May not sound like news, but for the last 70 years, we've been making assumptions about human neurons based on measurements from squid neurons. That's not quite as ludicrous as it sounds--squid axons are enormous, and so for a long time, they were the only tractable system for learning much of anything about neurobiology.

However, technology has since advanced to the point that someone could finally make the same measurements on our near and dear mammalian cousin, the long-suffering lab rat, and found--surprise!--different results.

The New Scientist article linked above gives a great account of the study, except for one glaring error: they say that axons are "each 1 millimetre in diameter in the giant squid."

No one, as far as I know, has ever voltage clamped axons from giant squid. They use giant axons from regular squid, and these giant axons can indeed reach 1 mm in diameter. But the common market squid that have been generously providing their axons to generations of neuroscientists--well, they're only about 10 cm long.