That riff is called a montuno. It is actually only a snippet of a montuno because a montuno is generally a repetitive rhythmic pattern that extends over many bars and also outlines the harmony with the pitches used. It is played mostly by the piano in Afro Cuban, Salsa and Latin Jazz. Over the years this type of pattern has spread into other Latin and non-Latin styles as well. Sometimes it is just single notes played in both hands and other times it can combine single notes with 2 or 3 note chords. It can be clave based (two bars long) or non-clave based (one bar long). This one in particular is a single note two bar clave based pattern. Clave is both an instrument, 2 sticks that are struck together and also the name of a 2 bar pattern that is the underlying pulse that other rhythm instruments base their patterns on. The pattern can start on either bar and is named for the number of notes in each bar, 5 total, either 3-2 or 2-3.
Below is what is played on the recording with one exception, I replaced the final note, C# with D to make it a better looping pattern. The descending aspect of the pattern comes from the chords, written above. The 2-3 clave on which this pattern is based is in the staff below for reference:
