You are given a sentence and your task is to generate another sentence that supports the given input.

Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas, oil and coal production and incomplete fossil fuel combustion.
Archaeans produce methane gas as a waste product.

A spring is any natural situation where water flows from an aquifer to the earth's surface.
You call water that flows out of the ground where an aquifer meets the surface a(n) spring.

Arandaspids represent the oldest known craniates, a proposed group of chordates that contain all chordates with a cartilage-derived skull (i.e., lampreys, armored agnathans, and gnathostomes), and hagfish.

Hagfishes have a skull made of cartilage.