DOCSLIB.ORG

Does Osteoderm Growth Follow Energy Minimization Principles?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Does Osteoderm Growth Follow Energy Minimization Principles? JOURNAL OF MORPHOLOGY 00:00–00 (2014) Does Osteoderm Growth Follow Energy Minimization Principles? Sebastian Sensale,1,2* Washington Jones,1 and R. Ernesto Blanco3 1Nucleo de Biomecanica, Espacio Interdiscipinario, Universidad de la Republica, Montevideo 11200, Uruguay 2Instituto de Fısica, Facultad de Ingenierıa, Universidad de la Republica, Montevideo 11300, Uruguay 3Instituto de Fısica, Facultad de Ciencias, Universidad de la Republica, Montevideo 11400, Uruguay ABSTRACT Although the growth and development of tion of contact surfaces among genetically deter- tissues and organs of extinct species cannot be directly mined elements (as in epithelia; Gibson et al., observed, their fossils can record and preserve evidence 2006; Farhadifar et al., 2007; Lecuit and Lenne, of these mechanisms. It is generally accepted that bone 2007). architecture is the result of genetically based biome- It is important to note that there is always chanical constraints, but what about osteoderms? In this article, the influence of physical constraints on cra- interplay between physically and genetically con- nial osteoderms growth is assessed. Comparisons trolled parameters (Padian et al., 2001; Castanet, among lepidosaurs, synapsids, and archosaurs are per- 2006). For example, in the cracking of a material formed; according to these analyses, lepidosaur osteo- layer, composition and thickness of the skin affect derms growth is predicted to be less energy demanding the mechanism (Milinkovitch et al., 2013); in RDM than that of synapsids and archosaurs. Obtained models treat developmental steps as if they were results also show that, from an energetic viewpoint, isolated from the rest of the organism, leaving ankylosaurid osteoderms growth resembles more that aside factors such as spatial and temporal location of mammals than the one of reptilians, adding evidence (Koch and Meinhardt, 1994); and, under closer to debate whether dinosaurs were hot or cold blooded. inspection, in energy minimization models the sys- J. Morphol. 000:000–000, 2014. VC 2014 Wiley Periodi- cals, Inc. tems are not perfectly regular and are often some- what disordered, which reflects the limit of a tight KEY WORDS: osteoderms; ankylosaurs; biomechanics; genetic control (Lecuit and Lenne, 2007). Also, periodic patterns these are all theoretical models and, as such, they tend to omit many features, such as the possible influence of electric or thermic properties, in order INTRODUCTION to focus on the influence of certain parameters. Periodic Patterning Modeling Polygonal Pattern Formation Mechanisms The growth of feathers, scales, hairs, and teeth, among other epidermal tissues, has long fasci- Due to their surfactants, biological membranes nated biologists. The presence of patterns in bio- behave like elastic membranes (Lautrup, 2004) logical tissues demonstrates how extremely and cell-surface mechanics are comparable to the organized developmental processes are to under- physics of foam formation (Taylor, 1976). Although stand how these patterns arise, the integration of this idea has been around for some time (Thomp- multiple disciplines (like physics and developmen- son, 1917), only recently 2D foam models have tal biology) seems mandatory. been applied to explain the development of Periodic patterning has emerged early in evolu- tion to allow functional redundancy and pheno- typic variation (Chuong and Richardson, 2009). In Additional Supporting Information may be found in the online ver- birds and mammals, reaction-diffusion mecha- sion of this article. nisms (RDM) generate the periodicity of structures Contract grant sponsor: Programa de Desarrollo de Ciencias such as hairs and feathers (Chuong et al., 2013), Basicas (PEDECIBA) and Agencia Nacional de Investigacion e but their relation with other tissues that present Innovacion (ANII).. periodic, repetitive patterns—such as the head scales of crocodiles—is not that direct (Milinko- *Correspondence to: S. Sensale; Instituto de Fısica, Facultad de vitch et al., 2013). Three major mechanisms could Ingenierıa, Montevideo 11300, Uruguay. E-mail: ssensale@fing.edu.uy generate polygonal patterns in biological tissues: the cracking of a material layer into adjacent poly- Received 27 August 2013; Revised 16 December 2013; gons (as in crocodile head scales), RDM pattern- Published online 00 Month 2014 in ings of genetically determined developmental units Wiley Online Library (wileyonlinelibrary.com). (as in feathers and hairs), and energy minimiza- DOI 10.1002/jmor.20273 VC 2014 WILEY PERIODICALS, INC. 2 S. SENSALE ET AL. against bulk pressure (P) when the volume (V)of the system is expanded by dV dW52PdV This resistance against expansion shows that the surface has an internal surface tension, which equals the surface energy density when under mechanical equilibrium.Considering a lapse of time where surface tension can be considered as constant, if two similar surfaces are in contact, it may be useful for many purposes to treat them as one by just doubling the surface tension constant. Therefore, problems of energy minimization can be reduced to problems of area minimization (Taylor, 1976). Clusters and energy minimizing (foam) Fig. 1. Cross section of an elementary 3D model of a material- models. If a 2D-structure consisting of many vacuum interface. Note how a molecule in the interface has one missing bond in comparison to a molecule in the interior. surfaces back to back everywhere (Fig. 2A) is con- sidered, minimizing the energy in the surfaces’ biological tissues such as the retina (Hayashi and junctions will involve minimizing their lengths. In Carthew, 2004) and epithelial junctional networks order to achieve this minimization, both the junc- (Farhadifar et al., 2007). Under this framework, tions’ perimeter and the area on each vertex surface tension properties underlie the control of where three or more edges meet must be minimal. tissue organization. The mathematics of elastic Therefore, two problems coexist: one involving a solids is a well-developed subject, and as such it minimal perimeter with free topology, and one can provide useful ideas about real-life processes involving the minimization of the vertices’ area. like the morphogenesis of biological tissues. In The areas surrounding each vertex have been proven to be minimal when three minimal surfa- this section, surface tension will be defined as well as its role in energy minimization. ces meet smoothly at angles of 120 along a curve Consider a simple regular “solid” surrounded by (Taylor, 1976; Graner, 2002), condition that will be vacuum whose molecules are placed in a cubic grid referred to as “triple junctures.” This condition can as in Figure 1, with grid length equal to the molecu- also be seen as the result of the three instantane- lar separation. Each molecule in the interior has six ous equal length-tension force vectors acting at a bonds to its neighbors, while those in the surface node. Basic mathematical properties prove that, have only five; this leads to a free surface energy under this hypothesis, the average surface will which, divided by the molecular area scale, defines have six (when considering the structure as free) what is called “surface energy density.” Because of or fewer sides (when considering the structure as the missing negative binding energy of the surface bordered, because of the defects; Graner et al., of molecules, this quantity is always positive when 2001; Milinkovitch et al., 2013). It is also worth considering the density associated with a liquid or noting that this result does not state that the solid interface against vacuum or gases, guarantee- mean surface will be a regular hexagon, but that ing that such interfaces seek toward the minimal it will be a polygon with six sides. This is also con- area consistent with the other forces that may be at sistent with Von Neumann–Mullins equation (Von play. This is not necessarily true on interfaces Neumann, 1952; Mullins, 1956) between solids and/or liquids, where its sign depends on the relation between the strength of the cohesive forces holding molecules together and the strength of the adhesive forces between the oppos- ing molecules of the interfacing molecules. Increasing the area of an interface with energy density a, a tiny amount dA requires an amount of work equal to the surface energy contained in the extra piece of interface dW 5adA: Note that, except for the sign, this is quite anal- Fig. 2. Scheme of surfaces back to back everywhere (A) lateral ogous to the mechanical work (dW) performed view; (B)dorsalview. Journal of Morphology CRANIAL OSTEODERM GROWTH 3 Ap dS5 ðÞn26 6 which states that, for foams and grain growth, surfaces with more than six sides (n) tend to grow, therefore being forced by their neighbors to shrink, while surfaces with less than six sides tend to disappear, therefore being less stressed by their neighbors. Although many models of minimal perimeter can be applied depending on the geometry (Bleicher, 1987; Morgan, 1994; Hales, 2000; Gra- ner et al., 2001; Cox and Graner, 2003; Cox et al., 2003; Cox, 2006; Cox and Shuttleworth, 2006; Cox and Flikkema, 2010; Cox et al., 2013a,b), most of them work under theoretical hypotheses that do not seem applicable to real-life systems. Neverthe- less, it has been demonstrated that the minimal perimeter configuration of a system of N deforma- ble areas with triple junctures is satisfied when the average area ratio of perimeter to square root of area is along the order of 23=2 Ã 31=4 3:7224 (Graner et al., 2001; Cox et al., 2013b). Note that, although this number is not sensitive to the num- ber of sides of an area, this is the same ratio that would be obtained if all the areas were regular hexagons. It is also worth noting that, as the num- ber of areas increases, this average ratio converges to 3.7224; nevertheless, this value is appropriate enough even for a few areas (Cox et al., 2003). Summarizing, a system of deformable surfaces Fig. 3. Crack patterns on a dried mud. Note how chaotic and back to back everywhere that follows minimal irregular these patterns are.
Load more

Recommended publications
  • JVP 26(3) September 2006—ABSTRACTS
    Neoceti Symposium, Saturday 8:45 acid-prepared osteolepiforms Medoevia and Gogonasus has offered strong support for BODY SIZE AND CRYPTIC TROPHIC SEPARATION OF GENERALIZED Jarvik’s interpretation, but Eusthenopteron itself has not been reexamined in detail. PIERCE-FEEDING CETACEANS: THE ROLE OF FEEDING DIVERSITY DUR- Uncertainty has persisted about the relationship between the large endoskeletal “fenestra ING THE RISE OF THE NEOCETI endochoanalis” and the apparently much smaller choana, and about the occlusion of upper ADAM, Peter, Univ. of California, Los Angeles, Los Angeles, CA; JETT, Kristin, Univ. of and lower jaw fangs relative to the choana. California, Davis, Davis, CA; OLSON, Joshua, Univ. of California, Los Angeles, Los A CT scan investigation of a large skull of Eusthenopteron, carried out in collaboration Angeles, CA with University of Texas and Parc de Miguasha, offers an opportunity to image and digital- Marine mammals with homodont dentition and relatively little specialization of the feeding ly “dissect” a complete three-dimensional snout region. We find that a choana is indeed apparatus are often categorized as generalist eaters of squid and fish. However, analyses of present, somewhat narrower but otherwise similar to that described by Jarvik. It does not many modern ecosystems reveal the importance of body size in determining trophic parti- receive the anterior coronoid fang, which bites mesial to the edge of the dermopalatine and tioning and diversity among predators. We established relationships between body sizes of is received by a pit in that bone. The fenestra endochoanalis is partly floored by the vomer extant cetaceans and their prey in order to infer prey size and potential trophic separation of and the dermopalatine, restricting the choana to the lateral part of the fenestra.
    [Show full text]
  • 1931-15701-1-LE Maquetación 1
    AMEGHINIANA 50 (6) Suplemento 2013–RESÚMENES REUNIÓN DE COMUNICACIONES DE LA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA 20 a 22 de Noviembre de 2013 Ciudad de Córdoba, Argentina INSTITUCIÓN ORGANIZADORA AUSPICIAN AMEGHINIANA 50 (6) Suplemento 2013–RESÚMENES COMISIÓN ORGANIZADORA Claudia Tambussi Emilio Vaccari Andrea Sterren Blanca Toro Diego Balseiro Diego Muñoz Emilia Sferco Ezequiel Montoya Facundo Meroi Federico Degrange Juan José Rustán Karen Halpern María José Salas Sandra Gordillo Santiago Druetta Sol Bayer COMITÉ CIENTÍFICO Dr. Guillermo Albanesi (CICTERRA) Dra. Viviana Barreda (MACN) Dr. Juan Luis Benedetto (CICTERRA) Dra. Noelia Carmona (UNRN) Dra. Gabriela Cisterna (UNLaR) Dr. Germán M. Gasparini (MLP) Dra. Sandra Gordillo (CICTERRA) Dr. Pedro Gutierrez (MACN) Dr. Darío Lazo (UBA) Dr. Ricardo Martinez (UNSJ) Dra. María José Salas (CICTERRA) Dr. Leonardo Salgado (UNRN) Dra. Emilia Sferco (CICTERRA) Dra. Andrea Sterren (CICTERRA) Dra. Claudia P. Tambussi (CICTERRA) Dr. Alfredo Zurita (CECOAL) AMEGHINIANA 50 (6) Suplemento 2013–RESÚMENES RESÚMENES CONFERENCIAS EL ANTROPOCENO Y LA HIPÓTESIS DE GAIA ¿NUEVOS DESAFÍOS PARA LA PALEONTOLOGÍA? S. CASADÍO1 1Universidad Nacional de Río Negro, Lobo 516, R8332AKN Roca, Río Negro, Argentina. [email protected] La hipótesis de Gaia propone que a partir de unas condiciones iniciales que hicieron posible el inicio de la vida en el planeta, fue la propia vida la que las modificó. Sin embargo, desde el inicio del Antropoceno la humanidad tiene un papel protagónico en dichas modificaciones, e.g. el aumento del CO2 en la atmósfera. Se estima que para fines de este siglo, se alcanzarían concentraciones de CO2 que el planeta no registró en los últimos 30 Ma. La información para comprender como funcionarían los sistemas terrestres con estos niveles de CO2 está contenida en los registros de períodos cálidos y en las grandes transiciones climáticas del pasado geológico.
    [Show full text]
  • Pleistocene – Cretaceous One-Two Punch
    FOSSIL COLLECTING REPORT September 2008 Daniel A. Woehr and Friends and Family September 1, 2008: Pleistocene – Cretaceous One-Two Punch “It’s the sheriff!” is what I heard when I opened my eyes to blinding lights. It seems that Johnny Law is not used to seeing law abiding grown men sleeping in cars by the roadside. I explained that I was nothing more than a nerdy fossil hunter on a budget and after checking my ID and noting the boat on my roof I suppose he believed me, as did his backup in the second car with headlights in my face. Dawn found me at my second put-in and soon making my way to a distant gravel bar. I wasn’t expecting much but my first find was a worn but very welcome mastodon vertebra. Finds were slow to come but some were rather nice. A good horse tooth, horse tibia, bison astragulus and calcaneum, and a few other things came to hand and put some heft in my catch bag. Still, the ever elusive mammoth tooth evaded me once again. FIG 1: Alligator mississippiensis osteoderm from Site 373 FIGS 2-6: Bison sp. calcaneum above and astragulus below (both ankle bones), 2 more views of same followed by worn Glyptotherium osteoderm next page (Site 373) FIG 7: Unidentified distal radius and distal scapula followed by horse lower molar (Site 373) FIGS 8-9: Worn Mammut americanum (mastodon) vertebra (Site 373) FIGS 10-11: Unidentified proximal rib and vertebrae (Site 373) Switching gears, I began my drive home, learned that the wife and boy wouldn’t be home anytime soon, and opted to drop in once again on some parts of the Corsicana exposure that Weston and I didn’t have time to look over on prior trips.
    [Show full text]
  • Crocodile Farming with Particular Reference to East Africa
    British Herpetological Sot 'co, Bulletin, No. 66, 1999 CROCODILE FARMING WITH PARTICULAR REFERENCE TO EAST AFRICA JOHN E. COOPER, DTVM, FRCPath, FIBiol, FRCVS Faculty of Veterinary Medicine, Sokoine University of Agriculture P.O. Box 3021, Morogoro, Tanzania Contact address in UK: Wildlife Health Services P.O. Box 153, Wellingborough, Northants NN8 2ZA INTRODUCTION The Class Crocodilia consists of the crocodiles, alligators, caimans and gharials. There are twenty-three extant species but, in the past, many more existed (Frye, 1994). Crocodiles are reptiles that are well adapted to life in water. While most are freshwater, one species is partly marine. The anatomy of crocodiles is dominated by their tough integument which, on the dorsum, is protected by plates of osteoderm. Internally, crocodiles have a well developed palate, a four chambered heart and a right aortic arch. All crocodilians are oviparous. In many species the female constructs a nest of decaying vegetable matter and as this decomposes, the temperature rises and assists in incubation. Sex determination in crocodilians is temperature-related. Crocodilians are unusual amongst reptiles in that the nests are guarded by the mother (possibly the father) who also protects the young, often for a considerable period of time. The Nile Crocodile (Crocodyhts nitoticits) is the most widespread of the three species of crocodile that are found in Africa. The Nile Crocodile is biologically similar to other crocodilians. It is an ectothermic vertebrate. The free-living crocodile reaches sexual maturity at between 20 and 35 years of age when the male is 3-3.3 m in length and the female is 2.4-2.8 m (Revol, 1995).
    [Show full text]
  • The Armor of FOSSIL GIANT ARMADILLOS (Pa1npatlzeriidae, Xenartlz Ra, Man1malia) A
    NUMBER40 PEARCE-SELLARDS SERIES The Armor of FOSSIL GIANT ARMADILLOS (Pa1npatlzeriidae, Xenartlz ra, Man1malia) A. GORDON EDMUND JUNE 1985 TEXAS MEMORIAL MUSEUM, UNIVERSITY OF TEXAS AT AUSTIN Pearce-Sellards Series 40 The Armor of FOSSIL GIANT ARMADILLOS (Pampatheriidae, Xenartlzra, Mammalia) A. GORDON EDMUND JUNE 1985 TEXAS MEMORIAL MUSEUM, UNIVERSITY OF TEXAS AT AUSTIN A. Gordon Edmund is Curator of Vertebrate Paleontology at the Royal Ontario Museum, Toronto, and Associate Professor of Geology at the University of Toronto. The Pearce-Sellards Series is an occasional, miscellaneous series of brief reports of Museum and Museum-associated field investigations and other research. All manuscripts are subjected to extramural peer review before being accepted. The series title commemorates the first two directors of Texas Memorial Museum, both now deceased: Dr. J. E. Pearce, Professor of Anthropology, and Dr. E. H. Sellards, Professor of Geology, The University of Texas at Austin. A portion of the Museum's general ope­ rating funds for this fiscal year has been provided by a grant from the Institute of Museum Services, a federal agency that offers general operating support to the nation's museums. © 1985 by Texas Memorial Museum The University of Texas at Austin All rights reserved Printed in the United States of America CONTENTS Abstract .... .............................................. I Sumario .................................................... 1 Acknowledgements . 2 Abbreviations ............................................... 2 Introduction . 3 A General Description of the Armor . 5 Types and Numbers of Osteoderms .... .. ........................ 6 Structure of Osteoderms . 7 Detailed Description of each Area ................................ 8 Conclusions. 19 References ............ .. .............. ............. ....... 19 LIST OF FIGURES Fig. 1. Restoration of Holmesina septentrionalis based on composite material from Florida ......... ...... .... facing 5 Fig.
    [Show full text]
  • Unprovoked Mouth Gaping Behavior in Extant Crocodylia
    Journal of Herpetology, Vol. 54, No. 4, 418–426, 2020 Copyright 2020 Society for the Study of Amphibians and Reptiles Unprovoked Mouth Gaping Behavior in Extant Crocodylia 1,2 3 4 NOAH J. CARL, HEATHER A. STEWART, AND JENNY S. PAUL 1Reptile Department, St. Augustine Alligator Farm Zoological Park, St. Augustine, Florida, 32080, USA 3Department of Biology, McGill University, Montre´al, Que´bec, Canada H3A 1B1 4Greg A. Vital Center for Natural Resources and Conservation, Cleveland State Community College, Cleveland, Tennessee, 37320, USA ABSTRACT.—Unprovoked mouth gaping behavior is ubiquitous throughout 24 extant members of Crocodylia, yet information on gaping Downloaded from http://meridian.allenpress.com/journal-of-herpetology/article-pdf/54/4/418/2696499/i0022-1511-54-4-418.pdf by guest on 25 September 2021 is limited. Proposed hypotheses for gaping include thermoregulation and the evaluation of potential environmental conditions. To determine temperature effects, we tracked head surface (Tsh), body surface (Tsb), and ambient (Ta) temperatures with insolation utilization and positions. To evaluate potential environmental stimuli, we tested behavioral effects (i.e., open-eye frequency) and recorded conspecific presence, day and night events, and interaction with flies and fish. We included 24 extant species representatives, with detailed assessments of American Alligators (Alligator mississippiensis), Crocodylus siamensis, Crocodylus intermedius, Crocodylus rhombifer, and Crocodylus halli. Observations occurred during a range of Ta (3.89–32.228C) with mean Tsh consistently higher than both Tsb and Ta across all crocodilians. Differences in Tsh and Ta were most pronounced with head in the sun. However, no significant differences in Tsh and Tsb were detected for A.
    [Show full text]
  • Short Review of Dental Microstructure and Dental Microwear in Xenarthran Teeth
    231 Short review of dental microstructure and dental microwear in xenarthran teeth Daniela C. Kalthoff Introduction Dentin is one of three tooth tissues occurring in mammals, Also using SEM technique, the most comprehensive and the other two being the hypermineralized tooth enamel detailed histological study to date is from Kalthoff (2011), and tooth cementum. In respect to volume, dentin usu- comprising teeth from about 50 xenarthran taxa dating ally makes up the largest part of the tooth. Interestingly, from late Eocene to Holocene. a number of mammal taxa have reduced the resistant Dental microwear analysis is the study of microscopic layer of tooth enamel during their evolutionary history, scars on the chewing surface of cheek teeth. Last consumed thus focusing on dentin as the main tooth building tissue. food items (and potentially also exogenous grit; Hoffman Enamelless teeth can be found in various extant and ex- et al. 2015) leave these scars, mainly different kinds of tinct taxa of odontocete whales (Odontoceti), aardvarks pits and scratches, during mastication and different food (Tubulidentata), armadillos, glyptodonts and pampatheres categories (leaves, grass, seeds, fruits, meat, insects, (Cingulata), sloths (Folivora), walruses (Odobenidae), sea etc.) produce different kinds of scars. Extant species with cows (Dugongidae), and elephants (Proboscidea). known diets are used to calibrate microwear scars. From This review will give an overview of recent results on the beginning of dental microwear analysis, the highly histology as well as dietary adaptations using the distinctly mineralized enamel had been the target tissue, and this built dentin teeth in armadillos and sloths and their fossil technique has been employed to various mammal clades relatives (in the following referred to with the informal term (e.
    [Show full text]
  • The Respiratory Mechanics of the Yacare Caiman (Caiman Yacare Daudine)
    First posted online on 29 November 2018 as 10.1242/jeb.193037 Access the most recent version at http://jeb.biologists.org/lookup/doi/10.1242/jeb.193037 The Respiratory Mechanics of the Yacare Caiman (Caiman yacare Daudine) Michelle N. Reichert1, Paulo R.C. de Oliveira2, 3, George M.P.R. Souza4, Henriette G. Moranza5, Wilmer A.Z. Restan5, Augusto S. Abe6, Wilfried Klein2, William K. Milsom7 1Royal Veterinary College, University of London, London, UK 2Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil 3Instituto Federal do Paraná- Câmpus Avançado Goioerê, Goioerê, PR, Brazil 4School of Medicine of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil 5Clinica Médica Veterinária, Universidade Estadual Paulista, Jaboticabal, SP, Brazil 6Departamento de Zoologia, Universidade Estadual Paulista, Rio Claro, SP, Brazil 7Department of Zoology, University of British Columbia, Vancouver, B.C., Canada Author for correspondence: Michelle N Reichert, [email protected] Key words: respiratory mechanics, static compliance, dynamic compliance, elastic forces, resistive forces, work of breathing Summary Statement: The respiratory system of the caiman stiffens during development as the body wall becomes more muscular and keratinized. Most of the work of breathing is required to overcome elastic forces and increases when animals are submerged. Flow resistance, primarily arising from the lungs, plays a significant role at higher ventilation frequencies. © 2018. Published by The Company of Biologists Ltd. Journal of Experimental Biology • Accepted manuscript Abstract The structure and function of crocodilian lungs are unique compared to other reptiles. We examine the extent to which this, and the semi-aquatic lifestyle of crocodilians affect their respiratory mechanics.
    [Show full text]
  • The Intervals Method: a New Approach to Analyse Finite Element Outputs Using Multivariate Statistics
    The intervals method: a new approach to analyse finite element outputs using multivariate statistics Jordi Marcé-Nogué1, Soledad De Esteban-Trivigno2,3, Thomas A. Püschel4 and Josep Fortuny2,5 1 Centrum für Naturkunde, University of Hamburg, Hamburg, Germany 2 Virtual Palaeontology, Institut Català de Paleontologia, Bellaterra, Spain 3 Transmitting Science, Piera, Spain 4 School of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom 5 Centre de Recherches en Paléobiodiversité et Paléoenvironnements, Museum national d'Histoire naturelle, Paris, France ABSTRACT Background. 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. Methods. 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. Results. 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. Submitted 10 March 2017 Discussion. We show that the proposed approach is a useful methodology not Accepted 20 August 2017 affected by the characteristics of the finite element mesh.
    [Show full text]
  • The Osteoderm Microstructure in Doswelliids and Proterochampsids and Its Implications for Palaeobiology of Stem Archosaurs
    The osteoderm microstructure in doswelliids and proterochampsids and its implications for palaeobiology of stem archosaurs DENIS A. PONCE, IGNACIO A. CERDA, JULIA B. DESOJO, and STERLING J. NESBITT Ponce, D.A., Cerda, I.A., Desojo, J.B., and Nesbitt, S.J. 2017. The osteoderm microstructure in doswelliids and proter- ochampsids and its implications for palaeobiology of stem archosaurs. Acta Palaeontologica Polonica 62 (4): 819–831. Osteoderms are common in most archosauriform lineages, including basal forms, such as doswelliids and proterochamp- sids. In this survey, osteoderms of the doswelliids Doswellia kaltenbachi and Vancleavea campi, and proterochampsid Chanaresuchus bonapartei are examined to infer their palaeobiology, such as histogenesis, age estimation at death, development of external sculpturing, and palaeoecology. Doswelliid osteoderms have a trilaminar structure: two corti- ces of compact bone (external and basal) that enclose an internal core of cancellous bone. In contrast, Chanaresuchus bonapartei osteoderms are composed of entirely compact bone. The external ornamentation of Doswellia kaltenbachi is primarily formed and maintained by preferential bone growth. Conversely, a complex pattern of resorption and redepo- sition process is inferred in Archeopelta arborensis and Tarjadia ruthae. Vancleavea campi exhibits the highest degree of variation among doswelliids in its histogenesis (metaplasia), density and arrangement of vascularization and lack of sculpturing. The relatively high degree of compactness in the osteoderms of all the examined taxa is congruent with an aquatic or semi-aquatic lifestyle. In general, the osteoderm histology of doswelliids more closely resembles that of phytosaurs and pseudosuchians than that of proterochampsids. Key words: Archosauria, Doswelliidae, Protero champ sidae, palaeoecology, microanatomy, histology, Triassic, USA.
    [Show full text]
  • Pleistocene Mammals of North America Pdf
    Pleistocene mammals of north america pdf Continue Subscription and order Prices To buy short-term access, please sign up to your Oxford Academic Account above. You don't have an academic account at Oxford yet? Registration of the Pleistocene Mammals of North America - 24 hours of access Start your review of the Pleistocene mammals of North America Very, very dry and actual so don't worry if you're passionately interested in Pleistocene mammals, or assignments comparing the fauna of the Hell Creek Formation with the Pleistocene fauna... and what are the chances of that? Useful reference book, now, alas, a little outdated. End of big beasts Who or what snuffed out megafauna 11,000 years ago? Holdings Description Comments Similar Items Staff Viewing similar items palorchestes (Museum of Victoria). In the second half of the Kenosoy era - about 50 million years ago until the end of the last ice age - prehistoric mammals were much larger (and alien) than their modern counterparts. On the following slides you will find photos and detailed profiles of more than 80 different giant mammals and megafauna that ruled the earth after the extinction of dinosaurs, ranging from Aepycamelus to Woolly Rhino. Epicomelus. Name of Heinrich Harder: Aepycamelus (Greek for high camel); pronounced AY-peeh-CAM-ell-us Habitat: Plains of North America Historical Age: Medium-Late Miocene (15-5 million years ago) Size and Weight: About 10 feet tall on the shoulder and 1000-2000 pounds Diet: Plants Distinctive Characteristics: Large Size; Long, giraffe-like legs and neck right off the bat, there are two strange things about Aepycamelus: first, this camel megafauna is more like a giraffe, with its long legs and slender neck, and secondly, it lived in the Miocene of North America (not a place that is usually associated with camels).
    [Show full text]
  • Mammalia, Xenarthra)
    AMEGHINIANA (Rev. Asoc. Paleontol. Argent.) - 41 (4): 651-664. Buenos Aires, 30-12-2004 ISSN 0002-7014 Functional and phylogenetic assessment of the masticatory adaptations in Cingulata (Mammalia, Xenarthra) Sergio F. VIZCAÍNO1, Richard A. FARIÑA2, M. Susana BARGO1 and Gerardo DE IULIIS3 Abstract. Cingulata -armadillos, pampatheres and glyptodonts- are among the most representative of South American Cenozoic mammalian groups. Their dental anatomy is characterised by homodonty, hypselodonty, and the absence of enamel in almost all known species. It has been proposed that these peculiarities are related to a primitive adaptation to insectivory and that they represent a strong phylogenetic constraint that restricted, or at least conditioned, adaptations toward other ali- mentary habits. However, the great diversity of forms recorded suggests a number of adaptive possibilities that range from specialised myrmecophagous species to carrion-eaters or predators among the animalivorous, and from selective browsers to bulk grazers among herbivores, as well as omnivores. Whereas armadillos (Dasypodidae) developed varied habits, mostly an- imalivorous but also including omnivores and herbivores, pampatheres (Pampatheriidae) and glyptodonts (Glyptodontidae) were herbivores. Morphofunctional and biomechanical studies have permitted a review of previous hypotheses based solely on comparative morphology. While in some cases these were refuted (carnivory in peltephiline armadillos), they were corrob- orated (carnivory in armadillos of the genus Macroeuphractus;
    [Show full text]