"Morphological Diversity of Neurocrania in Sharks (Chondrichthyes: Elas" by Jake J. Wood
College of Science and Health Theses and Dissertations

Date of Award

Summer 8-20-2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Science

First Advisor

Windsor Aguirre, PhD

Second Advisor

Eric Norstrom, PhD

Third Advisor

Kenshu Shimada, PhD

Abstract

Sharks occupy a wide range of ecological niches and lifestyle strategies attributed to their complex sensory system housed in their neurocranium. However, the diversity of neurocranial morphology in sharks and how the diversity may be related to their sensory capability have never been adequately surveyed. Therefore, the aims of this present study were: 1) to examine whether the relative sizes of rostral, olfactory, optic, and/or otic regions of neurocrania in sharks are related to their habitat, diet, and/or body form types; and 2) to investigate any possible patterns and insights into the ecology and evolution of sharks on the basis of neurocranial diversity. My primary dataset comprised neurocrania of 182 extant species in 37 families and 102 genera, along with 10 extinct elasmobranch taxa, representing the most comprehensive survey of the neurocranial diversity of sharks to date. My study suggests that there is a statistically significant difference between each of the four examined neurocranial regions and habitat, diet, and body form types, except for the relationship of the optic region size with the habitat types and body form types. My geometric morphometric analysis indicates that the rostral length and cranial width are the most variable parts of the shark neurocranium, where there appears to be only one general neurocranial morphology in sharks that is characterized by a relatively slender skull with a short rostrum. Whereas this morphological condition is regarded as plesiomorphic, my study reveals that the general neurocranial morphology could be evolutionarily modified in two different ways by elongating the rostrum or by broadening the cranial width. The skulls of most examined extinct sharks are represented by the generalized neurocranial morphology, but Lamniformes exhibit the greatest neurocranial diversity among all the shark orders examined. In addition to providing information about their ecology and evolutionary biology, my study offers new information that can be used for the conservation of sharks.

SLP Collection

no

Included in

Biology Commons

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