Description

Peytoia is a genus of hurdiid radiodont, an early-order of stem-group arthropods that thrived during the Cambrian period. It consists of two species: Peytoia nathorsti from the Miaolingian period in Canada and Peytoia infercambriensis from Poland, dating back to Cambrian Stage 3. These creatures had distinctive characteristics. Their two frontal appendages featured long bristle-like spines, lacked a fan tail, and had short-stalked eyes positioned behind their large head.

A total of 108 Peytoia specimens have been discovered in the Greater Phyllopod bed, making up approximately 0.21% of the community. Peytoia nathorsti was about 30 centimeters (12 inches) in body length. The oral cone of Peytoia nathorsti had four large plates, similar to Hurdia, whereas Anomalocaris had only three. Notably, Peytoia's oral cone lacked inner rows of spines, which differentiated it from Hurdia.

The frontal appendages of Peytoia had 13 podomeres in their distal part, a typical and likely ancestral feature of radiodonts. These appendages also displayed five blade-like endites with short auxiliary spines. An intercalary podomere separated the proximal and distal ends of the appendage, and the appendages had large medial spines, sometimes referred to as "gnathites," facing towards the opposite appendage. The trunk of Peytoia comprised 13 segments with wide swimming flaps. Compared to Hurdia, Peytoia had less prominent setal blades.

Early mistakes on discovery and indentification

The history of Peytoia is interconnected with that of "Laggania" and Anomalocaris. Initially, all three were identified as isolated body parts and only later recognized as parts of the same animal. This was due to the mixture of mineralized and unmineralized body parts, with the oral cone and frontal appendage being more easily fossilized than the delicate body.

The first discovery was a detached frontal appendage of Anomalocaris, initially described as a phyllocarid crustacean by Joseph Frederick Whiteaves in 1892 due to its resemblance to the abdomen of that taxon. Charles Doolittle Walcott later discovered the first fossilized oral cone, which he mistakenly identified as a jellyfish and placed in the genus Peytoia. In the same publication, Walcott described a poorly-preserved body specimen as Laggania, interpreting it as a holothurian (sea cucumber). In 1978, Simon Conway Morris noted that the mouthparts of Laggania were identical to Peytoia's, suggesting that Laggania was a composite fossil of Peytoia and the sponge Corralio undulata.