Fossil Arthropod Species

There are over one million living arthropod species today. Arthropods are invertebrate animals (having no backbone or spine) with:
  • a hard, external skeleton (known as an exoskeleton)
  • segmented bodies
  • jointed appendages
Freshwater seed shrimp (Ostracoda) are the most common arthropod fossil found in the Fossil Butte Member (FBM).
shrimp with long whiskers next to fish, additional fish tail in corner
Arthropod with D. dentatus FOBU11821 specimen

NPS Photo

Shrimp - Bechleja rostrata

Order Decapoda, Family Palaemonidae
The Bechleja genus appears to have gone extinct sometime during the Eocene. Living members of the Palaemonidae family:
  • live in freshwater and marine waters
  • also known as prawns
  • primarily carnivores
  • include over 900 species
lobster looking fossil with large front claws
Arthropod FOBU11926 specimen

NPS Photo

Crayfish - Procambarus primaevus

Order Decapoda, Family Cambaridae
Living members of the Procambarus genus are:
  • primarily found in warm freshwaters
  • found in North America and Central America
  • include 160 species
flattened spider body with 8 long legs and large body
Lycosidae (wolf spider) FOBU13456 specimen

NPS Photo

Spiders - 3 Unidentified Species

Order Aranae
  • Family Thomisidae (crab spider)
  • Family Salticidae (jumping spider)
  • Family Lycosidae (wolf spider)
Spiders are very uncommon fossil specimens in the FBM. Possible explanations include:
  • spiders' soft bodies are prone to fast decay
  • spiders may have been eaten before they could break water tension and sink to the bottom of Fossil Lake
Three families have been identified from the FBM, but no species have been described. Together, the 3 families contain thousands of modern species. None of these spider species use a web to catch prey.
bug with folded wings and long legs, missing head
Insect FOBU11882 specimen

NPS Photo


Insect fossils in the Fossil Butte Member (FBM) exist only as very thin carbon stains on the rock. Unlike fossil vertebrates (animals with a backbone), their skeletons are not visible beneath the rock. Insect specimens are found when the splitting rock layers split directly on the carbon stain.
FBM insect specimens are primarily flying or aquatic. They include:
  • dragonflies and damselflies
  • crickets
  • stoneflies
  • true bugs
  • beetles
  • wasps
  • bees
  • ants
  • moths
  • butterflies
  • flies
dragonfly with 4 long wings and long skinny body
Tynskyagrion brookae FOBU448 specimen

NPS Photo

Dragonflies & Damselflies

Order Odonata
  • Suborder Zygoptera (damselflies)
  • Suborder Epiprocta (dragonflies)
Living members of the Odonata order are:
  • diurnal (active during the day)
  • predator insects
  • aquatic, exclusively freshwater insects during nymph state (juvenile stage)
The FBM has produced several Odonata specimens not yet placed into families or described as species. Nymph specimens indicate Fossil Lake was a freshwater lake.
light impression of cricket body with long antennae
Orthoptera FOBU11854 specimen

NPS Photo


Order Orthoptera, Family Gryllidae
Only 1 cricket specimen is known from the FBM. It has not yet been descried as species, yet it closely resembles the living family Gryllidae (true crickets).
Living members of the Gryllidae family are:
  • nocturnal
  • omnivorous
  • an important food source for amphibians, reptiles, and other arthropods

Last updated: August 19, 2022

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