CICTERRA   20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Endocranial anatomy of Madrynornis mirandus (Aves, Sphenisciformes), a crown-penguin from the early late Miocene of Patagonia
Autor/es:
DEGRANGE, F.J.; TAMBUSSI, C.P.
Lugar:
Dallas
Reunión:
Congreso; 75th Society of Vertebrate Paleontology Meeting; 2015
Resumen:
By studying the brain and
inner ear anatomy of the early late Miocene (Tortonian, 11.6 - 7.2 Ma) crown
penguin Madrynornis mirandus
(MEF-PV100), it was our aim to find out more about the transition from stem to
crown penguins. Previous phylogenetic studies show Madrynornis mirandus
as closely related to the living Yellow-eyed Penguin and the crested penguins
of the genus Eudyptes. The three-dimensional visualization of its
endocranial anatomy in a comparative frame (stem and extant penguins and
outgroups) reveals some shared characteristics
with extant penguins while others with the stem penguins (Patagonian Miocene Paraptenodytes + Antarctic Eocene
penguins). Among the first, the brain is airencephalic, the wulst are less
caudally expanded but more dorsally extended than in extant penguins, the optic
lobes are cranially located but relatively less developed, the interaural
pathway (the contralateral
connection between the paired rostral tympanic recesses) is absent, the
general pattern of the tympanic recesses is simple without cancellae, the carotid anastomosis is X-type (similar to Spheniscus). Secondly, the telencephalon is relativelly longer and
narrower and the flocculi are stouter and more laterally disposed than in extant
penguins. Because the posterior portion of the skull is broken, brain volume
and consequently encephalization quotient, could not be estimated. Madrynornis mirandus also shows the
retention of primitive morphologies such as large olfactory bulbs and high
olfactory ratio (35.7) suggesting higher levels of olfactory sensitivity than
extant taxa. The
latter may indicate exceptional smell sensory abilities that would be expected
from predatory animals. These new data holds a large potential to learn
more about the evolution of the brain in penguins. Research support was provided by CONICET (PIP 112 20130100059 CO) and UNLP N671.