Agnostids the extinct marine animals

The reading and the lecture are both about agnostids, a group of extinct marine animals. The author has tree theories how agnostids may have lived. The lecturer has three weaknesses about these theories. According to the reading agnostidy may have been free-swimming predators. The lecturer challenges this argument. Predators have large developed eyes but agnostids had weak eyes even blind. There is no evidence that other sensors could enable them to be predators. Secondly, the author means that they have may lived on the seafloor due to other types of primitive arthropods. The lecturer, however, asserts that seafloor creatures tend to be slow. In case of agnostids this is not so by reason that they are spread in a lot of areas. In consequence, that means that they moved fast from one to another one. For this reason, it is highly unusual that they were seafloor creatures. Finally, the author posits that there is the possibility that the agnostids were parasites. In lecture, the lecture’s stance is that is unlikely. Parasites don’t live in large groups but there is evidence that agnostids were in large groups. A certain amount of parasites can kill the host.