Phylum Acanthocephala (Horny-Headed Worms, or Spiny-Headed Worms)

Approximate Number of Species: 1100

Macracanthorhynchus_hirudinaceus_adult_BAM1 — Adult of Macracanthorhynchus hirudinaceus at ~20 cm long. Image from Wikimedia Commons

Largest: Macracanthorhyncus hirudinaceus at a length of 25.59 inches (650 mm). M. hirudinaceus is intestinal parasite commonly found in pigs and thus often referred to as the “Giant Thorny-Headed Worm of Swine”.

Smallest: Males of Octospiniferoides chandleri obtain lengths of only 0.039 inches (1 mm)

References:

B. Nickol, personal communication

Bullock WL (1967) Octospiniferoides chandleri n. gen., n. sp. a neoechinorhynchid from Fundulus grandis Baird and Girand on the Texas Coast. Journal of Parasitology 58:290-297

Brusca RC & Brusca GJ (2003) Invertebrates (Sinauer Associates, Inc., Publishers, Sunderland, MA) 2nd Ed.