What is "ancalagon"

Ancalagon may refer to:

• Ancalagon the Black, a dragon from the works of J.R.R. Tolkien
• Ancalagon (genus), a Cambrian priapulid worm
• Ankalagon saurognathus, a Paleocene mesonychid mammal, originally named Ancalagon and later renamed

Ancalagon minor is an extinct priapulid worm known from the Cambrian Burgess Shale. Because it superficially resembles the modern-day internal parasites known as the acanthocephalids or "spiny-headed worms," A. minor was once thought to be, or once thought to resemble the hypothetical free-living ancestor of acanthocephalids.

Along with the other Cambrian worms such as Ottoia, Selkirkia, Louisella, Fieldia, Scolecofurca, and Lecythioscopa, the organism may fall into a clade termed "Archaeopriapulida," a stem group to the Priapulids proper. However, the morphological similarity of these organisms to their modern cousins is remarkable, especially for the Burgess Shale. A phylogenetic analysis does not provide a great deal of resolution to the relationships between these basal worms.

The generic name is a homage to the dragon Ancalagon, who is featured in J.R.R. Tolkien's Middle-earth legendarium, in reference to the worm's prominent rows of hooks on its proboscis. The species was previously referred to as a member of the genus Ottoia, as Ottoia minor, but was then removed by Simon Conway Morris, who noted morphological differences.