Siberiidae

Siberiids often reach large sizes, achieving as much as 22 cm, In the case of Megadictyon the appendages terminate with sclerotized spines. The bottom of the head exposes an oral opening surrounded by an array of layers of plates and teeth which has been compared to the oral cones of radiodonts; the pharynx houses numerous pharyngeal teeth, and has been compared to that of priapulids. No eyes have been observed. == Ecology ==

The respiratory papillae likely supported an active predatory lifestyle, similar to opabiniids, and radiodonts which too bear specialized respiratory structures, and raptorial appendages. This lifestyle is also supported by the gut diverticulae allowing for more efficient digestion and metabolism present in Jianshanopodia and Megadictyon. Siberiids have been found in the Chengjiang Biota and the Sinsk Biota. == Phylogeny ==

In the past siberiids have been considered a transitional group between 'Xenusia' and Radiodonta, which too bears differentiated raptorial frontal appendages. }} }}}}}}}}}}}}}}}}}}}}}}}}}} }}}} }} }} }} }}}}}}}}}}}}}}}}|style=font-size:90%}} == See also ==