[News]: Ichthyosaurs were bird-eaters

[tonmo]

Ceph geek news alert:

A recently discovered fossil dating back 110 million years suggests ichthyosaurs were not dining on belemnites alone. This revelation "has the scientific world in a tail-spin." Coverage can be found on news.com.au:

Bone debunks monster theory

 

[WhiteKiboko]

not directly linked to that news but, due to my subscription to scientific american (yes i know, the dumbed down version of nature or science) in late 2000 (i think somewhere between oct and dec) they had an article that stated that an Ichthyosaurus had that largest eye ever...beating out architeuthis by about a half an inch in diameter (for now).....but given as little as we know about both, i have a few dollars saying that fiugre willl grow and probably change hands in the coming years...

 

[Phil]

It is very interesting that a bird was found in the stomach of one of these creatures, what an incredible discovery! However, the ichthyosaurs were a diverse group and had many different forms from deep water slow movers to fast moving shallow water species and it should be no surprise that they show a variation in diet. In fact cannibalism has been a known feature amongst some species of ichthyosaur for many years; a small number of specimens show juvenile specimens in their stomach contents.

The species with the eyes even larger than Architeuthis was known as Ophthalomosaurus; anyone who has seen the BBC series 'Walking with Dinosaurs' will recognise it!

 

[Architeuthoceras]

Would'nt that be fun, going fly fishing with an immitation sparrow on the end of your line, fishing for Icthyosaurs. Would that be "catch and release" or "hook-em & cook-em"

Looky there, I think I got a bite

 

[WhiteKiboko]

the eating of birds doesnt surprise me too much (depending on the kind of bird) im almost positive ive seen numerous pictures of sharks going after gulls sitting on the surface...

 

[Architeuthoceras]

A bird gets blown out to sea (or dont quite make the next island), it would sit on the surface for awhile. If it was not eaten soon, eventually it would become waterlogged and start sinking. If it made it down past the ammonites, belemnites, fish and Icthyosaurs, it would enter the domain of the ancestral architeuthids (maybe they will find a bird wing in the stomach contents of Architeuthis). If it made it to the sea floor, if not devoured by bottom feeders, it would eventually become fossilized. Most fossil birds (non dinosaurian) and flying reptiles are found in marine or lacustrine (lake) deposits, so, many make it that far. But I would think alot more wouldnt.

Just Rambling

 

[Steve O'Shea]

Just discovered this link

FYI, I don't believe that Architeuthis has the largest eye either; Mesonychoteuthis, of comparable mantle length to Architeuthis (at a ML of 2.2m), must, if its kin Teuthowenia is anything to go by, have an eye even larger than Archi. We'll be able to tell you soon, coz we're up to something down here ......

O

 

[Fujisawas Sake]

Okay... Good article, but I thought that the scientific community already knew that Icthyosaurs were not feeding exclusively on Belemites? The bird in the stomach is a nice touch though! Hee hee

Here's what really bakes my noodle though: The icthyosaur "fish" body plan still lives on today in dolphins and whales. The plesiosaur design with the four powerful fins, shape, and maneuverability has more or less vanished from the scene (or been seriously reduced in size in the cases of seals, sea-lions, and turtles).

Maybe I'm stating the obvious here, but the dominance of certain designs seems to occur with multiple selective factors. Theoretically, some giant plesiosaur-like mammal should have evolved along the same lines... unless the pressures selected against it.

The selective pressures for the elimination of icthyosaurs were probably due to several factors, as is usually the case. Plesiosaurs were done in in a simiar fashion. They also ate the occasional Hesperornis and the like...

Sad, really... Heck, I wish I could see what fossil molluscs really looked like.

 

[tonmo]

Good article, but I thought that the scientific community already knew that Icthyosaurs were not feeding exclusively on Belemites?

Good point, that's my fault... I wrote the headline for the thread... but the article is simply saying that the belemnites were their main food source. I'll try to fix the subject title after posting this note.

Further to this, our friend Richard Ellis sent me this interesting email:

Hi Tony,

Thanks for the heads-up on the bird fossil. In my research on ichthyosaurs, I found no statement to the effect that they became extinct because the belemnites disappeared. In fact, belemnites survived the ichthyosaurs by millions of years, so the disappearance of the belemnites had nothing to do with the demise of the last of the ichthyosaurs.

Here's a drawing from "Sea Dragons" of an ichthyosaur (Shastasaurus)
chasing squid -- or maybe belemnites.

Richard

I'll be adding the attached file to our Art Gallery as well.

 

[Fujisawas Sake]

Tony,

No problem... Its just that the article doesn't seem quite on the ball.

It's just that in a lot of my books about dinosaurs and other ancient reptiles they state that icthyosaurs were essentially eating a relatively huge diet. I think they were a lot more 'molluscivorous' (?) than people think, and they were probably munching on deep-water fish, squid, and octopuses as well. Opthalmasaurus(Thanks Phil!), had huge eyes, and a lot of fossils show stress from deep-water travel during their lifetime.

Don't get me wrong; any opportunistic hunter would relish a little bird in his diet (and a few baby sea turtles, sadly enough). Personally, I find the fossil find extremely interesting, and the baby turtles may have been species that aren't found today... I would like to know more, but the news seems to only offer science in juicy tidbits rather than the whole meal.

Dessert anyone?

Suhsi and Sake,

John

 

[Sordes]

The biggest known eyes belonged in fact to ichthyosaurs. Ophtalmosaurus is often mentioned in this case, but it had only the biggest known eyes compared to its body-length among all ichthyosaurs. The larger species had large eyes too, and some of the ichthyosaurs became really huge. One skeleton which was discovered in Canada some years ago belonged to an animal which was about 23m in length, and isolated vertebras must have belonged to specimens with a minimum length of 27m. The eyeballs of this animals were surely even larger than those of Mesonychoteuthis (which woulb be only a snack for them).
It seems that many, especially the larger ichthyosaurs were very specialized squid hunters, which even lost their teeth when they became older. They had similar hyoidal structures to beaked whales, which probably allowed them to "inhalate" squid and fish like a vacuum cleaner. Fish is in fact only very rarely found in ichthyosaurs stomachs, most of them show only cephalopod remains. Only from one big and orca-like form named Temnodontosaurus also predation on smaller marine reptiles is known, but even they preyed in general on smaller prey.

 

[Phil]

Crikey, talk about a Lazarus thread, it's over three years old!

Thank you, that's a very interesting post there Sordes. I had no idea that fish remains were uncommon in ichthyosaur stomachs. Playing devil's advocate here though, I wonder if teuthid and belemnite hooklets are more often preserved simply due to their barbs latching into the stomach and gut linings. I reckon that hooks might be more resilient to being passed as they were more likely to be internally impaled. Perhaps this might lead to an inflated impression as to how much a part of the diet they comprised, compared to an easily digested slippery fish?

I really have not got a clue though, just a thought.

 

[spartacus]

made good sense to me Phil, gotta keep them blinkers off !
I recently read an article on Spinosaurus from North Africa, which appears to have been pigeon holed as a fish eater due to it's long narrow snout. Being an ex-wild fowler & experienced in the fine art of locomotion on soft soggy aquatic terrain, I'd love to see a demo of a 56 foot therapod dinosaur doing the same - I don't think so !

Keef

 

[Sordes]

I think many ichthyosaurs were more like modern beaked whales, which are mainly squid-eaters, although they also sometimes eat fish.
The argument with the fossilization is really good, I didn`t think about it. But there are several very good fossils from Holzmaden in Germany which shows not only all bones and the content of the stomach, but also the silhouette of the animals. If such a great fossilization happens, it would be strange if fish bones wouldn´t survive. Toady I was on the paleontological museum of Tübingen, and made some photos of the cephalopods there. I also looked at the ichthyosaur fossils, which had also all only relics of cephalopods in their stomaches.
Something about the Spinosaurus: In the stomach region of Baryonyx which was very similar to Spinosaurus, fossils of large fish were found, and the skull of this and other similar theropods like Suchomimus or Irritator were really so long and narrow, and also comparably small in relation to their bodies, that it is very hard to imagine that they hunted other dinosaurs. Furthermore their long claws on the fingers woulb be perfect to catch big fish, similar as grizzlies do it.
We still don´t know enough about the ancient ecosystems and the animals which belonged to it, to make really clear statements.