Odontoanserae

The Odontoanserae is a proposed clade that includes the family Pelagornithidae (pseudo-toothed birds) and the clade Anserimorphae (the order Anseriformes and their stem-relatives).[2] The placement of the pseudo-toothed birds in the evolutionary tree of birds has been problematic, with some supporting the placement of them near the orders Procellariformes and Pelecaniformes based on features in the sternum.[3]

Odontoanserae Temporal range: Late Cretaceous-Holocene, 71–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
The skull of Pelagornis mauretanicus (top) and the head of common merganser (bottom) showing the serrated edge common in this group
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Superorder:	Galloanserae
Clade:	Odontoanserae Bourdon, 2005
Subgroups
†Odontopterygiformes Anserimorphae Sibley & Ahlquist, 1988 †Gastornithiformes †Vegaviiformes Anseriformes sensu lato[1] †Conflicto †Anatalavis †Presbyornithidae Anseriformes sensu stricto

In 2005 a cladistic analysis had found support in placing pseudo-toothed birds as the sister group to waterfowl.[2] Evidence for this comes from shared characteristics in the skull such as lack of a crest on the underside of the palatine bone and two condyles on the mandibular process of the quadrate bone, with the middle condyle beakwards of the side condyle.[2] In addition to that, both groups have similar features in their pelvic and pectoral regions. Furthermore, a 2013 study on the growth pattern and structure of the pseudoteeth in Pelagornis mauretanicus shows more support of Odontoanserae as both groups have "soft rhamphotheca, or delayed hardening of the rhamphotheca."[4] In addition to Pelagornithidae and Anseriformes paleontologists also have support in placing mihirungs (Dromornithidae) and Gastornithids into this group, as they too also share anatomical features in the skull and pelvic bones with waterfowl.[5][6][7] The mihirungs and the gastornithids are more derived than the pseudo-tooth birds and are closer to Anseriformes. One hypothesis is that diatrymas and mihirungs are successive sister groups to anseriforms and another hypothesis places mihirungs as crown anseriforms closely related to the screamers (Anhimidae).[6]

Below is the general consensus of the phylogeny.[6][2][7][8][9]

Odontoanserae	†Pelagornithidae (pseudo-tooth birds)   Anserimorphae   †Gastornithidae       †Dromornithidae (mihirungs)       †Vegaviidae     Anseriformes (screamers and waterfowl)

However, a 2017 paper by Worthy and colleagues found an alternative phylogeny concerning Anserimorphae.[10] By adding additional new characters, as well as incorporating several new taxa into established matrices, the authors have found gastornithids and mihirungs to be sister taxa which could be placed in the order Gastornithiformes.[10] In addition, they have found support that the family Vegaviidae (usually classified as crown anseriforms or their sister taxon[9]) are more related to gastornithiforms than to anseriforms; accordingly, they have created the monotypic order Vegaviiformes.[10] The authors did note the bootstrap support is weakly supported and several alternative phylogenies in their paper found gastornithiforms to be stem galliforms instead.[10] These too were weakly supported as well.[10] Below is a simplified phylogeny showing their one phylogeny supporting gastornithiforms as anserimorphs.[10]

Anserimorphae	Anseriformes (screamers and waterfowl)       †Vegaviiformes   †Gastornithiformes   †Gastornithidae     †Dromornithidae (mihirungs)

In 2019 a new species Conflicto antarcticus was described from Early Paleocene deposits in Antarctica.[1] Known completely from associated bones from a single individual, Tambussi et al. (2019) incorporated the new taxon into a phylogenetic analysis using the matrix data from Worthy et al. (2017). Their results not only supported the sister grouping of vegaviids with gastornithids and mihirungs (which included Vegaviidae into Gastornithiformes), but also found two taxa, Anatalavis rex and the tall, wading presbyornithids, traditionally placed as part of the anseriform crown,[11] to be stem-anseriforms.[1] Below is the Tambussi et al. (2019) phylogeny.[1]

Anserimorphae	†Gastornithiformes   †Vegaviidae       †Gastornithidae     †Dromornithidae (mihirungs)       Anseriformes sensu lato     †Conflicto antarcticus     †Anatalavis rex         †Presbyornithidae     Anseriformes (screamers and waterfowl)

References

1. Claudia P. Tambussi; Federico J. Degrange; Ricardo S. De Mendoza; Emilia Sferco; Sergrio Santillana (2019). "A stem anseriform from the early Palaeocene of Antarctica provides new key evidence in the early evolution of waterfowl". Zoological Journal of the Linnean Society. 186 (3): 673–700. doi:10.1093/zoolinnean/zly085.
2. Bourdon, E. (2005). "Osteological evidence for sister group relationship between pseudo-toothed birds (Aves: Odontopterygiformes) and waterfowls (Anseriformes)". Naturwissenschaften. 92 (12): 586–91. doi:10.1007/s00114-005-0047-0. PMID 16240103.
3. Mayr, G.; Hazevoet, C.J.; Dantas, P.; Cachão, M. (2008). "A Sternum of a Very Large Bony-Toothed Bird (Pelagornithidae) from the Miocene of Portugal". Journal of Vertebrate Paleontology. 28 (3): 762–769. doi:10.1671/0272-4634(2008)28[762:asoavl]2.0.co;2.
4. Louchart, A.; Sire, J.-Y.; Mourer-Chauviré, C.; Geraads, D.; Viriot, L.; de Buffrénil, V. (2013). "Structure and Growth Pattern of Pseudoteeth in Pelagornis mauretanicus (Aves, Odontopterygiformes, Pelagornithidae)". PLoS ONE. 8 (11): e80372. doi:10.1371/journal.pone.0080372. PMC 3828250. PMID 24244680.
5. Andors, A. (1992). "Reappraisal of the Eocene groundbird Diatryma (Aves: Anserimorphae)". Science Series Natural History Museum of Los Angeles County. 36: 109–125.
6. Murrary, P.F; Vickers-Rich, P. (2004). Magnificent Mihirungs: The Colossal Flightless Birds of the Australian Dreamtime. Indiana University Press.
7. Agnolín, F. (2007). "Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno Medio de Patagonia, Argentina". Revista del Museo Argentino de Ciencias Naturales. 9: 15–25. doi:10.22179/revmacn.9.361.
8. Livezey, B.C.; Zusi, R.L. (2007). "Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion". The Science of Nature. 149 (1): 1–95. doi:10.1111/j.1096-3642.2006.00293.x. PMC 2517308. PMID 18784798.
9. Agnolín, F.L.; Egli, F.B.; Chatterjee, S.; Marsà, J.A.G (2017). "Vegaviidae, a new clade of southern diving birds that survived the K/T boundary". The Science of Nature. 104 (87): 87. doi:10.1007/s00114-017-1508-y. PMID 28988276.
10. Worthy, T.H.; Degrange, F.J.; Handley, W.D.; Lee, M.S.Y. (2017). "The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres)". Royal Society Open Science. 11 (10): 170975. doi:10.1098/rsos.170975. PMC 5666277. PMID 29134094.
11. Vanesa L. De Pietri; R. Paul Scofield; Nikita Zelenkov; Walter E. Boles; Trevor H. Worthy (2016). "The unexpected survival of an ancient lineage of anseriform birds into the Neogene of Australia: the youngest record of Presbyornithidae". Royal Society Open Science. 3 (2): 150635. doi:10.1098/rsos.150635. PMC 4785986. PMID 26998335.