Cephalopod: It's What's For Dinner

Much of this post was inspired by a discussion I had in the comments over at Jaime Headen's heady blog the bite stuff about Rhamphorynchus muensteri.

When I lived in the Bay Area one of my favorite past times was exploring Asian food markets. Not so much to shop for food (though they often had killer deals on beer) but just to get a kick out of the seafood selection. Seriously, the amount and sheer variety of oceanic critters on display at these places is astounding- kind of like going to an aquarium without feeling guilty over the imprisoned killer whales. All sorts of fish, cute little dried sea horses on sticks, crustaceans, molluscs- hell even dried jellyfish snacks (or jellies if you want to be PC)- were there either canned, dried, salted, butchered or even alive.

To western palates, and more specifically American palates, this seafood bonanza highlights how limited our diets really are in terms of amount of oceanic phyla consumed. And one group that I want to focus on today which is in no short supply in these Asian markets are cephalopods- the "head-footed" clan of mollusks that includes octopi, squid, nautilus, and cuttlefish. You western readers might be thinking: squid are not so exotic I enjoy a bit of calamari now and again. Yeah, you eat breaded, fried calamari rings- wowee. Go check your cabinet right now- how many cans of squid with ink do you have? How many cans of tuna do you have? Probably a lot more chicken of the sea, no? Us westerners have a very fish biased diet in terms of seafood choice. And it is this fish bias- a certain penchant for backbones - that I want to speak of today. And ultimately discuss how this tendency to look towards all things fishy may actually imbue our interpretation of certain long ago extinct beasties and how they lived.

Humboldt Squid. Bill Erhardt (c). Baja CA 2008

Kinda creepy looking, no? These are Humboldt Squid, Rojo Diablos- Red Devils, scientific name Dosidicus gigas. They are feeding on pelagic red crabs and it almost looks like a type of cooperative hunting is going on here- a behavior that has been attributed to these guys before. In recent years this species has been undergoing significant range shift, moving from a stronghold in the Sea of Cortez right up the coast of California sometimes as far north as Alaska. And this expansion speaks to a worldwide increase in squid numbers. It is now widely regarded that squid biomass exceeds human biomass and may be making serious inroads on fish biomass supremacy. Why? We have over-harvested many of their chief predators- billfish, tuna, sharks. But perhaps more importantly intrinsic changes in the ocean itself may be spurring on an increasingly tentacled ocean ecosystem. A paper on the Humboldt Squid, Combined Climate and Prey Mediated Range Expansion of Humboldt Squid, suggest expansion of an oceanic hypoxic layer allows refugia from predators and unfettered access to areas it had formerly been nonexistent. Another study comparing the differential ability of various fishes, cephalopods, and zooplankton to survive oxygen minimum zones comes to a similar conclusion. So when it comes to areas where oxygen is limiting, cephalopods seem to outcompete fish. Why this is so is less clear to me. Perhaps it has something to do with their chief form of locomotion via jet propulsion and the amount of water they can pump through their gills through their mantle?

Never the less if we paint with very broad strokes cephalopods seem to be winning in warm, oxygen deprived waters. I am looking at you Mesozoic oceans. Indeed in Mesozoic oceans we have not only squid, including big ones, but ammonites and belemnites. A very tentacle ridden, cult of Ctulhu styled scuba dive you might have if you explored the Western Interior Sea. Not only were cephalopods abundant and diverse but the work of the Jurassic Spitsbergen Research Group shows that fish were ecologically insignificant in some Mesozoic oceans. If you don't know now you know, calamari in form or another was a common food for aquatic predators during the Mesozoic.

And here is where I want to tie together the whole cultural bias against tentacled stuff and how our view of many deep time marine predators might be skewed by our fishy bias. Piscivore, say it with me, pis-civ-ore, one who consumes fish. If you are a animal/paleo-geek like me you are surely familiar with the term. But what is the name of a squid eater? I actually did not know when I asked myself this question but it is teuthophage, a word not so commonly thrown about as much as piscivory. Ok, so big whoopee if you can eat fish you can eat squidy type stuff too can't you? Well maybe in some cases, maybe not so much in others...

Do Brown Pelicans Avoid Squid... and if so Why?

Whenever I get a chance I love to talk to fishermen to glean any kind of info I can from them. Now we all know what they say about fisherman's tales but sometimes they will give you some info that perks your interest. And one of the more interesting bits I have heard on several occasions is that brown pelicans, Pelecanus occidentalis, assiduously avoids squids. And where I live on the coast of California  this struck me as a bit odd because we are having record hauls of market squid, which form huge shoals, and pelicans are ubiquitous here. Maybe these admittedly anecdotal accounts speak to a larger truth -why avoid such a tasty nutritious treat? As the you tube video above suggests maybe pelicans are not so dissimilar to humans when it comes to food. If you have a bad experience with a certain food type you are not apt to repeat that same mistake. And when a plunge diving pelican gets a beakfull of squid in it's gular pouch

and realizes that these creepy little things ain't anchovies and sucker on to my skin, block my throat, and some even have little switch-blade suckers that draw blood- it is a mistake not soon to be forgotten. And now go back and look at that gif of the unfortunate cat with a face-full of octopus. I was not trying to be cute there but actually trying to illustrate what works and what does not work to be a teuthophage- especially an air breathing one. Just because you can catch and eat fish well does not mean you can catch and eat cephalopods as well. Or you can put it this way: piscivores are not always teuthophages, but teuthophages can always be piscivores. If you are a teuthophage you can tackle tentacled prey in a couple of ways; beaked whales are very much larger than their squid prey and simply inhale their prey whole; sharks, pinnipeds, and predatory fish have the dental equipment/bills to dismember squidy prey on the spot negating the tentacled counterattack; sea birds that eat squid have longer bills, sometimes have ridged tongues for killing. Something like Pelagornis comes to mind when imagining the penultimate avian teuthophage. Ultimately when the cephalopod and the teuthophage are more equally matched in size- the would be predator wants to have a long, sharp mandible to keep Mr. Squiggly at arms length. And this is double important when the teuthophage in question is an air-breathing tetrapod.

Mesozoic Calamari

Now with the perils and pitfalls of teuthophagy in mind let us revisit the Mesozoic and remind ourselves that not only were there often abundant squid, but also shelled ammonites/belemnites. And given that many ammonites may have indeed been plankton consumers and were so common that their fossils constitute index fossils I want to pay special attention to them. Predation scores left on the shells of ammonites are well known, mosasaurs usually indicted as the culprit. And it is not too hard to imagine the heavy maw of a mosasaur, pliosaur, robust snouted icthyosaur or sea-going croc having a go at these shelled delicacies.

Does this imply the more daintier snouted icthyosaurs, plesiosaurs, elasmosaurs, and other more slender snouted/toothed marine predators simply left ammonites alone? I would argue no- they simply had other ways to retrieve the flesh and leave the shell alone. A quick snap at an exposed tentacle by any one of these critters at an ammonite. Establish a good grip. And then the predator can either shake off a piece, or... ready for this... go into a death roll pulling off a tentacle or maybe even yanking out the whole squishy body. And I know you love death rolls, now just imagine a 14 meter Elasmosaurus, grabbing onto the fleshy part of a large ammonite,  and spinning on it's own axis with a two tonne body creating tremendous torque funnelled down that long neck yanking the

doomed ammonite from it's shelly home....
I once saw a documentary on Moray eels and a similar death spin tactic was used by the eel to rip off a tentacle from a much larger octopus.

Now keep in mind that I am not suggesting fish and other critters were not routinely consumed by marine reptiles. The fossil evidence of stomach contents, coprolites tells us specifically that fish, turtles, pterosaurs and even benthic invertebrates were common dinner fare for some of these guys. In fact for the record, all things being equal, I automatically assume a generalist diet for just about any predator- especially marine reptiles. For me proving an obligate specialist diet requires more of a burden of proof than a more opportunistic/generalist strategy. What I am suggesting is that where we have an abundant prey base of shelled cephalopods- we should expect predators on hand to consume them and start looking for ways that they accessed such prey.

But it is also worth mentioning that fish remains have a better preservational potential in coprolites/gut remains than cephalopods because, you know, skeletons. And this bias would be even more pronounced if predators were just ripping off chunks and isolated tentacles from cephalopods.

Pterosaur Ptroubles 

As many have learned to their peril, putting forth thoughts on pterosaurs on the interwebz is a touchy subject. But since it was a discussion of Rhamphorynchus that started this whole train of thought here we go.

Rhamphorynchus. wiki

OK if you are up to date on pterosaur paleoecology then it should not be news to you that the traditional "deranged sea-gull" interpretation of pterosaur lifestyle has been laid to rest for the majority of pterosaurs. If you don't know about this change GTFO and go buy Mark Witton's book. But I want to talk about those oceanic pterosaurs for which a piscivorous lifestyle has been retrieved. Starting with our friend Rhamphorynchus muensteri I am intrigued by the hooked jaws and procumbent dentition- especially towards the tip. Remember what happened to the cat with the octopus on its face- if you are handling tentacled prey you want to keep all those moving parts away from your face. Expectations met. And those weird teeth and hooked jaw tip? My interpretation is that such a design was great for digging into shelled/coiled ammonites. Again they are not busting through the shell but probing into it. Do we have any modern analogues? Snail kites, Rostrhamus sociabilis, comes to mind- feeding almost

Snail Kite. Cornell Education

exclusively on apple snails, scooping out the flesh and leaving the shell. But bear in mind that although such a lifestyle today seems overwhelmingly specialized- in the Mesozoic ocean with scores of shelled, pelagic molluscs such a penchant for molluscivory may have been more widespread. Oh yeah, I almost forgot, Dave Hone does have some evidence of cephalopods in the diet of Rhamphorynchus as well from 2013 if you google it you can find reference...

Anhanguera blittersdorfi. wiki. Ghedoghedo

When you start to look at Ornithocheirids the pattern continues- long jaws with a spear like tip rosette of teeth to keep struggling tentacles away from the eyes/ears/throat. Also good potential for deep probing into shelled cephlapods- killed or scavenged. Again I am not arguing that pterosaurs did not eat fish also, but for me many of these adaptation of "piscivorous" pterosaurs are optimal for a teuthophage as well. And yes many of these guys lived at inland lakes lacking cephalopods- dual functionality for fish and cephlapods would conserve the design.

Pteranodon. Smokeybjb. wiki

And I want to leave you with the classic "piscivorous" pterosaur group the Pteranodontids. For me I imagine these as very special oceanic predators/savengers of late Cretaceous open ocean. Often compared to albatross in terms of flight ability I would venture to say the comparison also extends to their ecology. Their long, slightly upcurved, sharp fore-cep like eduntulous beaks in my mind appear optimal for snatching wriggly, tentacled things and also for probing deep into the chambers of ammonites. Again, not saying that they were wholly dependent on cephalopod food, just that the ecological conditions of their time- with loads of such prey- suggest to me that there was ecological imperative to access such foods.

Matt Martyniuk. wiki

Night was falling on the Western Interior Sea. And with this change in light conditions, the largest and oldest continual migration in the history of the planet commenced- the vertical migration. A myriad of creatures that took shelter in the darker, oxygen deprived water during the day to escape fishy predators of the sunlit upper realms commenced their nightly rise in the water column. And the most visually conspicuous members of this guild were cephalopods. 

Belemnite shells

Shoals of squid-like armored belemnites darted about, making a go at some of the larger bits of zooplankton. Large and predatory squid rose from the depths and aggressively preyed on whatever they could overcome. Their supercharged metabolism and growth rate a necessary corollary of their annual lifespan- growing from barely visible larvae to several hundred pounds in weight in about 1 year. And most dramatic of all were the numerous and diverse ammonites with the ability to effortlessly change their position in the water column through manipulation of the gas concentrations in the septae of their coiled shells. Despite the imposing physicality of the ammonites many of the largest types were harmless filter feeders- able to grow so large by sifting through the planktonic soup of the Cretaceous ocean. But these big boys, the largest ammonites, were not alone- night was also the time for mosasaurs, their chief nemesis, to ramp up their activities as well...

And with the commencement of this strange and scary nightwatch an aerial division also ramped up it's activities as well. An old Pteranodon sternbergi had reached a size and level of experience that distinguished it from younger and smaller pteranodons. He no longer squabbled with flocks of ocean birds and smaller pteranodons over small bait-fish balls and cephalopods but sought bigger fare- the largest cephalopods the ocean had to offer in fact. And he secured great big calamari steaks not by killing them himself (although he did sometimes dispatch disabled and wounded cephalopods he found on the surface) but by following pods of mosasaurs. And in a manner foreshadowing fellow long distance ocean travelers such oceanic white tips following pilot whales and albatross following killer whales the old Pteranodon hooked up with a pod of Tylosaurus kansasensis which the big pterosaur would follow for weeks at time for food.

Albatross Encounter. NZ. Sperm whale leftovers. 

Sakamoto, Takahashi, Trathan. wiki. Albatross & killer Whales

Sometimes scraps and chunks of ammonite would float up to the surface or sometimes the mosasaurs would drive to the surface a big boil of ammonites- but what the Pteranodon really relished was when a mosasaur would surface after a deep dive with a big ammonite. The ammonite, either dead or nearly dead, would float to the surface because of the gas filled chambers in it's shell. 

At this point, with the mosasaur replenishing it's oxygen after the long dive, the Pteranodon had unmitigated access to the carcass. Perhaps grab a tentacle and flap vigorously to dismember it, or if the mantle is open start probing into it with the long, sharp beak for choice bits of reproductive organelles, eggs, and other viscera.

Duane Nash

Above I have depicted such an event. A wounded, slowly dying large ammonite has been pulled up from the depths by a mosasaur. The mosasaur, recuperating from the dive and struggle, is in the background to the right. Seizing the opportunity a Pteranodon has swooped in to pull off a tentacle.

Cheers!!

*thanks to Lloyd Lustina for letting me borrow his phone to capture photos of the ammonites/belemnites at WFVZ collection

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