Clarke et al. 2005 brought us
Vegavis iaai (MLP 93-I-3-1, MACN-PV 19.748; Late Cretaceous. 68 mya; Figs. 1, 2), a disarticulated partial fossil from Antarctica, which they considered a duck relative and the first definite member of the Euornithes (extant birds and kin) that lived before the K-T boundary.
It appears that mistakes were made
by Clarke et al. which affected their matrix scores. If I made mistakes, I’d be happy to change them when better data comes along.
From the Clarke et al. abstract:
“Long-standing controversy surrounds the question of whether living bird lineages emerged after non-avian dinosaur extinction at the Cretaceous/Tertiary (K/T) boundary or whether these lineages coexisted with other dinosaurs and passed through this mass extinction event.”
“Here we identify a rare, partial skeleton from the Maastrichtian of Antarctica as the first Cretaceous fossil definitively placed within the extant bird radiation. Several phylogenetic analyses supported by independent histological data indicate that a new species, Vegavis iaai, is a part of Anseriformes (waterfowl) and is most closely related to Anatidae, which includes true ducks. A minimum of five divergences within Aves before the K/T bound- ary are inferred from the placement of Vegavis; at least duck, chicken and ratite bird relatives were coextant with non-avian dinosaurs.”
Only a tiny reconstruction
(Fig. 2.5) was provided by Clarke et al., so a larger one is provided here (Fig. 2) and it seems to be more crane- or ratite-like than duck-like, although the Eocene duck, Presbyornis (Fig. 3) does have a stork-like morphology.
Clarke et al. conclude:
“Vegavis has different proportions from Presbyornis that are closer to other extant basal anseriform species [geese, screamers). Thus, there is further support that the wader proportions and the ecology used to diagnose Presbyorntihidae are derived for that particular anseriform lineage and not ancestral avian characteristics.” Not sure why they arrived at this conclusion because Vegavis appears to have long-legged, stork- and ratite-like proportions (Fig. 2). This is a gracile bird.
Clarke et al. nest Vegavis
the LRT nests ducks higher on the tree (Fig. 5), closer to long-legged predatory birds. Here Vegavis nests with other pre-Ornithurae Cretaceous birds, like Archaeornithura (Fig. 4), most of which have teeth, unfused metatarsals and gastralia. I found gastralia on the published photo of Vegavis. Unfused metatarsals were originally illustrated. The purported fused sacrum (yellow in figs 1, 2) is the same shape as a distal humerus. It appears to be a split humerus, internal view (Fig. 6). The other split ‘humerus’ appears to be a tibia still articulating with the distal femur. Unfused sacral vertebrae are identified above. Pedal digit 5 is not absent. No scattered cervicals are longer than tall. The ischium is shorter than the pubis, which has a small pubic foot.
all birds with shorter limbs evolved them by neotony. Ratite, flamingo and stork juveniles have shorter legs.
I’m interested only
in getting things right. If you can provide better resolution images that support the original identifications, I will make changes to the data presented here. At present Vegavis is the result of a gradual accumulation of traits. It is transitional from birds with unfused sacrals and metatarsals to those with fused sacrals and metatarsals and no pedal digit 5 among several other traits.
If you want to see what a related bird sacrum should look like
click here for several samples.
Clarke, JA, Tambussi CP, Noriega JI, Erickson GM and Ketcham RA 2005. Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature 433, 305–308.