Tuesday, December 16, 2014

Plesiosaur Machinations II: The Social Sauropterygian

I find persistent natural history myths, anecdotes, and adages a topic of special interest. These  narratives, stories, adages and anecdotes - usually unsupported by detailed field work and not part of the technical literature - are usually just that, fictional stories, and easily dismissed. However sometimes such popular stories, especially when sourced from people who spend much time in the company of the animals in question, may offer some element of truth. For instance I was talking to a friend of mine who regularly goes deep sea fishing and he told me he prefers to use squid as bait - because brown pelicans (Pelecanus occidentalis) assiduously avoid eating squid. I investigated further and came across an interesting video on youtube suggestive of such avoidance and then went to talk to some squid fishermen at the local harbor (in recent years the squid fishery has been thriving in California waters). The squidders all assuredly and confidently replied no - pelicans do not attempt to pilfer or eat the squid from their catch. Gulls yes, pelicans no. Why is this? The fishermen thought is was because pelicans do not want to consume the internal "pen" of the squid. But I found this argument unconvincing, brown pelicans eat whole fish with loads of bone after all. Brown pelicans, unlike the white pelicans in my last post, plunge from height into the water and engulf prey and water in their pouch. The brown pelican then has to drain out the water in its pouch before swallowing the prey. When a pelican engulfs a mouthful of fish - no problem - but if a pelican engulfs a mouthful of squid it's a different story. At this point the squid can latch onto the inside of the pouch with their suckers or even obstruct and block the throat of the pelican  and thus represent not just a nuisance but a real and obvious choking hazard. Again, nothing in the technical literature on this topic but maybe some element of truth to these anecdotal observations.

And now for another interesting adage regarding peculiar natural history behavior, this time from Australia, and that is that abundant lizards, specifically larger skinks, can keep snakes out of an area. And you can find this sentiment repeated at several places on the interwebz. At first glance it seems that it should be easily dismissed. Indeed one can offer the argument that the opposite is more likely - abundant lizards should attract snakes as potential prey. Never the less, can this story offer some element of truth? The answer is yes, yes it can.

King's Skink chasing Dugite

The King Skink: Snakes Beware!!

Lesley Jackes. communal King's Skinks

Sociality in lizards: family structure in free living King's Skinks Egernia Kingii from southwestern Australia (C. Masters & R. Shine)

Abstract. King's Skinks Egernia kingii are large viviparous scincid lizards from southwestern Australia. Although some other species within the genus Egernia are known to exhibit complex sociality, with long-term associations between adults and their offspring, there are no published records of such behavior for E. Kingii. Ten years' observations on a single family of lizards (a pair of adults plus six successive litters of thier offspring) in a coastal suburban backyard 250 km south of Perth also revealed a very stable adult  pair-bond in this species. The female produced litters of 9 to 11 offspring in summer or autumn at intervals of one to three years. In their first year of life, neonates lived with the adult pair and all the lizards basked together; in later years the offspring dispersed but the central shelter-site contained representatives of up to three annual cohorts as well as the parents. Adults tolerated juveniles (especially neonates) and their presence may confer direct parental protection: on one occasion an adult skink attacked and drove away a tiger snake Notechis scutatus that ventured close to the family's shelter-site. Although our observations are based only on a single pair of lizards and their offspring, they provide the most detailed evidence yet available on the complex family life of these highly social lizards.

So, some lizard curious citizen-scientists decided to go all Jane Goodal on a family of King's Skinks living in their backyard and they document a monogamous, multi-generational, highly social, cohabiting, and offspring defending lizard!! And observed an adult attack and drive away a highly venomous tiger snake!! From the paper, regarding predation and the tiger snake interaction:

We have not observed predation nor found carcasses of skinks within the backyard. However, the lizards responded rapidly to birds flying overhead, with the smaller skinks fleeing first while the adults often remained in place on their basking sites. The skinks showed no overt reaction to bobtail lizards Tiliqua rugosa that occasionally moved through the backyard but we witnessed one vigorous interaction with another reptile species in April 1999. The larger adult E. kingii was found entwined and rolling over and over with a tiger snake Notechis scutatus only slighly longer than itself. When the two reptiles separated, the snake fled with the skink in hot pursuit. The skink later reappeared with no overt injuries.

Now, there are lots of neat stuff in this paper that will be revisited later but jeez, that tiger snake interaction was pretty cool. Going further from the discussion section:

The observation of an adult E. kingii fighting a tiger snake is particularly interesting. The snake was too large for the lizard to ingest (indeed, adult E. kingii are primarily herbivorous: Richards 1990) and the lizard was too large for the snake to ingest. The obvious inference is that this behavior constituted direct parental protection of offspring (which were ingestible-sized for such a snake, and would be acceptable prey for this snake species: Shine 1987). We are unaware of any previous example of such behavior in lizards or snakes, apart from an increase in aggressive responses to an intruder by postpartum rattlesnakes (Shine 1988; Green et al. 2002; see also anecdotal reports for other viperid snakes, summarised by Greene et al. 2002).



And if you want to see a series of aggressive attacks by a large King's Skink on another venomous snake called a dugite (Pseudonaja affinis) check out the two clips below. Filmed on a beach in Australia: my favorite part is the view of the barely interested Aussies looking on like, "Oh a giant lizard battling a venomous snake on the beach? I thought you were looking at something we don't see every day!!"




In both instances the interaction was clearly not about food, competition or territoriality - the inference to make is that the snake represented a threat to the progeny of the King's Skink. So although lizards in general won't keep snakes at bay here are at least two instances that might support the notion that keeping a stable of King's Skinks in your backyard or on your beach might help keep the local snake population slithering along to other places...

Besides the benefits of parental protection, the progeny of these sociable skinks also are privy to choice basking and shelter sites which may be at a premium in their environment. Looking at another sociable skink, the great desert skink  (Egernia kintorei), also viviparious, we see direct benefit given to offspring in the form of residence in extensive burrowing systems that extend up to 13 meters wide, have over 20 entrances, and offer refuge from predators and thermal extremes.

Lizards Cooperatively Tunnel to Construct a Long-Term Home for Family

All right so we can see that there might be some linkage between live birth, harsh conditions, and lack of critical refuge sites and theses factors are good Darwinian reasons for the unconventional social arrangements of skinks of the genus Egernia. And such behavior has even been suggested to be plesiomorphic for the group as a whole. Are there any examples of social lizards that give birth to live young and live in harsh environs that might offer a more independent test? Well yes, yes there is: the desert night lizard (Xantusia vigilis). The discovery of said animals' social behavior is of some interest to me because the researchers are from my alma mata UCSC, and also it is a California species.

Photo credit Mitch Mulks. Desert Night Lizard
Family Ties Bind Desert Lizards in Social Groups. Science Daily. 
Paper Here

Evidently this fairly small, viviparous lizard is extremely sedentary and usually lives most of its life in a fairly small home range. During winter months parents and offspring cohabited under highly localized fallen Joshua Tree logs and other vegetative debris. Offspring delayed dispersal from 1 to 3 years and remained in close proximity to parents although they foraged for themselves. Theses nuclear family aggregations were shown to be stable over several years although the exact benefit is unknown. But the researchers did highlight the link between live birth and social behavior suggesting kin-based sociality is a by product of live birth.

From the Science Daily article: According to (Alison) Davis (lead author), about 20 lizard species are thought to form family groups, and only two of those lay eggs. Viviparity (live birth) is crucial for the evolution of cooperative behaviors, she said.

"Viviparity provides the opportunity for prolonged interaction between the mother and offspring, which predisposes the animal to form a family group," Davis said. "The importance of parent-offspring interaction fits with what is currently understood about evolution of family groups and cooperative behavior in birds and mammals."

Although only recently revealed, viviparity neatly bookends the evolution of sauropterygian evolution in the Mesozoic. A Nothosaur from the middle Triassic and a polycotylid from the late Cretaceous both provide solid and iron-clad evidence of live birth in plesiosaurs and that the adaptation goes back very early in the lineage. Furthermore, the relative large size and single offspring in utero for the polycotylid suggests a very strongly developed k-strategist. This species at least does not appear to have been birthing high numbers of relatively small, live offspring - but investing heavily on a single, large offspring.

O'Keefe & Chiappe 2011


"Many of the animals alive today that give birth to large, single young are social and have maternal care. We speculate that plesiosaurs may have exhibited similar behaviors, making their social lives more  similar to dolphins than other reptiles." Robin O'Keefe, one of the authors of the paper: Viviparity and K-selected life history strategy in a Mesozoic marine reptile. Science 2011.

It should be noted that this view of social plesiosaurs has been met with skepticism. Sharks, which are  also viviparous but don't practice extended maternal care, may be better analogs, some have offered. However no sharks give birth to a single offspring. Plesiosaurs were diverse animals, can we really assert sociality as a whole for the family? Here I partially agree, there was likely a range of smaller offspring-larger brood-less maternal care to larger offspring-smaller brood-more maternal care/extended family bonds among plesiosaurs. But what we are trying to get at is a baseline from which behaviors may deviate towards other extremes. And I think the baseline for aquatic sauropterygian is strongly skewed towards maternal care and sociality. But what about the abundance of immature plesiosaur/elasmosaur recovered from coastal/lagoonal/freshwater deposits/ Could the mothers have been depositing them there and letting them mature on their own in such habitats? Possibly, but various cetaceans such as grey whales/humpback whales are known for utilizing warmer/nearshore/lagoonal habitats to birth their offspring. With occasional stillbirths and/or predator attacks at this vulnerable stage of life we should expect more immature individuals to be represented in such habits.

Of course science, like politics, is a funny thing is that it takes a compelling amount of evidence and effort to overturn previous - even dogmatic - sentiments. And even when this evidence arrives it does not take root immediately but may take several years or even decades to gain traction (case in point feathered dinosaurs). Sometimes it requires the most vocal opponents to well, how should I put it, to die... Who gets to decide what is the most conservative, parsimonious behavior for a group of extinct animals? Plesiosaurs are reptiles and the overwhelming majority of reptiles practice minimal to non-existent parental care. However when we invoke live birth, especially of a single large offspring, the balance of power shifts a bit with a number of viviparous reptiles offering evidence of parental care. When we invoke social behavior and we see that the overwhelming majority of kin based/social reptiles are also viviparous, k-strategists this further speaks to high levels of sociability probable in plesiosaurs. For me the implication is clear - like the skinks and desert night lizards discussed above plesiosaurs were social animals and invested in their offspring (and I am not the first to suggest this). Trying to retrieve a "typically reptilian" social, reproductive, and ecological adaptation for plesiosaurs has become the more untenable stance to take in my view.

Although the obvious comparison to make is between highly social mammalian toothed whales and plesiosaurs I do not think we need to invoke large brained mammalian analogs over what we can glean from contemporary social reptiles such as Egernia and Xantusia. And again, I am not the first to suggest this - O'Keefe: "a more helpful comparison (than mammals) to the plesiosaur may be the monkey skink or the shingleback skink in the Egernia group. These green, scaly lizards give birth to live offspring, one or two at a time, and are among the few known reptiles to function within a social group and care for their young." In short we do not need to try and resolve how a relatively small brained, limited intellect reptile such as a plesiosaur engaged in elaborate social behavior - several extant reptiles offer the context for how such an animal may have behaved socially, and they do not require delphinid levels of intelligence to do so.

Going back to the examples of the King's skink, desert skink, and desert night lizards which I discussed earlier I find it important to highlight another factor that may have helped push these lizards into the social realm and that is that critical microhabitats - shelter sites, basking sites, burrows - are at a premium and by living in extended families there was a net genetic benefit to the lizards that cohabited these areas with their kin. Juveniles did not have to disperse until several years of age to new sites and therefore minimized predation risk. The island night lizard depends on highly localized fallen joshua trees/yucca clumps/piles of dead vegetation to seek shelter and food under; the King's skink dependent on shelter sites/basking sites; and the desert skink on large, complex subterranean burrows. Taking these observations and applying the idea of critical refugia to plesiosaurs presents a problem; there is no where to hide in the open ocean. And so, with the observation of the venomous snake wrangling King's skink in mind, I am going to piggyback on that observation and suggest that plesiosaurs were not fleeing from the first sign of danger - but standing their ground, facing, and fighting - en masse - any potential predator. They moved aggressively in phalanx formation to danger. This is the paradigm of the earlier depictions of plesiosaurs I alluded to in my last post where I suggested that these earlier renderings of plesiosaurs - battle ready, pugnacious, and ready to throw down with any other denizens of the deep - offer >much more truth< than more contemporary works that seem to always portray plesiosaurs as the ill-equipped cannon fodder of the much larger, dominant, and aggressive predators they lived with. Pictures like this one, this one, this one, this one, even birds, and this one. It seems everywhere you look plesiosaurs are getting their asses handed to them, usually with those poor, dangly "oh so vulnerable" necks taking the brunt of the abuse. And yes we do have evidence of plesiosaurs being scavenged by sharks, a Tylosaurus swallowing a polycotylid (not even a long necked plesiosaur), and some suggestive tooth marks on the skull of Tuarangisaurus possibly from a pliosaur (Sven Sachs, 2004 Tuarangisaurus australis... Memoirs of the Queensland Museum available online). And I know I read about possible mosasaur damage to a Mauisasaurus but can't find the ref?... But as far as I can tell no suggestion of neck trauma stemming from predation among all those long necked forms....

And I will suggest that, when in phalanx, plesiosaurs were no easy pickings. Even very large predators will give up the hunt when the element of surprise is lost, their prey detects them, and has the armament to fight back. A Hainosaurus that drives home the attack on a phalanx of elasmosaurs and loses one or both eyes in the process has substantially lowered its own value in the  Darwinian sweepstakes. Lions often back off from herds of cape buffalo that stand and fight. Crows mob and drive off eagles. Sea lions will mob and harass great white sharks. And King's Skinks drive off venomous snakes.


Here I depicted a phalanx ( I am just going to start using that term instead of pod and hope it catches on, thanks Bk Jeong) of indeterminate Microcleidus sp. facing down and nipping at an intrepid Rhomaleosaurus sp. As you can see any headlong rush into such a group is going be a painful experience with no guarantee of capture. Furthermore, like herons when cornered and unable to fly, there is no reason that plesiosaurs could not have targeted the eyes of would be assailants. And when visually dependent predators lose an eye, not a good thing. Plesiosaurs were most vulnerable from the rear and you will notice I gave their stumpy, skink like tails eye spots. Furthermore the very solid and almost carapace like constuction of plesiosaur torsoes offered additional protection from rearward attacks. Microcleidus is a pretty cool but seldom discussed plesisoaur. It was basically an elasmosaur before it was cool to be an elasmosaur. Only about 3-4 meters long it had an exceptionally elongate neck, small head, but that head and jaw was nasty.

Microcleidus from Brown, Vincent, Bardett 2013

And below I depicted some more well known characters - a generic elasmosaur type plesiosaur family faces down a generic mosasaur stalking one of the youngsters.


As I went over in my last post, Introducing the Plesiosaur Phalanx Attack, a strong social adaptation in plesiosaurs offers a compelling foraging strategy. And such a social framework also offers a strong defensive strategy. Furthermore, by invoking this defensive adaptation a lot of the problems in plesiosaur anatomy that suggest high vulnerability to predation - long vulnerable neck, low maneuverability, low swimming speed - are squashed. The neck and head are not the most vulnerable spots in this scenario but instead the torso, rear flippers, and tail are. A large, plump tail would serve as a dispensable organ and may have been covered in eye spots or even shed (highly speculative?!?) to distract predators like many modern lizards. And the torso is heavily reinforced with a bony wall of ribs, gastralia, shoulder and pelvic girdles. Instead of a paradoxical animal, vulnerable on all levels to predation, seemingly outside the bounds of Darwinian evolution - a much more dynamic, capable, and combative animal emerges.

In short, a rare example, where the early artists got much more right in some regards than contemporary artists.

Édouard Riou from the 1867 edition of "Journey to the Center of the Earth"
































Sunday, December 7, 2014

Plesiosaur Machinations I: Introducing the Plesiosaur Phalanx Attack

Machination: a scheming or crafty action or artful design intended to accomplish some usually evil end.

Ok no talk of that movie, or Spinosaurus cuz it gets everyone including myself into a tizzy - no let's talk about something nice and non-controversial: plesiosaur feeding ecology. That is a pretty hum-drum topic no?

Of course your sarcasm detector should be buzzing and plesiosaur (for our purposes here just assume I am referring to the long necked variety when I say plesiosaur so I don't have to say "plesiosauromorph plesiosaurs" every time, ok) feeding ecology is just one of those topics in paleontology that continues to stifle us. And with such a strange and unparalleled morphology there are no shortage of foraging techniques, and otherwise, that have been suggest for dat neck. Adam S. Smith has compiled a good overview of many of these, check it out at your one stop shop for all things plesiosaurian: The Plesiosaur Directory. And hey, it included my twist feeding idea (not just for ammonites though but for any carcass, scavenged or otherwise, too large to swallow), among others. Now in this post I am not going to focus on twist feeding but actually incorporate that style of foraging - with several others listed there - into a more holistic interpretation of plesiosaur feeding ecology.

Before we begin - some qualifiers. Plesiosaurs were not as "samey" as often portrayed. Some were possibly straining small food particles out of the water column or substrate; some were equipped with especially heavy bones that may have allowed specialization on bottom foraging; some had extremely long, almost comical necks and some had necks that were rather conservative. I would argue further that what we are really seeing is a spectrum of species ranging from the plesiosauromorph bauplan to the pliosauromorph bauplan. Guys like Rhomaleosaurus (pictured below) traditionally called a pliosaur, actually fit nicely between the two extremes. Although big headed, it also has a long neck, especially by todays standards. So keep in mind that some species may have varied quite a bit from the picture I am going to paint depending on neck, teeth, skull etc. etc.

Rhomaleosaurus. A "pliosaur" yes, but still pretty "necky". wiki. Niki Odolphie
And in my last post on plesiosaurs - Thus Spoke Zarafasaura (catch my clever literary nod to Nietzsche there) - I discussed an elasmosaurid, Zarafasaura oceanis,  that may have been punching a little bit above it's weight - or at least was showing showing some skull/skeletal adaptations geared towards more rigorous feeding activities beyond the usual "gape limited, small fish only" dogma that dominates plesiosaur feeding ecological interpretations. I mean would you really be confident enough to go for a swim next to this guy? Are you so very sure it was "only a threat to small fish and squid"?

Zarafasaura oceanis
But hold your judgement for now as to whether or not some plesiosaurs were maybe biting into bigger stuff than generally portrayed, hopefully I can sway you later. I want to reiterate and restate a theme I brought up on that post about Zarafasaura which will also be at play in this and future posts on plesiosaurs. And that is, unlike the case with many popular and idiosyncratic prehistoric animals, I am going to argue that the earlier popular reconstructions of plesiosaurs captured their essence a lot more precisely than more current plesiosaur depictions. Now I am not talking about the S-shaped snake like neck here, or lifting the heavy neck swan like out of the water - I am not suggesting those physical feats are possible. I am talking about the portrayal - especially in those early gothic, black and white murals - that speak to a creature, while not immune from predation, was still willing and able to go to toe to toe (err flipper to flipper?) and dish it out against the other bad asses of the seas. Not a creature whose long neck was a liability and and made it a veritable punching bag to other bigger mouthed-stronger jawed creatures of the sea but a pugnacious, dynamic, and extremely well equipped and adapted marine tetrapod that could hold it's own.

In short more like this:

Thomas Hawkins' "Demonic Plesiosaur Battling Other Sea Monsters (Temnodontosaurus) in Eternal Darkness" 

And less like this:

Dmitry Bogdanov. wiki
Now of course you are probably thinking about all the abundant evidence of plesiosaurs being bit due to pliosaur attacks, mosasaurs etc etc., which is true - they did fall prey to other animals. But I want you to focus on the composition of the two paintings. Both feature two plesiosaurs. In the Hawkins rendition we see the plesiosaurs put up a united front against a possible predator while  in the Bogdanov painting we see one plesiosaur getting rag-dolled and bitten in that "oh so vulnerable" neck while his buddy high tails it out of there. Now I am gonna let you muse on that difference and consider why I think the top picture is more accurate and I will come back to plesiosaur defense strategy in a later post. But it should definitely be emphasized that the way prehistoric animals are depicted plays a profound role in how the debate is framed around these animals, both professionally and to more lay audiences. This can not be understated.

Today's post is on foraging strategy. In order to do so I have to put the cart ahead of the horse a bit here. I am assuming a high level of social unity and group foraging in these sauropterygians. I will address why this is a very defensible position to take with these creatures in a later post and I am sure some of you already know why I am making this general assumption. But for now please allow a little bit of "suspension of disbelief" if you are a doubter.

Of course asserting "group foraging" is a veritable land mine in paleo-interpretation. Let me qualify this a bit. I want to draw a distinct line between cooperative hunting emphasizing a high division of labor, foresight, and usually associated with high intelligence - the kind seen in humans, chimps, wolves, and killer whales and a more of "mob" foraging strategy which I favor for plesiosaurs. Like looters in a riot each individual is acting on their own selfish best interests but have learned that their rate of capture increases when moving and foraging together as a group. This method of feeding is well known in various birds, fish, and sharks and I see no reason that plesiosaurs, though likely limited intellectually, could not have fit into this model. Of course if you have been paying attention we are in the midst of a bit of a revolution when it comes to reptilian intellect and social behavior - planning, social strategy, tool use, and dare we say emotion - so the door might still be open for truly cooperative behavior in plesiosaurs. But for now I am going to take the more cautious approach and invoke the "mob - looters in a riot" model.

And to prime you I want to draw your attention to two examples of group foraging that offer much utility here, white pelicans and white-tip reef sharks.


Now the videos, by Jack Polanen (please like, subscribe, and leave a comment not enough views of these awesome clips),  above and below are highly demonstrative of the efficacy of leaderless, opportunistic group foraging of white-tipped reef sharks (Triaenodon obesus). I will forewarn you it gets pretty graphic and violent at the end of the top video but I would encourage you to watch it all the way through. One thing I would hope you pay attention to: it is often not the first shark to find and/or flush a fish out of hiding that gets it, it is the second or third shark that opportunistically grabs the harried fish. This is an important point that will be revisited later. But it becomes obvious that as a whole this style of foraging creates more opportunity and better efficiency than foraging alone.


And now for another video, again via youtube and from an amateur birder/wildlife documentarian  Michael Descamps, which depicts a quite large congregation of American white pelicans (Pelecanus erythrorynchos) group foraging at the Nygren wetlands preserve in Rockton, Illinois. Like the white-tipped reef shark videos above there is so much here to look at and find visually stunning. Amidst the action it is sometimes hard to pick out individual feeding events but Descamps does a good job of slowing down the video at times and narrating the events. He even took the time to note a frog seeking refuge from the feeding swarm. Again not enough views (something this cool should have more views than the "gangnam style" video lolz) so please watch, like, comment, and subscribe to his videos. Link below pic, for some reason blogger will not link direct to this video ?!?

Michael Descamps (c)

Also, on white pelicans check out the video below of a pretty impressive swallowing feet of a quite large fish by a bird at the same locality by Michael Descamps:


And if you are further intrigued by pelicans check out this amazing video below of how Australian pelicans (Pelecanus conspicillatus) utilize the arid interior of Australia. Highly recommended but a little longer.


Ok now that you have brushed up a bit with group foraging techniques among white pelicans and white tip reef sharks (in actuality I could have went further with loads of examples, especially among fish) before we get to the plesiosaur bit one final rejoinder per popular plesiosaur depictions and the constant push/pull of science/art/opinion. Go google plesiosaur pictures. Ok did you do it? Now among the depictions you are looking at how many show the plesiosaur swimming in a horizontal plane? Most if not all of them, right?

Well here I am going to depart from that convention and suggest that, when group foraging in the water column a vertical orientation was the dominant swimming position. By assuming a vertical orientation this would minimize the likelihood of prey detecting plesiosaurs visually and through  pressure waves when attacking from below; and minimize the chance of detection via casting a shadow when approaching from above. The vertically orientated eyes would naturally align to target prey in this position and allow the head maximum chance of getting in biting range without being detected.



And now without further ado and because a picture is worth a thousand words blah, blah, blah: Introducing the Plesiosaur Phalanx Attack!!


Above I depicted a foraging group of Hydrotherosaurus alexandrae from the Maastrichtian of what is now Fresno, California (being a Cali boy gots to rep) but what was then ocean. Much in the way the military phalanx could crush an enemies defense, the plesiosaur phalanx attack offered little recompense to prey in its sight. The plesiosaurs are rising, silently, cryptically, and slowly from the depths and picking off small cephalopods and fish as they move up the water column. If a prey item is detected the plesiosaur begins a slow, stealthy approach. If the first strike fails and the prey evades capture it is not out of the woods yet as the next nearest plesiosaur swoops its neck and head in to snatch it right up. If that second plesiosaur misses and the poor prey item in question manages to evade it there might still be a third plesiosaur attracted to the commotion which targets said prey. Small fish, crustaceans, and cephalopods could likely move quick enough to evade the first and even second strikes - but facing a full phalanx of lunging plesiosaurs they would quickly tire and be snatched up. Again very similar to the situation with the white tip reef sharks I discussed above.  In this manner we can see how the neck of the plesiosaur - while not snake like per se - offers much utility in terms of covering a wide arc lunging ventrally, dorsally, and laterally after available feeding opportunities and leaving prey little chance of escape.

Range of motion as estimated by Zammit et. al. illustrated & used w/permission via Adam S. Smith

The mesopelagic critters I depicted are putative members of the "deep scattering layer", so named because when this biological phenomena was discovered using by sonar during World War II sound would literally bounce, or scatter, off of the dense accumulation of life that congregated at around 300-500 meters below the surface creating essentially a "phantom bottom". Of course every evening, when the largest biological migration on earth occurs - the vertical migration - this deep scattering layer would   disappear as multitudes of creatures seeking refuge in the depth from predators, temperature, and likely other factors rise to the surface at night and then return again in the morning.

So yes, I do imagine that a number of plesiosaurs, especially many elasmosaurids, took advantage of foraging in a phalanx formation on this bountiful and dependable food source. It is worth noting that the famed western interior seaway, a shallow continental ocean usually suggested to be about 100 meters deep, is noted for a sparsity of elasmosaurid plesiosaurs. However once you get off the west coast of North America, where you find deeper, colder and possibly more productive oceans (and a deep scattering layer presumably) - the amount of elasmosaurid plesiosaurs goes up in numbers and diversity. Robert Bakker noted this in his book Dinosaur Heresies on page 430. Furthermore there is a detailed study on evidence of decompression syndrome i.e. "the bends" across sauropterygia. What did they find? Avascualar necrosis was found across all families but significantly lower in cryptoclydids. Best known for the species Cryptoclidus eurymerus (that wikipedia page has got to be changed, 8 tons I think not) and also famously featured in the original Walking With Dinosaurs, these beasts were likely near shore hunters of small prey and even infaunal sifting has been suggested. They are a bit of an outlier with regards to most plesiosaurs with weak lower jaws, small meshing teeth, and a fairly conservative neck.

Just compare the top pic, Cryptoclidus (Brown, 1981) to my boy,  Hydrotherosaurus bottom pic (Weles, 1943) both pics used courtesy of Adam Stuart and from the Plesiosaur Directory.



Now, even just looking at these skulls and giving them the eye test it is readily observable that there are some differences. The Hydrotherosaurus skull just looks more battle ready; longer, larger and more heterodont dentition; relatively larger temporal muscle site; a deeper lower mandible; stronger symphyseal union. If plesiosaurs were all supposedly "gape limited predators, a threat to nothing larger than a small fish or squid" why such divergence if they were all so limited in prey choice? The answer of course is that in my view they were not so limited in prey choice and carcass utilization as generally presumed. If we invoke a group foraging strategy then I think that definitely ups the ante in terms of what these guys might have been biting into... how big? Well let me put it to you this way: personally I would not feel comfortable with swimming with a Hydrotherosaurus or even a Cryptoclidus - alone or in a group. An eighteen inch head is still an eighteen inch head. And even in supposedly fish eating pinnipeds it has become increasingly apparent that they do engage in tackling quite large prey items. If a plesiosaur locked onto you and you yank away, you are leaving something behind.  I have kept too many diapsid pets that I know if they think that they can overpower you and get you in their belly, by hook or crook, that they are going to try and do so. Take that as you will.

To familiarize with what a much smaller, shorter, weaker toothed, and weaker jawed "small prey specialist" can do with its chompers check out these moray eel pics/videos.


Now the video above has been making the rounds for a bit now but it goes to show the impressive way a moray can utilize its body and jaws to subdue a small white tip reef shark. The video below is actually more interesting and startling actually - you might want to skip to about the 2:10 mark where a large green moray disturbs a lobster which seems to jump out of the water and never reappears (?!), and then the moray just charges the diver and does a small nip, but not really a dedicated bite per se. Did the moray see the human as possible predator? competitor? Startling video none the less.



Another scary video (below) about a diver who habituated a green moray (Gymnothorax tunebris) to feed off of little sausages. Unfortunately the eel mistook the divers thumb for a sausage and off went the thumb!! On the bright side at least the diver was not skinny dipping!!


For me there is little doubt that a 13 meter long, several ton plesiosaur - with a much heavier and stronger frame to spin off of - could do much more damage than 2 meter long moray eels. Just in case you are not convinced just look (graphic warning) at the bone scraping damage a green moray can incur on a humans arm. My point is not to shock with these clips but show that an animal with non-serrated, fish catching jaws can still do a good number on larger sized items.

And that's a-moray... eel skull. Looks vaguely plesiosaur like no?


Ok small digression there, just trying to chip away at the notion that all plesiosaurs did was bite into small stuff. Let's get back to deep diving plesiosaurs. And I think it worth mentioning that there are still loads of questions regarding how deep diving modern predators, especially air breathing tetrapods, work and operate at such depths. Never mind the fact that the sperm whale, an animal whole industries were founded upon, is still a huge mystery. Forgetting about the good old cachelot, let me point you in the direction of an interesting study of short-finned pilot whales (Globicephala macrorynchus) which contrasts their foraging ecology with that of the various species of beaked whales that they share deep sea habitat with off the Canary islands. Full paper here.

Short-finned Pilot Whale w/large squid tentacle. (c) Pablo Aspas
Their research on short-finned whales, which they dubbed "the cheetahs of the deep", points to an "all or nothing" foraging strategy of rapid and vigorous dives of 20 minutes or less in search of, evidently, fairly large cepahalopod prey including Architeuthis dux - the giant squid. These high energy and oxygen consuming dives are presumed to be the reason this species, when observed on the surface, are observed to be quite sedate and approachable - they are recovering from stressful and often unsuccessful deep sea pursuits of large cephalopods. Beaked whales, on the other hand, move and pursue prey at a more leisurely pace in their dives and generally, as the authors suggest, are "berry pickers" using suction to capture numerous smaller prey items through out the water column all the way to the sea-floor. This difference in foraging technique offers a suggestion of resource partitioning and also adds insight into why so little is known on beaked whales and why they are so rarely observed at the surface. Their more leisurely foraging technique, allows them to remain underwater longer and spend less time on the surface than short-finned pilot whales.

In comparing these two deep diving foraging strategies with regards to plesiosaurs I definitely would hedge more towards the "berry picking" of small prey and slow and leisurely foraging style of beaked whales than the "all or nothing" style of short-finned pilot whales. In plesiosarus the cryptic head at the end of a long neck allowed stealthy approach and lack of high velocity swimming/maneuvering capability further speak to beaked whales as a better analog than short-finned pilots - at least among the plesiosaurs that habitually dove into the mesopelagic/abyssal realms after prey. Of course I also think that such plesiosaurs, although having a predilection for small prey - would have opportunistically taken medium sized prey/scavenged carcasses as well. Let's look at a family of deep diving predators, that emphasizes cryptic, stealthy predation to the nth degree and which opportunistically catch prey from the abyssal realm all the way to shallow water - sharks of the genus Somniosus of the dogfish family - Squaliformes.

Video above really highlights the "blob of jelly" aspect of Sleeper sharks. Cook Inlet, Alaska.

Somnio: "a dream, sleepy". Sharks of the genus Somniosus, which may compete with the great white shark for title of largest extant predatory fish, are truly creatures out of a dream - or, more precisely, a nightmare. The Greenland shark (Somniosus microcephalus) holds the title of the world's slowest swimming fish (when corrected for size). Paradoxically there is evidence that this shark hunts and catches several species of seal as well as numerous fast, bony fish. It has increasingly become apparent that the slow cruising speed allows this shark to approach undetected towards sleeping or resting marine mammals and fish. The Greenland shark and other sharks of this genus occupy a unique niche of an exceptionally long lived - low metabolism, cryptic, slow cruising, opportunistic predator of a wide variety of prey types and sizes from throughout the water column. More detailed studies of the closely related Pacific sleeper shark (Somniosus pacificus) by the Alaskan Department of Fish and Game further support this adaptation. Investigating whether a marked increase in Pacific sleeper shark population was responsible for Stellar sea lion declines the researchers performed stomach analysis and PAT tagging work revealed a conspicuously wide ranging and catholic predator.

Pacific Sleeper Shark. wiki
Researcher Lee Hulbert found that far from being a deep water specialist the Pacific sleeper shark stayed below  the photic zone during the day and moved into shallower waters during the night when its dark color and silent approach with minimal hydrodynamic disturbance allowed it to approach prey including rockfish, pollock, salmon, flounder, halibut, cod, and marine mammal including harbor seal and whale - either predated or scavenged. The sharks moved in constant vertical oscillating patterns, averaging 6 km a day. Concerning their movements Lee said, "These sharks never stop moving. One of  them logged 12,000 vertical meters in 24 hours. The guys at Wildlife Computers had never seen anything like it from any animal."

All right so I think, in a necessarily piece meal fashion, many plesiosaurs that foraged in the open ocean would fit nicely somewhere between the "cherry picking" leisurely foraging of beaked whales and the slow, cryptic, vertically oscillating, and opportunistic foraging of sharks belonging to the genus Somniosus. Combined with the group foraging strategy outlined above, moving in a vertically orientated matter to further hide the body and diminish hydrodynamic disturbance, and the benefits of a long neck to cover a large feeding envelope and, for me, this is a pretty diabolically efficient foraging adaptation. As I mentioned at the beginning of this post plesiosaurs certainly were more diverse than usually portrayed and several specialized in shallow water/lagoonal settings (Crypotclydidae and Leptocleididae come to mind) and some potentially engaged in lots of benthic, demersal foraging similar to what the white tipped reef sharks were doing. But in all cases; deep water, shallow water, or sea bottom foraging or any combination there of - a cryptic approach combined with the benefits of group foraging and the unique physical proportions of plesiosaurs suggest a very successful foraging adaptation.

Anyways hope you stayed with me for the whole post. I know it was a little all over the place but with a difficult group of critters with no exact analogues it has to be a little chaotic and piece meal. Maybe you are not swayed with the idea of some plesiosaurs biting into bigger stuff than generally presumed or you think the whole group foraging hypothesis is a little too tenuous and speculative. And as many have noted the preserved stomach contents point towards small stuff. I want to explore this further in future posts but let me suggest that there can be fossil bias in stomach contents as well. If plesiosaurs are assiduously avoiding large bones due to obvious choking hazards and flesh does not fossilize (as well) we simply won't see evidence of larger animals in their diet. We now know from field observations that pinnipeds will kill good size cetaceans and sharks and strip high energy blubber and liver off of these respective animals. Yet the majority of their diet is small stuff. If these animals were fossilized there likely would be no evidence of these episodic moments. I will revisit these topics in future posts and hopefully can sway you.





Friday, November 28, 2014

Calm Down, Breathe, ... OK Repeat: It Is Only a Movie, It Is Only A Movie.....

I really did not want to write about the movie which, I mean you know what movie I am talking about, had a very early debut commercial this weekend. The fourth installment in a certain iconic franchise. Yes that movie. Anyways, although it was already known said starring characters would not be feathered, the backlash in the paleo/dino blogosphere was very palpable indeed. And then swiftly followed by a larger backlash against said backlash promoted and promulgated by the more general public at large against dino-buffs with indictments of "nerd rage" shot fourth.  Shots were indeed fired.

My point in writing this is not to pick sides but to add a little bit more context, reason, and nuance to the  general debate.

Before I do this I also think it worth reminding ourselves (political rant warning) there were a lot more interesting and profound things going on in the world this week than the trailer I speak of. At least here in America Ferguson should trump "bunny hands" in terms of relative importance. If you spend a lot of time thinking about, musing upon, blogging about, drawing, and theorizing about dinosaurs and other paleo related stuff just remind yourself that you are in a privileged position. Chances are if you are reading this you are white, male, and come from a relatively stable socio-economic background. You can dedicate a lot of mental energy to this stuff because you are not so preoccupied with getting shot due to the color of your skin or worrying about getting sexually assaulted or street harassed due to your gender.  You yourself might be poor, but more on that later...

Point #1 The Jurassic Park franchise was fictional from the start and willfully ignored the best available science from the get go.

I forgot where I read this or who said this (let me know in the comments) but to paraphrase "The first Jurassic Park felt like a love letter to paleontology and this new movie feels like a middle finger". While I will agree that the first Jurassic Park movie allowed the general public to play catch up to a lot of current thought in dinosaur paleontology - intelligent behavior, horizontal posture, advanced metabolic strategy, active lifestyle - it outright ignored some of the others and made plenty of stuff up. For example, the exquisitely preserved fossil Velociraptor, the supposed "cheetah speed" and "primate level intelligence" of raptors, a bipedally rearing Brachiosaurus  (not impossible but more likely for diplodocids), the enlarged size of Velociraptor (Utahraptor was not known when the decision was made to blow them up), and cobra spitting Dilophosaurus.

My point is this movie franchise set a precedent from it's inception to utilize some of the current science, ignore other bits, and completely make stuff up as was felt fit. Because it is a movie made to make money. Let us not deify, or glamorize the original movie - it is not without sin in these regards of scientific accuracy.

Point #2 There likely was a push to update the dinosaurs in JP$$$4. But money, and public opinion, and story continuity.

Just because your film has scientific advisors, does not mean that their advice will be listened to. If money is involved and the choice between making more money versus less money involves picking the non-scientific route, the non-scientific route will be chosen. Not because I agree, but because that is how the Hollywood machine works.

Here is how I think it likely went down in the boardroom meetings:

Scientific Advisor/Creative Type People: "We think updating the dinosaurs with feathers and diverse integumentary structures to reflect current knowledge of these animals will create a smart, edgy, new, and scientifically accurate film. We can not only add to the legacy of this franchise in this manner but jump start a new era in the Jurassic Park saga."

$ People: "While the board respects and appreciates your suggestions our in depth customer surveys finds that the general public at large still finds scaly dinosaurs more "scary" and "monstrous" and finds "feathery" dinosaurs more cute and less threatening. So, although we have taken your suggestions into consideration, we will keep the narrative of the first three films intact in terms of how these animals are depicted. As a bit of a compromise, our independent consultants have suggested a type of bio-engineered ubersaur. Fast, quick, smart, insatiable killing appetite. You paleo folks should love it because you love monsters anyways, am I right? Yeah we can sprinkle some dread lock looking stuff on that guy. White people are scared of dread locks too our surveys show."

Scientific Adivisor/Creative Type People: "We challenge this notion that you have to dumb down the franchise in order to appeal to a lowest common denominator. Many of the most iconic and celebrated movies of all time took risks and were intellectually challenging. For instance 2001: A Space Odyssey, Alien...

$ People: "Frog DNA."

Scientific Advisor: "We think you are missing a great opportunity. Hear me..."

$ People: "Thank you that is all. Frog DNA."

Advisors: "But!!!-"

$ People: "Frog. D. N. A."

Door slams shut.

Point #3 How to Talk to Non-Paleo People About Dinos Without Coming Off Like a Pompous Blowhard

This might be a tough pill for many to swallow but the average person does not care about dinosaurs or paleo related stuff at the level that you do or even at all. And they have a right to not care about 'em. You might feel very passionate about dinosaur socio-ecology or hadrosaur growth rates - but it is not your duty to promulgate this info to everyone in your life. In fact by aggressively espousing your knowledge and/or opinions on said subject matter you might be doing more harm than good to your social life and in fact turning them off to scientifically minded people in general.

Let us imagine a dinosaur buff is lucky enough to be on a date to see the Jurassic Park 4. First of all, if the decision to see JP4 is made by the date or concurrently at this point I would say it is ok to let the date know your background on the subject. But do it softly. Hey, if they are meant to be the one it is ok to let them know what you are passionate about.

Example: "I am actually a bit of a dinosaur fan myself. In fact, my interest in the subject has continued since childhood."
(Somehow or another this post turned into dating advise for paleo-nerds but this could apply to all social interactions.)

If your date says "Me too!!" count yourself lucky and continue forth in a measured pace. If your date does not mirror your interest. Shut up about Dinos (this is crucial).

During the film, and this might be excruciatingly hard to do, do not guffaw, roll your eyes, and make sardonic remarks at every scientific inaccuracy you see. If you are among like-minded friends go right ahead.

And finally after the movie is done do not go into an unsolicited diatribe concerning the plethora of errors you meticulously noted in your head. If your date petitions you for your opinion regarding the film and/or its inaccuracies feel ok to go forward in a measured pace but not overly opinionated. At the first sign of disinterest, glazed over expression, or exasperated stare, and this is important, SHUT THE FUCK UP ABOUT DINOSAURS!!!

Look, just because your date does not share your passion for dinosaurs (and chances are they will not), does not mean you should lose out on a potential partner.

Point #4 Why You Should Righteously Be Mad At JP$$$4

If you want to really have some fire in your belly, if you want to really speak truth to power, if you really want to punch upwards - this is why you should righteously be mad at JP$$$4: Because the  work and efforts of many people in or surrounding the field of paleontology - who did the work for little or no pay - is being appropriated, bastardized, plagiarized, and commodified with little or no recompense to said field by a film and franchise that will likely make (and has made) billions of dollars. Where is the funding that the Jurassic Park franchise could and should be giving back to paleontology and/or biological sciences in general? Just a small slice of the money that this franchise generates could support paleontological digs the world over. For a film franchise that owes so much to paleontological discoveries - whether they used the info correctly or not is not so important - where is the slightest bit of  financial recompense to the field that even allows such a franchise to exist at all?

And finally I quote from the first movie Dr. Ian Malcolm:

"You didn't earn the knowledge for yourselves, so you don't take any responsibilities for it. You stood on the shoulders of geniuses to accomplish something as fast as you could, and before you even knew what you had, you patented it, and packaged it, and slapped it on a plastic lunchbox and now, and now your selling it, you want to sell it. Well -"....

And finally a dreamy shot of Dr. Ian Malcolm and a rigorously rendered Tyrannosaurus rex:



Buy it here @Jim'll Paint It








Monday, November 17, 2014

Redwood Grove Along the Big Sur Coast: Southern Limits

The magnificent coastal redwood (Sequoia sempervirens) - tallest organism in the world - is most closely associated with inhabiting a narrow coastal strip in northern California, the redwood belt. This narrow strip of habitat provides the necessary moisture via incoming pacific storms (some areas here receive up to 100 inches of precipitation) and, more important arguably, persistent fog especially during the summer months. Due to a strong Mediterranean climate regime summer months in California  are essentially dry, but along the coastal strip enough moisture arrives via fog that these stately behemoths are able to minimize evapotranspiration and literally "intercept" moisture out of the air from fog.  It has become apparent that by adding significant moisture into their ecosystem redwoods are not only benefiting themselves but providing water to the other plants and animals in their community (some contend up to 1/3 of all water is from fog collection in these systems), even to the point of adding enough groundwater into the system that streams that may normally be ephemeral run year round.

Scott Catron. Redwood National Park. wiki

But I want to look at the redwoods existing on the southern fringes of their range as I have a special interest in organisms living at their absolute limits. The redwoods of Big Sur in Monterey county are the most southerly occurring natural redwood groves, are genetically distinct from populations north of the San Francisco Bay, and the most imperiled population due to climate change. It is here on the Big Sur coast, a land of extremes, where one can literally see cacti growing in close proximity to redwoods.



Never mind the invasive pampas grass, what should be apparent from this photo I took of one of most southerly stands of redwoods is that you can plainly see the juxtaposition of drought tolerant chaparral vegetation against water loving redwoods. These southern groves of redwoods do not carpet the entire landscape but are restricted to deep ravines and gullies that lie adjacent to the ocean. This population is within several hundred meters of the ocean and just off of highway 1.



As I mentioned earlier these southern populations of redwoods along the Big Sur coast are not only interesting in that they represent redwoods at the southern limit of their range but they also are genetically distinct from northern populations. Why would these populations of redwoods at the extreme limit of their range be genetically distinct from their northern counterparts? Good question and I am glad you asked. And the answer is basically genetic drift. Isolated from other neighboring populations by severe canyon topography and by populations up north by larger geographic features these isolated populations have each nonetheless adapted to the unique conditions that they find themselves in. Adapted to surviving on less fog and precipitation and higher temperatures than their northern counterparts they offer an interesting study in relictual pleistocene populations facing a warming climate. It has been established that redwoods used to extend much further south in the Pleistocene, at least to Santa Barbara county - if not all the way to Los Angeles (according to wiki so take it with a grain of salt). One can also make a broad comparison to southern steelhead trout in California and their interesting genetic legacy.

Their genetic potential of these southern redwoods, little studied and perhaps even more diverse than northern populations, may be of some utility if northern populations suffer due to climate change.





Of course redwoods are of some interest to me, and hopefully to you, as trees perhaps not too dissimilar have a long geologic history going back well into the Mesozoic. Indeed many dinosaur scenes feature a substantial use of redwood like foliage as a backdrop to herds of dinosaurs. Here is a good review of redwood prehistory, also check out the diagram below.


How accurate are scenes of gigantic redwood groves in Mesozoic dioramas? In light of the fossil record and the substantial similarity of form between living and extinct Sequoia I seen no issue with using redwoods as a model for many Mesozoic forests (although these scenes should be limited to northern latitudes and not equatorial latitudes which were likely too hot and dry i.e. don't put redwoods behind your Spinosaurus).  What is probably a better model for Mesozoic forests is the dawn redwood (Metasequoia sp.) a true deciduous conifer. But redwoods are fine... The question that arises in my mind is how did Mesozoic redwoods, with their substantial water needs, make due in an often arid and seasonal climatic regime? Did they persist as primarily riparian species, sipping from underground water tables? Were they substantially shorter in stature? Were they adapted to harvest water from the fog like modern redwoods do on the coast? As I discussed earlier the precipitation of the Big Sur coast - about 40 inches coming primarily in the fall and winter - is paltry compared to the upwards of 100 inches that other populations receive. Coastal fog is the difference.

On the Big Sur coast deep and cold submarine canyons bring cold waters to the surface which creates abundant fog when warm moist air blows over it. Mesozoic oceans were a lot warmer and shallower due to rising up onto the continent, so I really wonder if fog was consistent enough that Mesozoic redwoods sipped water from oceanic fog? Then again maybe they did in more higher latitudes where a stronger differential between ocean and air temperatures may have fostered consistent fog. Who knows, I don't know if anyone has seriously investigated how relatively frequently fog may have occurred in the Mesozoic. Fog occurs in inland areas too...


The Big Sur coast is definitely a worthwhile trip for anyone who lives in or is visiting California. Give yourself at least a day to do it as you will be pulling off the road to photograph scenes like the one above on the reg. Or battling immature male elephant seals during the molt readying their musculoskeletal systems for doing battle at 1 g...





On a wider note the Big Sur ecoregion is notable for harboring the largest extant predatory fish (the great white shark), the largest bony fish (Mola mola), the largest animal of all time (the blue whale), the second largest carnivoran of all time (northern elephant seal), the fastest growing and largest alga known (giant kelp), the second biggest wing-spanned terrestrial bird (California condor), the largest extant mustelid (sea otter), the largest extant sea turtle (leatherback sea turtle), the second most massive and tallest tree (coastal redwood), and, until recently, the largest extant terrestrial predator (grizzly bear).

And, oh yeah, the second largest extant terrestrial slug (go banana slugs!!!).

Eat your heart out Texas.

author. Jedidiah State Park.

Cheers!!






Friday, November 7, 2014

Time For the Giant Heron Spinosaurid Analogy to Bite the Dust Part 2: Getting More Than Just Your Feet Wet

Now first things first I want to clarify why I am writing these posts and how dealing with spinosaurid paleobiology is a veritable land mine. In my last post I echoed the sentiment of a poster for #2014SVP (Anduza, Danny Museum of the Rockies) that the wading "heron" analogy is not the best analogy of all possible tetrapod analogies for spinosaurids. As Dr. Thomas Holtz pointed out in the comments this is a "strawman argument" because no one has seriously suggested that spinosaurids hunted in the manner of herons which rely on a rapid acceleration of a sigmoidally orientated head and neck after visual detection of prey. And this is true: it is well known that spinosaurids had overall straighter and stiffer necks than let's say a fairly basal theropod like Coelophysis. Where the heron analogy works is that it provides a blueprint for an animal that wades in after prey. 

However, and this is a big however, spinosaurids - perhaps more than any other group of extinct animals save tyrannosaurids - lie squarely at the intersection of public and professional interest and interpretation. We saw this very interesting phenomena just occur - #Spinogate2014 - that illuminated an interesting socio-scientific-internet experiment. A radical new stance for Spinosaurus asserted, questions raised and doubt sown on the internet, and a very loud and vocal internet cadre of anti-Ibrahim et. al.  proponents sallied forth. In fairness some of the Ibrahim et. al. critics are acting in good accordance with sound scientific scepticism and legitimate concerns. But one can not deny that a social aspect - bipedal loyalists, "bipedalists" if you will - are really hellbent on keeping the JP3 Spinosaur alive and well. And continue to do so even after Ibrahim et. al. discounted the criticisms.

But this post is not about Spinosaurus or Spinogate it is about how an analogy for the group as a whole - the "giant heron" model - has been seized upon by the lay public as a point of reference for the group to the point where, I will argue, the "heron" model is providing a disservice. And the manner in which the "heron analogy' has gone too far is not wholly from paleontologists - but from how these animals are portrayed in artistic and especially video reconstructions. Unfortunately even though the "heron" analogy was useful in the broadest sense, popular reconstructions have run rampant with the "giant heron" model dominating. This is a hindrance.

Spinosaurus (c) BBC
Spinosaurus (c) Todd Marshall
Baronyx (c) Mark Witton
 Suchomimus w/Kryptops (c) Julius Csotonyi
As you can see in these assorted and very beautifully rendered pictures of various spinosaurids there are echoes of the "giant heron" analogy in all of them. In none of the pictures do we see the spinosaurid body largely submerged. The BBC pic and the Witton pic (btw check out Witton's great deal on art, remember the holidays are coming and we should support independent paleo projects) suggest an emphasis on visual detection a la herons.  But the lack of strong adaptation for binocular vision and emphasis on sensory pits speak against this. Unfortunately even the new NOVA doc on Spinosaurus depicts it fishing heron style.  The Marshall pic shows the Spinosaurus taking advantage of its sensory pits but the choice of putting the animal on the bank of the water instead of in the water speak to a larger problem in spinosaurid reconstruction - A PERVASIVE FEAR OF GETTING WET. The Csotonyi illustration is awesome, but again conservative in term of water depth (book here).


Seriously, for a group of animals that we can say exploited aquatic resources with strong confidence, there is a strong reluctance to actually put the whole animal in the water (where its sensory adaptations and foraging options make much more sense I will argue anyways). The above images have a profound impact on how these animals are imagined by laypeople and professionals alike. These representations that invoke the heron model to various degrees need to be dialed back a few degrees in my estimation. And here I want to provide some nuance to my argument. It is not that I am suggesting scenes like the above did not ever happen. That a spinosaurid, at one time during the long span of time such creatures existed, happened to be standing on a river bank and coincidentally a large fish just happened to swim by in shallow water and that the spinosaurid was able to lunge at it in a heron like manner and catch it - this most certainly happened. What I am suggesting is that the representation of such a moment and style of predation is disproportionate to the amount of time such a style of predation actually occurred. 

More Than One Way To Be A Wading Aquatic Predator

Grey Heron & Painted Stork Feeding (c) Lau SY
What do they say?... a picture is worth a thousand words. Above you see the very obvious difference in feeding between a wading grey heron and a painted stork. The heron relying on slow, cryptic stalking and the stork employing tactile feeding - sweeping its sensitive bill through the water and feeling out prey. Below is another video this time of a wood stork and various heron illuminating the different feeding strategies - also note that the wood stork will intentionally disturb the substrate to flush out prey.

                                     

Hopefully you probably figured out where I am going with this. Various wading storks that employ a tactile method of foraging with their sensitive jaws immersed in the water offer more utility as an analogy to spinosaurid foraging behavior than visually dependent herons. A slight shift in perspective is all I am suggesting. In light of their downward sloping profile, sensory pit equipped snout, and lack of binocular vision this view of spinosaurids highlighting a foraging behavior dependent on tactile foraging is of some use and should be taken into consideration for popular reconstructions of these animals. You can see that Marshall almost got it right in the picture above where he at least got the snout in the water, but he did not want to get the spinos feet wet. Sheesh just put the whole animal in water and it makes much more sense.

Which brings me to my next point, how deep of water to put these animals in. Anywhere on the spectrum of foraging in drying up pools all the way to completely submerged in my opinion. In light of the preponderance of illustrations/animations depicting them as seemingly limited to the shallows I am definitely for more depictions of them in deeper water. Even the new spino doc used this depiction of shallow water heron foraging. Furthermore, all things being equal, big fish are going to seek refuge in deeper water especially in predator rich environments. All these illustrations of spinosaurids in ankle deep water and a 200 pound lungfish or coelecanth just sort of nonchalantly offering itself up for grabs in the shallows.... yeah, I don't really buy it. Its insulting to fishdom and seemingly outside the bounds of Darwinian evolution. If fish are being predated upon fish will seek refuge in deeper water. And if you are a big spinosaurid trying to stalk a fish visually - if you can see it chances are it can see you and evade you. 

So how did a spinosaurid go about hunting in deeper waters? Well first and foremost for spinosaurids to be successful they want as many things in their advantage as possible. And that means murkiness. If you can't see me that means you might not swim away in time before my snout detects you. This might mean foraging at night, when fish although not "sleeping" do go into sort of rest phase and of course vision is limiting. Also many waters are naturally murky or turbid, especially in the tropics. Illustrations of normally murky tidal and tropical rivers intentionally clean things up a bit but that is simply an artifact of allowing the viewer to see what is under the water. Tides and storms can also disturb the water creating turbidity. Other animals, dinosaurs frolicking, and the large fish themselves rooting around in the mud will create turbid conditions. Remember the "river of giants" and also that lungfish are known feeders of benthic prey and are rooting around all the time. And then finally the spinosaurid itself; if conditions are just a little too clear; if prey is hiding in vegetation or in the mud; just use your big feet to stir things up a bit. Like a 10, 000 pound wood stork. After that it is just a matter of slowly cruising the water until your sensitive snout and/or gaff clawed hands bump into something tasty.  


Which is pretty much what I am trying to illustrate above where a Suchomimus tenerensis is intentionally stirring up the sediment in order to flush prey ( a poor lungfish of course) and cloak itself as well. Notice I draped loads of barbs or "whisker" type integument over the animal in order to make the whole animal sensitive all over. Hey why not, we are in a bit of an integument free for all for better or worse.

But I should also add that when fish were concentrated in drying, shallow pools or pushed through topographic bottlenecks due to tides, migrations, spawings any self respecting spinosaurid in the area is going to hone in on that area to forage as opposed to the method depicted above. But such confluences of events that make fish so easily scooped up are usually few and far between.

Marabou Stork w/trapped catfish (c) Jonathan & Angela Scott
I should also note that there are some artists that have begun depicting spinosaurids mostly or even completely submerged. Brian Engh's depiction comes to mind (in fairness this Spinosaurus was made before the new reconstruction). He also has got the arms and claws outstretched feeling for possible prey and increasing its feeding envelope. His depiction is suggestive of an animal dependent on tactile senses. Check out his awesome blog Don't Mess With Dinosaurs and remember it for the holidays because he has some pretty cool merch and we all need to support independent paleo/monster creations if we want more of 'em!!


*Update 11/8/14 Andrea Cau of Theropoda has also been beating the drum for putting more of spinosaurid anatomy immersed in the water. Anatomically citing a body design pitching forward and down - an anteroventrally inclined head partially immersed in the water has depicted in the below schematic. In the comments below Andrea informed me that Simone Maganuco brought up the "stork analogy" 5 years ago in a conversation - so credit where credit is due.



Why the "heron" model has dominated the view of these animals over others such as "storks" is a question worth asking. Maybe many view herons and storks as sort of "samey" while in fact their foraging method is quite dissimilar. It is worth speculating that dinosaur thought and concept is still largely dominated by North American and European peoples. Where, especially in America, there are a lot more visual orientated heron type aquatic waders than tactile stork type aquatic waders. I believe we pretty much just have the wood stork. Europe is known for storks but primarily they have white storks which often feed in wet meadows and fields as opposed to in the water. But go down to an east African river or spend a week on the Pantanal and you will see relatively more of all types of waders - but especially stork style tactile waders.

So in conclusion more "stork" and less "heron". But actually I like "storkodile" the best because it gives reference to the tooth studded jaws, large size, and opportunistic nature of these beasties. Eat your heart out Crocosaurus.


Cheers!!

Related Posts Plugin for WordPress, Blogger...