Try to justify fully terrestrial amphibian creatures evolutivly speaking withouth make just "neo-reptiles" or "neo-amniotes have been hard for me, after all the common ancestor of all amniotes was more similar to a transitional stage between amphibians and reptiles. So is problematic to imagine original adaptatations to create a set of creatures which can be notoriously amphibians but which are not dependant of water.
This is mainly aesthetic, but is insteresting to have things like giant predator frogs or flying salamanders, reducing the most possible the "evolutive steps".
So I searched informations about the dissorophids a temnospondyl group (ancient permian amphibians) which evolved special adaptations to compete on land with the amniotes of the Lately Carboniferous and Early Permian when temperatures started to increase. The terrestrial features are know by skeleton which shows limbs proportions more useful for land predators than semiacutic or acuatic creatures, limbs more larger and thicker with stronger articulations, stronger column and with an extra force by osteoderms.
(Image from wikipedia files)
The previous image shows a Nooxobeia which improved these features even getting longer limbs to run, a littler head, practically I can imagine this animal running in powerful blasts like a monitor lizard.
So this liet us know that is completly possible that fully terrestrial amphibians exist, the problem is that are known by fossils which don't permit to see other adaptations like the required skin to avoid drying, circulatory and respiratory system and the reproductive methods.
And this is the part in which I want to ask for solutions, ideas about what kind of adaptations could amphibians get for become active terrestrial creatures without just repeat reptiles or general amniotes.
Considerinf things like:
- Current amphibians skin is soft and wet, it easily dries and some amphibians even use it for respiration.
- Soft and jelly eggs, easily dry.
- Tadpoles and youngs.
- The difficulty to get even more specialized legs to terrestrial life style.
This is focused on modern amphibians but I used an extinct group as reference of the possibilities
I have my own creature design ideas based on this premise but I´m let some links to images which I think are good visual examples of what I imagine.
https://www.deviantart.com/juniorwoodchuck/art/Tyrannorhinella-rex-521427961 https://www.deviantart.com/qalasaci/art/Pterorana-sp-861530408 https://www.deviantart.com/dekerrex/art/The-Knobblybelch-755534347 https://www.deviantart.com/trendorman/art/COTW-132-Yara-ma-yahoo-688836540