Friday, October 14, 2016

Night Stalker Rex Part II: Tyrant Tummy Tucks & Where the Rubber Meets the Road

As Khalil Beiting pointed out in my last post T. rex is actually not the only known barrel chested terrestrial theropod. Allosaurus, though certainly not displaying the thickness of T. rex, has a pleasantly plump countenance. And certainly all other tyrannosaurids display a thickened torso to varying degrees. In the case of Allosaurus a highly agile, cursorial nature need not be selected for - giant sauropod carcasses, sauropodlets, and stegosaurids are not winning any foot races. Having a little extra in your back pocket might come in handy for Allosaurus when wrestling teenage sauropods and intimidating/fighting over carcasses with rival mega-avepods. In the case of other barrel chested tyrannosaurids I believe this increasing girth - culminating in T. rex of course - speaks to a general trend of highly sensory adapted, nocturnal, stealthy, territorial, quick killing, and calculating predators.

Of course when I speak of "fat" tyrannosaurus or other theropods I am not implying that they are fat the way a super weaner elephant seal pup is. Obviously they probably carried some fat depending on the season and condition but this fat would be concentrated at the base of the tail, thigh, abdomen and hip near the center of gravity (kind of like a chicken). When I speak of "fat" T. rex & tyrannosaurids I mean that they are coming at you with the thickness. A professional football linebacker or a sumo wrestler are both athletes, are both powerful in any sense of the word, are both athletically gifted in any sense of the word, and they both  are carrying not a little, but a lot of fat. But these "girthy" athletes are probably in better shape than the average reader of this blog and one would hesitate to call them "fat" in the negative connotation of the word if they were within arms reach of you.  It is a bit paradoxical that such large athletes are rarely described as "athletic" even though they perform amazing feats of power and strength. The term "athletic" seems to be reserved for only the svelte, lithe, trim, and quick athletes in the pantheon of "attractive" olympic body worship culture.

pro-baseball player Prince Fielder

It is this bias I speak of - "what constitutes athletic?" - and how this concept intertwines with being slim, of low body fat percentage, and being of a culturally established level of physical beauty and attractiveness. It is this bias, I assert,  that creeps into and underpins our thought processes when imagining what constitutes athletic and attractive creatures of deep time and how they should look.

olympic athlete Holley Mangold
It is my contention that we want slim attractive theropods - especially tyrannosaurids - because this matches what we want to see in our own vaunted athletes. Slim equals beauty, success, athleticism, and adaptive superiority. Fat equals ugly, inferior, sickly, tired, slow, and headed towards the evolutionary dustbin. The notion of fat dinosaurs, especially fat theropods, also strikes a dissonant chord within us because this was the predominant past visage of dinosaurs prior to the dinosaur renaissance. And we all know that the past researchers of dinosaurs (pre-renaissance) got everything wrong, right?

Gorgeous George and some dumb duckbill. credit Archive of Field Museum

Above is the old - and now overhauled - predatory pose of Daspletosaurus dubbed affectionately "Gorgeous George" over some dumb duckbill at the Field Museum of Chicago (special kudos to DinoGuy2 from the dinotoyblog forum for jotting my memory of it). Although I never saw it in person I do remember this image vividly from my childhood. What I want to talk about is not the outdated vertical mount, or the tail dragging, or the pronated hands, or the dubious taxonomic status of this specimen. Go read this excellent write up The Glorious Journey of Gorgeous George if you want to learn more about the history of this mount. What I want to draw attention to is the gastralia in this mount that denotes a very thick and round countenance.

Gastralia are rarely included in mounts, even to this day, and I can't overstate the caveat that skeletal mounts sometimes get it wrong. On the other hand can anyone prove to me that the gastralia as depicted here did indeed get it wrong? As noted in the linked history of this mount the gastralia is not of the original bone. But it looks to be a pretty seemless transition of the gastralia from the pubic bone to the furcula. Based on articulated specimens of other theropods with intact gastralia this should be what to expect.

stolen form some creationist web page
What is interesting, and maybe it is just perspective playing tricks here, is that when we look at the refurbished mount of Daspletosaurus at the Field Museum, Gorgeous George looks like he has lost a few pounds.

Did you lose some weight Gorgeous George? credit Funk Monk CC2.0

It appears that Gorgeous George in his new dynamic posture has received a bit of a tummy tuck. Where  did this tummy tuck come from?

Well if you go back and read Predatory Dinosaurs of the World Gregory S. Paul advocated hollowed out bellies for theropods:

"...theropods probably looked lean, sleek, and a little bony, like big dogs and cats. "Plump" theropod drawings are certainly wrong." (Pp. 105)

"Predators gorge at a carcass, then fast until they are hungry again. The stomach is highly distensible so it can hold big meals. In accordance with this the abdominal "ribs" or more correctly gastralia, of predatory dinosaurs were poorly ossifiied, multijointed, and very flexible. So hungry theropods on the hunt should be drawn with hollow cat- or dog-like bellies. In some of the big mounted skeletons, the abdominal ribs are mounted to form a distended belly, which would be true only after feeding on a kill. A satiated theropod mush have waddled away from its meal!" (pp. 106)

His skeletals follow suit. Go peruse his theropod skeletals, especially of any large bodied forms, and you will note he gives a distinctive tummy tuck to the gastralia just after the pubic bone.* But is there any evidence for such a tummy tuck in theropods? Would the gastralia of a hungry theropod necessarily have formed such a hollow cavity or would a theropod belt - line been a bit more ample? I have not found any preserved specimens and I welcome any evidence supporting such a tummy tuck. Crocs don't seem to have it. I can't discern such a tuck in any of the remarkably complete specimens of theropods... you can connect the dots or the gastralia as you want BUT there might just be a bit of a modern day bias in trimming up theropod skeletals/mounts in some cases. Perhaps the ol' skool look had a little bit more truthiness to it than we might initially presume... I have not noticed the tummy tuck in Scott Hartman's skeletals but I do think his flesh outlines are too svelte.

*I am not suggesting that GSP ignored or misinterpreted data merely that his depiction of tummy tucked gastralia is consistent with his assertion of hollow bellied, svelte theropods.

Things seem a little equivocal on the exact neutral placement of gastralia but there is some work done go here. Instead of gastralia allowing a "tummy tuck" look as GSP asserts Classens advocates a more concave look for theropod gastralia:

"In ornithomimids preserved in situ the ventral outline of the abdominal wall as indicated by the gastralia is usually concave. Although this may be a taphonomic artifact, midventral shortening of the gastralial system would result in ventral movement of the abdominal wall (fig 16 A-C below). The ventral movement of the body wall during protraction would result in an increase in trunk volume"

(from Classens 2005)
Also form Classens 2005 it does appear that in crocs there is strong musculature linking the pubic bone to the gastralia seeminly negating the possibility that such a tummy tuck would be apparent in life. Instead the gastralia likely moved as one functional unit and might not "pinch in" to denote an empty stomach. Indeed if an empty stomach would cause the "tummy tuck" look to appear we should see lots of evidence of this look in crocs since they are ectotherms and often have empty stomachs. But do we see this "tummy tuck" in living crocs? Nope.

Chubster Tyrannosaurus from David Norman's Dinosaur! non tummy-tuck
Svelte Tummy Tuck Tyrannosaurus credit Gregory S. Paul used for educational purposes "don't sue me please"

As you can see adding the tummy tuck has a profound effect on how the rest of the gastralia line up, dramatically altering the profile of the animal. Classens cites a paper by Carrier & Fisher that during gastralial retraction the abdominal cavity could expand 14% in Allosaurus !!

non-tummy tuck T. rex postcard from London Natural History Museum taken from Don Glut
credit Neil Lloyd taken from Love in the Time of Chasmosaurus

Obviously the above image has some glaring issues - but maybe the rotund girthiness offers a lot more truthiness in it than we might be comfortable in conceding?

Where does the truth lie with regards to gastralia placement? Maybe a bit in between the Gorgeous George look and the GSP tummy tuck look? Or is that just a needless compromise? Personally I suspect past "chubster" depictions might offer a shade more truth than the more recent svelte, trim depictions. Perhaps we prefer our theropods svelte, trim,  and "athletic" looking just like we prefer our modern day "athletes" to look with respect to olympic body spartan hero kult skinny worship?

Think about balance for a second. Having the most rounded, heavy part of your body towards the center of gravity makes absolute sense for a horizontal obligate biped, especially one with a big head. Functionally theropods would be more stable in that configuration.

Did I just make all theropods - not just tyrannosaurids - "fatter" or phatter if you prefer? Yeah I said it, every svelte looking, skinny, tummy tucked theropod is OBSOLETE!!   ;')

CutiePie by Duane Nash

Weird enough for you?

Whiskers, of course it had whiskers. A big fat tail base because of the caudemofemoralis and fat storage, of course. Prominent pterygoideus flare just like in big crocs - why not for the strongest terrestrial biter ever?  Obscene tufts of thickened skin around the head, neck, and forequarters - biting into the neck of T. rex would be like biting into a flat big rig truck tire. But probably the first thing that catches your eye is dem big honking toes and feet, enough to give any pedicurist nightmares...

The feet of course are why this post is subtitled "where the rubber meets the road" because it is the feet that take much of the impact of the stresses and strains of a biped the size of a small whale. They would need cushioning - gel soles if you will - and lots of it. More so than is pretty much always depicted. In other words pretty much every image of large theropod feet is - OBSOLETE!!!   ;')

Because the feet of Tyrannosaurus and other - quite literally - mega-avepods have to react to the stresses incurred by high weights we should think about the ol' square cube law. Since volume increases faster than surface area large theropods should have relatively bigger, derpier, and more rotund toe and foot pads than their smaller brethren. Trackways confirm this.

Credit Rufous-Crowned Sparrow. Philmount Ranch new Mexico

Richard T. McCrea, Lisa G. Buckley, James O. Farlow, Martin G. Lockley, Philip J. Currie, Neffra A. Matthews, S. George Pemberton -

In situ tyrannosaurid Bellatoripes fredlundi Trackway A images. a) Print #2 of Trackway A (in situ) - PRPRC 2011.11.001 (right); b) Trackway A (in situ) view to the east of prints #1–3. Note the thick layer of kaolinite in the freshly excavated area in front of print #3.
There is also loads of examples of large theropod footprints getting confused with large ornithopod footprints and vice versa. Almost like there is some sort of biomechanical constraint imposing limits on the pedal morphology of giant bipeds? Hint, hint there likely is...

Also of note is the reported gigantic abelisaur footprint of recent news that features a positively gigantic foot pad. I have heard some chatter it might be from a sauropod back foot but when giant biped get their foot on it just may have looked like that...

Not only are giant theropod feet bigger, wider, and more plump than generally depicted, the claw itself was likely fairly elevated off the substrate in neutral position with only the tip contacting the ground and perhaps only when it pushed off. Think more like giant dog paws. YW Lee was kind enough to share this purported photo displaying massive toe pads on the feet of Concavenator. I honestly don't know if I am breaking some embargo here or if this should be taken down (let me know if so), but sheesh that padding is incredible.

Anyways make of these pics what you will, perhaps I severely underestimated the amount of toe padding in my illustration?!?

In any case there are good examples from present theropods that have toe pads to suggest that as bipedal terrestrial theropods get bigger the padding on their feet get relatively bigger to compensate for the exponential expansion of volume (i.e. weight).

Compare the foot padding on a turkey to an ostrich:

credit Malcolm Libury. turkey foot

credit Masteraah. CC2.0

For paleoartists wanting to draw large theropod feet with a bit more truthiness: draw them bigger, plumper, more elevated claws, more uglier, and just plain derpier than you see in all other depictions (including any and all "world renowned" professional paleoartists). It is quite interesting why big ol' toes and toe pads have not got a "footing" so to speak (bad pun is always intended) in theropod paleoart.  I have discussed the patently obvious issue of ignoring abundant large toe pads in dromaeosaurids before - which calls into question a tight grasp needed for the RPR model of dromaeosaur predation. We have had evidence suggesting as such for some time via these footprints. But in my estimation only a paltry foot pad is given and never do you see the claws actually raised off of the ground.

Big, gnarly, ugly toes and feet are simply not as attractive and sexy as the slender, refined, and petite toes and feet of modern theropod paleoart. We keep wanting to export our cultural baggage with us in our excursions into deep time.

So back to stalking technique and what big foot pads, chubby toes, and gel shoes meant for T. rex and other large theropods. What these attributes imply is that one of the most iconic scenes from Jurassic Park - the cup of water rippling at the approach of T. rex - is truly and utterly false. Not only that, such a noisy approach is diametrically opposed to the stealth mode that these animals operated in.

T. rex and other giant avepods would have been disarmingly quiet when walking around. Their huge and fleshy toes and foot pads smothering and muffling the sound of any snapping vegetation or substrate that might betray their presence. In heightened stealth mode - when they were actually stalking - they would have moved with the precision and care of a gigantic heron. Students of natural history should immediately think of the commonly observed silence that elephants can move with. An uncanny ability to slip into stealth mode is often attributed to these animals by hunters/poachers/naturalists as they can at will slip into the brush and disappear noiselessly.

Elephants are also useful in providing an example of unequivocally gigantic, stealthy, and strategic (plant) predators that make successful and repeated nocturnal raids on the subsistence farms of hyper vigilant but nocturnally ill - equipped hominins.

When T. rex and other tyrannosaurids were not out performing stealth raid operations at night what were they doing during the day? Probably a lot of lounging around on their big fat bellies, preferably in a morass of cooling mud or body of water like the self satisfied tyrants they were. Probably looking quite ridiculous while doing so. And yes they could lie down just as I depicted below. (Pp 199 Ch. 11 Rex, Sit: Digital Modeling of Tyrannosaurus Rex at Rest Stevens, Larson, Will & Anderson Tyrannosaurus Rex: The Tyrant King).

Cuz bad asses do what they wanna do and they don't care what you think about 'em or how ridiculous they look doing it.


From Amlaner & Ball 1983. encountered here


The Glorious Journey of Gorgeous George. Extinct Monsters

Classens, Leon P.A.M. (2004) Dinosaur Gastralia: Origin, Morphology, and Function. Journal of Vertebrate Paleontology 24(1) 89-106: March 2004 online

Paul, Gregory S. Predatory Dinosaurs of the World. 1988 New York Academy of Sciences. Sime & Shuster

"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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Saturday, September 24, 2016

Night Stalker Rex Part I: Sue Is Built Like A Brickhouse

Here it is folks - the king of all kings, the prize fighter of antiquity, the grand poobah, good ol' sexy rexy himself - as you have never imagined before. Some say that we know more about Tyrannosaurus rex than other extinct animals - or even extant ones - and it is high time other lesser known animals should receive attention. Until recently I was of the same notion. However a new flurry of T.  rex research - highlighting it as an intelligent "super senses" endowed predator - has stirred a quiet but growing mumbling on what it really meant to be the tyrant lizard king. Emerging from the haze of past interpretations a more resolute and astonishing picture of T. rex has been forming in my mind. It is a startling beast quite distinct from past visages but not without a newfound ghoulish and nightmarish quality all of its own. Ladies and gentleman I give you Night Stalker Rex.

credit Robin Liesens

"Now wait a second here" you might be thinking "I have heard about likely nocturnal behavior in T. rex and other theropods before - nothing new here." And you are right, it has been suggested before. Indeed a central tenet of this hypothesis - the specialized detection and predation of sleeping dinosaurs by T. rex - has been at least cursorily mentioned at least once on the interwebz.  But you will not find the idea sold to you with quite the same zest and zeal that you will get from me. And you will not find several new and compelling lines of evidence put forth by me that further leverage and embellish the night stalker rex hypothesis.

To get the cognitive gears pumping I want to address a potential role of nocturnal hunting in a modern day T. rex sized predator - the killer whale (Orca orcinus).

This video is astonishing. What really captures my interest is not so much the explosive action and graphic violence but the more economic questions of foraging efficiency. The pod of orcas has obviously positioned themselves at depth - maybe even partially concealed by features we can't discern from the surface - and execute a precise ambush on a large pod of common dolphins. The orcas - which combined as a predatory arsenal must weigh several dozens of tons with appetites to match - expend much energy, foresight, and effort to snatch up just one small dolphin. For what amounts to basically a hard won "snack" for one orca much less for the whole pod the question arises "how efficient is such a foraging tactic for these massive, hot blooded, predators?" Now that the pod of dolphins is aware of the orcas seems the chance for another capture is remote... Not a great optimal foraging capability for the oceans top predator... Or are we looking at how orcas hunt - or more precisely "when" they hunt - in totally the wrong manner? Ask yourself this: for a predator that utilizes stealth to hunt a very agile and intelligent prey would it not be even more efficient for orcas to utilize the cloak of darkness for better tactical advantage? In diurnal predatory events in orca are we not in fact witnessing the exception to the rule of a generally nocturnal predator?

It is paramount to take heed of the obvious bias in wild orca research. Humans are diurnal. Humans are not marine. Most studies of wild orca will be conducted during the day for obvious reasons of practicality, safety, and ease of observation. Working from a research boat on difficult seas it is patently obvious why the overwhelming majority of wild orca research would occur during the day. Because wild orca are mainly observed during the day and because predation events are therefore only observed during the day the emerging bias becomes reinforcing - Orca are diurnal and do their hunting during the day.

However all may not be as it seems with the blackfish and an emerging trickle of data might in fact point to a more nocturnally active hunter than previously suspected.

By recording vocal activity at night at St. Paul island in the Bering Sea researchers K. Newman and A.M. Springer were able to elucidate not only heightened vocal activity at night in transient marine mammal hunting killer whales but they attributed this to predation events. Not only were calls recorded during the night but vocalizations peaked 1 hour after sunset and were more common from midnight to noon than noon to midnight (keep in mind the long days of the northern summer). Although transient killer whales remain silent during the hunt, after a chase or kill is initiated a flurry of calls commences - which when combined with the nocturnal foraging of the prey animal (northern fur seal) - led the researchers to conclude that nocturnal foraging was very important for these transient killer whales.

Could we be on the cusp of recognizing the importance of nocturnal foraging in many or even most populations of killer whales? The obvious utility of ambush technique shown in the above video suggests that such tactics would only be more adventitious at night, especially for an acoustically sensitive predator. The possibility is certainly there and it is easy to see why a bias of diurnal activity in these animals took root. Such a reversal in our thinking is certainly not without precedent.

Nocturnal hunting in great white sharks was only recently documented overturning the diurnal dogma that afflicted the nature of these fish; spotted hyenas long assumed to be solely scavengers from day time observations but long term studies including night time observation elucidated their predatory nature; and the king of beasts has long been known to be a primarily nocturnal hunter - what is less appreciated is that the male lion - long regarded as the inferior hunter compared to females - can actually hold his own as a nocturnal ambush predator of thick brush.

from here
Game cameras are revealing startling and explosive predatory action that occurs under the cloak of night such as this wild chase and capture of feral pigs by an American black bear - an animal not usually noted for stalk, ambush, and predatory technique.

Hunting dangerous, elusive, and quick quarry by predators under the cloak of night is a time honored tradition. Intuitively this makes sense, better to stalk and ambush prey from darkness. Nothing particularly revelatory about that. However there is a seldom mentioned facet of nocturnal predation that - when your prey is herbivorous - consistently tips the balance of power in favor of the predator. It is an inherent advantage the predator has that the herbivore can really do nothing about. One has to ask the question before one can come to an answer: "Why, if nocturnal vision is so advantageous for nocturnal predators, have not herbivorous prey answered the evolutionary arms race by evolving excellent nocturnal vision themselves? I mean, its not like they have not had enough time to evolve excellent night vision as this nocturnal depredation has been going on for some time likely. Darwinian evolution would almost predict such an advantageous adaptation arising."

The answer to be blunt is that herbivores can not, and likely never have, equalled the superior night vision of their predators because they can't. And it's because of what they eat.

Luckily enough through the power of google search I was able to source this little free preview snippet which I will provide below from Essential Fatty Acids and Eicosanoids: Invited Papers from the Third International Congress (ed Sinclair & Gibson 1992) from none other than the American Oil Chemist's Society:

Vitamin A is concentrated in animal tissue but scarce in plants. It is essential for night vision and because predators have a ready and pre-made form of it they will always have a greater capacity for night vision relative to herbivores. Not because herbivores would not benefit from good night vision but because of biochemistry. Yeah science!! If the present is the key to the past and the same unequal playing field occurred in dinosaurs (no reason to think that it didn't) there was likely a high bias of nocturnal theropods stalking the Mesozoic nights. T. rex - as an obligate hunter - certainly slots in nicely to this realm.

The question then becomes "well if T. rex was a nocturnal hunter what type of hunting strategy did it use?". Various methods could and likely did take place such as ambush  at known prey "hot spots", stampeding prey into confusion, stalking of prey in dense foliage, pursuit etc etc. Long story short I think all of these tactics were utilized during the different ontogenetic stages of T. rex. The more light and leggy youngsters utilizing more athletic, running pursuit strategies morphing into a more stealthy, ambush style predatory tactic with the onset of robust build and large mass.

For this hypothesis I want to concentrate on the onto-morph of the adult T. rex. We are talking about Sue sized rex here. And this is an important distinction because a tenet of this hypothesis is that the hunting strategy of other, smaller  tyrant lizard species was encapsulated in the ontogenetic history of T. rex. Essentially in moving up in size through sprightly large coelurosaur sized juveniles, to Albertosaurus like teenagers, to Daspletosaurus sized subadults the behavioral ecology of these respective tyrants was mimicked. But by the time we get to "Sue" sized adults T. rex was playing a different predatory ball game altogether.

Sue Is A Brickhouse - Built Like an Amazon

First of all time to talk about the elephant in the room when it comes to T. rex. And I literally mean elephant in the room. Sue not only was big, she was a certifiable fatty. Sue was not just a tad bit on the hefty side, she would have in life appeared ponderous and round to an almost cumbersome degree. Seriously T. rex as depicted in paleoart is probably the most shrink wrapped, trimmed up, and "wishfully" sveltely depicted  prehistoric animal of all time. Its like there is a collective denial of T.  rex's true body type. T. rex paleoart is the equivalent of gaining a few pounds (or a lot) and keeping that selfie around on social media from when you were trim. And I am not just discussing fan art or deviantart renderings of T. rex - I am talking about the big name "world renowned" paleoartists. You can take your pick, I say that they all underestimate the genuine "girthiness" of ol' sexy rexy. Not by a little, but by a lot mind you. It's time we embrace the big rex and stop the body shaming denial. Big is beautiful!!

If you want to move towards a more realistic countenance of T. rex draw an animal fatter and more rounded than pretty much all other depictions. Now make that animal 20% larger still!!

Have your doubts? Remember there was that little study published a bit ago by Hutchinson & Makovicky? They found that previous estimates were substantially low and their computer modelling suggested an increase of about 30% pushing Sue up to about 18,000 lbs or 9 tons - and they call this size on the conservative range!!

I got a chance to visit with Sue and talk to her about her self image and eating issues as she recently stayed at the Santa Barbara Museum of Natural History. Let me tell you that song "Brickhouse" (She's a brickhouse, just letting it all hang out") does not even come close to doing her justice.

"Sue" credit Duane Nash

When you really look at Sue - and to a lesser extent smaller adult rexes - once you get past the huge maw, lethal bananas, and overall size - you have to be impressed with that barrel chest. I mean come on now, if you take the perspective of the above photo and add on even just a smattering of integument, skin, muscle, and fat to the torso you quite literally would not see the hips from behind that thick barrel chest!!

"Sue" torso credit Duane Nash

I mean really now, it's just ridiculous. Especially when you compare the torso against other slab chested theropods or even other herbivorous dinosaurs for crying out loud. Go look at the various museum mounts of T. rex mounted in pursuit of herbivorous prey - the degree of roundedness in the torso of rex even crushes the giant, rear fermenting sauropods, ceratopsids, and hadrosaurs it was hunting. While not as wide as ankylosaurids T. rex certainly had a deeper chest than they did. Also compared against the torso of canids, felids, and even ursids T. rex looks unambiguously ahead of the curve in terms of a massive torso.

The real elephant in the room is not that T. rex had a massive barrel chest - that has been known and commented upon for some time - the issue is that no other terrestrial tetrapod predator has such a barrel chest!! You really have to go into the aquatic realm to find such girthy predators, animals that have escaped the burdens of gravity. Obviously T. rex is no whale or aquatic animal - it still had to operate under the confines of 1 G - but I do think it had escaped the traditional limits of what it means to be an agile, cursorial predator. No longer hemmed in by ecological and functional constraints of maintaining high degrees of speed and agility other evolutionary pressures dictated an increase in general size, robusticity, and overall swelling of the tyrannosaurid bauplan. These evolutionary pressures included territorial defense, intimidation of rivals, garnering mating privileges, and storage of fat for lean times. All of these Darwinian benefits would dictate and be benefited by increase in size/girth but only after the evolutionary pressures that necessitated speed & agility were lifted. In other words T. rex only could become the T. rex we know and love after it developed uncanny predatory technique as a cryptic, nocturnal, super senses equipped, arch predator specializing in detecting, infiltrating, and apprehending sleeping dinosaurs.

So how fast was T. rex

Obviously this is not a full on review of the research into tyrannosaurid speed. But it is my personal reconciliation of the data and not at all incongruent with accruing data and more coming down the pike suggesting that for T. rex (and probably many gigantic theropods) they were NOT SO FAST (or more importantly agile).

People love to ask this question, and paleontologists love to give eternally "sitting on the fence type answers" - as they should because we really don't know. Not only that but solid, concrete speed numbers on most extant animals is lacking. What I will say is this. Unless Usain Bolt is a secret paleo fan and reader of antediluvian salad, T. rex is probably faster than anyone reading this blog. Now, one statement I hear again and again is that "it does not really matter how fast T. rex was as long as it was faster than its prey". Which on the face of it seems like a reasonable answer, if you are assuming that T. rex was a bit of a pursuit predator and that leg length is a prime determinant of speed. But I am not quite so sold on this line of thinking because there are some notable exceptions - chiefly bears - which constantly fly in the face of the dogma that dictate long lower legs equal high speed.

Based on relative leg length we should expect camels to thoroughly smash bears when it comes to speed...

If both bears and camels were extinct based on comparing lower leg elements the camel would be asserted to be faster. The camel can indeed move pretty fast - indeed I was astonished when actually seeing them get into a full on gallop in the video below - but I would not by any means be confident that in short bursts bears are not just as fast as the longer legged camels.

When it comes to speed in T. rex, its likely prey base, and what it means to be a good & efficient predator I think the questions we ask play a big role in the solutions we seek. When we ask "how fast was T. rex?" implied and embedded in this question is that pursuit was important for T. rex and however fast it was it had to have been faster than its prey base in order to make a living. Instead of trying to get to answers based on the question of speed - which may in fact be a wash when compared against its prey base because of bears and how they break the rules - let us instead ask a more incisive and telling question: "how agile was T. rex?" This line of thinking has more merit to it than simply asking "how fast?" because when you couple the agility of T. rex with the attributes of its prey base there are some significant conclusions to be drawn.

T. rex was horrendously not agile. Indeed it is hard to imagine nature coming up with a design less equipped to handle tight turning. A tall biped, long and heavy all over. Once it gets a head of steam going in one direction it has horrible turning ability. Kind of like running while carrying a big heavy, long log and being asked to twist and turn. Hutchinson (yes the same Hutchinson form the revised mass estimate paper) came to this conclusion when he looked at the turning ability of rex. Ultimately the study concluded that T. rex took a full 1-2 seconds to make a quarter turn (45 degrees).

Past assertions have all resorted to the stock answer that T. rex was "just good enough" to chase down its gigantic prey base are lacking. First of all we don't have reliable speed indexes of modern animals much less extinct ones. The ability of short legged bears to sprint at the speed of long legged ungulates casts doubt on the mere long legged argument to infer high speed. We can't be confident that T. rex was faster than Edmontosaurus, Triceratops, or hell, even Ankylosaurus!?! Short legs, if well muscled and full of bouncy tendon can still do the same job of long legs. But one thing we can be certain of - more than the relative speed argument - is the relative agility index between T. rex and its presumed prey. And here we can see - unequivocally - that T. rex is not on a level playing field with its prey, all of which were quadrupedal with a lower center of gravity and better turning ability. If we combine this with the possibility that some of these herbivores were as fast or even faster (da' bears) than ol' sexy rexy we come to the distinct possibility that these animals could run circles around ol' rexy. Indeed if T. rex was a pursuit predator of gigantic and dangerous prey that could easily outrun, outmanoeuvre, and kill it T. rex would have quickly become erased from the fossil record. An obsolete and inefficient design with glaring flaws that can not be ignored or explained away.

Quite a predicament for rexy to be in if it somehow had to make a living off of catching these animals and - especially in the case of gigantic hadrosaurds, ceratopsians and ankylosaurids - these animals could out manoeuvre you and potentially mortally wound you too!! What is a T. rex to do?

The answer is that (adult morph) T. rex did not chase much of anything down except maybe another T. rex. Ol' sexy rexy eschewed the whole speed game altogether and in doing so achieved both great hunting prowess and great size. It snuck up on dinosaurs both awake and asleep - although sleeping dinosaurs became more of a specialization in larger rexes - under cloak of darkness. The average "chase" was measured in just a few meters or even centimeters. This opened up rexy to exploit not just the large ceratopsians, hadrosaurids, and ankylosaurids that it shared its habitat with but rex could now exploit all the smaller and even more agile dinosaurs it shared its habitat with. A true ruler - a tyrannical rex in every sense of the word - that by highlighting stealth and negating speed it could demand caloric tribute from every underling in its kingdom. Literally nothing was safe in the kingdom of rex - everything from armored ankylosaurids to speedy ornithomimids - could and did end up in the belly of the tyrant ruler king.

I guess I was a little naive in imagining I could get through this hypothesis in just one post. In this post I wanted to concentrate on the unparalleled girth of rex, highlight the fundamental underestimate of rex's size both in both paleoart and technical literature, and show why, if there is any sort of consensus on rex speed & agility, it should be moving in a direction of caution with regards to extremes in both of these dimensions. 

Up next I want to delve into the super senses of T. rex, how to be a giant stalker, and why T. rex had a "childhood".


Hutchinson JR, Ng-Thow-Hing V, Anderson FC. A 3-D interactive method for estimating body segmental parameters in animals: application to the turning and running performance of Tyrannosaurus rex (2007) Journal of Theoretical Biology vol 246 Issue 4. 21 June 2007 abstract

Hutchinson JR, Bates KT, Molnar J, Allen V, Makovicky PJ (2011) A Computational Analysis of Limb and Body Dimensions in Tyrannosaurus rex with Implications for Locomotion, Ontogeny, and Growth. PLoS ONE 6(10): e26037. doi:10.1371/journal.pone.0026037

Newman, K, Springer, AM. Nocturnal activity by mammal-eating killer whales at a predation hot spot  in the Bering Sea (2008). Marine Mammal Science, 24(4): 990-999 (October 2008)

Zelenitsky, DK, Therrien, F, Yoshitsugi, K. Olfactory acuitty in theropods: paleobiological and evolutionary insights (2009) Proceedings of the Royal Society of Biological Sciences. link

Wednesday, September 14, 2016

Microraptor Shenanigans Part II: Like a Shadow in the Night

Duane Nash

Pretty much ALL aspects of Microraptor have achieved special attention and thought. In this post/article - which is really a continuation of my take (and others too) on Microraptor as an especially diabolical and efficient predatory terrorist of all things small - I am going to highlight an aspect that has been startling, controversial, and plagued with misunderstanding, coloration. Ahem, not just coloration but structural coloration i.e. iridescence (Li, 2012).  More specifically that iridescence does not in fact preclude a nocturnal lifestyle.

Reader beware and tread carefully. Many of the arguments and thoughts I will bring forth stand on necessarily shaky ground. That is because issues of coloration, roosting behavior, iridescence, cryptic coloration, "cloaking" and other aspects of modern animals are woefully understudied and really on the cutting edge of modern animal research much less in long gone paravians. That does not mean I am not going to "go there" and in the end create a startling and believable lifestyle portrait of Microraptor gui.

For this piece I am going with the notion that the coloration of Microraptor is indeed black. Although arguments for degredation of color fibers etc etc. have been put forth I don't find them especially compelling. I might be wrong, but for this piece I am going with all black. Which really is a good policy for attire anyways, when in doubt go black. Or even better go with all black and iridescent if you really want to make a statement... For this piece I will address the two issues of black coloration and iridescence separately at first and then bring them together at the end.

credit George Hodan. public domain

Working from an all black plumage in Microraptor the mind necessarily thinks about modern day aves that don an all black attire. Various corvids come to mind - especially the common crow and raven - as well as grackles, and other various birds colloquially known as "blackbirds" in the passerine group. And this is where the confusion and typological thinking really mires us down in our interpretation of Microraptor.

For as much as we might be tempted to or find it "nice and tidy" to leverage arguments about what Microraptor did based on what modern birds do let us remind ourselves that Microraptor was not a bird nor was it ancestral to birds. It was its own thing. More so than that there is a tremendous gulf of time between Microraptor and modern birds - especially advanced "blackbird" type passerines. The environment is exceptionally different between what Microraptor inhabited and where modern "blackbird" gestalt birds generally thrive. Indeed a cool temperate rain forest dominated by giant old growth gymnosperm trees and lakes is about as far from the prairie like, open grassland type habitats that many "blackbird" type birds thrive in. Not to mention the differences in ecology between Microraptor - as yet only known to have eaten flesh - and the more granivorous or omnivorous tendencies of grackles, corvids and other passerine grassland thriving "blackbird" types.

I must ask some questions concerning the repeated occurrence of "blackbird" type birds in open grassland dominated habitats namely, "Why evolve a dark conspicuous coloration that highlights your presence to potentially other color vision attuned avian predators during the day?" You know it's true. Just look at a flock of crows foraging in a vacant lot or a flock of any of a number of blackbirds, whether the vegetation is flush with new growth and is bright green or it is brown and yellow after months of little rain these birds stick out like sore thumbs. Seems a little maladaptive does it not? Unless of course it is not actually maladaptive but exquisitely adaptive actually...

Blackbirds & Starlings in field credit USDA
And here I have to venture forth a hypothesis - a reasonable enough one I think - that the black or darkened coloration of many open habitat communal foraging birds is highly contrasting with the environment for a reason and that is in order to achieve group cohesion. I honestly don't know if this has been suggested before ;') . Birds can detect other foraging birds from distance and therefore keep social unity. More individuals in one place will actually lower the predator risk to any one individual at the same time allow more eyes for predatory vigilance. Having a dark black coloration would also be selected for as it allows birds to spot other birds foraging in food rich areas. That many of the birds engage in predatory mobbing type behavior plays into this.

There is another strategy that links group foraging "blackbird" type birds of open habitats and that is communal roosting in trees. Again here we see that the black or darkened coloration of these open habitat communal foraging birds plays a dual function at night. The dark coloration of these birds helps "cloak" them at night by, well, essentially mimicking the dark night sky. Even dark colored American coots may benefit from this as they also roost together at night next to bodies of water.

crows at roost credit (c) Daniel Hoherd
The defensive tactics of communal roosting birds is woefully understudied. Indeed what goes on at night in communal roosts is hardly looked at. I suspect there is a lot more going on than just sleep in some of the absolutely massive roosts that many birds engage in. The smell, noise, and general ruckus a large roost creates surely must act as a beacon to predators. Normally diurnal raptors might try to pick off roosting birds in early morning or late evening but black birds might just sort of disappear in darkness. Owls you would think could pick off roosting birds with ease but the predatory pressure that they put on roosting birds does not seem to be enough to dissuade the behavior. Likewise felids with their night vision would seem to be ideal candidates to depredate large roosts but cats are fairly near sighted and - when looking up at a dark colored roosting bird from the ground - the birds might just kind of disappear into the night sky. Check out this piece on what cats actually "see". I have done a little of my own field research into night roosting crows on Milpas street in Santa Barbara. A busy street during the day the crows gather in the large English laurels at night. When I checked out what was going on I could hear lots of activity actually. The crows engaged in subdued chatter, there was some movement and flight occasionally. But when my eyes tried to focus on any individual crow it was very difficult. I could kinda tell where they were at but they looked less like discernible objects and more like... negative space. Almost as if they were just black voids in the tree. They did not reflect the street lights - this roost is by a brightly lit gas station - but appeared to just suck up all the light that hit them.

credit Gustave Dore "Not the least obeisance made he" public domain
"And my soul from out that shadow that lies floating on the floor / Shall be lifted - nevermore!!" Edgar Allan Poe "The Raven"

But what works for communal nigh roosting blackbirds today in terms of cryptic coloration at night to avoid predators could work equally as well for a cryptic predator at night seeking to hide itself from prey... take home message: there is an argument to be made that black coloration in Microraptor is a useful element for a nocturnal stealth predator.

And now on to the iridescence.

"All modern iridescent birds are diurnal and therefore Microraptor was not nocturnal"

There it is, that stock line that in one fell swoop took the wind out of the sails in terms of nocturnal behavior (Schmitz, 2011) in Microraptor in many people's minds. Except such reasoning is not as ironclad as some might suggest.

And here is where I have to get all weird, paramilitary weapons technology on ya' all. Iridescence in many animals and plants might have a lot more to do with escaping - or possibly bewildering - detection rather than attracting it. So to prime you for it best check out a clip from one of the best sci-fi action films of all time and one of the best creature designs of all time: 1987's Predator:

The alien predator uses a technologically devised cloaking structural coloration to in fact mimic and blend into its surroundings. This ingenious camouflage was put to excellent use in the movie and the comparison to Microraptor in terms of an agile and multifaceted predator that takes advantage of 3-dimensional space - remember when Dutch (Arnold Schwarzenegger) realizes "It's using the trees."- and structural coloration should not go unnoticed. I realize some may have just checked out with that statement but yeah, I just kind of made the argument that a game hunting, cloaking alien from a Schwarzenegger movie is an analogy to take heed of when thinking about Microraptor.

Still with me? Ok time for a quick primer and some links to structural coloration of which iridescence is one of several types. Structural coloration is any microscopically structured surface fine enough to interfere with visible light. Visible light is not one color as we see it but contains all the colors we can and can not perceive. These "colors" have wavelengths and the microscopic structures in animals can alter these "colors" through wave interference. Based on the structures at hand wave construction can occur where colors are enhanced or wave destruction can occur where colors are diminished. The geometry of the material also plays a significant role as light both enters and refracts off of the structural material. This is why iridescent animals change colors depending on the angle you view them at as does soap bubbles... Still confused? Check out this primer on Iridescence "causes of color" and browse through the other sections.

Back to the question at hand which in this post is deconstructing the statement "Microraptor was not nocturnal because no modern day iridescent birds are nocturnal". My main lines of attack are two pronged and that there are two inherent assumptions implicit in the above statement 1) that iridescence is wholly and totally about "display" and therefore implies diurnal habits and 2) that Microraptor compares ecologically compatible with modern aves. Obviously I disagree with both assumptions and therefore strongly disagree with the logic of the argument itself.

I think one question that begs asking "Is iridescence totally or even mostly utilized in display in modern birds?" Of course in bird like a peacock the answer is an obvious YES!! But peacocks, like the various "blackbirds" I discussed earlier - at least the male - is a nocturnal tree rooster. Under the diminished light of the moon does the iridescence of the peacock perhaps play another subtle role in evading detection?

And what of the common occurrence of not only a dark or black coloration in many communal roosting birds combined with iridescence on one or both of the sexes to various degrees? One example that suggests more of a display trait in iridescence is grackles in which the male is the more iridescent example but starlings confuse the situation because both sexes are iridescent. This could be a case of mutual sexual selection but I suspect that nocturnal evasion aided by iridescent wave interference might be a hypothesis worth exploring. Is the iridescence of starlings totally about display? Or is there a dual functionality going on?

Sturnus vulgaris credit Tim Felke. CC2.0

Again, what goes on in nocturnal bird roosts? what tactics do they use to avoid predation? etc. etc., these are all areas of high speculation and little study. But the common occurrence of dark coloration, iridescence on one or both sexes, and nocturnal roosting is a topic just begging for more study. As I stipulated earlier there is much extrapolation and speculation inherent in this text and argument but I believe (pun intended) there is more than meets the eye with regards to iridescence.

Murmuration of Starlings preparing to roost. Scotland credit Walter Baxter CC2.0
Throwing another wrinkle in the equation what about the dark colored, iridescent cormorants? These are predators and like Microraptor inhabit and hunt in a dark, shadowy realm...

credit birds of the world

I am not completely sold on the notion that iridescence in modern birds is >completely< about display and I move to extend out arguments in terms of uses for iridescence outside of the rather arbitrary context of the restrictive phylogenetic bracket to include other organisms that utilize iridescence. Namely I want to focus on organisms that inhabit forested environments as deep forests serve as the most likely habitat of Microraptor. It is in the adaptational context - or adaptational bracket if you will - that we find not only the highest signal for iridescence in modern animals but also our most compelling arguments for iridescence as an aide in camouflage.

I start with the beetles. Shiny, iridescent, jewels of the animal kingdom. Yet their bright iridescent coloration shining and beckoning forth in the full light of day takes on a more muted, cryptic quality in the filtered light and shadow of deep forest canopy. Yet beetles do not use sexo-social display coloration as birds do but rely on chemical attractants. The high incidence of iridescence in beetles of the tropical forest just begs for an explanation in terms of camouflage and indeed this is the most compelling idea put forth.

Next I want to highlight animals closer both phylogenetically and ecologically to Microraptor which also sport iridescent coloration: snakes, but especially species that offers much utility in terms of understanding an iridescent forest hunting specialist of small things - the rainbow boa (Epicrates centria) of Central & South America and the Boelen python (Morelia boeleni) of Papua New Guinea.

What manner of beguiling tricks of light and shadow do these predators play on their prey in the dark cracks and crevices of their deep forested environment? It should not go unstated that both species are nocturnal...

Boelini Python credit Marc A. Spotoro

As is the case with iridescent beetles we can dismiss sexo-social display as an explanation for iridescence in these snakes as they don't actively display these structures and are more inclined towards scent and chemical cues rather than visual display. Microraptor, though displaced phylogenetically from these two boids, has much more in common with them ecologically and environmentally than the grackles and other grassland feeding birds often compared to it. I would offer that whatever benefits iridescence plays in the lifestyle of these two snakes Microraptor enjoyed as well.

credit Marc A. Spotoro
I would be remiss not to mention that there are several largely subterranean snakes that feature iridescence as well as the pertinent fact that the vast majority of cryptic, stealthy forest understory snakes don't feature iridescence. These observations create the argument that iridescence serves potentially no function at all. Perhaps some type of evolutionary byproduct of other happenings - one of Stephen Jay Gould's elusive "spandrels o fevolution".  Personally I don't think that is the case - the ubiquity of iridescence in numerous understory reptiles, birds, insects and plants points to some adaptive value.

And yes understory plants feature iridescence. Here we revisit an old friend of the blog the lycopsid genus Selaginella species name willdenowii. Discussed in this blog post and in this research paper this clubmoss (not a fern!!) shows striking blue iridescence and lives in deep shade.

S. willdenowii. credit Andre Cardosa
Many hypotheses have been put forth trying to explain the blue iridescence of S. willdenowii and other deep shade blue iridescent plants.  Ideas centered on better absorption of red color wavelength light in deep shade but this hypothesis was not shown by Thomas et al. (2010). Instead blue iridescence might offer several adaptive benefits; a photoprotective mechanism that shielded deep shade plants from sudden exposure to full sun; a visual defense against herbivores. Obviously the second hypothesis is of our interest and I will cut and paste the explanation of Thomas et al. (2010).

This adds another interesting wrinkly to the notion of structural coloration used to evade detection. As iridescence can change depending on the angle of the viewer another potential role for iridescence is confusion i.e. what the authors refer to as "making it harder for insects to form a search image". Note that this shimmering - alternatively blending and contrasting with the background - might offer a potential use for a predator as well by confusing and confounding prey - bedazzling them.

Imagine you are an enantiornithine sleeping high up in your roost at night in a large ginkgo. You are among many other birds. Suddenly you wake up detecting movement coming towards you. It is an animal of the same size as the other birds but it alternatively comes into and out of view in a transfixing beguilement of moon reflection and blackness. Your curiosity and inability to form a solid image of the animal is all the hesitation the predator needs. Just as you tense up to fly it is upon you, jaws and killing claws piercing your vitals.

As I mentioned earlier iridescence and what it means for living organisms is very much at the cutting edge of science for things much less long dead ones. But if the present is the key to past...

Here is a cut-out form a very pertinent review article titled Iridescence; a functional perspective

The authors are keenly aware that what can be used to hide prey from predators can also be utilized to disguise predator from prey:

Militaries Study Animals for Cutting - Edge Camouflage

credit LeeRobertsMe CC2.0

The males of the blue morpho family of butterflies use blue iridescence displays that can be seen from up to a 1 km away announce territory. Peter Vukusic, a physicist at Exeter University of England has been studying how the wing scales of these insects influences light waves. He posits that understanding how these scales work is the first step in creating a revolutionary style of camouflage.

"If you know how to manipulate the way light moves and reflects then you can make a surface brighter or darker."

Vukusic sees the potential for developing a type of camouflage that mimics the color of the surrounding environment - the obvious paramilitary advantage needs not be overstated. Vukusic sees tremendous potential in moths, several species of which he states have developed perfect nocturnal crypsis.

Moths have evolved modifications in their wing scales that swallow up light so their wings appear black:

"Instead of multilayers, some types of moth wings have  thousands of tiny, nipple shaped structures arranged in a hexagonal array. If they are really small, half the wavelength of light, then their effect is to reduce reflection from the wings surface" Vukusic says.

Want to go deeper down the wormhole of biomimicry inspired paramilitary technology? How to disappear completely.

A little unsure about what Microraptor was really up to with its iridescence? Or why so many diurnal active nocturnal tree roosting birds are painted black and iridescent? What purpose does that serve to be all black and stand out during the day? Why is iridescence so common in understory plants and animals? Do iridescent animals shine and shimmer when under dense canopy and/or the pale moonlight? Or does their brilliant iridescence take on another more subdued, cryptic usage under dull light? Feeling a little off balance? A little wobbly? A little less than certain at what you are really looking at in Microraptor through the obfuscating lens of millions of years of subsequent avian evolution, advanced passerine mobbing defense, and open grassland ecosystems? If you are feeling a little wobbly, a little confused, a little bedazzled at what you are actually looking at in Microraptor then good - that is what Microraptor wants you to feel before it snatches your life's breath away. 

And so concludes my little miniseries on Microraptor. A strong case can be made for a highly efficient, nocturnal, cryptic, multi-dimensional predator of small things. Being a predator of small things is no easy feet. Not only are you yourself a prey animal so every bit of time you spend foraging you are exposed to predation but the opportunities for facultative scavenging and usurping easy meals from other animals are diminished. Small bodies lose heat quicker than big ones so that small hot blooded predators need to eat a lot. A small animal predator can't afford to be inefficient. If small felids and mustelids worked with the same efficiency of killing as their larger cohorts they would be soon out of a job. A Microraptor that was a poor runner, poor flyer, and poor climber just would not make it. Instead it was fairly competent in all these realms - and maybe even swimming too (like a dipper). We sometimes speak of the large arch-predators as nature's perfect killing machines but it is really the small killers that outshine the larger ones in just about every metric of killing efficiency. No reason to suspect diminutive dinosaurian predators were any less savvy, efficient, and voracious than their modern ecological equivalents.

Up next I will be looking at a theropod that you may have heard about. A theropod on the complete opposite side of the size spectrum. I will be elaborating on how it was a predator like none we have seen before or since. Consider yourself put on notice.


Doucet, S., Meadows, M.G. (2009) Iridescence: A Functional Perspective. Royal Society Publishing 2009: April 6. online here

Li, Quanguo (9 March 2012), "Reconstruction of Microraptor and the Evolution of Iridescent Plumage", Science335: 1215–1219, doi:10.1126/science.1213780PMID 22403389

Schmitz L, Motani R (2011). "Nocturnality in dinosaurs inferred from scleral ring and orbit morphology". Science332 (6030): 705–8. doi:10.1126/science.1200043PMID 21493820

"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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