Ancalagon minor (USNM 57646) – Holotype (part and counterpart). Left, plate 22 of Walcott (1911), showing a retouched image of the original specimen (upside down) (figure 5). Right, images of the same specimen showing a dark stain, probably representing decay fluids at the posterior end of the body. Specimen length = 70 mm. Specimen dry – direct light (top), dry – polarized light (middle, bottom). Walcott Quarry.
© Smithsonian Institution – National Museum of Natural History. Photos: Jean-Bernard Caron
Ancalagon belongs to the priapulid worm stem group (Harvey et al., 2010; Wills, 1998).
Ancalagon – from Ancalagon the Black, a dragon in Tolkien’s fantasy writings (The Fellowship of the Ring, 1954; The Silmarillion, 1977), in reference to the worm’s strong rows of hooks.
minor – from the Latin minor, “inferior,” in reference to the small size of the worm.
Burgess Shale and vicinity: none.
Other deposits: none.
The Walcott Quarry on Fossil Ridge.
Walcott (1911, 1931) described and illustrated several specimens of this species as “Ottoia minor.” However, this species was pulled from the genus Ottoia to Ancalagon by Conway Morris (1977) and re-described as a primitive priapulid worm; later studies showed that it belongs to the priapulid stem group (Harvey et al., 2010; Wills, 1998).
The tubular body of this worm can reach up to 11 centimeters and is divided into a finely annulated trunk and an anterior eversible mouthpart, called a proboscis. The proboscis bears strong hooks at the front, and smaller hooks pointing backwards posteriorly. Fine hair-like setae are present on the trunk. The gut is straight and the anus is terminal.
This species is rare – less than 20 specimens are known.
The tubular body-shape is well adapted for burrowing; Ancalagon probably used its spines to pull itself through the mud. The strong hooks at the front of the proboscis suggest a carnivorous feeding habit.
CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.
HARVEY, T. H. P., X. DONG AND P. C. J. DONOGHUE. 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution & Development, 12(2): 177-200.
WALCOTT, C. 1911. Cambrian Geology and Paleontology II. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(5): 109-145.
WALCOTT, C. 1931. Addenda to descriptions of Burgess Shale fossils. Smithsonian Miscellaneous Collections, 85(3): 1-46.
WILLS, M. A. 1998. Cambrian and Recent disparity: the picture from priapulids. Paleobiology, 24(2): 177-199.
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