sexta-feira, 2 de janeiro de 2009

Opinions on non-Galliforme/Anseriforme Galloanserae

Providing the fact toothed seabirds took most of Spec's seabird niches, I had to change the pseudodontorns from gannet/albatross/pelican analogues into Spec's mergansers. I've also decided to express my opinion on Gastorniformes and on dromornids

Galloanserae is an old linage of Neornithe birds, which has included, across the history of both worlds, both fowl and waterfowl; both groups are actually on the opposite sides of the cladistic tree, since Galliformes are the most basal and Anseriformes are within a larger clade that also included at least two other groups (though one of these groups might belong within Anseriformes; see below). Both groups are still alive in Spec, though neither developed the spectacular forms present on HE.

One of these groups is Gastorniformes. On HE, they develop spectacular forms such as Gastornis, flightless and huge; their huge bills might had been used to crush their prey, though its not clear if they were carnivores (though its more likely they ate meat than their aussie relatives, the dromornids). On Spec, this clade is alive and well in South America (its interesting to note that, on HE, there was another giant, flightless relative of waterfowl known as Brontornis, though it wasn't a Gastorniforme [unless the features that unite them to Drmornidae and Anseriformes are resulted from parallel evolution]), where they took the niches of Galliformes. They are quite similar to HE's screamers, which are true Anseriformes, and which never evolved in Spec (though their closest relatives, magpie geese, occur in Australasia, and gave rise to the huge flightless "geese" in New Zealand). A similar niche is occupied in Oz by very similar birds, though they might be dromornids; in both landmasses there's arboreal Galliformes as well.

Pseudodontorns are the other group of Galloanseres that got extinct on HE; in Spec, they still exist, though they never developed the albatross like forms that evolved on our timeline. These ncihes were taken by Ichthyorniformes, which took over most seabird niches but those of large diving birds (those are held by Hesperorniformes and penguins). Instead, these actually occupy a somewhat marginal niche, but still interesting to note because they managed to prevent Anseriformes from taking it: that of mergansers. On HE there's at least 4 linages of diving freshwater birds, and Spec has 3. Mergansodontorns have their earliest fossils dating from the Eocene, though its possible their origins extend to the Cretaceous, since Pseudodontorns weren't very specialized at that time

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