The co-evolution of social behavior and cranial morphology in sheep and goats (Bovidae, caprini) [by] William M. Schaffer and Charles A. Reed.

Reed, Charles A.; Schaffer, William M.

doi:10.5962/bhl.title.2828

Cited by 31 publications

(61 citation statements)

References 16 publications

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“…The idea of frontal sinuses as 'shock absorbers' is often repeated in the literature (e.g. Geist, 1966;Schaffer and Reed, 1972) and has even been used, by analogy, to reveal the function of sinuses in extinct dinosaurs such as Triceratops (Molnar, 1977;Forster, 1996). Despite this, the idea of sinuses as protective structures remains completely untested.…”

Section: Introductionmentioning

confidence: 99%

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Frontal sinuses and head-butting in goats: a finite element analysis

Farke

2008

Journal of Experimental Biology

100

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SUMMARYFrontal sinuses in goats and other mammals have been hypothesized to function as shock absorbers, protecting the brain from blows during intraspecific combat. Furthermore, sinuses are thought to form through removal of ʻstructurally unnecessaryʼ bone. These hypotheses were tested using finite element modeling. Three-dimensional models of domesticated goat (Capra hircus) skulls were constructed, with variable frontal bone and frontal sinus morphology, and loaded to simulate various head-butting behaviors. In general, models with sinuses experienced higher strain energy values (a proxy for shock absorption) than did models with unvaulted frontal bones, and the latter often had higher magnitudes than models with solid vaulted frontal bones. Furthermore, vaulted frontal bones did not reduce magnitudes of principal strain on the surface of the endocranial cavity relative to models with unvaulted frontal bones under most loading conditions. Thus, these results were only partially consistent with sinuses, or the bone that walls the sinuses, acting as shock absorbers. It is hypothesized that the keratinous horn sheaths and cranial sutures are probably more important for absorbing blows to the head. Models with sinuses did exhibit a more ʻefficientʼ distribution of stresses, as visualized by histograms in which models with solid frontal bones had numerous unloaded elements. This is consistent with the hypothesis that sinuses result at least in part from the removal of mechanically unnecessary bone. Supplementary material available online at

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Section: Introductionmentioning

confidence: 99%

“…As suggested by Schaffer and Reed (Schaffer and Reed, 1972), the outer walls of the sinus or the struts within the sinus could deform during impact, in place of deformation of the endocranium. Thin walls of bone would be more deformable than solid bone.…”

Section: Introductionmentioning

confidence: 99%

Frontal sinuses and head-butting in goats: a finite element analysis

Farke

2008

Journal of Experimental Biology

100

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“…For example, if brain size scales negatively with skull size, sinuses may expand to fill the frontal bone to increase the surface area for attachment of masticatory muscles in large animals. Other hypotheses include decreasing the weight of the skull (Davis et al, 1996;Mitchell and Skinner, 2003;Shea, 1936), providing thermoregulation of the brain (Bremer, 1940;Dyce et al, 2002;Ganey et al, 1990;Skinner, 2003, 2004), shock absorption during head-butting or neck-sparring (Badlangana et al, 2011;Davis et al, 1996;Schaffer and Reed, 1972), serving as a resonance chamber for the production of low frequency sounds (Leakey and Walker, 1997;von Muggenthaler et al, 1999) and dissipation of stress over the skull during mastication, and particularly bone-cracking in carnivores (Buckland-Wright, 1971, 1978Joeckel, 1998;Tanner et al, 2008). Nonetheless, hypotheses regarding sinus function are difficult to test without first obtaining data on sinus variation within and between species.…”

Section: Introductionmentioning

confidence: 99%

A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Sharp¹

2016

MMV

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Sharp, A.C. 2016. A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials. Memoirs of Museum Victoria 74: 331-342.Cranial sinuses result from the resorption and deposition of bone in response to biomechanical stress during a process known as pneumatisation. The morphology of a pneumatic bone represents an optimisation between strength and being light weight. The presence of very large sinuses has been described in a number of extinct marsupial megafauna, the size of which no longer exist in extant marsupials. With advances in digital visualisation, and the discovery of a number of exceptionally preserved fossil crania, a unique opportunity exists to investigate hypotheses regarding the structure and evolution of the atypically voluminous sinuses. Sinus function is difficult to test without first obtaining data on sinus variation within and between species. Therefore, the crania of seven species of extinct and extant vombatiform marsupials were studied using CT scans to provide a volumetric assessment of the endocast and cranial sinuses. Sinus volume strongly correlates with skull size and brain size. In the extinct, large bodied palorchestids and diprotodontids the sinuses expand around the dorsal and lateral parts of the braincase. Brain size scales negatively with skull size in vombatiform marsupials. In large species the brain typically fills less than one quarter of the total volume of the endocranial space, and in very large species, it can be less than 10%. Sinus expansion may have developed in order to increase the surface area for attachment of the temporalis muscle and to lighten the skull. The braincase itself would have provided insufficient surface area for the predicted muscle masses.

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“…10 shows exactly how the benefits and costs are assessed. Moreover, by plotting Bx(pxvx+ 1/vo) against px(vx+ I/vo), the circumstances favoring the evolution of semelparity, iteroparity, or some combination of the two can be described (6,7,24,25).…”

Section: Discussionmentioning

confidence: 99%

Equivalence of maximizing reproductive value and fitness in the case of reproductive strategies

Schaffer

1979

Proc. Natl. Acad. Sci. U.S.A.

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The proposed equivalence of maximizing reproductive value and fitness is examined for two model life histories. In the first instance, it is assumed that offspring are fledged before the start of the next breeding season. In this case the proposed equivalence is verified. In the second model, parents care for their progeny for more than 1 year. In this case the optimal reproductive expenditure at a particular age is shown to depend on both current reproductive value and the diminution in survival rates of previously conceived young still dependent on parental protection.Recently, there has been considerable theoretical interest in the evolution of life history phenomena (1-8). The problem, first stated explicitly by Gadgil and Bossert (4), is as follows. Consider an organism with limited (i.e., finite) resources at its disposal. Further suppose that there exists heritable variation with regard to the manner in which these resources are allocated. Then, one wishes to determine the schedule of allocation-to growth, to reproduction, and to maintenance-that maximizes the individual's contribution to subsequent generations.In attempting to answer this question, several authors (5, 6, 8, 9) have proposed that the allocation schedule in question is that which maximizes reproductive value (10) at all ages. More recently, however, this view has been questioned (1, 2). In particular, it has been suggested that maximizing fitness and reproductive value and fitness are equivalent only under the restrictive circumstance that trade-offs between current fecundity and subsequent survival and growth are confined to operate within (and not between) age classes. The purpose of the present paper is to examine this question in detail. Specifically, it is argued that maximizing fitness and reproductive value is indeed equivalent, provided that increased expenditures for reproduction at age x do not adversely affect fecundity and survivorship at previous ages y (y < x). This assumption would appear to be met in nearly all cases, save those in which there is extended parental care. In such instances, offspring as yet unfledged can suffer increased mortality if the parents breed a second time and turn their attention to the more recent litter. Mathematically, this is equivalent to reducing the parents' fecundity at earlier ages and, in such cases, natural selection can be expected to maximize reproductive value plus a weighted sum of prior years' reproduction. An analysis of this case is given. ANALYSISPreliminaries. Consider an organism with the life cycle depicted in Fig. 1. The population is censused once a year during the breeding season, nx(t) being the number of xyear-old individuals alive in year t. Let mx be the number of offspring produced by an x-year-old individual. Of these, cx survive to be counted as young of the year (yearlings) the fol- Each of these produces mi offspring of which ci survive to the breeding season in their first year of life (zeroth age class). The product cimi = Bi is termed the effective fecun...

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The co-evolution of social behavior and cranial morphology in sheep and goats (Bovidae, caprini) [by] William M. Schaffer and Charles A. Reed.

Cited by 31 publications

References 16 publications

Frontal sinuses and head-butting in goats: a finite element analysis

Frontal sinuses and head-butting in goats: a finite element analysis

A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Equivalence of maximizing reproductive value and fitness in the case of reproductive strategies

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