these are SUPER cool!!!

There's a pang of sadness I feel when I read that bit about how they eventually have to return to the sea permanently. Just the idea of passing a life threshold and never being able to go back, leaving behind everything that was there no matter how it meant to you.

Certainly such a species would develop a tech to mitigate such a fate?

A personal counter gravity field would probably help, either lessen or completely neutralize local gravity beyond what is necessary for movement, similar to the Dune universe's Holtzman Suspensors. I'm not sure if the gravity generation tech in Hayven Celestia is miniaturized enough to make that work, though.

That, or giant mobile fish tanks.

Mobility fish tanks, support exoskeletons...

I love all the new species

Quite fascinating!

Kangaroo shark ocean friend

The big boy is handsome

Very interesting to have an aquatic race.
They do look somwhat like that Geroo race.

roo sharks!

Reminds me of a kangaroo with very shap teeth!

fuzzy shorks

Interesting species design! Very cute fluffy shork-roo.

Although I admit some of the species traits remind me of the Liir from the Sword of the Stars series of video games. Was that some of the inspiration?

This is a very kick ass design I can get behind. A fusion/hybrid of Roo & Shark: Adorable yet vicious. Fluffy, yet sharky

I really wanna see what some of the eldest tryonn look like

Do not overfeed your Tryonn, as tempting as it may be.

Okay, this guy is just plain adorable!

For a minute I thought it was a character sheet for the demon in housepets.

So, they’re born in the water, live in the water and usually die in the water and only use dry land as a technology, yet they have a very obvious bipedal land-dwelling body plan that would be more of a hinderance in their mostly aquatic life?

Kinda awkward on dry land, spending most time in water. Crocodile or aligator is the first thing that comes to my mind. Only able to keep partialy uplifted posture.

Crocodilians are probably the best species for this analogy. Land does have utility for them for laying eggs and traveling between bodies of water, but most other business is done in water. But I get OP in that occasionally needing to be on land doesn't make the super optimized bipedal structure that realistic, but I personally like the concept of a species having a set amount of time to spend on land enough to ignore the slight weirdness lol

its like if a kangaroo and a shark had an offspring, coupling it with a reptiles to grow continuously throughout its life time, an are so super cute too, dunno if it be practical to give one a hug though, certainly wouldnt mind one myself

I feel an affinity toward these not shark sharks.

How do the lungs and gills work together?

They each are built to shrink and close up when the other is in use

“Chlorine breathing”
How does that work? How do you get a chlorine based metabolism? Also how does that atmosphere requirement conflict with them operating in environments with other beings who, for example, breath oxygen?

Well first when I name an element for these species, I don't mean chlorine gas specifically. I'm not a chemistry expert so you can substitute that for "some kind of chlorine-based gas that is atmosphere-and-oxygen-stable" and generally in small but significant amounts. How does the metabolism work with it? I don't know. I'm not a biologist. I just know that oxygen itself is, in a way, corrosive, so it makes sense that other corrosive chemicals may be chemically useful in different evolutionary processes. It makes less sense to me to name a noble gas because they're non-reactive in most circumstances.

And in the stories, they generally can't operate in the same environments as species who breathe other atmospheres. There's ways around this--cybernetics, or masks/rebreathers, but that's one of the things about their situation is that not all species can live in all others' atmospheres.

I see, interesting...

May consider picking up the basics of bio chemistry if you want to be building custom atmospheres.

I find it interesting that you'd mention that, considering that on the atmosphere comparability chart Tryonn are labled as "Temporarily Survivable" for oxygen atmospheres, a classification which they share with Georidans with regards to oxygenated atmospheres, and Geordians appear to be able to breath oxygen as evident by them being maskless with Geroo in these two images (https://e621.net/posts/5176206 and https://e621.net/posts/2636196); as well as by their ref sheet which mentions their atmosphere mix has 1.5% ammonia and 19% oxygen, strongly suggesting they use the oxygen for respiration not the ammonia.

This leads me to think Tryonn dont use Chlorine for cellular respiration, but rather use oxygen and they need chlorine/chlorides because they're body chemistry developed with those gases present and thus would have problems without them.
I also have a suspicion that this is the same for many other species, as oxygen is present in the atmospheres of every species you provide an atmosphere breakdown of, and Sourang are able to adjust their bodies to a given atmosphere indicating they likely consume a base gas and then modify their body to process/reject the other foreign gasses.

Basically, species use oxygen for respiration, but then have some other gasses that are needed because the species developed with said gas and thus their body chemistry is tuned to need the given gas.

I would like to note this approach is somewhat useful for writting. It reduces the work on your end with regards to figuring out biochemistry as rather than figuring out how bromides or chlorides or flourides could work in place of oxygen in individuals and the biosphere as a whole, you could write that a species breathes oxygen but just needs x gas.

For example Geordians and Cosa both need high blood ammonia levels and have high blood ph as a consequence of their atmospheres containing ammonia. Without ammonia to breath, they would eventually die due to their blood ph falling too low, but the half life of the ammonia in their blood is long enough or their healthy blood ph range is wide enough they can breath without it for periods of time.

I wonder if any Tyronn's suppress or halt their growth to stay on land.

That would actually be an interesting idea, groups of Tyronns who halt their growth and thus can not only work on land but potentially travel beyond their home world, exploring space and potentially living among other species because they wont ever have to worry about growing too big.

I could imagine a social division emerging between Tyronn who endlessly grow and those with locked sizes, a division both due to clashing approaches to handle their biology and due to them physically occupying different enviroments.

My current thoughts on them have them regularly deliberately halting their growth for military/exploratory purposes. They engage in a very strict diet during this time to prevent unnecessary calories from causing undesired growth spurts

I knew about the dieting. I was thinking something like a hormone implant that suppressed the growth, likely forever. Something that would create a clear distinguishment between the eternal growers and those with halted growth, and would not require as much work to maintain as a diet.