Leptostega is one of the first aqautic hybrids to be released with, it is a hybrid of Prostostega and Leptocledius.
It inherited the shell from Leptostega for defensive capabilites and the body shape of Leptocledius. It also shares simillar coloring of Leptocledius in lvl 40.
Leptostega is one of the first aqautic hybrids to be released, a decent coral reef creature to use in stats, it would be your stepping stones to late game and unlocking much more powerful creatures.
Unlocking hybrids would be pretty long... as you would feed and evlove your creatures.
Tip: If you are struggling on maintaining your power for the coral class... you should try to unlock, and fuse it.