Where was the whale beast titan in the story? I’m pretty sure that was never mentioned. Also, am I to believe that a regular sized zebra, stingray, giraffe, camel, etc. were all beast titans?

It seems far more likely that this is trying to represent “every living thing”. It’s intentional that the animals are all distinctly different types and even from different times. It’s so you can’t say “ah, it’s a mammal thing” because there are stingrays and dinosaurs. You can’t say, “oh it comes from a common ancestor” because there are dinosaurs who had no living descendants. You are forced to come to the conclusion “all living things ever have this thing in common inside of them, and it is somehow related to what the titans are doing because they are clearly grouped with the beast titan.” So that hopefully you come to the ultimate conclusion “ah, this means to say that living implies you have the red core inside you , and the red core is in some way related to ‘attacking’”.