Feeding Biomechanics and Dietary Ecology of Paranthropus boisei

The Feeding Biomechanics and Dietary Ecology of Paranthropus boisei

Authors:

Smith et al

Abstract:

The African Plio-Pleistocene hominins known as australopiths evolved derived craniodental features frequently interpreted as adaptations for feeding on either hard, or compliant/tough foods. Among australopiths, Paranthropus boisei is the most robust form, exhibiting traits traditionally hypothesized to produce high bite forces efficiently and strengthen the face against feeding stresses. However, recent mechanical analyses imply that P. boisei may not have been an efficient producer of bite force and that robust morphology in primates is not necessarily strong. Here we use an engineering method, finite element analysis, to show that the facial skeleton of P. boisei is structurally strong, exhibits a strain pattern different from that in chimpanzees (Pan troglodytes) and Australopithecus africanus, and efficiently produces high bite force. It has been suggested that P. boisei consumed a diet of compliant/tough foods like grass blades and sedge pith. However, the blunt occlusal topography of this and other species suggests that australopiths are adapted to consume hard foods, perhaps including grass and sedge seeds. A consideration of evolutionary trends in morphology relating to feeding mechanics suggests that food processing behaviors in gracile australopiths evidently were disrupted by environmental change, perhaps contributing to the eventual evolution of Homo and Paranthropus.

Evolution Has Stopped?! Agriculture's Impact Over 6150 Years on Lower Limb Skeletal Biomechanics

Lower limb skeletal biomechanics track long-term decline in mobility across ∼6150 years of agriculture in Central Europe

Authors:

Macintosh et al

Abstract:

Central Europe is a region with a rich agricultural history that dates back to the emergence of the first Neolithic cultures here during the second part of the 6th millennium BC. The effects of prolonged cultural change on the skeletal morphology of agricultural populations in this region have not yet been fully reported. This study investigates diachronic trends in lower limb cross-sectional geometry among preindustrial Central Europeans spanning over 6000 years from the initial spread of agriculture in the region (∼5300 cal BC) to the Early Medieval (∼850 AD). Midshaft diaphyseal cross-sectional geometric (CSG) properties were derived from 443 three-dimensional laser scans of femora and tibiae. Results documented temporal change that was particularly pronounced in the tibia relative to the femur, indicative of declining compressional strength (males), bending and torsional rigidity (males), and increasingly more circular cross-sections (both sexes). When examined chronologically by cemetery, a major shift towards lower tibial rigidity was identified in the Late Bronze Age among males, after which time sexual dimorphism also declined. Regional variation in tibial rigidity was identified among males, being consistently low in males from modern-day Vojvodina (Serbia) relative to contemporaneous males elsewhere in Central Europe. In contrast, female temporal trends by cemetery were indicative of progressive but gradual declines in tibial loading. Results report systematic change in lower limb cross-sectional geometry among preindustrial Central European agriculturalists that are likely indicative of declining terrestrial mobility through 6000+ years of cultural change in the region.

Was Norian Triassic Sauropodomorph Unaysaurus tolentinoi Quadrapedal or Bipdeal?

Functional and biomechanic aspects of the scapular girdle and forelimbs of Unaysaurus tolentinoi Leal et al., 2004 (Saurischia: Sauropodomorpha)

Authors:

Vargas-Peixoto et al

Abstract:

This study presents evidence about the biomechanics and forelimbs functionality of the basal sauropodomorph Unaysaurus tolentinoi (upper portion of the SM2 sequence, Santa Maria Supersequence, Upper Triassic from southern Brazil). Maximum and minimum motion angles were inferred in the joints, disregarding the presence and/or thickness of cartilage. Furthermore, processes and external structures of the bones were analyzed in attributing the functionality of forelimbs. Unaysaurus tolentinoi had well-developed grapple ability. However, the preserved elements and their osteological features are not conclusive about strictly bipedalism or quadrupedalism in U. tolentinoi.

Sauropod Niche Partitioning in the Late Jurassic Morrison Formation

How the largest animals to have ever walked the Earth fed, and how this allowed them to live alongside one another in prehistoric ecosystems is the subject of new research from the University of Bristol and the Natural History Museum, London.

The sauropods – large, long-necked plant-eating dinosaurs such as Diplodocus and Brachiosaurus – dominated the land between 210 and 65 million years ago. They were the largest land animals of all time, with the biggest weighing 80 tonnes (more than 11 elephants) and would have needed vast amounts of food.

Despite this, multiple sauropod species often lived alongside each other. The most notable example is the community of the Late Jurassic Morrison Formation, a distinctive sequence of sedimentary rock in the western United States from which over 10 species of sauropod are known.

How so many giant herbivores could have coexisted has long been a mystery: even the highly diverse faunas seen in modern Africa only support one truly gigantic species, the elephant. This is made even more puzzling by the harsh, semi-arid environment of the Morrison Formation during the Jurassic, which would have limited plant growth.

A study conducted by David Button, a PhD student in Bristol's School of Earth Sciences and the Natural History Museum, and colleagues used a novel combination of approaches to investigate this problem.

Although sauropods were gigantic, their heads were comparatively very small and so how they ingested enough food has puzzled many scientists. The researchers focussed on the skull and jaws of sauropods, using a variety of biomechanical techniques to investigate how they functioned and what this would mean for sauropod ecology.

Using CT scans, the researchers digitally reconstructed the skulls of the sauropods Camarasaurus and Diplodocus, along with the jaw and neck muscles of both species from the traces left on the bones where these muscles were attached in life. These two species are very common in the Morrison Formation, and are known to have widely co-existed. From this data, a biomechanical computer model of the skull of Camarasaurus was built using Finite Element Analysis (FEA), a modelling technique often employed in engineering and design to calculate stress and strain distribution in complex shapes. This model was then compared to a pre-existing model of Diplodocus in order to investigate how the dinosaurs fed.

David Button said: "Our results show that although neither could chew, the skulls of both dinosaurs were sophisticated cropping tools. Camarasaurus had a robust skull and strong bite, which would have allowed it to feed on tough leaves and branches. Meanwhile, the weaker bite and more delicate skull of Diplodocus would have restricted it to softer foods like ferns. However, Diplodocus could also have used its strong neck muscles to help it detach plant material through movements of the head. This indicates differences in diet between the two dinosaurs, which would have allowed them to coexist."

The researchers also used a series of biomechanical measurements from other sauropod species to calculate the functional disparity in their skulls and jaws and found that other Morrison Formation sauropods were also highly varied in feeding adaptations, suggesting different diets.

Co-author, Professor Emily Rayfield of the University of Bristol said: "In modern animal communities differences in diet such as this – termed 'dietary niche partitioning' – allow multiple similar species to coexist by reducing competition for food. Although, dietary niche partitioning has been suspected between Morrison Formation sauropods based on their structural features and patterns of tooth-wear, this is the first study to provide strong, numerical, biomechanical evidence for its presence in this fossil community."

link.

paper link.

Modeling the Feeding Biomechanics of a Kimmridgian Jurassic Pliosaur

Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia: Sauropterygia) from Weymouth Bay, Dorset, UK

Authors:

Foffa et al

Abstract:

Pliosaurs were among the largest predators in Mesozoic seas, and yet their functional anatomy and feeding biomechanics are poorly understood. A new, well-preserved pliosaur from the Kimmeridgian of Weymouth Bay (UK) revealed cranial adaptations related to feeding. Digital modelling of computed tomography scans allowed reconstruction of missing, distorted regions of the skull and of the adductor musculature, which indicated high bite forces. Size-corrected beam theory modelling showed that the snout was poorly optimised against bending and torsional stresses compared with other aquatic and terrestrial predators, suggesting that pliosaurs did not twist or shake their prey during feeding and that seizing was better performed with post-symphyseal bites. Finite element analysis identified biting-induced stress patterns in both the rostrum and lower jaws, highlighting weak areas in the rostral maxillary-premaxillary contact and the caudal mandibular symphysis. A comparatively weak skull coupled with musculature that was able to produce high forces, is explained as a trade-off between agility, hydrodynamics and strength. In the Kimmeridgian ecosystem, we conclude that Late Jurassic pliosaurs were generalist predators at the top of the food chain, able to prey on reptiles and fishes up to half their own length.

Human Feet Are Less Unique Than Previously Thought?

Research at the University of Liverpool has shown that the mechanisms of the human foot are not as unique as originally thought and have much more in common with the flexible feet of other great apes.

Current understanding of the evolution of human walking is based on research from the 1930s, which proposes that human feet function very differently to those of other apes, due to the development of arches in the mid-foot region and the supposed rigidity of that on the outside edge of the foot.

In a study of more than 25,000 human steps made on a pressure-sensitive treadmill at the University's Gait Laboratory, scientists at Liverpool have shown that despite having abandoned life in the trees long ago, our feet have retained a surprising amount of flexibility, the type seen in the feet of other great apes, such as orang-utans and chimpanzees, that have remained largely tree-dwelling.

Professor Robin Crompton, from the University's Institute of Ageing and Chronic Disease, explains: "It has long been assumed that because we possess lateral and medial arches in our feet - the lateral one supposedly being rigid and supported in bone -, that our feet differ markedly to those of our nearest relatives, whose mid-foot is fully flexible and makes regular ground contact.

"This supposed 'uniqueness', however, has never been quantitatively tested. We found that the range of pressures exerted under the human mid-foot, and thus the internal mechanisms that drive them, were highly variable, so much so that they actually overlapped with those made by the great apes."

It has previously been thought that humans who make contact with the ground with the mid-foot region are primarily those that suffer from diabetes or arthritis, both of which can impact on the structure of the feet. Research showed, however, that two thirds of normal healthy subjects produced some footfalls where the mid-foot touches the ground, with no indication that this is other than an aspect of normal healthy walking.

Dr Karl Bates, from the University's Institute of Ageing and Chronic Disease, said: "Our ancestors probably first developed flexibility in their feet when they were primarily tree-dwelling, and moving on bendy branches, but as time passed and we became more and more ground-dwelling animals, some new features evolved to enable us to move quickly on the ground.

"Our limbs, however, did not adapt to life on the ground anywhere near as much as those of other ground-dwelling animals such as horses, hares and dogs. Our tests showed that our feet are not as stiff as originally thought and actually form part of a continuum of variation with those of other great apes.

"We hypothesise that despite becoming nearly exclusively ground dwelling we have retained flexibility in the feet to allow us to cope effectively with the differences in hard and soft ground surfaces which we encounter in long distance walking and running. The next part of our study will be testing this theory, which could offer a reason why humans can outrun a horse, for example, over long distances on irregular terrain."

Biomechanics of the Evolution of Walking...Fins to Legs

Why did animals with limbs win the race to invade land over those with fins? A new study comparing the forces acting on fins of mudskipper fish and on the forelimbs of tiger salamanders can now be used to analyze early fossils that spanned the water-to-land transition in tetrapod evolution, and further understand their capability to move on land.

Research conducted by Sandy Kawano and Richard Blob at Clemson University compared terrestrial locomotion in tiger salamanders and mudskipper fish, which have similar characteristics to early tetrapod ancestors.

The researchers filmed these organisms as they walked over a force platform which measures forces like a bathroom scale but separates them into 3 directions (upward, fore-aft, and side-to-side). They compared the forces experienced by the pectoral fins of the mudskipper fishes to the forelimbs and hind limbs of walking tiger salamanders. The results showed that that mudskippers' pectoral fins experience more medial forces than the limbs of salamanders, and that the forelimbs could have a played a similar weight-bearing role as the hind limbs.

Biomechanically Comparing Therian Sabretooths

Comparative Biomechanical Modeling of Metatherian and Placental Saber-Tooths: A Different Kind of Bite for an Extreme Pouched Predator

Authors:

1. Stephen Wroe (a,b)
2. Uphar Chamoli (b,c)
3. William C. H. Parr (b)
4. Philip Clausen (a)
5. Ryan Ridgely (d)
6. Lawrence Witmer (d)

Affiliations:

a. School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia

b. School of Engineering, University of Newcastle, Callaghan, NSW, Australia

c. St. George Clinical School, University of New South Wales, Sydney, NSW, Australia

d. Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America

Abstract:

Questions surrounding the dramatic morphology of saber-tooths, and the presumably deadly purpose to which it was put, have long excited scholarly and popular attention. Among saber-toothed species, the iconic North American placental, Smilodon fatalis, and the bizarre South American sparassodont, Thylacosmilus atrox, represent extreme forms commonly forwarded as examples of convergent evolution. For S. fatalis, some consensus has been reached on the question of killing behaviour, with most researchers accepting the canine-shear bite hypothesis, wherein both head-depressing and jaw closing musculatures played a role in delivery of the fatal bite. However, whether, or to what degree, T. atrox may have applied a similar approach remains an open question. Here we apply a three-dimensional computational approach to examine convergence in mechanical performance between the two species. We find that, in many respects, the placental S. fatalis (a true felid) was more similar to the metatherian T. atrox than to a conical-toothed cat. In modeling of both saber-tooths we found that jaw-adductor-driven bite forces were low, but that simulations invoking neck musculature revealed less cranio-mandibular stress than in a conical-toothed cat. However, our study also revealed differences between the two saber-tooths likely reflected in the modus operandi of the kill. Jaw-adductor-driven bite forces were extremely weak in T. atrox, and its skull was even better-adapted to resist stress induced by head-depressors. Considered together with the fact that the center of the arc described by the canines was closer to the jaw-joint in Smilodon, our results are consistent with both jaw-closing and neck musculature playing a role in prey dispatch for the placental, as has been previously suggested. However, for T. atrox, we conclude that the jaw-adductors probably played no major part in the killing bite. We propose that the metatherian presents a more complete commitment to the already extreme saber-tooth ‘lifestyle’.

Earliest Terrestrial Tetrapods Had A Weak Bite

What had the legs of a ‘gator and the jaws of a fish? Why, the earliest land animals. Because a new study shows that animals evolved weight-bearing limbs long before they had the chompers to really take advantage of a terrestrial diet. The research is in the journal Integrative and Comparative Biology. [Philip S. L. Anderson, Matt Friedman and Marcello Ruta, Late to the Table: Diversification of Tetrapod Mandibular Biomechanics Lagged Behind the Evolution of Terrestriality]

Scientists had suspected that the first four-legged creatures to haul their carcasses out of the ocean didn’t belly up to the salad bar straight away. But they lacked definitive proof.

Now, researchers have carefully examined the fossilized faces of 89 beasties that lived on land and sea some 300 to 400 million years ago. They probed the jaws for a range of biomechanical features, such as how much force they could give to their bite. The result: seems it took tens of millions of years after setting foot on land to come up with a mouth that could munch on the greenery.

Biomechanical Assessment of Evolutionary Changes in the Lepidosaurian Skull

1. Mehran Moazena,1,
2. Neil Curtisa,
3. Paul O'Higginsb,
4. Susan E. Evansc and
5. Michael J. Fagana

-Author Affiliations

1.
aDepartment of Engineering, University of Hull, Hull HU6 7RX, United Kingdom;
2.
bThe Hull York Medical School, University of York, York YO10 5DD, United Kingdom; and
3.
cResearch Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom

1.

Edited by R. McNeill Alexander, University of Leeds, Leeds, United Kingdom, and accepted by the Editorial Board March 24, 2009 (received for review December 23, 2008)

Abstract

The lepidosaurian skull has long been of interest to functional morphologists and evolutionary biologists. Patterns of bone loss and gain, particularly in relation to bars and fenestrae, have led to a variety of hypotheses concerning skull use and kinesis. Of these, one of the most enduring relates to the absence of the lower temporal bar in squamates and the acquisition of streptostyly. We performed a series of computer modeling studies on the skull of Uromastyx hardwickii, an akinetic herbivorous lizard. Multibody dynamic analysis (MDA) was conducted to predict the forces acting on the skull, and the results were transferred to a finite element analysis (FEA) to estimate the pattern of stress distribution. In the FEA, we applied the MDA result to a series of models based on the Uromastyx skull to represent different skull configurations within past and present members of the Lepidosauria. In this comparative study, we found that streptostyly can reduce the joint forces acting on the skull, but loss of the bony attachment between the quadrate and pterygoid decreases skull robusticity. Development of a lower temporal bar apparently provided additional support for an immobile quadrate that could become highly stressed during forceful biting.

* biomechanics
* Lepidosauria
* lower temporal bar
* streptostyly

Footnotes

* 1To whom correspondence should be addressed. E-mail: m.moazen@hull.ac.uk

Busy assessing what GPFS can do under our new configuration, so no time to comment.