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!!

Sunday, November 2, 2014

Time For the Giant Heron Spinosaurid Analogy to Bite the Dust Part 1

More to come for sure in many future posts but I just wanted to leave this here: an abstract for the Berlin SVP meeting looking at Spinosaurid behavioral ecology through the lens of extant fish eating tetrapods. I concur with some thoughts - lack of a strong signal for heron type stalking - and disagree with other thoughts - the use of the claws for "pinning" prey against the substrate as their primary role.


Great Blue Heron. Fillmore Fish Hatchery by Author

Friday, October 24, 2014

Deinocheirus mirificus: Mad Dabbler of the Nemegt

In quick succession we now have the reveal of another enigmatic mega-theropod of far ranging lore and speculation: Deinocheirus mirificus (Lee et al. 2014). What strange and wonderful times in dino-paleo where in one year two of the most mythologized and sought after dinosaurs are revealed. Not only that but there is much to suggest that both were more than a little ecologically linked to aquatic resources!! Congrats to Lee et al. on their paper and discovery!!



When the first photos of the skull of Deinocheirus were leaked online I made a basically off the cuff post arguing that we should be open to the potential of a dinosaur the size of Deinocheirus acting as sort of a massive waterfowl - a dabbling megaduck if you will. Inspired by the awesome rendering by Andrey Atuchin I suggested an emphasis on aquatic resources, particularly Azolla fern, as a dietary staple.

Turns out my musings may have been closer to the mark than I could have even anticipated.

From the supplementary material (free online): (update I guess you have to go see the pics at the supplementary materials directly as I had them posted here but they were taken down, oh well)

Not visible from the leaked photo, but the lower jaw is surprisingly deep. Not out of proportion from other ornithomimids in terms of depth - it is relatively longer than other ornithomimids and in fact congruent with other theropods (i.e. tyrannosaurids) in terms of length. Despite being longer relative to other ornithomimids the skull itself was wafer thin, no more than 6 mm thick in many areas.

Remains of the foot (right pedal digit II and unguals) are consistent with a graviportal adaptation and possibly even suggest weight distribution on unstable substrates (i.e. mud).

And finally the preservation of fish scales/fish vertebrate/gastroliths hints at exploitation of aquatic resources.

Very cool. although no doubt some will call these finds into question in terms of taphonomy. But altogether the duck bill, putative stomach remains, spreading toes and hoofs, and wet habitat of the Nemegt suggest very strongly in favor of a generalist aquatic omnivore - a true duck-billed dinosaurs.

How did the skull of the animal operate? Given an animal so large and devoid of grasping teeth, hooked bill etc etc. how did it get the numerous small fish into its stomach? I don't have much faith in this animal being a stealthy heron type aquatic stalker. It was just too large and bulky. And even more importantly depth perception appears lacking. In order to catch enough small fish to make this adaptation worthwhile this animal should have an efficient method of capture with the minimum amount of energy and effort expended. Instead of looking to herons let us look at the wood stork (Mycteria americana) for possible insight into how this animal may have operated when catching fish.


What you want to notice in the above video of the stork foraging is that, unlike stealthy herons, the stork is intentionally disturbing the water and substrate in order to get small prey up in the water column where the sensitive bill can snap 'em up and also to make its own movements more cryptic.

Also check out this video below where you can better contrast the similar foraging strategy of the roseate spoonbill (Platalea ajaja) against some egrets. It should not be to difficult to notice some striking similarities in form and possibly function between spoonbills and Deinocheirus.


Seen in the context of these two birds the relatively long skull, light build of skull (possibly for rapid sweeping back and forth), and unusual stance start to make a little bit more sense. One can imagine that Deinocheirus as a spoonbill writ large could take advantage of fish (especially trapped), mass emergent aquatic insects, crustaceans and other invertebrates. Like the wood stork in the above video perhaps intentionally disturbing the substrate with those two handy eight foot long arms/claws in order to scare up prey and conceal itself.

from Theropoda
It has also been suggested that the mouth as a whole acted like a bit of vacuum cleaner sucking up food. This would require a tight seal around the mouth which brings up the whole cheeks versus non cheeks issue. This adaptation would also suggest strong facial/oral muscular control ability - more of a mammalian adaptation and not necessarily a strong suite of archosaurs. But then again it is not currently ruled out and what about that massive turtle that sucked up small prey recently discovered? So who knows dabbling, probing, sucking or all of the above in various degrees.

Of course it is hard to imagine such a large animal subsisting entirely on small aquatic organisms surely a little roughage was in order to round out its diet? In my other post I suggested Azolla aquatic fern as a potentially important food source. It likely had a worldwide distribution. Used today to fertilize rice paddies it reproduces exponentially, is high in nutrients, and has even been championed as a possible carbon trap and livestock/poultry feed.

I can find no reference to Azolla in the Nemegt but I would expect it to be present given how aggressively aquatic organisms spread. There was a nice recent paper on aquatic plants in the Maastrichtian of Patagonia. A diversity of emergent vegetation and floating types were all potentially Deinocheirus fodder.

Cuneo et al. 2014
But one paper I did dig up was one that is online for all to see and is a real barnburner (especially for all you tets rule plants drool types): Upper Cretaceous Charophyta From the Nemegt Basin, Gobi Desert  from 1969!! A diversity of ostracods (small crustaceans) from the Nemegt is also known.

What is Charophyta precious? Charophyta is a division of green algae and includes the closest sister group to land plants. And more importantly for our purposes here they spread quickly via clonal growth  across the bottoms of bodies of water. And there are 13 species known from the Nemegt.


Chara vulgaris
An even stranger potential food stuff would be Nostoc. This is a colonial cyanobacteria, It has a worldwide distribution and grows in all types of habitats. But it is especially hardy in terms of surviving drought conditions. When on land it is inconspicuous, but with the addition of water swells up into a jelly like mass. I first encountered Nostoc when I was investigating beaver on the Santa Ynez River in Santa Barbara county for my other blog Southland Beaver (shameless self promotion but you should seriously check out it out). I was so intrigued by the stuff that I thought I had discovered some weird new type of freshwater brown algae!! I sent the stuff to an aquatic plants specialist in New York where he looked at it under microscopy and told me that it was just Nostoc. Cool and weird stuff anyways.

Nostoc sp. Santa Ynez River
Nostoc sp. and Charophytes. Santa Ynez River Santa Barbara County CA
Anyways cheers and thanks for stopping by and reading this - I put it together rather hastily and just wanted to get something out there for Deinocheirus.






Monday, October 6, 2014

Thus Spoke Zarafasaura

Seriously I need to start a plesiosaur legal defense fund. What other group of Mesozoic beasties has suffered such a profound and jarring hit to their reputation? Once depicted as worthy and regal denizens of the deep, able to hold their own against the other Mesozoic marine reptiles - everywhere I look now

Hawkins demonic plesiosaurs battling other sea monsters in eternal darkness. nice

all I see are pictures of plesiosaurs getting rag dolled by mosasaurs or decapitated by pliosaurs. Seriously its like everyone in the ocean is just taking out plesiosaurs left and right as if they were blundering insults to Darwinian evolution.

From Hero to Zero


Well I say it is high time we turn back these insults to plesiosaurs. 

Don't get me wrong we actually do know plesiosaurs were preyed upon. I just think all this violence perpetrated upon plesiosaurs glosses over the very real and very impressive predatory arsenal they had at their disposal. You heard me right plesiosaurs had an impressive predatory arsenal.

I think first and foremost this emerging image of plesiosaurs as little more than cannon fodder for the more impressive macropredatory saurians it shared the ocean with has a lot to do with two prevailing notions; that (1) long necked plesiosaurs (plesiosauromorphs) are often considered a bit "samey" and; (2) they are considered gape limited (can't expand their lower jaw out) predators of small prey (i.e. basically fish no longer than 20" for the largest elasmosaurids).

Well with regards to number #1 that they are a bit "samey" this is quickly discredited upon actually looking at the surprising diversity in both tooth/jaw morphology. Yes there were slight, fine toothed plesiosaurs - that potentially even sieved small prey out of the water/sediment - but at the other end of the spectrum there were some impressively toothed and jawed species that speak to a more robust capacity for predation. Which gets me to #2 that plesiosauromorphs were severely limited to a prey base of only smaller fish and cephalopods.

In order to challenge #2 I want to invoke a little heralded elasmosaurid from the Maastrichtian (Upper Cretaceous) pbosphate rocks of Morocco: Zarafasaura oceanis (Paper 2013 Lomax & Wahl). I just want you to take a good look at the skull; the robust mandible; strong piercing dentition; large temporal (jaw closing muscle) area; brevirostrine morphology. This was the bulldog of the elasmosaurids. 

Lomax & Wahl 2013. scale bar 10 cm
Lomax & Wahl 2013. scale bar 20 cm

Are you really confident that this was a mere predator of only small fish and cephalopods - harmless to anything bigger? So confident that you would go for a swim with it? Are you sure that sauropterygian brain would not take an opportunistic lunge at you? Or even worse if it travelled and fed in groups (a distinct possibility given live birth for this group) that you might meet your fate in a spectacularly gruesome Mesozoic version of being "drawn and quartered" by several  20 foot long sauropterygians?


What I think gets left out of the discussion with regards to prey dismemberment in carnivores that operate at 1 g versus carnivores that operate in water is the differing physics of each realm. In the water as food is being shook, rolled, or twisted the water itself acts as resistance to such movement. This higher viscosity of water compared to air allows the consumer to gain leverage and further increase the damage and bodily insults to the food item as it is being shook about violently in any number of ways (yanking, rolling, twisting). This extra bit of leverage that aquatic predators can use to dismember food is put to good use by various sharks, fish, eels, crocodiles and other critters. And as I have discussed before I think a number of long necked plesiosauromorphs may have engaged in food dismemberment strategies - including cooperative feeding/dismemberment and twist/rotational feeding - to increase the size envelop of food items that they can consume.


Neck flexibility is a tricky thing in plesiosaurs. They could not likely do the graceful "S" snake like strike pose but dorso-ventral flexibility of the amount pictured above by Mark Evans is possible give or take a bit depending on how much intervertebral cartilage was present. But for our purposes here the diagram above is useful in imaging how such animals may have used the puncture/pierce type teeth, long neck, and heavy rigid torso to get bite sized chunks off of  carcasses. 

1) Establish a good securing bite.

2) With neck extended and heavy torso acting as fulcrum/pivot point/ballast - yank neck away from food item. If flesh is soft and/or rotten this step might not even be needed. 

3) Conspecifics and/or water viscosity aids in leveraging off a bite size morsel. 

4) Swallow, rinse, & repeat

Is there any evidence for Zarafasaurus oceani engaging in rugged feeding events? Well maybe... In the paper I linked to earlier (Lomax & Wahl, 2013) there is specific mention of "vertical, serration like marks preserved on the inner side of the left dentary" and the "odd, strong rugosity that surrounds the base of the posterior premaxillary teeth". Picture below of both features.

Lomax & Wahl 2013
Interesting for sure, but nothing definite. Could those vertical serrations suggest habitual feeding of shelled/rugged prey? Ammonites, chondrycthians, turtles or all of the above? Sidedness? Who knows but the rugosities, serrations, and general rugged and robust morphology of the skull and skeleton as a whole suggests a capacity for certain violent feeding activities.

Wiki. CC
But what spurred me on to write about Zarafasaura today, as I have been wanting to write about this guy for a while now, is actually a paper: Mosasaurids (Squamata) form the Maastrichtian phosphates of Morocco: biodiversity, paleobiogeography, and paleoecology based on tooth morphoguilds. Bardett et al. 2014 Gondwana Research Abstract:

Mosasaurid squamates are the most numerically abundant, and taxonomically/ecologically diverse clade of marine amniotes represented in the Maastrichtian Phosphates of Morocco. With few exceptions, they are faunally typical of the Southern Mediterranean Tethys Margin (around palaeolatitude 25°N) and range from the base to the top of the stage. The Moroccan assemblages include at least 7 genera and 10 species representing a broad spectrum of sizes and morphologies that illustrate several ecological trends. Noteworthy is the predominance of Mosasaurinae which are widespread in contemporaneous outcrops worldwide and constitute 80% and 70% of the total genus/species number respectively. In contrast, Halisauromorpha and Russellosaurina (plioplatecarpines) are scarce and tylosaurines are presently unknown. All of the Moroccan mosasaurids exhibit characteristic tooth morphologies and can be placed into resource partitioning morphoguilds indicative of adaptations for piercing, crushing or cutting. Medium to large predators are found to distribute along the ‘Crush’–‘Cut’ axis of the morphoguild projection, and a new ‘Crush–Cut’ guild, previously unrecognised amongst Mesozoic marine amniotes, accommodates severalPrognathodon species. Also of importance is the lack of mosasaurids along the ‘Pierce’–‘Crush’ axis, potentially inferring that these ecological niches were occupied by other marine vertebrates such as selachians and plesiosaurians. In addition, the relative abundance of mosasaurids throughout the Maastrichtian series of the Gantour Basin evidences direct ecological competition or predation phenomena.



Did you catch that sentence towards the end? The one that says "Also of importance is the lack of mosasaurids along the ‘Pierce’–‘Crush’ axis, potentially inferring that these ecological niches were occupied by other marine vertebrates such as selachians and plesiosaurians.

As the only other plesiosaurians known from the Moroccan phospates are dainty toothed polycotylids, who does that leave but Zarafasaura oceanis?

And as I said earlier we need to stem the tide of plesiosaurs getting man handled so here I drew a mob (siblings?) of Zarafasaura oceanis having a go at the carcass of an immature Ocepochellon bouyi. Did they kill it or scavenge it? You decide.


Putting a little of the alien, evil, otherworldly, Ctulhuish aspect back into plesiosaurs.


Cheers!!

Sunday, September 28, 2014

Green is Good: Slaying the Uber Mega-Sauropod


So I noticed I have not written much about plants lately but have been instead looking at marine reptiles and of course Spinosaurus in recent months - and thats ok (its my blog after all and expect MUCH more on Spinosauridae in the future). However I have been watching my feed and noticing a lot of hits coming in from various dino chat boards/ "dino fanboy" sites/ reddit etc. etc. - probably a lot to do with my Spinosaurus posts.  And this concerns me a bit in that I don't want this blog to turn into Carnivora forum type of place - but if you are from one of the JP forums/ Carnivora forums please stick around and hopefully I can convert you to a more egalitarian view of the past. So as an antidote to this concerning trend I am going to talk about plants (and at the end maybe a word or two about dinosaurs). 'Cause nothing should scare dino fanboys away more than talk about boring ol' plants, am I right? People coming in from DeviantArt you guys are cool, open-minded, and generally not of the same ilk please stay around. 

I want to post some pics of the Norfolk Island Pines (Araucaria heterophylla) in my backyard. And if you don't know why trees like this are important in Mesozoic paleoecology GTFO.  The cones these guys produce are pretty neat looking and just recently have started going to seed. They take a LOOOOONG time to mature. Wikipedia said they take 18 months to mature but I have pictures of these same cones from at least January of 2013 so that number from wiki may in fact be at the low end.

Same tree with cones coming in Jan 2013
Now I have seen an invasive Fox squirrel (Sciurius niger) rampaging about in my backyard for several months and although I have yet to see it in this tree I would not put it past a known predator of pine seeds to pillage these guys. There is a tasty and nutritious seed inside the woody, protective husk. Humans themselves will feast on the seed of related species. And I have seen ravens dropping kernels from a large Bunya-Bunya pine in the path of oncoming vehicles to crack the husk so that they can get at the tasty kernel. Students of Mesozoic life should not miss the potential for beaked ornithopods, stout jawed sphenodonts, various proto-aves, and multiberculates to have behaved in a like-wise manner.




Araucariaceae occurred throughout the Mesozoic and there is much to suggest that the family has changed very little. In the book Plants in Mesozoic Time Ch-5 Carole T. Gee and William D. Tidwell document the preserved whole plant remains of Araucaria delevoryassi from the Howe-Stephens Quarry of the famed Morrison Formation (i.e. big sauropod country). As you noticed they placed it in the same genera as modern species of araucariaceae and noted a suite of characters suggesting a mosaic of primitive and advanced features in it. Digestibility tests suggest the foliage of these trees offered an abundant and nutritious option for sauropods provided that they digested it for long enough periods of time.

I think that this is a reasonable option, especially for high-browsing sauropods. What I find interesting and a bit of a conundrum is that modern members of Araucariaceae are not particularly fast growers. Now one can make the argument that with their main predators - the sauropods - long extinct modern members of this family have divested from fast growth rates but I personally don't find this argument compelling. Why lose the fast growth rate if you ever had it to begin with? I have experimented with trimming some branches off of a larger A. heterophylla in my backyard. New growth will sprout out from the where the old branch was snipped off, but often from several latent nodes creating a bushier effect.



Artists of Mesozoic foliage striving to show how sauropod modified araucariaceae trees look should take note - what was once one branch has, after pruning, turned into a much more bushier "shelved" habit of several branches for the tree. What should be noted is that this modest growth - occurred over several years since I initially pruned it - not a spectacularly high rate of re-growth from pruning. If Mesozoic araucaria trees had similar growth speeds, and I find no compelling reason that they should not, this suggests to me that heavy sauropod browsing was mitigated to an extent by  predators/parasites/water needs necessitating constant nomadic movements as not to put their primary food source in a negative carbon balance.

Images like this, depicting sauropod herds ravaging the landscape, toppling trees, and devouring ad infinitum should be balanced with a more nuanced view of sauropod (and other dino megaherbivores) and plant coexistence. Admittedly I am arguing the negative a bit here. Of course sauropods (and other megaherbivorous dinos) toppled trees, disrupted/compacted roots systems, and plowed paths through the vegetation. Of course these things happened - it was just a matter of course for such large animals. But what I fear is happening is that we are seeing a parallel to the hypercarnivorous, all consuming semi-mythologized uber-theropod of recent years, except this time happening with megaherbivorous dinosaurs. Large sauropods and other dino megaherbivores may have just as well fostered diversity and heterogeneous patches in their landscape, huge piles of feces may have acted as recruitment sites for young plants - especially via seeds and spores that passed undigested through their digestive tract - and consumption of faster growing species allowing slower growing species to thrive. Large sauropods and other megaherbivorous dinosaurs may have in fact fostered and benefited the exact plant community that they depended on for food.

In fact a recent paper may provide some insight and suggest a much more nuanced relationship of herbivorous dinosaurs to the plant communities that they fed upon.  Plant Ecological Strategies Shift Across the Paleogene-Cretaceous Boundary. What this paper suggests is that the angiosperm plant regime shifted from a relatively slow growing, evergreen dominated strategy in the Cretaceous to a faster growing/higher vein density regime of deciduous angiosperms after the K-Pg event. This ecological reset would have selected against the slower growing angiosperms and shifted the balance towards the metabolically faster deciduous plant community we see today. And here it should be reinforced that this changing of the guards occurred over a relatively short span of time of less than two million years. The faster growing species were around during the Cretaceous yet it took the meteor impact to provide the disruption that gave them the toe hold that they needed. And keep in mind that during the Cretaceous the slow growing angiosperm community - itself making inroads on the even slower growing gymnosperm/pteridophyte community that dominated most of the Mesozoic - existed under the auspices of supposedly some of the most disruptive/all consuming/omnipotent herbivorous animals the world has ever seen - dinosaurian megaherbivores. But if megaherbivorous dinosaurs were so aggressive/all consuming/disruptive why did they themselves not shift the angiosperm regime to a more quickly growing regime and not the K-Pg event? For me this is very suggestive and opens up many other questions. Were dinosaurs themselves keeping the faster growing species at bay and thus allowing  slower growing species to proliferate? And, if true, then perhaps it was the extinction of the dinosaurs that allowed the faster growing species to proliferate after the extinction of their chief predators? Or did herbivorous dinosaurs not matter at all to large trends in plant evolution and climate change/evolutionary innovation/ and extinction events are really what matter?

Kenneth Lacovara Phd, Dreadnoughtus remains
And one final word on megaherbivorous dinosaurs. We were recently treated to the rollout of the most complete and well preserved mega-sauropod ever recovered Dreadnoughtus schrani. Of course I am a little late to the game on covering this guy but - you know it is over 65 million years old so I think time is relative... But to my point of being careful not mythologize megaherbivorous dinosaurus the same way we do to mega-theropods:

“With a body the size of a house, the weight of a herd of elephants, and a weaponized tail, Dreadnoughtus would have feared nothing,” Lacovara said. “That evokes to me a class of turn-of-the-last century battleships called the dreadnoughts, which were huge, thickly clad and virtually impervious.” 

My critique is aimed at the very name of the beast - implied to "fear nothing". To me the idea of an animal that fears nothing speaks to a very maladaptive trait. A dinosaur this size should still fear lots of things. It should fear crossing uneven ground and breaking a leg. It should fear getting mired in mud. It should fear other members of its own species that might fight it for mates, water, or food. It should fear too high a parasite load. And as I will explain in a second it should still fear theropods even if it had grown out of the ontogenetic stage where it fell in the range of prey.

One of my favorite bits from Greg Paul's Princeton Field Guide to Dinosaurs was where he mused on the challenges that a field expedition of humans into the Mesozoic would face:

"A herd of whale-sized sauropods would pose a serious danger of trampling or impact from their tails, especially if they were spooked by humans and either attacked them as a possible threat or stampeded in their direction. Sauropods would certainly be more dangerous than elephants, whose high level of intelligence allows them to better handle situations involving humans." GSP

And here I think it important to recognize that anger and aggression - in animals and humans - is often the result of fear itself. If an animal is truly without fear then it would not even bother with acting aggressive - such as stamping the life out of a theropod. And mega-sauropods, perhaps surviving several dozen theropod attacks over the course of their lives before attaining a size range putting them out of threat, had evolutionary impetus to fear theropods. And when achieving a size outside the prey range of theropods who is to say that they were even intelligent enough to recognize this fact? Many animals, including humans, have been suggested to have predator recognition hardwired into their brain. Again sauropods - having to grow through several different size classes - would have been vulnerable to theropods for much of their life. Their would be evolutionary impetus for these animals to have a built in hardwired innate fear of theropods. And with the conservative theropod bauplan and long evolutionary history between the two groups there is much space and time for sauropods to evolve an innate predator recognition of theropods. So images of sauropods crushing the life out of theropods are just as plausible as huge adult sauropods getting spooked and fleeing away from harmless, small theropods.



Even relatively big-brained mammals such as the deer in this video display latent fear of house cats arguably due to predator recognition. I would suspect smaller brained sauropods (and other dinos) acted  with much the same consternation, confusion, and stress when faced with a theropod. How they react - either fleeing or attacking is besides the point. It was fear that caused the reaction. And it was this perpetual "landscape of fear" that theropods maintained - whether or not they could even attack/prey upon the animal - that mitigated wholesale destruction/over browsing of Mesozoic plant communities.

Or you may disagree.








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