u/johandiaz12326

Balaenolangosta leonii (Leon's whale lobster), named after Leon the lobster, is possibly the largest crustacean in my future earth, with a maximum length of 20 meters and weighing about 40 tons, it has convergently evolved with modern day baleen whales but they have some unique adaptations that make them very interesting animals.

Starting with the way they feed, they catch plankton and schools of small fish with the thousands of long bristles present in their maxillipeds and first two pairs of legs, kinda like modern bamboo shrimp and porcelain crabs, but instead of waiting for the food to come to them, they employ ram feeding, swimming through the clouds of zooplankton at high speeds, when the bristles are full they pass them through their mouths to eat all the food they've caught, when not in use the mouthparts fold and all gets covered by the second pair of legs to reduce drag (you can see how the folded mouthparts look in the juveline at the top left of the drawing).

Speaking about that juvenile in the top left you can see that it is molting, but this molting is special and very different to any known arthropods, modern crustaceans often die of exhaustion when trying to molt when they get too big, but the whale lobsters came up with a solution, instead of molting their entire exoskeletons in one go they slowly and gradually break off piece by piece and the membranes in the joints flake off, this means that molting doesn't require any physical effort from the lobster and they don't go through a soft and vulnerable stage because when an old piece of exoskeleton breaks off the new piece is already hardened. in the rare case of a stubborn piece that doesn't want to come off they breach out of the water to remove it.

You can see how their bodies have adapted to a life in the open ocean, their bodies are streamlined and they have developed a sort of dorsal fin in their third abdominal segment, the 3rd, 4th and 5th pairs of legs have flattened and now are used as flippers, most of their pleopods or swimmerets are now vestigial stumps because they swim with an up and down motion aided by the very large uropods, and the last pair of pleopods are used as stabilizers and rudders.

As with modern lobsters you can tell their sex by looking at their pleopods, if all but the last pair are just small stumps then you're looking at a male, but if you see that the first two pairs look normal and fully functional then it is a female, they use them to hold their eggs after laying them, the eggs are large and they only lay about six of them, the embryos can take almost a whole year to develop and when they hatch the babies are cared for by their mothers until they reach half of their adult size.

Maybe this isn't as plausible as other spec evo crustaceans but i had a lot of fun making this drawing and i hope you guys enjoy it as well!!