Gracile alien fauna - chordate brainstorm

The second brainstorming page deals with the gracile alien’s closer relatives, the local “chordate” analog.

The topmost drawing labeled “Base Terran chordate” is, of course, an amphioxus. Below it is the alien analog. It is still very crude at this phase, but there already is the repurposing of the top pair of digestive channels to breathing, and the bottom pair to digestion. It’s an animal that went to swimming after being a crawling bottom dweller, so it’s symmetry was broken on the dorsoventral axis first. There is also the first suggestion of the asymmetry of dorsal and ventral neural cords, which happened because I didn’t leave enough space for the dorsal cord between the notochord and the gill, but which I liked and kept. Happy accident!

Lots of notes to self about problems with the design and possible justifications and implications follow.

On the bottom, there’s a reminder of the apparent evolution of Terran chordates from the Vetulicolia. What did the alien “chordate” evolve from?