The Vampire and The Plesiosaur

[Phil]

These images depict a very unusual cephalopod discovery; this particular cephalopod, as far as I have been able to determine, represents the only known fossils of an ancient relative of the Vampire Squid, Provampyroteuthis giganteus. The fossil depicts a partial ribcage and stomach contents (including gastroliths) of a hitherto undescribed elasmosaurid plesiosaur (1998). The fossil dates to the early Santonian of the Late Cretaceous period, (approx. 87-85 mya ) was found at Hokkaido, Japan and is currently housed at the Yokasuka City Museum.

The black wedge shapes clearly visible between the ribs represent upper and lower jaw apparatus of this ancient vampyromorph. Interestingly, the upper jaws have been reported as bearing a striking similarity to the modern Vampyroteuthis infernalis and other octopods yet the lower jaw is more nautiloid in form. Major differences with Vampyroteuthis are that of size, Provampyroteuthis being considerably larger, and that of environment. Vampyroteuthis currently lives at a depth of 300-2500m whereas the Provampyroteuthis must have lived at a much shallower depth as it thought that the plesiosaurs were surface or shallow water swimmers and it is believed that these fossils came from an off-estuary deposit.

Perhaps we are looking at a scenario whereby the close relatives of Vampyroteuthis were, at least in some areas of the world, larger, more powerful surface swimmers that were slowly driven to the depths of the deeper parts of the ocean in the late Cretaceous or early Tertiary period. Today their descendants survive as smaller and weakly muscled ‘living fossils’.

Thanks to Mike Everhart for the photos.

 

[Phil]

And a Vampire Squid today, image credit Cephbase.

 

[Architeuthoceras]

Fantastic Phil

Boy, There must have been alot of cephalopods swimming around in the oceans during the Cretaceous.

Could Elasmosaurs have been like sperm whales, diving deep for their dinner? This one just happened to die in shallow water.

 

[Phil]

Well, and this just my opinion......... it seems to me that elasmosaurs would have hunted by purely visual methods, unlike the Sperm Whale which probably uses echo-sounding to locate large squid or shoals of squid. It is interesting that the eyes on elasmosaurid plesiosaurs were located angled slightly upwards on top of the skull and the fact that many examples, including this one, contained stones as part of the gut contents. These gastroliths were believed to have worked as counterbalance to create neutral buoyancy during dives. There is also evidence that some plesiosaurs suffered from ‘avascular necrosis’ in the humeri and femora, this being a form of bone death that is brought on by the interruption of blood flow as part of decompression sickness (5% of 576 specimens in a recent study published in the Journal of Vertebrate Paleontology).

As the eyes of elasmosaurs were much smaller than some of the deep water ichthyosaurs, I can’t imagine that the animal would have dived as deeply to hunt for prey. Putting this together it seems likely that the plesiosaurs may have swum underneath their prey perhaps looking upwards for silhouettes of squid and fish against the surface of the sea before snaking up and jabbing at their intended victims.

It is a pity that this particular plesiosaur has its head missing so we cannot confirm the precise position of the eyes, and the rest of the fossil was not diagnostic enough to allow for specific species identification so one can only rely on comparisons with similar animals. The fossil indicated that the plesiosaur was about ten feet long, and consisted of the right forelimb, fragments of the pelvic girdle, the right half of the pectoral girdle and disarticulated vertebrae.

I suppose another possibility is that this particular plesiosaur hunted at night and these fossils of Provampyroteuthis were in fact deep water animals but rose to shallow depths following the plankton during the nightly vertical migration that is such an important feature of todays oceans. There is no reason to suppose that this wasn’t as important in the Cretaceous oceans. Perhaps our plesiosaur glided below them watching for silhouettes against the moonlight or looking for flashes of bioluminescence.

 

[spartacus]

Phil, having just watched Blue Planet, could I propose that this particular elasmosaurid plesiosaur preferred red prey & therefore sported a red beacon on its head making its dinner visible in the dark depths ?
Shame the head is missing to add credence to my theory.