Wednesday, February 4, 2015

Plesiosaur Machinations IV: He Is the Last You'll Know....

When Harrison Okene, the chef on the oil company ship Jascon 4, rose early at around 4:30 a.m. on the morning of May 26, 2013 he would have had no inkling of the ordeal he was about to go through. A rogue wave slammed into the vessel that morning capsizing the ship. Okene, already awake and moving about, was at an advantage compared to his shipmates asleep and locked away in their cabins as a precaution against pirates in the ocean off Nigeria. Although he linked up with several shipmates following the hit they were washed away by incoming water, "I saw the first one, the second one, the third one just washed away. I knew these guys were dead." As the vessel began it's plummet 30 meters down (100 feet) to the bottom of the tropical Atlantic ocean Okene was able to find an air pocket, panelling to create a float to get partially out of the cold water, a bottle of coke, that, along with his faith, sustained him for 60 hours until rescue. Cold, in pitch black darkness, horrendously thirsty with saltwater taking the skin off his body and tongue the trauma for Okene was not yet finished, "I was there in the water in total darkness just thinking it's the end.... I couldn't see anything but I could perceive the dead bodies of my crew were nearby. I could smell them." It did not take long for scavenging fish and large sharks to move into the vessel and begin consuming his deceased shipmates,"The fish came in and began eating the bodies. I could hear the sound. It was horror."

Okene's hand making contact w/stunned diver. Link here.
Now reading this blog post (hopefully you don't skim read here tiss tiss) it is maybe a little hard to truly imagine what Okene went through and felt. You probably are well rested, not thirsty, have ate recently, are warm, dry, and - even if you are not with another person right now - you have experienced some social contact within the last couple of hours. Harrison Okene had none of these things going for him. Pitch black, no visual input only tactile. Cold and exposed. Even though able to get some of his body out of the water the skin was starting to slough off like an extreme case of raisin hand. Salt whisking away the water from your body like a giant desiccating jar. Tongue splitting. Social isolation. Loss of all sense of time and space. It is no wonder that Okene cited his faith as the reason he got through this. I wonder if I, as someone lacking faith, would have the same resolve he did.

And then, to truly remind him he was in an alien place indifferent to his continued existence, the sound of fish and sharks, breaking into the boat and locked cabins to have at his drowned ship mates. At these latitudes one has their pick of some truly nasty and voracious elasmobranchians that may have plied the very some confines Okene found himself trapped in. The tiger shark, Galeocerdo cuvier, as well as any number of reef sharks and even oceanic white tips are possible. But what I think would be truly terrifying would be the thought of massive bluntnose six gill sharks (Hexanchus griseus) breaking into the Jascon 4 and starting their slow motion feast of his shipmates.

Bluntnose Sixgill Photo Credit Island School
When we think of sixgill sharks what comes to mind is a true monster of the deep - a primeval undertaker that, luckily for us, sticks to the abyssal depths. This is not true though. Bluntnose sixgills, stick to the deeper parts of the continental shelf during the day but are well known to cruise up into shallow waters during the night. 30 meters down is well within their range. In fact sharks are noted for being very impoverished in truly abyssal depths. There just are not too many sharks of the abyssal plain. Why is this? Lack of resources for one and sharks do have those fatty livers to maintain have  been proposed.

And if you are further interested in the bimodal range of bluntnose sixgills this fishing show actually has some pretty good natural history tidbits as fishermen and hunters often times offer if you are ok with watching this genre of recreation (at least he is catch & release).

Never the less it would appear that sharks have had the niche of dominant large scavenger on the continental slope on lock down for some time and really is there any reason to suggest otherwise? As I will get to in a second maybe there is....

But just imagine in your minds eye Okene, his sinking ship transported via a time worm hole to the bottom of a Cretaceous ocean, and the undertaker that greeted him grimly at the bottom of the ocean was not the unblinking eye of a six gill shark but the snaggly toothed grin of a Terminonatator elasmosaur probing at his water softened extremities...

Terminonatator skull (Sato 2003) c/o Adam S. Smith

The idea of scavenging plesiosaurs is not a new one. In fact there are loads of interesting old papers on plesiosaurs from the grand ol' fossil collecting days full of the great writing and that old school penchant for flair that so used to characterize scientific writing but for whatever reasons has been replaced by a less colorful tone in most contemporary scholarly writing. And below is a gem I found on the interwebz by S.W. Williston titled North American Plesiosaurs in which he presciently suggests short necked polycotylids evolving from longer necked plesiosaurs, all but spells out Elasmosaurus using shallow waters to raise young, and interprets long-necked plesiosaurs as scavengers:

Zdenek Burian. 1955 Elasmosaurs & Tylosaurus
A constant theme of these posts has been that although much of the first interpretations of plesiosaur got a lot wrong, maybe they got a lot right and we should be careful not to throw the baby out with the bath water. In fact maybe it is later interpretations that have got further from the truth in some regards. And with scavenging plesiosaurs we do have some bona fide proof that they did eat dead stuff.

You might remember a couple of years ago a plesiosaur from the Jurassic Sundance formation with the preserved bones of a prenatal ichthyosaur in its stomach? You can find the paper online although it  takes a while to download.

Phote credit Fossils and Other Living
Prenatal Ichthyosaur vertebrae in stomach of plesiosaur
Now for whatever reason the ichthyosaur embryo was voided - either in life or death - and the plesiosaur opportunistically gobbled it up. But what about larger stuff? There is the consistently mentioned observation by Barnum Brown of broken up pterodactyloid bones preserved in the gastirc region of a plesiosaur from the Niobrara formation (late Cretaceous):

You should note that not only is Brown very insistent on plesiosaurs foraging on invertebrates commonly (read ammonites) he suggests that gastroliths did the chewing - I AGREE!! But about that pterodactyloid - although he does not name a species we only know of Pteranodon (common) and Nyctosaurus (uncommon) from the Western Interior Sea. As adults both species sport huge head gear and pointy and robust finger and arm bones. A significant choking hazard for such a supposed "gape limited predator" unless it just broke the pterodactyl bones by bashing it against the surface of the water or tugging on it with a friend or simply chomping on it repeatedly. But both the "pterodactyloid" remains and the ichthyosaur point to a more opportunistic, wider scoped foraging strategy than the usual dogma of "gape limited predators of small fish and squid - hardly a threat to anything larger than a trout" that has become a bit of dogma if you ask me. Even if the animals scavenged were small enough to be swallowed without dismemberment how many gape limited scavengers do you know that >only< eat the dead stuff they come across that they can swallow in one gulp? I can't think of any. If you are an opportunistic scavenger/predator (which I infer to be the dominant signal we get from plesiosaur stomach remains) then you don't turn your nose up at a free meal of any size. You break it up into smaller pieces to swallow - like any self respecting giant petrel, nile crocodile, western gull, or tiger shark would do!!

And now back to the question of dominant large deep coastal/contintal slope scavenger in the Mesozoic. Large sharks were certainly around in the Mesozoic and were already among the top pelagic large predators of the time. But I will argue that there was a bit of competitive exclusion going on in certain environmental situations that tipped the scale of power towards plesiosaurs (and other air breathing marine tetrapods of the time mosasaurs, ichthyosaurs, marine crocs) and that was repeated and consistent anoxic episodes throughout the Mesozoic. Simply put: you can't be a very efficient gill breathing scavenger in anoxic waters because, ummm, well you still have to breathe. And even if you can operate at very low oxygen amounts you are going to be a lot more sluggish, a lot less battle ready than those air breathing marine reptiles that are outswimming you and outcompeting you to all those carcasses in oxygen limiting zones. And why might you have loads of carcasses in anoxic waters? Anoxic waters can occur because of lack of ocean mixing but they can also occur when nutrients in the water stimulate a super bloom of phytoplankton and the concurrent food chain upwards. This explosion of life, and more importantly decaying particles with respiring bacteria, simply suck up all the oxygen from the ocean. With lack of ocean mixing and large scale monsoonal events weathering continents and dumping nutrients like fertilizer down the Mississippi into the Gulf today into the oceans of the Mesozoic may have experienced both types with regularity. And if vast shoals of fish, belemnoids, ammonites and other victims were caught in once nutritious waters turning anoxic that was a veritable feast for any scavenger that could get to them. Air breathing marine reptiles were free to do so and could go where sharks simply could not. Of course this all a little dependent on marine reptiles being able to handle scavenged animals that had succumbed to "red tide" which today kills marine mammals and birds.

Of course this does not imply that sharks were not successful in the whole of the Mesozoic - it appears that there were indeed large sharks then - I am just suggesting that in certain times that anoxia prevailed plesiosaurs - and other marine reptiles - had a distinct advantage over sharks. Whether or not this purported advantage resulted in evolutionary success of marine reptiles over sharks in certain epochs - I don't know but it is an interesting thought. And we do know from loads of examples sharks were scavenging a lot of stuff back then - especially dead marine reptiles.

Above I have depicted such a hypothetical scene of marine reptiles and pterodactylids converging on windfall of ammonites that have died due to a local anoxic event. The plesiosaur is Meyerasaurus victor. I know, usually considered a rhomaleosaurid pliosaur, but come on now that distinction is completely arbitrary especially in this case. Whether you want to call it a short necked plesiosaur or a long necked pliosaur any grade school kid would point out that it looks like the Loch Ness Monter. The ichthyosaur it is competing with and harrying is an indeterminate variety of Temnodontosaurus - Darren Naish loves talking 'bout this guy on his blog and the genus is in a bit of flux so I just took some liberties and depicted a medium sized longirostine variety. For sure I did not want to convey the reptilian dolphin meme that dominates reconstructions of these guys - they had shark like/tuna like caudal fins for christ's sake - why should they not swim like a shark (and probably not "porpoise" while swimming anyways).

The Posidonia shale dating to the Early Toarcian of the Early Jurassic best known from the Holzmaden of Germany is interpreted as a somewhat anoxic area of the Tethys ocean. There was the large Dorygnathus which yeah I took some liberties with and made it a little larger (my Xmas wish in paleo is the discovery of a truly large marine rhamphorynchoid). To the left you see the more svelte but cool still Campylognathoides. And you know I gots to speculate that the heterodont, stout, and piercing dentition of this guy would be great to get into the certain shell of a certain marine invertebrate that was so common it is used as an index fossil throughout the Mesozoic.

On a little tangent regarding flying marine reptiles. Make them more voracious, aggressive, and highly opportunistic in depictions. Flying around like a bat out of hell challenging other pterosaurs and foraging willy nilly even in the midst of larger marine reptiles. Like pelagic birds today. Especially large gulls, skuas, petrels, and albatross. Food doesn't come within reach at the surface all the time after all. Below are some pics I stole that best capture the fray that is feeding seabirds. The photographer made special mention that the most combative and violent bird was the smallest - the little Cape Petrels. All photos by Karim Sahai, link here. I tried to email him for permission to use but no reply. But to cool not share with the and if you got the cash go buy something from his website or comment there.

Cape Petrel (Daption capense) & Wandering Albatross (Diomedea exulans) feeding. Karim Sahai
Southern Giant Petrel (Macronectes giganteus) looks on at cape petrel quarrelling with
Southern Royal Albatross ( Diomedea epomophora)

Cape Petrel fighting next to Southern Royal Albatross
Anyways slight diversion but I think that needed to be said. Back to the marine reptiles. Meyersasaurus
was a pretty neat looking plesiosaur and interesting in its proportions. Check out this pic of Adam Smith from the Plesiosaur Directory next to one below used w/permission.

Adam Smith w/Meyerasaurus at Museum am Lowentor -Stutgart State Museum of Germany
Look at that nasty set of chompers!! This guy still had some heft to him - maybe the size of a bull stellar sea lion more or less? And those fins - is that a bit of a high aspect ratio to them I see? I think it is. I depicted Meyerasaurus as a bit like the oceanic white tip shark - an opportunistic, energy efficient cruiser of the open ocean. And I took this analogy a bit further and made Meyerasaurus to Temnodontosaurs a bit of like what the oceanic white tip shark is to pilot whales - a follow a long opportunistic scavenger/hunter. But I took the liberty of making Meyerasaurus a relatively more aggressive harasser and competitor of Temnodontosaurs. The adults of neither could safely attack each other - if you are a sight dependent deepwater forager like Temnodontosaurus likely was you could not afford to lose an eye to a well placed bite from Meyerasaurus.

Oceanic White Tip Shark & Pilot Whales

Anyways I want to wrap this post up. I do want to do a speculative story line here but I will save it for another time. I want to keep the posts kind of bite size. And I am sleepy. Say goodnight Bluntnose Sixgill.


Monday, January 26, 2015

Using Phytoliths to Determine Tree Cover in Ancient Ecosystems

Ok all you dinomaniacs its time to stop fapping over massive theropods, titanic sauropods, and feathered (or non-feathered) velociraptors and talk about some boring ol' plants. And not even whole boring ol' plants even, we are talking microscopic remains of plants called phytoliths. You may or may not be aware but there has been a bit of a slow motion revolution of sorts going on in paleoenvironmental circles for some time now - and knowing about it will ultimately help in potentially viewing dinosaurs - and other extinct beasties - with greater resolution. And that should be of some interest to you if you want to really get into the nitty-gritty of paleoecology.

Scanning Electron image Phytoliths Elephant Grass Parr et al 2001
Just published in the January issue of Science, Linked canopy, climate, and fauna in the Cenozoic of Patagonia lead author Regan E. Dunn.,

Yeah, as it turns out those boring silica based epidermal cells found in loads of plants and just kicking around preserved in sediments going back to the Devonian, yeah they might just be useful as a proxy for determining relative vegetative cover i.e canopy thickness for extinct environments. And even if you could care less about plants that's pretty cool for it's potential to elucidate characteristics of extinct ecosystems and also potentially infer habitat characteristics and ecologies of extinct animals - even dinosaurs.

From redOrbit review article:

"The new methodology provides a high-resolution lens for viewing the structure of ecosystems over the  deep history of our planet. This capability will advance the field of paleoecology and greatly improve our understanding of how future climate change will reshape ecosystems." Alan Tessier, director NSF Division of Environmental Biology.

"Vegetation structure links all aspects of modern ecosystems, from soil moisture to primary productivity to global climate. Using this method, we can finally quantify in detail how Earth's plant and animal communities have responded to climate change over millions of years, vital for forecasting how ecosystems will change under predicted future climate scenarios." coathor Caroline Stromberg, curator paleobotany Burke Museum.

As an independent test the researchers compared modern phytoliths collected from a variety of closed to open habitats in Costa Rica and the observed forest cover resolved quite nicely with the collected data. So that's a slam dunk right? We can now really get a handle on what some of the famed Mesozoic environments were like.. Was the Morrison forested or more open savanna type vegetation? The Hell Creek Formation? Well as I mentioned at the beginning of the post this has been a bit of a slow motion revolution (which is fitting as plants operate in a slower pace of life) and using phytoliths has been bandied about as a way to infer past vegetation for some time.

A quick internet sleuthing on my own part revealed this paper just published last year which cautions against too literal interpretations of phytoliths and calls attention towards soil type:

So, as always, things are a little more complicated than first imagined. Furthermore how much phytolith is produced by plants is variable; not all plants produce phytoliths. Notably for those interested in Mesozoic ecosystems many conifers, including Araucariaraceae and cycads lack phytolliths. But on balance phytoliths are common in Equisetaceae (horsetails) and Selaginellaceae (spike mosses) and several types of ferns. At least according to wiki and my quick investigation.

Anyways some stuff to think about and I find these papers and paleoenvironmental topics/paleobotany stuff get's a little underreported in the general paleoblogosphere. I wanted to write more but my stomach hurts.

So here is pic I took in Northern California

Sunday, January 18, 2015

Black, White, and Red All Over: Orcas Penetrate the High Arctic

You could say I have shifted a lot of my attention and interest onto aquatic stuff lately - hey I included the word salad in the name of this blog for a reason, a salad can have all manner of toppings including seafood!! So no plesiosaur machinations today nor spinosaurid stuff although plenty more to come this year in those regards so stay tuned. No today I want to focus on extant marine creatures/ecological communities of the Arctic. Namely recent range expansion of what I consider personally the penultimate marine predator of all time (sorry Megalodon fanboys), the killer whale or Orcinus orca while Ursus maritimus - the polar bear - diminishes.

 Orcinus orca. Uploaded by EvaK. CC 2.5 Senckenberg Museium Frankfurt Germany
The polar bear, Ursus maritimus, has become a bit of a symbolic linchpin for anthropogenic global warming. As a top predator at the top of the world which is inherently dependent on pack ice as a platform to hunt it's more aquatic capable phocid prey this choice is an obvious one. As the ice goes, so does the polar bear. And in our ramped up, high velocity anthropogenically driven world ecosystem there is a bit of an asteric at the question of polar bears surviving in an increasingly ice free Arctic - can they even adapt that fast with the pace of current climate change? I do lay out one possibility here. Never the less we should not consider the possibility of an ice free Arctic or the extinction of the polar bear as the end of an "ecosystem" so much as merely the start of a strange, new one. And quick to move into and usurp the polar bear as king of the Arctic is the killer whale, a shifting of the guard we may in fact be witnessing currently and which might become a veritable reality in this century.


Compared to the three most notable Arctic whales (bowhead, beluga, and narwhal) the killer whale is at a bit of a disadvantage in ice- it has a huge dorsal fin, especially among the males where it might be 2 meters tall. So although they do move up to the edge of the pack ice in the Arctic and Antarctic they do not penetrate very far into the pack ice or areas with large amount of floating ice due to obviously painful scrapings and cuts that constant abrasion against ice would incur. So not only is ice a hunting platform for polar bears and a resting/birthing stations for seals - it a sanctuary of sorts for Arctic whales from killer whales. But a spate of incidents suggests that the sanctuary that ice provided whales in the high Arctic Canadian archipelago and Hudson Bay is no more. There is a bloodbath in paradise.

Glenn Williams. Narwhals jousting

"We saw this big bloodstain in the water", and "You could smell the blubber in the air. And the killer whales were moving onto the next one, like nothing had happened." so describes a witness to an increasingly familiar but previously rare event - killer whales moving into Hudson Bay and targeting beluga whales in the estuaries and bays that they traditionally stayed in during the summer months in relative safety. Orcas Pop Up near Churchill, Feed on Beluga.  What was at most an ephemeral and rare predatory encounter between the two species is looking more and more like a deliberate hunt by the killer whales. The ice disappears earlier and arrives later allowing the orcas to move in and stay longer. There has been the suggestion that some recovering populations are being suppressed and others may be further diminished. Sometimes the killer do not make it out of the Bay in time, as occurred last year when a pod was trapped - but eventually freed by currents.

photo credit Davidee Mina. killer whales trapped Hudson Bay
What is obvious is that killer whales are increasing their presence in the Arctic, especially the eastern Canadian Arctic, and that they are targeting more than just belugas.

Invasion of the Killer Whales. Nature PBS December 18, 2014.

The portrait painted by the above highly recommended Nature documentary is one of an ecosystem in flux. Polar bears scrounging for carcasses on the beach, sea bird eggs, and fishing for Arctic char in rivers. And killer whales moving into an ecosystem in which they had previously been kept at bay. Moving with a purpose, covering over 200 km a day to seek out narwhal populations in the Canadian Archipelago from which they could not reach before. Bowhead whales evincing massive scars and bites from killer whales and switching their movements towards areas that retain ice year round to avoid the killer whales. Playing a game of cat and mouse the two whales listen to eachother across vast expanses of ocean.

Tagged killer whales (red) versus tagged Bowhead whales (yellow) showing avoidance patterns
Bowhead fluke w/killer whale maulings
And a third archpredator of the Arctic, Homo sapiens of the Inuit culture, seeking answers and context to an archpredator which had only previously been an ephemeral visitor but which now increasingly shapes the prey and the ecosystem that they are dependent on. Will the seals and whales that this culture depends on shift range and habits to deal with their new predator? How will this affect the ability of these people to find them? Are we looking at an example of killer whales competitively excluding humans?

"I was hunting these narwhals and they were fleeing from some killer whales. The killer whales were travelling fast and upside down. And they breached the water chasing the narwhal. When they got close to the shore where the narwhal were they took bites out of two of them very quickly. This is when I realized that they are supreme hunters." Inuit elder.

"We knew changes were happening and wanted to understand them... We anticipated a change from the bottom up... We recognized the killer whale as that top predator that was all of a sudden making these huge changes in the Canadian Arctic. And it was something we didn't really think about at the start but there it was staring us in the face." Steve Ferguson, Canadian fisheries biologist on realizing that simultaneous with a bottom up trophic cascade in the Arctic a top down trophic pressure via killer whales was also occurring.

While killer whales in the eastern Canadian Arctic appear to be expanding their range to include areas westward and northward and capitalizing on prey/feeding grounds previously out of their reach between Alaska and Siberia on a group of islands called the Diomedes they have been documented predating on walrus recently. The following clip I scrounged up on Youtube is to the best of my knowledge the first video documentation of such an occurrence.

Walrus, which are themselves recognized as keystone species due to the significant bioturbation they do when digging up benthic prey and are significant in the diet of Inuit, are also highly dependent on ice for resting upon. Loss of ice concentrates walrus in large herds on the land which might further enable killer whales to find and target these large seals.

Polar bears have also been documented targeting these concentrations of walruses, although concentrating usually on the young. Another food source grounded polar bears have been utilizing during the summer months are runs of a type of arctic salmon called arctic char.

Polar Bears hunting Arctic Char. Nature
 Harkening back to their brown bear roots...

Global ecosystem change is already afoot. Some will adapt. Some will move. Some will benefit. And some will perish. How this will all play out and what surprises await who can say?

(c)US Navy. public domain. USS Honolulu 450 km (280 mi) from N. Pole

Thursday, January 15, 2015

Dog-Eat-Dog World: Theropod Wars Revisited... Morrison Style

Jim Kirkland. Juvenile Ceratosaurus Leaping on Tanycolagreus. NAMAL
The above image of provided by James Kirkland as part of a temporary exhibit at the North American Museum of Ancient Life (NAMAL) depicts a putative intraguild predatory encounter between a juvie Ceratosaurs sp. and a little known theropod called Tanycolagreus. Now, I want to avoid a discussion on whether or not Tanycolagreus is in fact a synonym of Coelurus - I'll leave that up to someone else. I want to use this picture as a bit of a springboard for a larger discussion on the obvious diversity of theropods in the Morrison and of course a fave topic of mine - niche partitioning.

Now I have discussed niche partitioning before and it's not that I 100% disagree with the concept - there is a robust body of evidence from modern contemporary ecological studies that it is a useful theory - I just think that the concept is a little too oversold in paleontology, especially dinosaur paleoecological studies. What I am trying to say here is, let me choose my words carefully, is that niche partitioning gets seized upon because it speaks to a real human need to put nature in a box. To separate and control things. But nature, especially biology, is slippery and slimy and if you try and corral it at one end it pops out at the other.  Example: dinosaur A occupies a different morpho-ecospace than dinosaur B- and voila they coexisted by avoiding competition and eating different diets!! Now, as I said earlier I do think niche partitioning is a thing and worthy of study I just think a little more nuance, elaboration, and attention to what modern animals do is worth adding to the discussion.

Let me draw your attention to two recent studies, one paleo and one ecological,  that may elaborate on what I speak of. The first one is concerning a new smallish ceratosaurine theropod from the famed Como Bluff site of the Morrison formation recently published in Volumina Jurassica (get full paper here):

Now what I want to draw your attention to is the last sentence: "... it is tenable that theropods of different clades co-existed in the same ecosystem at the same time and most likely competed for the same food sources."

YES-YES-YES!! Finally a paper talking about theropods coexisting without resorting to the knee-jerk reaction of "well they must have partitioned resources to coexist". Again niche partitioning is a useful concept, but to gage the extent that it occurred first it is necessary to really assess; 1) Is a resource really limiting? i.e. maybe there was actually enough food to go around for all without having to divvy up everything via niche partitioning. It's not hard to imagine how, even when small prey was lacking, the occasional sauropod carcass was a windfall for theropods large and small and saw them through many a tough dry season; 2) Instead of always looking at morphometrics and trying to deduce partitioning maybe the landscape itself was partitioned. And finally sometimes species compete violently and both species just continue to live side by side with no elaborately contrived niche partitioning needed. Lions and hyenas come to mind.

With number 2 in mind let me direct your attention to a study published in the November 2014 issue of Ecology (Ecological Society of America):

Ok so a lot of things to glean from this study. Both the coyote and kit fox have substantial overlap in a prey base of mainly rodents/lagomorphs but the coyote is able to exert pressure on the kit fox as an intraguild predator. However, this was not enough to dissuade kit foxes from coexisting with coyotes in the habitat with highest prey biomass (shrublands, interdunal grasslands) although the foxes were less common there than in marginal, prey poor habitats (gypsum dunes, pickleweed playa) that coyotes shunned, presumably due to their relatively higher metabolic/water needs. In both instances it was prey abundance that modulated the intra-guild predator relationship with foxes able to exist in environments unsuitable for coyotes as well as the more prey rich environments that coyotes favored. The authors note that this is the first time two intraguild predator states - coexistence and competitive exclusion - occur simultaneously in the same ecological community.

All right with that interesting study in mind - showcasing the intricacies of prey abundance, competitive exclusion, and intraguild predation - let us revisit the Morrisson. Where, depending on who you talk to, it hosted a diverse bestiary of maybe half a dozen or more theropods evolving together amidst a tangle of megaherbivores and  smaller ornithopods in a seasonal, drought prone, heterogenous landscape. One often reads of the dominance of Allosaurus numerically to other theropods - both large and small - as reflected by fossils here. How much of this numerical dominance is real and how much an artifact of some type of preservational bias? If Allosaurus was the coyote of the Morrisson, limiting itself to only the spots in the community that provided it adequate prey and water - maybe it was excluded from the more resource poor parts of ecosystem where the more moderate sized and thrifty theropods held sway ala kit foxes via competitive exclusion? The large skeletal size and proximity to water of Allosaurus would further embellish this noted abundance of Allosaurus as compared to smaller theropods which frequented less productive lands further from areas of deposition and therefore preservation. And this would help explain the noted "hidden fauna" of smallish theropods in the Morrisson... and maybe Torvosaurus as the predatory wolf to the smaller Allosaurus... food for thought.

Friday, January 2, 2015

Join the Antediluvian Salad Facebook Page!!

Join HERE.

In addition to getting notified for new posts I will attempt to link to interesting articles, posts, videos, artwork, pictures that further delineate and spotlight the antediluvian salad eco-morphospace in the blogosphere.

Thursday, January 1, 2015

Plesiosaur Machinations III: The Family That Slays Together, Stays Together

First of all if you have not read Plesiosaur Machination Part I and Part II, GTFO, go read 'em,  and come back. If you have please enjoy Plesiosaur Machinations III: The Family That Slays Together, Stays Togetether (intentionally misleading title).

Ahhhh the holidays... did you feel that family togetherness, or maybe not so much? Whatever your particular situation is you can rest assured that the complicated emotions we feel, that are likely heightened this time of year, are a direct consequence of our mammalian social heritage, limbic system, and neocortex. But it is the limbic system, sometimes referred to as the "paleomammalian brain", that is most intimately associated with emotions. But the term "paleomammalian brain" is a bit of a misnomer as it implies only the synapsid line of tetrapods developed this emotional brain. Birds have their own version of the limbic system and it has increasingly become apparent that reptiles have a limbic system as well suggesting that the evolution of the limbic system occurred after the split of amphibians to reptiles. And given the recent revolution in reptile social behavior and, dare we say, emotional capacity this should not be so much of a surprise that reptiles have a (limited) emotional capacity. Given our history of trying to separate ourselves from other animals and having only so recently admitted alliance with primates - maybe we are still recalcitrant in allowing reptiles such a capacity for emotion which we link with ourselves, mammalia, and "higher" brain function?

But let us not get carried away here - no need to feel that you have neglected the brooding artist inside of your pet bearded dragon. If we count hate, love, lust, fear, anger, and contentment as the base emotions from which they are elaborated upon in mammals and birds - especially when used in conjunction with the neocortex - then reptiles would certainly fall under the banner of emotional animals, however diminished in capacity and variety as may be when compared to mammals. And as was discussed in the last post, several species of live-bearing lizards provide a model for how viviparity may have fostered a social bond in plesiosaurs. Here I want to consider how the emotional state of contentment achieved via  physical contact may have further solidified the social bond in plesiosaurs. And that an animal need not develop an expanded neo-cortex to achieve this blending of the social and emotional.

By Ampatent. St Louis Zoo. C.C.Attribution-NoDerivative Works 3.0 License

And then as now I would posit physical touch as the medium through which the social bond was consecrated in the extinct marine sauropterygians. A simple bio-physical chemical feedback loop reinforced via the winnowing effects of Darwinian evolution. The plesiosaurs that seek out and engage in physical contact with members of their own species, reinforced chemically by a presumed oxytocin like chemical,  stand a better chance of surviving than those that don't. No need to evolve a highly modified, derived mammalian type brain. The reptilian brain is good enough. Now diving into the wormhole of what chemicals may have enhanced the bonding experience - some sort of oxytocin "cuddle" type hormone or equivalent, most likely vasopressin - is an interesting question and one that is only minimally explored in modern reptiles. I myself don't feel qualified enough to offer any thought on this aspect of bio-chemical cuddle hormones but there is certainly the potential that some type of hormone fulfilled this role in plesiosaurs as suggested by modern phylogenetic bracketing.

And to the organ most useful in maintaining social cohesion and contact in plesiosaurs - that long dangly neck of course!!

A Touch in the Void by Duane Nash
With the body and flipper usually engaged in swimming the neck of plesiosaurs offers a useful organ to maintain physical contact and proximity with other members of the plesiosaur phalanx. This contact can be maintained while at rest, while traveling, and even while foraging. It is important to conceptualize the vastness, the isolation, the existential dilemma of living in the open ocean. Even to a 13 meter long elasmosaurid, equipped with a reptilian brain, the vastness of the Mesozoic oceans must have felt daunting. And the reassuring touch of another member of it's kind may have done much to assuage this sense of vulnerability and isolation. If we take this notion of kin-based social bonding in plesiosaurs to it's logical conclusion - a very touchy-feely bonding mechanism seems most likely. And one is forced to genuinely consider the probable likelihood of giant marine sauropterygians (and maybe many other extinct. live-bearing marine reptiles) engaging in what can most accurately be described as emotionally based, physical touch mediated bonding activities. And in this manner becoming eerily, maybe creepily, convergent to the well established physical bonding practiced by many cetaceans - most famously dolphins.

Which is not so strange is it when we commonly cite convergent evolution in terms of anatomical adaptations in disparate groups; why not convergence in social behavior when similar environmental/reproductive constraints are placed on distantly related tetrapods?

Wiki commons. Bottlenose mother/infant. M. Herko
Spinner Dolphins. Sunphol Sorakul. CC 2.0
Ebony & Ivory By Duane Nash
And I leave you with Dave and his big pet black throated monitor Big Boy.

Happy New Year and don't forget to hug a reptile!!

Saturday, December 27, 2014

Don't Draw Celibate Cycads!!

One does not have to look far to get into the well documented, especially on the paleoblogosphere, interplay between paleontology/paeoartistry/plagiarism/tropes etc. etc. Chances are if you read this blog you are aware of this crucial and ongoing debate especially as it pertains to certain tropes or memes that seem to get repeated, maybe even subconsciously, with regards to certain peculiarities or assumptions about the life appearance of extinct animals (esp dinos). And I don't really want to bother with a list of links to this ongoing discussion here although for starters there is the All Yesterdays movement, The Paleopolice FB/deviantart group, Support original Paleoart, and so on and so forth. What I want to do on this post is focus on the dilemma of "the celibate cycad".

A bit of a qualifier here. Not that there is anything particularly wrong with depicting a cycad alone on the landscape or even utilizing what I refer to as "the big three" (ferns, cycads, conifers) in Mesozoic landscape - it is a question of representation and over utilization, especially when alternate views are more or just as defensible. In the past I made the same argument with dinosaurs always conveniently framed on a bare patch of dirt. Now, truth be told I can't take 100% credit for noting that very common trope - I recall first hearing it mentioned in an online discussion somewhere - but I do think it is worth noting and it is unabashedly common once you start looking for it. Again, not that there were no bare patches of ground in the Mesozoic and not that dinos did not stand on them - conveniently framing themselves - it is a question of this view being over represented. And, while it is true that this meme repeats so often as a function of the artist framing the main subject which is the animal, after a while this repetition becomes a disservice because it does not speak to the full mosaic of ways in which animals, even large ones, clamber through, hide in, and engage with the vegetation in their respective environments.

(c) Gregory S. Paul
(c) Conway
(c) Troco
All three above images, beautiful and illuminating in their own rights, all depict the dinosaur conveniently framed on a bare patch of soil meme.

And so onto the problem of "celibate cycads". I first heard the term "celibate cycad" in an article by Jennifer Frazer titled Are Cycads Social Plants? Now I have discussed this concept of large herbivore mediated cycad dispersal before here but to recap cycads are a bit of an enigma - slow growing, toxic foliage and large seeds with a fleshy, nutritious outer coating called a sarcosta but somewhat analogous to angiosperm "fruit". It has been surmised that the large seed serves two purposes - small dispersers such as monkeys, possums, rodents etc etc. will tend to move the seed not too far from the parent plant. This increases the chance of the seed growing up in the vicinity of other cycads and, because they are "sexed" plants with a male and female plant and pollinated by insects, enhances the chances of reproductive success. This explains why cycads do not invest in bountiful numbers of cheap, small seeds which would tend to be dispersed further from other cycads and thus grow up isolated and celibate. For large dispersers - flightless birds, giant marsupials, dinosaurs - many "fruits" can be swallowed whole and then deposited en masse in the animals dung and thus setting up the potential for a new grove. What is important to keep in mind is that whether it be via small or large animal mediated dispersal grove formation is encouraged in both scenarios. Further supporting this scenario is the tendency of cycads to mast reproduce concurrently to attract pollinators and dispersers in numbers.

2013. Hall & Walter. Macrozamia Miquellii. Mount Archer Park, Australia

And so this tendency to grow in groves and reproduce concurrently is an attribute that paleoartists should take note of when depicting Mesozoic landscapes. It is especially important if one makes the defensible speculation that dinosaur herbivores/omnivores were commonly attracted to these mast cycad fruiting events as a source of food. Or possibly pterosaurs, mammals, sphenodonts, and crocs as well.

Arjay Bee
So are "celibate cycads" a problem in paleoart? I would say after looking over the vast majority of paleoart that no, most artists get cycads right with regards to depicting them most commonly in groves. But it is something to be aware of. I would love to see more of an emphasis on cycad groves as a common micro-habitat in Mesozoic landscapes.

However I would be remiss not to highlight the growth in popularity and utilization of digital artwork, especially per the influence of Julius Csotonyi, and possible problems there of. One of the main flaws in Julius' work as it pertains to vegetation is his plants are often vibrant green and look maintained as if in a park or garden - and this may have to do with the source photograph was from a park/garden. I have heard this criticism before but it bears repeating. Case in point here where the cycads are missing a skirt of old/dead dying leaves and some are borderline celibate. Also this one here which depicts several possible celibate cycads. And given their slow growth rates I don't place a lot of faith in cycads being common plants near riparian areas and dinosaur nesting grounds which are both prone to disturbance. And Julius also loves to put his dinos on a bare patch of dirt. Now I don't want to pick on Julius too much - I am not the hugest fan of digital art but Julius does a better job than most with it and I am a fan of his & his book -  but we should not be caught unawares that when certain artists get heralded as the "top of the line" that it is these exact artists that are the ones that most need to be looked at under a critical eye. This is due to the simple fact that these artists will have a proportionately greater influence than others over time. Whatever biases and flaws are imbued in their work, and history suggests that there are always some (see GSP and shrink-wrapping), will be co-opted by future artists. And this constant nit-picking of the top of the line artists will further refine the interplay of science and art in the future.

Cycas media. Tanetahi

Coming Soon: Don't worry loads more plesiosaur machinations coming up, if you liked the first two then lots more where they came from and IMO will get better and more interesting with time. Also if I don't post anything new before the New Year loads of more stuff planned for next year including some thought pieces and interpretations brand new!! Thanks for spending your time here consuming content when you could have spent it elsewhere in the unlimited free content world we live in. About to hit a quarter million unique page views!! Thanks
Related Posts Plugin for WordPress, Blogger...