Teleosteomorpha is an infraclass of ray-finned fishes containing all teleost fish and their closest extinct relatives. Also in this group are two diverse Mesozoic fish orders, the Aspidorhynchiformes and the Pachycormiformes. Several other non-teleostomorph teleosteans existed throughout the Mesozoic, although not as dominant as the two main clades in the group.

Shared morphological features of this group include a autosphenotic bone lacking a dermal component, the lack of a canal bearing part of the antorbital bone, the lack of vertebral centra fused into the occipital condyle in adult individuals, and each hypural (caudal fin support) being articulated with caudal rays.

The oldest known teleosteomorph is Prohalecites from the Triassic of Italy. The last surviving non-teleostean teleosteomorph was Belonostomus, which survived into the Late Paleocene.

Taxonomy

Cladogram of Teleosteomorpha after Sferco et al. 2015:

Holostei
TeleosteomorphaPachycormiformes Aspidorhynchiformes Mesturus Pholidophoridae Siemensichythys Dorsetichthys Eurycormus Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Pachycormiformes
Aspidorhynchiformes Mesturus Pholidophoridae Siemensichythys Dorsetichthys Eurycormus Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Aspidorhynchiformes
Mesturus
Pholidophoridae Siemensichythys Dorsetichthys Eurycormus Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Pholidophoridae
Siemensichythys Dorsetichthys Eurycormus Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Siemensichythys
Dorsetichthys Eurycormus Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Dorsetichthys
Eurycormus Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Eurycormus
Leptolepidae Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Leptolepidae
Luisiellidae Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Luisiellidae
Tharsis dubius Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Tharsis dubius
Varasichthyidae Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Varasichthyidae
Ascalabos Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Ascalabos
Ichthyodectiformes Teleostei crown group (including Crossognathiformes)
Ichthyodectiformes
Teleostei crown group (including Crossognathiformes)
(Teleostei total group)

The cladogram below is simplified after a phylogenetic analysis by Bean (2021).

TeleosteomorphaPachycormidae Aspidorhynchidae Teleostei Archaeomaenidae Pholidophoridae Prohalecites Eurycormus Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Pachycormidae
Aspidorhynchidae Teleostei Archaeomaenidae Pholidophoridae Prohalecites Eurycormus Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Aspidorhynchidae
TeleosteiArchaeomaenidae Pholidophoridae Prohalecites Eurycormus Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Archaeomaenidae
Pholidophoridae Prohalecites Eurycormus Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Pholidophoridae
Prohalecites Eurycormus Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Prohalecites
Eurycormus Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Eurycormus
Ankylophoridae Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Ankylophoridae
Ichthyokentema Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Ichthyokentema
Dorsetichthys Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Dorsetichthys
Leptolepis Ascalaboidae Varasichthyidae Crown group Teleostei
Leptolepis
Ascalaboidae Varasichthyidae Crown group Teleostei
Ascalaboidae
Varasichthyidae Crown group Teleostei
Varasichthyidae
Crown group Teleostei
Teleosteomorpha contains both the smallest (Paedocypris progenetica, above) and the largest (Leedsichthys problematicus, below) known ray-finned fish to have ever existed.

Where applicable, taxonomic order is based on Eschmeyer's Catalog of Fishes: