Vegavis: Late Cretaceous, but not a member of the Euornithes

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.

Unfortunately
I was not able to confirm this. The large reptile tree (LRT, 1064 tax, subset fig. 5) nests Vegavis as the proximal outgroup to Yanornis and the Ornithurae.

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.

Figure 1. Vegavis in situ from Clarke et al. 2005. Colors added and used to create the reconstruction in figure 2. What they thought was the other humerus is instead a tibia still linked to the femur. What they thought was a long sacrum is instead the inside of the other humerus.

Figure 1. Vegavis in situ from Clarke et al. 2005. Colors added and used to create the reconstruction in figure 2. What they thought was the other humerus is instead a tibia still linked to the femur. What they thought was a long sacrum is instead the inside of the other humerus The original scale bars did not permit a good match between plate and counter plate.

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.”

 

Figure 2. Vegavis had a relatively short scapula and small deltopectoral crest on a long humerus with a shorter antebrachium. The gracile elongated proportions are crane-like. The torso may have been shorter, reducing the gap between the pelvis and scapula. The original sacrum (yellow) is identical to the distal humerus in outline. Note the metatarsal elements are not fused.

Figure 2. Vegavis had a relatively short scapula and small deltopectoral crest on a long humerus with a shorter antebrachium. The gracile elongated proportions are crane-like. The torso may have been shorter, reducing the gap between the pelvis and scapula. The original sacrum (yellow) is identical to the distal humerus in outline. Note the metatarsal elements are not fused. Gray bones are restored.

Figure x. Reconstruction of Vegavis at published size (print 300 dpi reduced to web 72 dpi).

Figure 2.5. Reconstruction of Vegavis at published size (print 300 dpi reduced to web 72 dpi).

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.

Figure 2. Presbyornis (Eocene) and Anas (extant), a basal and modern duck.

Figure 3. Presbyornis (Eocene) and Anas (extant), a basal and modern duck.

Clarke et al. nest Vegavis

and ducks with chickens, like Gallus, among basalmost Neognaths, derived from sisters to paleognath tinamous like Pseudocrypturus.

Figure 3. Reconstruction of the basal ornithuromorph bird, Archaeornithura with skull added. Feathers and ribs omitted. The length of the tail is hard to determine.

Figure 4. Reconstruction of the basal ornithuromorph bird, Archaeornithura with skull added. Feathers and ribs omitted. The length of the tail is hard to determine.

By contrast,
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.

Apparently 
all birds with shorter limbs evolved them by neotony. Ratite, flamingo and stork juveniles have shorter legs.

Figure 5. Subset of the LRT with the addition of Vegavis as a proximal outgroup to Yanornis and the Ornithurae.

Figure 5. Subset of the LRT with the addition of Vegavis as a proximal outgroup to Yanornis and the Ornithurae.

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.

Figure 6. Here's the purported sacrum of Vegavis with color added. This looks more like a crushed bird humerus. Higher resolution would be helpful.

Figure 6. Here’s the purported sacrum of Vegavis with color added. This matches the one good humerus. I don’t see the hallmarks of a typical fused sacrum here Note the longitudinal lines that should be transverse if this was indeed a sacrum. Of the fused sacra I have seen, fusion extends to the ilia, which are not fused to the sacrum here. Is this the dorsal view? Lateral view? Ventral view of the purported sacrum? Other unfused sacrals are identified closer to the pelvis. Higher resolution would have been helpful, but the authors did not provide it for this key identification.

If you want to see what a related bird sacrum should look like
click here for several samples.

References
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.

 

digimorph.org/specimens/Vegavis_iaai/
wiki/Vegavis

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