Hyolithids

"a dark spear shape with a rounded head at the top molded into a rock"Hyoliths are an extinct group of animals that had cone shaped shells.  They lived from the Cambrian to the Permian, but were most diverse and abundant during the Cambrian.  Most paleontologists think that they lived on the sea-floor, did not move around much, and fed on organic material in the sediment (deposit feeders).  Many paleontologists agree that hyoliths are related to mollusks, though the closeness of this relationship remains in dispute.

Three species of hyolithids known from the Cambrian of Utah include:

  • Haplophrentis reesei Babcock & Robison, 1988
  • "Hyolithes" idahoensis Resser, 1938
  • "Hyolithes" comptus Howell, 1946

Many specimens are well-preserved and show the distinctive cone-shaped shell, the operculum (a “trap-door” that covered the front end of the animal), and the paired spines called “helens”, which are thought to have been used for stabilization on the sea-floor.

Gallery of Hyolithids

Note: Marks on all scale bars are centimeters (cm).

Haplophrentis reesei Babcock & Robison, 1988

Gray rock with a darker gray shaped like a spear with a circle head that is pointing in the left direction

KUMIP 204339 (Holotype). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figures 5.2 and 6.5 in Babcock & Robison (1988).

a close up of a gray rock that has a dark gray circle and a spear shape that is pointing in the bottom left corner

KUMIP 204340 (Paratype). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figures 5.1 and 6.4 inBabcock & Robison (1988) .

a gray rock with a outline of a spear shape pointing up

KUMIP 204341 (Paratype; part and counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figures 5.3 and 6.6 in Babcock & Robison (1988).

a close up of a gray rock with a pizza shape in the middle that is pointing up

KUMIP 204342 (Paratype; operculum only). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 5.4 in Babcock & Robison (1988).

a triangle rock pointing down with a circle an indent circle in the middle and a triangle beneath it that is pointing down

KUMIP 204343 (Paratypes; two specimens). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 1.1 in Babcock & Robison (1988).

a close up of a gray rock with a indention of a half circle that is connected with a long triangle at the bottom

KUMIP 204352 (Paratype). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 1.2 in Babcock & Robison (1988).

a close up of a yellow rock with a deformed half circle connected by a long triangle pointing down

KUMIP 204383 (Paratype; part and counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figures 5.5 and 6.1 in Babcock & Robison (1988).

a close up of a yellow rock with a half circle that has a chunk taken out that is connected to a long triangle that is pointing to the bottom right corner

KUMIP 204384 (Paratype; part and counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figures 5.6 and 6.3 in Babcock & Robison (1988).

"Hyolithes" idahoensis Resser, 1938

a close up of a gray rock that has a smooth gray circle in the middle and a pizza slice outline in the circle

KUMIP 204346 (operculum only). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 9.3 in Babcock & Robison (1988).

a close up of a rock with a yellow deformed half circle connected by a long triangle pointing down

KUMIP 204385 (Part and counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figures 9.1a and 9.1b in Babcock & Robison (1988).

a close up of a corner of a rock with a outline of a half circle connected with a long triangle

KUMIP 204345. Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 9.2 in Babcock & Robison (1988).

"Hyolithes" comptus Howell, 1946

a close up of a yellow rock with a indention of a half circle that is connected with a long triangle at the bottom
KUMIP 204344. Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 8 in Babcock & Robison (1988).