[MARMAM] New paper on kogiid cranial morphology

Steven Thornton swthornt at g.coastal.edu
Tue Jun 16 16:34:05 PDT 2015


Dear MARMAM subscribers,

We are pleased to announce the publication of the following paper in The
Anatomical Record.

Thornton SW, McLellan WA, Rommel SA, Dillaman RM, Nowacek DP, Koopman HN,
Pabst DA (2015) Morphology of the nasal apparatus in pygmy (*Kogia
breviceps*) and dwarf (*K*. *sima*) sperm whales. Anat Rec 298: 1301-1326.

ABSTRACT: Odontocete echolocation clicks are generated by pneumatically
driven phonic lips within the nasal passage, and propagated through
specialized structures within the forehead. This study investigated the
highly derived echolocation structures of the pygmy (*Kogia breviceps*) and
dwarf (*K*. *sima*) sperm whales through careful dissections (N = 18 *K*.
*breviceps*, 6 *K*. *sima*) and histological examinations (N = 5 *K*.
*breviceps*). This study is the first to show that the entire kogiid sound
production and transmission pathway is acted upon by complex facial muscles
(likely derivations of the *m*. *maxillonasolabialis*). Muscles appear
capable of tensing and separating the solitary pair of phonic lips, which
would control echolocation click frequencies. The phonic lips are enveloped
by the “vocal cap,” a morphologically complex, connective tissue structure
unique to kogiids. Extensive facial muscles appear to control the position
of this structure and its spatial relationship to the phonic lips. The
vocal cap's numerous air crypts suggest that it may reflect sounds. Muscles
encircling the connective tissue case that surrounds the spermaceti organ
may change its shape and/or internal pressure. These actions may influence
the acoustic energy transmitted from the phonic lips, through this lipid
body, to the melon. Facial and rostral muscles act upon the length of the
melon, suggesting that the sound “beam” can be focused as it travels
through the melon and into the environment. This study suggests that the
kogiid echolocation system is highly tunable. Future acoustic studies are
required to test these hypotheses and gain further insight into the kogiid
echolocation system.

The article can be found at:

http://onlinelibrary.wiley.com/doi/10.1002/ar.23168/abstract

PDFs can be requested at swthornt at coastal.edu

Regards,
Steven Thornton
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