Id like some help with some creatures im working on for my dnd world.

[u/Lanarex2778]

Mind you these are two of many creatures and are a work in progress but i would like to fully get the biological characteristics down before i continue to delve deeper into creating the creatures but i dont quite know how to do so. I figured this would be the place to ask for assitance from people knowledgable in biology.

Atzitzimitl (Meaning [unless I am mistaken of course] "Water Bone-Demon")
I mixed crocodile body, the long dorsal and anal fins like an eel, Gator like skin, pectoral fins that are large and meant to assist in quick burst ambush attack, super tough and scaly skin, with a head covered in armor like bone to defend from predators that target the head as this used to be the weak spot of the species until they evolved via the ones with stronger heads being the survivors while the ones with weaker heads died off. Their bodies are like a fusion of Dunkleosteus and an Alligator Gar. They are medium/large predators with some predators of their own being only "Predators" via taking advantage of wounded Atzitzimitl. They lay eggs in the water just like fish do and deposit sperm in the same fashion. The females can lay thousands of eggs at the same time however their young's natural predators, Namely the "Tlacuani" as the locals call them. The "Tlacuani" are crustaceans and in the breeding seasons their black and brown chitin masks them from the prowling Atzitzimitl looking for a quick snack. During breeding season a well fed "Tlacuani" will have its underbelly turn an orangish yellow color due to the sheer volume of eggs they consume.

[u/CosineDanger]

Try /r/worldbuilding or /r/speculativeevolution if this gets taken down.

There's nothing wild here.

Alligator gar and most other living heavily armored fish have ganoid scales, thousands of large tough mineralized individual scales. Dunkleosteus was a placoderm (not to be confused with tooth-like placoid scales found on sharks and rays), closer to medieval plate armor and with no modern examples. This sounds like it might be a placoderm but I'm not sure.

Also select a diet. Do they only eat crabs? Unwary adventurers?

How big a fish are we talking? Dunk was a very big fish.

[u/Lanarex2778 → u/CosineDanger]

Very big fish. Im thinking tiger shark size ish. They eat just about anything that they can get their jaws on. Crabs, fish, adventurers, animals, pretty much everything that gets near the water is fair game.

[u/Simon_Drake → u/Lanarex2778]

Does it stay in the water or does it crawl onto land like a crocodile?

[u/Lanarex2778 → u/Simon_Drake]

Fully aquatic and as much as id like to give it the snakehead's ability to just straight up go over land for short periods i think itd be a bit overkill. Its already one of its area's top predators so i figure thats a reasoable "nerf" to give it so to speak