Tolypelepidida

 ( Heterostraci ) 

Tolypelepidida is an extinct order of heterostraci . These armored jawless fish superficially resemble their relatives, the cyathaspids, though, researchers place the tolypelepids as a sister group to the cyathaspids and the pteraspidids (and both groups' daughter taxa).Philippe Janvier (1997) Heterostraci The Tree of Life Web Project. A recent study by Lundgren and Blom in 2013 implies that the order is paraphyly, with the type genus, Tolypelepis, being the sister taxon of Cyathaspidiformes.Lundgren, Mette, and Henning Blom. "Phylogenetic relationships of the cyathaspidids (Heterostraci)." GFF 135.1 (2013): 74-84. The typical tolypelepid had a carapace formed from dorsal and ventral plates, and a scaly tail.