Thursday, 27 August 2015

Oh No! Not Transitional Penguins!

Eocene Penguin from Peru
New fossil skulls reveal insights about penguin brain evolution -- ScienceDaily

Some 35 million years ago, stem penguins were doing something creationists insist never happens; they were transitioning from flying species to aquatic species.

Evolutionary transition is something that any self-respecting creationist will have had lots of practice at denying because examples of it are so abundant in the fossil record - where they shouldn't be if everything was created as is, by magic. So, rather than incorporate these facts into their world view, they retain their evidence-free world view by denying the facts. This is how we know creationism is a dogma, not a science.

The Antarctic fossils reveal that the neuroanatomy of penguins was still evolving roughly 30 million years after the loss of aerial flight, with trends such as the expansion of the Wulst and reduction of the olfactory bulbs still in progress.

Daniel T. Ksepka, co-author.
There are plenty of diving birds, of course, but penguins are unique in that they 'fly' through the water using their wings much as flying birds use them to fly through air, and not like other aquatic vertebrates such as seals and whales use their modified limbs to swim with. A major part of this transition included changes in the sensory systems and this is primarily where the authors of this paper have found evidence of transition - in the brain and, consequently, in the brain case.

Penguins are considered flightless, but when it comes to wing-propelled diving they are essentially practicing underwater flight. The brain morphology reflects this as penguins retain an overall "flight-ready" brain.

Daniel T. Ksepka.
By comparing virtual endocasts of three fossil skulls from different early penguin species, found in 35 million year-old sedimentary deposits from the Eocene on Seymour Island, Antarctica, with those of living species, Claudia P. Tambussi and her colleagues have shown that major sensory areas of the brain were still evolving with increases in the area of the brain associated with complex visual functions, and a reduction in the area associated with the sense of smell.

Additional changes to the ear are consistent with changes in the alignment of the head. Many of these modifications are to be found in modern penguins but these earlier specimens had structures normally found in flying birds, showing that these species were still evolving, transitioning between flying birds and the modern aquatic, flightless penguins.

Penguins have a more than 60 million year long evolutionary history. Thus, stem lineage fossil taxa are key to understanding their evolution. Here, we present data on three virtual endocasts from stem penguin skulls collected from the Eocene La Meseta Formation of Seymour Island (Antarctica), along with comparative data from extant penguins and outgroups. These fossils appear to belong to three distinct species, and represent both the oldest (34.2 Ma) and the most basal penguin taxa that have yielded endocast data. Data collected from the fossils provide new support for several important shifts in neuroanatomy and cranial skeletal anatomy along the transition from stem to crown penguins, including (1) caudal expansion of the eminentia sagittalis, (2) an increase in the overlap of the telencephalon onto the cerebellum, (3) reduction of the bulbus olfactorius, and (4) loss of the interaural pathway. The large semicircular canal diameters of the Antarctic fossils as well as the more crownward stem penguin Paraptenodytes antarcticus together suggest that canal size increased in basal penguins relative to outgroup taxa but later decreased near the crown radiation. As in most other wing-propelled diving birds, the endocasts lack evidence of cerebellar folds and possess a relatively large floccular recess. Several aspects of the endocast morphology, including the exposure of the tectum opticum in dorsal view and the rostral displacement of the eminentia sagittalis away from the border of the cerebellum, are seen neither in crown penguins nor in Procellariiformes (the extant sister clade to Sphenisciformes) and so appear to represent unique characters of these stem taxa.*

So, there we have yet another example of transitional fossils and, consistent with common descent, these early penguins retain vestiges of adaptation for flight.

Apart from the usual infantile denialism and gibberish about 'kinds' and still being penguins, which is frankly an insult to the intelligence of normal people, would any creationist like to explain here how these fit in with a special creation of all living things by magic, why this assumed creator created these long-extinct penguins to look millions of years old and exactly like you would expect early penguins to look like if they evolved out of flying birds and why it gave them vestigial adaptations for flight?

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