posasen
Imperfecto de subjuntivo para el sujetoellos/ellas/ustedesdel verboposar.

posar

Otras veces, se posaban o se anclaban al terreno, pero con independencia de él, como si se posasen elegantemente desde el cielo o emergieran abruptamente de él.
Other times, they were settling or they were anchoring to the area, but with independence of him, as if they were settling elegantly from the sky or were emerging abrupt of him.
Palabra del día
el guion