Its teeth and skeleton lead scientists to believe Spinolestes was a “ground dweller” that survived on a diet of bugs.

▲live (survive) on a diet of 的意思是“以吃……生存”。如：

He lived on a diet of water and tinned fish. 他仅靠喝水、吃鱼罐头过活。

The animals live on a diet of fruit and insect. 这些动物以水果和昆虫为食。

The Irish used to live on a diet of potatoes. 爱尔兰人过去以吃马铃薯为主。

They had to survive on a diet of insects and berries. 他们只好靠吃昆虫和浆果维持生命。

▲更句类似例句：

Cows have a diet of grass. 牛的食物是草。

He was put on a diet of milky food. 他按照医嘱要食用乳制品。

They were fed on a diet of rice and vegetables. 给他们吃的是大米和蔬菜。

The radio had fed him a diet of pop songs. 他从广播里听到的都是千篇一律的流行歌曲。

▲你的句子意思：它的牙齿和骨骼让科学家相信spinolestes是一种生活在地洞里以吃虫子为生的动物。