The following fish can be sold for the listed amount of Bells to Tom Nook.

Amber: 1,200 Bells
Ammonite: 1,100 Bells
Coprolite: 1,100 Bells
Dinosaur Track: 1,000 Bells
Archaeopteryx: 1,300 Bells
Pecking Man: 1,100 Bells
Fern Fossil: 1,000 Bells
Dinosaur Egg: 1,400 Bells
Shark Tooth: 1,000 Bells
Trilobite: 1,300 Bells
T. Rex Tail: 5,000 Bells
T. Rex Torso: 5,500 Bells
T. Rex Skull: 6,000 Bells
Tricera Tail: 4,500 Bells
Tricera Torso: 5,000 Bells
Tricera Skull: 5,500 Bells
Mammoth Torso: 2,500 Bells
Mammoth Skull: 3,000 Bells
Ankylo Tail: 2,500 Bells
Ankylo Torso: 3,000 Bells
Ankylo Skull: 3,500 Bells
Apato Tail: 4,000 Bells
Apato Torso: 4,500 Bells
Apato Skull: 5,000 Bells
Dimetrodon Tail: 4,500 Bells
Dimetrodon Torso: 5,000 Bells
Dimetrodon Skull: 5,500 Bells
Iguanodon Tail: 3,000 Bells
Iguanodon Torso: 3,500 Bells
Iguanodon Skull: 4,000 Bells
Sabertooth Torso: 2,000 Bells
Sabertooth Skull: 2,500 Bells
Pachy Tail: 3,000 Bells
Pachy Torso: 3,500 Bells
Pachy Skull: 4,000 Bells
Parasaur Tail: 2,500 Bells
Parasaur Torso: 3,000 Bells
Parasaur Skull: 3,500 Bells
Seismo Tail: 4,500 Bells
Seismo Hip: 4,000 Bells
Seismo Chest: 4,500 Bells
Seismo Skull: 5,000 Bells
Plesio Torso: 4,500 Bells
Plesio Neck: 4,500 Bells
Plesio Skull: 4,500 Bells
Stego Tail: 4,000 Bells
Stego Torso: 4,500 Bells
Stego Skull: 5,000 Bells
Ptera Right Wing: 4,500 Bells
Ptera Left Wing: 4,500 Bells
Ptera Skull: 4,000 Bells
Icthyo Torso: 2,000 Bells
Icthyo Skull: 2,500 Bells
Rapter Torso: 2,500 Bells
Rapter Skull: 3,000 Bells
Styraco Tail: 2,500 Bells
Styraco Torso: 3,000 Bells
Styraco Skull: 3,500 Bells