Spines developed separately in basically every flight at least once. It’s after all a good defensive measure, especially for small dragons like Faes or Spirals.
Some flight’s spines however have special adaptions.
Plague are often poisonous.
Nature spines excrete pheromones that make the dragon especially alluring.
Light spines are often almost crystalline in structure, allowing the dragons to use them either as a distraction in battle or as a mating signal. After all, now they can literally project rainbows.
Lightning spines tend to be larger and work as little lightning rods (naturally).
Shadow spines are poisonous, similarly to Plague ones, but Shadow poison tends to be hallucinogenic. Allegedly young dragons have taken to licking the spines of sleeping Shadow Guardians.
Fire spines are often hot to the touch because they allow a dragon to beter regulated body heat. In Ice the effect is similar but instead of getting rid of excess body heat, Ice dragons use the spines (often in a dark color) to collect sun rays and thus extra heat.
Water and Wind spines are often elongated if compared to other flights because the spines allow them better stability in flight or in dangerous currents.
Earth spines help a dragon borrow into the soil, almost like saw teeth.
Arcane spines often appear to be made from the same crystals as the Starfall Isles and often conduct magical energies especially efficient.