dotted quarter note
A quarter note that has at least one dot placed to the right of it. The dot denotes that the note's length is increased by half of its original value. In general, a note can have up to three dots. Subsequent dots add progressively halved value.
You can see one in the upper right corner of Danbooru post #150483.
Not to be confused with staccato, where the dot is placed above or below a note.