What does であったとされ mean in this sentence

Question

I’m reading a Wikipedia article about メガプテリギウス.

他のモササウルス類同様に肉食性であったとされ、小型で華奢な頭骨や細い歯を持つ特徴から主に小魚を餌としていたと考えられる

Answer 1

であった is the past tense of である, a form of the copula. So it means "was".

とされ is the masu-stem of the passive form of とする, which means something like "assume" or "decide". In this case, it refers to how the creature is classified by scientists.

肉食性であったとされ means something like "is thought to have been carnivorous". Here, the masu-stem (連用形) is used to continue the sentence. This is known as 中止法.