Everyone knows erect necked sauropods such as brachiosaurus, alamosaurus and others could physically not support their necks in this supposed vertical posture. So, clearly, the only way for this to have been achieved is a solution so obvious nobody has even thought of it.
I propose that sauropods held their necks aloft using large bags of lighter than air gas, ballooning from their throats. Seriously there's no other way.
I just concocted a sapient race of bipedal, wing-walking, volant, omnivorous, shaggy ceratopsians. Of course this was only possible if the K-T impact did occur, just... On a smaller scale.