Research Sandra Nauwelaerts

Abstract

This project will investigate the evolution of limb osteology of perissodactyls (horses, rhinos and tapirs) using geometric morphometrics to gain insights into the comparative limb osteology of this group. Phylogenetic comparative methods will then be applied to the osteological data to investigate the evolution of adaptations to locomotion within the Perissodactyla, with a focus on equids (horses).

Researcher(s)

• Promoter: Aerts Peter
• Co-promoter: Nauwelaerts Sandra
• Fellow: Maclaren Jamie

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

The fossil horse sequence is a popular example of a phylogenetic pattern resulting from the evolutionary process. However, the seemingly transitional stages are actually derived from a scattered sampling of horse fossils within the multi-branched horse evolutionary tree. The current hypothesis is that the reduction in the number of digits was necessary for the cursorial lifestyle of today's horses. Lengthening of the distal segments and toe-tip running increased the stride length and thus the speed with which the animal can move. However, to avoid the increase in cost of swinging the heavier limbs, the digital number was reduced. Reinforcement of the middle toe might have also led to an improvement of the stability. The drawback to the reduction lies in loss in versatility and a decreased ability to run on compliant substrates. This project proposes to perform detailed comparative research on horses and their extant relatives. By studying donkeys, zebras, horses and closely related species, we will detect evolutionary patterns within this group. By studying how the animals move combined with a detailed study of the limb anatomy of the same species, we aim at providing insights in the mechanisms behind the reduction in digital number. The limb movements of the animals will be studied using traditional gait analyses techniques. Video material will be obtained synchronized with ground reaction forces and pressure data under the hooves. This information can be combined with inertial information in a calculation technique called inverse dynamics that will yield the joint power profiles over time. These profiles can be regarded as indications for motor control patterns. This will allow us to compare motor control patterns between the different species. These gait analysis experiments will be done in collaboration with European zoos. Finally, a forward dynamic modeling approach (imposing patterns of joint moments of extant species onto fossil limb morphologies) will be applied. Models of trait evolution will be used to discern how limb skeletal morphology and motor control patterns have evolved in perissodactyls. This will require integration with the results of the projects running in parallel carried by Jamie MacLaren and Sandra Nauwelaerts, both now funded by the FWO-Fl (project IDs resp. 29820 & 27210).

Researcher(s)

• Promoter: Aerts Peter
• Co-promoter: Nauwelaerts Sandra
• Fellow: Kaashoek Mariëlle

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

This project will investigate the evolution of limb osteology of perissodactyls (horses, rhinos and tapirs) using geometric morphometrics to gain insights into the comparative limb osteology of this group. Phylogenetic comparative methods will then be applied to the osteological data to investigate the evolution of adaptations to locomotion within the Perissodactyla, with a focus on equids (horses).

Researcher(s)

• Promoter: Aerts Peter
• Co-promoter: Nauwelaerts Sandra
• Fellow: Maclaren Jamie

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

The fossil horse sequence is a popular example of a phylogenetic pattern resulting from the evolutionary process. However, the seemingly transitional stages are actually derived from a scattered sampling of horse fossils within the multi-branched horse evolutionary tree. The current hypothesis is that the reduction in the number of digits was necessary for the cursorial lifestyle of today's horses. Lengthening of the distal segments and toe-tip running increased the stride length and thus the speed with which the animal can move. However, to avoid the increase in cost of swinging the heavier limbs, the digital number was reduced. Reinforcement of the middle toe might have also led to an improvement of the stability. The drawback to the reduction lies in loss in versatility and a decreased ability to run on compliant substrates. This project proposes to perform detailed comparative research on horses and their extant relatives. By studying donkeys, zebras, horses and the closely related rhinoceros and tapir, we will detect evolutionary patterns within this group. By studying how the animals move combined with a detailed study of the limb anatomy of the same species, we aim at providing insights in the mechanisms behind the reduction in digital number. The limb movements of the animals will be studied using traditional gait analyses techniques. Video material will be obtained synchronized with ground reaction forces and pressure data under the hooves. This information can be combined with inertial information in a calculation technique called inverse dynamics that will yield the net joint moments and power profiles over time. These profiles can be regarded as indications for motor control patterns. This will allow us to compare motor control patterns between the different species. These gait analysis experiments will be done in collaboration with European zoos. Detailed anatomical descriptions of the joint surfaces and segment proportions will be used to obtain measures for range of motion and joint center locations. These will be compared between species and will create a basis for assessing range of motion in extinct species. These descriptions will be based on 3D scans of osteological samples obtained from museum material. Models of trait evolution will be used to discern how limb skeletal morphology and motor control patterns have evolved in perissodactyls. This work will then form the basis for future work on extinct species of the Perissodactyli.

Researcher(s)

• Promoter: Aerts Peter
• Co-promoter: Nauwelaerts Sandra
• Fellow: Maclaren Jamie

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

This project proposes to perform detailed research on the domestic horse to obtain a simplified protocol that can be used to study the way horses and their relatives move. By studying donkeys, zebras, horses and the closely related rhinoceros and tapir, we will detect evolutionary patterns within this group that we hope to extrapolate to extinct species. By using virtual models of the anatomy of the extinct species, based on museum material, we aim at bringing these species to life and to deduce how they moved about in their environment. By doing so, we will be able to test whether the current members of Equus were better equipped to survive by being able to run faster or more efficiently.

Researcher(s)

• Promoter: Aerts Peter
• Fellow: Nauwelaerts Sandra

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

The overall objective of the proposed research is to define biomechanical control of forelimb movement through musculoskeletal modeling combined with empirical gait tests. Our hypotheses are: (1) the tendons, working passively to control the distal joints of the forelimbs, are stretched more when limb loads are increased; (2) overstretching can be prevented in actively controlled joints via increased muscle force; (3) joint reaction forces (and torques) increase in reaction to load increase; and (4) joint reaction forces (and torques) change direction as loads increase.

Researcher(s)

• Promoter: Aerts Peter
• Fellow: Nauwelaerts Sandra

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

Several major radiations of amphibians have evolved from terrestrial ancestors. Some lineages have further developed the terrestrial design while others have derived an aquatic habit. Among frogs, constraints imposed by ancestral traits have significantly affected the evolution of locomotor mode: almost every frog group has evolved very specialised morphological adaptations for a saltatory (jumping) locomotion. Despite the apparent conflicting demands of jumping and swimming in frogs, hypotheses concerning the energetic trade-offs of these locomotor modes have never been explored. For example, swimming can be considered to be a costly activity because of the intermittent nature of this mode. However, slowly swimming frogs frequently maintain a continuous motion, which according to theory should reduce these costs. In short, the main purpose of this study is to quantify energetic costs of swimming and determine the mechanical differences between jumping and swimming in a model species of frog (Rana esculenta). These data will provide important insights into the origin of a possible trade-off between swimming and jumping in anurans.

Researcher(s)

• Promoter: Aerts Peter
• Fellow: Nauwelaerts Sandra

Research team(s)

• Functional Morphology

Project type(s)

• Research Project

Abstract

Several major radiations of amphibians have evolved from terrestrial ancestors. Some lineages have further developed the terrestrial design while others have derived an aquatic habit. Among frogs, constraints imposed by ancestral traits have significantly affected the evolution of locomotor mode: almost every frog group has evolved very specialised morphological adaptations for a saltatory (jumping) locomotion. Despite the apparent conflicting demands of jumping and swimming in frogs, hypotheses concerning the energetic trade-offs of these locomotor modes have never been explored. For example, swimming can be considered to be a costly activity because of the intermittent nature of this mode. However, slowly swimming frogs frequently maintain a continuous motion, which according to theory should reduce these costs. In short, the main purpose of this study is to quantify energetic costs of swimming and determine the mechanical differences between jumping and swimming in a model species of frog (Rana esculenta). These data will provide important insights into the origin of a possible trade-off between swimming and jumping in anurans.

Researcher(s)

• Promoter: Aerts Peter
• Fellow: Nauwelaerts Sandra

Research team(s)

Project type(s)

• Research Project

Abstract

Several major radiations of amphibians have evolved from terrestrial ancestors. Some lineages have further developed the terrestrial design while others have derived an aquatic habit. Among frogs, constraints imposed by ancestral traits have significantly affected the evolution of locomotor mode: almost every frog group has evolved very specialised morphological adaptations for a saltatory (jumping) locomotion. Despite the apparent conflicting demands of jumping and swimming in frogs, hypotheses concerning the energetic trade-offs of these locomotor modes have never been explored. For example, swimming can be considered to be a costly activity because of the intermittent nature of this mode. However, slowly swimming frogs frequently maintain a continuous motion, which according to theory should reduce these costs. In short, the main purpose of this study is to quantify energetic costs of swimming and determine the mechanical differences between jumping and swimming in a model species of frog (Rana esculenta). These data will provide important insights into the origin of a possible trade-off between swimming and jumping in anurans.

Researcher(s)

• Promoter: Aerts Peter
• Fellow: Nauwelaerts Sandra

Research team(s)

Project type(s)

• Research Project