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First titanosaur dinosaur nesting site from the Late Cretaceous of Brazil

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Titanosaurs were successful herbivorous dinosaurs widely distributed in all continents during the Cretaceous, with the major diversity in South America. The success of titanosaurs was probably due to several physiological and ecological factors, in addition to a series of morphological traits they achieved during their evolutionary history. However, the generalist nesting behaviour using different palaeoenvironments and strategies was key to accomplish that success. Titanosaur nesting sites have been found extensively around the world, with notable records in Spain, France, Romania, India, and, especially, Argentina. Here, we describe the first titanosaur nesting site from the Late Cretaceous of Brazil that represents the most boreal nesting site for South America. Several egg-clutches, partially preserved, isolated eggs and many eggshell fragments were discovered in an Inceptisol palaeosol profile of the mining Lafarge Quarry, at the Ponte Alta District (Uberaba Municipality, Minas Gerais State), corresponding to the Serra da Galga Formation (Bauru Group, Bauru Basin). Although classical mechanical preparation and CT scans have not revealed embryonic remains in ovo, the eggs and eggshell features match those eggs containing titanosaurian embryos found worldwide. The morphology of the egg-clutches and observations of the sedimentary characteristics bolster the hypothesis that these sauropods were burrow-nester dinosaurs, as was already suggested for the group based on other nesting sites. The egg-clutches distributed in two levels along the Lafarge outcrops, together with the geopalaeontological data collected, provide clear evidence for the first colonial nesting and breeding area of titanosaur dinosaurs in Brazil.
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First titanosaur dinosaur nesting
site from the Late Cretaceous
of Brazil
Lucas E. Fiorelli1*, Agustín G. Martinelli2,3*, João Ismael da Silva3,4,
E. Martín Hechenleitner1,5, Marcus Vinícius Theodoro Soares6, Julian C. G. Silva Junior3,7,
José Carlos da Silva8, Élbia Messias Roteli Borges9, Luiz Carlos Borges Ribeiro3,8,
André Marconato10, Giorgio Basilici1,6 & Thiago da Silva Marinho3,11
Titanosaurs were successful herbivorous dinosaurs widely distributed in all continents during the
Cretaceous, with the major diversity in South America. The success of titanosaurs was probably due
to several physiological and ecological factors, in addition to a series of morphological traits they
achieved during their evolutionary history. However, the generalist nesting behaviour using dierent
palaeoenvironments and strategies was key to accomplish that success. Titanosaur nesting sites have
been found extensively around the world, with notable records in Spain, France, Romania, India, and,
especially, Argentina. Here, we describe the rst titanosaur nesting site from the Late Cretaceous of
Brazil that represents the most boreal nesting site for South America. Several egg-clutches, partially
preserved, isolated eggs and many eggshell fragments were discovered in an Inceptisol palaeosol
prole of the mining Lafarge Quarry, at the Ponte Alta District (Uberaba Municipality, Minas Gerais
State), corresponding to the Serra da Galga Formation (Bauru Group, Bauru Basin). Although
classical mechanical preparation and CT scans have not revealed embryonic remains in ovo, the
eggs and eggshell features match those eggs containing titanosaurian embryos found worldwide.
The morphology of the egg-clutches and observations of the sedimentary characteristics bolster
the hypothesis that these sauropods were burrow-nester dinosaurs, as was already suggested for
the group based on other nesting sites. The egg-clutches distributed in two levels along the Lafarge
outcrops, together with the geopalaeontological data collected, provide clear evidence for the rst
colonial nesting and breeding area of titanosaur dinosaurs in Brazil.
Titanosaurs were a group of successful quadrupedal herbivorous sauropod dinosaurs distributed worldwide
during the Cretaceous1,2 that achieved the largest sizes for animal on terrestrial environments3,4. ey have a
OPEN
1Centro Regional de Investigaciones Cientícas y Transferencia Tecnológica de La Rioja (CRILAR-CONICET-Provincia
de La Rioja-UNLaR-SEGEMAR-UNCa), Entre Ríos y Mendoza S/N, CP 5301 Anillaco, La Rioja, Argentina. 2Sección
Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”-CONICET, Av. Ángel
Gallardo 470, C1405DJR Buenos Aires, Argentina. 3Centro de Pesquisas Paleontológicas L. I. Price, Complexo
Cultural e Cientíco Peirópolis, Pró-Reitoria de Extensão Universitária, Universidade Federal do Triângulo
Mineiro, Rua Estanislau Collenghi 194, Uberaba, Minas Gerais 38039-755, Brazil. 4Fundação Cultural de Uberaba,
Prefeitura Municipal de Uberaba, Praça Rui Barbosa 356, Uberaba, Minas Gerais 38010-250, Brazil. 5Instituto de
Biología de la Conservación y Paleobiología (IBICOPA), DACEFYN-CENIIT-UNLaR, Av. Luis M. de La Fuente S/N,
CP 5300 Anillaco, La Rioja, Argentina. 6Department of Geology and Natural Resources, Institute of Geosciences,
State University of Campinas, Rua Carlos Gomes 250, Campinas, São Paulo 13083-870, Brazil. 7Laboratório de
Paleontologia de Ribeirão Preto, Faculdade de Filosoa, Ciências e Letras de Ribeirão Preto, Universidade de São
Paulo, Av. Bandeirantes, 3900, Ribeirão Preto, São Paulo 14040-901, Brazil. 8Faculdades Associadas de Uberaba
(FAZU), Fundação Educacional para o Desenvolvimento das Ciências Agrárias (FUNDAGRI), Associação Brasileira
dos Criadores de Zebu (ABCZ), Av. do Tutuna, 720, Tutunas, Uberaba, Minas Gerais 38061-500, Brazil. 9Escola
Estadual Presidente João Pinheiro, Rua Menelick de Carvalho 383, Boa Vista, Uberaba, Minas Gerais 38017-070,
Brazil. 10Departamento de Geologia Sedimentar e Ambiental, Instituto de Geociências, Universidade de São
Paulo, Rua Do Lago, 562, Cidade Universitária, São Paulo 05580-080, Brazil. 11Instituto de Ciências Exatas,
Naturais e Educação (ICENE), Universidade Federal do Triângulo Mineiro (UFTM), Av. Randolfo Borges Jr. 1400,
Univerdecidade, Uberaba, Minas Gerais 38064-200, Brazil. *email: lucasorelli@gmail.com; agustin_martinelli@
yahoo.com.ar
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mainly Gondwanan distribution1,5,6, with a peak of abundance and diversity during the Late Cretaceous in South
America2,7,8. Particularly, Brazil and Argentina, with almost 75% of the titanosaur species recorded in Patagonia2,
are the countries that have provided most of the species and specimens, with some of the largest and smallest
sauropod species known to date3,9. Sites around the world with a high abundance of fossil egg-clutches and
eggs, in some cases in tightly packed nesting colonies, are uncommon and highlight that titanosaurs success-
fully reproduced in disparate environmental conditions at dierent latitudes10,11. ese ndings are important
to acknowledge the complex and diverse reproductive biology of titanosaurs, because colony nesting entails
behaviours with diverse ecological and evolutionary benets. us, the colonial nesting behaviour of titanosaurs
is key to understanding their success and dominance over all continents during the Cretaceous.
Titanosaur nesting sites have been found extensively around the world, with notable records in Europe and
Asia1215. However, the best-known titanosaur sauropod nesting sites are located in Argentina, with several
prolic and remarkable localities2,1620. e nesting sites from Argentina have yielded an impressive number
of titanosaurian egg-clutches and even with embryo remains in ovo2,16,17,19,21. ere is no unambiguous taxo-
nomic certainty for these embryonic eggs, but it is likely that they belong to one of the two major groups of
Late Cretaceous titanosaurs, namely Saltasauridae and Colossosauria2. e combination of palaeontological
and sedimentological data from Argentinean sites, mainly in Patagonia and La Rioja Province, has provided
crucial information on their palaeobiology, life history, physiology and embryology, reproductive strategies
and nesting behaviours, as well as taphonomic and diagenetic processes associated with dinosaur eggs11,16,1825.
ese titanosaur egg-clutches of up to 30 spherical eggs, about 12–18cm in diameter, display a monolayered
shell traditionally classied within Megaloolithidae, a parataxonomic group without any modern biological and
evolutionary principles11.
Despite the extraordinary nesting sites in Argentina, records of titanosaur eggs or eggshells in other South
American localities are rare, with scarce evidences in Uruguay, Brazil and Peru2628. Particularly in Brazil, pub-
lished oological material of titanosaurs is limited to a few isolated, incomplete eggs and eggshell fragments
collected both at the “Ponto 1 do Price” site (Peirópolis) and Ponte Alta region2831. However, detailed studies
of titanosaur nesting sites in South America, outside of Argentina, are still lacking. Here, we report for the rst
time a high density of egg-clutches discovered in levels of the Serra da Galga Formation (Bauru Group)32 at the
abandoned mining Lafarge Quarry, located in the district of Ponte Alta (Uberaba Municipality, State of Minas
Gerais; Fig.1), which represents the rst conrmed titanosaur nesting site for the Late Cretaceous of Brazil and
the most boreal titanosaur nesting site in South America. We describe in detail the morphological features of the
egg-clutches, eggs, and eggshells, the geological and sedimentological characteristics of the egg-bearing levels,
and provide palaeobiological consideration of this nesting site. e sedimentologic and palaeontologic data col-
lected provide clear evidence for the rst colonial nesting area of titanosaur dinosaurs in Brazil.
Geological setting
e new titanosaur nesting site is located within the abandoned mining Lafarge Quarry, located about 2km west
of the rural town of Ponte Alta, Municipality of Uberaba, State of Minas Gerais, Brazil (Fig.1a,b). is quarry
is located about 35km east of Uberaba city and 8km east of the classic “Ponto 1 do Price” (near Peirópolis rural
town)31. e Lafarge Quarry is a limestone mine that was worked for 26years, reaching an extension of approxi-
mately 840,000 m2 (Fig.1d,e). According to Soares etal.32, the Lafarge Quarry type-section is interpreted as the
proximal zone of an ancient distributive uvial system. e stratigraphic interval is mostly constituted by laterally
extensive (up to 3km) calcrete beds (2–4m thick) that occur interbedded with few palaeosol proles (Fig.1c).
Internally, the calcrete beds display alpha-type (i.e., abiotic origin) carbonate microstructures (e.g., circum-
granullar crystallaria, crystalline calcite) that imprinted over conglomeratic and medium- to coarse-grained
sandstones32. e calcretization is inferred to have occurred via groundwater percolation through the permeable
channel deposits of the proximal zone. Conversely, the palaeosol proles correspond to pauses in sedimentation
related to the avulsion of channel belts to a distant position on the alluvial surface32. e duration of such breaks
in uvial sedimentation was estimated in c. 2.6–10 ky according to the degree of pedogenic carbonate cemen-
tation in palaeosols of the proximal zone (see Fig.13 in Soares etal.33). e titanosaur egg-clutches and other
vertebrate remains were recovered from the palaeosol interval between the two well-developed calcrete beds
(Fig.1d,e). Furthermore, the palaeosol sandy levels in the Lafarge Quarry also yielded other fossil occurrences,
including fresh-water gastropods, sh (scales and teeth), crocodyliforms (teeth) and titanosaur and theropod
dinosaur (teeth, bone fragments) remains, which will be described elsewhere. e Serra da Galga Formation32,
formerly known as the Serra da Galga Member of the Marília Formation, has a taxonomically diverse tetrapod
fauna including anurans (Baurubatrachus pricei and Uberabatrachus carvalhoi), fresh-water turtles (e.g., Pricemys
caiera, Cambaremys langertoni), a lizard (Pristiguana brasiliensis), crocodilyforms (e.g., Itasuchus jesuinoi, Pei-
rosaurus torminni, Labidiosuchus amicum), various theropod groups (e.g., abelisauroids, maniraptorans, birds),
and titanosaurians (Baurutitan britoi, Trigonosaurus pricei, Uberabatitan ribeiroi)31 and references herein. For
more information on the geology, sedimentology and palaeoecology of the region, we suggest the review papers
of Martinelli and Teixeira31, Soares etal.32,33, and Martinelli etal.34.
Systematic palaeontology
DINOSAURIA Owen, 1842
SAUROPODA Marsh, 1878
TITANOSAURIA Bonaparte & Coria, 1993
Titanosauria indet.
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Figure1. Geological map and sedimentology of Ponte Alta nesting site. (a) Location of thePonte Alta site
and the Serra da Galga Formation at the northeast margin of the Bauru Basin. (b) Lithostratigraphic map of
the study area with indication of the Ponto 1 do Price and Lafarge Quarry where the Ponte Alta nesting site is
located. (c) Stratigraphical section of the Serra da Galga Formation at the Lafarge Quarry with the provenance
of titanosaur egg-clutches. (d) Satellite image of Lafarge Quarry in 2003; map data: Google Earth Imagen©2018
Digital Globe. (e) Panoramic viewof theLafarge Quarry with the outcrops of the Serra da Galga Formation,
with the detail of the eggs bearing levels (arrows) and the stratigraphic section (ss). Modied from Soares etal.32.
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Note. We do not follow here the classic oologic parataxonomic methodology and classication because it
presents serious biological-evolutionary problems. In the section “On the methodology of egg parataxonomy”
in “Methods, we explain the problems and inconsistencies of this methodology. Here, we analyze the eggs within
the context of the evolutionary trend of amniotes, in particular focused on dinosaurs.
Material. CPPLIP 1798, clutch with ten eggs, of which ve are almost complete and spherical, all partially
inserted in the sedimentary matrix (Fig.2a); CPPLIP 1799, two spherical eggs and a fragment of a third within
the sedimentary matrix (Fig.2c); CPPLIP 1800, two almost complete and spherical eggs, with sedimentary
matrix and no clear association with other specimens (Fig.2d,e); CPPLIP 1801, an almost complete and spheri-
Figure2. Selected titanosaurian eggs and egg-clutches collected from the Late Cretaceous Serra da Galga
Formation (Bauru Group) at Ponto Alta nesting site, Uberaba Municipality, Minas Gerais State, Brazil.
(a) CPPLIP 1798, best-preserved recovered egg-clutch, bottom view. (b) CPPLIP 1801, isolated egg, with
accompanying tomographic slice, showing thickness of the shell and its sedimentary ll. (c) CPPLIP 1799, egg-
clutch with accompanying tomographic slice, showing thickness of the shell, shells collapsed and its sedimentary
ll. (d,e) CPPLIP 1800, two eggs found associated. (f) CPPLIP 1804 isolated partial egg. Scale bars 5cm.
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cal egg (Fig.2b); CPPLIP 1802, two associated, fragmented eggs (not gured); CPPLIP 1803, three associated,
fragmented eggs, two of them still within sedimentary matrix (not gured); CPPLIP 1804, two associated,
almost complete eggs and one holding the sedimentary mold of the another (Fig.2f).
Type locality and horizon. Ponte Alta nesting site, Lafarge Quarry, Ponte Alta, Uberaba Municipality,
Minas Gerais State, Brazil (Fig.1). Sandstone beds of the Serra da Galga Formation, Bauru Group, Bauru Basin
(Maastrichtian).
The Ponte Alta nesting site
e egg-clutch-bearing layers of Ponte Alta nesting site are distributed in the sandstone-palaeosol facies in
between the 8 and 12m of the stratigraphic section of the Serra da Galga Formation at the Lafarge quarry,
above the lowermost exposed calcrete level (Fig.1c–e)32 and the eggs have been collected within an area of
approximately ~ 240 m2. With exception of CPPLIP 1801, all other specimens were found approximately in the
same stratigraphic level (palaeosol, ~ 9 m in the stratigraphic prole), whereas the former specimen comes from
almost two meters above (10.7 m) representing at least two egg-bearing levels. Although several egg-clutches
were detected at the outcrop, just some were excavated and collected during the mining activities. CPPLIP 1798
is the best preserved and complete specimen of a partial clutch; it preserves a cluster of ten eggs and the clutch
appears to be rounded to elliptical in shape (Fig.2a). Of these, eight eggs can be observed in planar view, whereas
two lie below them, which indicate that the clutch consisted of at least two superposed rows of eggs (Fig.3). In
addition, the eggs that occupy the periphery of the lower layer in CPPLIP 1798 are slightly higher than those in
the center (Fig.3d).
Some eggs suered modern weathering (e.g., eroded section of eggs, breaks, wear of the surface of the shell—
external surface of eggshell units), but most are quite complete. Some eggs from Ponte Alta show compressions
and deformations (slightly attened with oblate-ellipsoid-like shapes, perpendicular to clutch plane; e.g., CPPLIP
1802–1803; Fig.2c–f), but in general they are perfectly spherical as other titanosaur eggs2,13,17,35,36. Most of eggs
are cracked and show a partially fractured shell surface, showing other typical taphonomic alterations by sedi-
ment load (Figs.2, 3). Because egg-surface fracturing results from sedimentary compression, we infer those
titanosaurs from Ponte Alta would have buried their eggs, which is also consistent with the superposed rows of
eggs (see taphonomic comments on “Discussion” section).
Figure3. CT scans of the best-preserved egg-clutch (CPPLIP 1798). (a) 3D rendering of the bottom of the
clutch in CPPLIP 1798. (b) General view of the clutch at the same orientation, showing the external part of the
lower hemisphere of the eggs. (c) Top view of the lower egg row, showing the inner part of the lower hemisphere
of the eggs. (d) Lateral view of CPPLIP 1798, showing lower egg row with higher shells at both ends and part of
the upper egg row. In dark orange, eggshell fragments within the eggs. Note that the incompleteness (“holes”) of
some eggs in B and C are due to the lack of the eggshells and/or poor resolution of the CT scan. In A the shape
of each egg is maintained due to the sedimentary internal mold. Scale bar 10cm.
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Despite these taphonomic alterations (mostly by pedogenesis), the eggs and their shells are generally very
well preserved (Figs.2, 4, 5). For those complete eggs with little deformations and breaks, we estimate an egg
average diameter and volume of 12cm and ~ 900 cm3, respectively (Fig.2). ese values are quite similar to
other titanosaur eggs from Argentina and Romania2,13,17,35, although slightly smaller (~ 15 to ~ 20cm) than other
alleged titanosaur eggs distributed worldwide15,17,19,20,36. e specimen collected from an upper level, CPPLIP
1801, includes an almost complete and sub-spherical egg, with its major axis measuring 14.2cm and a volume
close to 1500 cm3. Computed tomography analyses revealed some important aspects of the eggs and clutches
(Fig.3). First of all, CT scans exposed the spatial distribution of eggs and no embryonic remains in ovo, a reli-
able way to accurately identify the taxonomy of a fossil egg23. In CPPLIP 1798 (Fig.3b), some eggs have wide
broken openings and contain eggshell fragments on the opposite side. In contrast, no high concentrations of
shell fragments are evident outside the eggs, surrounding the clutch. Into the eggs, the eggshell fragments are
found immerse in the sedimentary matrix, randomly with their concave face up or down (Fig.3b–d). e lentil
shape of the eggs suggests compaction and lithostatic pressure. Seen in plain view, its circular section is evident,
but the shell is collapsed in the area of contact with two adjacent eggs (Fig.3c,d).
e single structural layer of Ponte Alta eggshells (Figs.4, 5) measures 1.1mm in average and is thinner
than other titanosaur eggshells. For example, the Tama eggshells averages 1.5mm in thickness20; eggshells from
Quebrada Santo Domingo, Auca Mahuevo, and Toteşti measure ~ 1.7 mm2,13,35; the mean thickness in Salitral
de Bajo deSanta Rosa and south of France eggshells is ~ 1.9 mm18,37, whereas in Dholi Dungri and other nesting
sites reach and exceed 2.5 mm17,19,36,38.
e eggshells are composed of densely packed fan-shaped discrete units (Fig.4). ese units vary between
350 and 600µm in diameter and are structured by closely packed rhombohedral acicular calcite crystals radiating
Figure4. Transmitted light microscopic views of radial thin section of eggshell fragments from Ponte Alta
nesting site showing the fan-shaped eggshell units. (a,b) Eggshells from CPPLIP 1798 clutch. (c,d) Eggshells
from CPPLIP 1800 and 1801, respectively. e base of a group of eggshell units may develop “football boot-
studs” shape. e matrix inlling of the eggs are represented by the sand and clayey matrix visible at the bottom
of the eggshells. eis eroded internal surface, ns nodular surface, pc pore canal, si silicication, sph spherulite, su
shell unit. Scale bar 1mm.
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from nucleation centers at the base of each unit (Fig.5). ere is no substantial sign of recrystallization and
pristine surfaces of small crystals of about 5µm are observed (Fig.5b,c). Although some show wear and erosion
(Fig.4), each unit exhibits the rounded convex top and collectively determines the profuse nodular external
appearance of the eggshell surface. e combination of all these features (i.e., spherulites, nodular ornamenta-
tion, eggshell units shape, rhombohedral acicular calcite crystals, etc.) constitutes the typical design of titanosaur
eggshells. e columnar base of each unit averages 250µm in diameter (Fig.5a,e); between each basal column,
the complex network of the horizontal pore system occurs, well-developed in titanosaur eggshells. In general,
the horizontal network is lled with sediment and there is no evidence of the brous membrana testacea beneath
the units (Fig.5e). Similar to the eggshell pores of Río Negro and Santo Domingo localities from Argentina2,18,21,
straight and uniform pore canals of around 50µm in diameter between the shell units are observed in the Ponte
Figure5. SEM images of eggshells from thePonte Alta nesting site(taken from the clutch CPPLIP 1798).
(a) Radial sections of pristine eggshells with some weathering outer (pore canal indicated by white arrows).
(b) Eggshell growth of lines showing the pristine calcite of the unit with the inlling of the pore channel
(white arrow) by secondary calcite deposits. (c) Original rhombohedric acicular calcite crystals forming and
structuring the unit. (d) Very characteristic double funnel-shaped wide pores. (e) Well-developed base of
eggshell units like “football boot studs” (white arrows) and the particularly evident network of horizontal pore
canals running in between (white crosses). Scale bars represent 500µm (a); 100µm (b); 10µm (c); 200µm (d,e).
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Alta specimens (Fig.5b). However, display other kinds of pores with a peculiar and atypical morphology (Fig.5d).
Unlike the traditional eggshell pores found in other titanosaur eggs, some pores of Ponte Alta eggshells are
very wide and have opposite and inverted double funnel-shaped, with large internal and external openings of
around 350µm and a medial bottleneck of around 100µm (Fig.5d). Moreover, the inner walls of these atypical
pores show smooth pristine surfaces with no signs of internal erosion or recrystallization. ese pores suggest a
particular adaptability to the nesting microenvironment and their morphology could represent an apomorphic
character for the titanosaur that nested in Ponte Alta site. In contrast to other titanosaur eggs, such those from
Auca Mahuevo, Toteşti, and Tama13,20,35, the eggshell pores from this Brazilian nesting site do not ramify with
a Y-shaped pattern.
Discussion
e Ponte Alta nesting site is the rst conrmed dinosaur nesting area for Brazil. No embryo remains have been
yet recovered in ovo at Ponte Alta to eectively conrm and identify these eggs; however, the morphological
features aforementioned of the eggs and eggshells perfectly match the eggs with titanosaur embryos found inside
at other nesting localities worldwide13,16,21,35,36. e egg-clutches, egg-shape and size, and the eggshell morphol-
ogy, e.g., the shape of units, the surface nodular ornamentation, and the vertical and horizontal pore network
system (Figs.35), suggest that the nests were made by titanosaurs and the occurrence of several clutches (Fig.2)
implies that in Ponte Alta there was a titanosaur nesting colony. During the Upper Cretaceous, between the
Santonian to Maastrichtian, only derived titanosaurs such as saltasaurids and colossosaurians are recorded in
South America2,7. However, only colossosaurian remains have been found so far in the Upper Cretaceous Bauru
Group of Brazil3943. is is highly suggestive that the Brazilian eggs, as with other Late Cretaceous embryonated
eggs16,21, belong to some of these late titanosaur clades.
Isolated or fragmentary remains of titanosaur eggs had been previously reported for the Cretaceous of Brazil,
even from the Ponte Alta region2831. From isolated and fragmentary egg remains, Grellet-Tinner and Zaher30
already suggested that a group of titanosaur sauropods were present and reproducing in the region during the
Late Cretaceous. Moreover, and because these animals would have had a generalized reproductive behaviour,
these authors suggested colonial nesting for the Bauru Basin titanosaurs. e new Ponte Alta specimens support
this hypothesis.
In addition to the colonial nesting behaviour, the nding of several eggs and egg-clutches accumulations
in at least two levels suggests breeding philopatry (or breeding-site delity) (Fig.6). is behaviour involves a
group of individuals returning periodically to the same location to breed44 and can be selected for, particularly
if local habitats are worth clinging to45. Besides, the population-level benet of breeding-site delity in many
cases requires nding better habitats, dispersion, and migration. Philopatry behaviour has been suggested for
Cretaceous titanosaurs due to large and recurrent nesting breeding areas2,13,16,19. In this sense, it has also been
suggested that many titanosaurs required specic conditions for nesting (e.g., at Sanagasta nesting site11,19) and
would have migrated in search of these peculiar nesting areas. Philopatric behaviour, in addition to other spe-
cic intrinsic and extrinsic characteristics, further supports the idea that titanosaurs were breeding migrants25.
Titanosaurs are known to nest in a wide range of environments and varied nesting behaviours11. According
to the fossil record, most species buried their eggs in the substrate to be incubated by solar or thermal heat,
although some would have possibly explored mound-building strategies11,15,19,20. e egg-clutches of the Ponte
Alta nesting site record two dierent levels within the palaeosol prole of the Serra da Galga Formation (Fig.6),
developed in Inceptisol palaeosols32. According to Soares etal.32, this Inceptisol palaeosol was formed in semiarid
and well-drained palaeoenvironmental conditions. Similar characteristics of palaeosols and pedofeatures are
seen in other titanosaur nesting sites (e.g., Tama nesting site)20,46 and suggest perhaps closely related titanosaur
groups. Moreover, this evidence and morphological features of the eggs and eggshells advocate a nesting strategy
similar to that displayed at Tama nesting site in La Rioja province, Argentina20,46. e palaeosol facies indicate
long gaps in sedimentation of up to thousands of years generating topographic stability ideal for the nesting
conditions of titanosaurs. Despite intense mining activity in Lafarge Quarry, the high density and co-occurrence
of multiple egg-clutches in the same Inceptisol level bolster the hypothesis of a large breeding colony of dinosaurs
in Ponte Alta (Fig.6).
Figure6. Model of events of titanosaur egg laying in two levels (L1 and L2), preservation, and subsequent
sedimentation in the Ponte Alta nesting site. (a) First level of eggs. (b) Repeated selection of the laying area (by
philopatry or breeding-site delity), excavation, and laying the eggs. (c) Covered eggs and a new deposition.
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CPPLIP 1798 clutch, conrmed by CT-based 3D reconstruction, shows a compact arrangement of the sub-
spherical eggs in two overlapping layers, which suggests insitu preservation and incubation within the sandy
substrate. CPPLIP 1798 is the most informative in terms of spatial distribution, with several eggs overlapping
and contacting each other. e arrangement in the lower layer, with central eggs located lower than those on the
periphery of the accumulation, is consistent with deposition in a bowl-shaped structure. is is a common feature
in titanosaur clutches and its nesting behavior due to buried nest building11,15,19,20,23. In addition, most eggs show
signs compatible with vertical compression due to sedimentary loading, such as the lentil shape and fractures
in one of the egg halves. Several eggs with wide openings could be also considered signs of biological activity,
either hatching or scavenging. However, these activities generally displace debris both inside and outside the
egg. In CPPLIP 1798 the missing fragments appear exclusively within each egg. Furthermore, numerous isolated
eggshells are immersed in the matrix, which suggests that they were incorporated as the sediment entered the
egg during diagenesis. ese patterns suggest that the eggs fractured aer the matrix lithied suering lateral
extension47. is proves that the eggs were complete at burial and titanosaurs from Ponte Alta buried their eggs.
e compaction by sedimentary load is also the most plausible hypothesis to explain the disposition of the broken
egg, whose debris is similar to that of another egg located further down.
Although it looks very similar to other titanosaur eggshells (e.g., Tama, Quebrada Santo Domingo, Auca
Mahuevo, or Toteşti), the thin shell of the Ponte Alta eggs displays some atypical pore canals. In addition to the
typical ne and straight pores with funnel-shaped openings, they display wide interspersed and apparently ran-
domly distributed pores. ese pores show wide internal and external funnel-shaped openings up to 350µm but
no forked Y-shaped pattern like in Auca Mahuevo, Toteşti, and Tama eggshells13,20,35. e pore canals facilitate gas
exchange through the eggshell and the supply of oxygen necessary for the embryo48. e pore canal morphology
and the characteristics of this complex respiratory system determine the gas conductance and the humidity in
the surrounding nesting environment49. Actually, it is the most informative trait of the eggshell and their micro-
nesting features20. e atypical wide opposite and inverted double funnel-shaped pores observed in the Ponte Alta
eggshells display pristine inner wall surfaces (Fig.5d). ese pores are not the product of dissolution, erosion,
recrystallization or any other taphonomic artefact, but their specic shape. ese peculiar wide pores would
have favored enormous gas diusion through the thin eggshell, while the constriction in the midsection—like a
bottleneck—would have restricted this diusion. us, these pores increase the pore area and could be a physi-
ological response in those cases of pores clogged by sand grains allowing a continuous exchange of gases and
maintaining a high diusion. Moreover, this suggests an adaptive response to reproduction under relatively arid
environmental conditions, a very common behaviour in mid-palaeolatitude titanosaurs25.
Regarding to the palaeolatitude, during the Late Cretaceous, Ponte Alta was located at about -26 degree
(similar to the Indian nesting sites), but lower than the other nesting sites in South America (between -33 to -47
degrees). is latitudinal dierence could also inuence the distribution of species on the Gondwana continent,
and the palaeoclimatic variation and geological characteristics could be determinant at the time of nesting.
Cretaceous titanosaurs once roamed over all continents, even walked in Antarctica. eir skeletal remains were
found everywhere16, whereas titanosaur nesting sites have more restricted distributions, being recovered in
Spain, France, Rumania (Laurasia) and Argentina, India, and now Brazil (Gondwana). However, the presence
of isolated eggs or eggshells in other areas (e.g., Peru, Uruguay)26,27 suggests geographically broader nesting
areas yet to be discovered. Tightly packed nesting colonies were seemingly very common among titanosaurs;
some South American colonies would have been really huge (e.g., Auca Mahuevo, Sanagasta, Santo Domingo,
etc.), establishing true titanosaur “rookery”. However, these rookeries developed with a strong dependency on a
wide variety of environments and exploited diverse nesting behaviors11, which would have been a tremendous
adaptive success for the group.
Conclusions
We report the rst dinosaur nesting area for the Cretaceous of Brazil, corresponding to several eggs and egg-
clusters discovered in the Serra da Galga Formation (Bauru Group) at the abandoned mining Lafarge Quarry,
in Ponte Alta region, Uberaba Municipality, Minas Gerais State. is titanosaur nesting site also represents the
most boreal one for South America, with a palaeolatitude similar to the one found in India. Fossil preparation and
CT scans of these egg-clutches have so far not revealed any embryonic remains in ovo. However, the egg-clutch
features and the macro- and micromorphology of the eggs and their eggshells match those titanosaur eggs found
worldwide which bolster the hypothesis of Late Cretaceous derived titanosaurs nesting in large colonial breeding
areas also in Brazil. Based on the depositional horizon and the macro- and micromorphology of the eggs, the
titanosaurs from Ponte Alta must have adopted a burial nesting strategy and the eggs were incubated in specic
conditions under environmental source heat. ese would have been commonly chosen nesting conditions by
lithostrotian titanosaurs. During Cretaceous times, titanosaurs lived on every continent, even Antarctica. e
worldwide evolutionary success of titanosaurs was due, among other things, to their great, quasi-general, adap-
tive behaviour to nest in colonial nesting areas and in several environments. However, the direct dependence
of its nesting behaviour to specic environments (e.g., arid palaeosols, hydrothermal environment, etc.) could
have played a key role as an extinction factor at the end of the Cretaceous.
Methods
Institutional abbreviations. CPPLIP, Centro de Pesquisas Paleontológicas “Llewellyn Ivor Price, Com-
plexo Cultural e Cientico de Peirópolis, Universidade Federal do Triângulo Mineiro, Peirópolis, Uberaba,
Minas Gerais, Brazil. All the egg-clutches, eggs, and eggshell fragments, petrographic samples and thin-sections
here studied are housed at the CPPLIP.
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Sample collection. Our data consist of titanosaur egg-clutches, eggs, and eggshell specimens collected
between 1998–2000 during mining work for the extraction of limestone in the now abandoned Lafarge Quarry
(Ponte Alta, Minas Gerais State, Brazil), where the Serra da Galga Formation is widely exposed32. e recovered
specimens were donated and incorporated into the CPPLIP collection through the management carried out by
two of the authors (JIDS and AGM). e exact point where the egg-clutches were found at the Lafarge Quarry
is here nominated “Ponte Alta nesting site” (GPS: S19° 42.634/W47° 40.534, 844m.a.s.l.). Several eggshell frag-
ments were selected for microscopy, on which were made thin sections for petrographic analyses as well as
coated with metal for scanning electron microscope (SEM) analyses and images. Comparisons with other eggs
and eggshells of titanosaurs were made on the basis of descriptions and gures in the literature as well as from
egg material studied rst-hand.
Eggshell thin sections. e thin sections of eggshell fragments were made at the Petrology Laboratory at
CRILAR (La Rioja, Argentina), using the following protocol for petrographic sectioning: the specimens were
washed in distilled water and cut with Petroin, dried at 40°C in an oven for 24h, glued with compound glue
(Araldit CY 248 and hardening HY 956) on glass slides of 28 × 48 × 1.8 mm3. Observations were obtained under
a Leica DM2500P petrographic microscope and images were captured with a digital camera (Leica DFC295)
attached to the microscope and connected to a computer for processing, editing, and measurements.
SEM analysis. e scanning electron microscopic analysis and preparation of the eggshell materials and
image captures were performed following50. Each specimen was mounted on an aluminium stub and coated with
gold/palladium for 15min (3 Armstrong/seg.) in a ermo VG Scientic SC 7620. e SEM observations were
conducted at 10kV with a LEO 1450VP Scanning Electron Microscope at the Microanalysis Laboratory of the
Universidad Nacional de San Luis (San Luis, Argentina; http:// labmem. unsl. edu. ar/).
CT analysis. Specimens CPPLIP 1798, CPPLIP 1799 and CPPLIP 1801 were scanned at the Toshiba
Aquilion®64 helical CT scanner of the Centro de Diagnóstico por Imagen, Hospital de Clínicas of the Universi-
dade Federal do Triângulo Mineiro (UFTM, Uberaba, Minas Gerais State, Brazil). CPPLIP 1798 has 512 images,
CPPLIP 1799 has 375 and CPPLIP 1801 has 157. e slices have 1mm of thickness, a voxel size of 938μm,
608μm and 361μm, respectively, and were done under 120 kVp and 200 μA. e three-dimensional reconstruc-
tions were performed by using the open source soware 3D Slicer.
Image and graphics design. CorelDRAW Graphics Suite 2020 and Adobe Photoshop CC14 were used for
storage and processing of the images, and nal design of the gures. All photos and drawings of the gures were
taken and drawn by the authors (LEF, AGM, EMH,and MVTS).
On the methodology of egg parataxonomy. Herein we do not follow the classic oologic parataxo-
nomic methodology and classication51 because it presents serious biological-evolutionary problems. We intro-
duce here some of them. Although parataxonomy is extensively used in studies of fossil eggs, we analyzed the
Ponte Alta eggs as a biological entity within the context of the evolutionary trend of amniotes. Aer fertilization
of an egg cell, the eggshell—and membranes—is an organic complex structure containing genetic information
of the female and combined genetic information in the embryo derived from the sexual reproduction (unless
parthenogenesis has occurred). Unlike the embryo, the rest of the egg (shell and membranes) is genetically
determined by the female. In general, the dinoavian eggshell is about 95% calcium-carbonate mineral—calcite—
and ~ 3.5% organic material/matrix52 (unlike bone tissues, which are generally made up of calcium phosphate
and organic materials in almost similar proportions). For that reason, the eggshell is a biocomposite ceramic
consisting of organic matrix—hundreds of identied proteins—and a crystalline calcium carbonate ller53. e
large number of proteins that make up the shell (e.g., ovocalyxin, lysozyme, ovalbumin, ovocleidin, cystatin,
osteopontin, ovotransferin, X-type collagen, keratan and dermatan sulfate, etc.) determine the processes of
deposition or inhibition of calcite—shell crystallization and pore, respectively54,55. In this sense, the eggshell is
a biomineralized structure which occurs in the uterus, and is the product of complex physiological processes
that depend on deep and precise hormonally and genetically synchronized moderators52,5458. Like bone tissue,
the dinosaur eggshell tissue is a bioceramic with phylogenetic information and provides multiple functions to
the embryo23,57,58. ere are at least four ways to determine the taxonomy of a fossil egg: (1) with an embryo
inside13,16,21,22,5961; (2) adults with eggs inside62; (3) adults brooding eggs63,64 and (4) by phylogenetic inferences
from the egg and its shell23,50,60. In most egg and eggshell fossil cases should be approached from this last per-
spective. us, the eggs described here certainly correspond to a specic dinosaur clade within Sauropoda and
their oological and reproductive features can be phylogenetically traceable23. And under the light of evolution-
ary biology, fossil egg parataxonomy classication is inappropriate. For these and other reasons, we do not use
it here.
Received: 4 January 2022; Accepted: 17 March 2022
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Acknowledgements
We thank to Lázara Marques da Silva Messia, Saulo Messias da Silva and José Fernandes Souto for their help to
make possible that the studied specimens be housed at the CPPLIP-UFTM. We thank to the sta of the Centro
de Diagnóstico por Imagem, Hospital de Clínicas of the Universidade Federal do Triângulo Mineiro (UFTM,
Uberaba, Minas Gerais State, Brazil), namely Cássio Vilela Komatsu, for the tomographies; to the technicians
Tonino Bustamante and Sergio de la Vega (CRILAR) for laboratory support and thin sectioning of eggshells, and
to Esteban Crespo (LABMEM, San Luis, Argentina) for his support with the SEM images. Special thanks to the
Llewellyn Ivor Price Paleontological Research Center and the Dinosaur Museum of the Cultural and Scientic
Complex of the Federal University of Triângulo Mineiro for their constant support to the research carried out
at this institution, oering structure and logistical support. In the same way, in these 30 years, its scientic col-
lection has been made available to Brazilian and foreign geoscientists. is research was partially funded by the
Conselho Nacional de Desenvolvimento Cientíco e Tecnológico (CNPq 305098/2018-7 to T.d.S.M.) and the
Agencia Nacional de Promociones Cientícas y Técnicas (PICT 2018-01211 to L.E.F.). Finally, the comments
provided by the Editor Jingmai O’Connor and two anonymous reviewers greatly improved the manuscript.
Author contributions
L.E.F., A.G.M., J.I.D.S. and T.D.S.M.: investigation (lead), coordinated the project and were involved in study
concept; M.V.T.S., G.B. and A.M. conducted the geological studies; A.G.M., E.M.H. and T.D.S.M. conducted
the CT image processing; L.E.F., A.G.M. and E.M.H. handled the analysis and SEM images; writing—original
dra (all authors).
Competing interests
e authors declare no competing interests.
Additional information
Correspondence and requests for materials should be addressed to L.E.F.orA.G.M.
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