Tetrapodomorphs/Fishopods

[Zirojtan]

I'm really sorry that I keep posting threads with frankly rather random questions about science, but here we go again:


Is anyone on here particularly savvy with early tetrapod evolution? I'm really trying to understand the transitions that were made from sarcopterygian to tetrapodomorph, but a lot of what I am finding on Google is just creationist junk about how scientists haven't been able to conclusively make the link between the two.


I'm specifically interested in the morphological changes of the limps and the neck, and the hypothesized reasons behind these transitions.


I've read quite a bit concerning the idea that limbs were evolving in tetrapods as a way for fish to maneuver through vegetation-clogged water, but some of what I read says that these animals may have been marine, and others say that they lived in freshwater, so I'm not really sure.


Also, I'm interested in early lungfish, such as Dipnorhynchus and Dipterus, if anyone has any info on those. Those are very scantly described animals on the internet.

[madd0ct0r]

fire alrylium a message.

[Zirojtan]

Alrylium? I was unable to find a user by that name. Do you mean Alyrium?

[Wing Commander MAD]

Yes, that's who he meant.

[Alyrium Denryle]

I have been summoned.

I've read quite a bit concerning the idea that limbs were evolving in tetrapods as a way for fish to maneuver through vegetation-clogged water, but some of what I read says that these animals may have been marine, and others say that they lived in freshwater, so I'm not really sure.

Either way, it works. There are aquatic plants in coastal marine and estuarine habitats that are all salt water. The other thing is that these organisms could easily have inhabited both habitats, it is not as if Ichthyostega for example was the ONLY SPECIES in its entire taxa. Afterall, there are only a few places where fossils of that period are accessible/still exist at all due to subduction.

Still, the consensus view is that they evolved in shallow vegetation choked water. This is primarily because they did not have a pelvic girdle capable of supporting them on land such that they could actually move between bodies of water, which was the old hypothesis. Given that, plus the vegetation in the sediments...yeah. Like walking catfish, they might have been able to squirm over short distances, but that is about it. The flexible neck would have allowed them to take prey at the surface in shallow water, which they otherwise would have had difficulty doing if they had to orient their whole bodies. The ability to breath air is also common among fish in low-oxygen environments like warm shallow water.

If you have any more specific questions, I can answer them readily. Before I switched over to insect behavior and functional morphology, I specialized in amphibian behavior and functional morphology...

[madd0ct0r]

huh. didn't know you'd moved on to insects.

[Alyrium Denryle]

huh. didn't know you'd moved on to insects.

I dont need to deal with collection permits unless I want to work with something endangered, and at no point do I ever need to worry about local populations being stressed by what I do. Dragonfly nymphs are available year-round. I dont have to deal with animal research ethics committees, which are an extra special pain in the ass when you study predator-prey interactions, even when everything is going well (and heaven help you if they go terribly terribly wrong).

All in all, it is a win. Plus I get to work with these.

[Zirojtan]

I do have more questions, actually.


What do you know about the morphology of fossil lungfish like Dipterus and Dipnorhynchus? I've been unable to find much about either of them besides references to their skull morphologies being more similar to early tetrapods than modern lungfish, but exactly how that is I haven't been able to find out.


And I was aware that they were believed to have evolved in vegetation choked water, but in both salt and freshwater then? I'm not much of an expert on aquatic habitats at all, but over the past couple of days I've been doing some reading about coral reefs and such, and what I read suggested that one of the essential functions of coral reefs is blocking waves that would otherwise erode other habitats, thereby providing for their assistance. Is that true? And if so, then would that imply that some early tetrapodomorphs may have evolved in vegetation choked habitats that were provided for by nearby reefs?