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Paraptenodytes antarcticusFossil, Fossil Stem Penguin
Dr. Daniel T. Ksepka - North Carolina State University
A.M. Balanoff, S. Walsh, A. Revan and A. Ho
Paraptenodytes antarcticus
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skull
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American Museum of Natural History (AMNH 3338)

Image processing: Dr. Amy Balanoff
Publication Date: 09 Aug 2012

ITIS TNS Google MSN

The imagery on this page is the basis for a paper entitled Evolution of the brain and sensory organs in Sphenisciformes: new data from the stem penguin Paraptenodytes antarcticus, by D.T. Ksepka, A.M. Balanoff, S. Walsh, A. Revan and A. Ho (2012, Zoological Journal of the Linnean Society, 166, 202-219). The abstract is as follows:

Penguins have undergone dramatic changes associated with the evolution of underwater flight and subsequent loss of aerial flight, which are manifest and well documented in the musculoskeletal system and integument. Significant modification of neurosensory systems and endocranial spaces may also be expected along this locomotor transition. However, no investigations of the brain and sensory organs of extinct stem lineage Sphenisciformes have been carried out, and few data exist even for extant species of Spheniscidae. In order to explore neuroanatomical evolution in penguins, we generated virtual endocasts for the early Miocene stem penguin Paraptenodytes antarcticus, three extant penguin species (Pygoscelis antarctica, Aptenodytes patagonicus, Spheniscus magellanicus), and two outgroup species (the common loon Gavia immer and the Laysan albatross Phoebastria immutabilis). These endocasts yield new anatomical data and phylogenetically informative characters from the brain, carotid arteries, pneumatic recesses, and semicircular canal system. Despite having undergone over 60 million years of evolution since the loss of flight, penguins retain many attributes traditionally linked to flight. Features associated with visual acuity and proprioception, such as the sagittal eminence and flocculus, show a similar degree of development to those of volant birds in the three extant penguins and Paraptenodytes antarcticus. These features, although clearly not flight-related in penguins, are consistent with the neurological demands associated with rapid manoeuvring in complex aquatic environments. Semicircular canal orientation in penguins is similar to volant birds. Interestingly, canal radius is grossly enlarged in the fossil taxon Pa. antarcticus compared to living penguins and outgroups. In contrast to all other living birds, the contralateral anterior tympanic recesses of extant penguins do not communicate. An interaural pathway connecting these recesses is retained in Pa. antarcticus, suggesting that stem penguins may still have employed this connection, potentially to enhance directional localization of sound. Paedomorphosis, already identified as a potential factor in crown clade penguin skeletal morphology, may also be implicated in the failure of an interaural pathway to form during ontogeny in extant penguins.

About the Species

This specimen was collected from the early Miocene of Patagonia. It was made available to DigiMorph by Dr. Amy Balanoff of the American Museum of Natural History.

About this Specimen

This specimen was scanned at Stony Brook University Hospital using a GE Lightspeed 16 medical scanner. The interslice spacing was 0.1 mm, and the interpixel spacing was 0.1875 mm.

About the
Scan
Literature

Bertelli, S., Giannini, N.P., and Ksepka, D.T. 2006. Redescription and phylogenetic position of the early Miocene penguin Paraptenodytes antarcticus from Patagonia. American Museum Novitates 3525:1-36.

Literature
& Links
braincase with endocast roll movie

Click on the thumbnail to the left for a roll animation (3.8 mb) of the Paraptenodytes endocast rendered within the semi-transparent braincase.

endocast roll movie

Click on the thumbnail to the left for a roll animation (2.6 mb) of the Paraptenodytes endocast.

endocast yaw movie

Click on the thumbnail to the left for a yaw animation (2.3 mb) of the Paraptenodytes endocast.

endocast pitch movie

Click on the thumbnail to the left for a pitch animation (3.0 mb) of the Paraptenodytes endocast.

Additional
Imagery

To cite this page: Dr. Daniel T. Ksepka, A.M. Balanoff, S. Walsh, A. Revan and A. Ho, 2012, "Paraptenodytes antarcticus" (On-line), Digital Morphology. Accessed November 23, 2014 at http://digimorph.org/specimens/Paraptenodytes_antarcticus/.

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