Seashell Fragment Project!

I just made my first project! (and my first topic) so I’d really love to have some input on some of the definitions I made up. I’d also like to know what other taxa commonly encounter IDable fragments on iNaturalist and if you think a project for fragments across more or for other taxa would be beneficial.
here’s what I have typed in the project at the moment:

There is a great number of seashell species posted to iNaturalist as fragments and many of them can be identified to species. Learning how to identify fragments forces one to look at tiny details that are usually not worth analyzing when other indicators are present. This can be a fun way to challenge your ID skills! Unfortunately, it didn’t make it to the list of new annotations, but that’s okay, that’s why we have projects!

Definitions (please tell me if you think they need improvement)

All categories: There should be minimal tissue left in the fragment (for the sake of being a shell). Freshwater mollusks are welcome even though they’re not “sea” shells but just shells.

Bivalve shells: at least 50% of the shell is missing (50% of one of the two valves)
Gastropod shells: the shell lacks a complete or undamaged spiral. I’d like to lump operculum in here.
Chiton shells: an isolated plate
Tusk shells: does not make a complete tube
Sand dollar & sea urchin shells: at least 50% is missing. I’m lumping in teeth and spines here.
Crab & barnacle shells: single limb or isolated carapace (again, minimal tissue present aside from ligaments)

Not counted:
Coral: are colonial so don’t really have distinct fragments.



Defining fragment seems a little subjective, but I think saying anything less than 50% of the original shell makes sense. Probably don’t want to make it too complicated.


Cool project! I would assume limpets would follow the 50% rule too?


I agree, I think slipper snails and limpets would follow the 50% rule; the complete or undamaged whorl rule doesn’t make any sense for them. I will correct it, thanks!

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When I read

I initially thought it meant there should be some tissue left in the fragment. Suggest to reword as “There should be little or no tissue left in the fragment”


Here are some common fragment species that need work (for my sake and if anyone wants to help) I’m sure there are a lot more around the world but these are the species I am familiar with from the southeastern US. I tried to sort of put them in order of how common they are found fragmented.

Please add to the list if you know of more so I can try to work on them. Thanks!

Giant Atlantic Cockle
Flame Streaked Box Crab
Giant Hermit Crab

Florida Fighting Conch
Scotch Bonnet
Lightning Whelk
Shark eye
Lettered Olive
Knobbed Whelk
Eastern Banded Tulip
Atlantic Fig Snail

Channeled Duck Clam
Sawtooth Pen Shell
Stiff Pen Shell
Northern Quahog
Southern Quahog
Turkey Wing
Mossy Wing
Yellow Prickly Cockle
Florida Prickly Cockle

CRABS: (I’m not very familiar with crabs)
Dolly Varden Crab
Florida Stone Crab
Speckled Swimming Crab
Atlantic Sand crab
Atlantic Blue Crab

Sand Dollars (most not IDed to species)
Variegated Sea Urchin

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Thanks, I will do that!

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Looks like a useful project.

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I’m always in favor of efforts to make a difficult category of ID more possible. Whether it’s shell fragments, plants out of season, leaf mines, or anything else – it’s projects like yours that create greater understanding and in the long term make these ‘tough’ IDs more practical and approachable.


Perhaps I should have called the topic “Fragment Project” because I truly would like to know if other taxa have fragments that are posted frequently. I am, however, very grateful for all the support everyone has given!!!

I suppose it may just be that only seashells have any significant volume of fragments. I guess it’s not like you’re just walking along and there’s just a spider leg or beetle elytra laying there and for some reason, you decide to post it AND an expert is somehow able to ID it to species.

I guess If that is true, creating a “fragment” under “evidence of organism” really would only be warranted for mollusks (I have found several cephalopod fragments too). I’m also not crazy about the idea of mammal fragments because being able to sort for monkey limbs kinda feels weird😜.

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