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Hatch MatchHook the Horizon · field intelligence

One question at a time

Start from what kind of animal it is.

The comparison needs you to name a structure. This asks instead — the way a specimen in a tray actually resolves — and tells you what is still standing after every answer.

Step 1

What kind of animal is it?

Asked first because a cue means nothing outside its class. 'Does it have three tails' is not a question about a shad, and the comparison does not score it as one.

Still standing

39 of 39 reviewed groups

In carrier order, unranked, with no score attached. A key narrows; it does not decide which of these is more likely, and neither does this list.

The whole key

What it asks, and where each answer lands.

Drawn from the same data the walk uses, so the arms are the real ones and the counts are the real counts. Notice how uneven it is: the fish side runs deepest because most of what a key has to separate here is small silver fish, and the shelled arm stops after one question because a coiled shell and a hinged pair are not a problem that needs one.

What kind of animal is it?A fish14The fin on its back — spines, o…A spiny front dorsal7What shape is the body?Deep and slab-sided, with a dark e…4Longer, with dark vertical bars3Cigar-shaped, blunt head, two dors…2One soft dorsal, no spines8Run a thumb along the belly.Sawtooth — it catches on a thumb3Which herring?A long thread trailing off the bac…1The eye is wider than the snout is…1A shoulder spot with rows of small…3Smooth8Two separate dorsal fins with a cl…5I can only say it is a small fish,…14It does not look like open-water b…4An insect — six legs, a head, a se…13What is at the back end?Three long filaments2Down the sides of the abdomen —…Plate-like or feathery gills along…1The three 'tails' are flat leaves,…1Two long filaments1Where are the gills?At the thorax or the leg bases — n…1It has wings — this one is out of …1One, pointing straight back1No long filaments at all11What is at the back end instead?It is carrying a case, or living i…1Hooks or prolegs it grips with3Fleshy lobes or a disc at a blunt …1A swollen rear stuck to a rock, bo…1Nothing — a plain soft rear, or an…9A crustacean — many legs, a hard s…6Which way is it squashed?Side to side — it falls onto its s…2Top to bottom — it lies flat and w…2It has pincers3None of those — a shrimp, a crab, …3Soft-bodied — no legs, no shell, n…3What is at the two ends?A sucker at each end1Bristle bundles along the segments…3It everts a proboscis with dark ja…1It has a shell of its own2Arms, and it changes colour1

The boundary, again

A shortlist of one is still a shortlist.

This key holds no biology of its own. Every branch names structures already in the reviewed reference set, and an animal appears on an arm only because its record scores that structure — so the key and the comparison cannot disagree, and a correction to the reference set changes both at once. A fixture fails the build if an arm strands a group or if a group reaches a question it cannot answer.

What it cannot do is conclude. It does not weigh your answers against each other, does not report a confidence, and does not know which structures you were unsure about. That is the comparison's work, and the button above is how you hand it over.