To help with the lab, there are a number of photos and diagrams ... of the gill slits until you reach the coracoid bar. Cut across the coracoid bar. Cut below the sinus venosus, leaving it intact.

But this new work suggests that modern-day fish may actually be the ones with the ancient gill structures. Shark gills are the gills that evolved. "That bucks a trend that's been in the literature ...

Now, a well-preserved, 325-million-year-old shark-like fossil from Paleozoic Arkansas shows how the skeletal structure that supports the gills of a very early shark resembles bony fishes much more ...