Cambrobranchus, the earliest acorn worm

[Halichoeres]

Acorn worms form part of the living sister group to echinoderms, which in turn is the living sister group to the chordates if the deuterostome hypothesis is correct. But acorn worms have no hard parts and are extremely rare as fossils. This fossil was just described as the earliest known acorn worm, from the Cambrian of China. Meet Cambrobranchus pelagobenthos ('Cambrian gill of the seafloor'). I'll be interested to see what other Cambrian researchers have to say about it.


Appears to be open access: https://palaeo-electronica.org/content/2024/5163-origin-of-the-hemichordate-larva

[ceratopsian]

Yes, open access. How interesting to read of larvae and juveniles being preserved.