Fossilized Spine

A column of interlocking vertebrae.
Overview
The Fossilized Spine is an item that can be obtained by fishing in the river at the Dig Site. It is one of the fossil items associated with Ginger Island content and can be useful both for collection completion and for several crafting and tailoring-related uses.
It can be donated as part of the Large Animal fossil for the Island Field Office. Completing that specimen rewards 6 Golden Walnuts and a 
The Fossilized Spine also has a few practical uses outside of donation:
- It can be processed in the
Bone Mill to produce
Quality Fertilizer,
Speed-Gro,
Deluxe Speed-Gro, or
Tree Fertilizer.
- It is used on the spool of a
Sewing Machine to create the Skeleton Shirt.
- It can be used in dyeing as a yellow dye item at the dye pots in
Emily's and
Haley's house at 2 Willow Lane.
It may also be relevant during the Special Orders quest Fragments of the past, in which 
Because it has multiple downstream uses, the Fossilized Spine is worth keeping until the Island Field Office fossil collection is complete and any desired crafting or tailoring recipes have been made. After that, excess copies can be converted through the Bone Mill or used for dyeing and clothing production.
Official description
A column of interlocking vertebrae.