I created a tag called striped_quills, which I intended to use for porcupine images where either the individual quills are seen to be striped, like this:

post #3049907

and also for images where the collective mass of quills forms an overall striped pattern, like this:

post #3583953 post #3410752

However, after tagging a few images, I realised that the site isn't very clear about the difference between quills (anatomy) and spines. I think clarification is needed on when each of these tags should be applied.

What do wikis say?

The Wikipedia article https://en.wikipedia.org/wiki/Spine_(zoology) describes quills as a subset of spines. That suggests to me that we might ultimately need to have quills_(anatomy) imply spines.

The e621 wiki page for quills (anatomy) doesn't say much, and seems mostly to be there just to warn people against mixing them up with feathered pens:

This tag refers to the spikes/spines on an animal. For the writing utensil, use quill.

The wiki page for spines doesn't have any example images, but it's more widely linked to (e.g. the wiki page spikes links to it), and its text is more thorough:

Posts depicting needle-like protrusions in parts of a body.
Spines are found in both vertebrate and invertebrate animals alike, in mammals they are more commonly seen in hedgehogs and porcupines. Also found on some plants, such as cactuses.

Note that although animals such as hedgehogs are expected to have these, most of the anthro hedgehogs (such as the ones in Sonic the Hedgehog (series)) actually lack anything that could be tagged as spines.

That's a good point about cactuses: you wouldn't tag these two images with "quills":

post #4956607 post #5541540

Sonic

As for Sonic the Hedgehog's needles: earlier this year, I added a Sonic image to the wiki page for quills (anatomy), because AFAIK even though Sonic's quills/spines are very stylised, they are still pointy protrusions that should be tagged. (Now that I've seen the spines wiki page: personally, I disagree with its recommendation to avoid doing this.)

For reference, these are the number of Sonic images with each of the tags:

• Searching for quills_(anatomy) sonic_the_hedgehog gives ~750 results.
• Searching for spines sonic_the_hedgehog gives only ~75 results.

Previous discussions

Looking at other forum topics and BURs about quills and spines:

• https://e621.net/forum_topics/12055 - This one from 2016 requested aliasing quills -> spikes and was rejected. User Ryu Deacon commented: "I was actually under the impression that there was still some dabate over the precise definition of a number of tags that describe pointy protrusions on the body and slightly overlap, that includes tags such as spikes, barbs, thorns, ridges and spines."
• https://e621.net/forum_topics/56870 - A pending BUR from April 2025, requesting that head_spines, back_spines, and tail_spines should imply spines. The requester also mentioned needles_(anatomy) as a potential alternative tag.
• https://e621.net/forum_topics/43068 - A pending BUR from March 2024, requesting {color}_quills should imply quills_(anatomy).
• https://e621.net/forum_topics/37352 - A pending BUR from Feb 2023, requesting {color}_quills should imply quills (without the "(anatomy)" bit).

Questions

So, my questions are:

1. Should the tags quills_(anatomy) and spines both stay in use? Or is one of them redundant, and they should be combined?

2. If it's decided that they should both stay in use, does anyone have a clear explanation of the difference between them, which can be put on the wiki?

3. If they both stay in use, should spines be treated as the overarching tag, with quills_(anatomy), penile_spines, etc all implying it?

4. Should Sonic the Hedgehog be tagged with quills_(anatomy) or spines? The wiki page above says no, but I think he should, because even though they're stylised quills, that's what they represent.

5. Should striped quills (or striped spines, if that ultimately turns out to be the preferred tag) also be tagged with striped_markings? I feel like it should count as a "marking" if the collective mass of quills forms a striped pattern, but if we can see that each individual quill is striped along its length, it might not qualify.

To me, quills are made of keratine. They are long needle-like strands and are typically attached to the skin of a character. (counter examples would be shed, or throw quills during an action pose (think Megaman X's Sting Chameleon))

Spines are way more general. Plants can have spines (roses), can be spicules, can be dorsal-ridge-like formations.

Spine can also refer to a spinal column or the part of a book to which the pages are attached.

I don't think a fusion of spines and quills is warranted

bleakdragoon said:
To me, quills are made of keratine. They are long needle-like strands and are typically attached to the skin of a character. (counter examples would be shed, or throw quills during an action pose (think Megaman X's Sting Chameleon))

Spines are way more general. Plants can have spines (roses), can be spicules, can be dorsal-ridge-like formations.

Spine can also refer to a spinal column or the part of a book to which the pages are attached.

I don't think a fusion of spines and quills is warranted

here my takes on wiki definitions

Spines

Spines are stiff, pointed structures that can be found on animals and plants. Spines are usually modified scales made of keratin (the same stuff as claws and horns). They tend to be shorter, rigid, and often function as defensive armor.

In character art: Spines are usually depicted as short, thick, and often bony-looking. Think of them as back plating or rows of sharp nubs running along a dragon’s spine.

Tag tip: Use spines for characters with ridged, armor-like protrusions that don't look flexible or hollow.

Quills
Quills are a type of spine, but usually longer, flexible, and often hollow. They're most famously seen on porcupines, who use them as natural defense weapons. Quills can detach or bristle outward as a threat display.

In character art: Quills are typically drawn long and needle-like. They can sometimes be stylized like feathers. They may fan out, curve, or be arranged in expressive ways.

Tag tip: Use quills when the character has porcupine-style spikes—thin, possibly movable, and sometimes colored or patterned.

bleakdragoon said:
here my takes on wiki definitions

Spines

Spines are stiff, pointed structures that can be found on animals and plants. Spines are usually modified scales made of keratin (the same stuff as claws and horns). They tend to be shorter, rigid, and often function as defensive armor.

In character art: Spines are usually depicted as short, thick, and often bony-looking. Think of them as back plating or rows of sharp nubs running along a dragon’s spine.

Tag tip: Use spines for characters with ridged, armor-like protrusions that don't look flexible or hollow.

That description sounds more similar to the existing tags spikes (anatomy) and (for the blunter kind) head ridge/dorsal ridge/tail ridge.

chemistrynoisy said:

That description sounds more similar to the existing tags spikes (anatomy) and (for the blunter kind) head ridge/dorsal ridge/tail ridge.
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No, the each ridge definitions state clearly that they can not stab anything. Spines can pierce, that's what "pointed structures" strongly implies.

As for spikes, I agree both are practically the same and should probably be mergedOr you keep spine as the catch all since spikes are typically boney appendages on living characters

[edit]
Spike definitions indicates they are port of character anatomy and the example show the girthy-bony-solid kind of spikes/spines.