Heliophora sp. Echinoid
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Quick Facts
What is a Sand Dollar?
Sand dollars are not shells but are the skeletons, or "tests," of a type of flat, burrowing sea urchin. They are marine animals belonging to the class Echinoidea, making them close relatives of regular sea urchins and heart urchins. Their flattened, discoidal shape is an adaptation for living on or just beneath the surface of sandy seabeds.
Anatomy & Characteristics
Fossil sand dollars like Heliophora are excellent paleoenvironmental indicators. Their presence in the fossil record tells paleontologists that the ancient environment was a shallow, high-energy marine setting with a sandy substrate, such as a near-shore or sandbar environment.
The coastal region of Boujdour of Morocco was a shallow sea during the Miocene and Pliocene epochs. The conditions were perfect for large populations of sand dollars to thrive on the sandy seafloor. After death, they were quickly buried by sand, which later lithified into sandstone. Many of these fossils are preserved as durable internal molds (also called steinkerns), where sediment filled the inside of the test before the original calcite skeleton dissolved away, leaving a perfect cast of its interior.
- Scientific Name: Heliophora sp.
- Common Name: Keyhole Sand Dollar
- Geological Period: Miocene-Pliocene Epochs
- Age: Miocene or Pliocene
- Location Found: Boujdour Province, Western Sahara region, Morocco
- Fossil Type: Typically preserved as an internal mold (steinkern) in sandstone.
What is a Sand Dollar?
Sand dollars are not shells but are the skeletons, or "tests," of a type of flat, burrowing sea urchin. They are marine animals belonging to the class Echinoidea, making them close relatives of regular sea urchins and heart urchins. Their flattened, discoidal shape is an adaptation for living on or just beneath the surface of sandy seabeds.
Anatomy & Characteristics
- Shape: A distinct, flattened, circular body (test) made of fused calcite plates.
- Lunules: The most prominent feature of the Heliophora genus are the elongated slots or "keyholes" that pass completely through the test. These holes, called lunules, are a hydrodynamic adaptation that helps the animal burrow more efficiently and stay stable in strong sea currents.
- Petaloid Pattern: The top surface features a distinct five-petaled pattern (the petaloid), which housed the specialized tube feet used for respiration.
- Symmetry: Like all echinoids, they have a five-fold radial symmetry.
Fossil sand dollars like Heliophora are excellent paleoenvironmental indicators. Their presence in the fossil record tells paleontologists that the ancient environment was a shallow, high-energy marine setting with a sandy substrate, such as a near-shore or sandbar environment.
The coastal region of Boujdour of Morocco was a shallow sea during the Miocene and Pliocene epochs. The conditions were perfect for large populations of sand dollars to thrive on the sandy seafloor. After death, they were quickly buried by sand, which later lithified into sandstone. Many of these fossils are preserved as durable internal molds (also called steinkerns), where sediment filled the inside of the test before the original calcite skeleton dissolved away, leaving a perfect cast of its interior.
