Descrição: Decifrando a Terra preenche uma lacuna na literatura didática em Geociências. Com abordagem introdutória apresenta a dinâmica do planeta Terra
forma moderna. Seu escopo multidisciplinar explicando conceitos básicos
das Ciências Geológicas está voltado ao estudante universitário nos Geologia, Geofísica, Geografia, Biologia, Química, Oceanografia, e Engenharias, bem como ao interessado em compreender como funciona seu Planeta. Ao enfatizar o
do ser humano como agente transformador da superfície terrestre, induz o
leitor a uma reflexão responsável sobre assuntos que afetam o
desenvolvimento da sociedade.
Informações Do Curso: Nome: Decifrando a Terra – Completo Autor: Wilson Teixeira, Fábio Taioli e Thomas Fairchild Gênero: Curso Editora: Textos Formato: Tamanho: 229 Mb Idioma: Português
Decifrando a Terra - Download
Seguindo
a mesma linha do post mais visitado do Estudando Geologia, o do livro
Para Entender a Terra, trago um outro livro que é bastante procurado.
O Decifrando a Terra veio preencher uma lacuna que já vinha sendo
sentida há algum tempo quando o assunto era o Ensino das Geociências.
Com conteúdo bastante atual e a citação de exemplos que ocorrem no
Brasil, o que o diferencia bastante dos outros que não traziam essa
abordagem. Ele enfoca principalmente nos processos que controlam e
modelam a superfície do planeta e o interior, contado desde o
princípio, no Big Bang, até os processos que atuam agora.
O livro é composto por 28 capítulos que ''desvendam'' os segredos da
formação e das alterações que sofre a Terra. São trabalhados assuntos
como tipos de rocha e sua formação/transformação estrutural em escala de
macro e micro; tectônica global e a dança que move os continentes; ação
dos agentes do intemperismo; e também as transformações antrópicas que
afetam a superfície terrestre.
Para baixar os capítulos, clique nos links abaixo.
Peço desculpas por compartilhar uma edição que não é a mais recente, que seria a 2ª Edição, publicada em 2009.
LIVRO DE GEOLOGIA
George H. Davis, "Structural Geology of Rocks and Regions, 3rd edition"
George H. Davis, "Structural Geology of Rocks and Regions, 3rd edition" W ey | 2011 | ISBN: 0471152315 | 839 pages | PDF | 87,1 MB
Relates the physical and geometric elegance of geologic structures
within the Earth's crust and the ways in which these structures reflect
the nature and origin of crystal deformation through time. The main
thrust is on applications in regional tectonics, exploration geology,
active tectonics and geohydrology. Techniques, experiments, and
calculations are described in detail, with the purpose of offering
active participation and discovery through laboratory and field work.
Pale
Blue Dot é um livro escrito por Carl Sagan em 1994. Sagan foi inspirado
pela fotografia da Terra, a 6,4 bilhões de quilômetros de distância,
mostrando-a como um pálido ponto azul.
Nele
Sagan coloca em questão a necessidade de nós humanos entendermos a
raridade de recursos propícios à vida, demonstrando o quão pequeno é o
nosso lar em um universo infinito onde não passamos de herdeiros
temporários do nosso pequeno mundo que por acidente adquiriram a
capacidade de destruir o mesmo.
Veja o que Carl Sagan escreveu em 1994 a respeito da nossa casa, nosso planeta Terra:
“Olhe
o pálido ponto azul. É aqui. É a nossa casa. Isso somos nós. Ali estão
todos que você ama, todos que você conhece, de quem já ouviu falar, todo
ser humano que já existiu, que já viveram suas vidas. O compêndio da
nossa alegria e sofrimento, milhares de religiões conflitantes,
ideologias e doutrinas, cada predador e presa, heróis e covardes,
criadores e destruidores de civilizações, reis e camponeses, cada jovem
casal apaixonado, cada mãe e filho, pai, esperançoso, inventor e
explorador, cada professor da moral, cada político corrupto, cada
“superstar”, cada “líder supremo”, cada santo e pecador na história da
nossa espécie, ali – num grão de poeira suspenso num raio de sol.
A
Terra é um palco muito pequeno em uma imensa arena cósmica. Pensem nos
rios de sangue derramados por todos os generais e imperadores para que,
na glória do triunfo, pudessem ser os senhores momentâneos de uma fração
de um ponto. Pensem nas crueldades infinitas cometidas pelos habitantes
de um canto desse pixel contra os habitantes pouco distinguíveis de
algum outro canto, em seus freqüentes conflitos, em sua ânsia de
recíproca destruição, em seus ódios ardentes. Nossas atitudes, nossa
imaginada auto-importância, a ilusão de que temos uma posição
privilegiada no universo, são desafiadas por este ponto de luz pálida.
Nosso
planeta é um pontinho solitário na grande escuridão cósmica circundante.
Em nossa obscuridade, em toda essa imensidão, não há nenhum indício de
que a ajuda virá de outro lugar para nos salvar de nós mesmos. A Terra é
o único mundo conhecido até agora para abrigar vida. Não há nenhum
outro lugar, pelo menos no futuro próximo , para onde nossa espécie
possa migrar. Visita, sim. Para assentamento, ainda não. Goste ou não, a
Terra é o lugar onde nós fazemos o nosso teatro.
Tem
sido dito que a astronomia é uma experiência de construção humilde e
edificadora do personagem. Talvez não exista melhor comprovação da
loucura das vaidades humanas do que esta distante imagem de nosso mundo
minúsculo.
Para
mim, ela enfatiza a responsabilidade de nos relacionarmos mais
bondosamente uns com os outros e de preservarmos e amarmos o pálido
ponto azul, o único lar que conhecemos...a Terra!
Carl Sagan – 1994
DOCUMENTÁRIO
Planeta Terra: Episódio 04 – Cavernas
Sinopse
Simplesmente a mais grandiosa produção já feita sobre a natureza e a vida selvagem do planeta.
Vivemos em um planeta de uma beleza estonteante. Dos cumes das montanhas
do Nepal até o verde intenso da Amazônia; das áridas esculturas do
Seara até as brilhantes calotas polares, nosso mundo é realmente espetacular. Usando câmeras
de alta definição, um orçamento sem precedentes, nenhuma parte do nosso
planeta ficou inexplorada. Sequências de tirar o fôlego testemunham a
evolução do meio ambiente através dos tempos. Graças aos recursos da
tecnologia, os expectadores podem chegar a lugares inimagináveis: de um
vulcão em erupção até o centro da terra.
Mega-Bites: Extreme jaw forces of living and extinct piranhas (Serrasalmidae)
Here, we document in-vivo
bite forces recorded from wild piranhas. Integrating this empirical
data with allometry, bite simulations, and FEA, we have reconstructed
the bite capabilities and potential feeding ecology of the extinct giant
Miocene piranha, Megapiranha paranensis. An anterior bite force of 320 N from the black piranha, Serrasalmus rhombeus, is the strongest bite force recorded for any bony fish to date. Results indicate M. paranensis'
bite force conservatively ranged from 1240–4749 N and reveal its novel
dentition was capable of resisting high bite stresses and crushing
vertebrate bone. Comparisons of body size-scaled bite forces to other
apex predators reveal S. rhombeus and M. paranensis have
among the most powerful bites estimated in carnivorous vertebrates. Our
results functionally demonstrate the extraordinary bite of serrasalmid
piranhas and provide a mechanistic rationale for their predatory
dominance among past and present Amazonian ichthyofaunas.
The evolution of gnathostome jaws, along with bite forces that
can capture and masticate active prey is a key functional innovation
underlying the diversification of early Devonian vertebrates1.
As a result of their fundamental importance in expanding predatory
niches and promoting the success of vertebrates, jaws and bite forces in
living and extinct species have been repeatedly modeled through lever
and linkage mechanics, bite simulations, and 3-D finite element analyses
(FEA)2, 3, 4, 5, 6. However, few theoretical studies have validated their models with empirical measurements from living taxa7, 8, 9. In-vivo
experiments in the field to elicit and record ecologically realistic
biting behaviors for predatory species are rare, dangerous, and
difficult to perform10.
Among bony fishes, piranhas (Serrasalmidae) represent an ideal group of
predatory vertebrates in which to investigate the evolution of extreme
biting capabilities because of their aggressive nature, relatively small
size, and accessible populations. While anecdotes of piranha-infested
waters skeletonizing hapless victims are generally hyperbole, the
effectiveness of their bite is not. Even at their small body sizes, diet
studies indicate that piranhas will attack and bite chunks out of prey
many times larger than themselves11, 12, 13.
Recent
molecular evidence indicates there are three major subclades of the
Serrasalmidae: 1) the carnivorous piranha-clade, 2) the omnivorous Myleus-clade, and 3) the herbivorous pacu-clade14. Within the piranha-clade, feeding ecology varies from the typical flesh and fin eating forms of Serrasalmus and Pygocentrus spp., to the highly specialized lepidophagous (i.e. scale-eating) Catoprion mento. Tooth shape and dentition patterns in Serrasalmidae demonstrate a strong functional relationship to diet11, 12, 13.
Carnivorous piranhas typically have jaws lined with a single row of 6–7
serrated, multi-cusped, triangular, blade-like teeth. Dentition and
tooth morphology have long been used to classify serrasalmid species15, 16. In 2009, Cione et al.17 described a new extinct serrasalmid species of the Upper Miocene from the Paraná geological formation in Argentina. Megapiranha paranensis
is classified as a new genus of a giant, piranha-like species described
from a single fossilized premaxilla jaw bone fragment that had a set of
three triangular teeth set in a zig-zag pattern. The fossil teeth are
also morphologically distinct. They have labio-lingually compressed
pointed cusps with finely serrated cutting edges similar to a shark. In
contrast, the mid tooth expands into a broad lingual shelf that is
anchored to the jaw with a robust circular base (Fig. 1, inset). These morphological synapomorphies with extant serrasalmid species place M. paranensis as sister taxa to the carnivorous “piranha-clade” and a more distant intermediate relative to the herbivorous “pacu-clade” (SI Fig. 1).
Figure 1: Skull anatomy of S. rhombeus (photo by SH) and fossil teeth of M. paranensis (inset, reprinted from Cione et al.).
Teeth of S. rhombeus and M. paranensis share similarly shaped cusps that form labio-lingually compressed triangular blades. Arrow (inset) demarks fine serrations on M. paranensis tooth for slicing flesh. Homologous landmarks were measured as length of labial base (mm) for the 5th premaxillary tooth (A). Allometric relationship describing growth of the 5th tooth relative to body size, measured as total length (mm) in the black piranha, S. rhombeus (B). Tooth length scales isometrically with increasing body size (slope = 1.02). Data were log10 transformed and fitted to a least-squares linear regression model: Log10 (tooth) = 1.02 Log10 (TL) − 1.91 (r2 = 0.96, F (1,14) = 339.8; p < 0.0001). Using this regression equation, a conservative body size of 71 cm TL was back-calculated for M. paranensis and was subsequently used to estimate its lower bound of bite forces (Fig. 2A).
The dentition pattern and tooth shape of the M. paranensis
fossil indicates an intermediate morphology capable of both slicing soft
flesh and crushing hard prey. However, the diet of this giant piranha
species still remains a mystery. The Miocene epoch is renowned for its
gigantism in Neotropical aquatic flora and fauna18, 19. Thus, it is reasonable to assume the food resources available to Megapiranha would likely have required jaw forces and dental weaponry capable of capturing and processing very large prey.
Here we report the first in-vivo bite forces recorded from wild specimens of the largest species of carnivorous piranha, Serrasalmus rhombeus,
and describe the underlying functional morphology of the jaws that
power their bite. Using this extant species as an allometric surrogate,
we are able to infer the feeding ecology of the giant Miocene piranha, M. paranensis,
by reconstructing its bite forces and the mechanical capabilities of
its unique dentition. Lastly, by removing the effects of body size, we
are able to demonstrate that the biting abilities of these relatively
diminutive serrasalmid fishes have biomechanically surpassed much larger
iconic predators documented in the literature.
Maximum bite force was tested in-vivo for 15 specimens of Serrasalmus rhombeus ranging in body length from 205 to 368 mm TL using a customized force gauge (SI Table 1).
Bite force varied nearly five-fold from 67 N in a 0.17 kg individual to
more than 320 N for a 1.1 kg specimen. To examine the ontogeny of bite
performance in S. rhombeus, we plotted bite force against body size (Fig. 2A). In-vivo bite forces in S. rhombeus
scale with significant positive allometry (slope = 2.30) demonstrating
that jaw strength increases considerably faster than body length.
Figure 2
Scaling of maximum in-vivo bite forces (N) plotted against body size (TL) for Serrasalmus rhombeus (A).Data were Log10 transformed and fitted to least squares linear regression: Log10 (N) = 2.30 Log10 (TL) − 3.469 (r2 = 0.77, F(1,14) = 43.7; p < 0.0001). Predicted maximum bite force for a 71 cm TL M. paranensis is also plotted (dashed arrow).
Jaw functional morphology revealed a massive adductor mandibulae muscle
complex (AM) that rotates the lower jaw postero-dorsally (white arrow)
via a robust rope-like tendon (B, C). Lower jaw mechanics depict a
highly modified 3rd class lever where the closing mechanical
advantage (Li/Lo) amplifies AM muscle force transmission by 50% to 150%
from the jaw tip to the posterior teeth (C).
Dissections of S. rhombeus'
jaws reveal their powerful bite is generated by a massive adductor
mandibulae muscle complex. It is made up of four distinct subdivisions:
A1, A2 lateral, A2 medial, A3 (Fig. 2B, C).
The A1 subdivision is a smaller fusiform muscle that originates on the
ventral portion of the preopercle and extends dorso-rostrally to wrap
around the coronoid process of the articular and insert onto the
dorso-medial surface of the dentary. The two large A2 subdivisions span
out and fill the entire suspensorium to make up more than 80% of the
adductor mandibulae mass. Together the A2 subdivisions along with the
medial A3 fuse into a thick rope-like tendon that inserts supra-distally
into a deep Mecklian fossa on the medial lower jaw (Fig. 2C).
The
mechanical advantage (MA) of the lower jaw in vertebrates determines
the proportion of adductor muscle force that is transmitted to the bite
and is a function of the ratio of the in-lever length (Li = the distance
from the jaw joint to where the adductor muscles insert onto the
mandible) to the out-lever length (Lo = the distance from the jaw joint
to the distal-most tooth tip). In Serrasalmus rhombeus, the
extreme anterior insertion of the A2/A3 tendon creates a high mechanical
advantage for even the most rostral teeth (MA ~ 0.5) (Fig. 2C, Table 1). For practical comparison, if the prey is bitten farther back along the lower jaw at the 4th tooth position, the shorter Lo increases the MA to 1.0 and approaches 1.5 at the most posterior teeth.
Table 1: Comparison of in-vivo and theoretical bite forces (BF) derived from adductor mandibulae (AM) physiology and lower jaw morphometrics for Serrasalmus rhombeus (N = 6)
To investigate the effects of having a massive adductor mandibulae
complex in combination with a high MA on piranha bite force, we ran a 2D
computer simulation that uses jaw morphometrics and adductor muscle
physiology parameters to predict bite forces in six individual S. rhombeus
covering a range of body size. As expected from the jaw lever
mechanics, simulation results demonstrate bite force nearly doubles from
the anterior most teeth to the mid-jaw position (Table 1).
For one of our largest specimens (TL = 365 mm), predicted mid-jaw bite
force (where MA = 1.0) was calculated to be as high as 631 N, more than
twice the in-vivo bite force recorded for this individual.
However, an analysis of covariance comparing simulation results with our
empirical data revealed the predicted anterior bite forces derived from
jaw morphometrics are not significantly different from the maximum in-vivo bite forces recorded for these specimens (Table 1).
Body size and bite force reconstruction
Estimates for Megapiranha paranensis were back-calculated from allometric relationships of tooth growth and in-vivo bite force for S. rhombeus. In contrast to previously published estimates (~73 kg, 128 cm TL)17, our allometric analysis of M. paranensis' fossil premaxilla suggests a more conservative body size: ~10 kg, 71 cm TL (Fig. 1B). Bite force predictions for M. paranensis
using our calculated body size and the previous published estimate
ranged from 1240 to 4749 N, respectively, at least a 4-fold increase in
bite force over the largest S. rhombeus (Fig. 2A).
Bite simulations and fea of fossil teeth
Bite simulations using a bronze-alloy metal replica of the M. paranensis
jaw fossil were conducted to examine the potential for comminution of
bony materials. These indentation trials tested the fossil teeth's
ability to penetrate ecologically relevant bony prey of varying
thickness. Using the predicted bite force range (e.g. 1245–4448 N), Megapiranha's
teeth penetrated the thick cortical layer (5.94 mm) of a bovine femur
in a primarily linear fashion generating piercing indentations from
1.0–2.3 mm deep (Fig. 3).
Further simulation tests on aquatic turtle carapace and dermal scales
from armored catfishes repeatedly resulted in catastrophic punctures at
much lower bite forces (range = 66.7–889.6 N; SI Movie 1).
Figure 3: Bite simulation curves using a metal-alloy replica of M. paranensis fossil upper jaw (left inset) indenting a bovine femur (Δ), aquatic turtle carapace (O, Phrynops sp.), and dermal scales from an Amazonian armored catfish (+, Pterygoplichthys multiradiatus).
Black arrows indicate the predicted anterior bite force for small and large body size estimates of M. paranensis. The 3rd and 5th
teeth punctured the cortical bone layer of the bovine femur from
1.0–2.3 mm (inset upper right corner). Results from the turtle carapace
and catfish dermal scales reveal Megapiranha's dentition pierces through these bony prey items at relatively low forces.
To better understand the functional significance of the unique shape of the M. paranensis
premaxillary tooth, we used FEA programs to simulate the predicted
loads generated during biting. We applied these loads to models of the M. paranensis
premaxillary teeth, as well as to homologous teeth of two closely
related serrasalmid relatives that cover the spectrum of tooth shapes
and feeding ecologies (Fig. 4).
We examined both Von Mises stress, which acts as a predictor of the
likelihood of failure, and Total Strain Energy, which predicts
resistance to deformation and thus efficiency of the shape at
transmitting bite forces. Using these two metrics, we examined the
effects of different tooth shapes under the high loading regimes that
would be experienced when biting into hard bony materials. FEA results
indicate when force is applied at the cusp of the tooth, stresses are
concentrated around the loading area in all three morphs. In addition,
stresses are distributed across the body of the Piaractus brachypomus
tooth, onto the medial face. Distribution patterns change when force is
applied over the upper third of the tooth as if it were puncturing
through a hard bony material. Across all tooth types, stresses are
concentrated around the lowest point of loading. However, stresses are
distributed through the body of the tooth in both the P. brachypomus and M. paranensis and are channeled to the base of the tooth. In contrast, stresses in the Pygocentrus nattereri
tooth remain concentrated in a broad ring around the middle of the
tooth. The magnitudes of Von Mises stresses and Total Strain Energy are
consistently higher in the sharper P. nattereri and M. paranensis tooth morphologies compared to the blunter shape of P. brachypomus indicating a greater likelihood of structural failure and deformation while puncturing hard materials at these forces (Fig. 4; Table 2).
Figure 4: Finite Element Analysis of serrasalmid dentition.
Maximum and minimum Von Mises stresses reported for maximum predicted bite force (scaled relative to predicted bite forces in Megapiranha);
distribution of stresses remains the same regardless of magnitude of
applied force. Warmer colors indicate higher concentrations of Von Mises
stress and cooler colors reflect lower stress concentrations. Higher
concentrations of Von Mises stress indicates a greater likelihood of
failure in that region of the tooth.
An in-vivo bite force of 320 N in Serrasalmus rhombeus is the strongest yet recorded for any bony or cartilaginous fish to date7, and is nearly three times greater than the bite force of an equivalent size American alligator8.
Positive allometry of bite force is common in carnivorous and
durophagous bony and cartilaginous fishes that excise chunks of flesh or
fracture hard-shelled prey by crushing3, 20, 21, 22. Our analysis of wild piranhas fits this trend, and the in-vivo data demonstrate that S. rhombeus
can bite with a force more than 30 times its weight, a remarkable feat
yet unmatched among vertebrates. However, it should be noted that there
was some variation in our in-vivo bite force data among similar
sized individuals that was likely caused by some individuals under-
performing due to stress or fatigue. At least one fish (TL = 310 mm)
appears to be an outlier in the regression depressing the slope of the
relationship. Removal of this individual increases the slope to 2.48 and
improves the r-square of the relationship to 0.85. Thus, taking this
outlier into account, the significant positive allometry of bite force
presented here should be considered a conservative lower bound for
maximal performance in S. rhombeus.
How do black piranhas
achieve these powerful bites at such relatively small sizes? The answer
stems from the extraordinary size of the adductor mandibulae complex and
the efficient transmission of its large contractile forces through a
highly modified jaw closing lever. Indeed, the mass of the adductor
mandibulae complex makes up over 2% of S. rhombeus' total body mass. The highest percentage yet recorded for bony fishes23.
This large muscle mass combined with a short overall muscle length
results in a huge physiological cross sectional area that is directly
proportional to the amount of force it can produce (Fig. 2B, Table 1). Furthermore, the extreme anterior insertion of the A2/A3 tendon gives S. rhombeus an anterior bite force that is powered by one of the highest jaw closing mechanical advantages ever identified in fishes (Fig. 2C, Table 1)24.
Thus, unlike many actinopterygiian fishes where the closing MA of the
lower jaw averages 0.27 (i.e. less than 30% of the adductor's muscle
force is transmitted to the bite), S. rhombeus' lower jaw lever
can harness 50% of the adductor complex's force generating capacity at
the tip of its jaws. Even more impressive, if the prey is bitten on the
lateral side of the jaws near the posterior teeth, this musculoskeletal
arrangement further increases the jaw's closing MA to amplify the
adductor complex's torque during biting by as much as 150% (Fig 2C).
Our simulations results demonstrate how this underlying functional
morphology amplifies the adductor muscles' force so that even the
smallest specimen (0.22 kg) can potentially generate a range of
traumatic bite forces across the jaw (e.g. 72–123 N; Table 1).
The fact that our theoretical estimates for anterior bite force are
statistically indistinguishable from the bite performances that were
recorded near the tip of the jaws indicates the 2D model's simulation of
lever mechanics combined with adductor muscle physiology accurately
explains bite force capability in S. rhombeus. So, when one
considers their unique jaw functional morphology combined with their
aggressive biting behavior, it should come as no surprise that black
piranha whether large or small can rapidly and efficiently excise large
chunks out of their prey.
Although our body size estimate of M. paranensis is considerably smaller than previous published accounts17, it is still more than triple the maximum body size of extant S. rhombeus15.
It is also important to note that both of these estimates fall within
the range of sizes for the largest living serrasalmid, the frugivorous
Tambaqui, Colossoma macropomum15.
Paleontological reconstructions using fossil evidence and inferences
drawn from related extant taxa are commonly used to generate hypotheses
about ecology, behavior, and biomechanics of extinct species2, 4, 5, 25, 26. Because of their close phylogenetic relationship, we assumed homologous jaw biomechanics, and used the ontogeny of S. rhombeus as a proxy to predict Megapiranha's bite forces. For comparison, our analysis predicts Megapiranha's bite was equivalent to the anterior bite force of a great white shark weighing over 400 kg (SI Table 3). Again, these bite force predictions likely underestimate Megapiranha's maximum bite force since they are based on the allometry of the variable in-vivo data. Furthermore, the in-vivo
allometric relationship represents anterior bite forces and does not
take into account the potential for doubling bite forces along the lower
jaw. Thus, if M. paranensis did have similar musculoskeletal architecture in the lower jaws as in S. rhombeus (Fig. 2C)
but scaled up to its larger body sizes, then the mechanical advantage
at its mid-jaw (MA = 1.0) could have produced bite forces as high as
2480 N to 9498 N. With these amplified estimates, a 73 kg Megapiranha's biting attack would have had the same ferocity of a 3000 kg great white shark (SI Table 3)5.
What Megapiranha
fed on with these powerful bites is uncertain. Tooth morphology
commonly reflects feeding ability in fishes, with a strong functional
relationship to diet in the Serrasalmidae11, 16, 23. However, the unique dentition of M. paranensis presents a paradox, exhibiting traits from relatives of both the herbivorous pacu-clade and the carnivorous piranha-clade14, 17. Megapiranha
teeth have robust circular bases with a broad lingual shelf that tapers
into short serrated triangular blades at the crown, making them
potentially suited for processing both soft and hard prey materials (Fig 2, inset). Did Megapiranha
use their strong jaws and novel dentition to not only slice into their
prey's compliant flesh, but also crush through their stiff bones? Our
bite simulations indicate Megapiranha's hybrid teeth were
indeed capable of transmitting sufficient bite pressure to generate
micro-fractures in robust cortical mammalian bone as well as complete
mechanical failure of thinner vertebrate bony tissues (Fig 3).
For comparison, even modern carnivorous piranhas species with less
robust tooth shapes are capable of some bone comminution as they often
feed by taking bites out of the bony fins of fishes11, 12, 13. In fact, there are also documented cases of S. rhombeus biting off and consuming human phalanges27. Thus, the combination of applying the predicted bite forces from the allometry of S. rhombeus with the fossil replica in our penetration tests demonstrates the tooth shape of M. paranensis
would have facilitated an osteophagous diet of turtles and armored
catfish and to a lesser extent limb structures of larger terrestrial
mammals during the Miocene Epoch.
From the FEA models, the distribution of Von Mises stresses in the M. paranensis
tooth revealed hybrid patterns that reflect those observed in both the
sharp triangular blades of the carnivorous red belly piranha, Pygocentrus nattereri, and the blunt cuspids of the durophagous pacu, Piaractus brachypomus (Fig. 4). When loaded at the tip, both M. paranensis and P. nattereri exhibit Von Mises stress distributions similar to FEA models of shark teeth puncturing soft prey28.
In contrast, once the tip has presumably pierced into the bony material
and compressive loading regimes are focused on the upper third of the
tooth, the shape of M. paranensis distributes Von Mises stresses like the half-domed mollariform shape of P. brachypomus.
The pattern reveals a reduction of Von Mises stresses in the broader
sloped middle portion of the cusp where increased enameled surface area
would come in contact with the bony prey material material after initial
penetration (Fig. 4).
The distribution patterns of Total Strain Energy (not shown) also
closely mirrored the Von Mises stresses, indicating higher efficiency
and lower deformation in the same region. Contrary to our initial
hypothesis, the hybrid morphology of the M. paranensis tooth
revealed the highest Von Mises stresses and Total Strain Energies of the
three species, though the differences are slight (Table 2).
This suggests that there are performance tradeoffs when combining
shapes for piercing and crushing in the same tooth. However, while
relative stresses and strain energies are high in M. paranensis, their distribution patterns reflect tensile strains, not only similar to those we found in P. brachypomus, but also seen in FEA modeling of mammalian cingulum29.
A partial cingulum in mammals creates a morphologically similar shelf
that reduces tensile strains patterns in the tooth by as much as 21%
after penetrating the prey. This enhanced strain resistance is
apparently achieved by increasing the total surface area of the shelf
that comes in contact with load. The M. paranensis tooth is
apparently able to overcome these scaled shape limitations in a similar
way by being absolutely larger than the teeth of either P. nattereri and P. brachypomus
and expanding the surface area of the lingual slope where crushing
forces would be most efficiently transmitted. Thus, the novel shape of Megapiranha's
dentition appears functionally adapted to not only focus stress at the
tip while puncturing flesh like the teeth of a red belly piranha, but
also effectively spread impact stresses through the thicker broader base
for cracking through bony materials similar to a nut- crushing pacu.
From
these integrated simulations and FEA models, we surmise feeding on
significantly hard prey items was at least biomechanically possible for M. paranensis.
Confirmation of true osteophagous behavior on large vertebrate prey,
however, still requires the discovery of Miocene fossils with bite marks
that can be attributed to its dentition. Even so, our results indicate
that the predicted bite pressures and hybrid tooth morphology of Megapiranha would have granted access to a vast menu of large prey resources present during the Miocene18.
The reconstructed bite forces of M. paranensis
are impressive, but how do they compare to other vertebrate
mega-predators? Using fossil evidence and indentation simulations
comparable to those presented here, the bite force of Tyrannosaurus rex was estimated to be over 13,400 N26, almost three times the largest M. paranensis estimate. However, much of this difference is due to scaling effects attributable to T. rex's
over 100-fold greater body mass. To control for the effects of body
size, we used published theoretical estimates for anterior bite force,
and calculated normalized bite force quotients (BFQ's)25 for nine living and extinct bony and cartilaginous fishes (Fig. 5; SI Table 3).
These species vary widely in their phylogenetic and geological origins,
but all are apex predators that feed on large prey with similar feeding
strategies and powerful jaw mechanics. Correcting for body size
differences reveals that both the living Serrasalmus rhombeus and the extinct Megapiranha paranensis have among the most powerful bites in carnivorous fishes, living or extinct. Indeed, for its relatively diminutive size, Megapiranhaparanensis' bite dwarfs other extinct mega-predators, including the enormous whale eating Carcharodon megalodon and the monstrous Devonian placoderm, Dunkleosteus terrelli.
Figure 5: Bite Force Quotients of living and extinct apex predatory fishes.
The extreme biting abilities and jaw functional morphology of wild
black piranhas presented here provide the first quantitative data that
illustrate the effectiveness of their feeding mechanism. In addition, if
our fossil reconstructions and simulations are correct, then Megapiranha paranensis
was indeed a ferocious bone-crushing mega-predator of the Miocene
epoch. Taken together with our body size corrected bite force estimates,
our results for living and extinct species validate the fearsome
predatory reputations of piranhas and establish this group of fishes as a
pinnacle of performance in gnathostome jaw evolution.
In August 2010, we collected live black piranha, Serrasalmus rhombeus
(Linnaeus, 1766), while fishing along the Xingu and Iriri tributaries
of the Amazon River basin near Altamira, Brazil. A total of fifteen fish
ranging in body size from 205–368 mm TL were collected by hook-and-line
and gill nets. To ensure minimal damage to the jaws and record maximal
performance, we used barbless hooks and carried out bite force
experiments as soon as possible after capture to reduce stress and
fatigue. After the expedition, collected specimens were donated to the
INPA Ichthyological Collection at Manaus, Brazil.
Bite performance
In-vivo
bite forces were recorded using a customized portable and waterproof
force gauge constructed of a LCGD -250 low profile miniature load cell
(range = 0–250 lbs) and a DP7600 digital high-speed load/strain meter
(500 Hz sampling rate) (www.omega.com).
This species readily performed multiple defensive bites with the
transducer placed between the tips of the jaws. After each bite, peak
force was recorded and the force gauge was removed from the jaws and
tared before the next attempt. After bite force trials, fish weight (g)
and total length (mm) were measured, and the fish was either euthanized
in an ice bath for later anatomical dissections or released alive. All
bite performance experiments with live wild caught piranhas comply with
the guidelines of the Western Kentucky University Institutional Animal
Care and Use Committee.
Jaw functional morphology
In the field, individual S. rhombeus
were sacrificed and dissected to investigate the morphology of the
lower jaw mechanism. For each fish, the main subdivisions of the
adductor mandibulae (A1, A2, and A3), the major jaw closing muscles,
were excised and weighed with an Ohaus HH-320 digital scale to the
nearest 0.1 g. Adductor mandibulae subdivisions were carefully
investigated for their origins, insertions, and lines of action.
Musculoskeletal anatomy follows the nomenclature conventions of
Machado-Allison16.
For six individual fish covering a range of body sizes (210–368 mm TL),
digital photographs of the dissected jaw anatomy were taken from the
fish's right side with a scale bar in frame. Photographs were analyzed
using ImageJ64 (http://imagej.nih.gov/ij)
to determine landmark coordinates of adductor muscle insertions and
origins and lower jaw dimensions. Morphometric data were then analyzed
with MandibLever v3.530.
MandibLever calculates static and dynamic bite forces from jaw lever
mechanics, non-linear length-tension muscle contractile properties using
the Hill equation, and estimates of adductor muscle physiological
cross-sectional area. ANCOVA was then used to compare the allometries of
simulation results and in-vivo bite performance with body size
as the covariate. A non-significant interaction term indicated parallel
slopes between these two relationships. Subsequently, the ANCOVA model
was rerun without the interaction to examine if a significant difference
existed between the predicted anterior bite forces generated by
MandibLever and the empirically measured in-vivo bite forces recorded in the wild.
Scaling analyses
We summarized the mean and standard deviations of bite performance for each individual (SI Table 1).
The peak force (N) recorded for each individual was used as a
conservative estimate of the maximum bite performance for that
individual. To scale bite forces in S. rhombeus, maximum bite
force was regressed against total length (TL). The null hypothesis was
isometry (i.e. slope = 2.0) in maximum bite force relative to body size.
A second scaling relationship was also developed to examine the growth
rate of the 5th premaxillary tooth in S. rhombeus. The
null hypothesis for isometric growth in tooth length was an expected
slope of 1.0. The regression equation for this allometric relationship
was then used as a proxy to back-calculate an estimated body size for M. paranensis using the homologous length for its 5th
premaxillary fossil tooth. Allometric relationships were developed
using standard least square regression models. All data were Log10 transformed and analyzed using JMP v5 by SAS Institute (2002) statistical software program.
Reconstructing the bite of megapiranha paranensis
We have generated hypothetical estimates of the body size and maximum bite forces of M. paranensis by extrapolating predictions from allometric relationships of its close living relative, Serrasalmus rhombeus. S. rhombeus
is the largest carnivorous species of piranha in the Amazon River basin
growing to over 3 kg. From the morphological phylogeny, the monotypic M. paranensis is nested between Catoprion and the higher monophyletic clade of Pygopristis, Serrasalmus, and Pygocentrus17 (SI Fig. 1). Thus, we chose S. rhombeus as a suitable surrogate piranha morphotype with which to reconstruct M. paranensis
bite forces based on their grossly similar carnivorous tooth
morphologies and close phylogenetic relationship. To reconstruct
hypothetical bite forces in M. paranensis, we used two estimates of body size: the smaller 710 mm TL, based on the scaling analysis of tooth growth rates in S. rhombeus in this study (Fig. 2), and the larger 1280 mm TL estimate17.
From these two body sizes, we calculated lower and upper bounds for
maximum bite forces using the regression equation generated from the
scaling relationship of S. rhombeus' in-vivo bite forces (Fig. 1A).
Bite simulations
To
investigate the effects of tooth shape on fracturing vertebrate bone,
bite simulations were conducted using a metal replica of the M. paranensis
fossil teeth and premaxilla. The full-scale dental-grade model was
forged from bronze-alloy by Master Craftsman Studios. Metal alloy
replicas of fossil teeth provide sufficient yield strength and hardness
to perform as an enameled tooth analog for testing bite indentations4, 26.
Simulation trials penetrated ecologically relevant bony prey materials
of varying thickness (e.g. cortical layer of freshly thawed bovine
femur, turtle carapace, and dermal fish scales). Indentation trials
examined normal loading of the Megapiranha replica puncturing
into the material. The bony materials were secured in a United Testing
Systems SSTM-10 KN universal loading frame and indented with the replica
at a rate of 1 mms−1 with a displacement sampling rate of
20 Hz. Each trial tested the range of predicted bite forces from this
study (e.g. 1240–4749 N) (Fig 3).
FEA of serrasalmid tooth shape
For M. paranensis
fossil tooth comparisons to extant serrasalmid species, homologous
premaxillary teeth were isolated from preserved specimens from the Field
Museum of Natural History Fish Collection for Pygocentrus nattereri (FMNH 108184) and Piaractus brachypomus
(FMNH 110198). Three dimensional tooth models were generated for each
species using a Next Engine 360° Digital Laser Scanner. Individual teeth
were then isolated from laser scans using MeshLab (v1.3.1 Visual
Computing Lab - ISTI – CNR), which was also used to fill holes and
simplify the meshes. Tooth meshes were then uploaded into Amira (v5.2.2
Visage Imaging), where they were converted from shells to solids. Solid
models were imported into Marc Mentat (2010.1.0 MSC Software
Corporation) for analysis, and elements were set to be solid tetras.
There has been little work done on non-mammalian tooth materials
properties, so we used an average of the Young's Moduli found for shark
species (7.05 e 08 N/m2)31
and a Poisson's ratio of 0.3, a standard for mineralized materials.
Nodes at the base of each tooth model, where the tooth would articulate
with the underlying bone, were held motionless while the rest of the
model was allowed to move and rotate without constraint. Each model was
subjected to two different types of loading at both the maximum and
minimum predicted bite force for Megapiranha paranensis. To
compare between teeth of different sizes, we scaled applied forces such
that the ratio of force to approximate surface area would be similar
between treatments32.
For the first treatment, to mimic the point at which the tooth first
interacts with a hard surface, we loaded a small area at the very tip of
the tooth cusp. In the second treatment, to simulate the forces exerted
when the tooth has been driven into the prey, we loaded each tooth to a
depth approximately equal to one third of the tooth height. This depth
was based on penetration distance taken during the indentation trials.
We measured the Von Mises stresses distributed in each model, as a proxy
for structural failure; higher Von Mises values means a greater
likelihood of structural failure. Stress distribution patterns in each
tooth were also compared across the different treatments. To measure
Total Strain Energy, tooth models were imported into COMSOL Multiphysics
(version 4.3.0.151) and subjected to the same load treatments. The
force used for each tooth was scaled so that the ratio of applied force
to approximate volume was equivalent for comparison between models32.
Mega-predator comparisons
Bite Force Quotients (BFQ) were calculated following the method of Wroe et al.25.
Briefly, maximum anterior bite forces (N) and body sizes (g) for each
of seven additional predatory species were gleaned from the literature (SI Table 2).
Where possible, small and large bite force estimates for each species
were included along with the low and high range of bite force
measurements for S. rhombeus and estimates for M. paranensis from this study for a total of sixteen data points. Data were then log10
transformed and all species bite forces were regressed against body
size to generate a Mega-predator linear regression equation (Log10 (Predicted BF) = 0.59 Log10(g) + 0.16; r2
= 0.84, P < 0.0001). From this Mega-predator linear regression
‘predicted’ bite forces for each species body size were calculated, and
the size corrected BFQ for each species was generated with the following
equation: (Anterior Bite Force/Predicted Bite Force) * 100.
Purnell, M. A.Chapter 12: Scenarios, selection and the ecology of early vertebrates. In Major Events in Early Vertebrate Evolution. Ed. Per Erik Ahlberg, Publishers Taylor and Francis: London and New York (2001).
Anderson, P. S. L. & Westneat, M. W.Feeding mechanics and bite force modeling of the skull of Dunkleosteus terrelli, an ancient apex predator. Biol. Lett.3, 77–80 (2007).
Grubich, J. R., Rice, A. N. & Westneat, M. W.Functional morphology and bite mechanics in the great barracuda. Sphyraena barracuda. Zoology111, 16–29 (2008).
Gignac, P. M., Makovicky, P. J., Erickson, G. M. & Walsh, R. P.A description of Deinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations. J. Vert. Paleo.30(4), 1169–1177 (2010).
Davis, J. L., Santana, S. E., Dumont, E. R. & Grosse, I. R.Predicting bite force in mammals: two-dimensional versus three-dimensional lever models. J. Exp. Biol.213, 1844–1851 (2010).
Huber, D. R., Eason, T. G., Hueter, R. E. & Motta, P. J.Analysis of bite force and mechanical design in the feeding mechanism of the durophagous horn shark,. Heterodontus francisci. J. Exp. Biol.208, 3553–3571 (2005).
Erickson, G. M., Lappin, A. K. & Vliet, K. A.The ontogeny of bite-force performance in American alligators (Alligator mississippiensis). J. Zool. Lond.260, 317–327 (2003).
Mara, K. R., Motta, P. J. & Huber, D. R.Bite force and performance in the durophagous bonnethead shark,. Sphyrna tiburo. J. Exp. Zool.311A, 1–11 (2009).
Erickson, G. M., Lappin, A. K., Parker, T. & Vliet, K. A.Comparison of bite force performance between long term captive and wild American alligators (Alligator mississippiensis). J. Zool. Lond.262, 21–28 (2004).
Machado-Allison, A. & Garcia, C.Food habits and morphological changes during ontogeny in three serrasalmin fish species of the Venezuelan floodplains. Copeia (1), 193–195 (1986).
Orti, G., Sivasundar, A., Dietz, K. & Jégu, M.Phylogeny of the Serrasalmidae (Characiformes) based on mitochondrial DNA sequences. Gen. & Mol. Biol.31, 343 (2008).
Jégu, M. Checklist of the Freshwater Fishes of South and Central America. Reis, R. E., Kullander, S. O., Ferraris, Jr. C. J. Eds. (EDIPUCRS, Brasil) pp. 182–196 (2003).
Machado-Allison, A. Studies on the systematics of the subfamily Serrasalminae (Pisces-Characidae). Ph.D. Thesis, George Washington University, pp 267 (1982).
Cione, A. L., Dahdul, W. M., Lundberg, J. G. & Machado-Allison, A.Megapiranha paranensis,a new genus and species of Serrasalmidae (Characiformes, Teleostei) from the upper Miocene of Argentina. J. Vert. Paleo.29(2), 350–358 (2009).
de Lapparent de Broin, F., Bocquentin, J. & Negri, F. R.Gigantic turtles (Pleurodira, Podocnemididae) from the late Miocene-early Pliocene of southwestern Amazon. Bull. Inst. Fr. Etu. And.22(3), 657–670 (1993).
Huber, D. R., Dean, M. N. & Summers, A. P.Hard prey, soft jaws and the ontogeny of feeding mechanics in the spotted ratfish, Hydrolagus colliei. J. R. Soc. Interface5, 941–953 (2008).
Kolmann, M. A. & Huber, D. R.Scaling of feeding biomechanics in the horn shark Heterodontus francisci: ontogenetic constraints on durophagy. Zoology112, 351–361 (2009).
Wainwright, P. C., Bellwood, D. R., Westneat, M. W., Grubich, J. R. & Hoey, A. S.A functional morphospace for the skull of labrid fishes: patterns of diversity in a complex biomechanical system. Biol Linn J. Soc.82, 1–25 (2004).
Wroe, S., McHenry, C. & Thomason, J.Bite Club: comparative bite force in big biting mammals and the prediction of predatory behavior in fossil taxa. Proc. Roy. Soc. Lond. Ser. B272, 619–625 (2005).
Whitenack, L. B., Simkins, D. C. Jr. & Motta, P. J. Biology Meets Engineering: The structural mechanics of fossil and extant shark teeth. J. Morph.272, 169–179 (2011).
Anderson, P. S. L., Gill, P. G. & Rayfield, E. J.Modeling the effects of cingula structure on strain patterns and potential fracture in tooth enamel. J. Morph.272, 50–65 (2011).
Whitenack, L. B., Simkins, D. C., Motta, P. J., Hirai, M. & Kumar, A.Young's modulus and hardness of shark tooth biomaterials. Arch. Oral. Biol.55, 203–209 (2010).
Dumont, E. R., Grosse, I. R. & Slater, G. J.Requirements for comparing the performance of finite element models of biological structures. J. Theor. Biol.256, 96–103 (2009).
We would like to thank our Brazilian guides for their service,
and the Kararo and Arara Tribes of the Xingu River for their
hospitality. The expedition was funded by a National Geographic
Expeditions Council Grant (#EC0463-10) to J.R. Grubich. Research support
was provided by National Geographic Development Funds x20469-03-1008
& a WKU Faculty Scholarship Award (#10-7072) to S. Huskey, as well
as a Field Museum of Natural History Collection Research Grant and WKU
Travel Grant to J.R. Grubich.
Department of Biology American University in Cairo, New Cairo, Egypt 11835
Justin R. Grubich
Division of Fishes The Field Museum of Natural History, Chicago, IL 60605
Justin R. Grubich
Biology Department Western Kentucky University, Bowling Green, KY 42101
Justin R. Grubich &
Steve Huskey
Department of Biology, University of Washington, Seattle, WA 98195
Stephanie Crofts
Department of Biological Sciences, George Washington University, Washington, DC 20052
Guillermo Orti
Instituto Nacional de Pesquisas da Amazônia (INPA) Manaus-AM, Brazil 69011-970
Jorge Porto
Contributions
JRG was responsible for manuscript composition. SH and JRG were
responsible for piranha jaw functional morphology interpretation as well
as bite performance and bite simulation protocols and analyses. JRG
calculated serrasalmid allometry, MandibLever v3.5 results, and BFQ
calculations, as well as 3D digital reconstruction of serrasalmid
premaxillary teeth. SH was responsible for bite gauge construction and
material tester access, as well as skeleton construction. SC developed
the Finite Element Analysis of premaxillary teeth using 3D digital tooth
vector algorithms and generated Von Mises Stress and Total Strain
Energy data. GO was responsible for species identification and data
collection, as well as phylogenetic justification and analysis of
serrasalmid relationships. JP procured INPA fish collection permits,
acted as liaison with indigenous tribes, and assisted in data collection
and interpretation.
Competing financial interests
The authors declare no competing financial interests.
