This is apparently what basal insects looked like. Bunch of myriopod looking things.
This is apparently what the common ancestors of molluscs looked like. Snail stuff.
Two theories of bilaterians. Post interesting basal animals.
>>4795960Yes? And?
I think I can believe it
>>4796038I just want people to post basal versions of modern animals.
>>4795962Which is more Lively?
>>4796935Assuming Xenacoelomorpha is at the base of Bilateria, then the "Planuloid" hypothesis is probably more correct. But when people think of Bilateria they are often thinking about just Nephrozoans. The last common ancestor of Nephrozoa may have been more complex.
>>4798204errm, english please?
>>4798204A small quibble with this, it turns out xenocoelmorpha have all the genes except one for forming an anus, so it seems their blind gut is a derived rather than ancestral trait. So it seems the urbilaterian at least had a through gut.
>>4795960I mean, remipedians are the closest living relatives of insects so it checks out. The first terrestrial ancestors of insects were probably myriapod-like crustaceans that later became extinct. I wonder how many groups of arthropods evolved terrestriality only to become extinct and leave no trace of their existence.
>>4795960Checks out. Lobopodians are the ancestors to every arthropod alive today. The closest modern relative to lobopodians or the animal which has retained the most basal features are velvet worms.
>>4799058I don't know if I can put it in simple terms, but this cladogram helps explain what I mean. Xenocoelomorpha is the first group to split off from the rest of Bilateria. Given that the closest groups to Bilateria, such as Cnidaria (jellyfish, sea anemones, corals) also lack the traits in the "Complex" Urbilateria hypothesis their absence in Xenocoelomorpha is likely an indicator of what the first bilaterian was like. However, it is possible that some traits may have been lost in Xenocoelomorpha (>>4799093 refers to evidence that the ancestors of Xenocoelomorpha had a through gut) and that the first bilaterian may have been more complex.This all assumes that this cladogram is correct though. There is a competing hypothesis that Xenocoelomorpha is a branch within Deuterostomia in which case the lack of complex traits in Xenocoelomorpha cannot be taken as evidence for the "Planuloid" Urbilateria hypothesis.
>>4799255Damn, I half-joked and you actually went out of your way to explain it, thank you it was an interesting read!
>>4796137Thank you, I've never seen this ancestor of mine.
