Learn Finnish: Uusi laji on matelija, ja se on väriltään vihreä. - The new species is a reptile, and it is green in color.

The word väriltään is an example of the ablative of respect. It is formed from the noun väri (color), plus the ablative case ending -ltä, and finally the third-person possessive suffix -än (its). Together, they literally mean 'from its color', which we translate naturally as 'in color' to specify exactly which quality of the reptile is green.

Is it mandatory to include the possessive suffix -än at the end of väriltään?

Yes, for this specific grammatical structure. The ablative of respect always requires a possessive suffix to link the quality back to the subject. Without the suffix, saying väriltä would sound incomplete or incorrect, as it would just mean 'from a color' rather than 'by its color'.

Could I just say ja sen väri on vihreä instead of using väriltään?

Absolutely. Saying ja sen väri on vihreä (and its color is green) is grammatically correct and perfectly natural. However, using väriltään vihreä is a very common, slightly more elegant way to express this in Finnish, especially in descriptive or factual contexts like talking about a species.

The word matelija means reptile, but does it come from a verb?