What is the fastest dino on the index?
Dimorphodon, SPD 30, orange header, wave 80, $320. Compsognathus is the fastest early card at SPD 26.
Later waves
Past wave 37 the index stops being cheap, bosses get huge HP and tiny SPD, and the timer shop finally has prices that match a long run.
Updated

Early dinos are fast. Compsognathus is SPD 26, Troodon is SPD 23, Microraptor is SPD 21. Bosses are not. From Titanhorn at 3.5 down to Grovebreaker at 2.8, the red cards crawl. Your late index dinos mostly sit at SPD 11 to 15. Dimorphodon is the exception that is actually on a card: DINO - WAVE 80, SPD 30, HP 1.4K, DMG 95, $320.
If a late wave is leaking fast dinos and your board is Ankylosaurus, Triceratops, and Titanosaurus, you stacked HP and DMG and left speed behind. Dimorphodon is the index answer. It is orange, wave 80, and cheaper than Diplodocus ($855) and Titanosaurus ($1,156).

Wrecker at wave 70 is HP 23K. Skyreach at wave 90 is HP 25K. Grovebreaker at wave 250 is HP 30K, DMG 120, SPD 2.8, $4,000. Your best damage-per-dollar dino, Ankylosaurus, is DMG 140 on a body with HP 580. The boss HP and the dino HP are not the same scale. You need many cards firing, plus traps whose text says they hit a lane or slow a crosser.
Spine Roller says it grinds the whole lane, at $240000 on the restock we saw. Tar Pit says anything crossing it crawls, at $180000. Those sentences match a slow, fat boss better than another SPD 11 tank does. They are still a rotating stock. Open ELITE TRAPS and read the live row before you treat this paragraph as a menu.
Two different rows talk about fixing things. Bone Mender, Epic, $17500, x1 Stock: Repairs your most damaged defences. Salvage Crane, Legendary, $300000, x1 Stock: Rebuilds your destroyed traps mid-run. The crane is for a trap that is already gone. The mender is for one that is hurt. Buying the crane first, with no trap down, spends $300000 on a sentence that cannot trigger.
Neither row shows a repair amount. We do not know how many hit points come back. Place them because of the sentence on the row, and judge them in the run, not from a made-up heal number.

On the cheaper shop, Pterodactyl Perch was Epic, $20000, Out of Stock, with the line Dive-bombs the farthest dino, at any range. That is the shop's answer to something standing at the back of the lane. It is not Dimorphodon and it is not on the index.
Out of Stock means the sentence was visible and the buy was not. If your shop shows the perch in stock, the price on that live row wins over the $20000 from this clip. x1 Stock and Out of Stock are the two stock lines these shops use.

HATCH [E] costs 79 of the hexagon currency, not cash. Galaxy Rex is 5.7% on that panel. Ancient Protector is 36.4%. A late-wave player who spends every hexagon on the egg is choosing the 5.7% portrait over Tar Pit's slow. That can be right if the board is already fine. It is a bad first move if wave 70 Wrecker is still walking through.
Frost Egg at $10000 in cash is the other egg, and it has no percent table. $10000 is less than Bone Mender and far less than Tar Pit. It is still more than the entire orange index trio if you add Dimorphodon, Diplodocus, and Titanosaurus ($320 + $855 + $1,156).
It is not a script, and it is not a code. The top bar does not grow a Codes button at wave 50. It is not the marketing art that puts a silly DPS number on a tower. The official promo shots are not the index. DMG on this site is the orange pill, and the highest one on a dino card we read is Titanosaurus at 145, then Ankylosaurus at 140.
It is also not a level grind. Cards do not show levels. When a patch adds a card, the 33/33 counter is the tell. Until that counter moves, the route above is the whole index plus one shop restock and one trap restock.
FAQ
Dimorphodon, SPD 30, orange header, wave 80, $320. Compsognathus is the fastest early card at SPD 26.
Only if traps are already dying. The row says it rebuilds destroyed traps mid-run. Tar Pit and Spine Roller are the rows that do the work the crane would rebuild.