Aristelliger barbouri

Number of Pages: 1Integrative BiologyGeological Science

Aristelliger

Number of Pages: 4Integrative BiologyGeological Science

Thecadactylus, T. rapicauda

Number of Pages: 16Integrative BiologyGeological Science

Aristelliger georgeensis

Number of Pages: 2Integrative BiologyGeological Science

Anolis garmani

Number of Pages: 3Integrative BiologyGeological Science

On the Origin of Frictional Adhesion in Geckos: Small Morphological Changes Lead to a Major Biomechanical Transition in the Genus \u3cem\u3eGonatodes\u3c/em\u3e

The evolutionary history of vertebrate locomotion is punctuated by innovations that have permitted expansion into novel ecological niches. Frictional adhesion of geckos is an innovation renowned for enabling locomotion on vertical and inverted smooth surfaces. Much is known about the microstructure and function of the fully-expressed gekkotan adhesive apparatus, although how it originated is poorly understood. Therefore, identifying species that exhibit the earliest stages of expression of frictional adhesion will provide significant insights into the evolution of this trait. Our previous investigation of digital proportions, shape, scalation, skeletal form, and subdigital epidermal micro-ornamentation in the genus Gonatodes led us to hypothesize that Gonatodes humeralisexpresses incipient frictional adhesion. To test this, we first conducted a phylogenetic analysis of Gonatodes and related sphaerodactyl genera to clarify the historical context of the evolution of frictional adhesive capability in the genus. We then measured the ability of G. humeralis and its close relatives to generate frictional adhesive force, examined their locomotor capabilities on low-friction surfaces, and observed animals in their natural habitat. After accounting for body mass and phylogenetic relationships, we found that G. humeralis generates frictional adhesive force essentially equivalent to that of Anolis, and can scale vertical smooth surfaces. Gonatodes vittatus, a species that lacks elaborated epidermal setae, generates negligible frictional adhesive force and can only ascend smooth inclined surfaces with a pitch of ≤ 40°. We conclude that the ostensibly padless G. humeralis, with feet lacking the musculoskeletal, tendinous, and vascular modifications typical of pad-bearing geckos, nevertheless can employ frictional adhesive contact to assist locomotion. As in Anolis, the release of frictional adhesive contact occurs when the foot is plantar flexed after the heel has lifted from the surface. Our findings indicate that the origin of frictional adhesion was likely gradual but that, ultimately, this led to major shifts in ecology and function

Literature, Pandemic, and the Insufficiency of Survival: Boccaccio’s Decameron and Emily St. John Mandel’s Station Eleven

The question of literature’s utility in relation to the “real world” has been asked since at least the time of Plato. This essay examines an extreme instance of this problem by investigating two works, Giovanni Boccaccio’s Decameron (1349-1353) and Emily St. John Mandel’s Station Eleven (2016), that argue for the value of art in the midst of catastrophe. Boccaccio’s collection of 100 tales, written in the context of the Black Plague, and Mandel’s post-apocalyptic novel about a world devastated by a killer flu, overlap and diverge in instructive ways in making their cases for the important role of literature in confronting suffering, trauma, and loss. Specifically, this essay contrasts Boccaccio’s vision of literature as encouraging a lucidly compassionate embrace of flawed humankind that looks to the future, and Mandel’s evocation of Shakespeare as a trope for civilization that is more nostalgically oriented towards the recovery of the past as a response to the tragic present

The genera Rhoptropus and Phelsuma (Reptilia: Gekkonidae) in Southern Africa: A case of convergence and a reconsideration of the biogeography of Phelsuma

The genus Rhoplropella Hewitt, 1937 is shown to be a junior synonym of Phelsuma Gray, 1825 and the genera Phelsumaand Rhoplropus Peters, 1869 are compared. It is pointed out that Phelsuma ocettata shows a great deal of convergence with Rhoplropus but that both of these forms exhibit their own distinctive derived character combinations. The distribution pattern of Phelsuma on the main-land of Africa and on Madagascar is reviewed inthe light of current theories of biogeography and past continental relationships. It is suggested that the distribution of Phelsuma may represent a track which is also occupied by other reptilian genera

Correction techniques for depth errors with stereo three-dimensional graphic displays

Three-dimensional (3-D), 'real-world' pictorial displays that incorporate 'true' depth cues via stereopsis techniques have proved effective for displaying complex information in a natural way to enhance situational awareness and to improve pilot/vehicle performance. In such displays, the display designer must map the depths in the real world to the depths available with the stereo display system. However, empirical data have shown that the human subject does not perceive the information at exactly the depth at which it is mathematically placed. Head movements can also seriously distort the depth information that is embedded in stereo 3-D displays because the transformations used in mapping the visual scene to the depth-viewing volume (DVV) depend intrinsically on the viewer location. The goal of this research was to provide two correction techniques; the first technique corrects the original visual scene to the DVV mapping based on human perception errors, and the second (which is based on head-positioning sensor input data) corrects for errors induced by head movements. Empirical data are presented to validate both correction techniques. A combination of the two correction techniques effectively eliminates the distortions of depth information embedded in stereo 3-D displays

Effect of short-term exposure to stereoscopic three-dimensional flight displays on real-world depth perception

High-fidelity color pictorial displays that incorporate depth cues in the display elements are currently available. Depth cuing applied to advanced head-down flight display concepts potentially enhances the pilot's situational awareness and improves task performance. Depth cues provided by stereopsis exhibit constraints that must be fully understood so depth cuing enhancements can be adequately realized and exploited. A fundamental issue (the goal of this investigation) is whether the use of head-down stereoscopic displays in flight applications degrade the real-world depth perception of pilots using such displays. Stereoacuity tests are used in this study as the measure of interest. Eight pilots flew repeated simulated landing approaches using both nonstereo and stereo 3-D head-down pathway-in-the-sky displays. At this decision height of each approach (where the pilot changes to an out-the-window view to obtain real-world visual references) the pilots changed to a stereoacuity test that used real objects. Statistical analysis of stereoacuity measures (data for a control condition of no exposure to any electronic flight display compared with data for changes from nonstereo and from stereo displays) reveals no significant differences for any of the conditions. Therefore, changing from short-term exposure to a head-down stereo display has no more effect on real-world relative depth perception than does changing from a nonstereo display. However, depth perception effects based on sized and distance judgements and on long-term exposure remain issues to be investigated