Bivalved Arthropods

"a gray rock with a yellow stain in the middle"As their name implies, bivalved arthropods have an exoskeleton composed of two valves which surround much of their body. Living bivalved arthropods, such as the small ostracods, are crustaceans, the group that today also includes crabs, shrimps, and lobsters.

It is thought that many of the fossil remains of bivalved arthropods found in the Cambrian of Utah also belonged to either extinct groups of crustaceans, or groups closely related to crustaceans.

At least 10 genera of bivalved crustaceans have been recorded from the Cambrian of Utah. Click on the images below to explore this diversity.

Gallery of Bivalved Arthropods

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

Branchiocaris

a gray rock with a outline of a fish like shape in it and rib like structure inside

KUMIP 204797 (Part, counterpart). Marjum Formation, House Range, Millard County, Utah. Figures 5.1, 5.2 in Briggs & Robison (1984).

a tan rock and two yellow ovals with a spine like line in the middle

KUMIP 204795 (Part, counterpart). Marjum Formation, House Range, Millard County, Utah. Figures 7.3, 9.1 in Briggs & Robison (1984).

a gray rock with a smooth smudge in the middle that forms a circle

KUMIP 204796 (Part, counterpart). Marjum Formation, House Range, Millard County, Utah. Figures 7.1, 7.2 in Briggs & Robison (1984).

a eroded in half circle of a gray rock

KUMIP 204792. Marjum Formation, House Range, Millard County, Utah. Figure 9.2 in Briggs & Robison (1984).

a gray pot shaped mark on a rock with a diagonal line through it

KUMIP 204793. Marjum Formation, House Range, Millard County, Utah. Figure 9.3 in Briggs & Robison (1984).

a yellow pot shaped mark on a white rock

KUMIP 204794 (Part, counterpart). Marjum Formation, House Range, Millard County, Utah. Figure 9.4 in Briggs & Robison (1984).

a pear shaped mark on a gray rock

University of Utah (UU) 06011.06. Wheeler Formation, Drum Mountains, Millard County, Utah. Figure 13.1 in Briggs & Lieberman et al. (2008).

a pot shaped mark on a yellow rock

KUMIP 153897 (Part, counterpart). Wheeler Formation, Drum Mountains, Millard County, Utah. Figure 1.5 in Robison & Richards (1981).

a orange pot shaped mark on a tan shape

KUMIP 153898. Wheeler Formation, Drum Mountains, Millard County, Utah. Figure 1.6 in Robison & Richards (1981).

Canadaspis

a yellow corner of a rock with a small insect like body formed into the rock with legs and a tail

KUMIP 314077 (Part, counterpart). Wheeler Formation, Drum Mountains, Millard County, Utah. Figure 11 in Briggs & Lieberman et al. (2008).

a close up of a yellow rock and a outline of a peach like body

KUMIP 153896 (Part, counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah.

a close up of a gray rock with a circle like yellow smudge with a dark gray smudge within the yellow smudge

KUMIP 195725. Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah.

Dicerocaris

a gray rock with a yellow half circle smudge

KUMIP 134939 (Holotype; part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figures 1.1a, 1.1b in Robison & Richards (1981).

a gray rock with dark brown smudge with a flat top and a circle body

KUMIP 134940 (Paratype; part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figures 3.2a, 3.2b in Robison & Richards (1981).

a close up of a gray rock and a darker smudge in the middle that is a darker shade

KUMIP 134900 (Paratype). Wheeler Formation, Drum Mountains, Millard County, Utah. Figure 3.3 in Robison & Richards (1981).

Dioxycaris

a close up of a yellow and tan rock with a red outline of a half circle

KUMIP 153911. Ute Formation, Wellsville Mountains, Box Elder County, Utah. Figure 3.6 in Robison & Richards (1981).

a close up of a gray rock with a dark shade of a half circle

KUMIP 135145 (Part, counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 3.5 in Robison & Richards (1981).

Isoxys

a close up of a yellow rock with a half circle with red spots
KUMIP 312404. Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 14 in Briggs & Lieberman et al. (2008).

Pahvantia

While we have classified Pahvantia with bivalved arthropods, some have argued instead that these fossils are parts of an anomalocaridid.

a close up of a gray rock with a darker shade of a arrowhead shape pointing down

KUMIP 134878 (Holotype; part, couterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 8.2 in Robison & Richards (1981).

a gray rock with a yellow stain in the middle that forms a teardrop but has a big chunk in the top right taken out

KUMIP 134187 (Paratype). Wheeler Formation, House Range, Millard County, Utah. Figure 8.1 in Robison & Richards (1981).

bottom corner of a gray rock that has a yellow stain formed like a bottom of a arrowhead

KUMIP 134879 (Paratype). Wheeler Formation, House Range, Millard County, Utah. Figure 7.3 in Robison & Richards (1981).

Perspicaris

Two species of bivalved arthropod have been questionably assigned to the genus Perspicaris:

  • Perspicaris? dilatus
  • Perspicaris? ellipsopelta

Below we show the figured type specimens from the KUMIP collections that have been assigned to these two species. For details on non-figured paratypes of these two species, see Robison and Richards (1981).

a gray rock with a half circle outlined in the rock

KUMIP 135128 (Holotype). Wheeler Formation, House Range, Millard County, Utah. Figure 1.4 in Robison & Richards (1981).

a gray rock with a pot shape outline in the rock

KUMIP 135129 (Paratype). Wheeler Formation, House Range, Millard County, Utah. Figure 2.7 in Robison & Richards (1981).

a gray rock with a half circle and spots of non shaded rock on the half circle

KUMIP 135130. Wheeler Formation, House Range, Millard County, Utah. Figure 2.6 in Robison & Richards (1981).

a gray rock with a half circle with a dark shade of the half circle

KUMIP 135131 (Paratype). Wheeler Formation, House Range, Millard County, Utah. Figure 2.5 in Robison & Richards (1981).

a tan rock with a pot shaped dark yellow figure in the rock

KUMIP 153902 (Holotype). Marjum Formation, House Range, Millard County, Utah. Figure 2.1 in Robison & Richards (1981).

a yellow rock with a faint shade of black that makes a half circle

KUMIP 153903 (Paratype). Marjum Formation, House Range, Millard County, Utah. Figure 2.2 in Robison & Richards (1981).

a corner of a yellow rock with a peach shape dark yellowed figure in the rock

KUMIP 153904 (Paratype). Marjum Formation, House Range, Millard County, Utah. Figure 2.3 in Robison & Richards (1981).

a red rock with half circle shape that is darker shade of red

KUMIP 153905 (Paratype). Marjum Formation, House Range, Millard County, Utah. Figure 2.4 in Robison & Richards (1981).

Proboscicaris

While we have classified Proboscicaris with bivalved arthropods, some have argued instead that these fossils are parts of an anomalocaridid.

a close up of a gray rock with a yellow mark in the middle that has a round shape
KUMIP 153901 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 4.1 in Robison & Richards (1981).

Pseudoarctolepis

a gray rock with a breast like shape with wings on each side

KUMIP 135134 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 6.1 in Robison & Richards (1981).

gray rock with a dark gray smudge on it

KUMIP 135134 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 6.1 in Robison & Richards (1981).

a gray rock with a dark gray smudge that formed a circle

KUMIP 135135 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 4.4 in Robison & Richards (1981).

a gray rock with a yellow stain in the middle and a line coming out of it on left side

KUMIP 135138 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 6.2 in Robison & Richards (1981).

a gray rock with a black smudge in the middle with a wing on each side

KUMIP 135139. Wheeler Formation, House Range, Millard County, Utah. Figure 4.2 in Robison & Richards (1981).

a gray rock with a outline of a bug that forms a oval and can see that outline of bones

KUMIP 135142. Wheeler Formation, House Range, Millard County, Utah. Figure 5.5 in Robison & Richards (1981).

a gray rock with a big yellow stain in the middle of it

KUMIP 153912 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figures 4.3, 5.3 in Robison & Richards (1981).

a gray rock with a brown smudge and wings on each side

KUMIP 153913 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figures 4.5a, 4.5b in Robison & Richards (1981).

a gray rock with a brown smudge that is cut off at the middle

KUMIP 153914 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 5.1 in Robison & Richards (1981).

a close up of a gray smudge that forms a half circle

KUMIP 153915 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 5.2 in Robison & Richards (1981).

a close up of a gray rock with a dark gray smudge that formed a circle

KUMIP 153916 (Part, counterpart). Wheeler Formation, House Range, Millard County, Utah. Figure 5.4 in Robison & Richards (1981).

Tuzoia

Three species of large bivalved arthropods from the Cambrian of Utah have been assigned to the genus Tuzoia:

  • Tuzoia guntheri
  • Tuzoia retifera
  • Tuzoia? peterseni

Below we show the figured type specimens from the KUMIP collections that have been assigned to these three species. For details on non-figured paratypes of these species, see Robison and Richards (1981).

While the fossilized carapaces of Tuzoia are known from Cambrian soft-body deposits from around the world, most of the internal features of the animal (such as the appendages) remain unknown. It is thought that Tuzoia species probably lived in the water column, perhaps explaining their great distributions.

a red rock with a lighter tone in the middle that makes a half circle

KUMIP 134797 (Paratype; part, counterpart). Marjum Formation, House Range, Millard County, Utah. Figure 8.4 in Robison & Richards (1981).

a red rock with a outline of a hour glass shape

KUMIP 134798 (Paratype). Marjum Formation, House Range, Millard County, Utah. Figure 9.2 in Robison & Richards (1981).

a close up of a yellow rock with a pot shaped formed in the rock

KUMIP 144982 (Paratype). Marjum Formation, House Range, Millard County, Utah. Figure 8.5 in Robison & Richards (1981).

a gray rock with a darker shade that is pot shaped

KUMIP 153918 (Part, counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 8.3 in Robison & Richards (1981).

a gray rock with a yellow stain in the corner that looks like crab with legs on the right side

KUMIP 134799 (Holotype). Wheeler Formation, House Range, Millard County, Utah. Figure 9.1 in Robison & Richards (1981).

Waptia

a green rock with a dark smudge in the middle

KUMIP 314038 (Part, counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 12.3 in Briggs & Lieberman et al. (2008).

a green rock with a dark smudge in the middle

KUMIP 314038 (Part, counterpart). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 12.3 in Briggs & Lieberman et al. (2008).

a gray rock with a smudge of gray that outlines a thick line across the rock

KUMIP 314044 (Tail only). Spence Shale Member of the Langston Formation, Wellsville Mountains, Box Elder County, Utah. Figure 12.1 in Briggs & Lieberman et al. (2008).

Undetermined Bivalved Arthropod

a gray rock with two yellow stains that look like two leaves on top of each other
KUMIP 134188. Wheeler Formation, House Range, Millard County, Utah. Figure 9.3 in Robison & Richards (1981).