tetraspaaniinids

Tetraspaaniinids are a group of extinct marine invertebrates belonging to the phylum Echinodermata. They are known from fossilized remains, primarily their ossicles, which are small calcareous plates that formed their body skeleton. Tetraspaaniinids lived during the Devonian period, approximately 419 to 359 million years ago. They are characterized by a body plan that suggests a sessile or semi-sessile lifestyle, likely attached to the seafloor.

The most distinctive feature of tetraspaaniinids is the presence of ossicles with a tetraradial symmetry, meaning they exhibit symmetry in four directions. This arrangement is reflected in the name "tetraspaaniinid," which translates to "four-spanned." The exact biological affinities and evolutionary relationships of tetraspaaniinids within the Echinodermata are still a subject of scientific investigation. Their peculiar morphology and limited fossil record make them an intriguing group for paleontologists studying the early evolution of echinoderms.

Fossils of tetraspaaniinids have been found in various locations globally, indicating a widespread distribution during the Devonian. Their ecological role in ancient marine environments is not well understood, but it is presumed they occupied benthic niches. The study of tetraspaaniinids contributes to our understanding of the diversity and adaptive radiation of early echinoderms.