Bacillaria paxillifer (or Bacillaria paxillifera) is a colonial diatom species in the family Bacillariaceae.

[3] Bacillaria have a unique form of colonial motility among diatoms.

[3] Individual cells (with their long axes parallel to one another) slide against their neighbors in a coordinated fashion, allowing the entire structure to expand or contract.

[5] It was separately described two years later (1788) by Johann Friedrich Gmelin as Bacillaria paradoxa.

(1951), was established based on rules of priority.