TOEFL TPO 43 Integrated Writing Task

From the Agnostids fossils found in rocks it has been discovered that they were primitive arthropods-relatives. However, their eating habits and behavior is still unknown to paleontologists.The reading states a few theories about their lifestyle. The speaker on the other hand believer pointed out statements contain serious weaknesses.
To begin with, the reading asserts that this species could have been free swimming predators which feed on smaller animals. The speaker, however, opposes this assertion claiming that according to discoveries in contrast with other primitive arthropods who surfed the sea with the help of their big eyes, Agnostids had a tiny, poor developed eyes. This meant that they could have not used their sight to hunt smaller species for food supply and hunting could only be possible if they used another sense.

As well as that, although the passage holds this opinion that they could have dwelled on the seafloor, the speaker disapproves this idea demonstrating that seafloor dwellers are not capable of travelling fast or far.
They usually occupy a small area which is not likely to be the case for Agnostids. Fossils of this animal has been discovered in vast spots showing that it inhabited in distant areas so they could move.

Lastly, the passage claims that there is the possibility that they were parasites which prey on other larger organisms. The speaker disputes this theory offering an explanation. If parasites are a large population they can kill the animal they are feeding on. So the huge number of fossils found of this animal reassures us that this could not be their inhabiting style.