Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions

Abstract

The megatooth shark, Otodus megalodon, is widely accepted as the largest macrophagous shark that ever lived; and yet, despite over a century of research, its size is still debated. The great white shark, Carcharodon carcharias, is regarded as the best living ecological analog to the extinct megatooth shark and has been the basis for all body length estimates to date. The most widely accepted and applied method for estimating body size of O. megalodon was based upon a linear relationship between tooth crown height and total body length in C. carcharias. However, when applying this method to an associated dentition of O. megalodon (UF-VP-311000), the estimates for this single individual ranged from 11.4 to 41.1 m. These widely variable estimates showed a distinct pattern, in which anterior teeth resulted in lower estimates than posterior teeth. Consequently, previous paleoecological analyses based on body size estimates of O. megalodon may be subject to misinterpretation. Herein, we describe a novel method based on the summed crown width of associated fossil dentitions, which mitigates the variability associated with different tooth positions. The method assumes direct proportionality between the ratio of summed crown width to body length in ecologically and taxonomically related fossil and modern species. Total body lengths were estimated from 11 individuals, representing five lamniform species: Otodus megalodon, Otodus chubutensis, Carcharodon carcharias, Carcharodon hubbelli, and Carcharodon hastalis. The method was extrapolated for the largest known isolated upper tooth of O. megalodon, resulting in a maximum body length estimate of 20 m.

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Perez, Victor J., Leder, Ronny M., and Badaut, Teddy. 2021. Body length estimation of Neogene macrophagous lamniform sharks
(Carcharodon and Otodus) derived from associated fossil dentitions. Palaeontologia Electronica, 24(1):a09. https://doi.org/10.26879/
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Body length estimation of
Neogene macrophagous lamniform sharks
(Carcharodon and Otodus) derived from
associated fossil dentitions
Victor J. Perez, Ronny M. Leder, and Teddy Badaut
ABSTRACT
The megatooth shark, Otodus megalodon, is widely accepted as the largest mac-
rophagous shark that ever lived; and yet, despite over a century of research, its size is
still debated. The great white shark, Carcharodon carcharias, is regarded as the best
living ecological analog to the extinct megatooth shark and has been the basis for all
body length estimates to date. The most widely accepted and applied method for esti-
mating body size of O. megalodon was based upon a linear relationship between tooth
crown height and total body length in C. carcharias. However, when applying this
method to an associated dentition of O. megalodon (UF-VP-311000), the estimates for
this single individual ranged from 11.4 to 41.1 m. These widely variable estimates
showed a distinct pattern, in which anterior teeth resulted in lower estimates than pos-
terior teeth. Consequently, previous paleoecological analyses based on body size esti-
mates of O. megalodon may be subject to misinterpretation. Herein, we describe a
novel method based on the summed crown width of associated fossil dentitions, which
mitigates the variability associated with different tooth positions. The method assumes
direct proportionality between the ratio of summed crown width to body length in eco-
logically and taxonomically related fossil and modern species. Total body lengths were
estimated from 11 individuals, representing five lamniform species: Otodus megal-
odon, Otodus chubutensis, Carcharodon carcharias, Carcharodon hubbelli, and
Carcharodon hastalis. The method was extrapolated for the largest known isolated
upper tooth of O. megalodon, resulting in a maximum body length estimate of 20 m.
Victor J. Perez. Department of Vertebrate Paleontology, Florida Museum of Natural History, 1659 Museum
Rd., Gainesville, Florida 32611, USA and Department of Geological Sciences, University of Florida, 241
Williamson Hall, PO Box 112120, Gainesville, Florida 32611, USA and Department of Paleontology,
Calvert Marine Museum, Solomons, Maryland 20688, USA Victor.Perez@calvertcountymd.gov
Ronny M. Leder. Department of Vertebrate Paleontology, Florida Museum of Natural History, 1659
Museum Rd., Gainesville, Florida 32611, USA and Natural History Museum City of Leipzig, Lortzingstraße

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
2
3, 04105 Leipzig, Germany. ronnymaik.leder@leipzig.de
Teddy Badaut. Independent Researcher, Thoirette, France. kieffer_stirlling@hotmail.fr
Keywords: megalodon; body size; fossil; paleoecology; macropredator; apex predator
Submission: 12 November 2020. Acceptance: 1 March 2021.
INTRODUCTION
The order Lamniformes includes two of the
most iconic shark species: the extant great white,
Carcharodon carcharias, and the extinct mega-
tooth shark, Otodus megalodon (Cappetta, 1987,
2012). Carcharodon carcharias is the largest mac-
rophagous shark alive today, achieving maximum
body lengths of arguably 6 to 7 m (Gottfried et al.,
1996; Castro, 2012; McClain et al., 2015). Otodus
megalodon represents the largest macrophagous
shark that ever lived, with contentious adult esti-
mates ranging from 10 to more than 30 m (Dean,
1909; Randall, 1973; Bendix-Almgreen, 1983;
Gottfried et al., 1996; Pimiento et al., 2010;
Pimiento and Balk, 2015; Reolid and Molina, 2015;
Trif et al., 2016; Grant et al., 2017; Razak and Koc-
sis, 2018; Shimada, 2002a, 2019; Herraiz et al.,
2020). This longstanding interest in body size of
the world’s largest marine macropredators has
been shared by professional paleontologists and
the public alike. Hypothetical models of Otodus
megalodon are used as centerpiece exhibits in
numerous natural history museums (e.g., the
Calvert Marine Museum, Florida Museum, Smith-
sonian National Museum of Natural History, West-
ern Australian Museum). Likewise, popular science
fiction has featured these taxa, with vastly overesti-
mated body sizes (e.g., Jaws and The Meg). Con-
straining body size estimates is imperative if we
are to accurately represent these taxa and deci-
pher the evolutionary mechanisms that produced
these enormous macropredators.
The chondrichthyan fossil record is largely
restricted to teeth, due to the high preservation
potential of hydroxyapatite and poor preservation
potential of cartilage and soft tissue (Kent, 1994).
Consequently, interpretation of chondrichthyan
evolutionary history is largely restricted to what we
can infer from dental data and modern analogs. To
estimate the size of Otodus megalodon, a number
of researchers have attempted to relate tooth
height to total body length in the extant great white
shark as a proxy (Gottfried et al., 1996; Pimiento et
al., 2010; Pimiento and Balk, 2015; Reolid and
Molina, 2015; Trif et al., 2016; Grant et al., 2017;
Razak and Kocsis, 2018; Shimada, 2002a, 2019).
Gottfried et al. (1996) estimated body size based
on the relationship between total tooth (root and
crown) height (TH) of the second upper anterior
(A2; see Figure 1A for dentition terminology) and
total body length (TL), resulting in a conservative
maximum adult size of 15.9 m for O. megalodon.
Gottfried et al. (1996) speculated the TL of O. meg-
alodon throughout ontogeny by scaling up TL and
body mass in extant Carcharodon carcharias indi-
viduals from different ontogenetic stages. Pimiento
et al. (2010) used this to define three life stages for
O. megalodon: neonate (TL < 4 m), juvenile (TL = 4
to 10.5 m), and adult (TL > 10.5 m).
Shimada (2002a, 2019) suggested that
growth rates in the crown and root are not isomet-
ric, and instead developed a method based on
crown height (CH). Shimada (2002a) used a linear
regression to determine the relationship between
CH and TL for each tooth position in C. carcharias.
It was then proposed that these equations may be
an appropriate analog to estimate body size of O.
megalodon, given that C. carcharias represents the
largest extant macrophagous shark. All subse-
quent studies (Pimiento et al., 2010; Pimiento and
Balk, 2015; Reolid and Molina, 2015; Trif et al.,
2016; Grant et al., 2017; Razak and Kocsis, 2018;
Herraiz et al., 2020) mentioned have since used
the Shimada (2002a) equations to estimate the
size of O. megalodon. However, K-12 students
applied Shimada’s (2002a) equations to a 3D
printed model of an associated dentition (i.e., multi-
ple teeth from a single individual) of O. megalodon
(UF-VP-311000), resulting in a range of body
length estimates from 12 to 45 m for this single
individual (Grant et al., 2017). This prompted the
authors of this study to re-evaluate the Shimada
(2002a) method and to develop the novel method
described herein.
Since then, Shimada (2019) also re-evaluated
the original linear equations proposed in 2002 and
took a closer look at the relationship between CH
and TL of anterior tooth positions in Carcharodon
carcharias. In this study, Shimada determined that
a power function results in a greater correlation
between CH and TL than a linear regression. Fur-
ther, Shimada determined that upper anterior teeth

PALAEO-ELECTRONICA.ORG
3
FIGURE 1. Premise of summed crown width method. (A) Carcharodon carcharias dentition in lingual view, with appli-
cable terminology. The right half is an illustration of the typical dental formula for C. carcharias. The left half is from a
5.18 m female with one less posterior tooth in the lower tooth series (originally figured in Hubbell, 1996; figure 5).
Scale bar equals 5 cm. (B) The most complete known associated dentition of Otodus megalodon (CH-31-46P) in lin-
gual view. Scale bar equals 5 cm. (C) Body length of fossil taxa is calculated under the assumption that the ratio of
summed crown width to total body length (TL) is proportional in ecologically and taxonomically related species. Sil-
houette proportions for O. megalodon are based on Cooper et al. (2020). A/a = anterior, I = intermediate, and L/l = lat-
eral. Uppercase letters denote upper teeth and lowercase letters denote lower teeth.

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
4
resulted in more reliable estimates than lower
teeth, and that the second upper anterior (A2)
tooth position provides more reliable estimates
than the first upper anterior (A1) tooth position. Shi-
mada et al. (2020) analyzed dental homology in
macrophagous lamniforms based on the typical
“lamnoid tooth pattern.” In this dental pattern, ante-
rior teeth are always the tallest (Applegate, 1965;
Shimada, 2020). Shimada (2019) used the isolated
O. megalodon tooth with the largest CH in a
museum collection (NSM PV-19896; CH=120 mm)
to estimate a maximum body size, assuming it rep-
resents tooth position A1-A2, resulting in a TL of
14.2 to 15.3 m.
These results have clear implications that
applying the Shimada (2002a) method to a sample
of isolated teeth could be biased by estimates
derived from different tooth positions. Whether one
attempts to apply the Shimada (2002a) or Shimada
(2019) method to estimate body size, both require
identification, or at least approximation, of tooth
positions from isolated fossil teeth. Identifying tooth
positions requires knowledge of a taxon’s dental
formula, which defines the total number of teeth
and how they are arranged within a dentition. Two
forms of evidence have been used to infer the den-
tal formula of the megatooth lineage, each of which
has pros and cons. Extant macrophagous sharks
offer a source of indirect evidence, in which the
dental formula of the extinct megatooth lineage is
assumed to reflect that of the closest living analogs
(i.e., the lamnoid tooth pattern). The fossil record
offers the only direct evidence of the megatooth lin-
eage but consists primarily of isolated teeth (Cap-
petta, 2012). Rare disarticulated, associated
dentitions represent the most holistic direct evi-
dence available to reconstruct the dental formula of
the extinct megatooth lineage (Uyeno et al., 1989;
Purdy et al., 2001; Pimiento et al., 2010; Perez et
al., 2019). Consequently, all reconstructions of the
dental formula in the megatooth lineage represent
hypothetical models (Welton and Farish, 1993; Shi-
mada, 2005). The various dental models proposed
are fundamentally important for understanding
potential biases in body length estimates of the
megatooth lineage. Proposed dental models for the
megatooth lineage are intrinsically linked to their
taxonomic assignment.
Megatooth Shark Taxonomy
The taxonomy of Otodus megalodon has
changed frequently and even now a complete con-
sensus has not been reached. Otodus megalodon
was originally assigned to the genus Carcharodon,
under the assumption that it was related to
Carcharodon carcharias, and was placed in the
family Lamnidae (Agassiz, 1833-1844; Applegate
and Espinosa-Arrubarrena, 1996; Gottfried et al.,
1996; Purdy, 1996; Purdy et al., 2001). Other
researchers have proposed that O. megalodon
evolved as a separate lineage derived from Otodus
obliquus, placing it in the family Otodontidae
(Casier, 1960; Glickman, 1964; Zhelezko and
Kozlov, 1999; Ward and Bonavia, 2001; Nyberg et
al., 2006; Cappetta, 2012; Ehret et al., 2012; Shi-
mada et al., 2017; Perez et al., 2019). Three alter-
native generic names had been proposed:
Carcharocles (Jordan and Hannibal, 1923), Pro-
carcharodon (Casier, 1960), and Megaselachus
(Glickman, 1964). Consequently, many research-
ers began to use the genus Carcharocles, given
that it had precedence over Procarcharodon and
Megaselachus, to describe all serrated taxa within
the megatooth lineage (i.e., C. auriculatus, C.
angustidens, C. chubutensis, and C. megalodon).
The presence of serrations represents a con-
venient and easily distinguishable character to
delineate O. obliquus from its descendants; how-
ever, Cappetta (2012) argued that serrations were
not a sufficient character to warrant a separate
genus and instead used Otodus for the entire lin-
eage. As somewhat of a compromise, Cappetta
(2012) proposed the use of Carcharocles and
Megaselachus as subgenera to describe serrated
taxa within the megatooth lineage. Shimada et al.
(2017) also argued for the use of Otodus for the
entire megatooth lineage to achieve monophyly,
under the assumption that Parotodus and Megalol-
amna were sister taxa to Otodus within the family
Otodontidae. However, Shimada et al. (2017)
acknowledged that this shifts the issue of para-
phyly to the ancestor of O. obliquus, Cretalamna,
and that paraphyletic taxa are inevitable when
attempting to place Linnaean taxa onto a phyloge-
netic tree.
Kent (2018) noted that the debate between
the use of Carcharocles versus Otodus hinges on
whether the lineage evolved through cladogenesis
versus anagenesis and argued that the fossil
record of megatooth sharks may not be sufficiently
detailed to demonstrate anagenesis. Whether the
megatooth lineage evolved through a series of
rapid branching events (i.e., cladogenesis) or
through the slow accumulation of mutations over
time (i.e., anagenesis) is somewhat irrelevant to
this study. For now, we will adopt the popular use
of Otodus to describe the megatooth sharks as a
chronospecific lineage. Rather, what is relevant is

PALAEO-ELECTRONICA.ORG
5
that we agree that O. megalodon evolved from O.
obliquus and represents a separate lineage from
that of C. carcharias (Figure 2).
The Megatooth Dental Formula
Lamniform sharks typically exhibit hetero-
donty known as the “lamnoid tooth pattern,” which
consists of both monognathic and dignathic hetero-
donty (Shimada, 2002b; Shimada et al., 2020). In
macrophagous lamniforms, upper monognathic
heterodonty is generally characterized by two rows
of anterior teeth on either side of the jaw symphy-
sis, followed by one or more intermediate tooth
rows, and a series of lateral teeth. The anterior
teeth are vertically erect and generally represent
the tallest teeth in the dentition. The intermediate
teeth are significantly smaller, interrupting the gen-
eral pattern of the tallest teeth being mesial posi-
tions and smallest teeth being distal positions,
relative to the jaw symphysis. Shimada (2002b)
referred to the first three tooth positions (i.e., A1,
A2, and I1) as “index tooth rows” to identify dental
homologies. However, it is possible for a shark to
modify their dentition by either losing or gaining a
tooth row. Further, there is intraspecific variability in
the lamnoid tooth pattern (Hubbell, 1996).
Applegate and Espinosa-Arrubarrena (1996;
figure 1a) depicted C. carcharias with 46 teeth in its
functional series. In this model, a complete half of
the dentition has an upper tooth series with two
anterior, one intermediate, five lateral, and four
posterior teeth and a lower tooth series with three
anterior, five lateral, and three posterior teeth. In
Shimada (2002a; figure 1), Carcharodon carcha-
rias has a functional series consisting of 50 teeth.
In this model, a complete half of the dentition has
an upper tooth series with two anterior, one inter-
mediate, and 10 latero-posterior teeth and a lower
tooth series with two anterior, one intermediate,
and nine latero-posterior teeth. Based on denti-
tions observed by the authors of this study, we
assume that the typical dental formula for C.
carcharias is in between both models, with 48
teeth in the first functional series (Figure 1A).
Shimada (2005) defined a spectrum of pres-
ervation states for fossil shark teeth, ranging from
common isolated teeth to rare associated denti-
tions. Isolated tooth sets (i.e., composite or artifi-
cial dentitions) are comprised of teeth from
multiple individuals from the same taxon and rep-
resent a completely fabricated dental model. Asso-
ciated tooth sets (i.e., associated dentitions)
represent multiple teeth belonging to a single indi-
vidual, which can be found either in articulation or
disarticulated. Articulated dentitions provide a true
dental model. Disarticulated dentitions require
inferences to reassemble the true dental model but
provide context for making those inferences. Six
disarticulated, associated dentitions of O.
chubutensis and O. megalodon have been refer-
enced in peer-reviewed literature (Uyeno et al.,
1989; Purdy et al., 2001; Pimiento et al., 2010;
Grant et al., 2017; Perez et al., 2019). To date, no
one has reported a verified articulated, associated
dentition of O. chubutensis or O. megalodon.
Applegate and Espinosa-Arrubarrena (1996)
created artificial dentitions of Otodus/Carcharodon
using isolated tooth sets, in which they proposed a
dental formula for O. megalodon comprised of 58
teeth in the functional series. In this model, a com-
plete half of the dentition consisted of an upper
functional series with two anterior, one intermedi-
ate, seven lateral, and four posterior teeth and a
lower functional series with three anterior, eight lat-
eral, and four posterior teeth. Purdy et al. (2001)
figured partial reconstructions of two disarticulated,
associated dentitions of Otodus chubutensis
(USNM 411881 and USNM 299832) and one disar-
ticulated, associated dentition of Otodus megal-
odon (NCSM 13073) from the Lee Creek Mine in
Aurora, North Carolina. These reconstructions all
included a medially-oriented upper intermediate
tooth, based on an assumed evolutionary relation-
ship with Carcharodon carcharias.
Pimiento et al. (2010; figure S1) provided a
dental model for Otodus megalodon consisting of
46 teeth in its functional series, with a complete
half of the dentition comprised of an upper func-
tional series with three anterior and nine latero-
posterior teeth and a lower functional series with
three anterior and eight latero-posterior teeth. This
was the first dental model for Otodus megalodon
that lacked any intermediate tooth positions. It is
unclear if tooth position A3 in O. megalodon should
FIGURE 2. Phylogeny of macrophagous lamniforms
included in this study, showing the relationship between the
family Otodontidae (O. megalodon and O. chubutensis) and
the family Lamnidae (C. carcharias, C. hubbelli, C. hastalis,
I. paucus, and I. oxyrinchus).

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
6
be considered an intermediate tooth, but the pro-
portions are certainly not analogous to I1 in C.
carcharias (Figure 1). Pimiento et al. (2010) stated
that this dental model was adapted from Gottfried
et al. (1996), which presumably refers to the com-
posite, artificial dentition of O. megalodon on
exhibit at the Calvert Marine Museum (see
Gottfried et al., 1996; figure 1B). Gottfried et al.
(1996) stated that the figured O. megalodon denti-
tion was casted from the original Smithsonian com-
posite dentition “… prior to the discovery of
important natural tooth sets at Lee Creek Mine,
North Carolina and in Florida that help clarify the
arrangement of teeth in C. megalodon.”
The dental model for Otodus megalodon in
Pimiento et al. (2010; figure S1) originated, at least
in part, from dental reconstructions based on the
fossil associated dentitions that Gottfried et al.
(1996) had alluded to. Pimiento et al. (2010; tables
S1 and S2) referred to these specimens as “juve-
nile Carcharocles megalodon associated tooth set”
and “adult Carcharocles megalodon associated
tooth set” and reported crown height (CH) and
crown width (CW) measurements for each tooth
position. The juvenile individual was recovered by
L. Martin and G. Hubbell in 1995 from the Bone
Valley region in Florida (herein referred to as CH-
31-46P, Figure 1B), and the adult individual was
recovered by A. Felt in 1996 from the Lee Creek
Mine in North Carolina (herein referred to as UF-
VP-311000). Both disarticulated, associated denti-
tions were originally reconstructed by G. Hubbell.
Images of CH-31-46P can be found on
www.elasmo.com (Bourdon, 2005; Razak and Koc-
sis, 2018), and a 3D model of UF-VP-311000 is fig-
ured in Grant et al. (2017; figure 1). The Bone
Valley dentition (CH-31-46P) has been referenced
in exhibits at the Florida Museum, Smithsonian
National Museum of Natural History, and Western
Australian Museum.
Pimiento et al. (2010; figure 4) used the
CH:CW ratio in these associated dentitions to
approximate tooth positions of isolated O. megal-
odon teeth from the Gatun Formation. Some teeth
were assigned to an exact tooth position, while oth-
ers were given a range of potential tooth positions.
Pimiento et al. (2010) then used these tooth posi-
tions to estimate body size with the equations
reported by Shimada (2002a) and determined that
the Gatun Formation represented a paleo-nursery
for O. megalodon. Pimiento and Balk (2015)
repeated this process to analyze spatial and tem-
poral macroevolutionary body size trends in O.
megalodon. This method has since propagated
into numerous studies of O. megalodon (Reolid
and Molina, 2015; Trif et al., 2016; Grant et al.,
2017; Razak and Kocsis, 2018; Herraiz et al.,
2020).
Given that fossil associated dentitions were
influential in predicting the dental formula for Oto-
dus megalodon, it seems logical that we should
test the accuracy of body length estimates using
these associated dentitions as hypothetical mod-
els. Further, preliminary results reported in Grant et
al. (2017) indicated that the Shimada (2002a)
method results in highly variable body length esti-
mates. As such, this study analyzes variability in
body length estimates by applying the dental
model proposed by Pimiento et al. (2010) to fossil
associated dentitions. In addition, a novel method
for estimating TL is proposed based on this dental
model.
Body Length Estimation using Jaw Width
Methods for estimating body length based on
TH, CH, and CW all follow a similar rationalization
that teeth grow proportionately with total body
length. Reolid and Molina (2015; figure 4) com-
pared the linear relationship between different
crown measurements in the second upper anterior
tooth position (A2) and total body length (TL) in
Carcharodon carcharias, reporting a greater cor-
relation for CH than CW (r=0.92 for CH and r=0.53
for CW). However, after re-calculating the Pearson
coefficient of correlation (r) from the Reolid and
Molina (2015) dataset, the correlation should be
r=0.77 for CW (n=58) and r=0.93 for CH (n=85).
While this still indicates that CH is a better predic-
tor of body length than CW, it does not consider
other tooth positions or summed crown width
(SCW) of associated teeth as a proxy for body
length. In addition, there has been inconsistency in
the literature regarding tooth position nomencla-
ture. Hubbell (1996) referred to the first two ante-
rior teeth of C. carcharias as A2 and A3, due to a
hypothesis from Applegate and Espinosa-Arrubar-
rena (1996) that C. carcharias had lost an anterior
tooth row during its evolution. Consequently, Reo-
lid and Molina (2015) included data from Hubbell
(1996) that actually refers to tooth position A1 and
combined this with data from other studies for tooth
position A2.
Lowry et al. (2009) studied the relationship
between jaw circumference and total body length
in 14 shark species, as a means of estimating body
size from shark bite marks. This forensic method
allows researchers to estimate the body size of
individuals involved in shark attacks. Lowry et al.

PALAEO-ELECTRONICA.ORG
7
(2009) used a metric referred to as the interdental
distance (IDD), which is measured as the distance
between the crown apex of two neighboring teeth,
as a proxy for jaw circumference. A linear regres-
sion of IDD versus TL for C. carcharias resulted in
an R2=0.98 for the upper jaw and R2=0.97 for the
lower jaw. Siversson (2012) first emphasized the
potential of applying this method to estimate body
size in fossil taxa, specifically the extinct Creta-
ceous lamniform Cardabiodon ricki. Newbrey et al.
(2015) applied the jaw circumference method to a
partially articulated, associated dentition of C. ricki,
resulting in a body length estimate of 5.5 m. This
method has a strong foundational premise but
does not offer a way to account for missing teeth in
fossil dentitions and requires assumptions regard-
ing interdental spacing.
This study introduces a novel method for esti-
mating body size in fossil lamniform sharks that
builds on the concept that jaw circumference is
proportional to total body length. Such that, the
summed crown width (SCW) in the functional
series is constrained by jaw size. Based on a sim-
ple mathematical concept referred to as the rule of
three, this method assumes direct proportionality
between the ratio of SCW to TL in related modern
and fossil taxa (Figure 1C). Herein, we apply this
method to fossil associated dentitions from five
macrophagous lamniform species within the fami-
lies Otodontidae and Lamnidae: Otodus megal-
odon, Otodus chubutensis, Carcharodon
carcharias, Carcharodon hubbelli, and Carcharo-
don hastalis.
MATERIALS AND METHODS
Modern and Fossil Dentitions
Data was collected from the first functional
series in 11 fossil associated dentitions of lamni-
form sharks (Table 1) and 19 modern lamniform
dentitions (Table 2). These specimens are repos-
ited in the Florida Museum (UF-VP), Gordon Hub-
bell Collection (GHC), and the National Museum of
Natural History of the Smithsonian Institution
(USNM). Specimens in the GHC are gradually
being acquisitioned into the Florida Museum verte-
brate paleontology collection and will remain
accessible for research throughout the process.
Provenance information for these specimens was
derived from each museum’s collections database
and/or personal communication with the museum’s
respective collections manager (i.e., R. Hulbert, G.
Hubbell, and D. Bohaska).
Four associated dentitions and a single iso-
lated tooth of Otodus megalodon were included in
this study. UF-VP-311000 consists of 37 teeth (22
from the first functional series) collected by A. Felt
in 1996 within the Nutrien Corp phosphate mine
(commonly known as the Lee Creek Mine) in
Aurora, North Carolina (Figure 3A). 3-D files of UF-
TAB LE 1. Specimen data for fossil material included in this study.
Specimen ID Location Lithostratigraphy Geologic Age Nature of Specimen
Otodus megalodon
UF-VP-311000 North Carolina, USA Yorktown Fm Pliocene 37 associated teeth
GHC 1 Atacama Desert, Chile Bahía Inglesa Fm Miocene 92 associated teeth
CH-31-46P Florida, USA Bone Valley Fm Miocene 95 associated teeth
UF-VP-460000 Atacama Desert, Chile Bahía Inglesa Fm Miocene 43 associated teeth
GHC 6 South Carolina, USA Hawthorn Group Miocene 1 isolated tooth
Otodus chubutensis
USNM 411881 North Carolina, USA Pungo River Fm Miocene 106 associated teeth
USNM 299832 North Carolina, USA Pungo River Fm Miocene 32 associated teeth
GHC 3 Ica, Peru Caballos Fm Miocene 65 associated teeth
UF-VP-312864 Ica, Peru Caballos Fm Miocene 53 associated teeth
Carcharodon carcharias
GHC 4 Sacaco, Peru Pisco Fm Mio-Pliocene 65 associated teeth
Carcharodon hubbelli
UF-VP-226255 Sacaco, Peru Pisco Fm Miocene Articulated skeleton: 222
teeth, 45 centra
Carcharodon hastalis
GHC 5 Sacaco, Peru Pisco Fm Mio-Pliocene 165 associated teeth

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
8
VP-311000 are freely available on Morpho-
Source.org. GHC 1 consists of 92 teeth (36 from
the first functional series) found by M. Marinelar-
ena in 2003 within the phosphate mining region of
the Atacama Desert in northern Chile (Figure 3B).
CH-31-46P consists of 95 teeth (44 teeth from the
first functional series) found by L. Martin and G.
Hubbell in 1995 within the Four Corners phosphate
mine in Polk County, Florida (Figure 1B and 3C).
The physical specimen resides in the GHC;
although, reproductions can be purchased from
Bone Clones under the code CH-31-46P (we use
this as a temporary identifier until the specimen is
assigned a globally unique identifier). UF-VP-
460000 consists of 43 teeth (30 from the first func-
tional series) found by J. Arias in 2003 within the
phosphate mining region of the Atacama Desert in
northern Chile (Figure 3D). GHC 6 represents the
largest isolated tooth of O. megalodon known to
the authors of this study (TH=165 mm, CH=122
mm, CW=133 mm). This specimen was found by V.
Bertucci while diving in the Morgan River in South
Carolina.
Four associated dentitions of Otodus
chubutensis were included in this study. USNM
411881 consists of 106 teeth (38 from the first func-
tional series) found by P. Harmatuk in 1986 within
the Nutrien Corp phosphate mine in Aurora, North
Carolina (Figure 4A). USNM 299832 consists of 32
teeth (20 from the first functional series) found by
P. Harmatuk in 1981 within the Nutrien Corp phos-
phate mine in Aurora, North Carolina (Figure 4B).
GHC 3 consists of 65 teeth (31 from the first func-
tional series) found by G. Hubbell in 1993 on the
western bank of the Ica River in Peru (Figure 4C).
UF-VP-312864 consists of 53 teeth (35 from the
first functional series) collected in 2002 from the
Ica River in Peru (Figure 4D).
Three associated dentitions of Carcharodon
spp. were included in this study, all from Sacaco,
Peru. GHC 4 is a C. carcharias dentition consisting
of 65 associated teeth (32 from the first functional
series) collected by C. Martin in 1988 (Figure 5A).
TABLE 2. Specimen data for 19 modern dentitions. SCW = summed crown width. TL = total body length. Measure-
ments are separated for the different regions preserved: upper left (UL), upper right (UR), lower left (LL), and lower
right (LR).
Specimen ID Location Sex
SCW (mm)
TL (cm)UL UR LL LR
Carcharodon carcharias
SOP020105018.011 Unknown M 152.99 - 98.39 - 237
F7687 Albany, Australia F 319.99 - 195.3 - 518
C41185 Ponce de Leon Inlet, FL F 191.21 195.1 131.95 129.11 281
R92185 Pointe Vicente, CA F 370.35 355.8 224.9 234.85 536
L11685 Anacapa Island, CA F 361.34 363.78 231.5 231.46 563
SP1394 St. Petersburg, FL M 337.47 344.3 223.96 226.9 474
F102281 Albany, Australia F 152.48 170.82 107.27 109.77 244
Car206 Los Angeles, CA M 84.66 79.94 55.99 55.27 124
RC112885 Los Angeles, CA F 115.04 113.89 82.23 79.68 170
H5384 Ledge Point, Australia F 323.76 320.52 193.48 197.19 594
H10886 Key Largo, FL M 274.32 277.66 186.02 183.56 503
Hubbell (1996, fig. 2) Unknown M - 291.72 - 190.45 440
Hubbell (1996, fig. 4) Unknown ? - 218.35 - 136.67 366
Hubbell (1996, fig. 5) Unknown F - 316.509 - 191.89 518
Hubbell (1996, fig. 6) Unknown M - 298.15 - 182.83 488
H8993 Bunbury, Australia M - 311.73 - 189.36 518
GHC 7 Unknown M - 314.78 - 195.92 520
Isurus oxyrinchus
GHC 8 San Nicol’s Island, CA F 187.24 182.11 155.15 157.7 320
Isurus paucus
GHC 9 Pompano Beach, FL F 238.48 249.82 215.9 207.32 488

PALAEO-ELECTRONICA.ORG
9
GHC 5 is a C. hastalis dentition consisting of 165
teeth (40 from the first functional series) collected
by C. Martin in 1988 (Figure 5B). UF-VP-226255 is
a partially articulated skeleton of C. hubbelli con-
sisting of 222 teeth, 45 centra, and portions of the
cartilaginous mandibular arch and neurocranium
(see Ehret et al., 2009, 2012).
To date, no completely articulated dentitions
of O. megalodon nor O. chubutensis have been
reported. Consequently, reconstructions of the fos-
sil dentitions represent hypothetical models that
can only be verified by the discovery of fully articu-
lated dentitions of each species being analyzed. As
such, the dental patterns utilized reflect a major
assumption that is fundamental to the body length
method described in this study.
Among the 19 modern lamniform dentitions,
measurements were recorded from 17 Carcharo-
don carcharias individuals, one Isurus oxyrinchus
individual, and one Isurus paucus individual. All
modern specimens originated from the GHC col-
lection. Specimens that were physically available
were measured using calipers, whereas speci-
mens that were figured in Hubbell (1996) were
measured digitally using ImageJ. See Table 2 for
additional specimen information.
Dental Measurements
Crown width (CW) and crown height (CH)
were measured for every tooth position in the 19
modern dentitions (Appendices 1 and 2) and 11
fossil dentitions (Appendices 3 and 4). CW is
defined as a line segment between the crown-root
contact on the mesial and distal cutting edges. CH
is defined as a perpendicular line segment from the
crown apex to the CW line segment. For nine of the
19 modern analogs, authors VJP and RML inde-
pendently measured CH and CW. These measure-
FIGURE 3. Associated dentitions of Otodus megalodon in lingual view. (A) UF-VP-311000; (B) GHC 1; (C) CH-31-
46P; and (D) UF-VP-460000. Scale bars equal 5 cm.

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
10
ments were used to address how much variation in
the final body length estimate could be attributed to
human measurement error.
Dentitions were segmented into four regions
(upper left, upper right, lower left, and lower right).
Summed crown width was measured for each
region of the dentitions. The summed crown width
of all teeth present in the dentition is referred to as
SCWms. To account for missing teeth in the fossil
dentitions, correction factors (CF) were determined
by calculating the percent of the total summed
width attributable to each tooth position in the mod-
ern and fossil dentitions (Figure 6 and Appendix 5).
The mean percentage for each tooth position of
modern Carcharodon carcharias was applied as a
correction factor to estimate the width of missing
teeth in the fossil dentitions of Carcharodon spp.
Missing teeth in the Otodus spp. dentitions were
corrected using percentages from the most com-
plete, comparable fossil Otodus dentition (Appen-
dix 5). Corrected summed crown width (SCWc) is
calculated to account for missing teeth by dividing
the measured summed crown width (SCWms) by
one minus the sum of all correction factors (Eq. 1).
Summed crown width, measured and corrected,
are provided in Table 3 for all fossil dentitions.
Body Length Estimation
Body length estimates were calculated under
a basic assumption that the ratios of summed
FIGURE 4. Associated dentitions of Otodus chubutensis in lingual view. (A) USNM 411881 (adapted from Perez et al.,
2019; fig. 5); (B) USNM 299832; (C) GHC 3; and (D) UF-VP-312864. Scale bars equal 5 cm.
Eq. 1

PALAEO-ELECTRONICA.ORG
11
crown width (SCW) to body length (TL) are propor-
tional in taxonomically and ecologically related
species (Eq 2). The rule of three method assumes
direct proportionality between the ratio of summed
crown width (a = SCWm) to body length (b = TLm)
in modern taxa (e.g., C. carcharias, I. oxyrinchus,
and I. paucus) and the ratio of summed crown
width (c = SCWf) to body length (x = TLf) in fossil
taxa (e.g., O. megalodon, O. chubutensis, C.
carcharias, C. hubbelli, and C. hastalis). Such that,
FIGURE 5. Associated dentitions of Carcharodon spp. in lingual view. (A) Carcharodon carcharias, GHC 4. (B)
Carcharodon hastalis, GHC 5. Scale bars equal 5 cm. See Ehret et al. (2009) for images of the Carcharodon hubbelli
dentition, UF-VP-226255.
FIGURE 6. Portion of summed crown width (SCW) for each tooth position. (A-B) Proportions from 10 modern
Carcharodon carcharias dentitions. (C-D) Proportions from all eight fossil Otodus associated dentitions, after apply-
ing correction factors. (A, C) upper and (B, D) lower. Correction factors were derived from these proportions (see
Appendix 5).

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
12
there are four variables, of which three can be
measured (a, b, and c) and the fourth solved for
(x):
Body length estimates were calculated using
three extant lamniform species as analogs: C.
carcharias (n=17), Isurus oxyrinchus (n=1), and
Isurus paucus (n=1). Body length estimates
derived from different modern analogs highlights
TAB LE 3 . Body length estimates from 11 fossil dentitions of Otodus and Carcharodon. Summed crown width measured
(SCWms) and corrected (SCWc), and total body length (TL). * denotes the best estimate. UL = upper left, UR = upper
right, LL = lower left, and LR = lower right.
Catalog # Position
SCWms
(mm)
SCWc
(mm)
TL Range
(m)
TL Mean
(m)
Otodus megalodon
GHC 6 L1-L2 133 1266.7 – 1303.9 17.4 – 24.2 *20.3
UF-VP-311000 UL 1055.5 1093.7 15.1 – 20.3 *17.3
LL 852.4 852.4 17.6 – 26.2 20.8
GHC 1 UL 951.5 1095.0 15.1 – 20.3 *17.3
UR 947.3 1122.4 15.5 – 20.8 17.7
LL 689.0 811.5 16.8 – 24.9 19.8
LR 550.4 781.8 16.2 – 24.0 19.1
CH-31-46P UL 783.5 783.5 10.8 – 14.5 *12.4
UR 739.5 790.9 10.9 – 14.7 12.5
LL 612.2 612.2 12.7 – 18.8 15.0
LR 579.2 611.6 12.6 – 18.8 14.9
UF-VP-460000 UL 519.6 681.9 9.4 – 12.6 10.8
UR 533.5 685.7 9.4 – 12.7 *10.9
LL 400.7 540.8 11.2 – 16.6 13.2
LR 404.8 546.3 11.3 – 16.8 13.3
Otodus chubutensis
USNM 299832 UL 215.4 679.5 9.4 – 12.6 10.7
UR 576.3 696.9 9.6 – 12.9 *11.0
LR 400.4 530.3 11.0 – 16.3 13.0
GHC 3 UL 60.1 707.1 9.7 – 13.1 11.2
UR 668.6 690.7 9.5 – 12.8 *10.9
LL 379.2 497.0 10.3 – 15.3 12.1
LR 542.7 542.7 11.2 – 16.7 13.3
USNM 411881 UL 491.5 569.5 7.8 – 10.6 *9.0
UR 482.7 546.7 7.5 – 10.1 8.6
LL 389.3 453.2 9.4 – 13.9 11.1
LR 300.4 429.1 8.9 – 13.2 10.5
Eq. 2

PALAEO-ELECTRONICA.ORG
13
interspecific and intraspecific variation in the rela-
tionship between SCW and TL. The rule of three
method was applied for each region of the fossil
dentitions preserved (upper left, upper right, lower
left, and/or lower right) with all 19 modern analogs.
Among the 19 modern analogs, eight only had half
of the dentition preserved (left or right). Thus, for a
single fossil dentition with all four quadrants pre-
served, there were a total of 120 different body
length estimates. The range and mean body length
estimates from each region of the jaw were calcu-
lated (Eq. 3). This equation is similar to a linear
regression, where the calculated mean approxi-
mates the linear trendline and the range captures
the extent of variance around the mean. The bene-
fit of calculating TL with this equation is the ability
to quickly compare estimates derived from specific,
individual modern analogs and better explain the
source of variance around the mean.
Extrapolation for Isolated Teeth
The correction factors that were calculated
using the modern dentitions of Carcharodon carch-
arias and the most complete fossil associated den-
titions of Otodus spp. were used to estimate body
size from isolated teeth. To extrapolate the SCW
method in this manner, one must first determine
which associated dentition to use as an analog to
approximate the appropriate tooth position. For
example, if you wish to estimate the size from an
isolated O. megalodon tooth, then you could use
either the adult individual (UF-VP-311000) or the
juvenile individual (CH-31-46P) as your analog to
do so. If you are uncertain which is the best analog,
then body length should be calculated using both
models and an average estimate should be
reported. If a tooth cannot be identified to a specific
tooth position, then a range of potential positions
and corresponding body lengths should be
reported.
This extrapolated version of the SCW method
offers the opportunity to re-assess body size esti-
UF-VP-312864 UL 357.9 376.3 5.2 – 7.0 *5.9
UR 269.1 379.5 5.2 – 7.0 6.0
LL 299.0 336.0 6.9 – 10.3 8.2
LR 174.3 305.3 6.3 – 9.4 7.5
Carcharodon hastalis
GHC 5 UL 301.2 336.5 4.6 – 6.2 5.3
UR 322.9 331.5 4.6 – 6.1 *5.2
LL 232.1 253.9 5.2 – 7.8 6.2
LR 219.2 223.0 4.5 – 6.9 5.4
Carcharodon hubbelli
UF-VP-226255 UL 291.4 299.2 4.1 – 5.5 4.7
UR 313.0 313.0 4.3 – 5.8 *4.9
LL 225.4 229.3 4.7 – 7.0 5.6
LR 189.2 220.3 4.5 – 6.8 5.4
Carcharodon carcharias
GHC 4 UL 191.6 256.1 3.5 – 4.8 4.0
UR 249.7 256.4 3.5 – 4.8 *4.0
LL 88.4 187.3 3.9 – 5.8 4.6
LR 178.5 195.3 4.0 – 6.0 4.8
Catalog # Position
SCWms
(mm)
SCWc
(mm)
TL Range
(m)
TL Mean
(m)
TAB LE 3 (continued).
Eq. 3

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
14
mates in previous paleoecological studies (i.e.,
Pimiento et al., 2010; Pimiento and Balk, 2015;
Herraiz et al., 2020) and compare them with esti-
mates derived from the Shimada (2002a, 2019)
isolated CH method. Body length estimates were
re-calculated using a subset of the Pimiento and
Balk (2015) sample. The SCW method was applied
by using proportions from CH-31-46P and UF-VP-
311000 separately. The average of these two esti-
mates was compared to those reported by
Pimiento and Balk (2015) to determine if there was
a predictable variation in body length estimates
based on the tooth position assigned.
The SCW method was also extrapolated to
estimate the maximum body size of Otodus megal-
odon, using the isolated tooth with the widest
known crown width (GHC 6; CW=133 mm). The
tooth position was assigned based on a compari-
son of the CH:CW ratios in the largest associated
dentition of O. megalodon, UF-VP-311000. The
corrected SCW was calculated based on the CW
proportions in UF-VP-311000.
RESULTS
Segmenting the dentitions into four regions
(upper left, upper right, lower left, and lower right)
allowed for the inclusion of partial associated denti-
tions, comparison of estimates derived from the
lower versus upper dentitions, and comparison of
estimates derived from the left versus right sides of
the dentitions. However, this also required determi-
nation as to which of the four regions provided the
most reliable body length estimate. In all taxa, bilat-
eral symmetry is generally observed; however, this
symmetry is often imperfect. Body length estimates
derived from the left and right sides of a single indi-
vidual varied from 0 to 0.4 m (Table 3). In terms of
selecting left versus right, the more complete side
of the fossil dentitions is considered the more reli-
able estimate.
For all individuals, the mean body length esti-
mates derived from the lower dentition were
greater than estimates derived from the upper den-
tition (Table 3 and Figure 7). For the upper denti-
tion, estimates using Isurus as the modern analog
were greater than estimates derived from
Carcharodon. For the lower dentition, estimates
using Isurus as the modern analog were within the
range of estimates derived from Carcharodon.
These differences between the upper and lower
dentitions and different modern analogs can be
explained by varying tooth morphologies attributed
to different functional roles and feeding ecologies
(see Discussion below). Thus, the mean TL from
the most complete upper half of the dentition, with
C. carcharias as the modern analog, is considered
the most reliable estimate (Table 3).
For the four individuals of O. megalodon,
mean body lengths estimates were 10.9, 12.4,
17.3, and 17.3 m, respectively. Using the same
modern comparative dataset, the body length esti-
mates for the four individuals of O. chubutensis
were 5.9, 9.0, 10.9, and 11.0 m, respectively. Only
a single individual of C. carcharias, C. hubbelli, and
C. hastalis were used in this study, which resulted
in body length estimates of 4.0, 4.9, and 5.1 m,
respectively.
The single individual of Carcharodon hubbelli,
UF-VP-226255, was the only fossil specimen found
as an articulated skeleton, comprised of 222 teeth
and 45 vertebral centra. Ehret et al. (2009) applied
body length equations based on regressions of
vertebral diameter and vertebral radius, proposed
by Cailliet et al. (1985), Gottfried et al. (1996), Win-
tner and Cliff (1999), and Natanson (2001). These
body length estimates based on vertebral mea-
surements ranged from 4.7 to 5.2 m, with a mean
estimate of 4.9 m. Ehret et al. (2009) also applied
the Shimada (2002a) method, resulting in a range
of estimates from 3.0 to 7.0 m, with a mean esti-
mate of 5.1 m. The SCW method resulted in a
range of estimates from 4.1 to 5.8 m, with a mean
estimate of 4.9 m.
The Shimada (2002a, 2019) methods were
applied to the 11 fossil dentitions for comparison
(Figure 7 and Table 4). Body length estimates
based on the Shimada (2002a) method resulted in
a wider range of estimates than the SCW method
described herein. For Otodus individuals, body
length estimates based on the Shimada (2019)
method were lower than the SCW method applied
herein. For Carcharodon individuals, body length
estimates based on the Shimada (2019) method
were within 0.5 m of estimates based on SCW.
Extrapolating the SCW method for the largest
known isolated tooth of O. megalodon (GHC 6)
resulted in a corrected summed crown width rang-
ing from 1266.7 to 1303.9 mm. Based on a SCW of
1266.7 mm, the SCW method results in a TL of
17.4 to 23.5 m, with a mean estimate of 20.0 m.
Based on a SCW of 1303.9 mm, the SCW method
results in a TL of 18.0 to 24.2 m, with a mean esti-
mate of 20.6 m.

PALAEO-ELECTRONICA.ORG
15
FIGURE 7. Comparison of body length estimates based on SCW direct proportions and Shimada (2002a) CH linear
regression. (A–B) Otodus megalodon; (C–D) Otodus chubutensis; and (E–F) Carcharodon spp. (A, C, E) SCW direct
proportions. (B, D, F) Shimada (2002a) CH linear regression. U = upper and L = lower.

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
16
TAB LE 4. Comparison of different methods for estimating body length: Shimada (2002a), Shimada (2019), and this
study. All estimates are in meters. * denotes the best estimate. UL = upper left, UR = upper right, LL = lower left, and
LR = lower right.
Catalog #
Tooth
Position
Shimada
(2002a)
Shimada
(2019)
SCW
(Range)
SCW
(Mean)
SCW
(Linear Fn)
SCW
(Power Fn)
Otodus megalodon
GHC 6 L1-L2 16.4 – 17.4 - 17.4 – 24.2 *20.3 *20.1 21.6
UF-VP-311000 UL 11.4 – 31.6 12.0 15.1 – 20.3 *17.3 *17.3 18.5
LL 11.6 – 41.1 10.3 17.6 – 26.2 20.8 21.6 24.8
GHC 1 UL 12.5 – 38.1 12.3 15.1 – 20.3 *17.3 *17.4 18.5
UR 13.1 – 30.0 12.8 15.5 – 20.8 17.7 17.8 19.0
LL 13.1 – 65.1 10.7 16.8 – 24.9 19.8 20.6 23.5
LR 12.3 – 29.1 10.5 16.2 – 24.0 19.1 19.8 22.5
CH-31-46P UL 9.3 – 19.8 9.3 10.8 – 14.5 *12.4 *12.4 13.0
UR 9.1 – 20.2 9.3 10.9 – 14.7 12.5 12.5 13.1
LL 9.8 – 31.8 8.7 12.7 – 18.8 15.5 15.5 17.2
LR 10.0 – 32.6 8.7 12.6 – 18.8 15.5 15.5 17.1
UF-VP-460000 UL 9.3 – 19.4 9.7 9.4 – 12.6 10.8 10.8 11.2
UR 9.2 – 21.8 9.3 9.4 – 12.7 *10.9 *10.9 11 .3
LL 9.3 – 16.7 8.3 11.2 – 16.6 13.7 13.7 14.9
LR 9.8 – 16.6 8.6 11.3 – 16.8 13.8 13.8 15.1
Otodus chubutensis
USNM 299832 UL 7.7 – 10.0 - 9.4 – 12.6 10.7 10.8 11.2
UR 7.5 – 19.4 - 9.6 – 12.9 *11.0 *11.0 11 .5
LR 8.4 – 15.7 7.6 11.0 – 16.3 13.0 13.4 14.6
GHC 3 UL - - 9.7 – 13.1 11.2 11.2 11.7
UR 7.3 – 16.5 7.5 9.5 – 12.8 *10.9 *10.9 11 .3
LL 8.1 – 23.7 - 10.3 – 15.3 12.1 12.5 13.6
LR 7.9 – 29.8 7.3 11.2 – 16.7 13.3 13.7 15.0
USNM 411881 UL 5.5 – 13.9 5.9 7.8 – 10.6 *9.0 *9.0 9.3
UR 5.3 – 14.9 6.0 7.5 – 10.1 8.6 8.6 8.9
LL 6.3 – 31.8 6.1 9.4 – 13.9 11.1 11.4 12.3
LR 6.1 – 26.5 5.9 8.9 – 13.2 10.5 10.8 11.6
UF-VP-312864 UL 4.1 – 14.2 4.3 5.2 – 7.0 *5.9 *5.9 6.0
UR 4.4 – 10.8 4.5 5.2 – 7.0 6.0 6.0 6.0
LL 5.1 – 31.3 5.2 6.9 – 10.3 8.2 8.4 8.8
LR 5.6 – 24.1 - 6.3 – 9.4 7.5 7.6 7.9
Carcharodon hastalis
GHC 5 UL 4.5 – 5.6 5.6 4.6 – 6.2 5.3 5.3 5.3
UR 4.0 – 5.5 5.5 4.6 – 6.1 *5.2 *5.2 5.2
LL 4.6 – 8.5 5.9 5.2 – 7.8 6.2 6.3 6.4
LR 3.4 – 6.1 5.5 4.5 – 6.9 5.4 5.5 5.6

PALAEO-ELECTRONICA.ORG
17
DISCUSSION
Accounting for Error
There are a few different potential sources of
error that could impact body length estimates using
the SCW direct proportionality method. These
sources can be broadly grouped into three catego-
ries: natural variation, human observer error, and
mathematical assumptions. Natural variation in
tooth proportions occurs within individuals, within
species, and between species, which could intro-
duce error to our body length estimates. Human
error could be introduced while measuring teeth or
through assumptions related to the dental count
and pattern of fossil dentitions. Assumptions
regarding the optimal mathematical equation intro-
duce yet another avenue for error. Accounting for
each source of error offers constraints on the
potential accuracy of body length estimates pro-
posed in this study and in previous studies.
Natural variation. Variation within individuals was
accounted for by comparing estimates between the
four quadrants in the dentition. Given that all indi-
viduals exhibit bilateral symmetry, there is minimal
variation between the left and right sides of the
dentition (i.e., < 0.5 m difference in TL estimates).
This was accounted for by simply selecting the side
of the fossil dentition that was most completely pre-
served as the superior estimate.
Greater variability was observed in estimates
derived from the upper versus the lower dentitions,
in which the lower dentition always resulted in
larger TL estimates than the upper dentition (Fig-
ure 7). This consistent difference in body length
estimates derived from upper and lower dentitions
can be explained by two factors: function and phy-
logeny. There is a difference in shape and corre-
sponding functionality between the lower and
upper dentition (Kent, 1994; Cappetta, 2012).
Lower teeth tend to be narrower and have a more
robust root relative to upper teeth, which aids in
penetrating and grasping prey. After the lower teeth
have anchored the prey, the upper teeth then tear
and cut the flesh. While both upper and lower teeth
are predominantly designed for cutting, there is
greater grasping functionality in lower teeth than in
upper teeth. Further, this grasping functionality of
the lower teeth is more apparent in representatives
of the genus Carcharodon than those in the genus
Otodus. Carcharodon spp. tend to have more sym-
metrical, vertically erect lower teeth than Otodus
spp.
Within the extant comparative dataset of C.
carcharias, SCW versus TL was plotted for the
upper and lower dentitions separately (Figure 8).
Both showed a strong correlation; however, the
coefficient of determination between upper SCW
and TL was stronger than that of the lower SCW
and TL (upper: R2=0.9326 and lower: R2=0.8977).
Thus, we concluded that the most reliable body
length estimates are from the most complete upper
half of the dentition. The determination that the
upper dentition is more reliable than the lower den-
tition is in agreement with the TH method
employed by Gottfried et al. (1996) and the CH
method proposed by Shimada (2019). It seems
plausible that the offset in TL estimates from the
upper and lower jaws may be predictable and,
thus, a correction factor could be calculated.
Although, determining if this is the case is a task for
a future research endeavor and beyond the
intended scope of this manuscript.
In addition to segmenting the jaw, three mod-
ern analogs within the family Lamnidae were con-
Carcharodon hubbelli
UF-VP-226255 UL 4.4 – 7.1 4.4 4.1 – 5.5 4.7 4.7 4.7
UR 3.3 – 6.1 4.4 4.3 – 5.8 *4.9 *4.9 4.9
LL 4.3 – 7.0 4.3 4.7 – 7.0 5.6 5.7 5.8
LR 4.3 – 5.8 4.3 4.5 – 6.8 5.4 5.5 5.5
Carcharodon carcharias
GHC 4 UL 3.0 – 4.8 4.1 3.5 – 4.8 4.0 4.0 4.0
UR 3.1 – 5.0 4.3 3.5 – 4.8 *4.0 *4.0 4.0
LL 4.0 – 4.6 4.4 3.9 – 5.8 4.6 4.6 4.6
LR 3.9 – 6.8 4.4 4.0 – 6.0 4.8 4.8 4.8
Catalog #
Tooth
Position
Shimada
(2002a)
Shimada
(2019)
SCW
(Range)
SCW
(Mean)
SCW
(Linear Fn)
SCW
(Power Fn)
TAB LE 4 (continued).

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
18
sidered: C. carcharias, Isurus oxyrinchus, and
Isurus paucus. Body length estimates derived from
the upper jaw of Isurus spp. resulted in larger body
length estimates than those derived from C. carch-
arias. For the lower dentition, estimates using
Isurus spp. as the modern analog were within the
range of estimates derived from C. carcharias.
While all three are macrophagous lamniform
sharks, they express very different dentition types
that correspond to different feeding ecologies.
Isurus spp. have narrower, non-serrated teeth that
serve to feed on fast swimming fishes, as opposed
to the more broadly triangular, serrated teeth of C.
carcharias that are better adapted to feeding on
fleshier marine mammals (Kent, 1994; Cappetta,
2012). Similar to the functional argument that
explains the differences between upper and lower
estimates, the narrower teeth of Isurus spp. also
result in relatively larger body length estimates. All
the fossil taxa analyzed in this study have more
broadly triangular teeth that are functionally more
similar to C. carcharias than Isurus spp.
These differences in body length estimates
between different parts of the jaw and different
modern analogs highlight the importance of select-
ing an ecologically similar modern analog to esti-
mate body size. This is particularly important when
attempting to estimate the size of taxa that are
even more distantly related (e.g., Otodus obliquus).
Cooper et al. (2020) stated that “Lamna nasus is
considered the best dental analogue for both Cre-
talamna and Megalolamna, mako sharks (Isurus
spp.) have similar dental morphology to Otodus,
and C. carcharias has similar dentition to Otodus
(Carcharocles) and Otodus (Megaselachus).” How-
ever, we feel that the typical tri-cusped morphology
of teeth in O. obliquus is more akin to the teeth of
the extant Lamna nasus. Future research that aims
to expand this method to other taxa should take
this into consideration when selecting their modern
analogs.
Aside from heterodonty, ontogeny is often ref-
erenced as the greatest source of natural intraspe-
cific variation in lamniform dentitions (Hubbell,
1996; Tomita et al., 2017). In C. carcharias, teeth
tend to be narrower in juveniles and become pro-
gressively broader throughout ontogeny (Hubbell,
1996; Tomita et al., 2017). Interestingly, Tomita et
al. (2017) noted that the intermediate tooth position
is proportionately similar to adjacent teeth in early-
FIGURE 8. Correlation between summed crown width and total body length in 17 modern Carcharodon carcharias
individuals, comparing the upper versus lower dentition. (A) linear function (upper dentition: R2 = 0.93); (B) power
function (upper dentition: R2 = 0.97); (C) linear function (lower dentition: R2 = 0.90); and (D) power function (lower
dentition: R2 = 0.95).

PALAEO-ELECTRONICA.ORG
19
term embryos and that the lamnoid tooth pattern is
achieved in mid- to full-term embryos. Conse-
quently, the CH and CW proportions vary through-
out ontogeny. This potential ontogenetic variation
is difficult to account for in the extinct megatooth
lineage, particularly with the small sample of asso-
ciated dentitions available. Among the four associ-
ated dentitions of Otodus megalodon, they can be
grouped into two size classes: juvenile (CH-31-46P
and UF-VP46000) and adult (UF-VP-311000 and
GHC 1). Consequently, correction factors for O.
megalodon were separated into two categories
(juvenile and adult) based on the most complete
associated dentitions available.
While lamniform sharks generally conform to
the lamnoid tooth pattern, there is undoubtedly
intra- and inter-specific variation in the dental count
and pattern. The general dental formula used in
this study for Carcharodon carcharias had 48 teeth
in its functional tooth series. However, the extant
individuals measured in this study had a functional
series ranging from 46 to 50 teeth (see Appendices
1 and 2). TL estimates for the largest associated
dentition of O. megalodon, UF-VP-311000, using
the 17 modern individuals of C. carcharias as ana-
logs, ranged from 15.1 to 20.3 m, with a mean esti-
mate of 17.3 m. TL estimates for the smallest
associated dentition of O. megalodon, UF-VP-
460000, using the same modern analogs, ranged
from 9.4 to 12.7 m, with a mean estimate of 10.9
m. The range of estimates largely reflects the natu-
ral intraspecific variation exhibited in the modern
Carcharodon carcharias used as analogs. Thus,
there is an unavoidable range of error of approxi-
mately ± 1 to 3 m that is accounted for simply by
taking the mean value. This range of error is posi-
tively correlated with TL, meaning that there will
always be a greater range of estimates for larger
individuals.
Human observer error. The natural variability in a
species dental count is difficult to account for in dis-
articulated, associated dentitions of extinct taxa
and is, consequently, a potential source of human
error. The dental count for all Otodus dentitions
was based on the most complete known associ-
ated dentition (CH-31-46P), under the assumption
that the functional series in the left half of the denti-
tion was completely present (Figure 1B). Thus, it
was assumed that a complete functional series in
Otodus chubutensis and Otodus megalodon con-
sisted of 46 teeth (24 upper and 22 lower), which
meant that every associated dentition of Otodus
was missing at least one posterior tooth.
It is easy to imagine how posterior teeth could
be missing from these fossil dentitions. As the
smallest teeth in the dentition, they are the most
susceptible to being transported away through
taphonomic processes and would be the easiest to
simply not see while collecting the other teeth.
However, there is also the possibility that some of
these individuals had a dental count slightly differ-
ent from that of CH-31-46P, which would change
the corrected SCW and resultant TL estimates. For
example, in the largest associated dentition of O.
megalodon, UF-VP-311000, the corrected SCW
was calculated under the assumption that tooth
position L9 was not found but would have been
present (Figure 3A). If tooth position L9 was not
missing and the teeth recovered represent the
complete upper half of the dentition, the SCW
would be 1055.5 mm and the TL estimate would be
16.7 m (0.6 m smaller than the current estimate).
Likewise, we cannot be certain that this dentition
did not have a dental count greater than that of CH-
31-46P.
Every method that attempts to estimate body
size from teeth requires one to identify tooth posi-
tions, whether working with isolated teeth or asso-
ciated dentitions. When applying the Shimada
(2002a) method to samples of isolated teeth,
researchers often account for this by identifying
teeth to a range of potential tooth positions and
reporting the mean estimate. For example,
Pimiento et al. (2010) identified an isolated tooth of
O. megalodon (UF 246002) as belonging to tooth
position L7-L9, with a CH = 24.5 mm. Applying the
Shimada (2002a) method results in a range of TL
estimates from 16.5 to 34.2 m, with an average
estimate of 25.2 m. However, Pimiento et al. (2010)
reported a TL of 11.5 m for this specimen. Under
further inspection, Pimiento et al. (2010; figure S8)
incorrectly reported that the TL equation for tooth
position L9 from Shimada (2002a) as TL = -10.765
+ 17.616(CH). This is actually the equation for
tooth position i1 in Shimada (2002a; table 1). The
correct equation for tooth position L9 in Shimada
(2002a) was TL = -62.050 + 142.142(CH). This
obviously has a drastic effect on the body length
estimate and potentially major implications for the
conclusion that the Gatun Formation represented a
paleonursery for O. megalodon. Further, even with
the correct equations from the Shimada (2002a)
study, the range of error on the body length esti-
mate is approximately ± 9 m for this specimen,
which is much larger than any of the potential
sources of error discussed so far.

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
20
To develop the SCW method, we had to infer
which tooth positions were present in the disarticu-
lated, associated dentitions. Generally speaking, it
should be relatively easy to distinguish anterior vs
lateral teeth and upper vs lower teeth, based on
common trends observed in the typical lamnoid
tooth pattern, but it is extremely difficult to identify a
single tooth to an exact tooth position without con-
text. However, when you have multiple teeth pre-
served together, there is context for making that
determination. With a collection of associated
teeth, one can assume that the taller, more sym-
metrical teeth will be more anteriorly positioned
and the smaller, more asymmetrical teeth will be
more posteriorly positioned. Even if multiple teeth
were misplaced, as long as they are identified to
the correct quadrant, their CW will still be included
in the SCW. However, this could result in inaccu-
rate correction factors used to estimate CW of
missing tooth positions. At present, we consider
these reconstructions as a hypothetical model and
accept this as a source of error that cannot yet be
fully accounted for.
Yet another potential source of human
observer error is introduced while measuring spec-
imens. Linear measurements (CH and CW) were
recorded for teeth from 19 modern dentitions, 11
fossil associated dentitions, and one isolated fossil
tooth. Despite these measurements being clearly
defined, there will always be some degree of incon-
sistency between individuals. This source of error
is often disregarded, yet it is present. For example,
Shimada (2019) noted that Applegate and Espi-
nosa-Arrubarrena (1996) incorrectly reported the
TH for the largest known specimen of O. megal-
odon as 168 mm and stated that the correct TH is
162 mm. This changes the maximum TL estimate
reported by Gottfried et al. (1996) from 15.9 to 15.3
m. Therefore, using the TH linear regression, mea-
surement error may account for more than 0.5 m
difference in TL.
To account for this potential source of error,
authors VJP and RML independently measured
CH and CW in nine of the 19 modern analogs.
Body lengths were calculated using measurements
from both subsamples separately. TL estimates
using the SCW method varied by less than 0.2 m
for all individuals. Admittedly, this measurement
error likely also exists in the total body lengths
reported from the extant comparative individuals;
however, we cannot account for this variability, as
the measurements were not taken by the authors
of this study.
Mathematical equations. Methods for estimating
body length based on TH, CH, and SCW all follow
a similar logic that teeth grow proportionately with
total body length. In contrast with the results of
Reolid and Molina (2015), based on the sample of
modern C. carcharias from this study, for the A2
tooth position, there is comparable correlation for
CH and TL (r=0.99) versus CW and TL (r=0.97).
Likewise, the correlation between upper SCW and
TL (r=0.97) is comparable (Figure 8A).
Shimada (2019) determined that a power
function has a greater coefficient of determination
(R2) than a linear function when analyzing the rela-
tionship between CH and TL. The same is true
when analyzing the relationship between SCW and
TL (Figure 8). This can likely be attributed to the
greater variability in tooth proportions throughout
ontogeny (Hubbell, 1996; Tomita et al., 2017).
However, R2 values may not be appropriate for
determining which model is superior (Cornell and
Berger, 1987). R2 values are calculated differently
for linear and nonlinear functions, so they are not
necessarily directly comparable. Further, R2 values
are influenced by factors such as sample size and
sample distribution. By segmenting the dentition
into multiple regions to analyze variation within
individuals, we effectively increased our sample
size, which has an inverse effect on R2 values.
Thus, the higher R2 produced by the Shimada
(2019) power functions do not necessarily indicate
that the model is better than SCW power function
in this study.
To illustrate the variability associated with dif-
ferent mathematical assumptions, we estimated TL
using the SCW direct proportions equation, SCW
linear regression equation, and the SCW power
regression equation (Table 4). As is to be
expected, the SCW direct proportions and linear
regression result in nearly identical TL estimates.
Among the Otodus spp., in the upper dentition, TL
estimates vary by at most 0.1 m; however, for the
lower dentition, TL estimates vary by up to 0.8 m.
This further supports that there is greater variance
in the lower dentition. For the Otodus spp., the
SCW power function always results in a larger TL
estimate than the SCW direct proportions or linear
regression methods. Again, as one would expect,
the difference in TL estimates increases with larger
individuals; however, all estimates still fall within
the range of estimates produced by the SCW direct
proportions method. Among the Carcharodon spp.,
there is less than 0.1 m difference in estimates
derived from the SCW direct proportions, linear
regression, and power regression methods for both

PALAEO-ELECTRONICA.ORG
21
the upper and lower dentition. As such, we suggest
that either the SCW direct proportions or SCW lin-
ear regression should be used to estimate TL of
Otodus spp., whereas the SCW direct proportions,
linear regression, or power function can be used to
estimate TL of Carcharodon spp.
Paleoecological Implications
Body size estimates based on CH of isolated
Otodus megalodon teeth have been utilized to
identify paleo-nurseries (Pimiento et al., 2010; Her-
raiz et al., 2020) and as evidence for geographi-
cally discrete communities (Pimiento and Balk,
2015). These studies all employed the CH linear
regressions developed by Shimada (2002a) to esti-
mate body size, which result in widely variable esti-
mates when applied to Otodus spp. (Figure 7 and
Table 4). While applying the Shimada (2002a) lin-
ear equations to the associated dentitions in this
study, it became apparent that the variation in TL
estimates followed a predictable trend according to
tooth position, in which body length estimates gen-
erally increased from anterior to posterior tooth
positions (Figure 9A-B). Further, estimates from
the upper and lower dentition differed the greatest
in lateral tooth positions. This variability in esti-
mates derived from different parts of the dentition
has implications for the potential of sampling bias
affecting interpretations of body size trends in O.
megalodon.
In the Pimiento and Balk (2015) study, the
total sample consisted of 544 O. megalodon teeth.
Of which, 355 (65.2%) were identified as upper
teeth and 189 (34.8%) were identified as lower
teeth. Using a subsample of the 355 upper teeth,
body lengths were re-estimated by extrapolating
the SCW method. In general, the SCW method
resulted in larger TL estimates for anterior tooth
positions and smaller estimates for posterior posi-
tions than the CH method (Figure 9C-D). This
implies that the SCW method averages out the
variation associated with estimates from different
FIGURE 9. Variation in body length estimates by tooth position. (A-B) Body length estimates from each tooth position
in the Otodus megalodon dentition, using the Shimada (2002a) method. (A) CH-31-46P. (B) UF-VP-311000. (C-D)
Comparison of body length estimates based on the SCW vs. Shimada (2002a) CH method, using the sample of upper
teeth reported in Pimiento and Balk (2015). (C) SCW calculated using tooth proportions in CH-31-46P. (D) SCW cal-
culated using tooth proportions in UF-VP-311000. Positive values indicate that the SCW method results in larger TL
estimates than the CH method. Negative values indicate that the SCW method results in smaller TL estimates than
the CH method. Teeth are subdivided based on the tooth positions assigned by Pimiento and Balk (2015); however,
there is some overlap between categories given that some teeth were identified as antero-lateral (e.g., A1-L1) or lat-
ero-posterior (e.g., L3-L7).

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
22
tooth positions and explains why the Shimada
(2019) method always results in lower estimates
than the SCW method.
As for the Pimiento et al. (2010) study, we
pointed out that the TL equation for tooth position
L9 was incorrectly transcribed from the Shimada
(2002a) manuscript. Among the sample of 28 O.
megalodon teeth from the Gatun Formation, 20
were assigned to upper tooth positions. Three of
these teeth were identified as potentially belonging
to tooth position L9. After re-calculating TL with the
correct equation from Shimada (2002a), the esti-
mates for these three specimens are 16.9, 17.1,
and 25.2 m (Figure 10A). If we instead re-calculate
TL using the SCW method, with a subsample of
the 20 upper teeth, the range of estimates is much
lower (Figure 10B). Using the SCW method, the
same three specimens identified as possibly
belonging to tooth position L9 result in TL esti-
mates of 13.7, 13.8, and 11.5 m, respectively.
As such, the SCW method would actually pro-
vide better support for the hypothesis that the
Gatun Formation represented a paleo-nursery for
O. megalodon than the CH method. However,
there are two main caveats to this conclusion. First,
the life stages derived from Gottfried et al. (1996)
should be re-assessed, as it was stated that “esti-
mated lengths and mass for megatooth fetuses
and neonates … are speculative.” Shimada (2021)
reported a neonate TL of 2 m based on growth
bands in a disarticulated, associated vertebral col-
umn of Otodus megalodon (IRSNB 3121); how-
ever, this single individual is not sufficient evidence
for determining the size range of all O. megalodon
neonates. Second, if one were to use the SCW
method, the conclusion regarding the presence of
a paleo-nursery would be drawn from a sample of
only 20 teeth. That is a fairly small sample size to
support an inference about the reproductive and
distribution habits of an extinct species.
Maximum Body Length
As was described in the introduction, the max-
imum body size of O. megalodon has been revised
on numerous occasions. Gottfried et al. (1996)
reported a conservative maximum estimate of 15.9
m based on a maximum TH = 168 mm (FMNH PF
11306). However, Shimada (2019) noted that the
TH for FMNH 11306 was incorrectly reported and
is actually 162 mm, which would result in a TL of
15.3 m using the Gottfried et al. (1996) TH linear
regression. Alternatively, Shimada (2019) reported
a conservative maximum estimate of 14.2 m based
on a maximum CH = 120 mm (NSM PV-19896).
Larger TL estimates have been reported by
researchers that have attempted to employ the
Shimada (2002a) CH linear regressions to isolated
teeth (e.g., Pimiento et al., 2010: 16.8 m; Pimiento
and Balk, 2015: 17.9 m; Reolid and Molina, 2015:
20.3 m). However, these estimates are all deemed
unreliable based on errors in the data reported and
the inconsistent results that are produced by the
Shimada (2002a) method.
GHC 6 represents the largest tooth of Otodus
megalodon known and physically accessible to the
authors of this study (Figure 11A; TH=165 mm,
CH=122 mm, and CW=133 mm). This specimen
has a CH:CW of 0.917, which corresponds best
with tooth positions L1-L2 based on the two largest
associated dentitions of O. megalodon (UF-VP-
311000 and GHC 1). In UF-VP-311000, tooth posi-
tion L1 accounts for 10.5% of the SCW and tooth
position L2 accounts for 10.2% of the SCW (see
Appendix 5). The SCW direct proportions method
was extrapolated using these proportions, resulting
in a corrected SCW of 1266.7 to 1303.9 mm.
FIGURE 10. Re-calculation of Otodus megalodon body
lengths from Pimiento et al. (2010). (A) Re-calculation
using the correct equations from Shimada (2002a). (B)
Re-calculation using the SCW direct proportions
method, showing results based on CH-31-46P and UF-
VP-311000 as analogs separately.

PALAEO-ELECTRONICA.ORG
23
Based on a SCW of 1266.7 mm, the TL estimates
ranged from 17.4 to 23.5 m, with a mean estimate
of 20.0 m. Based on a SCW of 1303.9 mm, the TL
estimates ranged from 18.0 to 24.2 m, with a mean
estimate of 20.6 m.
One can quickly calculate the mean estimate
by directly comparing the proportions in UF-VP-
311000 and GHC 6 (Figure 11). This follows the
same principle that was used to develop the SCW
method. Since we are estimating body size based
on the tooth with the widest known CW, it seems
reasonable to assume that this tooth also repre-
sented the widest tooth in the dentition from which
it originated. In which case, the proportions of tooth
position L1 from UF-VP-311000 should result in the
best estimate. For this tooth position, the SCW
direct proportions method results in a TL of 20.0 m,
the SCW linear regression results in a TL of 20.1
m, and the SCW power regression results in a TL
of 21.6 m. We assume that the power regression
overestimates the TL and that the SCW direct pro-
portions and linear regression produce the more
reliable estimate. As such, we predict a maximum
body size for O. megalodon of approximately 20.0
m.
CONCLUSION
Through an evaluation of body length esti-
mates using fossil associated dentitions, it is evi-
dent that estimates based on crown height of
isolated teeth are highly variable when applied to
different tooth positions. Further, this variability fol-
lows a predictable trend, in which anterior teeth
result in smaller estimates than posterior teeth.
This has clear implications for previous studies that
FIGURE 11. Maximum body length estimation of Otodus megalodon. (A) Widest known tooth of O. megalodon (GHC
6), lingual view. The tooth enamel has been repaired inside the red polygon. Scale bar equals 5 cm. (B) Body length
calculation for specimen GHC 6, using the associated dentition UF-VP-311000 as an analog and assuming the tooth
represents position L1. SCWc = summed crown width corrected and TL = total body length. (C) Illustration depicting
the mathematical equation used to solve for body length. Otodus megalodon artwork by Tim Scheirer, used with per-
mission from the Calvert Marine Museum.

PEREZ, LEDER, & BADAUT: ESTIMATING LAMNIFORM BODY SIZE
24
have employed the Shimada (2002a) CH method
to analyze paleoecological and macroevolutionary
trends based on body size of Otodus megalodon.
Herein, a novel method was developed based
on summed crown width using fossil associated
dentitions. By segmenting the associated denti-
tions into different regions, we were able to assess
different sources of error that can affect body size
estimation of fossil lamniform sharks. Specifically,
estimates based on upper teeth are likely more
accurate than estimates based on lower teeth. This
is largely attributed to differences in the functional
role of upper versus lower teeth. This method pro-
vides significantly greater constraint on the resul-
tant body length estimate than the isolated CH
method but requires assumptions about the dental
pattern and count in the extinct megatooth lineage.
These associated dentitions represent the most
holistic direct evidence available to reconstruct the
dental and cranial anatomy of the megatooth lin-
eage but should still be treated as hypothetical
models until an articulated dentition is recover.
Based on a sample of 17 modern C. carcha-
rias dentitions, there was an approximately ± 1 to 3
m range of error in TL estimates for the eight asso-
ciated dentitions of Otodus spp. that can be
attributed to natural intraspecific variation. This
range of error increases for larger individuals.
While the sample size of fossil associated denti-
tions is not large enough to determine the size
range of the taxa analyzed in this study, we did
extrapolate the SCW method for the tooth of O.
megalodon with widest crown width (GHC 6) to
provide a maximum body size estimate. Assuming
this tooth represents position L1, the SCW direct
proportionality method results in a maximum body
length estimate of 20.0 m for O. megalodon, with a
range of error of approximately ± 3.5 m. Again, this
range of error reflects the natural variation in the
modern sample of Carcharodon carcharias used to
calculate TL.
ACKNOWLEDGEMENTS
This project would not have been possible
without the mentorship and support from G. Hub-
bell. Thank you for sharing your invaluable knowl-
edge on lamniform anatomy and evolution and
donating many of the specimens utilized in this
study. Thank you to S. Godfrey and D. Bohaska for
coordinating access to the Smithsonian collections.
We also appreciate personal communications with
M. Siversson and K. Shimada on previous studies
relevant to this research. Thank you to B. MacFad-
den, D. Jones, E. Martin, K. Bjorndal, and K. Crip-
pen for assistance in editing this manuscript and
advising us throughout this research project.
Finally, thank you to the reviewers and PE editorial
team for your valuable feedback. This study is
based upon work supported by the Florida Educa-
tion Fund McKnight Doctoral Fellowship, the
National Science Foundation Graduate Research
Fellowship program (Grant No. DGE-1315138),
and the National Science Foundation Advancing
Informal STEM Learning program (Grant No. DRL-
1322725). This manuscript is University of Florida
contribution to paleobiology number 879.
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APPENDICES
APPENDIX 1.
Crown width measurements in mm from modern Carcharodon carcharias (n=10) and Isurus oxy-
rinchus (n=1). Measurements are separated for the different regions preserved: upper left (UL),
upper right (UR), lower left (LL), and lower right (LR). (All appendices are available for download
in one zipped file at https://palaeo-electronica.org/content/2021/3284-estimating-lamniform-
body-size.)
APPENDIX 2.
Crown height measurements in mm from modern Carcharodon carcharias (n=10) and Isurus
oxyrinchus (n=1). Measurements are separated for the different regions preserved: upper left
(UL), upper right (UR), lower left (LL), and lower right (LR). * pathologic or broken. (All appendi-
ces are available for download in one zipped file at https://palaeo-electronica.org/content/2021/
3284-estimating-lamniform-body-size.)
APPENDIX 3.
Crown width measurements in mm of 11 fossil dentitions of Otodus and Carcharodon. Measure-
ments are separated for the different regions preserved: upper left (UL), upper right (UR), lower
left (LL), and lower right (LR). (All appendices are available for download in one zipped file at
https://palaeo-electronica.org/content/2021/3284-estimating-lamniform-body-size.)
APPENDIX 4.
Crown height measurements in mm of 11 fossil dentitions of Otodus and Carcharodon. Measure-
ments are separated for the different regions preserved: upper left (UL), upper right (UR), lower
left (LL), and lower right (LR). (All appendices are available for download in one zipped file at
https://palaeo-electronica.org/content/2021/3284-estimating-lamniform-body-size.)
APPENDIX 5.
Correction factors applied for missing teeth in fossil Carcharodon and Otodus dentitions. Correc-
tion factors for Carcharodon spp. are based on the mean percentage of the total summed crown
width from a sample of 10 modern C. carcharias dentitions (see Figure 6A-B). Correction factors
for adult Otodus megalodon are based on crown width proportions in UF-VP-311000. Correction
factors for juvenile Otodus megalodon are based on crown width proportions in CH-31-46P. Cor-
rection factors for Otodus chubutensis are from GHC 3. (All appendices are available for down-
load in one zipped file at https://palaeo-electronica.org/content/2021/3284-estimating-lamniform-
body-size.)