Psammosteida also called as Psammosteoidei is a suborder of pteraspidid heterostracan agnathans. The psammosteids had broad, flattened bodies, suggesting a predominantly benthic habit. The earliest unequivocal psammosteid is Drepanaspis of Early Devonian Germany. Other notable psammosteids include Psammosteus, and Obruchevia, two genera of enormous species with dorsal shields around one meter in diameter. The Psammosteids were the only heterostracans to survive to the end of the Devonian, where they finally perish during the Hangenberg event.
Classification Internal relationships Taxonomy The following families and genera were recognised by Glinskiy (2017) in the suborder Psammosteoidei:
Suborder Psammosteoidei (sensu Psammosteida Kiaer, 1932 emend. Tarlo, 1962)
Family Drepanaspididae Traquair, 1899 Genus Drepanaspis Schlüter, 1887
Family Guerichosteidae Tarlo, 1964 Genus Guerichosteus Tarlo, 1964 (= ?Hariosteus Tarlo, 1964)
Family Obrucheviidae Tarlo, 1964 Genus Obruchevia Whitley 1940 Genus Perscheia Elliott, Mark-Kurik & Daeschler, 2004
Family Русnоstеidае Tarlo, 1962 Genus Ganosteus Rohon, 1901 Genus Pycnolepis Tarlo, 1964 Genus Pycnosteus Preobrazhensky, 1911
Family Psammolepididae Tarlo, 1962 Genus Psammolepis Agassiz, 1845
Family Psammosteidae Traquair, 1896 Subfamily Placosteinae Glinskiy, 2017 Genus Placosteus Agassiz, 1845 Subfamily Psammosteinae Traquair, 1896 Genus Elgaia Glinskiy, 2017 Genus Psammosteus Agassiz, 1844 Genus Karelosteus Obruchev, 1933 Genus Traquairosteus Tarlo, 1964 Subfamily incertae sedis Genus Vladimirolepis Glinskiy, 2017
Family incertae sedis Genus Schizosteus Obruchev, 1940 Genus Tartuosteus Obruchev, 1961
Phylogeny An analysis by Glinskiy in 2017 obtained the following phylogenetic tree by strict consensus:
External relationships A 2025 comprehensive analysis on pteraspidomorph relationships by Randle et al. retained the placement of Psammosteoidei within Pteraspidiformes, with Anchipteraspididae as the deepest branching Pteraspidiformes.
References