Vicious saucebacks

The vicious saucebacks, formerly known as the western saucebacks, were a clade of basal saucebacks native to the former Glicker supercontinent in what is now eastern Darwin. They had many anatomical differences from modern saucebacks, such as four jaws derived from elongated gums; a mobile, protruding ischium forming the first segment of the leg instead of the femur; and a partially external skeleton. They were all fairly large creatures, which was ultimately their downfall as they became extinct as a result of the impact event at the end of the Somanian period.