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Brain Volume and Brain Width in Mammals and Birds



From: Ben Creisler
bcreisler@gmail.com

A new paper that discusses brain size in theropods:

Soichiro Kawabe, Tetsuya Shimokawa, Hitoshi Miki, Takashi Okamoto,
Seiji Matsuda, Takuya Itou, Hiroshi Koie, Masato Kitagawa, Takeo
Sakai, Misato Hosojima and Hideki Endo (2013)
Relationship Between Brain Volume and Brain Width in Mammals and Birds.
Paleontological Research 17(3):282-293
doi: http://dx.doi.org/10.2517/1342-8144-17.3.282
http://www.bioone.org/doi/abs/10.2517/1342-8144-17.3.282


In this study, we explored the relationship between brain volume and
brain width in a wide range of extant mammals and birds in an effort
to determine whether brain width could be used as an appropriate
variable for estimating the brain volume of extinct species. The
relationship between brain volume and brain width in extant species
was assessed using computed tomography images of mammalian skulls from
55 species representing 13 orders, and avian skulls from 64 species
representing 21 orders. Brain volume and brain width showed a strong
linear correlation in both mammals and birds. We also discovered that
brain volume of extant as well as extinct mammals and birds can be
estimated on the basis of brain width. The brain widths of Cynodontia,
Triconodonta, and non-avian Theropoda were relatively narrower than
those of extant mammals and birds. This data indicates that compared
to their early ancestors, the brain width of both mammals and birds
has increased with respect to brain endocast volume. Thus, on the
basis of our results we have concluded that the relationship between
brain volume and brain width is useful for estimating the brain volume
of extinct mammals and birds. In addition, it was found that relative
brain width of both mammals and birds has increased throughout their
evolutionary history from early ancestors to extant species.