Tolypelepidida is an extinct

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

of heterostracan

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

s. 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). Janvier, Philippe (1997
Heterostraci
''The Tree of Life Web Project''. A recent study by Lundgren and Blom in 2013 implies that the order is

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, with the type genus, ''Tolypelepis'', being the sister taxon of

Cyathaspidiformes Cyathaspidiformes is an extinct order of heterostracan vertebrates known from extensive fossil remains primarily from Silurian to Early Devonian strata of Europe, and North America, and from Early Devonian marine strata of Siberia. Anatomy Like ...

.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.

References

Heterostraci Prehistoric jawless fish orders Devonian jawless fish Silurian jawless fish Silurian first appearances Pridoli taxonomic orders Early Devonian taxonomic orders Early Devonian extinctions {{Pteraspidomorphi-stub