40MM Detailed Fossil Tetragramma Marticense Sea Urchin Echinoid Cretaceous

Location: Morocco 

Weight: 1.3 Ounces

Dimensions: 40MM

Late Cretaceous 95 -89 Million Years Old

The item pictured is the one you will receive.

Tetragramma marticense Sea Urchin is an extinct species of echinoid, a group of marine invertebrates more commonly known as sea urchins. Echinoids belong to the phylum Echinodermata, which also includes starfish, brittle stars, and sea cucumbers. They are among the most enduring and successful marine organisms, with a fossil record stretching back approximately 450 million years to the Late Ordovician Period.

These animals have thrived in nearly every marine environment on Earth—from the icy waters of the poles to tropical coral reefs, and from the intertidal zones to ocean depths exceeding 5,000 meters. Today, around 800 living species of sea urchins can be found across the globe, continuing a lineage that has survived multiple mass extinction events and vast geological changes.

Tetragramma marticense belongs to an extinct lineage of echinoids commonly known as “Sea Biscuits.” The nickname arises from their rounded, flattened shell, or test, which resembles the shape of a baked biscuit. The scientific term echinoid is derived from the Greek word for “spiny” or “hedgehog,” while the Latin word echinus translates to “pickle,” a name that humorously reflects their texture and appearance.

When alive, these sea urchins were covered with movable spines that served two main functions: protection from predators and mobility across the seabed. The spines, in coordination with tube feet that extended through small pores in the test, allowed the urchin to crawl, burrow into sediment, or even right itself if overturned. These spines also acted as a defensive mechanism, deterring fish and other marine animals from preying upon them.

Fossilized specimens of Tetragramma marticense display intricate details of the test structure, including the ambulacral and interambulacral plates, which form a distinctive five-fold symmetry characteristic of echinoderms. The pattern and texture of these plates often help paleontologists identify individual species and understand evolutionary relationships within the echinoid lineage.

Sea biscuits like Tetragramma marticense typically inhabited warm, shallow marine environments where they fed on detritus, algae, and organic matter found within the sand and sediment. Their feeding apparatus, known as Aristotle’s lantern, consisted of a complex arrangement of calcareous plates and muscles that worked together to scrape and chew food particles—a remarkable adaptation still found in modern sea urchins.

The abundant fossil record of Tetragramma marticense and other echinoids provides critical insights into ancient marine ecosystems and the environmental conditions of prehistoric oceans. Because of their sensitivity to changes in water chemistry and sedimentation, echinoids are valuable indicators of paleoenvironmental conditions, helping scientists reconstruct ancient seafloor habitats and climate patterns.

Tetragramma marticense and its relatives eventually disappeared from the fossil record, but their modern descendants continue to thrive in today’s oceans. Their long evolutionary journey—from the Ordovician seas to the present day—stands as a testament to the resilience and adaptability of echinoderms, one of the ocean’s most remarkable and enduring lineages.