This Island Earth Part IIIc: Theropod Wars

So you may have noticed it has got a little toothy around here as of late... what with all the talk about sharks, top down control, intraguild predation, theropods of Kem Kem- I thought this was a blog about plants man. What all these posts are building up to is this critical installment of the This Island Earth series. Basically what I am trying to build a case for in the This Island Earth series is that the dinosaurian megaherbivores, despite their larger size, were actually less stressful on their respective vegetative communities than modern mammalian herbivores. If you want to review my argument points so far- go ahead and do it at my rundown here. But basically what I have argued so far is that dinosaurian herbivores, despite their absolute larger size, were not as adapted to the extent of large mammals as "whole plant predators" and to take the gardening analogy further- more like "pruners than chainsaws". But now back to meat eating...

Recent years have seen a revival of the importance of diverse predators, and especially top predators, in the health, vitality, and diversity of the earth's ecosystems. Not only do top predators keep down the numbers of other animals and prevent excessive overbrowsing and loss of microhabitats, but they also shape the ecosystem just by being around. While I went through some of the main points in top predator benefits in shark bay describing how tiger sharks maintain the seagrass banks, other studies are pointing to even more intricate and profound effects of top predators on ecosystem health.

Grasshoppers frightened by spiders affect whole ecosystem. Very interesting study. Basically researchers introduced "defanged" (harmless) spiders into enclosures with grasshoppers. Although the spiders could not predate on the grasshoppers directly the grasshoppers nevertheless went into a "fear mode" and concentrated on more carbohydrate rich parts of the plants. The "scared" grasshoppers were in a sense carb-loading (a little like stressed people?). Control studies of grasshoppers without spiders were more nitrogen enriched- they were taking in more amines/amides- basically concentrating on parts of the plant with more proteins.  Soil microbes, responsible for the transfer of nutrients from dead organics to plants, work at a higher pace with abundant nitrogen. Both the feces and the dead bodies of the "scared" grasshoppers showed a slower turnover rate of nutrients through soil microbes than the control group which was N-enriched. That is not to suggest the speedy turnover rate of the control group is more desirable- in fact quite the opposite- slow release of nutrients to plants is much more ideal in the longrun. What the study explicitly demonstrates is that predators have unexpected, and often dramatic, roles in their ecosystems.

All right, so once we realize the importance of predators in modern ecosystems it is not a stretch to imagine that these same ecological principals of "top down control" were also at play in the earth's past ecosystems. But all intact ecosystems (modern and ancient) maintain a dynamic equilibrium of top down (predators, parasites, virus, pathogens) and bottom up ( abiotic factors, rain, temp, plant availability, nutrient in soil) controls. What is a challenge to decode is the relative importance of each. Teasing apart these intricacies is hard enough in modern ecosystems- where the stuff is still alive- but trying to argue the relative importance of these controls in deep time is even more of a challenge, many would argue beyond the limit of our dataset...but let's go there anyways.

I am going to argue that theropods, as well as other archosaurian predators, exerted strong top down control on their respective Mesozoic faunas. This top down control was pervasive and systemic to dinosaurian faunas and on a level beyond that of modern mammalian dominated communities. The net effect of this top down control was to maintain biodiversity and, especially, floral diversity and health. Archosaurian predators were the "guardians of the Mesozoic garden" and kept plant predators at bay by not only active predation, but by maintaining a "climate of fear" that kept plant predators slightly stressed and always on the move.

Herrerasaurus and Eoraptor. wiki

Let us first look at how dinosaur reproductive physiology "set the table" (pun intended) so to speak for not only dinosaur success- but theropod success. It is now widely regarded that dinosaurs were R-strategist reproducers, as opposed to most large mammals which are classic K-strategist. R-strategist species are characterized by high reproductive output, small offspring, minimal to nonexistent parental investment in the offspring, independent offspring, and relatively early maturation and are not especially long lived. Generally speaking these species are "weedy" in the sense that they can quickly proliferate in disturbed ecosystems, especially when not at carrying capacity. K-strategists in contrast have few offspring which they invest tremendous resources into, are generally long lived, and maintain population at or near carrying capacity. Elephants, whales and humans are on the extreme scale of R-strategists all being long lived, large, and invest heavily in the young.

Now following from these differences between dino and mammal reproductive style are several corollaries which are important for future arguments.

1) Immature dinosaurs acted as "separate ecological species" from the adults (Codron, 2012). This creates a dinosaur fauna skewed towards either very large species or relatively small species- but few species in the middle range. In any given dinosaur population one may find a wide spectrum of different age/size groups represented with the population's modal size possibly quite smaller than the full size adult.

2) Unlike mammalian K-strategists, young dinosaurs- due to minimal ecological overlap with their parents- did not compete directly for food. This is opposite from the case with mammals or most modern aves as well- where neonates are directly stealing resources from the parents (i.e. milk and direct provisioning of food stuffs). These are resources the parents could have utilized for growing larger themselves- like dinosaurs did. And when the K-strategist finally weans its offspring they are full or nearly full grown and now direct competitors with the parents in their respective ecosystem.

"Feed Me!"

Alright then, dinosaurs, both predators and herbivores are reproducing at rates relatively faster than most modern birds and mammals. Obviously the vast majority of dinos are not going to make it- where do they go- down the gullet of theropods. A large, constantly replenishing prey base of immature dinos would have provided an easily accessible standing crop of food for theropods.

Like theropods, carnivorous mammals love to go after the young- they are easier to catch and not as dangerous as the adults. But contrast the situation in a mammal dominated ecosystem- for example the Serengeti plains- with what was going on in say a dino dominated ecosystem such as the Morrison. Each year every wildebeest cow has but one offspring- which are heavily sought after by any number of predators. Each year in the Morrison every Camarasaurus may lay several dozens of eggs- which turn into several dozens of baby sauropods- which feed several dozens of various theropod species. It can thus be argued that dinosaur dominated habitats would have provided a lot more easily caught, abundant protein packets in the form of baby dinos than mammal dominated ecosystems with much less abundant, more heavily guarded offspring. This important distinction is why dino habits would have been slightly more enriched in predators than mammal ones. And if you follow my line of thought you should also be reminded of my first Planet Predator where I discussed the hyperabundance of large predators on pristine reefs- central to that seeming ecological anomaly was the rapid reproduction of the reef fish prey base which constantly replenished itself even with 85% predator biomass. Again- I am not suggesting theropods were 85% of the biomass in their ecosystems. But what I would expect is predator prey ratios slightly enriched compared to modern mammalian predator prey ratios.

 And this is actually what we see in many dino habits with sufficient sampling.

A study by Horner found T-Rex to represent about 25% of ALL dino bones in the famous Hell Creek formation. In some locations it was equal or even greater than Edmontosaurus, supposedly one of its main prey species. Likewise in the Morrison, we have super abundant Allosaurus alongside a bevy of smaller and larger theropods. In the book Jurassic West predator biomass is estimated at 8.6%, on the extreme high end for mammalian communities. But the adjusted ratio for large predators is still 7.3%. Keep in mind though that sauropods (73% biomass), being substantially larger, would therefore not have been as numerous as one might expect compared to theropods. Trackway fossils in the Morrison bare this out, with theropod footprints being nearly as numerous as sauropod footprints by their data. Quite simply theropods were possibly only slightly less visible on the Morrison landscape than sauropods (barring grievous preservational bias).

And this is an important point for consideration- it would have been the visual threat of predation as much as the actual predation event itself that may have mattered in terms of how prey moved across the landscape.

We may never know to what extent theropods tackled prey larger than itself. But chances are any dinosaur that makes it to full grown status (predator or herbivore) has felt the pangs of being bit by a theropod several times while growing up. And there is no reason to doubt that the fear invoked while growing up remains in the adult. So if we apply sound ecological observations on the effects predators have on their prey- by predation or simply by presence- ( tiger sharks and dolphins, wolves and elk, spiders and grasshoppers) it is not unreasonable to assume theropods had profound impacts on herbivore movements/browsing intensity. The behavior of the herbivores under predator stress would consequently affect their prey- namely plants. And given theropods were relatively more abundant than mammalian predators (due to the abundance of baby dino apertifs), this "climate of fear" may have been ultimately greater than that in mammal communities.

And so what about corollary #2- that many dino species occupied distinct niches through their growth allomatry and this minimized competition between the adults and immature stages? Well if something wiped out the adult stage- some type of disease, lack of prey- there was always a younger generation ready to fill in the gap. Well this predicts two things in my mind- theropods ( and all dinos really) were very hard to get rid of- and herbivores got not break.

Well I will continue this post later- wrote more than I thought I would for this . Coming up next- theropod feeding envelope buoys up population and more on fishing theropods.

 Cheers

Pertinencia

Naish, Darren. Cristina Eisenberg's The Wolf's Tooth: Keystone Predators, Trophic Cascades and Biodiversity. Tet Zoo. http://scienceblogs.com/tetrapodzoology/2011/05/07/eisenbergs-the-wolfs-tooth/

Foster, John. Jurassic West. Indiana University Text, 2002.

Hone, D.W.E. & Rauhut, O.W.M. 2010: Feeding behaviour and bone utilization by theropod dinosaurs.
Lethaia, Vol. 43, pp. 232–244 http://gucas.academia.edu/DaveHone/Papers/164809/Feeding_behaviour_and_bone_utilization_by_theropod_dinosaurs

Daryl Codron, Chris Carbone, Dennis W. H. Müller, and Marcus Clauss. Ontogenetic niche shifts in dinosaurs influenced size, diversity and extinction in terrestrial vertebrates. Biology Letters, April 18, 2012 DOI:10.1098/rsbl.2012.0240

Horner JR, Goodwin MB, Myhrvoid N (2011) Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA PLoS One 6(2) doi:10.1371/journal.pone.0016574http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0016574#top

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This Island Earth Rundown

So for any new readers of da' salad I wanted to do a rundown of the blogposts that connect to the larger argument I started presenting in This Island Earth Part III Big Guy Bias.

This Island Earth Here by detailing the plight of the island fox on Santa Cruz Island I introduce many of the themes of this series: Predatory exclusion, intraguild predation, trophic cascades, island as a concept and evolutionary laboratory, herbivore pressure.

This Island Earth Part II Here I expand upon the damage wrought on the island by feral pigs on Santa Cruz Island. I discuss the boom bust cycles, parasite load, and vegetative changes due to the ecological imbalance. I then contrast the pigs ability to survive on the island with the former large herbivore the pygmy mammoth. I first suggest the size of a herbivore is not the only factor in the influence of that herbivore on its environment.

Mountaineering Moa: Coproecology of the Upland Moa Here I discuss the Upland Moa diet. Quite pertinent to my argument because now we have a large herbivorous archosaur family- that possibly put less stress on the plant community than the smaller mammalian community that replaced it.

In my post on the island Socotra and the desert cloud forests of Yemen and Oman I expanded upon the biological concept of islands as well as some more damage from mammalian herbivores.

How did multiple large dinos coexist on a relatively small island continent? Laramidia; the Great Dinosaur Species Pump

This Island Earth IIIa Big Guy Bias- This is where I first explicitly state my argument I have been building up to. Namely that dinos were less harsh on plant communities than mammals.

On This Island Earth IIIb Chainsaw or Pruners? I argue that the giant sauropod dinos acted more as "pruners" than modern elephants acting as "chainsaws". Ultimately I argue that sauropods were not designed as whole plant predators.

On Planet Predator I discuss the seeming ecological anomaly of a top down controlled pristine reef ecosystem with 85% predator biomass. Very important for future arguments in this series.

Shark Bay discusses the profound influence of the tiger shark on a variety of critters in a seagrass dominated community. Very pertinent as an argument for the benefits of large predators in ecosystems.

Planet Predator II Kem Kem goes into a deltaic environment seemingly dominated by giant theropods, fish, crocs but scarce dino herbivores. Very important for future issues of the series.

More to come- Parasites, pathogens, and pteridophytes Oh MY!!!

Planet Predator II: Kem Kem

(C) Troco. One of my fave recent images, read more about it here

Sometimes specific geologic formations take on a special, almost mythical, aspect to them. The Kem Kem beds of Morocco and Algeria definitely have that "special" quality to them. Documenting a roughly 10 million year span of the Cenomanian in the early Late Cretaceous, the formation represents several transgressive and regressive cycles of a coastal system on the southern Tethys Sea. Generally referred to as a "deltaic" environment, the Kem Kem contained a variety of environments within it- including offshore rudistid reefs, mangrove type forests, tidal rivers, floodplains and estuaries. But everywhere water was a dominant feature. The water was not necessarily all from precipitation- climatic models for this time predict arid conditions towards the equator- and rainfall when it occurred was episodic and monsonal. Picture the Kem Kem more like Arnhem land in the Northern Territory of Australia than the Amazon delta. No, the large amount of water was due to a very low gradient of land approaching high epicontintental seas.

Arnhem Land, Northern Australia

Ocean bound water slowed down and intermingled with waters from the Tethys creating a massive land sea interface on a continental scale- the magnitude of which we do not see today- perhaps the Sunderbans of India come close.

Sunderbans, India

Of course given this immense land/sea mosaic we would expect mangrove forests to dominate- except mangrove trees, which are angiosperms, had not yet evolved. Instead we had forests of Weichselia reticulata, a halophytic (salt tolerant) tree fern that was likely the dominant member of the intertidal floral community. Also common would have been various halophytic members of cheirolepidaceae- an extinct order of diverse coniferous plants- such as Frenelopsis. Herbaceous ferns, horsetails, and charyphytic algae rounded out the plant community.

Weichselia reticulata

Frenelopsis sp.

Thriving amongst these various watery microhabitats was a diverse assortment of fish. Amongst the more notable fish were a variety of medium to large sharks, coelecanths, bowfins, elasmobranchs, tarpons, lungfish, and even planktivorous paddlefish types. Adding to the diversity was a variety of marine reptiles, pterosaurs, turtles, crocodiles, snakes, and lizards. In a rather extensive review of the Kem Kem beds distinct faunas emerged relating to sea level and showing several biogeographic affinities to other marine/terrestrial provinces.

(c) Brian Engh

Of course what attracts the most attention, rightfully so, is the dinosaur remains from the Kem Kem. While several sauropods were present and ornithopod remains are sporadic as well what the Kem Kem does offer is a rather large assortment of multi-tonne theropods. And these guys were literally "whale sized". 

Kem Kem Theropods

So let's disregard the two smaller grey theropods- they are "problematic" to say the least. That still leaves you with the respectably sized Deltadromeus (green), gargantuan Spinosaurus (black), massive Carcharodontosaurus (red) and... who is that guy in blue? The guy in blue represents a potentially even more massive, as yet unnamed, basal carcharodontosaurid represented by basically a chunk of its braincase. Read about it here.

So whaaaa... how, ecologically speaking, did this suite of massive predators coexist? Especially in light of the fact that herbivorous dinos in this ecosystem appear to be less diverse/abundant?  (I don't buy completely the idea of "sampling bias" that some argue- although some truth to it is probable it does not erase the fact of four very large predators) Especially seen from the perspective of large mammal dominated ecosystems the idea of four contemporaneous multi-tonne predaceous dinos seem preposterous...

Well let's look at the ecosystem from the perspective of the most dominant feature present- water. Modern mangrove ecosystems are very productive places. But even in modern mangroves we don't really see anything analogous to say a seven tonne spinosaur tromping about. What was different in these areas from the present? Let's look a little lower on the food chain.

What really sets the Kem Kem apart is the abundance, diversity, and wealth of relatively large fish. If we look at modern large coastal fish we can draw some rough parallels. Many coastal fish do not typically stay in a single microhabitat. Barramundi, able to tolerate a variety of salinities (euryhaline), is known to descend downstream from its inland rivers into estuaries/tidal flats to breed.

Barramundi sp.

Tarpons (genus Megalops) are also euryhaline except that the fry are born in open ocean and then move in progressively closer to shore and sometimes into fresh water as they mature.

Tarpon (Megalops)

And then you have monstrous guys like the sawfish:

Some species can reach 23 feet in length and several tonnes in weight and all species can easily go between salt and freshwater habitats. And the Kem Kem is well known for having its own giant sawfish, the 8 meter long Onchopristis, often posited as a fave prey of spinos.

So what can be gleened from all this? Well all of the above fish are large, tropical, and are known for travelling between, among, and throughout various nearshore/offshore, estuarine, upriver habits in all kinds of combinations- seasonally or at will. The Kem Kem, with an even greater variety of large- most probably euryhaline- fish, was likely the focal point of energy transfer from both offshore, local, and inland water ecosystems. Combined minimal to nonexistent seasonal change, high epicontinental seas, and abundant primary productivity and you have a fish monger's dream.

Russel (2009) suggested fish were the basis for the food chain- culminating in the large predaceous theropods. I tend to agree with this statement. Although the case for spinos being sushi lovers is pretty iron-clad at this point- what about the several large carch species as well as Deltadromeus? Well, just because they have no clear adaptations towards piscivory like spinos do does not mean that fish- or aquatic organisms in general- were not a mainstay of their diets. Plenty of large typically terrestrial predators habitually take advantage of water based prey- jaguars, various bears, wolves to name a few- especially during seasonal migrations or when drought/geography funnel water prey into easily caught situations. Various crocodile species are well known for predicting fish movements and taking advantage of specific sites where fish are easily caught. Theropods, by no means brainiacs, were at least as cunning as crocodiles at predicting spots to opportunistically take advantage of certain hard to get prey items.

And even if the large theropods aside from spinosaurs were clumsy fishers don't forget about stealing your fish dinner!!! Indeed this form of piscivorous kleptoparasitism is rampant in extant theropods.

Maybe carchs habitually followed spinos and stole their fish...Maybe the efficient fish hunting spinos were key to the success of the other theropods- much as wolves indirectly benefit bears and other scavengers through their kills.

Remember the first Planet Predator I did a while back about the seeming paradox of a predator dominated ecosystem? One of the keys to the sustainability of such an ecosystem with 80% predator biomass  is that the prey base rapidly replenishes itself to sustain the losses. Well in the Kem Kem we may actually have a parallel situation with numerous fish species- many possibly rapid reproducers- supporting a top heavy cast of large predatory fish, pterosaurs, crocodiles, and theropods. Did the biomass of theropods and other top predators approach 80%- probably not, especially in light of the fact that the dinos were probably endothermic- but there is every possibility that it was higher than you might expect in a typical terrestrial plant>herbivore>carnivore pyramid. Here's why.

1) Abundant, rapidly replenishing fish prey base. The low continental relief combined with high consistent temps, epicontinental seas and productive mangrove/deltaic environment doubtless supported large nurseries of small fish and an unparalleled diversity of large, euryhaline fish. These fish likely moved between all environments distributing nutrients accordingly.

2) The predators themselves. Take a look at the pic in the beginning of the post. What it depicts is a large adult carch that has used a natural rock formation on abeach to pin down three immature spinos and kill one of them. A very realistic example of intraguild predation. Then go review this article and read about intraguild predation in raptors and monitors. Its quite possible intraguild predation was par for the course in these theropods. The theropods, especially given their reproductive capacity and size envelop from hatchling to adult, were partially acting as their own prey base!

3) Nary a herbivorous dino around. Its quite possible that the theropod diversity and numbers in the Kem Kem, buoyed up by abundant aquatic resources, were an active deterrent to abundant herbivorous dinos- despite the abundance of plants in these mangrove/deltaic conditions. Much like we saw in Shark Bay where the mere presence of tiger sharks was inhibiting foraging efforts by dugongs, dolphins, and cormorants- the abundance of theropods in the Kem Kem was simply not worth the effort for dino herbivores. So how did the lack of dino herbivores bolster theropod numbers? Well if the dinos were not eating the plants that means inverts were taking up the slack- insects, millipedes, snails, crabs, shrimp. It also means more decaying vegetation- which enriches the waters further- more food for the fish. In either case- more bugs or more nutrient rich water- the fish are happier. The fish are happier- the theropods are happier as well. The exclusion of abundant dino herbivores allowed a feedback loop which benefitted fish and theropod.

4) Spinosaurus was key. Of the four large theropods Spinosaurus was the only one specialized towards piscivory (crocodile jaws, pressure sensing snout, gaff like hand claws). The other theropods were likely not as efficient fishers. They may have benefitted from the presence of spinosaurs by either stealing or scavenging their catches or using spinos directly as prey in lieu of herbivorous dinos. In either case spinos were the keystone species- the presence of which affected all others.

Of course I could be wrong. Perhaps carcharodontosaurids were true landlubbers and hated sushi. Perhaps the predator bias is actual and herbivorous dinos were more common and diverse than thought.   Perhaps spinosaurids didn't eat much fish at all- but swam offshore to feast on rudistid clams...perhaps

Nah, I like the idea of a theropod dino dominated habit thriving on fish/aquatic animals. Herbivorous dinosaurs need not even be involved in this food web. Aspects of this type of ecosystem are not unparalleled. If we look to pristine reefs with tremendous top predator biomass we see potentially analogous characteristics. And if we look at the type of exclusionary actions abundant large predators impose on other animals (tiger sharks in Shark Bay, wolves in Yellowstone) this situation in the Kem Kem is not without precedent.

And now just for fun...

I imagine the "food journal" of an adult Carcharodontosaurus in the Kem Kem would go something like this...

Today I woke up and sniffed out the remains of a 5 meter sawfish hauled to shore by some spinosaurs from the night before. Left a little hungry but slept the rest of the warm day. Woke up at 3 am to the sound of several large stomatosuchid crocodiles scooping up schools of fish in some shallow water.

I knew the bay they were in and I knew if I could approach from deeper water I could probably snag one. I did it! - several of the larger 6 meter guys got away but I snatched up a good 4 meter croc which slid down my gullet in one swallow... Slept for three days in a row, I have not seen a carch larger than myself (about 13 m and 4 tonnes) in several months so I feel pretty confident in napping whenever and wherever. Several years ago  at about 10 meters I had to watch out for larger carchs as well as large adult spinos- my left arm was pulled off by a big bruiser of a spino at about 16 meters, Now even these guys leave me alone and I routinely steal fish from spinos up to about 14 meters. I start making my way upriver as it was about this time last year that large schools of coelecanth congregated to breed in some pretty dense horsetail beds where the water is more fresh tasting (I do have salt glands to deal with drinking salty water). Even if I don't catch a fish chances are I could steal one from the abundant spinos that congregate for the fish- or even kill a small spino if given the chance. Along the way I cross some open dry terrain and smell my old nemesis Deltadromeus. Until I was about 8 meters long these guys really gave me a hard time.

Pretty much all of my clutch-mates were gobbled up by these annoying speed demons. They were always faster than me and I would generally back myself into a corner to avoid their annoying but not very strong bites. Now I hunt them whenever I get the chance. They tend to avoid the deeper waters and denser forests where their speed is neutralized but I have got them before- usually in the chaotic monsoon when I can sneak up on 'em undetected. I finally reach the horsetail beds after several days travel. Over the years I have refined my hunting technique for these strong, maneuverable fish. I know of one spring fed pool, clear and deep where they like to breed. Leading to it is a small channel, only about 3 meters across and surrounded by dense cycads on either side. I set up my ambush site here and catch the 50 kg fish pretty consistently over several days. On the third day I notice a sound I had not heard for several months- a herd of rebbachisaurus sauropods.

I used to hunt these guys all the time before I discovered its a lot easier to be a hooligan in the delta. Even a midsize one can pack a whallop with its tail and I've been injured by these brutes before. Never the less I launch into an attack on one about the same size as me and deliver a good slashing bite to its left front leg- making it limp. Soon it will fall behind the herd and I will have a good feed of sauropod- a meal I have not enjoyed in several months!!!

Cheers!!!

Mawsonia libyca, 3 meters long, next to modern coelecanth & girl

Pertinencia

Cau, A.; Dalla Vecchia, F.M.; Fabbri, M. (2011). "Evidence of a new carcharodontosaurid from the Upper Cretaceous of Morocco". Acta Palaeontologica Polonica, in press. doi: 10.4202/app.2011.0043.

Loeuff, et al. Vertebrate assemblages from the early Late Cretaceous of Morocco: an Overview. Journal of African Earth Sciences. 2010.

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Sinocalliopteryx gigas: "Get in My Belly"

Stuff just keeps coming out that I can't ignore...

Here is the abstract:

Two skeletons of the large compsognathid Sinocalliopteryx gigas include intact abdominal contents. Both specimens come from the Jianshangou Beds of the lower Yixian Formation (Neocomian), Liaoning, China. The holotype of S. gigas preserves a partial dromaeosaurid leg in the abdominal cavity, here attributed to Sinornithosaurus. A second, newly-discovered specimen preserves the remains of at least two individuals of the primitive avialan, Confuciusornis sanctus, in addition to acid-etched bones from a possible ornithischian. Although it cannot be stated whether such prey items were scavenged or actively hunted, the presence of two Confuciusornis in a grossly similar state of digestion suggests they were consumed in rapid succession. Given the lack of clear arboreal adaptations in Sinocalliopteryx, we suggest it may have been an adept stealth hunter.

Art by Cheung Chungtat, from Xing et al., 2012.

Well a couple things can be taken from this:


1) Dromaeosaurs (i.e. "raptor" dinos) were not always the proverbial kick-boxing ninja super badasses in their respective environments. Remember this is not the first time they have been posited as prey for another dino- the baby dromaeosaur in the oviraptor nest? Indeed the last couple of years has seen a steady diminution of their supposed "hyper-predator" attributes. The clan has gone from JP styled pack hunting predators of larger dinos who killed with disemboweling kicks to solitary hunters of small to medium sized game which was ambushed and pinned down with those raptorial claws.


2) If the stock in raptor dinos has been falling as of late, the compsognathid clan has been quietly rising in the dino-predator sweepstakes. Generally small bodied specialists Sinocalliopteryx gigas was the giant of the family and hints at possibly an unrealized diversity of sizes in this family. And the fact that these dinos are often found with varied, often agile, prey items swallowed whole in their bellies- in this case raptor dinos, ornithiscian legs, and two birdies- says that they were super badasses and quite possibly ninja-sneaky. Don't forget that compsognathids are now thought to be cousins to tyrannosaurids

3) Intraguild predation may have been rampant in theropod dinos. We will talk more about this in upcoming posts but much evidence is pointing to theropods loving to eat other theropods. Intraguild predation is defined as the consumption of a predator who kills another predator that has at least some commonality in prey base. In the above example Sinornithosaurus, the dromaosaur consumed by the Sinocalliopteryx, likely ate a lot of the same prey species- such as the confuciusornis birds in the Sino's belly. By eating a competitor an intraguild predator is both gaining the nutrients from said body but also reducing potential competition for prey, nesting, ambush sites etc.etc.

Pertinencia

Xing L, Bell PR, Persons WS IV, Ji S, Miyashita T, et al. (2012) Abdominal Contents from Two Large Early Cretaceous Compsognathids (Dinosauria: Theropoda) Demonstrate Feeding on Confuciusornithids and Dromaeosaurids. PLoS ONE 7(8): e44012. doi:10.1371/journal.pone.0044012

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0044012 

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Shark Bay

Ok, Ok, Ok- after the throngs of requests for a new post from my minion(s ?) I got something for ya' all. Honestly I just started Calculus and Organic Chemistry so about a post a week is how it will be for awhile.

Because we are at the tail end of summer and shark week just went down- all things sharky are on my mind. But this post also serves a dual purpose of acting as a bit of a prologue to my next installment of This Island Earth- where I will be talking about the importance of large predators in a healthy ecosystem. Now the classic study that has recently came out in these regards is the ecological cascade that occurred with the reintroduction of wolves into the greater Yellowstone area. Long story short the return of the wolf allowed for a diversification of songbirds, Willow/riparian vegetation, scavengers, and beavers. Read about it here.

Now you might already be familiar with that ecological parable, if not be sure to check it out. But I want to focus your attention to another, lesser known, analysis of the effect of a top predator on a ecosystem- tiger sharks (Galeocordo cuvier) in the seagrass beds of Shark Bay western Australia.

Seagrass beds are a little appreciated, but highly productive, marine ecosystem. Along with mangroves, seagrass ecosystems represent one of the few examples of flowering plants (angiosperms) successfully invading the marine realm- complete with submarine pollination. Over 60 species exist worldwide in tropical/temperate seas and are important primary producers where they occur- providing food and habitat for a plethora of critters. They only exist on sandy bottoms in the photic zone and, like coral reefs, are highly sensitive to perturbations in nutrient levels. Too much nitrogen/phosphorous stimulates algae growth in the water column- blocking out the sun- and eventually the system degrades to a algae dominated soup. Probably does not surprise you to learn that seagrass is declining worldwide. Oh yeah, and seagrass might just be the savior to coral reefs.

Seagrass is also important as an ecosystem engineer. The large beds inhibit tidal and storm surge as well as building up on itself creating vast shallow beds with tremendous primary productivity. The effect is basically that of an "underwater grassland" and the analogy is apt.

A UNESCO world heritage site, Shark Bay contains the largest example of an intact seagrass dominated ecosystem in the world. Much like the coral reefs I talked about here, Shark Bay provides a unique opportunity to study a relatively pristine environment- less than 1000 people inhabit the 1,500 km of coastline that the bay encompasses. Although the bay is huge, covering 10,000 square km, the average depth is fairly shallow at about 10 meters owing to seagrass' ability to modify its own habitat.

Shark Bay, western Australia

Of course a habitat of this type is bound to attract some animal life and Shark Bay does so in spades. The bay is home to about 10,000 dugongs as well as abundant bottlenose dolphins, pied cormorants, sea snakes, loggerhead and green sea turtles. And lording over all of these is the brootal tiger shark. How the tiger shark affects these species- both by preying on them directly and by just simply being around- is the crux of this article.

Don't let the pop science mantra of "mistaken identity" fool you- the tiger shark has and does actively eat humans- and just about anything else it comes across in the sea, earning the dubious nickname "trashcan of the sea". It just happens to be that in aptly named Shark Bay mammals, birds, and reptiles happen to be on the menu in addition to the usual fare of fish and inverts. How these interactions affect these critters and the larger ecosystem has begun to be illuminated through the Shark Bay Ecosystem Research Project.

The dugong (Dugong dugon) is technically the only herbivorous marine mammal (close relative the manatee is not 100% marine) and is highly dependent on seagrass- often eating both the blade and root of the seagrass- acting as a "whole plant predator". What the researchers found is that, due to tiger shark threat, the dugongs in Shark Bay avoid foraging in the exposed middle of seagrass banks even though this area has the most nutritious grasses. Instead the dugongs, as well as the green turtles, concentrated their foraging efforts in the edge of seagrass banks- where the threat from tiger sharks was minimal. By establishing test enclosures the researchers observations were supported.

Outside enclosed area seagrass grazed to nothing

Interestingly both bottlenose dolphins and plied cormorants avoid areas where dugongs are plentiful, because tiger sharks are plentiful there as well. And these habitats are rich foraging grounds for the birds and dolphins due to the abundance of small fish, but simply not worth the risk. Don't let the image of dolphins as "people of the sea" fool you- large sharks commonly catch, kill, and eat dolphins (u r warned violent here)- and have tactics to do so. So in effect, the presence of dugongs actually discourages both pied cormorants and bottlenose dolphins.

Pied Cormorant

To add another element to the story, small seagrass consuming fish such as striped trumpeters may be winning out big because tiger sharks are keeping their predators (cormorants/dolphins) and competitors (dugongs) at bay. How and if these fish inhibit seagrass cover is yet to be determined...

What we can see here is that tiger sharks both directly and indirectly affects the foraging behavior of common prey items (dugongs) and less common prey items (dophins, cormorants) which has repercussions throughout the system. Tiger sharks are indeed the guardians of the seagrass banks.

Stromatolites. Shark Bay Australia

One final tid bit. Paleo folks might also know about Shark Bay because of stromatolites, which thrive in the hypersaline shallows of Shark Bay. Indeed hypersaline Shark Bay is the only known occurrence of these ancient accretionary cyanobacteria biofilms. Shark Bay maintains a salinity higher than the neighboring open ocean because it is so shallow and the high evaporation rates of hot subtropical Australia concentrate salt. As I mentioned earlier, it is the seagrass banks that create this extensive shallow gradient. So if the seagrass creates the environment for hypersalinity, which allows stromatolites to persist, and tiger sharks preserve the seagrass banks- can we say tiger sharks preserve the stromatolites?

Any excuse to post pics of cute girls will be used

Cheers!!

Pertinecnia

Shark Bay Ecosystem Research Project

http://www2.fiu.edu/~heithaus/SBERP/projects/index.html

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Planet Predator

While Shark Week was busy finding out what Megaladon could bite through, other more meaningful studies escaped mention in their week of carnage. One particularly relevant bit of knowledge gleaned from studies of the few pristine reef ecosystems left is that sharks- and other predatory fish like jacks and groupers- dominate these systems in terms of biomass. They seem to break all the text book food chain-pyramids we have come to understand as to how normal ecosystems works.

These coral reefs have inverted the classic biological food chain. How have they done this? And why does it matter that the vast majority of coral reefs are no longer like this? Surely having such predator dominance, 85% top predator biomass in some Pacific atolls, is not sustainable?

A key to this seeming ecological anomaly is differences in reproduction capacity and maturation rates. Sharks have relatively low reproductive rates and maturation rates while their reef fish prey base have quick maturation rates and reproduce prolifically. Despite their constant losses from the predators the reef fish are able to absorb the losses through quick reproductive turnover.

And as it turns out, the reef communities studied with top predator dominance invariably had healthier corals with abundant coral recruitment and greater diversity levels overall than those with less abundant predators- they were also more resistant to perturbations in temperature, pollution i.e. coral bleaching. But because of their slow reproductive rate, fishing- even at subsistence levels- has a more dramatic and long lasting effect on shark populations than other fish. And when the sharks are gone coral communities tended to look like this for a while:

Looks pretty inviting, doesn't it? In fact the above view may be what many of us picture a pristine, healthy reef to look like. At the very least it is the type of reef that is inviting to recreational diving. But a growing body of evidence is suggesting that many coral reefs like the one pictured above are in a state of decline for their lack of large predatory fish.

For reasons not yet fully understood picturesque reefs like the one above are transforming from coral/fish/invert dominated systems to algae/bacteria/planktivorous small fish dominated systems in the absence of large predators.

 So while tourists might prefer to swim in a reef swarming with colorful reef fish, they are in fact swimming in a reef on the edge of collapse. Although a little more intimidating a reef like the one below with slightly hungry sharks cruising past always on edge reef fish offers a view of a much more healthy, intact reef ecosystem.

So if you took the time to watch any of the rehashed bits on shark week you should take the time to watch this clip below and really learn something about sharks and that ecological buzz phrase of "top-down control".

Pertinencia

http://www.ted.com/talks/view/lang/en//id/854

Various authors. Baselines and Degredations of Coral Reefs in Northern Line Islands. PloS One
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0001548

An Uneasy Eden. Nat Geo
http://ngm.nationalgeographic.com/2008/07/kingman-reef/warne-text

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Trogloraptor: Once Again an Invert Steals a Cool Name

I honestly was planning a post on spiders but then this popped up which is some pretty amazing-cool news anyways...

Trogloraptor ( cave robber) is a new genus and species of a new family Trogloraporidae discovered by citizen scientists in some privately owned caves in southern Oregon (Grant's Pass area) and also in thick undergrowth in old growth redwood forests of northern California. This is only the third new spider family discovered in the world since 1990 and the first in North America since 1870! These kinds of discoveries don't just happen every day folks!!!

C. California Academy of Sciences

For a temperate spider it is actually quite large- about 1.5 inches long or easily able to cover a silver dollar. It has several features suggestive of ancient heritage and is distinguished by some rather gruesome looking claw/fang type grapplers, check out pic:

California Academy of Sciences

So in 2012 whole new families of spiders are being discovered in the most populous state in the US by citizen scientists who then collaborate with a major institution to bring to light this find. Unexpected and cool.

But what is not surprising is that this find would be from the unique coastal forest belt from northern California through British Columbia. Now there is some very unique habitats, full of all kinds of nooks and crannies- chopped up by big rivers, mountains and forests- just ripe for unique cryptids, relicts, and speciations. What other discoveries await us from this region?

Deep, old growth redwood forest do have a certain 'cavelike' quality to them- pretty dark, cool, dank and wet. I can see how these spiders might feel comfortable in both caves and redwood undergrowth. One also wonders if they habit the hollowed out insides of fire burnt redwoods- seems like a good, cavelike little microhabitat for the Trogloraptor.

Peace out.

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