Proteid evolution

[Markgilst]

I know that the mudpuppy in north america and the olm in europe are of the same family, but why are two super similar species distributed so far from eachother? did their common ancestor live in both areas at a time where europe and america were connected? was there a time when no glaciers made the ocean waters less salty enough for the common ancestor to swim across and live in both parts? was there a time during the ice age where more land was exposed (and possibly rivers) so that necturi could swim through the arctic to europe? some of this sounds pretty silly i'll admit but this really makes me wonder, how did the two species so similar get spread so far apart from eachother?

 

[Jennewt]

Your first speculation is correct: Pangaea. There are many other examples in other families of animals too.

 

[Vern5384]

Their origin is probably a little more recent than Pangaea. Maybe more like Laurasia. The family probably did evolve, in fact, at a time when North America and Europe were connected, such as during the Jurassic, although fossil proteids are only known from much more recent deposits (the upper Paleocene in Canada.) Super cool family of critters. I'm doing a Master's thesis on dwarf waterdogs (Necturus punctatus.)

 

[Markgilst]

you sure? because the proteid fossil record is apparently only from about 50 million years ago, just a bit after the cretaceous ended. but it seems legit.

 

[Vern5384]

50 mya is, indeed, shortly after the Cretaceous during the late Paleocene/early Eocene as I said, and the oldest known proteid fossils are from this time period. However, the fossil record is not necessarily definitive of the origin time for a taxa. Something small and squishy like a salamander isn't all that likely to fossilize, anyway, so the ancestors of many of these taxa probably were around long before one of them happened to perish and be deposited in the right conditions to fossilize and be found later by us. Biogeography and phylogeny seem to place the origin of this family much earlier than the fossils would indicate.

 

[Markgilst]

Like in the Permian, Triassic, or even Devonian? Yeah, I've noticed that a lot of the fossils from those early amphibians look really similar to aquatic salamander skeletons.

 

[sergé]

There is another fascinating puzzle: the plethodontidae! Which are widespread in the America's, the most common group, but only a few species in Europe (France, Italy with the island of Sardenia with at least 5 endemic species of Speleomantes...) and then one specie in Asia (Karsenia!).

 

[methodik]

The species of europe (Speleomantes) were put into one genus with some of the US-American west coast (Hydromantes) before, if I remember right.

 

[Vern5384]

Just to guess, I'd say Jurassic or early Cretaceous. The common ancestor of frogs and salamanders probably split during the Triassic (frog fossils are known from this period, but sallies don't show up till the Jurassic.)

 

[Chamaeleo]

The last common ancestor of frogs and salamanders lived rather in the Permian. (Triadobatrachus massinoti, one of the earliest frogs, is from the early Triassic)

 

[Vern5384]

Guess I may have been off by ~2 million years out of 250 million or so. Are there any hypothetical fossil intermediates between caudates and anurans (something like a common ancestor)? I honestly don't know. Would like to see what that would look like. I'm guesing an awful lot like a salamander.

 

[FrogEyes]

It's highly doubtful a definitive direct ancestor to both urodelans and anurans will ever be identified, but Lissamphibia are usually suspected to being derived from within Amphibamidae [Temnospondyli]. Alternate hypotheses suggest Lyssorophia [Lepospondyli], especially for either caecilians or caecilians and salamanders; or Microsauria. Within Amphibamidae, the main suspects are Amphibamus and Doleserpeton.

Would like to see what that would look like. I'm guesing an awful lot like a salamander.

That's a truism. Frogs had a highly modified [derived] body plan, whereas salamanders have a very universal plan, that of a tetrapod with four legs and a tail [ie, a plan shared with modern reptiles, turtles, fossil "amphibians", crocodilians, dinosaurs, some fossil snakes, one fossil caecilian, limbed transitional fishes, and most mammals]. Temnospondyls and most of their derivative groups, like Lepospondylia, Microsauria, Lissamphibia, and Amphibamidae, almost universally share this design.

On this question though, proteids are not relevant. They're not close to the origin of either salamanders or modern amphibians, but are a fairly recent derivation within modern salamanders. Older hypotheses suggested different origins for North American and European lineages, but the best recent data suggest the two to be closest kin. While sharing recent origin, that origin is still old enough for a land/freshwater link between the two lineages. The modern continents are really very young, relatively speaking. It's interesting that although the two lineages have similar numbers of species, the Old World [Proteinae - Proteus] is almost exclusively subterranean, while the New World [Phanerobranchinae - Necturus] is exclusively epigean. I suspect the karst habitat had little competition in Europe, while epigean habitats either retreated into the karst, were lost entirely, or suffered competition with various newt lineages [many of which are now extinct]. In North America, stream habitats of all kinds were either occupied or quickly colonized by plethodontids, the latter seemingly being the first to take over the mountain stream and subterranean habitats. Thus, Necturus remained restricted to the same habitats it now occupies, and Proteus habitats gradually retreated into the limestone.

 

[Markgilst]

Just a wild guess but maybe the fossil record is a little older than thought with various species of salamanders evolving before the continents split up?