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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

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  • $\begingroup$ Is this question about modern amphibians or ancient amphibians? You mention ancient amphibians as examples, but you seem mostly focused on modern amphibians $\endgroup$
    – Ichthys King
    Aug 19, 2021 at 8:35
  • $\begingroup$ @IchthysKing . Modern ones $\endgroup$
    – Drakio-X
    Aug 19, 2021 at 13:04
  • $\begingroup$ "Soft and jelly eggs, easily dry" - so you want animals with hard shell eggs which are NOT amniotes? $\endgroup$
    – Alexander
    Aug 19, 2021 at 16:58
  • $\begingroup$ @Alexander . Not exactly, interesting reproductive methods which are not the same as amniotes which would be able to solve the problem of drying. $\endgroup$
    – Drakio-X
    Aug 19, 2021 at 16:59
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    $\begingroup$ So you have two options - soft shell eggs which somehow do just fine without water (maybe drying up forms the shell), or hard shell eggs somehow allowing fertilization after the shell is formed. $\endgroup$
    – Alexander
    Aug 19, 2021 at 17:06

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Moist Skin

Amphibians generally have moist skin that is subject to dessication. But not all of them. Toads, for example, have dry skin. While I can't confirm that it protects well against dessication, I don't see why it couldn't, at least with the right adaptations

Jelly Eggs

Having moist, gelatinous eggs makes it hard to go freely on land, but doesn't make it impossible. One solution, if you really want to flaunt the jelly, would be nests, which could be soaked in body fluids such as saliva, or some sort of milk. Another solution could be for the eggs to be brooded in the mouth

Tadpoles

Tadpoles are not much of an obstacle to going terrestrial; you can simply make them terrestrial just like the adults. This will require more reworking for the anatomy, but the idea of all life stages being terrestrial is far from an evolutionary dead-end

Teeth

This depends on which amphibian you're adapting. A salamander would be fine with its lizardly dentition, but frogs are more limited, and toads even moreso. No matter which amphibian is being adapted, there's no reason I know why absent teeth couldn't be replace with ceratodontes in the ancestors of these land-frogs

Ribs

This is more a problem for large creatures rather than simply terrestrial ones, but this is still something to think about. Most amphibians do not have functional ribs. While I don't see a reason why the remnants couldn't return to their original shape, there is another solution: Gastralia. These are rib-like structures along the belly that support the organs. These could arise on amphibians, perhaps with some side-gastralia as well, allowing the amphibian to reach truly huge sizes (assuming the organs can become more efficient alongside them)

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    $\begingroup$ I was skimming and misread part of the jelly eggs section as "soaked in blood" which gave me the idea of a creature dragging dead prey to the nest and squeezing blood out over the eggs. Milk, or a comparable fluid, makes a lot of sense because it'd diffuse nutrients into the eggs as well as moisture. $\endgroup$
    – Steven Gann
    Aug 19, 2021 at 18:28
  • $\begingroup$ @Steven Gann . A cool idea, amphibians using corpse to incubating their wet eggs. $\endgroup$
    – Drakio-X
    Aug 19, 2021 at 18:59
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    $\begingroup$ @Drakio-X Similar to mouth brooding, picture a creature that disembowels prey, moves the eggs into the cavity, and keeps them there for moisture and protection. "And I thought they smelled bad... on the outside." $\endgroup$
    – Steven Gann
    Aug 19, 2021 at 19:01

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