[求助]请教一道prep题目，感谢！

A group of paleontologists recently announced that a site in Utah has yielded fossils of some of the biggest armored dinosaurs ever found, and that they were at least 25 million years older than any similar dinosaur type previously found in North America.

(A) and that they were at least 25 million years older than any similar dinosaur type previously

(B) and they are at least 25 million years older than those of any similar dinosaur type that previously was

(C) and the fossils are at least 25 million years older than any similar dinosaur types that previously were

(D) fossils that are at least 25 million years older than those of any similar dinosaur type previously

(E) fossils at least 25 million years older than similar dinosaur types previously

答案是d。比较的含义我已经清楚了，此恐龙化石和彼恐龙化石作比较，疑惑的是把正确答案带入句子后，逗号前和逗号后的句子不是run-on sentences 吗？两个句子之间没有什么联系了阿。

谁能帮我澄清，解答下，谢谢啦！

逗号后面的部分是同位语，补充说明前面的fossils

这是名词重复性同位结构~~