HOME | DD
Eurwentala β Island Dwarf
Published: 2010-12-03 22:34:28 +0000 UTC; Views: 4638; Favourites: 107; Downloads: 44
Redirect to original
Description
Europasaurus holgeri lived in what is now Germany in the Jurassic. At the time, Europe was an archipelago, and the fossil animals show fascinating adaptations to island life.These islands were too small to support a population of giant sauropods. Thus, the sauropods shrank until they were only around the size of a cow.
The fact that my Europasaurus is wading is not meant to imply that they were aquatic. I just imagine the animal taking a quick bath and a drink on a hot day. On the background, there is a random four-winged paravian. I know the basal paravians probably (?) couldn't lift their hands above their backs, but couldn't resist the pose.
Related content
Comments: 30
Interesting
But I heard that not only large herbivores shrunk, but even larger carnivores, smaller herbivores, and smaller carnivores where pygmy sized
π: 0 β©: 1
In modern world, it generally seems small animals grow to giant sizes on islands (giant rabbits, giant dormice, giant geckoes and skinks etc.), while big animals shrink (pygmy elephants and mammoths, goats etc.). I'd suppose something similar was going on in the time of dinosaurs as well. As most non-avian dinosaurs we know were fairly large to begin with, it's sensible that most of them shrank. Then again, Balaur bondoc might have been a giant flightless island bird.
π: 0 β©: 1
Hmmm
So smaller raptor like carnivores would be the apex predators
I like these ideas, but I don't understand why animals would switch rolls in dominance and size???
π: 0 β©: 1
The details of evolution on islands are, I think, still hotly debated, but there is a fairly good general explanation to what happens. The thing is, islands are not just copies of mainland ecosystems. They are inbalanced and less biodiverse, as few big terrestrial animals ever make it onto islands, and extinctions are more frequent on small land areas. The fauna is constantly changing, as species go extinct and new ones arrive.
The animals don't really switch roles in size, but rather get closer to each other. Large predators are usually absent, which frees the herbivores to do a lot of things that are impossible on the mainland. Paired with limited food, it makes herbivores do odd stuff. Small herbivores like rodents or tortoises have a chance to get bigger (and clumsier), which makes it easier to digest plants and carry fat reserves. Big herbivores, on the other hand, tend to get smaller, because a small island might simply not be able to carry a viable long-term population of, say, full-size elephants or sauropods. To save energy, their brains are also often significantly smaller than their mainland relatives: you don't need much wits in a world without predators.
Small carnivores, if they make it onto an island at all, might get larger, because the ecological niches of large predators are empty. There have been some giant otters on Mediterranean islands, for example. On the other hand, they might become more omnivorous or herbivorous in the absence of prey, such as many island geckoes and skinks. Flying animals tend to lose their ability to fly (think dodo), because they don't need to in the absence of significant predators, and flying off an oceanic island is most often a suicide.
I can only think of one case where a large, hypercarnivorous predator somehow ended up on a small and isolated island without big prey. That was Xenocyon - the common ancestor of today's dholes and African hunting dogs - and the island was Sardinia. It evolved into a much smaller, fox-like animal called the Sardinian dhole (Cynotherium sardous), so the shrinking rule seems to also apply to big predators. Then again, Komodo dragons stranded on Komodo and Flores still have plenty of big prey, so they have stayed large despite being on islands.
So there's a lot of exciting stuff going on on islands, with different islands ending up with very different faunas depending on which species managed to get there. European Jurassic and Cretaceous islands were fairly large and close to each other, which probably made them more similar to mainland than, say, Hawaii, but they still had plenty of oddities.
Okay, apparently I just accidentally wrote a full essay on this. I hope this satisfied your curiousity.
π: 0 β©: 1
this is very interestingΒ
id like to study more on this
thanks forΒ explainingΒ this to me
your very knowlageable
π: 0 β©: 1
Thanks! Evolution has these insanely interesting quirks. I recommend studying more, as it never stops surprising.
π: 0 β©: 1
They could have swam between islands however.
π: 0 β©: 1
Yeah, sure. Much like giant tortoises and Komodo dragons today travel from oceanic island to another. Though in tortoises, it's more like uncontrolled cruising.
π: 0 β©: 1
Considering that sauropod bodies were surprisingly lightweight thanks to air sacs and hollow bones this could've being a feature possessed by many if not all sauropod species.
π: 0 β©: 1
Yeah, though floating like a cork might make controlled swimming a bit difficult.
π: 0 β©: 1
They could've serve as mobile ecosystems for lots of tiny animals nesting on their great backs.
π: 0 β©: 0
Well, I was thinking about gliding with some flapping. Something like the almost-flightless fowl and pigeons do. I suppose there's a tree outside the frame where it jumped to glide.
π: 0 β©: 0
It was a brachiosaur, not a titanosaur. The famed dwarf titanosaur was actually Magyarosaurus, which lived much later than Europasaurus. But great drawing nonetheless
π: 0 β©: 1
As far as I have understood, Europasaurus is thought to be a sister taxon of Brachiosauridae (according to Sander et al's 2006 paper and Ksepka&Norell's 2010 phylogeny) and not a brachiosaur itself. In the Wikipedia article about macronarian sauropods Europasaurus is contained within Titanosauriformes, which is what I meant by "a titanosaur". On closer look, I'm not sure what this is based on, since the reference articles don't seem to support that (though I can't read all of them). It seems like the 2010 phylogenetic analysis leaves Europasaurus just outside Titanosauriformes. I suppose it would be most probably right just call it a dwarf sauropod, or perhaps dwarf macronarian. 
π: 0 β©: 1
Well it's a basal Brachiosaur for all practical purposes.... it's much closer to brachiosaurs than to titanosaurs. I don't know if the meaning "sister taxon of brachiosauridae" really means it's not a brachiosaur, rather it could be a basal "stem-brachiosaur" but really at that point it's like splitting hairs. It's more derived than a camarasaur and is thus grouped in to titanosauriformes. Now the most basal family of titanosauriformes (and the one closest to Europasaurus) is indeed Brachiosauridae. So unless there's another family into which it can be placed, I'd say it's a brachiosaur, even if a very primitive one. The nasal structure is far more like brachiosaurs than anything else, as with the vertebrae. Since brachiosauridae as a clade hasn't been defined all that consistently, it's quite possible it was more inclusive than it's currently understood to be. Things like Paluxysaurus, which have been classed and even reconstructed as titanosaurs, are now more favorably identified as brachiosaurs. It's a cladistics issue more than an evolutionary one. The morphology of Europasaurus is extremely close to all known brachiosaurs so in all likelihood it is also a brachiosaur, and also descended from a common brachiosaur ancestor like Volkheimeria or Atlasaurus. That's just my take on it. The skulls of Atlasaurus and Europasaurus look so similar it's not even funny. They're more like each other than like other brachiosaurs.
π: 0 β©: 1
Ok, thanks for clarifying.
Though I do not find Europasaurus being the sister taxon of Brachiosauridae all that weird. You have to define a clade somehow, and pick an ancestor, whose descendants will be called brachiosaurs. It's inevitable that the closest (in time and relations) sister taxons will be very similar to basalmost members of the clade. If, of course, Europasaurus is descended from a taxon that is a brachiosaur (is it? I don't know) then it must be a brachiosaur.
π: 0 β©: 1
That's the 64,000 dollar question - was Europasaurus descended from a brachiosaur? It was a Late Jurassic animal (Kimmeridgian epoch). This seems to fit with the theory that it was indeed a brachiosaur, since the oldest brachiosaurs were from the Middle Jurassic (such as Volkheimeria, Atlasaurus, Daanosaurus, Lapparantosaurus, and possibly Klamelisaurus). Europasaurus has more brachiosaurid features than any of those early forms, and emerged later. So there's a strong possibility it was a brachiosaur. Living in Europe at the same time as Lusotitan does point to some pretty predictable family ties.
π: 0 β©: 1
It does sound plausible, I agree. Then again, the cladistic analyses have found Europasaurus outside Brachiosauridae. I don't have enough expertise to have a really informed opinion.
π: 0 β©: 1
Well.... to be honest I hate cladistics. Not because it's unreliable, but because to MAKE it reliable you have to account for a lot of "characters" that sometimes get missed, and yet so many people (professionals included) tend to treat cladistics like some kind of infallible holy oracle that can never be wrong. Gimme a break! Cladistics is only as good as the software you use and more importantly, the data you put into it! Also your reference taxa need to be MANY in number. For example to do a really strong cladistic analysis of Europsaurus, you need to put in at least five brachiosaur taxa and easily twice as many non-brachiosaurs. Most of these analyses are WEAK because they include only two relevant taxa (for brachiosauridae usually only Brachiosaurus and Giraffatitan) and they tend to define a clade very weakly (brachiosauridae in some analyses is defined only with ONE feature - a femur transversely broad at mid-shaft).
This is a sad way to go. First of all, there are way more diagnostic features than just that one for brachiosauridae. Second, the family must be well-represented. Lusotitan, Bothriospondylus, Pelorosaurus, Cedarosaurus, Abydosaurus, and Paluxysaurus almost NEVER get used as reference taxa. WHY? Because everybody has to do their own cladistic analysis, with their own data. Well that's just dandy, because one person can only gather data on so many specimens. If all the brachiosauridae were put into a juxtaposed analysis (matching a part of Europasaurus against ALL brachiosaurs for which that part has been found) then for each bone there would be a factor of "brachiosaur-ness" or diagnostic match-up with brachiosaurs as opposed to non-brachiosaurs (or N/A for bones not found for any other brachiosaur). These relevant bones could then be rated on the strength of these factors. Average them out and you get the final result.
So the recap, cladistics is ONLY a tool! It can be good or bad for science depending on how effectively you use it. Too many scientists focus on complicated algorithms and concepts like stem-node hypertrophy and "jackknifing" in their cladistics, when they really should be sticking to the basics - large sample sizes, diverse arrays of reference taxa, and stack-juxtaposing body part characters without set limits (overlapping comparisons - since many species only include a few well-preserved bones rather than the whole skeleton). If they can prove it's more basal than Volkheimeria, then for now it's not a true brachiosaur. If that's not possible, then we all know the logical conclusion.
π: 0 β©: 1
I'm sure you're right about that. Really big phylogenetic analyses demand enormous amounts of work and quite a bit computer time for the calculations - and those, of course, are the more reliable ones.
I have only made these analyses with genetic data, but I can see what you mean.
π: 0 β©: 1
Yeah, it's a bit funny how those things turn out. For example, it's widely accepted now that Lognkosauria is a genuine clade of titanosaurs, because Calvo et. al., 2008 put together a solid phylogenetic tree with very strong bootstrap characteristics (even though they got the measurements totally wrong on Futalognkosaurus ironically). But the problem for people like me is that all their diagnostic characters for Lognkosauria were features of the neck - which makes a comparison VERY hard for possible lognkosaurs that are not known from neck material. Plus, there are plenty of other unique lognkosaur features that are not on the neck. So the analyses, even the really good ones, are only as robust and useable as the data you put in them.
π: 0 β©: 0
Nice job. You seem to know a lot about dinosaurs.
π: 0 β©: 1
Thanks!
I try to, at least.
π: 0 β©: 0
The Pavarian looks quite naturally posed, so I would say you did good. And the Europasaurus looks big until I read the description. Very, very good.
π: 0 β©: 1
Thanks!
The pose looks natural to me too - that's why I drew it. It just might be anatomically impossible.
π: 0 β©: 1
True, birds must have a Hell of a time getting that wing above their First vertebrae. That is how Vertebrae is spelled, right?
π: 0 β©: 0
