No there is lots of data, Twenhofel and Shrock wrote in 1935,
"About 150 species of living cephalopods are known, and fully 10,000 fossil
species have been described." William H. Twenhofel and R. R. Shrock,
"Invertebrate Paleontology, p. 394.
There are now known to be about 650 living species. I can not find the modern
count of extinct species, but in any event, the dead outnumber the living.
There is plenty of hard data and it is not all theory driven.
But this does raise a question for the PC guys. Why did God create so many
animals doomed to extinction? Why wouldn't He create the modern forms?
glenn