New ideas: Mixing FEA and histology in fossil taxa

Finite Element Analysis (FEA) is a useful method for understanding form and function. However, modelling of fossil taxa invariably involves assumptions as a result of preservation-induced loss of information in the fossil record. In this new work, to test how well results from FEA correlate to cranial mechanics predicted from bone structure, we used the well-known temnospondyl Metoposaurus krasiejowensis as a model to compare results for the first time from a:

• A Structural Static Analysis to evaluate the biomechanical behaviour during biting was performed using Finite Element Analysis. This analysis was previously published in Fortuny et al. 2017
• A histological study of cranial bones of Metoposaurus krasiejowensis that was also performed in Gruntmejer et al. 2016

The results obtained in this mixed research showed that an histological analysis of skull microstructure mostly confirms the models created by FEA. Thus, results predicting cranial mechanical behaviour using both methods to understand the feeding strategy of Metoposaurus. Metoposaurus appeared to have been an aquatic animal that exhibited a generalist feeding behaviour.

Read more in : Konietzko-Meier D, Gruntmejer K, Marcé-Nogué J, Bodzioch A, Fortuny J. (2018) Merging cranial histology and 3D-computational biomechanics: a review of the feeding ecology of a Late Triassic temnospondyl amphibian. PeerJ 6:e4426

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New methods drive to new ideas

Recently we published the paper “The intervals method: a new approach to analyse finite element outputs using multivariate statistics” in PeerJ . This paper is a continuation of our previous works with armadillos jaws (such as Marcé-Nogué et sal. 2016) where we are developing new methods to help the interpretation of FEA results. In this paper, we propose a new method, named the intervals’ method, to analyse data from finite element models in a comparative multivariate framework. As a case study, several armadillo mandibles are analysed, showing that the proposed method is useful to distinguish and characterise biomechanical differences related to diet/ecomorphology.

The intervals’ method consists of generating a set of variables, each one defined by an interval of stress values. Each variable is expressed as a percentage of the area of the mandible occupied by those stress values. Afterwards these newly generated variables can be analysed using multivariate methods.Applying this novel method to the biological case study of whether armadillo mandibles differ according to dietary groups, we show that the intervals’ method is a powerful tool to characterize biomechanical performance and how this relates to different diets. This allows us to positively discriminate between specialist and generalist species and, moreover, something that it is very important when working with FEA: We show that the proposed approach is a useful methodology not affected by the characteristics of the finite element mesh.

Marcé-Nogué J, De Esteban-Trivigno S, Püschel TA, Fortuny J. The intervals method: a new approach to analyse finite element outputs using multivariate statistics. PeerJ 2017;5:e3793. More info: https://peerj.com/articles/3793/

 

Parametric analysis in a FEA model to understanding basal urodeles

In vertebrate palaeontology, some previous works joined a Parametric Analysis and FEA to test the behaviour and sensitivity of different parameters such as the material properties of the biological tissue, the homogeneity or heterogeneity of the bone, the sutures, or the influence of the loads applied. Previously we used thiks type of analysis to test how the variation of the original geometry affects the biomechanical performance in the eyes of an Edingerella madagascariensis to study the implications of orbit Position and size diversity of early amphibians: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131320

Now, Our new joined paper “Cranial biomechanics in basal urodeles: the Siberian salamander (Salamandrella keyserlingii) and its evolutionary and developmental implications” with the researchers Zupeng Zhou, Josep Fortuny & Pavel P. Skutschas has been published in Scientific Reports. The work is analysing a 3D cranial biomechanics of the adult Salamandrella keyserlingii  under different tissue properties and ossification sequences of the cranial skeleton to unravel that:

1. Mechanical properties of tissues (as bone, cartilage or connective tissue) imply a consensus between the stiffness required to perform a function versus the fixation (and displacement) required with the surrounding skeletal elements.
2. Changes on the ossification pattern, producing fontanelles as a result of bone loss or failure to ossify, represent a trend toward simplification potentially helping to distribute stress through the skull, but may also imply a major destabilization of the skull.
3. Bone loss may be originated due to biomechanical optimization and potential reduction of developmental costs.
4. Hynobiids are excellent models for biomechanical reconstruction of extinct early urodeles.

Zhou, Z. et al. “Cranial biomechanics in basal urodeles: the Siberian salamander (Salamandrella keyserlingii) and its evolutionary and developmental implications”. Scientific Reports. 2017. More info at: https://www.nature.com/articles/s41598-017-10553-1

 

 

Hard food for stiffer Jaw

I recently published in Scientific Reports a new paper entitled “A biomechanical approach to understand the ecomorphological relationship between primate mandibles and diet” which deals with the fact that in primates, hard food eaters have stiffer mandibles when compared to those that rely on softer diets. This is a research that I did with my colleagues Thomas Püschel, from The University of Manchester, and Thomas Kaiser from the University of Hamburg.

Altought the relationship between primate mandibular form and diet has been previously analysed by applying a wide array of techniques and approaches, now we proposed a new approach using FEA. Nonetheless, most of these previous studies compared few species and/or infrequently aimed to elucidate function based on an explicit biomechanical framework. In this study, we generated and analysed 31 Finite Element planar models of different primate jaws under different loading scenarios (incisive, canine, premolar and molar bites) to test the hypothesis that there are significant differences in mandibular biomechanical performance due to food categories and/or food hardness.

To demonstrate that the stress distribution is different depending on the diet we used the new methodology proposed by Marcé-Nogué et al. 2016 in “Accounting for differences in element size and homogeneity when comparing Finite Element models: Armadillos as a case study” which facilitates the comprehension and helps us to quantify each FEA result to, for example, do an ancestral reconstruction.

The results obtained in this paper are highly relevant because they show that there is a strong association between mandibular biomechanical performance, mandibular form, food hardness and diet categories and that these associations can be studied using biomechanical techniques rather than focusing solely on morphology.

+ More information in: https://www.nature.com/articles/s41598-017-08161-0

 

 

Going to the EAVP not only as an attendant

The first week of August I attended the 15th Annual Meeting of the Association of European Vertebrate Palaeontologists (EAVP) in Munich (Germany). I presented my recent join work about biomechanics of the platyrrhine talus with my colleague Thomas Püschel (University of Manchester) where we were studied the biomechanical behaviour of the talus in 40 extant platyrrhine species to test if it was possible to distinguish locomotor behaviours (i.e. suspension, quadrupedalism and leaping). Then, we analysed ten different Miocene fossil samples to compare their stress results with the extant data to infer their possible locomotor behaviours.

But, this was not all my contribution in the conference. Moreover, I was one of the co-organizers of the symposyum “Ecomorphology and functional anatomy in vertebrate palaeontology” together with my colleagues of the Institut Català de Paleontologia (ICP): Josep Fortuny and Soledad De Esteban-Trivigno. This symposium intended to be the meeting point for all functional anatomists and evolutionary ecologists interested in vertebrate palaeontology with more than 20 talks. My talk was included in this symposyum as well the talk of my colleague Josep Fortuny about our join work using Finite Element Analysis (FEA) in current and extanct amphibians and reptiles.

The first day of the conference I was also teaching a four-hours workshop organized by Transmitting Science: “Introduction to Finite Element Analysis”. The workshop introduced vertebrate paleontologists to FEA, which is a great tool to approach problems in biomechanics of living and extinct organisms using digital models.

My works there:

• Marcé-Nogué, J. [et al.] “Inferring locomotor behaviours in Miocene New World Monkeys: A comparative Finite Element Analysis of the platyrrhine talus” 15th EAVP. Munich (Germany). 2017
• Fortuny, J. [et al.] “3D Computational Biomechanics Meets Amphibians: Ecomorphology And Evolutionary Implications”. 15th EAVP. Munich (Germany). 2017

And, of course, I took some days off to visit Munich and the most known place in Bayern: The castle of Neuschwanstein!

Attending a conference in New Orleans

This April I attended the American Association of Physical Anthropologists Meeting in New Orleans (USA) where I presented some of my last works in primates morphology and biomechanics and I had the ooportunity to be in the Science March. The works I or my colleagues presented were:

• Marcé-Nogué, J. et al. “Hard food for stiffer jaws: A comparative Finite Element Analysis of different primate jaws”.
• Püschel, T.A. et al. “Analyzing the Morpho-functional Consequences of Seed Predation in the Pitheciid lower Jaw using Finite Element Analysis and Geometric Morphometrics”.
• Pina, M. et al. “Patellar response to knee flexion in the Miocene primates Epipliopithecus vindobonensis and Pierolapithecus catalaunicus”. 

The works presented there are based in the idea that biomechanics and forces are demonstrated to be crucial to understand better the biomechanics of primates correlating with diet, locomotion and evolution depending if we are studying cranial bones or post-cranial. The models in each work were studied using Finite Element Analysis with the background idea of developing new methods to shed light in all of this. The meeting was great, I could attend a lot of talks to learn what other researchers are doing to learn new methods and have new ideas. I could also met old friends, know what they are doing, and I made news, which is always another good reason to attend conferences. And I had few time (but enough!) to visit the city and the surroundings, to hear good New Orleans music and being part of the Science March of the 22th.

 

Feeding biomechanics of Late Triassic Metoposaurids

A new paper has been published in Journal of Anatomy studying the paleoecology of extinct amphibian Temnospondyli. The study aims to expand upon the paleoecological interpretations of these animals using 3D Finite Element Analyses (FEA) because the paleoecology of metoposaurids is controversial; they have been historically considered passive, bottom-dwelling animals, waiting for prey on the bottom of rivers and lakes or they have been suggested to be active mid-water feeders.

Skulls from two taxa, Metoposaurus krasiejowensis, a gigantic taxon from Europe, and Apachesaurus gregorii, a non-gigantic taxon from North America, were analyzed under different biomechanical scenarios. Both 3D models of the skulls were scaled to allow comparisons between them and reveal that the general stress distribution pattern found in both taxa is clearly similar in all scenarios. In light of our results, both previous hypotheses about the paleoecology of these animals can be partly merged: metoposaurids probably were ambush and active predators, but not the top predators of these aquatic environments. To demonstrate that the stress distribution is similar in both scenarios we used the new methodology proposed by Marcé-Nogué et al. 2016 in “Accounting for differences in element size and homogeneity when comparing Finite Element models: Armadillos as a case study” which facilitates the comprehension.

The FEA results demonstrate that they were particularly efficient at bilateral biting, and together with their characteristically anteropositioned orbits, optimal for an ambush strategy. Nonetheless, the results also show that these animals were capable of lateral strikes of the head, suggesting active hunting of prey.

Regarding the important skull size differences between the taxa analyzed, our results suggest that the size reduction in the North American taxon could be related to drastic environmental changes or the increase of competitors. The size reduction might have helped them expand into new ecological niches, but they likely remained fully aquatic, as are all other metoposaurids.

+ more info: http://onlinelibrary.wiley.com/wol1/doi/10.1111/joa.12605/abstract