Tetraspaannids

Tetraspaannids are a proposed but hypothetical group of extinct terrestrial arthropods. The name suggests they would have possessed four pairs of limbs, similar to other arachnids. Paleontological evidence for tetraspaannids is currently considered insufficient by most scientists, and the concept remains largely speculative. The idea of tetraspaannids arose from interpretations of certain problematic microfossils, primarily from the Ediacaran and Cambrian periods. These fossils are ambiguous and have been attributed to a variety of other groups, including early crustaceans, myriapods, or even non-arthropod metazoans. Researchers who have advocated for the existence of tetraspaannids often point to specific fossil specimens, such as those found in the Emu Bay Shale of Australia, as potential examples. However, the limited detail and preservation of these fossils make definitive classification challenging. The scientific consensus is that more robust fossil evidence is needed to confirm the existence of tetraspaannids as a distinct evolutionary lineage. Until such evidence emerges, tetraspaannids remain a topic of debate and conjecture within the field of paleoarthropod evolution.