Bats are surprisingly long-lived creatures,some having a life span of around 20 years.请问,其中的状语some having a life span of around 20 years中,some是什么成分.

问题描述:

Bats are surprisingly long-lived creatures,some having a life span of around 20 years.
请问,其中的状语some having a life span of around 20 years中,some是什么成分.