Why does the index skip some wave numbers?
The card prints the wave it belongs to. Plenty of waves have no new dino. Boss and mini-boss cards fill some of those gaps: Titanhorn at 10, Chompers at 20, Boulderback at 30, and so on.
Index
The left-side Dinos button opens DINO INDEX. The counter on the screen we read said 33/33. Every dino page on this site is one of those cards.
Updated

The left rail has three labels: Abilities, Shop, and Dinos. Dinos is the bottom one, under a gray dinosaur head. That button opens the index. Shop opens the rotating defense list, which uses Rare, Epic, and Legendary instead of the index header colors.
Build a Dino Defense prints the index title as DINO INDEX. Two tabs sit under it, DINOS and BOSSES. On the DINOS tab the counter in the top right read 33/33. That is the full dino list we copied. Boss cards continue after you switch tabs or scroll past Titanosaurus, and they are not part of the 33.

A dino card puts the name on the left of the header and DINO - WAVE, plus the unlock wave, on the right. Microraptor says DINO - WAVE 7. Under the portrait, four pills run left to right: red HP, orange DMG, light-blue SPD, and a green dollar price. Microraptor's pills are HP 55, DMG 9, SPD 21, and $11.
If you already own the card, a green bar under the pills says CLAIMED. The index does not print Common, Rare, Epic, or Legendary on these cards. The color is the header bar. This site names that bar Green, Blue, Purple, Orange, Gold, or Red so the database can sort it. Those words are our labels for the bar you can see, not a second line of text on the card.

The header is a gradient, lighter through the middle, with a dark outline. The swatches below are mid tones sampled from that bar, and they are the colors used on the dino pages. Pill colors are separate: HP stays red, DMG stays orange, SPD stays blue, and the price stays green no matter which header the card uses.
Green is wave 1 through 9. Blue is wave 12 through 29. Purple starts at Juvenile Tyrannosaurus, wave 31, and runs through Brontosaurus at wave 59. Orange is Diplodocus, Dimorphodon, and Titanosaurus.
| Header | Swatch | Where it shows up |
|---|---|---|
| Green | #48CF62 | Wave 1 through wave 9 |
| Blue | #33ABFE | Wave 12 through wave 29 |
| Purple | #AA5DEC | Wave 31 through wave 59 |
| Orange | #FF8F1C | Diplodocus, Dimorphodon, Titanosaurus |
| Gold | #FFB92B | Mini-boss cards, not the 33 dinos |
| Red | #E6384D | Boss cards, starting with Titanhorn |
Oviraptor and Troodon both say DINO - WAVE 12. Oviraptor is HP 75, DMG 11, SPD 19, $16. Troodon is HP 55, DMG 12, SPD 23, $14. Same wave, different card. Troodon is the cheaper one and the faster one. Oviraptor has more HP.
Giganotosaurus and Juvenile Spinosaurus both say DINO - WAVE 52. Giganotosaurus is HP 1.8K, DMG 115, SPD 15, $462. Juvenile Spinosaurus is HP 1.6K, DMG 100, SPD 15, $387. If a guide tells you only one dino exists at wave 12 or wave 52, it skipped a card.

Divide the orange DMG pill by the green price. That is not a hidden game formula. It is a way to compare the cards you can already read. On the 33 dinos, Ankylosaurus is the outlier: DMG 140 for $92, about 1.52 damage per dollar, on a purple header at DINO - WAVE 37. Its SPD is 11, so it is slow.
Before wave 37 the best of that ratio is Pachycephalosaurus at wave 13: DMG 30 for $30. Pegomastax at wave 6 is DMG 7 for $8. Parasaurolophus at wave 17 is the other kind of buy: HP 380, but only DMG 15 for $55. Buy it when you want the red pill, not when you want damage per dollar. Dimorphodon at wave 80 has the highest SPD on the index, 30, with HP 1.4K, DMG 95, and $320.

The card has no level and no drop rate. Juvenile Tyrannosaurus shows HP 1.1K, not a level bar. A later update can add cards; the 33/33 counter is the check.
Shop prices do not belong in this list. Bone Mender and Tar Pit were on a timed restock. Royal Egg names are not index rows. Cash and Friend Boost are your run, not a dino's stats.

FAQ
The card prints the wave it belongs to. Plenty of waves have no new dino. Boss and mini-boss cards fill some of those gaps: Titanhorn at 10, Chompers at 20, Boulderback at 30, and so on.
No. The header is the card color. The price pill is green on every card, including red boss cards. Read the header for the color, and read the pills for HP, DMG, SPD, and price.