Inoceramus shells

Inoceramids make good index fossils because of their variability and large number of short-lived species.

NPS photo.

Marine Fossil
Scientific Name: Inoceramus (genus)

Inoceramids are bivalves related to living clams and mussels and are one of the most common marine fossils of the Late Cretaceous. Large, diverse groups of Inoceramids lived in shallow waters and were epifaunal, covering the muddy seafloor like a carpet. This family of bivalve diversified rapidly during the Cenomanian and Turonian ages, branching out to more than 70 species over the course of just about 11 million years. Species ranged from a few centimeters to two meters (1-6.5 feet) in length. Their success continued for another 34 million years until the end of the Cretaceous period when they went extinct along with several other taxa.

Fossil bivalves preserved in a sandstone matrix.

NPS photo.

Paleontologist will look at details from a whole bed of fossils to determine taphonomy, or the processes of fossilization. The condition and position of shells provides clues to the mechanism of burial, transport, decay, etc.. Studying this fossil record can help to determine the conditions of the paleoenvironment that supported these bivalves on the seafloor.

3D Inoceramus shells—Inoceramids
Chaco Culture National Historical Park, New Mexico

_{Inoceramus shells on sandstone slab by National Park Service Geologic Resources Division on Sketchfab}

Alternative Text for the 3D Model

A 3D model. This model shows fossil clam shells on a block of rock. The model can be rotated and tilted using a computer interface.

Inoceramids are bivalves related to living clams and mussels and are one of the most common marine fossils of the Late Cretaceous.

To learn more, visit - https://www.nps.gov/articles/series.htm?id=7B32EA8A-A130-11C3-E755871E8385F30E

Footnotes linked to the 3D model:

1. Scale marker.
2. Scale marker.
3. Put a ring on it! The distinctive ridges are growth rings. Inoceramids, like ammonites, make good index fossils because of their variability and large number of short-lived species. Identifying physical features, like the shape of the valves and rings on the outer shell, help distinguish the different species.
4. Clam scramble—Paleontologists can learn a lot about the environment these mussels lived based on their position in the rocks (once a sandy sea floor). In a high-energy environment, such as the wave-battered shoreline, fossils may break and jumble together before burial. Here, mostly intact shells suggest near shore environment with well-sorted sand, near the surf of the beach.

Footnotes

1. Scale marker.
2. Scale marker.
3. Put a ring on it! The distinctive ridges are growth rings. Inoceramids, like ammonites, make good index fossils because of their variability and large number of short-lived species. Identifying physical features, like the shape of the valves and rings on the outer shell, help distinguish the different species.
4. Clam scramble—Paleontologists can learn a lot about the environment these mussels lived based on their position in the rocks (once a sandy sea floor). In a high-energy environment, such as the wave-battered shoreline, fossils may break and jumble together before burial. Here, mostly intact shells suggest near shore environment with well-sorted sand, near the surf of the beach.

Related Links

• NPS—Chaco Culture National Historical Park
• NPS—National Fossil Day
• NPS—Photogrammetry
• NPS—Fossils and Paleontology
• NPS—Geology