Symmetry of gliding reflection

Jorge Luis Borges noted that Sir Thomas Browne dismissed the Amphisbaena, a two-headed snake, because there could be no creature without a bottom, top, front, back, left and right.

I can find few creatures, real or imaginary, stranger than the Ediacarian biota (given, for now, that we take them to be animals and not something else).

Trilobozoa, for example, had triradial symmetry, while Yorgia had symmetry of gliding reflection.

What would Browne and Borges have made of them?



another image here.