Guildayichthyidae

Guildayichthyidae Temporal range: Late Mississippian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Fossil of Discoserra pectinodon
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	† Guildayichthyiformes Lund, 2000
Family:	† Guildayichthyidae Lund, 2000
Genera
See text

Guildayichthyidae is a prehistoric family of marine fish from the Mississippian Bear Gulch Limestone of Montana. ^{[1] [2]} It is the only family in the order Guildayichthyiformes. Guildayichthyids possess an uncommon mixture of primitive and modern characteristics in their skull bones. ^[3]

Their taxonomy has long been debated, with studies placing them within the Neopterygii, while others placed them within the Cladistia. A 2025 study found them to most likely be the sister group to the extinct Bobasatraniiformes, with the two forming an early-diverging clade within the crown group Actinopterygii. ^[4]

Taxonomy

This family consists of the following genera and species: ^[1]

• Genus Guildayichthys Lund, 2000
  • Species Guildayichthys carnegiei Lund, 2000
• Genus Discoserra Lund, 2000
  • Species Discoserra pectinodon Lund, 2000

References

1. Lund, Richard (2000). "The new Actinopterygian order Guildayichthyiformes from the Lower Carboniferous of Montana (USA)" (PDF). Geodiversitas. 22 (2): 171–206.
2. Albert, James S.; Johnson, Derek M. (23 November 2011). "Diversity and Evolution of Body Size in Fishes". Evolutionary Biology. 39 (3): 324–340. doi:10.1007/s11692-011-9149-0. S2CID   255346377.
3. "Exquisitely-Preserved Guildayichthys Mississippian Bear Gulch Fish". FossilMall.
4. Stack, Jack. "An ontological morphological phylogenetic framework for living and extinct ray-finned fishes (Actinopterygii)". The Anatomical Record. n/a (n/a). doi:10.1002/ar.70090. ISSN   1932-8494.