Largest spider that ever lived..

[ancientscout]

I thought this might be of interest here.
Megarachne was thought to be the largest spider to ever live. But actually, even larger was an Eurypterid[crab]. An interesting site for this is located at:
http://www.sciencedaily.com/releases/2005/02/050222192426.htm

 

[MindUtopia]

Hmmm, thought you posted your "last post" already. Interesting.

Well, welcome back, I guess. Thanks for the link.

 

[phormingochilus]

Actually what the article says is that the large arthropod Megarachne previously assumed to be a very large spider was actually an Eurypterid, which is in effect a kind of sea scorpion and which closest relative today would be crabs or lobsters. The article also states that the conclusion of this is that the largest spider of all times known to science is Theraphosa leblondi (sic! mispelling) = T. blondi ;-)

Regards
Søren

I thought this might be of interest here.
Megarachne was thought to be the largest spider to ever live. But actually, even larger was an Eurypterid[crab]. An interesting site for this is located at:
http://www.sciencedaily.com/releases/2005/02/050222192426.htm

 

[M.F.Bagaturov]

Yep, Mr. Rafn...
So the theraphosids still do not have an ancestor

And here is what we had some no long time ago:
http://tarantulas.tropica.ru/english/index2.php?link=evol1.html

 

[phormingochilus]

I think the Theraphosidae do have an ancestor - everything else would be ridiculous ;-) But I do not believe we will find some giant "megadinomygalomorph" ancestor. I believe the large sized theraphosids of today is something new and that their ancestor is a smaller spider, much like the general bulk of mygalomorphs today. If we look at a cladogram for Mygalomorphae placed within a time frame in the article of DAVID PENNEY ET AL. in Evolution, 57(11), 2003, pp. 2599–2607, we see that the origin of the Theraphosidae clade happened in a splitting event some 20 million years ago resulting in the Paratropidae and the Theraphosidae, about 21-22 million years later but still in the Neogene age the Theraphosidae/Paratropidae clade seperated from the Barychelidae clade. The Barychelidae/Paratropidae/Theraphosidae clade were seperated from the Nemesidae/Dipluridae clade in the early Cretaceous periode some 120 millions of years ago. Thus it is pretty well supported that these three families; Paratropidae, Barychelidae and the Theraphosidae are relatively closely related both morphologically and on the evolutionary time line. If we look at the sizes of the members of these three families it is only in Theraphosidae we finde the truly huge spiders. The members of the Paratropidae and Barychelidae is small to medium sized spiders. The bulk of species in the Theraphosidae isn't exactly monstrously sized either but small to medium sized with the few enormous sized exceptions mainly found in the Theraphosinae clade. If we compare the Theraphosidae to the bulk of species in the entire Mygalomorphae clade this supports the notion that big sizes are a unique Theraphosidae phenomenon as well. Thus I believe the big sized spiders found in Theraphosidae is to be something new and unique for the Theraphosidae family.

Regards
Søren

Yep, Mr. Rafn...
So the theraphosids still do not have an ancestor

And here is what we had some no long time ago:
http://tarantulas.tropica.ru/english/index2.php?link=evol1.html

 

[Crotalus]

The idea about a small ancester have as little evidence as a giant ancester. Until someone find fossils.
I dont see a problem with a giant ancester, since that is quite common among other life forms such as reptiles.

 

[phormingochilus]

I do not agree with you here Lelle. Contrary to the hypothesis of a big ancestor the hypothesis of a smaller ancestor is backed up by fossil evidence, and is congruent with the picture we see in the systematics like phylloogenetic cladograms which must be assumed to be much more solid than no fossil evidence and thus no data to fill in to the cladogram ;-) ...

Remember that spiders are not reptiles and you cannot directly transfer evolutionary trends for the Sauropsida and the Arachnida clade. There has evidently been giants in the Arachnida clade, but not in the Aranea clade. The ancestor of reptiles were also relatively small compared to the later dinosaurs, and members of this (these) clades did at times reach huge sizes as is evidenced by the fossil record. This cannot be said about the spiders.

Regards
Søren

The idea about a small ancester have as little evidence as a giant ancester. Until someone find fossils.
I dont see a problem with a giant ancester, since that is quite common among other life forms such as reptiles.

 

[Crotalus]

No they are not reptiles but lots of other nonreptilians had giant ancestors. All im saying is since we dont have proof of small or gigantic ancestor in theraphosids its just theories. Clads can only show so much. It wont tell you everything.

 

[phormingochilus]

Yes other non-reptilians had giant ancestors, but then again other non-reptilian ancestors had not - whales is just one great example of this. Again vertebrates and invertebrates are not the same clades and they had different eras of peaking with different environmental parameters influencing their evolution together with the absolute differences in morphology and anatomy this makes it pretty hard to draw any parallels between these clades.

What is important is to look at what we know and not what we can imagine. I can imagine a lap dancer here in front of me right now, unfortunately my ability to imagine this doesn't make it true. Evidence defines what we can define as truth. And there is no evidence of neither a lap dancer in front of me nor of giant ancestors in the Aranea clade thus we cannot claim the lap dancer or giant ancestors in Aranea as truth as it is not backed up by evidence.

Thus the speculation of gigantic ancient spiders is for now (I do not discard the possibility alltogether but there is no fact to support the idea) lumped together with other myths and legends of zoocryptology as the yeti, medieval dragons and the loch ness monster. Imaginably yes - but supported on fact and evidence? No.

Clades are used to test hypothesis and theory, and yes the selection of characters are subjective but the essence is that cladograms are working tools for discussion for the scientific community as you have to justify and show every step of your thought process thus the cladograms are not definite pictures of THE reality but definite pictures of the perceived reality AND the process leading to this understanding in individual groups of scientist and the scientific community as such. The discussion and trimming of cladograms is in effect a total picture of the progress of true evolutionary science, not everything, but pretty damn close to depicturing everything we know so far.

Regards
Søren

No they are not reptiles but lots of other nonreptilians had giant ancestors. All im saying is since we dont have proof of small or gigantic ancestor in theraphosids its just theories. Clads can only show so much. It wont tell you everything.