Home > Haplophrentis carinatus
3D animation of Haplophrentis carinatus.
Animation by Phlesch Bubble © Royal Ontario Museum
3D model of Haplophrentis carinatus.
Animation by Phlesch Bubble © Royal Ontario Museum
Haplophrentis carinatus (ROM 60747). Several small individuals preserved in the gut of the priapulid worm Ottoia prolifica. Length of largest specimen = 7 mm. Specimen wet – direct light. Raymond Quarry.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Haplophrentis carinatus (ROM 39305). Aggregates of skeletal elements possibly representing gut contents or coprolites. Aggregate length = 128 mm. Specimen dry – direct light (top left) and coated with ammonium chloride sublimate to show details (bottom left and right). Walcott Quarry talus.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Haplophrentis carinatus (ROM 45288). Small individual showing conch, operculum and helens. Specimen length = 15 mm. Specimen dry – direct light (left), wet – direct light (middle) and coated with ammonium chloride sublimate to show details (right). Walcott Quarry talus.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Haplophrentis carinatus (ROM 45302). Isolated operculum and two conchs on the same slab surface. Operculum width = 8 mm, length of largest conch = 18 mm. Specimens coated with ammonium chloride sublimate to show details. Walcott Quarry talus.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Haplophrentis carinatus (ROM 59943). Large individual showing conch, operculum, Helens and potential gut trace. Specimen length = 26 mm. Specimen dry – direct light (left), wet – polarized light (right). Stanley Glacier.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Haplophrentis carinatus (ROM 8463a, 8463b) – Lectotype and paralectotype. Figures 5a and 5b of Matthew (1899) and photographs of original specimens, a conch in ventral view (top right) and an incomplete operculum (bottom right). Specimen lengths = 19 mm (conch), 5.5 mm (operculum). Both specimens dry – direct light. Trilobite Beds on Mount Stephen.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Haplophrentis belongs to a group of enigmatic cone-shaped to tubular fossils called hyoliths that are known only from the Palaeozoic. Their taxonomic position is uncertain, but the Hyolitha have been regarded as a separate phylum, an extinct Class within Mollusca (Malinky and Yochelson, 2007), or as stem-group molluscs.
Haplophrentis – from the Greek haploos, “single,” and phrentikos, “wall,” in reference to the single wall within the shell.
carinatus – from the Latin carinatus, “keel-shaped,” referring to the morphological similarity to the bottom of a boat.
Burgess Shale and vicinity: none
Other deposits: H. reesei Babcock & Robinson, 1988 (type species), from the lower Middle Cambrian Spence Shale and elsewhere in Utah; H.? cf. carinatus from the Middle Cambrian Kaili deposit in China (Chen et al., 2003).
The Walcott, Raymond and Collins Quarries on Fossil Ridge, the Trilobite Beds on Mount Stephen and Stanley Glacier in Kootenay National Park.
Matthew described Hyolithes carinatus from the Trilobite Beds in 1899 based on five incomplete specimens. Babcock and Robison (1988) reviewed the original fossils, along with additional specimens collected by the Royal Ontario Museum from various Burgess Shale localities. They concluded that the species carinatus didn’t belong in Hyolithes, and established a new genus, Haplophrentis, to accommodate it.
Like all hyoliths, Haplophrentis had a weakly-mineralized skeleton that grew by accretion, consisting of a conical living shell (conch), capped with a clam-like “lid” (operculum), with two slender, curved and rigid structures known as “helens” protruding from the shell’s opening. The function of these helens is still debated, but one possibility was to allow settlement and stabilization on the sea floor. Haplophrentis had a wiggly gut whose preserved contents are similar to the surrounding mud.
H. carinatus usually grew to around 25 mm in length, although some specimens reached as much as 40 mm; the species is distinguished from H. reesei, its cousin from Utah, by the faint grooves on its upper surface, the more pronounced net-like pattern on its “lid” (operculum), and its wider, more broadly-angled living shell (conch).
Haplophrentis can be distinguished from the similar hyolith genus Hyolithes because it bears a longitudinal wall running down the inner surface of the top of its living-shell.
Haplophrentis is relatively common on Fossil Ridge and in the Walcott Quarry in particular, accounting for 0.35% of the community there (Caron and Jackson, 2008).
Haplophrentis probably moved very little; its helens appear unsuited for use in locomotion (See Butterfield and Nicholas, 1996; Martí Mus and Bergström, 2005; Runnegar et al., 1975). Whilst Haplophrentis feeding mode remains somewhat conjectural, it probably consumed small organic particles from the seafloor. Numerous specimens have been found in aggregates or in the gut of the priapulid worm Ottoia prolifica suggesting Haplophrentis was actively preyed upon and ingested (Conway Morris, 1977; Babcock and Robison, 1988).
BABCOCK, L. E. AND R. A. ROBISON. 1988. Taxonomy and paleobiology of some Middle Cambrian Scenella (Cnidaria) and hyolithids (Mollusca) from western North America. University of Kansas Paleontological Contributions, Paper, 121: 1-22.
BUTTERFIELD, N. J. AND C. NICHOLAS. 1996. Burgess Shale-type preservation of both non-mineralizing and “shelly” Cambrian organisms from the Mackenzie Mountains, Northwestern Canada. Journal of Paleontology, 70: 893-899.
CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.
CHEN, X. Y. ZHAO AND P. WANG. 2003. Preliminary research on hyolithids from the Kaili Biota, Guizhou. Acta Micropalaeontologica Sinica, 20: 296-302.
CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.
MALINKY, J. M. AND E. L. YOCHELSON. 2007. On the systematic position of the Hyolitha (Kingdom Animalia). Memoir of the Association of Australasian Palaeontologists, 34: 521-536.
MARTÍ MUS, M. AND J. BERGSTRÖM. 2005. The morphology of hyolithids and its functional implications. Palaeontology, 48:1139-1167.
MATTHEW, G. F. 1899. Studies on Cambrian faunas, No. 3. Upper Cambrian fauna of Mount Stephen, British Columbia. The trilobites and worms. Transactions of the Royal Society of Canada, Series 2, 4: 39-66.
RUNNEGAR, B., J. POJETA, N. J. MORRIS, J. D. TAYLOR, M. E. TAYLOR AND G. MCCLUNG. 1975. Biology of the Hyolitha. Lethaia, 8: 181-191.