Journal of South American Earth Sciences 39 (2012) 16e23
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Journal of South American Earth Sciences
journal homepage: www.elsevier.com/locate/jsames
Footprints of large theropod dinosaurs and implications on the age of Triassic
biotas from Southern Brazil
Rafael Costa da Silva a, *, Ronaldo Barboni b, Tânia Dutra b, Michel Marques Godoy c,
Raquel Barros Binotto d
a
CPRM e Companhia de Pesquisa de Recursos Minerais e Serviço Geológico do Brasil, Departamento de Geologia, Divisão de Paleontologia, Av. Pasteur, 404, Urca,
22290-240 Rio de Janeiro, RJ, Brazil
Graduation Program in Geology, Universidade do Vale do Rio dos Sinos e UNISINOS, Av. Unisinos, 950, 93022-000 São Leopoldo, Rio Grande do Sul, Brazil
c
CPRM e Companhia de Pesquisa de Recursos Minerais e Serviço Geológico do Brasil, Gerência de Recursos Minerais, Rua Banco da Província, 105, Santa Teresa,
90840-030 Porto Alegre, RS, Brazil
d
CPRM e Companhia de Pesquisa de Recursos Minerais e Serviço Geológico do Brasil, Gerência de Relações Institucionais e Desenvolvimento, Rua Banco da Província,
105, Santa Teresa, 90840-030 Porto Alegre, RS, Brazil
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 January 2012
Accepted 23 June 2012
Dinosaur footprints found in an outcrop of the Caturrita Formation (Rio Grande do Sul State, Southern
Brazil), associated with a diverse and well preserved record of fauna and flora, reopen the debate about
its exclusive Triassic age. The studied footprints were identified as Eubrontes isp. and are interpreted as
having been produced by large theropod dinosaurs. The morphological characteristics and dimensions of
the footprints are more derived than those commonly found in the CarnianeNorian, and are more
consistent with those found during the RhaetianeJurassic. The trackmaker does not correspond to any
type of dinosaur yet known from Triassic rocks of Brazil. Recent studies with the paleofloristic content of
this unit also support a more advanced Rhaetian or even Jurassic age for this unit.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Eubrontes
Dinosaur
Caturrita Formation
Gondwana
1. Introduction
The study of tetrapod fossil tracks provides a great amount of
data about diversity, functional morphology, behavior and ecological relationship of extant animals, beyond sedimentological
features of the substrate and paleoenvironmental aspects. Traditionally, they are not used for biostratigraphic purposes, although
they may be important for determining the age of successions
lacking body fossils or for the refinement of ages when associated
with them (e.g. Lucas, 1998; Lucas and Tanner, 2007).
In southernmost Brazil (state of Rio Grande do Sul), the Linha
São Luiz outcrop exposes levels of the Caturrita Formation and has
provided numerous and well preserved fossils, including cynodonts, dinosaurs, possible pterosaurs, sphenodontids, procolophonids, fishes, insects, conchostraca, invertebrate ichnofossils and
remains of several distinct types of gymnosperms. The diverse
fossil record of the Caturrita Formation and its lithological
* Corresponding author.
E-mail
addresses:
[email protected],
[email protected]
(R.C.da Silva), [email protected] (R. Barboni), [email protected]
(T. Dutra), [email protected] (M.M. Godoy), [email protected]
(R.B. Binotto).
0895-9811/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jsames.2012.06.017
relationships indicate an Early Norian age (Late Triassic) for this
unit (Rubert and Schultz, 2004), although more recent studies
suggest a NorianeRhaetian age (Abdala and Ribeiro, 2010).
Recently, two footprints were found in the upper portion of the
outcrop. Together with some paleofloristic and other paleofaunistic
data, it reopens the debate about the age of the Caturrita Formation.
This study aims to analyze these tracks and their paleontological
and geological context.
2. Material and methods
The studied material was identified at the Linha São Luiz
outcrop (29 330 4500 S; 53 260 4800 W), municipality of Faxinal do
Soturno, state of Rio Grande do Sul (Fig. 1), and consists of two
footprints preserved in a tabular sandstone layer that represents
the upper part of a rhythmic succession of sand and mud layers and
overbank deposits (crevasse splay). They received the field code
FSSL-01 and FSSL-02 (FS ¼ Faxinal do Soturno; SL ¼ São Luiz). The
first one was collected in 2008 and housed at the paleontological
collection of Museu de Ciências Naturais, Fundação Zoobotânica do
Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, under the
number MCN-PIC.030. The second footprint, FSSL-02, was found in
2009 less than a meter away from the first, covered by a layer of
R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23
17
Fig. 1. Location of the Linha São Luiz outcrop in the state of Rio Grande do Sul, Southern Brazil (based on Schultz et al., 2000).
sandy siltstone. It was studied and prepared in situ and kept in
place. This footprint was moistened to enhance the contrast for the
photographic record. A plaster model was made in the field and
deposited in the mentioned institution. The specimens were
prepared by mechanical processes. Footprint parameters were
based on Leonardi (1987) and measured using the computer
program ImageJ (Abramoff et al., 2004).
3. Geological context
The Caturrita Formation is considered a Triassic independent
unit from the Paraná Basin (Andreis et al., 1980; Faccini, 1989). It
was subdivided in two parts based on its fossil content (Zerfass
et al., 2003; Faccini, 2007). The basal one was considered Early
Norian due to its vertebrate fauna (Barberena, 1977; Schultz et al.,
2000; Rubert and Schultz, 2004), and the youngest one (“Mata
Sandstones”), probably Rhaetian by the presence of allocthonous
Araucarioxylon wood logs (Faccini, 1989, 2007; Guerra-Sommer and
Cazzulo-Klepzig, 2000).
According to sequence stratigraphic concepts, the Caturrita
Formation corresponds to a transgressive tract system that includes
two possibly incomplete third order sequences, deposited in
a tectonically and structurally disturbed area (Zerfass et al., 2003,
2004). Deposition occurred in high energy, low sinuous and
ephemeral river systems with associated plains or lakes in an
extensional basin, contemporaneous to those from Waterberg,
South Africa, and Cuyo and Ischigualasto, western Argentina
(Zerfass, 2007). The active tectonism that affected the Triassic
successions from Rio Grande do Sul (Andreis et al., 1980; Da-Rosa
and Faccini, 2005; Zerfass, 2007) led to a progressive increase in
accommodation rate that supported delta progradation and
longitudinal and transversal faults. The related block dislodgement
affect correlations.
The Linha São Luiz outcrop (Fig. 2) is about 20 m high and
composed of sandstones in the basal portion, mudstones in the
middle, and rhythmic sandstones and mudstones at the top. The
basal portion is composed of low angle cross bedded and well
sorted fine to medium sandstones, as well as short scale trough
cross-bedded sandstones (fluvial system) followed by massive or
sigmoidal trough cross-laminated fine sands associated with
crevasse deposits (Faccini, 2007), generated into a fluvio-deltaic
system (Faccini, 1989; Zerfass, 2007).
The following laminated mudstone-siltstone interval represents
a more permanent lake and yielded autochthonous and parautochthonous gymnosperm wood material (Pires and GuerraSommer, 2004; Dutra and Crisafulli, 2009), branches of diversified conifers and rare Equisetales, and impressions of sterile and
reproductive parts of Bennettitales (Wilberger et al., 2004; Barboni
and Dutra, in press), accompanied by conchostraca, insects and fish
scales. The upper portion of the outcrop is represented by heterolithic sandstone and mudstone deposits with evidences of
episodically subaerial exposure. These are considered to represent
a crevasse splay deposition and contain the two large dinosaur
footprints herein discussed, associated with desiccation cracks, in
the surface of a thick tabular sandstone layer.
4. Systematic ichnology
Ichnogenus Eubrontes Hitchcock, 1845
Eubrontes isp.
Material: MCN-PIC.030 and FSSL-02, isolated footprints (Fig. 3).
Description: The footprints are digitigrade, tridactyl and
mesaxonic, with acute digital extremities and hypices and with
a rear margin indented by a posteromedial notch or a heel-like
bulge. The footprint MCN-PIC.030 is incomplete due to erosion
and corresponds to the impression of a left foot with the plantar
portion, digit IV and the proximal portion of the digits II and III
preserved. Digit IV presents three phalangeal pads and a claw mark.
This footprint is oriented approximately to northwest, having 11 cm
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R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23
Fig. 2. Detailed section of Linha São Luiz outcrop, Paraná Basin, Southern Brazil. A, General view of the outcrop; B, Fluvial (base), lacustrine (middle) and crevasse splay (top)
deposits; C, General view of the crevasse splays deposits.
of sole length and 22 cm of sole width. The footprint FSSL-02
corresponds to the complete impression of a right foot, with the
digits medially curved. It is longer than wide and there are no
phalangeal or plantar pads. Digits II and IV are almost equal in
length while digit III is longer. This footprint is oriented approximately southeast and presents 43 cm of length and 39 cm of width.
Measurements of both footprints are given in Table 1.
Remarks: The footprints clearly fulfill the criteria of impressions
made by dinosaurs and cannot be confused with archosaurian
chirotheroid footprints due to the strong mesaxonic and digitigrade
pattern. The studied footprints can be attributed to Eubrontes due to
the totally digitigrade instance, the typical tridactyl theropod
morphology and the big size, longer than 28 cm (as defined by
Olsen et al., 1998). Morphologically, the studied material is closer to
Eubrontes veillonensis Lapparent and Montenat, 1967. However,
given the absence of trackways or more specific details, the identification at ichnospecific level is not possible. The footprints differ
from other ichnogenera of similar size like Gigandipus Hitchcock,
R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23
19
Fig. 3. Eubrontes isp., footprints from Caturrita Formation at Linha São Luiz outcrop. A, MCN.PIC.030, specimen at the field and after collecting; B, FSSL-02, specimen at the field on
the surface and cutted; C, Composite photograph illustrating the original position of the two footprints; D, Original and cast of the specimen FSSL-02.
1855 by the absence of hallux impressions, and Tyrannosauropus
Haubold, 1971 by the presence of longer digits in relation to the
sole. Gigandipus was also considered a behavioral variant of
Eubrontes (Rainforth, 2004, 2005). An isolated footprint resembling
the studied material was illustrated and briefly described by Turner
et al. (2009: 63) as “.Large ornithopod footprint cf. Wintonopus, ca.
Table 1
Parameters of the footprints from Caturrita Formation (L ¼ length, W ¼ width,
SL ¼ sole length, SW ¼ sole width, D ¼ divarication, TD ¼ total divarication). Linear
measures in cm.
MCN-PIC.030
FSSL-02
L
W
SL
SW
L II
L III
L IV
D IIeIII
D IIIeIV
TD
e
43
e
39
11
17
22
31
e
19
e
29
17
22
44
28
25
24
69
52
48 cm long.”, but this footprint does not match the diagnostic
patterns of that ichnogenus like the smaller size, broad digits with
rounded or bluntly angular tips, and digits III and IV close together,
parallel or slightly divergent.
5. Discussion
The two footprints identified as Eubrontes isp. are typical of large
theropod dinosaurs (e.g. Haubold, 1971; Thulborn, 1990; Lockley,
1991). The footprints are preserved in a tabular sandstone layer
and show signs of deformation. During the preparation in the field,
it was observed that the sandy siltstone layer that covers the
footprints was also deformed and revolved above them, what
means that the trackmaker stepped on the fresh silty sediment,
crossing through it and reaching the sand below (e.g. Brand and
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R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23
Kramer, 1996; Milàn and Bromley, 2006). The imprints are not
recognizable in the siltstone because of the semi-fluid nature of the
original substrate, but they are preserved in the sandstone. This
process may enhance the preservation potential of the footprints,
because eliminates the aerial exposure after their generation. It can
also explain the differences in size between the two footprints,
because the original footprint was probably larger than the
preserved one, with their size controlled by the depth of the
impression (Fig. 4). This kind of preservation can be understood as
a variation of the classic undertracks and ghostprints, and is similar
to what was called “cut undertracks” by Goldring and Seilacher
(1971). It was also noted in tracks preserved in grainflows of
dune deposits of the Lower Jurassic Navajo Sandstone, southwestern USA (Loope, 2006).
Also, there are no other, smaller tracks on the same surface,
which probably results from the “Goldilocks” effect as noted by
Falkingham et al. (2011). In such cases, only a narrow range of loads
can produce tracks, given that small animals failed to indent the
substrate.
The total divarication of the studied footprints is slightly higher
than the average for the ichnogenus Eubrontes, indicating that they
were produced on a softer and wetter ground. Footprints produced
on this kind of substrate tend to show higher divarication angles
than those produced on firm ground (Currie and Sargeant, 1979;
Thulborn, 1990). The heel-like bulges at the rear margin of the
footprints are occasionally produced when the foot does not sink
deeply into the substrate. Such features are usually found in
theropod footprints (Haubold, 1971; Thulborn, 1990), as those from
Northeast Brazil (Carvalho, 2000, 2004; Leonardi, 1994). It is not
possible to determine if the footprints were made by a single
trackmaker, because their size and direction are different.
The footprint FSSL-02 corresponds to a complete impression of
a right foot with 31 cm of sole width and 43 cm of total length. This
footprint was the base to estimate the size of the trackmaker
according to the equations used by Thulborn and Wade (1984) and
Thulborn (1989). Employing both methods discussed by those
authors: morphometric ratios (h ¼ 4.9 FL when footprint length
[FL] is higher than 25 cm, for large theropods) and allometric
equations (h ¼ 8.6 FL0.85, when FL > 25 cm), it was possible to
estimate the height at the hip joint (h) at 2.10 m, what corresponds
to an animal with up to 8 m long, similar in size to a big Allosaurus.
Currently, the known paleofauna of Linha São Luiz outcrop
includes mainly small animals, like the sphenodontian Clevosaurus
riograndensis (Bonaparte and Sues, 2006), the procolophonid
Soturnia caliodon (Cisneros and Schultz, 2003), the lepidosauriformes Cargninia enigmatica (Bonaparte et al., 2010a), the cynodonts Riograndia guaibensis (Bonaparte et al., 2001), Brasilodon
quadrangularis, Brasilitherium riograndensis (Bonaparte et al., 2003)
and Minicynodon maieri (Bonaparte et al., 2010a), the possible
pterosaur Faxinalipterus minima (Bonaparte et al., 2010b), and the
medium-sized dinosaur probably Guaibasaurus candelariensis
(Rubert and Schultz, 2004; Bonaparte et al., 2006). All of them are
restricted until now to the massive sandstones of the basal crevasse
splay deposits of São Luiz outcrop (Bonaparte et al., 1999, 2001,
2003, 2006, 2010b; Cisneros and Schultz, 2003; Martinelli et al.,
2005; Bonaparte and Sues, 2006; Arantes et al., 2009; Soares
et al., 2011a,b). As a whole, the paleofauna of Caturrita Formation
includes also the medium-sized dicynodont Jachaleria candelariensis (Araújo and Gonzaga, 1980), an indeterminate phytosaur
(Kischlat and Lucas, 2003), the cynodont Irajatherium hernandezi
(Martinelli et al., 2005), indeterminated sphenodontians, a stereospondyl temnospondyl (Dias-da-Silva et al., 2009), the dinosauromorph Sacisaurus agudoensis (Ferigolo and Langer, 2006) and
Unaysaurus tolentinoi (Leal et al., 2004), beyond more fragmentary
archosaur and cynodont remains (Dornelles, 1990; Ribeiro et al.,
2011).
Other dinosaurs recorded in the Brazilian Triassic include Pampadromaeus, Staurikosaurus, Saturnalia and also Grallator footprints
from the lower Santa Maria Formation (Colbert, 1970; Langer et al.,
1999; Silva et al., 2008; Cabreira et al., 2011). In addition, tracks
were previously recorded in the Caturrita Formation at the Novo
Treviso site and assigned to prosauropod dinosaurs (Silva et al.,
2007). However, those rocks were reinterpreted in a recent
mapping of the region as belonging to the Guará Alloformation,
Late Jurassic to Early Cretaceous in age (Scherer et al., 2000, 2001;
Zerfass, 2007). Dinosaur footprints were also recorded in other
outcrops of the Guará Formation and assigned to Sauropoda and
Theropoda (Schultz et al., 2003; Dentzien-Dias et al., 2005; Dias
and Schultz, 2005; Dentzien-Dias and Bertoni-Machado, 2005;
Scherer and Lavina, 2005). Thus, the structures found in Novo
Treviso are similar in age and shape to the other imprints from
Guará Formation and could be related to the same trackmakers.
Of the above mentioned taxa, none represent potential
producers for the footprints dealt with here. The largest known
dinosaurs from Caturrita Formation, U. tolentinoi and G. candelariensis, are considerably smaller than the Eubrontes trackmaker, as
well as the others known dinosaurs from the Triassic of the Paraná
Basin (Fig. 5). In fact, the Grallator footprints from Santa Maria
Fig. 4. Preservation of the footprints (specimen FSSL-02) as “cut undertracks”, in which the semi-fluid nature of the original substrate controlled the depth of the impression and
allowed the impression in already buried layers.
R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23
21
Fig. 5. Dinosaurs recorded in the Brazilian Triassic, based on body fossils and ichnofossils. Note the incongruent size of Eubrontes trackmaker compared to the others.
Formation (Silva et al., 2008) correspond to what would be expected for the Brazilian Triassic dinosaurs.
Ichnologists have long debated about the age of the oldest
occurrence of the ichnogenus Eubrontes. Haubold (1971) regarded
the occurrence of Eubrontes as spanning both Late Triassic and Early
Jurassic. Olsen and Galton (1984) proposed that its lowest occurrence matches with the base of the Jurassic, due to the correspondence between the appearance of this ichnogenus in the
Newark Supergroup and the Passaic palynofloral event (but see
Lucas and Tanner, 2007). Thereafter, most ichnologists began to
consider Eubrontes tracks as indicative of Jurassic age (e.g. Haubold,
1986; Lockley and Hunt, 1994). Indeed, Olsen et al. (2002a, 2002b)
concluded that the sudden appearance of Eubrontes giganteous in
the Early Jurassic of the Newark Supergroup indicates a dramatic
size increase in theropod dinosaurs at the TriassiceJurassic
boundary. However, E. giganteous appears to also occur in the
latest Rhaetian based on the new definition of the base Hettangian
GSSP (Olsen et al., 2011).
Triassic theropod tracks were revised by Lucas et al. (2006), who
assigned all tridactyl footprints longer than 25 cm to Eubrontes.
They listed distinct tracks, with varied sizes, from Australia (Carnian? 43 cm long), Southern Africa (Norian, up to 35 cm), Great
Britain (NorianeRhaetian, 26 cm), Switzerland (Norian, 25e30 cm),
France (Norian, 50 cm?; Rhaetian, 40 cm), Germany (Rhaetian,
25 cm), Sweden (Rhaetian, 32 cm) and Greenland (Norian, 28 cm).
However, the size criteria applied alone cannot provide a solid
ichnotaxonomic basis, and morphological elements should be
considered for an appropriated identification. They also argued that
the footprints from Great Britain, France, Germany and Greenland
are of grallatorid morphology. Lucas and Tanner (2007) also cited
that theropods large enough to have made at least some Eubrontessize tracks are known from the Late Triassic body-fossil record as
Liliensternus (Norian of Europe, estimated length of 5 m) and
Gojirosaurus (Norian of the USA, estimated length of 5.5 m), but
animals of this size do not explain the occurrence of footprints with
more than 30 cm long as those described. The problem of the
identification of some Triassic footprints as theropodan in origin
also has been discussed by several authors (e.g. Olsen et al., 1998;
Olsen et al., 2003; Lucas et al., 2006).
Although the subject is still far from being closed, it seems clear
that the emergence of Eubrontes trackmarkers occurred before the
beginning of the Jurassic, and that there are Triassic animals
capable of producing at least mid-sized Eubrontes-like footprints.
Nevertheless, there is an agreement between most researchers that
most Eubrontes tracks are clearly Jurassic, or at least that theropod
footprints with more than 40 cm in length, and with eubrontid
morphology, are more characteristic of the Jurassic.
The age of Caturrita Formation is also subject of discussion in the
literature. Rubert and Schultz (2004) proposed the Ictidosauria
Cenozone to the upper part of Caturrita Formation. Soares et al.
(2011a,b) have proposed to replace the “Ictidosauria Cenozone”
for the Riograndia Assemblage Zone. It was correlated with the
faunas of Los Colorados Formation, from Argentina, traditionally
placed in the Norian. A Norian age for the Caturrita Formation has
been used ever since, despite earlier works considered the deposition of the Los Colorados Formation as Rhaetian in age (Heckert
and Lucas, 1998; Lucas, 1998; Arcucci et al., 2004).
According to Abdala and Ribeiro (2010), a late NorianeRhaetian
age is more plausible for the cynodonts, as indicated by its correlation with the Los Colorados (Argentina) and the Elliot (South
Africa) formations faunas. The difficulties to correlate the faunistic
content of São Luiz exposition results from the different positions of
regional structural blocks due to fault displacements (Da-Rosa and
Faccini, 2005) and the endemic character of most of its faunal
components.
Other elements, such as J. candelariensis, apparently constrain
the age of the Caturrita Formation to the Triassic due to correlations
with the argentine basins and the extinction of the group at the end
of the Triassic (Schwanke and Araújo-Barberena, 2002; Rubert and
Schultz, 2004). However, remnants of dicynodonts with plesiomorphic characters have recently been identified in the Lower
Cretaceous of Australia (Thulborn and Turner, 2003). At this time,
however, no record of J. candelariensis occurs at São Luis outcrop,
which is known exclusively from one outcrop near Candelária,
50 km east of the site herein studied.
In relation to paleofloristic content, Barboni and Dutra (in press)
recently registered Bennettitales “flowers” in the São Luis outcrop.
The derived morphology of the female cone Williamsonia reinforces
a Rhaetian or younger age, which is also supported by comparisons
with other fossil floras, mainly those from Argentine basins (Artabe
et al., 2005; Menéndez, 1966; Barboni, 2010).
6. Conclusion
The studied footprints were identified as Eubrontes isp., and
their trackmarkers were most likely large theropod dinosaurs. The
morphological characteristics and dimensions of the footprints are
not commonly found in the CarnianeNorian, but more consistent
with those found after the RhaetianeJurassic. The trackmaker does
not correspond to any type of dinosaur known in Triassic rocks from
Brazil. The occurrence of the footprints, along with paleofloristic
and paleofaunistic data, indicate a Triassic age younger than
previously suggested for the Santa Maria Supersequence for the
upper portion of the Caturrita Formation or at least for the Linha
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R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23
São Luiz site, although an Early Jurassic age cannot be discarded.
More data and detailed studies of the fossil content are needed for
a better age estimate.
Acknowledgments
Thanks go to: Jorge Ferigolo and Ana Maria Ribeiro, Fundação
Zoobotânica do Rio Grande do Sul (FZB-RS), for receiving the
material in the collection; to Henrique Zerfass (Petrobras) for
assistance on the field and discussions on geology; and to CONDESUS (Consórcio de Desenvolvimento Sustentável da Quarta
Colônia) for technical support; and to Peter L. Falkingham
(University of Manchester) for the revision of the manuscript. We
also thank the anonymous reviewers and the Editor for the
suggestions. Financial support was provided by CPRMeServiço
Geológico do Brasil, CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), FAPERGS (Fundação de Amparo à
Pesquisa do Estado do Rio Grande do Sul) and UNISINOS (Universidade do Vale do Rio dos Sinos). Ronaldo Barboni thanks also
CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível
Superior) for his Master degree Grant.
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