Biology:Unenlagiidae

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Unenlagiidae is a proposed family of eumaniraptoran paravians that includes the subfamilies Unenlagiinae and possibly Halszkaraptorinae. Fossils of both subfamilies have been found in both Gondwanan and Laurasian deposits. The biology of the group suggests that some members were semiaquatic specialists.[1]

Classification

The family Unenlagiidae traditionally includes the same members as the previously named subfamily of Dromaeosauridae, Unenlagiinae, so Unenlagiidae was often seen as a synonym of Dromaeosauridae. However, since the 2010s, there have been subsequent studies that have questioned this placement, necessitating the revival of the family name. Some have placed unenlagiids as outside Dromaeosauridae, being the sister taxon or closely related to Avialae,[2][3] while others have placed the newly recognized halszkaraptorines in the family, as basal deinonychosaurs outside Dromaeosauridae and Troodontidae.[4] Other recent studies supported the traditional placement of Halszkaraptorinae and Unenlagiinae in Dromaeosauridae, forming no distinct clade.[1][5] In 2021, Brum et al. named the clade Unenlagiinia for a unified Unenlagia+Halszkaraptor clade, recovering them as basal dromaeosaurs.[6]

The following cladogram is from Motta et al., 2020, showing Unenlagiidae outside dromaeosaurids and more closely related to Avialae:[3]

Paraves
 

Troodontidae

 
Eumaniraptora
 

Dromaeosauridae

 
 
 

Microraptoria

 
 
Unenlagiidae
 

Austroraptor

 
 

Buitreraptor

 
 

Unenlagia

 
 
 
 
 

Overoraptor

 
 

Rahonavis

 
 
Avialae
Archaeopterygidae
 

Alcmonavis

 
 
 

Wellnhoferia

 
 

Archaeopteryx

 
 
 
 
Anchiornithidae
 

Xiaotingia

 
 

Anchiornis

 
 
 
 

Jeholornis

 
 

Pygostylia

 
 
 
 
 
 
 
 
 

In 2025, Motta et al. recovered Unenlagiidae (along with Halszkaraptoridae, Anchiornithidae, and Archaeopteryx) as within Avialae.[7] The two trees recovered are reproduced below:

Consensus Improved (equal weighting)
Pennaraptora
 
 

Scansoriopterygidae

 
 

Oviraptorosauria

 
 
Paraves
 

Troodontidae

 
Eumaniraptora
Dromaeosauridae
 

Microraptoria

 
 

Eudromaeosauridae

 
 
Avialae
Unenlagiinia
 

Halszkaraptoridae

 
 

Unenlagiidae

 
 
 
 
 

Anchiornithidae

 
 

Archaeopteryx

 
 
 
 

Jeholornis

 
 

Pygostylia

 
 
 
 
 
 
 
Consensus Improved (implied weighting)
Pennaraptora
 
 

Scansoriopterygidae

 
 

Oviraptorosauria

 
 
Paraves
 

Troodontidae

 
Eumaniraptora
Dromaeosauridae
 

Microraptoria

 
 

Eudromaeosauridae

 
 
Avialae
Unenlagiinia
 

Halszkaraptoridae

 
 

Unenlagiidae

 
 
 
 

Anchiornithidae

 
 
 
 

Fujianvenator

 
 

Archaeopteryx

 
 
 
 

Jeholornis

 
 

Pygostylia

 
 
 
 
 
 
 
 

References

  1. ↑ 1.0 1.1 Cau, A.; Beyrand, V.; Voeten, D.; Fernandez, V.; Tafforeau, P.; Stein, K.; Barsbold, R.; Tsogtbaatar, K. et al. (6 December 2017). "Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs". Nature 552 (7685): 395–399. doi:10.1038/nature24679. PMID 29211712. Bibcode: 2017Natur.552..395C. 
  2. ↑ Federico L. Agnolín and Fernando E. Novas (2013). Avian ancestors. A review of the phylogenetic relationships of the theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae. SpringerBriefs in Earth System Sciences. pp. 1–96. doi:10.1007/978-94-007-5637-3. ISBN 978-94-007-5636-6. 
  3. ↑ 3.0 3.1 Matías J. Motta; Federico L. Agnolín; Federico Brissón Egli; Fernando E. Novas (2020). "New theropod dinosaur from the Upper Cretaceous of Patagonia sheds light on the paravian radiation in Gondwana". The Science of Nature 107 (3). doi:10.1007/s00114-020-01682-1. PMID 32468191. Bibcode: 2020SciNa.107...24M. 
  4. ↑ Hartman, Scott; Mortimer, Mickey; Wahl, William R.; Lomax, Dean R.; Lippincott, Jessica; Lovelace, David M. (2019). "A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight". PeerJ 7. doi:10.7717/peerj.7247. PMID 31333906. 
  5. ↑ Cau, Andrea (2020-02-25). "The body plan of Halszkaraptor escuilliei (Dinosauria, Theropoda) is not a transitional form along the evolution of dromaeosaurid hypercarnivory" (in en). PeerJ 8. doi:10.7717/peerj.8672. ISSN 2167-8359. PMID 32140312. 
  6. ↑ Brum, Arthur S.; Pêgas, Rodrigo V.; Bandeira, Kamila L.N.; Souza, Lucy G.; Campos, Diogenes A.; Kellner, Alexander W.A. (2021). "A new Unenlagiinae (Theropoda: Dromaeosauridae) from the Late Cretaceous of Brazil". Papers in Palaeontology 7 (4): 2075–2099. doi:10.1002/spp2.1375. 
  7. ↑ Motta, Matías J.; Agnolína, Federico L.; Eglia, Federico Brissón; Rozadillaa, Sebastián; Novas, Fernando E. (22 Aug 2025). "Phylogenetic relationships of Unenlagiidae among Paraves (Dinosauria)". Journal of Systematic Palaeontology 23 (1). doi:10.1080/14772019.2025.2529608. https://www.tandfonline.com/doi/full/10.1080/14772019.2025.2529608. Retrieved 22 August 2025. 

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