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Abstract

Estimates of body mass often represent the founding assumption on which bio-mechanical and macroevolutionary hypotheses are based. Recently, a scaling equation was applied to a newly discovered titanosaurian sauropod dinosaur (Dreadnoughtus), yielding a 59 300 kg body mass estimate for this animal. Herein, we use a modelling approach to examine the plausibility of this mass estimate for Dreadnoughtus. We find that 59 300 kg for Dreadnoughtus is highly implausible and demonstrate that masses above 40 000 kg require high body densities and expansions of soft tissue volume outside the skeleton several times greater than found in living quadrupedal mammals. Similar results from a small sample of other archosaurs suggests that lower-end mass estimates derived from scaling equations are most plausible for Dreadnoughtus, based on existing volumetric and density data from extant animals. Although volumetric models appear to more tightly constrain dinosaur body mass, there remains a clear need to further support these models with more exhaustive data from living animals. The relative and absolute discrepancies in mass predictions between volumetric models and scaling equations also indicate a need to systematically compare predictions across a wide size and taxonomic range to better inform studies of dinosaur body size.
rsbl.royalsocietypublishing.org
Research
Cite this article: Bates KT, Falkingham PL,
Macaulay S, Brassey C, Maidment SCR. 2015
Downsizing a giant: re-evaluating
Dreadnoughtus body mass. Biol. Lett. 11:
20150215.
http://dx.doi.org/10.1098/rsbl.2015.0215
Received: 18 March 2015
Accepted: 18 May 2015
Subject Areas:
biomechanics, evolution, palaeontology
Keywords:
Dreadnoughtus, body mass, modelling,
scaling equations
Author for correspondence:
Karl T. Bates
e-mail: k.t.bates@liverpool.ac.uk
Electronic supplementary material is available
at http://dx.doi.org/10.1098/rsbl.2015.0215 or
via http://rsbl.royalsocietypublishing.org.
Palaeontology
Downsizing a giant: re-evaluating
Dreadnoughtus body mass
Karl T. Bates1, Peter L. Falkingham2, Sophie Macaulay1, Charlotte Brassey3
and Susannah C. R. Maidment4
1
Department of Musculoskeletal Biology, University of Liverpool, Duncan Building, Daulby Street,
Liverpool L69 3GE, UK
2
School of Natural Sciences and Psychology, Liverpool John Moores University, James Parsons Building,
Bryon Street, Liverpool L3 3AF, UK
3
Faculty of Life Sciences, University of Manchester, Manchester M13 9PL, UK
4
Department of Earth Science and Engineering, Imperial College, South Kensington, London SW7 2AZ, UK
PLF, 0000-0003-1856-8377
Estimates of body mass often represent the founding assumption on which bio-
mechanical and macroevolutionary hypotheses are based. Recently, a scaling
equation was applied to a newly discovered titanosaurian sauropod dinosaur
(Dreadnoughtus), yielding a 59 300 kg body mass estimate for this animal.
Herein, we use a modelling approach to examine the plausibility of this mass
estimate for Dreadnoughtus. We find that 59 300 kg for Dreadnoughtus is
highly implausible and demonstrate that masses above 40 000 kg require
high body densities and expansions of soft tissue volume outside the skeleton
several times greater than found in living quadrupedal mammals. Similar
results from a small sample of other archosaurs suggests that lower-end mass
estimates derived from scaling equations are most plausible for Dreadnoughtus,
based on existing volumetric and density data from extant animals. Although
volumetric models appear to more tightly constrain dinosaur body mass, there
remainsa clear need tofurther supportthese models with more exhaustive data
from living animals. The relative and absolute discrepancies in mass pre-
dictions between volumetric models and scaling equations also indicate a
need to systematically compare predictions across a wide size and taxonomic
range to better inform studies of dinosaur body size.
1. Introduction
Sauropod dinosaurs include the largest terrestrial animals to have ever evolved,
and mass properties are regarded as a crucial component of their functional,
behavioural and evolutionary dynamics [1]. Recently, Lacovara et al. [2] descri-
bed a gigantic, near-complete titanosaurian sauropod, Dreadnoughtus schrani,
from Argentina. These authors used a scaling relationship between long bone
(femoral plus humeral) circumference and body mass [3] to derive a mass esti-
mate of 59 300 kg for the holotype of Dreadnoughtus. This scaling equation is
well supported statistically in living tetrapods and to date has been used to esti-
mate the body mass of extinct taxa to facilitate studies of physiology and growth
(e.g. [4]) and macroevolutionarydynamics [1]. However, the mass estimate seems
high given that in overall skeletal proportions Dreadnoughtus only marginally
exceeds those of near-complete specimens of other sauropods (e.g. Apatosaurus
and Giraffatitan) whose masses have been estimated at 25 –35 000 kg by various
methods (e.g. [3,5]). In this paper, we use a digital three-dimensional skeletal
model and volumetric reconstructions to directly examine the plausibility of the
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59 300 kg mass estimate for Dreadnoughtus,andsubsequently
comment upon the use of scaling equations to estimate dinosaur
body mass.
2. Material and methods
A digital model of the Dreadnoughtus skeleton from Lacovara et al.
[2] was used as a basis for a three-dimensional volumetric model
(figure 1). For comparative purposes, we also modelled six
extant taxa (three birds, two crocodilians and one lizard) and
two other large sauropods using identical methods: Giraffatitan
brancai, based on a laser scan of MB (Museum fu
¨r Naturkunde,
Berlin, Germany) SII from our previous study [5], and Apatosaurus
louisae, based on a new three-dimensional model of CM (Carnegie
Museum, USA) 3018 generated using photogrammetry [6]. Each
three-dimensionalskeletal model was posed in a standard ‘neutral
posture, with the tail and neck extending horizontally and the
limbs in a fully extended, vertical position (figure 1). Models
were then divided into the following body segments: head, neck,
‘trunk’ (thorax and limb girdles), tail, thigh, shank, foot, humerus,
forearm and hand.
The holotype of Dreadnoughtus is missing most of the cervical
vertebrae, as well the manus, skull and distal tip of the tail. Our
convex hulling approach [5] to volumetric reconstruction involves
tight-fitting three-dimensional convex polygons to each body seg-
ment. As the extent of an object’s convex hull is dictated solely by
its geometric extremes, we were able to minimize the amount of
skeletal reconstruction in our model (electronic supplementary
material, figure S1). For the hand and skull, we used photo-
grammetric models of these elements from Rapetosaurus (FMNH
PR 2209), another titanosaur, and re-scaled them using the recon-
struction in Lacovara et al. (fig. 2 in [2]). To allow convex hulling to
connect the ‘trunk’ and neck segments, we duplicated the ninth
cervical vertebra preserved in the specimen and placed its pos-
terior surface above the most anterior point of pectoral girdle at
a height consistent with the position of the preserved dorsal ver-
tebrae. An additional 10% was added to the distal tail using the
reconstruction of Lacovara et al. [2] as a guide (electronic sup-
plementary material, figure S1). In the electronic supplementary
material, we provide extensive sensitivity tests of our skeletal
(a)
(b)
(d)
(c)
Figure 1. Dreadnoughtus three-dimensional skeletal model and the (a) convex hull, (b) plus 21%, (c) maximal and (d) scaling equation mass volumetric recon-
structions in lateral, oblique and aerial views. Black structures are respiratory volumes. (Online version in colour.)
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reconstruction procedure (electronic supplementary material,
figures S1– S8).
The minimum convex hull volume for each skeletal body seg-
ment was calculated using the MATLAB (www.mathworks.com)
qhull command [5,8]. The total minimum convex hull volume pro-
vides the minimum volume estimate for each animal, and a
baseline for our sensitivity analysis in which we generated three
further models. In the first model, the minimal convex hulls were geo-
metrically expanded by 21%, following a previous study in which
live body mass was estimated to have been on average 21% greater
than that calculated from minimum convex hulls for a range of
extant mammals [5]. We subsequently generated a ‘maximal mass
model’ in which the volume of the trunk segment was increased by
50% and those of all other segments by 100%. Finally, we expanded
the minimum convex hull model of Dreadnoughtus by the amount
required to match the total body masses predicted by the scaling
equation of [3]. For the sauropod models, body segments were
given an initial density of 1000 kg m
23
.Zero-densityrespiratory
structures in the head, neck and ‘trunk’ segments were reconstructed
and the volumes of these structures subtracted from their overall seg-
ment volume, as in previous volumetric studies of dinosaurs [7,9,10].
Homogeneous body densities were used for the extant taxa, based on
published values for crocodiles and chickens [10].
3. Results
The convex hull volume reconstruction of Dreadnoughtus
results in a total body volume of 26.910 m
3
(figure 1aand
table 1). Expanding this minimum convex hull volume by
21% raises the whole-body volume to 32.534 m
3
(figure 1b),
while the volume of our maximal model is 43.016 m
3
(figure 1c). Deducting the volume of our reconstructed
Table 1. Mass property data for convex hull reconstructions of Dreadnoughtus,Apatosaurus and Giraffatitan, and summary of whole-body mass data from
different model iterations.
Dreadnoughtus Apatosaurus Giraffatitan
convex hull
volume
(m
3
)
density
(kg m
23
)
mass
(kg)
volume
(m
3
)
density
(kg m
23
)
mass
(kg)
volume
(m
3
)
density
(kg m
23
)
mass
(kg)
body segments
head 0.033 1000 33.49 0.02 1000 23.46 0.06 1000 59.45
neck 3.110 1000 3109.99 2.62 1000 2615.16 2.46 1000 2461.00
trunk 20.382 1000 20 381.96 20.12 1000 20 187.65 19.85 1000 19 850.92
tail 1.011 1000 1011.35 1.86 1000 1861.20 0.78 1000 774.76
humerus 0.186 1000 186.08 0.23 1000 232.34 0.30 1000 298.78
forearm 0.097 1000 97.36 0.10 1000 103.01 0.16 1000 160.67
hand 0.024 1000 24.11 0.03 1000 25.96 0.09 1000 85.98
humerus 0.186 1000 186.08 0.28 1000 275.31 0.30 1000 298.78
forearm 0.097 1000 97.36 0.10 1000 103.01 0.16 1000 160.67
hand 0.024 1000 24.11 0.03 1000 25.96 0.09 1000 85.98
thigh 0.246 1000 246.13 0.35 1000 351.27 0.29 1000 294.19
shank 0.110 1000 109.86 0.21 1000 208.57 0.19 1000 193.06
foot 0.042 1000 41.91 0.08 1000 84.62 0.04 1000 35.69
thigh 0.246 1000 246.13 0.35 1000 351.27 0.29 1000 294.19
shank 0.110 1000 109.86 0.21 1000 208.57 0.19 1000 193.06
foot 0.042 1000 41.91 0.08 1000 84.62 0.04 1000 35.69
axial total 25.50 1000 24 536.80 24.62 1000 24 687.47 23.15 1000 23 146.13
hind limb total 0.796 1000 795.80 1.289 1000 1288.92 1.046 1000 1045.88
fore limb total 0.614 1000 615.09 0.722 1000 722.62 1.092 1000 1090.87
whole body 26.91 1000 25 947.68 26.63 1000 26 699.01 25.28 1000 25 282.88
respiratory structures
head 0.003 1000 3.43 0.001 1000 0.99 0.0036 1000 3.60
neck 4.30 1000 4303.67 4.60 1000 4602.86 5.00 1000 5000.39
trunk 0.49 1000 486.48 0.29 1000 291.95 0.33 1000 332.54
model iteration
minimum
convex hull
26.91 821.9 22 117.98 26.63 818.8 21 803.21 25.284 788.8 19 946.35
plus 21% model 32.53 852.7 27 741.68 32.26 850.5 27 363.56 30.54 825.2 25 204.65
maximal model 43.02 888.6 38 224.57 43.08 886.4 38 187.23 40.40 867.9 35 060.42
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respiratory structures from each of these models yields total
body masses of 22 117, 27 741 and 38 225 kg for the three
model iterations. These data and data from equivalent
models of Apatosaurus and Giraffatitan (figure 2a,b)areshown
in table 1, while the data from extant taxa are tabulated in the
electronic supplementary material (tables S1– S6, and figures
S8 and S9). Convex hull volumes are available in the electronic
supplementary material.
4. Discussion and conclusion
The mass of Dreadnoughtus was estimated at 59 300 kg using
the raw bivariate predictive equation of Campione & Evans
[3]. The masses of our three volumetric reconstructions
of Dreadnoughtus (figure 1acand table 1) are equivalent to
37, 47 and 64% of the 59 300 kg scaling equation mass.
The ‘average per cent prediction error’ from the bi-variate
equation gives a minimum mass of 44 095 kg (5780 kg or 15%
higher than our ‘maximal’ model) and a maximum mass of
74 487 kg (36 262 kg or 95% higher than our ‘maximal’
model). The ‘95% prediction interval’ from the equation
yields a range of 32 000– 109 000 kg for Dreadnoughtus, which
overlaps with model estimates (figure 2).
Convex hulling provides a close, objective approximation of
the body volume defined by a skeleton alone [5,8]. A volume
2.38 times larger than that of our convex hull model is required
for Dreadnoughtus to achieve the mean or ‘best-estimate’ scaling
equation mass of 59 300 kg, using our estimates for the size of
respiratory structures (figure 1d). This represents an expansion
more than 6.5 times greater than the average value found in a
sample of quadrupedal mammals spanning major taxonomic
groups [5]. This 2.38 times expanded model (figure 1d)hasa
bulk density of 925 kg m
23
, which is higher than any presen-
tly published estimate for sauropods (range 791– 900 kg m
3
;
electronic supplementary material, table S7). If lower-end
estimates of 800 kg m
23
for sauropod density [7] are correct,
then achieving a body mass of 59 300 kg for Dreadnoughtus
would require body and respiratory volumes of 74.125 m
3
and 14.825 m
3
, respectively, the latter representing a 310%
expansion of our respiratory volumes (figure 1). Filling the
entire ribcage with a zero-density respiratory structure (elec-
tronic supplementary material, figure S7), which is obviously
highly implausible, only produces a 212% increase in respirat-
ory volume. It is clear from our model that bulk densities as
low or approaching 800 kg m
3
cannot be reconciled with a
total body mass of 59 300 kg given the skeletal proportions of
Dreadnoughtus and the space available within the ribcage for
low-density respiratory structures.
Comparison of mass predictions from volumetric recon-
structions of near-complete skeletons of Apatosaurus and
Giraffatitan (figure 2) to the mean scaling equation masses, pro-
duces a qualitatively similar result: scaling equation mass
predictions exceed those of our maximal models (figure 2c,d).
The disparity between the two approaches increases further if
the whole-body densities of these models are set to lower-end
20 000
40 000
60 000
120 000
80 000
100 000
body mass (kg)
Apatosaurus DreadnoughtusGiraffatitanApatosaurus DreadnoughtusGiraffatitan
95PI
PPE
95PI
PPE
95PI
PPE
95PI
PPE
95PI
scaling equation convex hull model plus 21% model maximal model
PPE
95PI
PPE
(a)(b)
(d)(c)
Figure 2. Comparison of skeletal proportions and convex hull volumes for Apatosaurus (top), Dreadnoughtus (middle) and Giraffatitan (bottom) in (a) dorsal and
(b) lateral views. Comparison of mass predictions from the models in this study to masses derived from the scaling equation [2], with (c) model mass and density
calculated using reconstructed zero-density respiratory structures, and (d) density artificially set to 800 kg m
23
[7]. The positive error bar on our maximal models
represents the mass predicted by expanding convex hull volumes by the highest exponent (1.91) for mammals [5] and archosaurs to date. The ‘PPE’ error bars on
scaling equation outputs represent the average ‘per cent prediction error’, whereas ‘95PI’ error bars represent the ‘95% prediction interval’.
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estimates for sauropods (800 kg m
23
[7]) rather than predicting
density by inclusion of respiratory structures. In the case of
both Apatosaurus and Giraffatitan, there is clear overlap between
the lowest scaling equation estimates and our maximal models,
although as with Dreadnoughtus there remains no overlap
between the lowest scaling equation masses and those derived
from the upper bounds of the mammalian convex hull
expansion exponent (figure 2).
Convex hull volumes for extant taxa produced here
required scaling exponents of between 1.18 and 1.91 (electronic
supplementary material, tables S1– S6, and figures S8 and S9)
to reach actual measured body masses, with three animals
(American alligator 1.69; guineafowl 1.91; leghorn chicken
1.87) requiring exponents greater than that applied in our
‘maximal’ models (figure 1). However, increasing convex
hull volume by 2.38, as required for our reconstruction of
Dreadnoughtus to reach the mean scaling equation mass, results
in substantial mass overestimates for all modelled extant
taxa (23– 102% overestimates; see electronic supplementary
material, tables S1–S6).
Our analysis emphasizes a number of important points that
should be considered in future studies. Firstly, it is vital
that uncertainties and likely error magnitudes are explicitly
acknowledged in mass estimates derived from all methods,
including scaling equations. Our analysis also reveals that the
higher range estimates predicted by bivariate scaling equations
[3] appear to be highly incompatible with volumetric models
that are based directly on currently available volume and den-
sity data from living vertebrates ([5]; electronic supplementary
material, tables S1–S6). Indeed, in the case of Dreadnoughtus,
the mean, and perhaps even some lower-end, scaling equa-
tion estimates appear to be implausible based on current
data (figures 1 and 2). The high scaling equation mass for
Dreadnoughtus also appears to result in a discrepancy in relative
mass predictions between the modelled sauropods; our convex
hull volumes (which providea close approximation of the body
volume defined by the preserved skeleton) of Apatosaurus
and Giraffatitan represent 0.9 and 0.985 that of Dreadnoughtus,
which appears congruent with the overlap in gross linear
body proportions (electronic supplementary material,
figure S11). By contrast, mean scaling equation mass predic-
tions for Apatosaurus and Giraffatitan are 0.57 and 0.70 that of
Dreadnoughtus (figure 2). While differences in skeletal : extra-
skeletal dimensions should be expected [3], even in relatively
closely related taxa (electronic supplementary material, tables
S1–S6) it seems unlikely that differences in skeletal proportions
of these three sauropods (figure 2; electronic supplemen-
tary material, figure S11) are sufficient to account for the
20–25 000 kg difference in body mass predicted by the scaling
equation. Thus, even physiological and macroevolutionary
studies that use relative mass values or distribute taxa into dis-
crete mass ‘categories’ based on scaling equation estimates
should take the maximum range of values or error inherent
in these equations into account.
Recently, a similar pattern of divergence between volu-
metric and linear-based mass estimates was found for an
exceptionally complete Stegosaurus skeleton [8]. The authors
attributed this discrepancy to the ontogenetic status of the
individual. Certain skeletal features may indicate that the
Dreadnoughtus holotype was still growing at the time of
death [2]. As an organism’s body proportions change with
age, the application of a scaling equation derived from
modern adult skeletons to the limb bones of a sub- or
young adult may be erroneous. At least some of the inconsis-
tency we find here between mass estimation techniques may
therefore be due to the ontogenetic stage of the specimen.
Given the absence of confirmed ‘adult’ skeletal material for
Dreadnoughtus however, it would be challenging to account
for this phenomenon.
Estimating the mass of extinct animals is challenging [3,5,
8–10]. By directly using the determinates of mass (volume
and density) and maximizing skeletal evidence, volumetric
approaches allow inherent uncertainties in mass predictions to
be explicitlyassessed (figures 1 and 2) and plausiblelimits estab-
lished based on data and models of extant taxa. Our analysis
reveals the importanceof extending current analyses of dinosaur
body mass i n two ways; first and fo remost by addition of further
volumetric and density data on living taxa in order to more
tightly constrain maximum plausible values for extinct animals.
Second, a systematic comparison of dinosaur mass predictions
from modelling and scaling equations, across a wide taxonomic
and size range, is needed to identify and explain discrepancies
between the two approaches (figure 2). Such a study would
not only lead to more informed estimates of dinosaur body
mass, but could also shed light on musculoskeletal adaptations
for large body size in different dinosaur lineages.
Data accessibility. Convex hull models are downloadable from Dryad
(http://dx.doi.org/10.5061/dryad.t5606).
Authors’ contributions. K.T.B., S.C.R.M., C.A.B. and P.L.F. designed the
experiments; K.T.B., S.M. and P.L.F. collected the data; K.T.B.,
C.A.B, S.C.R.M. and S.M. analysed the data; all authors contributed
to the manuscript.
Competing interests. The authors declare that they have no competing
interests.
Funding. K.T.B. and S.M. acknowledge funding from the Adapting to
the Challenges of a Changing Environment (ACCE) NERC doctoral
training partnership.
Acknowledgements. Nicola
´s Campione and two other anonymous
reviewers are thanked for their comments, which greatly improved
the paper.
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... In order to reconstruct different palaeobiological aspects of sauropods and of other extinct terrestrial quadrupeds, the estimation of body mass represents a principal measure of body size to analyse palaeoecological implications of the faunal composition of ancient ecosystems (Campione & Evans, 2012). In recent years, different palaeontological studies have focused on developing alternative methodologies to approximate the body mass of extinct vertebrates, including gigantic theropod and sauropod dinosaurs (Campione & Evans, 2012;Sellers et al., 2012;Bates et al., 2015Bates et al., , 2016. In particular, Campione & Evans (2012) suggested a new scaling method to relate stylopodial circumferences with body mass (BM), using the humeral and femoral circumferences (CH and F, respectively) of different quadrupedal taxa. ...
... Three-dimensional skeletal reconstructions are now also widely used to approximate the body volume of different sauropod taxa (Sellers et al., 2012;Bates et al., 2015Bates et al., , 2016Carballido et al., 2017), representing an alternative model to the scaling and quadratic approaches when the femoral and humeral circumferences are not available. However, volumetric analyses are clearly subject to different uncertainties related to the amount of reconstructed soft tissue (Campione & Evans, 2012;Carballido et al., 2017), and large discrepancies from the scaling model have been detected for several sauropod body mass estimations (Bates et al., 2015;Carballido et al., 2017). ...
... Three-dimensional skeletal reconstructions are now also widely used to approximate the body volume of different sauropod taxa (Sellers et al., 2012;Bates et al., 2015Bates et al., , 2016Carballido et al., 2017), representing an alternative model to the scaling and quadratic approaches when the femoral and humeral circumferences are not available. However, volumetric analyses are clearly subject to different uncertainties related to the amount of reconstructed soft tissue (Campione & Evans, 2012;Carballido et al., 2017), and large discrepancies from the scaling model have been detected for several sauropod body mass estimations (Bates et al., 2015;Carballido et al., 2017). ...
Article
Osteological knowledge of the sauropod dinosaur Ligabuesaurus leanzai is increased by the description of new postcranial elements assigned to the holotype MCF-PVPH-233. Furthermore, a newly referred specimen, MCF-PVPH-228, is recognized after a detailed revision of the abundant sauropod material collected from the Lohan Cura Formation outcrops in the Cerro de los Leones locality (southern Neuquén Basin, Patagonia, Argentina). Recent laboratory preparation and fieldwork allowed us to recognize several new morphological features of the pectoral and pelvic girdles and the cervical and caudal anatomy. Thus, a new diagnosis of Ligabuesaurus is proposed that includes new autapomorphies and a unique combination of features. A phylogenetic analysis based on this new material recovers Ligabuesaurus as a non-titanosaurian somphospondylan, more derived than Sauroposeidon. Therefore, we discuss the palaeobiogeographical implications for the diversification and distribution of South American somphospondylans, especially in the Neuquén Basin, which are closely related to the early stages of evolution of Titanosauria. In this context, Ligabuesaurus represents one of the more complete Early Cretaceous Titanosauriformes and the earliest non-titanosaurian somphospondylan of South America. Finally, the new information on Ligabuesaurus contributes not only to reconstruction of the sauropod faunal composition of south-western Gondwana, but also sheds light on the early stages and emergence of titanosaurians.
... Patagotitan mayorum represents one of the most complete giant titanosaurs described and its body mass has been estimated with various methods (i.e., scaling equations and volumetric reconstruction; see also Campione and Evans, 2012;Bates et al., 2015Bates et al., , 2016Carballido et al., 2017;Otero et al., 2019;but see McPhee et al., 2018;Chapelle et al., 2019 for an alternative quantitative method). In this section we discuss apomorphies of Patagotitan in the context of the evolution of Sauropoda and their utility as different character states to be used in future phylogenetic analysis. ...
... The original estimate of body mass in Patagotitan was about 70 tons (Carballido et al., 2017), using the scaling equation based on stylopodial circumferences proposed by Campione and Evans (2012). That estimate posited Patagotitan as the largest terrestrial animal ever described, largely surpassing the body mass of other giant sauropods, such as Apatosaurus louisae (∼42 tons), Giraffatitan (34 tons), Alamosaurus (∼35 tons), Futalognkosaurus (∼38 tons), and Dreadnoughtus (∼60 tons) (Benson et al., 2014;Bates et al., 2015). Estimates using volumetric reconstructions based on 3D models also yielded Patagotitan (∼44 tons) at the top of the list of heaviest sauropod dinosaurs (Dreadnoughtus, ∼27 tons; Apatosaurus ∼26 tons; Benson et al., 2014;Bates et al., 2015). ...
... That estimate posited Patagotitan as the largest terrestrial animal ever described, largely surpassing the body mass of other giant sauropods, such as Apatosaurus louisae (∼42 tons), Giraffatitan (34 tons), Alamosaurus (∼35 tons), Futalognkosaurus (∼38 tons), and Dreadnoughtus (∼60 tons) (Benson et al., 2014;Bates et al., 2015). Estimates using volumetric reconstructions based on 3D models also yielded Patagotitan (∼44 tons) at the top of the list of heaviest sauropod dinosaurs (Dreadnoughtus, ∼27 tons; Apatosaurus ∼26 tons; Benson et al., 2014;Bates et al., 2015). In the light of the modified scaling equation introduced by Campione (2017) and re-measuring the long bone circumference for the humeri of Patagotitan recently prepared (MPEF-PV 3395 and 3396), the estimated body mass ranges between 42.5-71.4 ...
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Its huge size, excellent preservation, and completeness make Patagotitan mayorum a unique opportunity to explore the anatomy, paleobiological, and phylogenetic aspects linked to gigantism within Sauropoda. In this regard, we describe the appendicular skeleton of this titanosaurian species from the late Albian-aged Cerro Barcino Formation of Chubut Province, Argentina. The diagnosis of Patagotitan mayorum is revised, increasing the number of identified autapomorphies (i.e., lateral surface of the scapular blade with two divergent crests; anterior surface of proximal humerus with paired muscle scars; combined bulges on the deltopectoral area of the humerus; ischium with well-developed and sharp ridge projecting from the ischial tuberosity to the distal blade). Several diagnostic characters of this species correspond to osteological correlates associated to appendicular musculature (e.g., Mm. deltoideus scapularis, deltoideus clavicularis, and teres major; M. coracobrachialis; Mm. supracoracoideus/deltoideus clavicularis and latissimus dorsi; Mm. flexor tibialis 3 and adductor femoris 2), which we discuss in the context of sauropod evolution. In the light of a modification of the scaling equation previously proposed and adjusting the long bone circumference for the humeri of Patagotitan, a new body mass estimate of this species ranges between 42-71 tons, with a mean value of 57 tons. Although considerably less than the value obtained by the original linear equation, the corrected quadratic equation used here provides a mean body mass estimate that is more consistent with those derived from volumetric reconstructions of Patagotitan.
... Body mass estimation is a fraught exercise for fragmentary skeletons (Bates et al., 2015;Bates et al., 2009;Bates et al., 2016;Campione & Evans, 2012;Campione & Evans, 2020;Paul, 2019). Recent body mass estimates of giant sauropods (Carballido et al., 2017;Lacovara et al., 2014) using humeral and femoral circumferences (Benson et al., 2014;Campione & Evans, 2012;Campione & Evans, 2020) have come under scrutiny and are shown to be implausible or inaccurate (Bates et al., 2015;Otero, Carballido & Moreno, 2020;Paul, 2019). ...
... Body mass estimation is a fraught exercise for fragmentary skeletons (Bates et al., 2015;Bates et al., 2009;Bates et al., 2016;Campione & Evans, 2012;Campione & Evans, 2020;Paul, 2019). Recent body mass estimates of giant sauropods (Carballido et al., 2017;Lacovara et al., 2014) using humeral and femoral circumferences (Benson et al., 2014;Campione & Evans, 2012;Campione & Evans, 2020) have come under scrutiny and are shown to be implausible or inaccurate (Bates et al., 2015;Otero, Carballido & Moreno, 2020;Paul, 2019). However, a recent review of these inaccuracies has suggested that the estimation methods themselves can be reconciled, albeit with reservations when dealing with particular groups of tetrapods, like giant sauropods (Campione & Evans, 2020). ...
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A new giant sauropod, Australotitan cooperensis gen. et sp. nov., represents the first record of dinosaurs from the southern-central Winton Formation of the Eromanga Basin, Australia. We estimate the type locality to be 270–300 m from the base of the Winton Formation and compare this to the semi-contemporaneous sauropod taxa, Diamantinasaurus matildae Hocknull et al., 2009, Wintonotitan wattsi Hocknull et al., 2009 and Savannasaurus elliottorum Poropat et al., 2016. The new titanosaurian is the largest dinosaur from Australia as represented by osteological remains and based on limb-size comparisons it reached a size similar to that of the giant titanosaurians from South America. Using 3-D surface scan models we compare features of the appendicular skeleton that differentiate Australotitan cooperensis gen. et sp. nov. as a new taxon. A key limitation to the study of sauropods is the inability to easily and directly compare specimens. Therefore, 3-D cybertypes have become a more standard way to undertake direct comparative assessments. Uncoloured, low resolution, and uncharacterized 3-D surface models can lead to misinterpretations, in particular identification of pre-, syn- and post-depositional distortion. We propose a method for identifying, documenting and illustrating these distortions directly onto the 3-D geometric surface of the models using a colour reference scheme. This new method is repeatable for researchers when observing and documenting specimens including taphonomic alterations and geometric differences. A detailed comparative and preliminary computational phylogenetic assessment supports a shared ancestry for all four Winton Formation taxa, albeit with limited statistical support. Palaeobiogeographical interpretations from these resultant phylogenetic hypotheses remain equivocal due to contrary Asian and South American relationships with the Australian taxa. Temporal and palaeoenvironmental differences between the northern and southern-central sauropod locations are considered to explain the taxonomic and morphological diversity of sauropods from the Winton Formation. Interpretations for this diversity are explored, including an eco-morphocline and/or chronocline across newly developed terrestrial environments as the basin fills.
... The next step was to apply a specific density to the living tissue to obtain an estimate of the body mass from the obtained volume. In particular, Larramendi (2016) proposed a specific average body gravity in extinct proboscideans of 0.99 to 1.01; in several contributions (e.g., Alexander, 1985Alexander, , 1989Gunga et al., 1995;Henderson, 1999;Hurlburt, 1999;Hutchinson et al., 2007;Bates et al., 2009Bates et al., , 2015Romano et al., 2021) the density of water, i.e., 1 kg/1,000 cm 3 , has been used as the most plausible value to calculate body mass in extinct vertebrates. According to Gunga et al. (2007), rhinoceros has the highest density of land mammals, equal to 1.15 kg/1,000 cm 3 . ...
... As stressed in the text we prefer the volumetric method for body mass estimate, since the classic regression formulas based on long bone dimensions can lead to substantial under-or overestimation of the body weight of extinct tetrapods (see Sellers et al., 2012;Bates et al., 2015;Brassey et al., 2015;Larramendi, 2016;Romano and Manucci, 2019;Romano and Rubidge, 2019a;Romano et al., 2021). It has been empirically shown that the discrepancy between estimates obtained from regression formulas are greater when applied to clades phylogenetically distant from those used to construct the dataset (Brassey, 2016;Romano and Manucci, 2019;Romano and Rubidge, 2019a), and in particular to taxa with a "primitive" sprawling posture characterized by excessively "overbuilt" long bones (sensu Romano, 2017b;Romano and Rubidge, 2019b). ...
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Pareiasaurs (Amniota, Parareptilia) were characterized by a global distribution during the Permian period, forming an important component of middle (Capitanian) and late Permian (Lopingian) terrestrial tetrapod biodiversity. This clade includes some of the first large-sized terrestrial herbivores, playing a fundamental role in the structure of middle and late Permian biodiversity and ecosystems. Despite their important ecological role and relative abundance around the world, our general knowledge of the biology of these extinct tetrapods is still quite limited. In this contribution we provide a possible in-vivo reconstruction of the largest individual of the species Scutosaurus karpinskii and a volumetric body mass estimate for the taxon, considering that body size is one of the most important biological aspects of organisms. The body mass of Scutosaurus was calculated using a 3D photogrammetric model of the complete mounted skeleton PIN 2005/1537 from the Sokolki locality, Arkhangelsk Region, Russia, on exhibit at the Borissiak Paleontological Institute, Russian Academy of Sciences (Moscow). By applying three different densities for living tissues of 0.99, 1 and 1.15 Kg/1000 cm3 to the a reconstructed ‘slim’, ‘average’ and ‘fat’ 3D models we obtain an average body mass respectively of 1060, 1160 and 1330 Kg, with a total range varying from a minimum of one ton to a maximum of 1.46 tons. Choosing the average model as the most plausible reconstruction and close to the natural condition, we consider a body mass estimate of 1160 Kg as the most robust value for Scutosaurus, a value compatible with that of a large terrestrial adult black rhino and domestic cow. This contribution demonstrates that barrel-shaped herbivores, subsisting on a high-fibre diet and with a body mass exceeding a ton, had already evolved in the upper Palaeozoic within parareptiles, shedding new light on the structure of the first modern terrestrial ecosystems.
... The uses are varied, with many possibilities yet to be explored, and range from 3D bone scanning to biomechanics, locomotor capabilities, retrodeformation of fossils, muscle reconstruction and body mass estimate (e.g. Gunga et al. 2007Gunga et al. , 2008Bates et al. 2009Bates et al. , 2015Mallison 2010aMallison , 2010bMallison , 2010cHutchinson et al. 2011;Bates and Falkingham 2012;Sellers et al. 2012Sellers et al. , 2017Stevens 2013;Reiss and Mallison 2014;Brassey et al. 2015;Brassey 2016;Vidal and Diaz 2017;Romano and Manucci 2021;Bishop et al. 2021;Romano and Rubidge 2021;Romano et al. 2021aRomano et al. , 2021b. This virtual revolution, even with regard to the most common digital illustration, has not, however, hindered those who continue to use the traditional artistic tools, from painting to manual sculpture, with authors who continue the great paleoartistic tradition that has always accompanied this genre from its origins. ...
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Between the fifteenth and sixteenth centuries, the first naturalistic illustrations appeared in texts and treatises, marking the true and proper passage from simple literary works to real scientific contributions. Since that time, the geo-palaeontological literature and the world of scientific illustrations developed together. For a long time initially the scientist and artist coincided in the same person, until the emergence of the ‘paleoartist’, as a professional devoted to naturalistic representations. Here, we review the fundamental steps of ‘co-evolution’ between advances in scientific knowledge and their representation in ‘paleoart’. The study led to the identification of six principal ‘Genres’; in addition, a subdivision of the history and evolution of ‘paleoart’ into six periods or major ‘eras’ is proposed. The analysis is based on a dataset with a total of 605 authors, considering a time range between the first half of the 18th century up to 2020, with paleoartists from 42 different countries. The relationship between scientist and ‘paleoartist’ has been, and will be in the future, a constructive interaction of ‘reciprocal illumination’, where the questions asked by the artist represent a genuine propellant for the advancement of knowledge and the research itself.
... Most of these are due to the reliability of the skeletal reconstruction and the subjectivity induced by the interpretation of the soft tissue covering the bones. Given the inexistence of preserved bones of the thoracic region of Neoepiblema, a convex hull volumetric approach is unviable for the taxon, though other workers have successfully estimated plausible body mass values based on incomplete skeletons (e.g., Bates et al. 2015;Muller et al. 2020). Nonetheless, until more complete N. acreensis skeletons are discovered, allowing assessment of the complete osteological proportions of this rodent, this remains the best way to perform a volumetric comparison with the estimates based on allometric equations. ...
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In this paper, we study the postcranial morphology (humerus, ulna, innominate, femur, tibia, astragalus, navicular, and metatarsal III) of Neoepiblema, a giant Late Miocene South American rodent, searching for evidence about its paleobiology based on unpublished specimens from Solimões Formation (Upper Miocene, Brazil). The study includes a morphofunctional analysis of the postcranial bones and a comparison with extant and extinct rodents, especially Phoberomys. The morphofunctional analysis of the postcranial bones suggests that Neoepiblema (as well as Phoberomys) would have a crouched forelimb that was not fully extended, with powerful pectoral and triceps musculature, and able to produce movements of pronation/supination and possibly with a hand able to grasp. The combination of characters of the innominate bone, femur, and tibia indicates a predominance of parasagittal movements and a thigh with powerful musculature used during propulsion. In sum, the analyzed postcranial features are consistent with the limb morphology of ambulatory rodents, but with faculty to dig or swim. The sedimentary evidence of the localities in which fossils of neoepiblemids have been found suggests that these rodents lived in wet and water-related environments (near swamps, lakes, and/or rivers). Graphical abstract
... Given the versatility and ongoing development of micro-drones, in this study we tested the use of unmanned aerial vehicles in palaeontology for the 3D acquisition of large skeletons mounted on exhibit in museum structures. In fact, 3D reconstruction of articulated vertebrate skeletons is a very useful tool in palaeontology, allowing, thanks to the help of modern image and video editing technologies, advanced studies in several fields such as locomotion, posture, and biomechanics (e.g., Mallison Bishop et al. 2021), body mass estimation and in vivo restoration of extinct tetrapods (e.g., Gunga et al. 2007Gunga et al. , 2008Bates et al. 2009Bates et al. , 2015Sellers et al. 2012;Brassey et al. 2015;Brassey 2016;Romano and Manucci 2019;Romano and Rubidge 2021;Romano et al. 2021aRomano et al. , 2021b, just to name a few. ...
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Unmanned aerial vehicles (UAVs), have seen tremendous development in the last decade, with numerous applications in civil and research fields. Drones' success, particularly in the field of research, is due to a number of factors, including rapid technological advancement, tool versatility, and prices that are becoming increasingly affordable even for small research groups or individuals. Given the versatility and ongoing development of micro drones, we tested the use of micro-drones in vertebrate palaeontology to reconstruct mounted skeletons using the photogrammetry method. The experiment was carried out on a massive specimen of Mammuthus meridionalis (Nesti 1825) from Madonna della Strada, which is on display at the east bastion of the Spanish Fortress in L'Aquila (Abruzzo, Central Italy), comparing the results with those obtained using the traditional method using a digital camera. Even though both the traditional digital camera and the drone methods produced a high-resolution 3D model of the skeleton, the results obtained, indeed, lead us to consider the use of micro-drones in museum structures as a very interesting and promising new field of application. Drones provide a simple, fast, and non-invasive system for the study, monitoring, and enhancement of cultural heritage in all of its possible manifestations.
... It is extremely quick and mostly objective, assuming accurate re-articulation of the fossil specimen [2]. While the resultant shape is unlikely to visually match the original segment, convex hulling has seen widespread adoption in recent years [22][23][24][25][26][27][28]. This has only occasionally been extended to BSP estimation for subsequent gait analyses [29,30], and the accuracy of this approach is currently unknown. ...
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Obtaining accurate values for body segment parameters (BSPs) is fundamental in many biomechanical studies, particularly for gait analysis. Convex hulling, where the smallest-possible convex object that surrounds a set of points is calculated, has been suggested as an effective and time-efficient method to estimate these parameters in extinct animals, where soft tissues are rarely preserved. We investigated the effectiveness of convex hull BSP estimation in a range of extant mammals, to inform the potential future usage of this technique with extinct taxa. Computed tomography scans of both the skeleton and skin of every species investigated were virtually segmented. BSPs (the mass, position of the centre of mass and inertial tensors of each segment) were calculated from the resultant soft tissue segments, while the bone segments were used as the basis for convex hull reconstructions. We performed phylogenetic generalized least squares and ordinary least squares regressions to compare the BSPs calculated from soft tissue segments with those estimated using convex hulls, finding consistent predictive relationships for each body segment. The resultant regression equations can, therefore, be used with confidence in future volumetric reconstruction and biomechanical analyses of mammals, in both extinct and extant species where such data may not be available.
... As MOZ-Pv 1221 lacks humerus and femur, estimates of its body mass cannot be made using the current main methods (e.g., Campione andEvans, 2012, 2020;Benson et al., 2014;Bates et al., 2016;Campione, 2017;Otero et al., 2019), precluding direct body mass comparisons with other gigantic titanosaurs for which estimates have been made, both by volumetric and scaling methods, such as Dreadnoughtus and Patagotitan (Benson et al., 2014;Bates et al., 2015;Carballido et al., 2017;Campione and Evans, 2020). In comparison to giant titanosaurs, however, the recovered appendicular bones of MOZ-Pv 1221 are larger than any known titanosaur described to date. ...
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One of the most fascinating research topics in the field of sauropod dinosaurs is the evolution of gigantism. In the particular case of Titanosauria, the record of multi-ton species (those exceeding 40 tons) comes mainly from Patagonia. The record of super-sized titanosaur sauropods has traditionally been extremely fragmentary, although recent discoveries of more complete taxa have revealed significant anatomical information previously unavailable due to preservation biases. In this contribution we present a giant titanosaur sauropod from the Candeleros Formation (Cenomanian, circa 98 Ma) of Neuquén Province, composed of an articulated sequence of 20 most anterior plus 4 posterior caudal vertebrae and several appendicular bones. This specimen clearly proves the presence of a second taxon from Candeleros Formation, in addition to Andesaurus, and is here considered one of the largest sauropods ever found, probably exceeding Patagotitan in size. While anatomical analysis does not currently allow us to regard it as a new species, the morphological disparity and the lack of equivalent elements with respect to coeval taxa also prevent us from assigning this new material to already known genera. A preliminary phylogenetic analysis places this new specimen at the base of the clade leading to Lognkosauria, in a polytomy with Bonitasaura. The specimen here reported strongly suggests the co-existence of the largest and middle-sized titanosaurs with small-sized rebbachisaurids at the beginning of the Late Cretaceous in Neuquén Province, indicating putative niche partitioning. This set of extremely large taxa from Patagonia has contributed to a better understanding of the phylogenetic relationships of titanosaurs, revealing the existence of a previously unknown lineage and shedding new light on body mass evolution.
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The density, or specific gravity (SG), of organisms has numerous important implications for their form, function, ecology, and other facets of beings living and dead, and it is especially necessary to apply SG values that are as accurate as practical when estimating their masses which is itself a critical aspect of living things. Yet a comprehensive review and analysis of this notable subject of anatomy has never been conducted and published. This is such an effort, being as extensive as possible with the data on hand, bolstered by some additional observations, and new work focusing on extinct animals who densities are least unknown: pterosaurs and dinosaurs with extensive pneumatic complexes, including the most sophisticated effort to date for a sauropod. Often difficult to determine even via direct observation, techniques for obtaining the best possible SG data are explained and utilized, including observations of floating animals. Neutral SG (NSG) is proposed as the most important value for tetrapods with respiratory tracts of fluctuating volume. SGs of organisms range from 0.08 to 2.6, plant tissues from 0.08 to 1.39, and vertebrates from about 0.75 (some giant pterosaurs) to 1.2 (those with heavy armor and/or skeletons). Tetrapod NSGs tend to be somewhat higher than widely thought, especially those theropod and sauropod dinosaurs and pterosaurs with air-sacs because respiratory system volume is usually measured at maximum inhalation in birds. Also discussed is evidence that the ratio of the mass of skeletons relative to total body mass has not been properly assayed in the past.
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Body mass is a key biological variable, but difficult to assess from fossils. Various techniques exist for estimating body mass from skeletal parameters, but few studies have compared outputs from different methods. Here, we apply several mass estimation methods to an exceptionally complete skeleton of the dinosaur Stegosaurus. Applying a volumetric convex-hulling technique to a digital model of Stegosaurus, we estimate a mass of 1560 kg (95% prediction interval 1082-2256 kg) for this individual. By contrast, bivariate equations based on limb dimensions predict values between 2355 and 3751 kg and require implausible amounts of soft tissue and/or high body densities. When corrected for ontogenetic scaling, however, volumetric and linear equations are brought into close agreement. Our results raise concerns regarding the application of predictive equations to extinct taxa with no living analogues in terms of overall morphology and highlight the sensitivity of bivariate predictive equations to the ontogenetic status of the specimen. We emphasize the significance of rare, complete fossil skeletons in validating widely applied mass estimation equations based on incomplete skeletal material and stress the importance of accurately determining specimen age prior to further analyses.
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Titanosaurian sauropod dinosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era. Several titanosaur species are regarded as the most massive land-living animals yet discovered; nevertheless, nearly all of these giant titanosaurs are known only from very incomplete fossils, hindering a detailed understanding of their anatomy. Here we describe a new and gigantic titanosaur, Dreadnoughtus schrani, from Upper Cretaceous sediments in southern Patagonia, Argentina. Represented by approximately 70% of the postcranial skeleton, plus craniodental remains, Dreadnoughtus is the most complete giant titanosaur yet discovered, and provides new insight into the morphology and evolutionary history of these colossal animals. Furthermore, despite its estimated mass of about 59.3 metric tons, the bone histology of the Dreadnoughtus type specimen reveals that this individual was still growing at the time of death.
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Large-scale adaptive radiations might explain the runaway success of a minority of extant vertebrate clades. This hypothesis predicts, among other things, rapid rates of morphological evolution during the early history of major groups, as lineages invade disparate ecological niches. However, few studies of adaptive radiation have included deep time data, so the links between extant diversity and major extinct radiations are unclear. The intensively studied Mesozoic dinosaur record provides a model system for such investigation, representing an ecologically diverse group that dominated terrestrial ecosystems for 170 million years. Furthermore, with 10,000 species, extant dinosaurs (birds) are the most speciose living tetrapod clade. We assembled composite trees of 614-622 Mesozoic dinosaurs/birds, and a comprehensive body mass dataset using the scaling relationship of limb bone robustness. Maximum-likelihood modelling and the node height test reveal rapid evolutionary rates and a predominance of rapid shifts among size classes in early (Triassic) dinosaurs. This indicates an early burst niche-filling pattern and contrasts with previous studies that favoured gradualistic rates. Subsequently, rates declined in most lineages, which rarely exploited new ecological niches. However, feathered maniraptoran dinosaurs (including Mesozoic birds) sustained rapid evolution from at least the Middle Jurassic, suggesting that these taxa evaded the effects of niche saturation. This indicates that a long evolutionary history of continuing ecological innovation paved the way for a second great radiation of dinosaurs, in birds. We therefore demonstrate links between the predominantly extinct deep time adaptive radiation of non-avian dinosaurs and the phenomenal diversification of birds, via continuing rapid rates of evolution along the phylogenetic stem lineage. This raises the possibility that the uneven distribution of biodiversity results not just from large-scale extrapolation of the process of adaptive radiation in a few extant clades, but also from the maintenance of evolvability on vast time scales across the history of life, in key lineages.
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Recent palaeohistological studies on paramedian osteoderms of aetosaurs revealed the presence of growth lines (lines of arrested growth or LAGs) and a minimal or nonexistent secondary remodelling in the bone matrix of these elements. This feature allows the age of individuals to be estimated through growth line count. In the present contribution we study the growth curve of the South American aetosaur Aetosauroides scagliai. We estimated the age (obtained from LAG counting) and body size (body length and body mass were used as proxies) of different aetosaur specimens in order to reconstruct the growth curve of the South American species. The data obtained for Aetosauroides scagliai were compared with that of other aetosaurs, such as Neoaetosauroides engaeus, Aetosaurus ferratus, Aetobarbakinoides brasiliensis, Typothorax coccinarum and Paratypothorax sp. Our results indicate that, if body length is considered as proxy, all studied aetosaur specimens have a similar or almost identical growth rate. However, important variations arose among aetosaur taxa if body mass is considered as proxy, which would be related to a body morphology ranging from slender (e.g. Aetobarbakinoides brasiliensis) to very wide (Typothorax coccinarum) morphotypes. In comparison with extant pseudosuchians (i.e. crocodylians), Aetosauroides scagliai possesses a relatively lower growth rate.
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Body size is intimately related to the physiology and ecology of an organism. Therefore, accurate and consistent body mass estimates are essential for inferring numerous aspects of paleobiology in extinct taxa, and investigating large-scale evolutionary and ecological patterns in the history of life. Scaling relationships between skeletal measurements and body mass in birds and mammals are commonly used to predict body mass in extinct members of these crown clades, but the applicability of these models for predicting mass in more distantly related stem taxa, such as non-avian dinosaurs and non-mammalian synapsids, has been criticized on biomechanical grounds. Here we test the major criticisms of scaling methods for estimating body mass using an extensive dataset of mammalian and non-avian reptilian species derived from individual skeletons with live weights. Significant differences in the limb scaling of mammals and reptiles are noted in comparisons of limb proportions and limb length to body mass. Remarkably, however, the relationship between proximal (stylopodial) limb bone circumference and body mass is highly conserved in extant terrestrial mammals and reptiles, in spite of their disparate limb postures, gaits, and phylogenetic histories. As a result, we are able to conclusively reject the main criticisms of scaling methods that question the applicability of a universal scaling equation for estimating body mass in distantly related taxa. The conserved nature of the relationship between stylopodial circumference and body mass suggests that the minimum diaphyseal circumference of the major weight-bearing bones is only weakly influenced by the varied forces exerted on the limbs (that is, compression or torsion) and most strongly related to the mass of the animal. Our results, therefore, provide a much-needed, robust, phylogenetically corrected framework for accurate and consistent estimation of body mass in extinct terrestrial quadrupeds, which is important for a wide range of paleobiological studies (including growth rates, metabolism, and energetics) and meta-analyses of body size evolution.
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The 3D digitisation of palaeontological resources is of tremendous use to the field, providing the means to archive, analyse, and visualise specimens that would otherwise be too large to handle, too valuable to destructively sample, or simply in a different geographic location. Digitisation of a specimen to produce a 3D digital model often requires the use of expensive laser scanning equipment or proprietary digital reconstruction software, making the technique inaccessible to many workers. Presented here is a guide for producing high resolution 3D models from photographs, using freely available open-source software. To demonstrate the accuracy and flexibility of the approach, a number of examples are given, including a small trilobite (~0.04 m), a large mounted elephant skeleton (~3 m), and a very large fossil tree root system (~6 m), illustrating that the method is equally applicable to specimens or even outcrops of all sizes. The digital files of the models produced in this paper are included. The results demonstrate that production of digital models from specimens for research or archival purposes is available to anyone, and it is hoped that an increased use of digitisation techniques will facilitate research and encourage collaboration and dissemination of digital data.
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Body mass is a critical parameter used to constrain biomechanical and physiological traits of organisms. Volumetric methods are becoming more common as techniques for estimating the body masses of fossil vertebrates. However, they are often accused of excessive subjective input when estimating the thickness of missing soft tissue. Here, we demonstrate an alternative approach where a minimum convex hull is derived mathematically from the point cloud generated by laser-scanning mounted skeletons. This has the advantage of requiring minimal user intervention and is thus more objective and far quicker. We test this method on 14 relatively large-bodied mammalian skeletons and demonstrate that it consistently underestimates body mass by 21 per cent with minimal scatter around the regression line. We therefore suggest that it is a robust method of estimating body mass where a mounted skeletal reconstruction is available and demonstrate its usage to predict the body mass of one of the largest, relatively complete sauropod dinosaurs: Giraffatitan brancai (previously Brachiosaurus) as 23200 kg.
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Inertial properties of animal bodies and segments are critical input parameters for biomechanical analysis of standing and moving, and thus are important for paleobiological inquiries into the broader behaviors, ecology and evolution of extinct taxa such as dinosaurs. But how accurately can these be estimated? Computational modeling was used to estimate the inertial properties including mass, density, and center of mass (COM) for extant crocodiles (adult and juvenile Crocodylus johnstoni) and birds (Gallus gallus; junglefowl and broiler chickens), to identify the chief sources of variation and methodological errors, and their significance. High-resolution computed tomography scans were segmented into 3D objects and imported into inertial property estimation software that allowed for the examination of variable body segment densities (e.g., air spaces such as lungs, and deformable body outlines). Considerable biological variation of inertial properties was found within groups due to ontogenetic changes as well as evolutionary changes between chicken groups. COM positions shift in variable directions during ontogeny in different groups. Our method was repeatable and the resolution was sufficient for accurate estimations of mass and density in particular. However, we also found considerable potential methodological errors for COM related to (1) assumed body segment orientation, (2) what frames of reference are used to normalize COM for size-independent comparisons among animals, and (3) assumptions about tail shape. Methods and assumptions are suggested to minimize these errors in the future and thereby improve estimation of inertial properties for extant and extinct animals. In the best cases, 10%-15% errors in these estimates are unavoidable, but particularly for extinct taxa errors closer to 50% should be expected, and therefore, cautiously investigated. Nonetheless in the best cases these methods allow rigorous estimation of inertial properties.
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Body mass reconstructions of extinct vertebrates are most robust when complete to near-complete skeletons allow the reconstruction of either physical or digital models. Digital models are most efficient in terms of time and cost, and provide the facility to infinitely modify model properties non-destructively, such that sensitivity analyses can be conducted to quantify the effect of the many unknown parameters involved in reconstructions of extinct animals. In this study we use laser scanning (LiDAR) and computer modelling methods to create a range of 3D mass models of five specimens of non-avian dinosaur; two near-complete specimens of Tyrannosaurus rex, the most complete specimens of Acrocanthosaurus atokensis and Strutiomimum sedens, and a near-complete skeleton of a sub-adult Edmontosaurus annectens. LiDAR scanning allows a full mounted skeleton to be imaged resulting in a detailed 3D model in which each bone retains its spatial position and articulation. This provides a high resolution skeletal framework around which the body cavity and internal organs such as lungs and air sacs can be reconstructed. This has allowed calculation of body segment masses, centres of mass and moments or inertia for each animal. However, any soft tissue reconstruction of an extinct taxon inevitably represents a best estimate model with an unknown level of accuracy. We have therefore conducted an extensive sensitivity analysis in which the volumes of body segments and respiratory organs were varied in an attempt to constrain the likely maximum plausible range of mass parameters for each animal. Our results provide wide ranges in actual mass and inertial values, emphasizing the high level of uncertainty inevitable in such reconstructions. However, our sensitivity analysis consistently places the centre of mass well below and in front of hip joint in each animal, regardless of the chosen combination of body and respiratory structure volumes. These results emphasize that future biomechanical assessments of extinct taxa should be preceded by a detailed investigation of the plausible range of mass properties, in which sensitivity analyses are used to identify a suite of possible values to be tested as inputs in analytical models.
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