Exoacantha

Exoacantha is a genus of extinct echinoids, commonly known as sea urchins, that lived during the Cretaceous period. The name Exoacantha, derived from Greek, refers to the prominent and often long spines that characterized these animals. Fossil evidence of Exoacantha has been found in various parts of the world, indicating a wide distribution during its existence. These marine invertebrates were benthic, meaning they lived on the seafloor, and likely played a role in the Cretaceous ecosystem as detritivores or grazers.

The genus Exoacantha is distinguished by specific morphological features of its test, the hard, calcareous shell that encloses the internal organs of the sea urchin. These features typically include the arrangement and morphology of the ambulacral and interambulacral plates, as well as the tubercles where the spines were attached. The spines themselves are a notable aspect of Exoacantha, often being hollow and robust, suggesting a defensive purpose or a role in locomotion or anchoring. Paleontologists study the fossil remains of Exoacantha to understand the evolution of echinoids, the paleoenvironments of the Cretaceous, and the broader patterns of marine life during that era. The classification and specific species within Exoacantha have been subject to revision as new fossil discoveries are made and analyzed.