Quantitative Kinematic Research Articles

Sprawling locomotion in the lizard Sceloporus clarkii: quantitative kinematics of a walking trot

Although the hindlimb is widely considered to provide the propulsive force in lizard locomotion, no study to date has investigated the kinematic patterns of the lizard hindlimb during running for more than one stride for a single individual. The quantitative kinematics of the hindlimb, pelvis and backbone are described here for two individuals of the lizard Sceloporus clarkii using a fast walking trot on a treadmill moving at a constant speed of 0.833 m s-1. Pelvic rotation, femoral retraction, knee flexion and posterior movement of the foot all begin before the foot hits the substratum and, thus, there is a terminal portion of the swing phase during which the limb is retracting. Pelvic rotation (to the opposite side), femoral protraction and knee flexion all begin before the foot leaves the substratum. The foot, however, continues to move posteriorly into the early swing phase. Thus, limb retraction and protraction movements do not directly correlate with footfall phases. Axial bending involves a rough standing wave with two nodes, one centered on each limb girdle. In Sceloporus clarkii, the foot clearly remains lateral to the knee and, thus, has a more sprawling posture than that of any other vertebrate studied to date. Therefore, the generalization that the 'lacertilian' foot passes under the knee joint is no longer supported. The kinematics of sprawling locomotion in Sceloporus clarkii are compared and contrasted with the general understanding of lizard locomotion based on qualitative work to date. Comparisons with other tetrapods reveal a fundamental functional dichotomy in hindlimb retraction mechanics in salamanders and mammals versus lizards that may be related to a key morphological difference in the saurian caudifemoralis muscle.

Stratigraphic and kinematic modeling of thrust evolution, northern Apennines, Italy

We present a quantitative kinematic model of thrust evolution that allows detailed interpretation of the stratigraphic record of foreland basins. Simulation of thrusting and syntectonic sedimentation shows that changes in the relative rate of thrusting and mode of thrust activation can be determined by their expression in basin stratigraphy. Truncations and offlaps reflect thrust activity, and hinterland migration of basin depocenters indicates out-of-sequence thrusting. Forward modeling of the stratigraphic record of the Pliocene-Quaternary Po basin, Italy, enables the quantitative reconstruction of the displacement sequence of the thrust sheets prograding into the basin during the Pliocene. Deep-seated middle Pliocene thrusting accompanied by out-of-sequence thrusting provides a consistent explanation for the observed stratigraphic record of the Po piggyback basins.

The problem of the deep structure of the Southern Alps: 3-D material balance considerations and regional consequences

The Lombardic Southern Alps are a typical thin-skinned frontal fold- and thrust belt. Although this recent reassessment is widely accepted, figures for shortening and schemes for transfer of shortening at their eastern end in the Giudicarie vary. Exact section balancing is not feasible because of insufficient information, but approximate shortening is on an order probably exceeding 100 km, with about 80–100 km attributable to the Middle to Late Miocene “Milan belt”. Acceptance of this quantitative conclusion has farreaching consequences. Transfer of the Milan belt shortening in the east follows the lateral edge of the allochthon which is sinistrally transpressive, the Giudicarie line, with its sedimentary décollement zone, the Giudicarie belt. The pre-existing Adamello intrusions and the Jorio-Tonale line are part of the thrust masses and consequently allochthonous. Transfer of shortening across the Insubric line into the Tauern antiform and associated structures of Neo-Alpine compression in the Eastern Alps resulted in the sinistral dissection of the Insubric line at the Giudicarie line. Superposition of this compression on Pannonian stretching east of and transtensive motion at the Brenner line west of the Tauern produced a confusing structural pattern whose quantitative kinematics have not been worked out. Another sinistral, probably compressive transfer zone is postulated at the western end of the Milan belt. Retrodeformation leads simultaneously to both a straightening of the Insubric line and the connection of the Canavese line with the Villalvernia-Varzi-Levanto line to define the boundary of the Adriatic block at the beginning of Neo-Alpine deformation.

Kinetics of tongue projection in Ambystoma tigrinum: Quantitative kinematics, muscle function, and evolutionary hypotheses.

The projectile tongue of caudate amphibians has been studied from many perspectives, yet a quantitative kinetic model of tongue function has not yet been presented for generalized (nonplethodontid) terrestrial salamanders. The purposes of this paper are to describe quantitatively the kinnematics of the feeding mechanism and to present a kinetic model for the function of the tongue in the ambystomatid salamander Ambystoma tigrinum. Six kinematic variables were quantified from high-speed films of adult A. tigrinum feeding on land and in the water. Tongue protrusion reaches its maximum during peak gape, while peak tongue height is reached earlier, 15 ms after the mouth starts to open. Tongue kinematics change considerably during feeding in the water, and the tongue is not protruded past the plane of the gape. Electrical stimulation of the major tongue muscles showed that tongue projection in A. tigrinum is the combined result of activity in four muscles: the geniohyoideus, Subarcualis rectus 1, intermandibularis posterior, and interhyoideus. Stimulation of the Subarcualis rectus 1 alone does not cause tongue projection. The kinetic model produced from the kinematic and stimulation data involves both a dorsal vector (the resultant of the Subarcualis rectus 1, intermandibularis posterior, and interhyoideus) and a ventral vector (the geniohyoideus muscle), which sum to produce a resultant anterior vector that directs tongue motion out of the mouth and toward the prey. This model generates numerous testable predictions about tongue function and provides a mechanistic basis for the hypothesis that tongue projection in salamanders evolved from primitive intraoral manipulative action of the hyobranchial apparatus.

A quantitative kinematic theory of convection currents in the earth's mantle

Based on a system of structurally simple postulations the kinematics of mantle convection is derived. With regard to the strain-stress relations valid in the mantle and the energy source of the convection the theory is without any presumptions. In compliance with recent hydrodynamic investigations the flow is introduced rather as roll currents than as a hexagonal cell pattern. From the feasible types of current a theoretical topography is derived which is in quantitative agreement with the observed one. Also the distribution of the seismic discontinuities substantiates the validity of the expression. Finally, some suggestions are given for a hydrodynamic theory of mantle convection. This paper contains that part of the theory which is necessary for testing the calculations, while the relationship of the theory to other geological and geophysical problems are dealt with by the author [26]2).