I guess it is my turn to be that guy. None of those graphs should be line graphs. There is no continuous X variable.
I agree that a stacked bar graph would be nice, since the focus is on the per-species total across all 8 tooth types. Could you explain why a line graph is bad for a discrete but ordered variable, like [Molars - Premolars - Canines - Incisors]?
In this case a line graph is bad because the line doesn't mean anything. It implies an extrapolation that doesn't actually exist.