Avian Evolutionary Lineages

[Talon87]

NPR reports on a recent study published in Science in which researchers analyzed the genomes of 48 different kinds of birds -- pigeons, owls, flamingos, all sorts -- in order to try and figure out how closely related the birds of today are to one another, how many ancestor species survived the extinction event 66 million years ago, etc.

Of particular note:

• avian genomes are one-third the size of mammalian genomes
• parrots are close relatives of falcons
• the study suggests that only four avian dinosaur species survived the Cretaceous-Paleogene extinction event and that they gave rise to 95% of the species of birds we have today

On that last point, I'm somewhat confused. If only four ancestor species survived, and if those four only account for 95% of the birds we have today, where then did the other 5% come from? The implication would appear to be some non-avian species. Does this mean that 5% of birds alive today are incredibly far removed genetically from all other birds? And if so, then which ones are we talking about?

I figured Daisy would enjoy that second bullet point.

[Emp]

Originally Posted by Talon87

On that last point, I'm somewhat confused. If only four ancestor species survived, and if those four only account for 95% of the birds we have today, where then did the other 5% come from? The implication would appear to be some non-avian species. Does this mean that 5% of birds alive today are incredibly far removed genetically from all other birds? And if so, then which ones are we talking about?

This interested me also, so I scoured the comments and found two possible explanations:

• The Neoaves has those four lineages that cover 95% of birds. The other 5% are the chickens, ducks, and ostrich groups below.
• The remaining 5% are for the lineages that we have not yet gotten published sequences for.

[Talon87]

The first answer still doesn't explain why (the article claims that) the scientists claim that only four species survived the extinction event. If the understanding is that fowl and ostriches descended from an avian dinosaur ancestor, and if that avian dinosaur ancestor is different from the four, then we have a problem.

More confusing, the chart he references suggests that all of the neoaves derive from a single common ancestor -- namely, the Neoaves ancestor -- and that, by the time of that ancestor's first split into two daughter groups, we had five "species" or major groups we were working with: the Neoaves, the Galliformes, the Anseriformes, the Tinamiformes, and the Struthiorniformes. If these five groups existed before the K-Pg extinction event, then we have both a problem with the number four as well as a problem with that commenter's interpretation that the fowl & ostriches are the missing 5%. On the other hand, if the extinction event occurs at the very left border of the chart, then we have a different problem: 100% of the birds in the chart are being shown to have descended from a single source rather than from the reported four different sources.

Either way, the chart does not shed enough light on the article to make clear what's going on with the math.

[Doppleganger]

Colonel Sanders really digs the Galloanseres common ancestor.

[SW!FT]

Why doesn't this thread receive more attention

I like this thread