托福 考试写作之历年托福 考生优秀范文14
A Rare Fossil Record
The preservation of embryos and juveniles is a rate occurrence in the fossil record. The tiny， delicate skeletons are usually scattered by scavengers or destroyed by weathering before they can be fossilized. Ichthyosaurs had a higher chance of being preserved than did terrestrial creatures because， as marine animals， they tended to live in environments l
