Two halves and a hinge. That is as far as this goes.
First checkTwo halves with a hinge along the top edge, or one coiled shell?
Two hinged shell halves that close on the animal. In the hand it is quick: you can see the seam and feel the hinge, and a live one pulls its shell shut. The one two-shelled lookalike, the clam shrimp, has jointed legs and feathery antennae.MDC-FINGERNAIL-CLAMS, MDC-FRESHWATER-MUSSELSDispute
That is also where the honesty runs out. A young Asian clam can be mistaken for a fingernail clam, and what separates them is raised ridges and a thick shell, on a shell a few millimetres across. That is the distinction that matters ecologically — it is the native-or-invasive one — and at that size it is easy to get wrong.MDC-FINGERNAIL-CLAMSDispute
So this entry exists to stop a clam being handed back as a snail, and to say plainly what it cannot do. It is the thinnest record in the set and it is published knowing it.Dispute
The tell
What settles it, and what settles against it.
Read off this record's own diagnostic weights, heaviest first. A structure near the top of the left column does most of the work on its own; one near the bottom only leans.
Argues for Clam (small freshwater bivalve)
Two hinged shell halves that close on the animal+7
Argues against it
A single coiled shell with a soft foot coming out of it-6
Fish-shaped forage silhouette (minnow / shiner / fry) — not an insect-5
Moving as a school or tight bait cluster, not as a single insect-4
Aquatic insect crawling on rock or debris-3
A structure at −4 or below is treated as a hard exclusion by the comparison tool rather than as a penalty: if you saw it, this group is ruled out and no amount of matching elsewhere brings it back. Run a comparison →
Life stages
What it looks like, stage by stage.
Clam (small freshwater bivalve) — Every stage — young are miniature adultsdrawn
A caddis case is built of glued grit and has a jointed head and legs coming out of it. A clam is a shell the animal grew, with nothing coming out but a foot.
Where in the column it mattersIn the substrate. At or just under the bottom. Some fingernail clams also crawl on submerged plants, but no source consulted places them in open water.
Read from the record's own position notes: at or just under the bottom substrate; sand, gravel and mucky bottoms.
What eats it
Which fish the dossiers actually name.
No reviewed dossier names this group. That is an absence in the dossier layer rather than a finding about the animal — four dossiers exist and only one of them names any forage group at all.
Nothing in the pattern layer is mapped to this group, so no presentation family follows from it here.
Not known
What this entry cannot tell you.
9 of them. The limits are part of what was reviewed rather than a disclaimer bolted on afterwards. An entry that hid them would be claiming more than it checked.
Written by the reviewer
Declared by the reviewerHonest at 'small bivalve' and no finer. A young Asian clam can be mistaken for a fingernail clam; raised ridges and a thick shell point to the Asian clam, but this guide does not make that call.MDC-FINGERNAIL-CLAMSDispute
Declared by the reviewerBivalves have no emergence, so there is no timing information here.Dispute
Declared by the reviewerThis record is honest at 'small bivalve' and no finer. A young Asian clam can be mistaken for a fingernail clam; raised ridges and a thick shell point to the Asian clam, but on a shell a few millimetres across that is easy to get wrong, and it is the distinction with the ecological weight, because it is the native/invasive one.MDC-FINGERNAIL-CLAMSDispute
Sources disagreeFingernail-clam size limits differ: Missouri's fingernail-clam page gives a maximum usually no more than half an inch, its mussel page three-quarters of an inch or less, and the Upper Midwest guide 2-20 mm.
Read off the record
Nobody typed these. They are fields that are empty, said out loud rather than left for you to notice from a section that simply is not there.
SeasonalityNo reference window is published for this group, so this entry says nothing about when it is available. That is an absence in the calendar layer, not a claim that the animal has no season.
PatternsNo fly pattern in the pattern layer is mapped to this group. Whether anything imitates it is not answered here.
What eats itNo reviewed species dossier names this group. Some dossiers describe forage in class terms — small forage, insects, bait — and those are shown below, but a class description is not a reviewed link to this group and none is claimed.
Sources
Everything above rests on 4 published pages.
These are every page behind this entry. Where a reviewer traced a line above to the pages that carry it, that line names them itself, with where the evidence comes from when it is narrower than the whole entry. A line with no names beside it rests on this list as a whole: nobody has yet checked which page carried it, and naming one would be a mapping nobody made.
A plate shows shape. It cannot show a gill beating, a mask firing, or an animal reversing into sand — so where motion is the field mark, the entry points at motion. These are demonstrations, selected by hand and by publisher. Nothing here is a source: it changes no score, no window and no reviewed claim.
Nature in Motion. The white foot extending between the valves and the siphons working — the soft parts a shell photograph never has.
Science media · external video · title read back from the publisher 2026-09-09
Carry it on
Take the group to the next step.
These send the class of animal and the water this record is documented in. They do not send a sighting, because this page does not have one — you have not told it what you saw.
Which fish in this kind of water are documented eating this class of forage, and how they behave when they are.
What this forage class asks of the setup — the weight it wants, and where the chain gives first.
Keep the group on the day's record, so a later entry can be compared against what you were looking at.
Found an error?
This entry was written and drawn away from your water. If something here is wrong, say so — the report is assembled in your browser and sent only if you send it.