Chapter 9 - Anatomy of skull and mandible
The skull of the bowhead whale is composed of all the bones commonly found in mammals, although the shape of these bones is far from ordinary. Features related to feeding dominate the skull: there are no teeth, and the rostrum is long and curved, resembling a bow. The incisive and maxilla form a high arch that forms the origin of the baleen rack, and the mandibles are straight in lateral view, but deeply curved in the horizontal plane to make room for the tongue and baleen. The blowhole is located near the apex of the skull, and the boney portion of the nasal passage opens caudally into the nasopharynx ventral to the braincase. As in other baleen whales, the occipital projects rostrally, covering a portion of the parietals and frontals.
Hillmann DJ; Tarpley RJ; George JC; Nader PB; Thewissen JGM
The Bowhead Whale
2021
Book Chapter
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Chapter 9 - Anatomy of skull and mandible
bones; whale; Bowhead whale; skull; mandible; osteology; Balaena mysticetus;
The skull of the bowhead whale is composed of all the bones commonly found in mammals, although the shape of these bones is far from ordinary. Features related to feeding dominate the skull: there are no teeth, and the rostrum is long and curved, resembling a bow. The incisive and maxilla form a high arch that forms the origin of the baleen rack, and the mandibles are straight in lateral view, but deeply curved in the horizontal plane to make room for the tongue and baleen. The blowhole is located near the apex of the skull, and the boney portion of the nasal passage opens caudally into the nasopharynx ventral to the braincase. As in other baleen whales, the occipital projects rostrally, covering a portion of the parietals and frontals.
Hillmann DJ; Tarpley RJ; George JC; Nader PB; Thewissen JGM
The Bowhead Whale
2021
2021-01-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
journalArticle
<a href="http://doi.org/10.1016/B978-0-12-818969-6.00009-1" target="_blank" rel="noreferrer noopener"></a>
Dental morphology of Remingtonocetidae (Cetacea, Mammalia)
eocene; Paleontology; whale
Thewissen J G M; Bajpai S
Journal of Paleontology
2001
2001-03
Journal Article
<a href="http://doi.org/10.1666/0022-3360(2001)075%3C0463:dmorcm%3E2.0.co;2" target="_blank" rel="noreferrer noopener">10.1666/0022-3360(2001)075%3C0463:dmorcm%3E2.0.co;2</a>
An analysis of von Economo neurons in the cerebral cortex of cetaceans, artiodactyls, and perissodactyls
Anatomy & Morphology; anterior cingulate cortex; bowhead whale; brain; cetartiodactyla; Cingulate; cortex; Cortical evolution; evolution; evolution; Fork cells; frontoinsular cortex; great apes; Insula; Neurosciences & Neurology; phylogeny; spindle neurons; variant frontotemporal dementia; Von Economo neurons (VENs); whale
Von Economo neurons (VENs) are specialized projection neurons with a characteristic spindle-shaped soma and thick basal and apical dendrites. VENs have been described in restricted cortical regions, with their most frequent appearance in layers III and V of the anterior cingulate cortex, anterior insula, and frontopolar cortex of humans, great apes, macaque monkeys, elephants, and some cetaceans. Recently, a ubiquitous distribution of VENs was reported in various cortical areas in the pygmy hippopotamus, one of the closest living relatives of cetaceans. That finding suggested that VENs might not be unique to only a few species that possess enlarged brains. In the present analysis, we assessed the phylogenetic distribution of VENs within species representative of the superordinal clade that includes cetartiodactyls and perissodactyls, as well as afrotherians. In addition, the distribution of fork cells that are often found in close proximity to VENs was also assessed. Nissl-stained sections from the frontal pole, anterior cingulate cortex, anterior insula, and occipital pole of bowhead whale, cow, sheep, deer, horse, pig, rock hyrax, and human were examined using stereologic methods to quantify VENs and fork cells within layer V of all four cortical regions. VENs and fork cells were found in each of the species examined here with species-specific differences in distributions and densities. The present results demonstrated that VENs and fork cells were not restricted to highly encephalized or socially complex species, and their repeated emergence among distantly related species seems to represent convergent evolution of specialized pyramidal neurons. The widespread phylogenetic presence of VENs and fork cells indicates that these neuron morphologies readily emerged in response to selective forces,whose variety and nature are yet to be identified.
Raghanti M A; Spurlock L B; Treichler F R; Weigel S E; Stimmelmayr R; Butti C; Thewissen Jgmh; Hof P R
Brain Structure & Function
2015
2015-07
Journal Article
<a href="http://doi.org/10.1007/s00429-014-0792-y" target="_blank" rel="noreferrer noopener">10.1007/s00429-014-0792-y</a>
Sensory Hairs in the Bowhead Whale, Balaena mysticetus (Cetacea, Mammalia).
anatomy; Animals; Bowhead Whale/*anatomy & histology; Cetacea; Epidermis; hair; Hair/*anatomy & histology; Lip/anatomy & histology; vibrissa; whale
We studied the histology and morphometrics of the hairs of bowhead whales (Balaena mysticetus). These whales are hairless except for two patches of more than 300 hairs on the rostral tip of the lower lip and chin, the rostral tip of the upper lip, and a bilateral row of approximately ten hairs caudal to the blowhole. Histological data indicate that hairs in all three of these areas are vibrissae: they show an outermost connective tissue capsule, a circumferential blood sinus system surrounding the hair shaft, and dense innervation to the follicle. Morphometric data were collected on hair diameters, epidermal recess diameters, hair follicle length, and external hair lengths. The main difference between the hairs in the different regions is that blowhole hairs have larger diameters than the hairs in the chin and rostrum regions. We speculate that the hair shaft thickness patterns in bowheads reflect functional specializations.
Drake Summer E; Crish Samuel D; George John C; Stimmelmayr Raphaella; Thewissen J G M
Anatomical record (Hoboken, N.J. : 2007)
2015
2015-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ar.23163" target="_blank" rel="noreferrer noopener">10.1002/ar.23163</a>