Harrytoombsia was the ' little brother ' of the five - metre - long placoderm Dunkleosteus which preyed on its smaller relatives .
The five - metre - long placoderm Dunkleosteus is the giant shark - like fish of its time .
Harrytoombsia was the ' little brother ' of the five - metre - long placoderm Dunkleosteus , the giant shark - like fish of its time , which preyed on its smaller relatives .