it's environment? Can it, in a reasonable manner do things like forage, move, mate, evade predators and in general get along in none too friendly environment full of obstacles, competitors, and predators? This notion that some animals from the fossil records are "in the process of adapting" or "an unfinished product" is bogus to me. Not only does such a sentiment smack of neo-Lamarckism but it also begs the question: where are all the unfinished products in today's biota? Is a mudskipper a less than perfect transitional species on its way to becoming terrestrial? No it's an animal doing just fine in the environment it lives in. Are gliding animals inferior to flying ones or are they better viewed as just good enough for where and how they live?

The jack of all trades, master of none interpretation of Spinosaurus as mixed forger of land and water is not congruent with the wealth of anatomical attributes pointing towards a primarily aquatic existence. The reluctance to give up obligate or classical theropodian terrestrial bipedalism - as evinced by the artistic depictions I mentioned earlier - is at odds with Spinosaurus' peculiar pelvic anatomy. There is a layer of evidence - sitting in plain sight as is so often the case - that speaks against "classic" theropod bipedalism. This anatomical incongruous - especially when viewed in light of the animal's likely habitat of complex, intertidal estuarine fluvial systems - essentially creates a vanishingly small window of opportunity for the bipedal loyalists to maintain Spinosaurus as just another good ol' bipedal theropod. 

You may or may not recall that paleo-super hunk and Papa John spokesman Paul Sereno starred in a very well done promotional video that coincided with the infamous Spinosaurus Science publication. In this video Paul offers some really great and captivating sound bites and a little background on this most fabled of dinosaurs. For our purposes here he makes special emphasis on the femur of FSAC-KK-11888:

On lacking a marrow cavity: "It didn't have a marrow cavity. We had never seen this in any predatory dinosaur. they all have good marrow cavities. And that resembles animals that are actually spending a lot of time in the water. They want to be a little heavier than the water so they don't float all the time and they can control their swimming movements."

On the proportion of the thigh bone (femur) vs shin bone (tibia): "This thigh bone is shorter than the shinbone by several inches.... In animals that are sitting on top of the water and using their limb to paddle that thigh bone becomes short and stocky."

On the caudemofemoralis attachment "On that thigh bone we noticed that the attachment for the muscle that moves it back is huge. So what were looking at is an animal that has adapted it's hindlimb largely for paddling in water."

A couple of things here. While it's old hat that Spinosaurus lacked a marrow cavity I want to point out an inconsistency in Paul's thinking. In one instance he asserts that such animal's want to be a "little heavier than the water so that they don't float all the time" and to "control their swimming movements"This makes sense and I mostly agree with what he is saying here. But then later on Paul - when talking about the use of the hind limb and it's expanded musculature to paddle through the water contradicts himself saying, "In animals that are sitting on top of the water and using their limb to paddle that thigh bone becomes short and stocky".

Did you catch that? We can't have it both ways - Spinosaurus is either a floater or sinker. It's either heavier than the water (a sinker) or lighter than the water (a floater). In order for Spinosaurus to be a floating paddler like a duck or seagull we would not expect such dense bones. Spinosaurus is therefore - as I have been arguing for a while now - a sinker and when dense bones are combined with a dense dermis, which is not unparalleled,  it is more tenable to interpret Spinosaurus as an animal that sinks right down to the bottom. Which is where the true nature of Spinosaurus' unique and powerful pelvic anatomy come to fruition as an underwater walker.

Before I go into how and why Spinosaurus was such a superbly and beautifully adapted underwater walker one final nail in the coffin of this notion of Spinosaurus as floating paddler. Surface area. One of the most important concepts in paleo - functional analysis is the square-cube law.  As an animal increases in size the volume (read bulk) increases at a much higher rate than the surface area. Therefore a structure that is dependent on surface area to do it's job efficiently - such as a paddle - must hold pat and increase at a concurrent rate as size increases. In other words a 5 ton duck should have relatively larger paddles than a 2 lb duck. Like crazy huge paddles. Spinosaurs is a big, heavy and long animal. Even the most rudimentary, intuitive spitball analysis looking at it's paddling arsenal shows that it does not really have the type and spread of foot paddle needed to even move at the relative speed of a duck on the top of the water - much less the type of speed needed for a predator that, you know, had to go out and catch stuff. Just check out the huge rear foot paddles on a true rear foot paddler in the beaver pictured below.

 Beaver on bank lower Kern River. credit Ryanx7. CC3.0

Within the same line of reasoning it is easy to dismiss Spinosaurus, indeed all spinosaurids really, as wading, stalking heron type predators - they just did not have the foot spread to support such a lifestyle. Indeed when you extrapolate the amount of spread in heron feet - which often weigh just one or two kilograms - and assume the same level of spread in giant bipeds of several metric tons - you come up with an improbable amount of foot spread needed to achieve a wading/soft substrate stalking lifestyle. Now I am not saying that in the history of spinosaurid existence a spinosaurid never waded out and caught a fish like a heron does - just that these animals make more sense placed in the water with the fish rather than stalking and catching them from above heron style. Not to mention the lack of binocular vision, relatively straight neck, and tactical face suggesting immersion in the water.

For argument's sake let us dispense the center of gravity work, all those bits and pieces that probably belong to Sigillmassasaurus, and just look at FSAC-KK-11888 as a single entity - which it most certainly was as there is no duplication of material and the bones are ontogenetically congruent (i.e. come from an animal of same age). What we have in FSAC-KK-11888 is a simple case of deduction. If we can exclude rear paddle swimming on the grounds that the foot lacks adequate surface area, then we are left with Spinosaurus being either a powerful biped underwater or on land as indicated by the robust muscular attachment so noted by Sereno & Ibrahim et al. It was using that powerful leg for something after all. 

Now recall Paul Sereno's emphasis on the grossly enlarged muscular attachment on the femur for the caudemofemoralis - the muscle that pulled the leg back and which he assumed was pivotal in the paddling stroke. As I alluded to earlier there is an anatomical incongruous - two things that do not fit together - that stood out to me from Ibrahim et al., an observation that was plainly laid out for everyone to see but which, again, is seemingly glossed over in just about every online discussion both professional and lay regarding FSAC-KK-11888.

From Ibrahim et al.:

"The pelvic girdle and hind limb are considerably reduced in Spinosaurus. The surface area of the iliac blade is approximately one-half that in most theropods, and the supracetabular crest that supports the hind limb is low."

This is a crucial point that the bipedal loyalists have seemingly glossed over. The musculature and skeletal framework that are exactly crucial for standing bipedally (on terra firma) are diminished in Spinosaurus. Not only are the legs proportionately smaller in FSAC-KK-11888 (the proposed neotype) but the legs are relatively diminished in their capacity to support and maintain bipedality.

From Ibrahim et al.:

"The femur in Spinosaurus has an unusually robust attachment for the caudofemoral musculature, which is anchored along nearly one-third of the femoral shaft, suggesting powerful posterior flexion of the hind limb. The articulation at the knee joint for vertical limb support, in contrast, is reduced. The distal condyles of the femur are narrow, and the cnemial crest of the tibia is only moderately expanded."

What we have here in FSAC-KK-11888 is an incongruity that needs explaining. On one hand the femur and musculature attached give us a signal for massive power in the horizontal plane. Discordant with this observation is the relatively weak and diminished musculature and skeletal structure for the vertical plane that would be needed to support a biped of this size. How to explain this seeming contradiction?

Let's revisit my contention earlier than an animal should work reasonably well in its environment. If we put Spinosaurus in the large, complex mangrove/deltaic/intertidal habitat that is most likely for it and infer bipedalism we should expect the opposite pattern of limb development. That is, far from being diminished in size, the skeletal and muscular framework for bipedalism should be hypertrophied (larger & stronger). The reason is that pushing yourself through water, mud, thick sand, tangles of mangrove vegetation as a biped is hard work. So if Spinosaurus was indeed doing this as an obligate biped we should see greatly expanded musculature for bipedalism in terms of vertical support, which we don't.  I cite the remarkable robusticity and upper muscular development for the swamp lions of Botswana's Okavango delta. These impressive lions - the females of which are as big as male lions elsewhere - have expanded chest and shoulder musculature that assist in not only their main prey - Cape buffalo - but also in swimming, wading, and pushing through their swampy, flooded habitat. There is even some suggestion of a separate subspecies emerging.

So using simple deduction if we can eliminate paddling as a way to explain Spinosaurus' pelvic anatomy on the grounds that it simply did not have too great of a surface area for foot paddling and if we can eliminate terrestrial walking/wading on the grounds that the exact structures needed for such an adaptation are diminished in Spinosaurus - the exact opposite of what should occur in such a large biped in a swamp - then we are left with underwater walking or "punting".

Underwater walking is consistent with the dense bones, diminished size of pelvic area, and greatly expanded caudemofemoral attachment. Neither obligate bipedalism nor paddling addresses the unique and seemingly incongruous features in Spinosaurus. Furthermore the lack of vertical support at the knee joint as noted in the Ibrahim's et al. paper speaks against both bipedalism and quadrupedalism and is another line of evidence in support of belly sliding. Even if Spinosaurus were to have evolved some form of quadrupedalism there is no reason for such an adaptation to cause a decrease in the ability of the hindlimbs to hold weight.

Finally those puny legs - a seeming weakness - are actually superior to long legs for an underwater walker. In one of the few research papers that actually attempted to quantify and bring some discourse to the manner in which hippo run underwater it was found that short, quick steps or "punts" actually outpace the longer "gliding" paces in speed when measured in controlled observations of hippos walking underwater.

Comparing hippo locomotion underwater to humans moving in a "microgravity" environment (i.e. outer space) Coughlin & Fish wrote in their abstract:

"Ground contact time decreased with increasing horizontal velocity,"

Which translates to as the hippo moved faster underwater the amount of time that the foot hit the ground decreased.

"vertical displacement during the unsupported intervals increased with an increase in ground contact time,"

"vertical displacement" refers to how high the hippo rises off the bottom of the tank in their observations. Since longer ground contact time is associated with slower relative speed when the hippo is moving relatively slowly its foot contacts the ground longer and it rises higher in the water column (i.e. gliding phases).

"and time between consecutive footfalls decreased with an increase in horizontal velocity."

which is pretty straightforward - as the hippo increased in velocity footfalls became more frequent (but still relatively short in duration).

Spinosaurus likely had the same pattern of locomotion underwater. Slow speeds with increased foot contact time and longer gliding phases (how beautiful to imagine btw). Higher speeds had decreased foot contact time and shorter unsupported intervals. Some might poo-poo this line of reasoning "you can't compare a bipedal dinosaur to a quadrupedal mammal blah, blah" but much recent work has highlighted congruity in all forms of tetrapod locomotion - especially remarkable convergence in aquatic locomotion in tetrapods. Furthermore you can test it out yourself as a biped. Go to a pool or body of water up to your chest and run. You will quickly see that short, quick steps with little gliding phase outpaces longer paces with lengthier gliding phases. As the authors note in the paper: "Under conditions of microgravity, humans switch from a walk to a run at slower speeds. (Kram et al, 1997)"

And don't for a second dismiss underwater walking or "punting" as a less efficient or even speedy way of moving through water than swimming. Check out the speed and alacrity in which the hippos in this  clip move. Although you can not see them as the people are in a boat - you can surmise from the wake and relative speed of the boat that the animals are moving along underwater at quite a pace.

The short and powerful legs of Spinosaurus are therefore beneficial to walking underwater at speed since short and quick paces outperform long paces for underwater walking.

In the discussion from the hippo/microgravity paper the authors also highlight the importance of the animal in question being denser than the water,

"Effective bottom walking requires a body that is denser than water when submerged."

As I argued in my first post in this series on Spino there is reason to make Spinosaurus denser than the water via dense bones and an extensive and dense epidermis not without parrallel to manatees, hippos, and possibly tapirs.

update new art!! used w/permission credit Robin Liesens deviantartits Dontknowwhattodraw

When we put Spinosaurus in it's proper environmental context which is completely underwater - not some bastardized giant heron nor an improbable jack of all trades switch-hitter of surf and turf - now a real functional use for the sail emerges. As I discussed in my last post the sail would not sit above water anyways as the display marker so many have championed, nor would it add any sort of propulsive power either. But what it would do, I suggest, is act as stabilizer - a dorsal keel - that helped prevent Spinosaurus from rolling when twisting and turning underwater. As much as I have championed the hippo as a useful model for Spinosaurus underwater movement, they differ in one fundamental aspect. Hippos do not have to move with much agility underwater because their primary food - grass - does not grow there nor would it swim away from them if it did. Spinosaurus as an underwater hunter of aquatic prey that did not want to get caught - needs relatively more agility underwater than a hippo. Additionally, because Spinosaurus moves as an underwater bipedal walker not a quadruped, if Spinosaurus changes course rapidly underwater and it's body starts rolling it has no way to correct itself with forelimbs (like a hippo). Now caught in an underwater body roll a Spinosaurus' hind limbs would lose contact with the substrate and it would lose it's main propulsive power since pushing off the substrate is required in underwater punting. A sail helps with this dilemma so that as Spinosaurus twists and turns underwater to either sides the sail pushes back against the water and helps prevent rolling.

Ha, ha I made Spino almost comically "fat" but really no more ponderous that a hippo. You will note that I actually depicted another, more subtle, use for the sail in the top pic. That due to it's swayback morophology the sail may have hydro dynamically made movement underwater more efficient. As the animal moves from right to left, as shown by the large arrow - water flows up and over the sail but forms little micro-eddies over each rise and fall of the sail. The effect is that a slipstream develops that allows Spinosaurus to recoup some of the energy dispensed moving through the water. If you think about the way competitive bicyclists use slipstreams or even the "shake and bake" tactic used in competitive race car events this is not far from what I am suggesting. In the biological realm birds flying in formation or even migrating lobsters moving in line take advantage of the energy saving features of slipstreams. Spinosaurus may have done the same with it's sail underwater in addition to it's movement stabilizing attributes and not altogether dismissing possible uses for bluff/intimidation/social signalling, thermodynamics, prey corral, buoyancy control, and mineral storage.

Oh yeah I almost forgot. What animal also has big flat unguals and partially webbed toes? Take a wild guess...

Ibrahim et al 2014

Also it is worth repeating how "barrel chested" Spinosaurus really is. This is an important point and another nick against trying to retrieve any meaningful terrestrial bipedality. The front of this animal was heavy. Furthermore it compares very well with the skeletal framework of - you guessed it - a hippo. Drape on some muscle, meat, and a thick skin and you will have a very voluptuous - and long - animal. The likes of which is going to be very maladapted for bipedal movement on land and even worse off trying to walk through thick tidal muds, sands, and tangles of swamp vegetation.

link Youtube Hippo 3d skeleton

In the water it was a superbly adapted underwater bipedal walker or "punter" - very graceful, powerful and daunting in that environment. On land, not so much. Smaller juveniles could have enjoyed more liberty in moving around terrestrially, perhaps even going into quick bipedal sprints. As I have maintained since before the actual publication of the Ibrahim material it was a belly sliding mud surfer, looking like an amalgamation of a giant saltwater croc, a penguin, and a loon.  But that was ok for what it had to do in life. It conceded terrestrial ability for aquatic proficiency. And that is not radical or revolutionary or even unique - every tetrapod lineage that transitions back into the aquatic realm concedes some or even all amount of terrestrial capability. Otters, beavers, crocodiles, pinnipeds, loons, penguins they all can move around on land but are much less proficient on land than their related terrestrial brethren.

CC 2.0 credit Mike Bowler. Spinosaurus & Onchoprostis

Well for now that about does it for all I want to say on Spinosaurus (although things always change). I am quite confident that my take on Spinosaurus - a belly sliding, underwater punting, primarily aquatic/piscivorous beast of tidal waterways - will prove to have much truthiness to it.

And in closing I leave you with a depiction of an adult Spinosaurus closing off a tidal outlet and using it's length, size and sail to corral aquatic animals trying to exit with the outgoing tide. The experienced adult has enmeshed itself between two thickets of the mangrove fern Weishchelia reticulata and completely dammed off the outflow channel from a tidal mudflat that fish came up through to feed during high tide. Contrary to the vast majority of Spinosaurus/ Kem-Kem paleoart which feature towering cypress canopy relatively low and shrubby cheirolepidiacean conifers and Weischelia should dominate the flora. Some of the fish - Lepidotes - even swim out of the water to escape the hungry maw of the Spinosaurus while other fish such as the sawshark and various sarcopterygians attempt to vault over the striking theropod to get to the deeper safer water on the other side. I would suggest that this form of fishing - not too dissimilar to what modern crocs do - would be a very efficient and likely manner of fishing for Spinosaurus especially amongst the older, larger, and more experienced Spinos that knew how to take advantage of such tidal choke points. A chunk has also been taken out of the Spino's sail. Also take note of the pterosaurs and dromaeosaurids attracted to the commotion and easy feed provided by the spino.

Tidal Harbinger Negative Brown by Duane Nash click image for larger view
Tidal Harbinger Shocked Pink by Duane Nash click image for larger view

I have actually amassed quite a lot of posts on Spinosaurus going back nearly to the start of this blog. Going back and reading these may be of interest to see the evolution of my ideas - including ideas I have since abandoned.

Spinosaurus Unauthorized II: Spino Identity Crisis & Island Hopping Hippos from November 2, 2015 in which I go into Sigillmassasaurus and what this animal means and does not mean for the "new" Spinosaurus and highlight a pivotal point generally overlooked in discussion of the veracity of FSAC-KK-11888. More on hippos and what island hopping hippos tell us and don't tell us about swimming ability and lack there of.

Spinosaurus Unauthorized I: Hippos Are Not Really Fat and Can't Swim from October 12, 2015. I return to the spino debacle and begin building my case that Spinosaurus works most effectively as an underwater walker/punter. In order to do so I have to spend a lot of time on hippos and a whole lot of effort arguing that hippos can not actually swim. I also argue that Spinosaurus sported a very thick and heavy dermis that assisted as ballast control along with the thick bones similar to manatees, hippos, tapirs, and walrus.

Time For the Giant Heron Spinosaurid Analogy to Bite the Dust Part 2: Getting More Than Just Your Feet Wet from November 7, 2014 in which I elaborate on why the heron/spinosaur comparison is very much less than ideal and not at all the best of all candidate analogs. Also why depictions of spinosaurids  standing on the edge of riverbanks hoping for big fist to blunder on by is patently ridiculous.

Time For the Giant Heron Spinosaurid Analogy to Bite the Dust Part I from November 2, 2014. In which Thomas Holtz says I make a straw man argument.

"Last Man Standing... el Ultimo Hombre": As the Dust Settles on the Spinosaurus Bombshell from September 14, 2014. Well the dust is still settling and well, sometimes you have to push the issue to get people to take notice.

Adding Some Context to the Middle Eastern Attack Today. from September 11, 2014. Do you see what I did there? Very meta.

Surf OR Turf: Can a Terrestrial/Aquatic Switch Hitter Really Exist? from August 31, 2014. Skeptical of the notion that Spinosaurus ala JP3 could function equally proficiently in the water or land.

Did Bakker Get Spinosaurus Right After All? from August 16, 2014 in which - upon seeing the leaked Nat Geo photos of the new Spino reconstruction - first mused that Bakker got Spinosaurus right in the animal being very aquatic and where I first argue the belly sliding hypothesis. I am now equivocal on how much the forelimbs - if at all - assisted in belly sliding or a "combat crawl" type of movement or some combination there of. In either case the post is one of my most popular and still gets lots of links and hits never mind the fact that I feel how Spino moved terrestrially is among the least interesting aspects of the animal.

Planet Predator II: Kem Kem from September 7, 2012 in which I muse on the ecology of the Kem Kem & Cenomanian North Africa and Spinosaurus' place in the ecosystem as prey, competitor, and provider of fish dinners for other kleptoparasitic theropods.


Coughlin, Brittany & Frank, E.  Hippopotamus underwater locomotion: reduced gravity movements for a massive mammal. (2009) Journal of Mammalogy 90(3) 675-679

N. Ibrahim, P. Sereno, C. Dal Sasso, S. Maganuco, M. Fabbri, D.M. Martill, S. Zouhri, N. Myhrvold, D.A. Iurino (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science 26 September 11, 2014

"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine

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Elijah Shandseight said...

Excellent article, Duane.
The model you're proposing for Spinosaurs is coherent with the data we've got and it is absolutely fascinating how the much-discussed 2014 restoration is far from being absurd. Together with some other considerations (like the biomechanical features and implications suggested by Andrea Cau), this and the other posts you've written give us a look not of a bunch of bones, but that of a living and breathing animal.
Really well done

Ps: don't know why, but instead of thinking about running lizards, your young spinos reminded me of the running Allosaurus model in Carrier et al.

Bk Jeong said...

Has anyone considered the possibility of integument on the arms being used as paddles for steering, or webbing between the claws?

Duane Nash said...

@ Elijah Shandseight Thanks and I had never come across that pose for a running Allosaurusus - interesting. Now that I think about it I do remember some doc suggesting that in order to better make turns Tyrannosaurus would pull it's head head and tail up together.

@ Bk Jeong not that I know of - although to my knowledge we do not have a complete and undisputed Spinosaurus forelimb.

Fred Spiers said...

Whilst there's some logic to it, that raised up Allosaurus pose looks so much like the terribly old and inaccurate restorations I can't help but be amused!

Nicely put together article, you certainly have me convinced. It would be really interesting to look at Baryonyx and Suchomimus (popularly anyway, are there others?) as more primitive forms, but as you said, still well adapted to their current situation (whatever that would have been). Suchomimus seems to have a rudimentary 'sail' of sorts compared to the earlier Baryonyx. I wonder if it shows any other 'mid-way' adaptations between Baryonyx and Spinosaurus?

On the note of animals sacrificing terrestrial capability for aquatic capability, I think varanids are especially interesting as the more aquatically inclined species do not appear to differ much outwardly from more exclusively terrestrial cousins, yet are pretty proficient underwater, even able to hunt fish. Their long body shape, as crocodilians, also hearkens back to Spinosaurus itself. I'd like to note the keeled aspect of the tail that is not shown in the skeleton of those species, and with its long tail it seems not unreasonable to expect Spinosaurus to share a similar feature. I can't think of any long tailed aquatic animals where it is not keeled in some form (except the Eurasian otter, unlike most other otters; what's up with that??).

Bk Jeong said...

I just came up with this bizarre idea (combination of SpinoGate & Grand Guginol Theropoda plus a hint of the Plesiosaur Machinations)

Spinosaurus being far more formidable than often assumed (because piscivore =/= obligate piscivore =/= small prey), is it safe to assume the front-heavy build is to assist in underwater grappling of sharks/crocodiles/sawfish/Mawsonia? Basically, the animal would wrestle its prey into submission with its arms, get a grip with its stout conical teeth, then vertically move its head up and down to flay it. At the same time, the sail would provide a fulcrum in heavy currents and ensure that the spinosaur stays in one place as its victim is tossed around.

Duane Nash said...

@Bk Jeong Good point, Also - and it is worth repeating - the fish fauna of Cenomanian North Africa were not pushovers. Yeah I have thought about how Spinos would handle largish prey as they could not use death rolls due to their sail and their tooth serrations were reduced. Some combination of securing prey with the gaff like hand claws and up & down and/or side to side head shaking is a good hypothesis. That being said full on swallowing of pretty large stuff should not be discounted. I am consistently surprised by the size of food items modern predators gulp down and what I think of as overly conservative estimates for extinct animal swallowing capability. Remember that croc trying to gulp down a whole baby hippo that I linked to on a past plesiosaur machination? Crocs have no "give" in their jaws - Spinosaurus at least had some.

One thing I have also thought about is turtle consumption. Would they have swallowed 'em whole or maybe with those hand claws pried them apart?

The Eurypterid said...

Oh man that fat spino with the coel is hilarious. "I'mma gonna getcha... I'mma gonna getcha... Mueheheheh!"

Kudos on more science being done. If it wasn't rude I'd totally invade the rest of the paleoblogosphere comment sections with hippo spino. And burrow masaikasaurus. And SIGILs. And...

Bk Jeong said...

Yeah but I doubt even the biggest Spino could fit a 3 ton Oncopristis or Mawsonia in its mouth.

What I consider to be something important when Spino took on such huge fish are the brow ridges. Much like how the ridges helped carnosaurs during vertical and back-and-forth sawing motions, they would provide structural integrity when a spinosaur repeatedly tossed prey animals into the air or against the surface.

Turtles? Has anyone checked if spinozaur forlimbs could pry the carapace open?

Bk Jeong said...

Also, the real formidable prowess of spinousaurs needs to appear on these posts all the time (basically, do the same you did for iPhone theropods and elasmosaurs) to shut up the fanboys.

babehunter1324 said...

Excellent article. You're theory really has a lot of ground, I guess it will only be a matter of time until somebody publishes a paper that comes to a similar conclussion.

Jonathan Atkinson said...

Duane what is you source for spinosaurus/spinosaurs lacking binocular vision as i remember them having distinctively good bino vision. Other wards great article and i just finished your plesiosaur list, truly eye opening.

Anonymous said...

Hi Duane!

I definitely agree with your theories on Spinosaurus having an aquatic lifestyle more like a hippo than a duck or other surface paddler- those reconstructions never made sense to me, because of just how small its feet and hindlimbs are! Nor do the reconstructions of Spinosaurus being a quadrupedal walker or even a bipedal one make sense. I think the "belly crawl" is the only way that Spinosaurus would have been able to move on land.

Your drawings of Spinosaurus are really great, too. I like the dromaeosaurid that is sliding down its sail ala Raptor Red!

However, I do take issue with the way that the Spinosaurus juveniles are shown running. The Carrier et al method of running has since been disproven, it seems.

Here are the pertinent snippets, from "The Carnivorous Dinosaurs" by Kenneth Carpenter, courtesy of Google Books (I decided to just take screenshots, but the link itself is easily found): The inaccurate version of the running theropod. The more accurate version. Explanation 1. Explanation 2. Explanation 3.

Keep up with the interesting blog posts!

-L. Walters

Duane Nash said...

@Jonathan Atkinson Personal communication with Thomas Holtz - binocular vision like other carnosaurs not as high as tyrannosaurids or herons for that matter.

@L. Walters you know I kind of remember hearing about theropod limitations of running in that fashion. But what if the hips are kept fairly horizontal as I depicted in my picture and it is the the tail and torso that bends? In the Carrier pic it looks like the hips are tilting upward which is the problem while I kept mine in a horizontal posture just with extreme tilting of the torso & tail.

khalil beiting said...

Hey Duane! I have some questions on the matter of Spinosaurus locomotion:
1. Is knuckle walking even possible? The hands, wrists and arms aren't adapted to knuckle walking or any other form of quadrupedality, and they are also highly pneumatisized like all other Theropods. This means that it couldn't support it's weight on it's arms/wrists/hands. So is it even possible?

2. Is bipedality even possible? It's legs are so short and it has such a forward center of balance that it looks as though it would just fall over. Even with it's neck in a pelican like position and with it's tail on the ground, it would just have a hard time moving. Although I have recently gotten into a conversation about Spinosaurus' bipedality, and it turns out that the hips, legs and tail are dense. The tail would also be incredibly heavy since it would be covered in muscles. And the chest, neck and head are also highly pneumatisized and relaitvely light. With this in mind, we get from a top heavy knuckle walker to a bipedal, pelican like walker. Isn't this more likely for locomotion on land than knuckle walking? I assume mud crawling would be better for terrestrial locomotion in it's natural habitat since it lived in a tidal swamp full of mud, but when moving on firm ground, how would they get around? Knucklke walking or bipedalism/

3. What skeletal is more accurate out of all of these?:
This on by Get Away Tike:
The original Ibrahim et al:
Or this one who's name I forgot:
Which one is accurate?

Duane Nash said...

1. We don't have a complete arm/wrist/hand that is >unquestionable< spino material. Some of the stuff Ibrahim et al. attributed to Spino in terms of arm material might be Sigillmassasaurus. So while some unique and strange quadrupedal adaptation in Spinosaurus is a possibility I personally think it is an extremely remote possibility. Furthermore there would be no strong selective pressure for it to go through that evolutionary path and - as I mentioned in this post - the pelvic anatomy that holds Spinosaurus upright is diminished. Flowing from that observation I don't see why that diminished pelvic support would occur in a biped OR a quadruped. Even if it was quadrupedal why would it lose vertical support strength in the hindlimb and at the same time grossly increase the femoral attachment for the caudemofemoralis? This is an important incongruity that needs explaining. The long and short of it is that bipedal or quadrupedal movement on terra firma was not important for Spinosaurus and really should not be too important to us.

Always remember North Africa was like one huge continental sized tidal/deltaic/swamp that interfingered more inland/terrestrial habits. Spinosaurids are always associated with the aquatic type habits and really could live out there whole life only coming onto land to relax a bit and lay eggs. No need for a strong terrestrial component in their habitat/lifestyle.

2. I can only speak for myself here as I feel many researchers/scientists/professionals have taken a vow of agnosticism "let's wait and see" approach. But what I argued in this post is that if we just look at FSAK-11188 as a discrete entity - and cut out all the other noise from associated material that may or may not belong to the same species - there is enough there from that one specimen to signal it not being a classic biped. I have heard all the arguments that are like "wait the tail is SOOO heavy and the front end is SOOO light" but is it? So far these are just random claims chiming forth but no real study behind s assertions. I can just as easily say the front was WAY heavy and assert that it had a barrel chest not a slab chest, a long neck, 2 meter tall sail of solid bone, and heavy robust forequarters. If anything I would argue that relative to other theropods Spinos is more front heavy. Again all those bones - including the sail itself - were solid.

3. The Ibrahim one and the third one you listed are actually the two skeletals independently arrived at from the study. That is an Italian team came up with the third one which matched the more widely known Ibrahim one. They both converged on pretty much the same morphology - which may yet again change with future and better material/studies.

khalil beiting said...

1./2. Thanks for the help Duane. So at the end of the day, Spinosaurus was just a mud crawler? It does make sense of course since it lived in such a swampy area and would have spent most of it's time in the water regardless. So what would this mud crawling look like exactly? I'm still having some trouble imagining it. Not because I doubt it, but rather that I can't really imagine it that well.

3. So with our current knowledge, is the skeletal from Ibrahim et al accurate?

Duane Nash said...

Will see a more up to date skeletal whenever they put out their monograph.

Hopefully someone animates Spinosaurus doing a belly slide some day!! Maybe I can hope... Go watch videos of penguins belly sliding, crocs belly sliding across thick mangrove muds, and loons and imagine a composite of all these.

Robert Haan said...

A bit late to the fray i admit, but yet another great article again Duane, i really like the proposition you brought up that the sail /ridge would have aided the Spino in maintaining stability in the water , there was a study which came out a few months back which came to a similiar conclusion by comparing the sail of Spinosaurus with those of Sailfishes, all in all a much more plausible and satisfactory explanation for the existence of the structure as opposed to "it was just for display".

Anyway this is a very satisfying conclusion to the whole Spinogate saga (well at least until the next great discovery , but i think alot of your points will still stand.) i have to admit i was one of those on board the fully bipedal Spino camp, but after seeing what it eventually turned out to be, Spino has become a much more fascinating, unique and dare i say "badass beast" , it wasn't competing with the other giant theropods for a place at the table, rather it thrived in its own niche , exploiting its environment with the uttermost efficiency , in a sense it was in a league of its own altogether, this way surpasses any Spinozilla Hollywood can come up with.

Oh and on a final note, was it really stated that the forelimbs and most of the front portion of Spinosaurus was heavily pneumatized ? as far as i know, Ibrahim and co have stated that the spines and ribs were dense and the ribs themselves were tightly curved and resulted in a relatively barrel shaped torso, Sereno himself stated that "Spinosaurus was incredibly front heavy)

Duane Nash said...

Thanks. Regarding the front half of the animal being "light" or pneumatized: there was chatter that bipedalism could be retrieved because of the front half of theropods being full of air sacs. I don't think this argument has much merit though due to barrel chest, large sail, heavy arms, long and heavy neck/head all adding a lot of weight to the anterior. And no I have not heard of any spino remains being pneumatic, even the bones in the sail are quite dense.

Heteromeles said...

Late to the party, but I'd like to note something weird: even the oldest modern "mangrove" (the Nypa palm) has fossils going back around 70 to maybe 90 mya.

What did those earlier Cretaceous "mangrove forests" look like? The only place I can find them referenced is as habitat for sauropods and spinosaurus. My uninformed and suspicious guess is that it's being used as an incorrect shorthand for something else, or at best, some sort of coniferous saline swampland that is, at best, a poor analog for more modern mangrove forests.

Anonymous said...

Hey Duan, excellent article on this animal, seems totally believable. While I'm here, I would like to post a suggestion for your next article. It somewhat like your pleisosaur machinations, except this time with Ceratosaurus. After all, Ceratosaurus is a cool looking theropod that basically looks like a dragon, but it seems that no one is paying attention to this theropod, because ever pop culture depiction of this animal I come across shows it being taken down by an Allosaurus (Jurassic Fight Club, When Dinosaurs Roamed America,etc.). I would like you to do a post where you redeem Ceratosaurus as this amazing animal that can hold his own with even the formidable of foes, just like how you did with pleisosaurs. I hope you will consider such an article in the future.

Anonymous said...

P.S I am the same person who proposed a that all theropods had "roof teeth" and serrated tongues, and that most marine reptiles had Leatherback mouths

Anonymous said...

Wait!! I almost forgot, what are your thoughts on the new titanosaur that is suggested to be the largest land animal of all time. The researchers say that the giant was actually a sub adult, meaning it was still growing, but it was already 10% larger than Argentinosaurs, and I was wondering if you could do another article that talks about how big they it can get. Also what are your thoughts on the size of Amphicoelias. Personally, I find it highly unlikely that it grew to 200 feet long and weighed in at 120 tons, and I would think that it would "only" be around 100-115 feet long and around 70-75 tons in weight, one of the largest, but the largest land animal. Another thing, would Majungasauruhs have quills, knobs, flaps, and wrinkled skin that you suggested in your face bitting theropods.

Anonymous said...

Forgive me if I am asking too many questions. I'm just a curious, almost 13 year old, mesozoic animal nerd. I here all of my friends saying that I know more about dinosaurs than most paleontologists, but I don't think so, and after reading about your posts, it seems that I was correct, and again, forgive me if you I am asking too many questions.

Duane Nash said...

@Anonymous (please give yourself a name btw)

Don't take my depictions of theropods too literally. All depictions of prehistoric animals to greater or lesser extents are hypotheses. Exceptions of course stuff like Yutyrannus, preserved wooly mammoths etc etc. Majungasaurus probably did have a face that closely resembled its skull though.

Yes Ceratosaurus is cool, I don't have anything planned on him and I have a policy of not taking requests for posts as I always write about what is interesting to ME at the moment to make things as passionate and interesting at the time. It is this little snobby integrity think I abide by. But stay tuned you will enjoy upcoming posts.

I don't really have a strong opinion on >how big< such and such sauropod was or really size questions in general but I think size in prehistoric animals is often overblown. They were big let's leave it at that.

Anonymous said...

Ok, and you can call me D-man.

D-man said...

Hey Duan, D-man here again. I have a hypothesis (kinda like your hypotheses). I looked at the skull of a T.rex and since it could withstand high pressure, I was wondering if males of a species had competitions in where the males would basically have shoving contests with other males, since 1) T.rex has a strong skull, and 2) The heads of T.rex were adorned by small bumps would have been covered by keratin in real life. My hypothesis suggests that the males first tried to intimidate each other and if it failed, they would then proceed to interlock their "horns" with each other and try to push and shove the competitor to the ground. Then the dominant male would proceed to mount the loser to assert his dominance (probably what the hands were for). Of course this is just my hypothesis, but I would like to hear what you think of it.

As for the "biggest dinosaur", your right, the size of the animal only tells part of the story, their are other questions like how did it survive in its world, how would its size help it get food, or how it helps it reproduce. But of course, the media sometimes glosses over these things and just focus on the size of the animal. Also I forgot to say...


D-man said...

Hey Duan, back again and I hope your doing well, and I found out that although theropods probably did not have the channel papillae, they probably had serrated tongues, since cats have these too, and yet already have teeth to kill. Cats have these to scrap off all the flesh, so maybe this kind of serrated tongue came in handy during times of little food, and they probably had these serrated tongues to scrap off the last scraps on the carcasses. I am not taking your depictions too literally, this is just my own hypothesis since cats already have teeth, yet have serrated tongues. I even found some more images with hyenas that seem to show serrated tongues (not to the extent of cats). I would imagine hyper carnivorous coelosaurs such as raptors, troodontids, and tyrannosaurs would have these to scrap off every last piece of meat from the carcass, accessing maximum nutrition and energy. This is just a hypothesis of mine of course and correct me if I'm wrong.

D-man said...

By the way, the documentary you were thinking of that shows that T.rex pulls in it head and tail towards its body is the BBC documentary, The Truth About Killer Dinosaurs.

Robert Haan said...

So any hints on what you intend to write about next Duane ? Only been a few posts so far this year , but they've all been packed with all sorts of goodness.
Looking forward....

Duane Nash said...

Thanks for interest. Because of my job I can only get so many out. Here is a hint, I'm taking on the king next... with implications for all of theropoda. Might be startling and make you question how certain assumptions about how theropods look came into vogue. Have an open mind, it might not convince you but it will make you question...

D-man said...

Ooo, all aboard the hype train!

Robert Haan said...

Yeaa , you know for someone who's not part of the intellectual elite , i'm quite impressed with how well thought out your articles are,ever since Spinogate my minds been open to all sorts of possibilities , not just regarding theropoda but including the entire dinosauria as well, seriously the real things are way cooler and more interesting than what movies like JP and its kin can give us(having said that i did enjoy the movies, all four of them very much)

Misheru Misaki said...

I've been keeping up with your posts on Spinosaurus and I have to say I think yours are easily among the most plausible restorations I've seen.

I'm interested to hear your opinion on the idea that Spinosaurus sail could have been thicker over the hips as the neural columns themselves are quite a bit wider. I had originally planned to use this reasoning for my reconstructions to giving Spinosaurus a bipedal gate with the thicker structure serving to aid in balance, but I had never heard that about the iliac before. What purpose do you think this sort of a structure could have served and do you think it would be enough to present a plausible stance for Spinosaurus being capable of -but not reliant on- bipedal movement?

Duane Nash said...

I find the bipedal stance on solid ground unlikely. It just was not evolving in such a way that a terrestrial mode of life was important for it. I find all these - some rather clever - tweaks of anatomy such as a very heavy tail or modified dorsal tendon bridge or what you are suggesting rather anomalous in light of the diminished ilia and knee and vertical support. If spinosaurus was bipedal on land why is it diminishing these very necessary vertical components? Easier to just maintain vertical support in muscular/skeletal anatomy and NOT evolve all these other extraneous and quite frankly less than parsimonious solutions to retrieve bipedalism.

Misheru Misaki said...

My thoughts exactly after finally (as you said a real shocker it's not been brought up more often) hearing that about the ilia. It honestly just seems silly by this point to claim Spinosaurus was an obligate biped. Although I'm still willing to entertain the idea of a facultative biped even that is becoming more speculative.

Prechristoric Sapien said...

Just one little nit-pick or whatever you want to call it. The problem I'm imagining is how they would reproduce. I'm necessarily talking about the mating part of it all, but how and where would they lay their egg(s), would they migrate, or is it the first dinosaur to give live birth (probably not). Just how would an animal with a life style so different from its kin and ancestors tackle this new problem?

Duane Nash said...

They probably rested and basked on land like crocs or seals. Females would find a spot above high tide line to lay eggs just like a croc.

The Eurypterid said...


Just posting to say that this year's SVP abstracts featured a simulation of Spinosaurus- they found it to be able to float, and that it likely had a far enough back centre of mass for bipedal motion to be a valid and sensible likelihood. Does this affect your own hypotheses?

Duane Nash said...

I have not read their work.

Misheru Misaki said...

I see no reason to assume changes in balance would change anything. The leg muscles weren't built for supporting weight, doesn't matter how well it was balanced.

MrCrow said...

Hello Mr. Nash
According to the latest SVP, Spinosaurus and Suchomimus seemed to grow denser bones with age (and no this isn't under embargo fortunately). This is consistent with other aquatic animals like penguins. Young Suchomimus groups with birds and other typical theropods while adults group more intermediate. Ibrahim's Spinosaurine groups with subadult alligators. Also Ibrahim's Spinosaurine was only 17 years old at the time of its death.

Duane Nash said...

Hey thanks for heads up MrCrow. I remember the abstract but have not read further on this study because I'm moving right now. If this suggests that the young may have been >more< terrestrial that is really cool and what I've been suggesting for dispersal/movement strategies. That Suchomimus seems to suggest a trend towards Spinosaurus in terms of bone density and presumed aquatic dependence is also very cool.

Marcos Pinheiro said...

Hello, Duane Nash.

I'm Marcos.
It's a pleasure to meet you and write here on this remarkable blog of yours about your points of view in prehistoric life and research. Love the amazing and unique comparisons you did with the modern living animals with the new Spinosaurus so far. And your ideas and suggestions about belly sliding, possible thick dermis and other possible functions of the sail are amazing and well thought! I learned so many things about tapirs, manatees, loons, penguins and hippos that I never knew before, and from the clever questions made by viewers and your replies to them! You really have a big imagination and scientific evidence altogether to reach new questions and views about dinosaurs! :D

I'm working on a dinosaur project of my own and the first one is about the spinosaurids.
I'll focus more the possible lifestyles of Spinosaurus, Baryonyx and possibly Irritator.
Other blogs, including yours, books and websites are helping a bunch to my project!

But I have a few questions that I thought I should ask you:

a) I totally believe the neotype's age and its parts are from the same individual thanks to you and other sources I've found. But if Spinosaurus really lived mostly in water, as I believe too because of its bones and oxygen isotope compositions in 2010 paper, how did or could possibly survive the drought seasons as shown in BBC Planet Dinosaur? And how does the hippo survive in that harsh season as well?

b) If it really belly-slided, how were its arms positioned? Did its clawed fingers touched the the ground while is belly-slided?

c) Female crocs dig with their hind limbs and front limbs, so Spinosaurus would use just its arms and hands to dig or its back webbed feet could do the job too?

d) So far, as I read your Spino Saga trilogy and comments, I think an adult Spino could knuckle-walk sometimes and rarely rear on its legs with its tail like a tripod only to intimidate an adult Carcharodontosaurus if dared to attack it on land. But what do you think about this, if they crossed each other like lions and a hippo sometimes happened?

e) I read a part of the book called "Weird Dinosaurs: The Strange New Fossils Challenging Everything We Thought We Knew" by John Pickrell, and its says that sicentists believe it was territorial with its sail displaying its size and age to others. This is interesting and the crocodilians today are also territorial, BUT some like the Nile Crocodile are gregarious and attack in a mob and the oldest or the biggest have the rights to feed the kill first, but some are very agressive and not tolerant with others like the Saltwater crocodile. With so many Spinosaurus fossils found, do you think it behaved more like the hippos and Nile crocs or more like the salties?

Thanks for reading my comment and I'll be waiting for your opinions and answers, Duane. :)

Michelle Wall said...

I'll let the professionals handle the rest but as for Planet Dinosaur, well it just goes to show you shouldn't trust everything you see on TV. Documentaries aren't about education, they're about making sure they get "all the coolest" dinosaurs doing "all the most bad-ass" fights. It's about that 5-10 year old demographic for them and nothing else, period.

Planet Dinosaur in particular was quite awful, an absolute smorgasbord of incorrect anatomy, misplaced or missing feathers, animals that never lived together fighting, and arbitrary natural disasters. Spinosaurus didn't coexist temporarily with Sarcosuchus or Carcharodontosaurus, and it would not have had to deal with seasonal droughts. It lived in coastal mangrove rich swamps, not inland wetlands.

Marcos Pinheiro said...

Yeah, I'll wait for the professionals to answer my five questions I wrote.
But thanks for the warning and sharing your opinion about the probability of any seasonal drought in North Africa, Michelle Wall.

Now take a look at these readers and viewers! The Eurypterid is right! SVPCA and SPPC in Liverpool revealed many things including this curious research about the Spinosaurus buoyancy comparing with Tyrannosaurus if it was in the water in August 25th, 2016! Sounds pretty crazy but it's still interesting. Here's the link to prove everyone:

Marcos Pinheiro said...
This comment has been removed by the author.
Marcos Pinheiro said...

And this picture by Alessandro Chiarenza shows the Henderson's digital model with the center of mass closer to the hips than previously estimated.

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