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Fossil marine vertebrates of Cerro Los Quesos: Distribution of cetaceans, seals, crocodiles, seabirds, sharks, and bony fish in a late Miocene locality of the Pisco Basin, Peru


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One-hundred and ninety-two fossil marine vertebrate specimens, preserved as bone elements cropping out at Cerro Los Quesos (Pisco Basin, Peru), are identified and reported on a 1:4,000 scale geological map and in the corresponding stratigraphic section. All the fossils originate from the Pisco Formation, which is dated in this area to the late Miocene (from 7.55 Ma to ≥6.71 Ma, based on 40Ar/39Ar analyses of three volcanic ash layers along the section). Specimens are particularly concentrated near the top of the two main hills, where the geologically youngest portion of the examined section crops out. The impressive fossil assemblage includes cetaceans (91.6%), represented by mysticetes (balaenopteroids and cetotheriids) and odontocetes (phocoenids, physeteroids, and ziphiids, including the holotype of Nazcacetus urbinai). Seals, a crocodile, a seabird, bony fish, and sharks are also reported. Isolated large teeth of Carcharocles and Cosmopolitodus are common and, in several instances, associated to mysticete skeletons. Together with a similar work recently published for the other late Miocene locality of Cerro Colorado, this work represents a case study for the detailed inventory of the extraordinary paleontological heritage of the Pisco Basin. As such, it constitutes the basis for future taphonomic, paleoecological, and systematic studies, as well as for a much-needed conservation effort.
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Journal of Maps
ISSN: (Print) 1744-5647 (Online) Journal homepage:
Fossil marine vertebrates of Cerro Los Quesos:
Distribution of cetaceans, seals, crocodiles,
seabirds, sharks, and bony fish in a late Miocene
locality of the Pisco Basin, Peru
Giovanni Bianucci, Claudio Di Celma, Alberto Collareta, Walter Landini,
Klaas Post, Chiara Tinelli, Christian de Muizon, Giulia Bosio, Karen Gariboldi,
Anna Gioncada, Elisa Malinverno, Gino Cantalamessa, Ali Altamirano-Sierra,
Rodolfo Salas-Gismondi, Mario Urbina & Olivier Lambert
To cite this article: Giovanni Bianucci, Claudio Di Celma, Alberto Collareta, Walter Landini,
Klaas Post, Chiara Tinelli, Christian de Muizon, Giulia Bosio, Karen Gariboldi, Anna Gioncada,
Elisa Malinverno, Gino Cantalamessa, Ali Altamirano-Sierra, Rodolfo Salas-Gismondi, Mario
Urbina & Olivier Lambert (2016): Fossil marine vertebrates of Cerro Los Quesos: Distribution
of cetaceans, seals, crocodiles, seabirds, sharks, and bony fish in a late Miocene locality of the
Pisco Basin, Peru, Journal of Maps, DOI: 10.1080/17445647.2015.1115785
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Fossil marine vertebrates of Cerro Los Quesos: Distribution of cetaceans, seals,
crocodiles, seabirds, sharks, and bony sh in a late Miocene locality of the Pisco
Basin, Peru
Giovanni Bianucci
, Claudio Di Celma
, Alberto Collareta
, Walter Landini
, Klaas Post
, Chiara Tinelli
Christian de Muizon
, Giulia Bosio
, Karen Gariboldi
, Anna Gioncada
, Elisa Malinverno
Gino Cantalamessa
, Ali Altamirano-Sierra
, Rodolfo Salas-Gismondi
, Mario Urbina
and Olivier Lambert
Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy;
Scuola di Scienze e Tecnologie, Università di Camerino, Camerino, Italy;
Dottorato Regionale in Scienze della Terra Pegaso, Pisa, Italy;
Natuurhistorisch Museum Rotterdam, Rotterdam, The Netherlands;
Département Histoire de la Terre (CR2P - CNRS, MNHN, UPMC, Sorbonne Université) Muséum national dHistoire naturelle, Paris, France;
Dipartimento di Scienze dellAmbiente e del Territorio e di Scienze della Terra, Università di Milano-Bicocca, Milan, Italy;
Departamento de
Paleontologia de Vertebrados, Museo de Historia Natural-UNMSM, Lima, Peru;
Institut royal des sciences naturelles de Belgique, Brussels,
One-hundred and ninety-two fossil marine vertebrate specimens, preserved as bone elements
cropping out at Cerro Los Quesos (Pisco Basin, Peru), are identied and reported on a 1:4,000
scale geological map and in the corresponding stratigraphic section. All the fossils originate
from the Pisco Formation, which is dated in this area to the late Miocene (from 7.55 Ma to
6.71 Ma, based on
Ar analyses of three volcanic ash layers along the section).
Specimens are particularly concentrated near the top of the two main hills, where the
geologically youngest portion of the examined section crops out. The impressive fossil
assemblage includes cetaceans (91.6%), represented by mysticetes (balaenopteroids and
cetotheriids) and odontocetes (phocoenids, physeteroids, and ziphiids, including the
holotype of Nazcacetus urbinai). Seals, a crocodile, a seabird, bony sh, and sharks are also
reported. Isolated large teeth of Carcharocles and Cosmopolitodus are common and, in
several instances, associated to mysticete skeletons. Together with a similar work recently
published for the other late Miocene locality of Cerro Colorado, this work represents a case
study for the detailed inventory of the extraordinary paleontological heritage of the Pisco
Basin. As such, it constitutes the basis for future taphonomic, paleoecological, and systematic
studies, as well as for a much-needed conservation effort.
Received 13 August 2015
Revised 27 October 2015
Accepted 30 October 2015
Paleontological heritage;
marine vertebrates; fossils;
Miocene; Peru
1. Introduction
The lower portion of the Pisco Formation crops out in
the desert area of Ocucaje (Ica Region), along the
southern coast of Peru. This formation is famous for
its fossil marine vertebrates: the quality of the preser-
vation as well as the concentration of specimens places
this unit as one of the very best for the study of the
marine Neogene (Brand, Esperante, Chadwick, Poma,
& Alomía, 2004,2011;Bianucci et al., in press;Esper-
ante, Brand, Nick, Poma, & Urbina, 2008,2015). The
fossil assemblage of the Pisco Formation is also highly
diverse, including sharks and bony sh, marine turtles,
crocodiles, seabirds, baleen and echolocating toothed
whales, seals, and marine sloths (see Bianucci et al.,
in press and reference therein).
More specically, the Ocucaje area is characterized
by the presence of several hills (named cerros)
where an exceptional concentration of fossil ver-
tebrates is observed: the best known are Cerro la
Bruja (Lambert & Muizon, 2013;Lambert, Bianucci,
& Beatty, 2014a), Cerro Ballena (Brand et al., 2004),
and Cerro Colorado (Bianucci, Lambert, & Post,
2010;Collareta et al., 2015;Lambert, Bianucci, &
Post, 2010a, Lambert et al. 2010b,2015a;Parham &
Pyenson, 2010). Another equally important but less
known fossiliferous locality of this area is Cerro Los
Quesos, the type locality of the fossil beaked whale
Nazcacetus urbinai Lambert, Bianucci, & Post, 2009.
Although a preliminary study of Cerro Los Quesos
was undertaken by Esperante, Brand, Chadwick, and
Poma (2015), as for other fossiliferous localities in
the Ocucaje area, these authors focused their attention
only on baleen whales; surprisingly, in Cerro Los
Quesos they identied 42 mysticetes and only 2 pinni-
peds among the other vertebrates.
With a methodology and objectives similar to those
of a recently published work on the Cerro Colorado
locality (Bianucci et al., in press), this study presents
the rst complete census of the fossil vertebrates
found at Cerro Los Quesos. All specimens are reported
on a geological map and a precise stratigraphical pos-
ition is given for each fossil found.
© 2016 Giovanni Bianucci
CONTACT Giovanni Bianucci
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2. Geological and stratigraphic setting
The southern portion of the forearc Pisco Basin is a
180 × 30 km elongated sedimentary basin originating
from the subduction of the Nazca plate underneath
the South America plates in southern Peru (e.g.
Barazangi & Isacks, 1979;Cahill & Isacks, 1992;Pilger,
1981). The tertiary collision between these plates
deformed the leading edge of the South American
Plate and developed a composite transform-convergent
margin characterized by normal and strike-slip faults
that formed extensional/pull apart basins along
the western margin of Peru (e.g. León, Aleman, Torres,
Rosell, & De La Cruz, 2008;Thornburg &
Kulm, 1981;Zúñiga-Rivero, Klein, Hay-Roe, &
Álvarez-Calderon, 2010). The (East) Pisco Basin is
the onshore sector of one of these basins and its ll
comprises, from oldest to youngest, the Eocene Paracas
Group, the late Oligocene-middle Miocene Chilcatay
Formation, and the middle Miocene-Pliocene Pisco
Formation (DeVries, 1998;Dunbar, Marty, & Baker,
1990). These units are bounded by regional angular
unconformities recording discrete periods of subaerial
The layers of the Pisco Formation exposed at Cerro
Los Quesos are at least in part younger than that of the
layers farther north in Cerro Colorado (Di Celma,
Malinverno, Gariboldi, et al., in press); they consist of
sandstone, siltstone, and tuffaceous and diatomaceous
mudstone that form a gently east-dipping monocline
intensely dissected by almost-pure and oblique-slip
normal faults (Rustichelli, Di Celma, Tondi, & Bia-
nucci, 2016). Gariboldi et al. (2015) observed that a
consistent number of vertebrate fossils, both from
Cerro Colorado and Cerro Los Quesos, are included
inside dolomitic nodules and/or have dolomite-lling
bone cavities. Di Celma, Malinverno, Cantalamessa,
et al. (in press) described the geology of the Cerro
Los Quesos area and dened 6 informal members,
designated by the letters A through F in ascending
order, and 15 closely spaced marker beds allowing a
higher-than-usual stratigraphic resolution and the pre-
cise stratigraphic placement of the vertebrate fossils.
These marker beds were named (in ascending order)
Alcatraz, Araña, Árbol, Ballena, Colibrí, Cóndor,
Espiral, Estrella, Flor, Lagarto, Manos, Mono, Pájaro,
Pelícano, and Perro after the geoglyphs found in the
Nazca desert.
The area prospected for fossils in this study includes
the main hills of Cerro Los Quesos but not all the sur-
rounding areas investigated by Di Celma, Malinverno,
Cantalamessa, et al. (in press), where the lower portion
of the section crops out. Consequently, members A and
B and the lowest three marker beds (Alcatraz, Araña,
and Árbol) reported in Di Celma, Malinverno, Canta-
lamessa, et al. (in press) do not appear on the Main
3. Chronostratigraphic framework
Radiometric (
Ar) dating of biotite from three
volcanic ash layers of Cerro Los Quesos was published
by Di Celma, Malinverno, Cantalamessa, et al. (in
press). The stratigraphically lowest of the three dated
tuffs, resting directly on top of the Ballena marker
bed (31.4 m above the base of the section in Member
C), gave an age of 7.55 ± 0.05 Ma (all uncertainties
are given at the 95% condence level). The second
dated volcanic ash layer is the Mono marker bed
(142.3 m above the base of the section in the lower por-
tion of Member F), which provided an age of 6.93 ±
0.09 Ma. The stratigraphically higher tuff, exposed in
the uppermost part of the Cerro Los Quesos section
(193 m above the base), provided an age greater than
or equal to 6.71 ± 0.02 Ma. These ages are in agreement
with those reported as Kevin Nick, written communi-
cation, 2014by Esperante et al. (2015); these authors
reported an ArAr age from 7.73 to 7.11 Ma for
Cerro Los Quesos, but they did not provide any infor-
mation about the stratigraphical position of the dated
ash layers.
Biostratigraphic analyses based on diatoms substan-
tially agree with the radiometric ages (Di Celma,
Malinverno, Cantalamessa, et al., in press). Indeed,
the interval from 117.5 m to 141.3 m above the base
of the section (end of Member E and base of Member
F) is characterized by the co-occurrence of Nitzschia
porteri and Nitzschia miocenica. The rst has its last
occurrence at 7.1 Ma (ages for tropical planktonic
diatoms in the equatorial Pacic; Barron, 2003),
whereas the latter has its rst occurrence at 7.35 Ma
(low-latitude diatom zonation of Barron, 1985),
therefore biostratigraphically constraining this part of
the section between 7.35 and 7.1 Ma (base of the
N. miocenica zone in the low-latitude diatom zonation
of Barron, 1985).
In conclusion, both radiometric dating and diatom
analyses converge to indicate a late Miocene age (late
Tortonianearly Messinian) for the portion of the
Pisco Formation exposed in the study area, which is
signicantly younger than previously thought (Lam-
bert et al., 2009).
4. Study area and methods
From 2006 and during seven successive eld cam-
paigns, an area of approximately 4 km
was investi-
gated in detail at Cerro Los Quesos, Ica Region,
southern coast of Peru. The methods used in the eld
to collect global positioning system (GPS) receiver
coordinates and to establish a preliminary identi-
cation of the fossil specimens discovered are the same
as in a previous work in Cerro Colorado (see Bianucci
et al., in press for details). As for the latter locality, a few
highly signicant specimens were collected and
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deposited in the Museo de Historia Natural de la
Universidad Nacional Mayor de San Marcos
(MUSM) in Lima for preparation, study, and curation.
All fossil vertebrate specimens discovered were
reported on a 1:4,000 scale geological map; they were
positioned along the newly described sequence of dis-
tinctive marker beds and with a stratigraphic accuracy
from ±0.4 to ±3 m in a measured stratigraphic section
(Di Celma, Malinverno, Cantalamessa, et al., in press)
providing a framework for the spatial and temporal
distribution of all data, observations, samples, and
specimens collected or examined in situ in the course
of this long-term project.
Isolated shark teeth belonging to the genera Carch-
arinus, Carcharocles, and Cosmopolitodus, in several
cases strictly associated with other fossil vertebrate
skeletons, were reported on the map and along the stra-
tigraphic column as well. However, as already pointed
out by Bianucci et al. (in press), it should be noted that
different from other bony remains, isolated shark teeth
generally do not record the death of the animal, as one
shark can lose several thousand teeth in a lifetime. In
addition, the concentration of exposed large shark
teeth was observed to decrease signicantly over the
course of our subsequent eld campaigns, due to
their continuous looting.
A detailed taphonomic and paleoecological analysis
is beyond the aims of the present work, which consti-
tutes a starting point for further investigations and
comparisons among studied localities.
5. Overall composition of the vertebrate
A total of 192 marine vertebrate specimens preserved as
bony elements were recorded in the assemblage of Cerro
Los Quesos. Cetacean remains dominate the assemblage
(91.6% of the specimens), with a predominance of mys-
ticetes (42.2%), more than four times less odontocetes
(8.8%), and a relatively large number of more fragmen-
tary specimens noted as Cetacea indet. (40.6%) due to
their fragmentary state and/or to the partial burial-cov-
ering diagnostic features (Figures 13).
Among mysticetes, balaenopteroids are by far the
most common clade at Cerro Los Quesos, with many
specimens corresponding to at least partly articulated
skeletons; two to three species are tentatively identied,
characterized by distinct size ranges: the largest one
exhibits a skull about 3 m long and an estimated body
length of about 15 m; the smallest species has a skull
length and estimated body length of 1.6 and 8 m,
respectively; and an intermediate group of specimens,
with a skull about 2.5 m long and an estimated body
length of 1213 m, could either belong to the largest
species or to a third species. Although balaenopteroids
represent only 8.9% of the entire vertebrate assemblage
of Cerro Los Quesos, most of the indeterminate mysti-
cete remains and most of the indeterminate cetacean
remains (together representing 72.9% of the vertebrate
assemblage) correspond to large-size cetaceans that
more likely belong to Balaenopteroidea. Mysticetes are
Figure 1. Quantitative composition of the fossil vertebrate assemblage from the Pisco Formation at Cerro Los Quesos, based on
systematic surface prospecting. Isolated teeth of Elasmobranchii are not considered.
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also represented by at least two small cetotheriid skel-
etons sharing similarities with Piscobalaena nana (Pilleri
& Siber, 1989) from the latest Miocene of the Pisco For-
mation, in the Sacaco area (southern part of the Pisco
Basin; see Bouetel & Muizon, 2006).
The odontocete assemblage consists of phocoenids
(5.2%), physeteroids (2.1%), and ziphiids (1.5%). Pho-
coenids are represented by 10 more or less fragmentary
specimens, including several abraded skulls (two of
which were collected). Three of these remains show
afnities with, and can tentatively be referred to, Loma-
cetus ginsburgi (Muizon, 1986), originally described
from the Aguada de Lomas Level (AGL) of Sacaco
area (late Miocene of the Pisco Formation; Ehret
et al., 2012;Lambert & Muizon, 2013;Muizon, 1988).
Physeteroids include two skulls with associated mand-
ibles and teeth sharing similarities with (but not refer-
able to) Acrophyseter deionodon (Lambert, Bianucci, &
de Muizon, 2008) from Sud-Sacaco (latest Miocene,
Pisco Formation). The best preserved skull was
collected and prepared and is now under study.
Another skull collected belongs to a kogiid and displays
some afnities with Scaphokogia cochlearis (Muizon,
1988) also from the AGL level of Aguada de Lomas.
All ziphiid remains were collected; they are represented
by one skull with associated mandibles and cervical
vertebrae, described by Lambert et al. (2009) as the
holotype of N. urbinai, and by two other specimens
(an incomplete skull and mandible and a rostrum
with associated mandibles), now under study,
belonging to two distinct undescribed new genera
and species.
Non-cetacean marine vertebrates are represented by
eight partial pinniped skeletons (4.2%, family Phoci-
dae), one partial disarticulated skeleton of a marine
crocodylian (0.5%) with osetoderms very similar to
those of Piscogavialis jugaliperforatus (Kraus, 1988)
from Sud-Sacaco, one fragmentary postcranial skeleton
of a Phalacrocorax-like seabird (0.5%), a few bones
belonging to three bony sh specimens (1.6%), and
Figure 2. Fossil vertebrates from the Pisco Formation at Cerro Los Quesos. (a) Partially articulated skeleton of a medium-size balae-
nopteroid mysticete. (b) Disarticulated skeleton of large-size balaenopteroid mysticete.
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three partial skeletons with associated teeth of sharks
(1.6%, two belonging to Cosmopolitodus hastalis and
one to Carcharinus leucas). Isolated teeth of Carcharo-
cles megalodon and C. hastalis are common. Teeth of C.
leucas and of the ray Myliobatis sp. were found around
a large balaenopteroid skeleton during its excavation.
6. Fossil distribution
For what concerns the spatial and vertical distribution
of fossils, the most striking observation is the concen-
tration of fossil vertebrates at the top of the two hills,
where the geologically youngest portion of Member F
crops out (Figure 4). Indeed, analyzing the fossil
distribution along about 200 m of section, it appears
that 178 specimens (92.7% of the total) are inside
Member F. Within the latter, 166 specimens (86.5%
of the total) are concentrated in an interval of 40 m
of sediments (140180 m from the base of the exam-
ined section). Inside these 40 m of the section there
are more than 10 peaks of concentration and in some
cases the corresponding fossils appear in the eld
very close to each other and with similar orientations
of skeletons. These peaks could represent single cata-
strophic-like episodes of deposition. Although only
two large peaks and a third smaller peak are observable
in the simplied large-scale section (Figure 5), this
pattern is especially conspicuous in the detailed
Figure 3. Fossil vertebrates from the Pisco Formation at Cerro Los Quesos. (a) Articulated skeleton of a large-size balaenopteroid
mysticete inside a dolomitic nodule. (b) Partial articulated skeleton of a small-size balaenopteroid mysticete. (c) Portion of articu-
lated skeleton of Piscobalaena-like cetotheriid mysticete. (d) Abraded skull of a Lomacetus ginsburgi-like phocoenid odontocete. (e)
Several associated shark teeth belonging to the same individual of C. hastalis.
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small-scale section included on the Main Map. Isolated
teeth of C. megalodon and C. hastalis are also common
in this 40 m part of the section, with several cases
associated to mysticete skeletons.
Apparently absent in the rst 35 m of the examined
section, the remaining fossil vertebrates are more or
less uniformly distributed in the lower strata forming
Members C, D, and E .
Two parameters may contribute to the non-homo-
geneous vertical distribution of the fossil vertebrates
across the mapped area. Although a non-homogenous
vertical distribution of fossils in the strata seems to be
a predominant factor, the resulting distribution is also
impacted by recent morphological changes in the land-
scape. Indeed, smaller portions of horizontally deposited
skeletons are exposed along a steep slope, contrasting
with less inclined outcropping surfaces. Furthermore,
specimens on slopes are subject to greater erosion
rates with respect to specimens on the top of the hill.
Interestingly, with the exception of a pinniped skel-
eton found near the base of the exposed section, all the
fossils of Cerro Los Quesos were deposited during an
interval time of not more than 0.84 million years, as
they are all included in a 161.6 m thick interval between
a lower and an upper ash layer that provided a radio-
metric dating of 7.55 and 6.71 Ma, respectively (Di
Celma, Malinverno, Cantalamessa, et al., in press). More-
over, only not more than 0.22 million years separate the
two uppermost ash layers (in Member F, dated to 6.93
and 6.71 Ma, respectively by Di Celma, Malinverno,
Cantalamessa, et al., in press), for a 50.7 m thick interval.
When analyzing separately the vertical and horizon-
tal distribution of each identied taxon, no substantial
differences are observed; where fossils are abundant
mysticetes remain common, whereas pinnipeds (pho-
cids) are represented by only a few remains distributed
along the whole exposed section. Two exceptions are
represented by birds and crocodilians, which are both
Figure 4. Map of the investigated area of Cerro Los Quesos showing the whole fossil vertebrate distribution.
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represented by a single specimen located in the part of
the section corresponding to the highest peak of fossil
7. Conclusions
As for the recently published paper about Cerro Color-
ado (the type locality of the giant raptorial sperm whale
Livyatan melvillei), this work provides a combined
quantitative and qualitative evaluation of the distri-
bution of marine vertebrates in a fossil-rich late Mio-
cene (late Tortonianearly Messinian) Pisco
Formation locality.
The combination of a detailed geological and strati-
graphic study with the prospection and mapping of
fossil vertebrates allowed positioning of all the fossils
on a geological map and along the related stratigraphic
section. This is the best way to provide a precise over-
view of the spatial and stratigraphic distribution of the
192 specimens discovered. More specically, most of
the fossils are concentrated near the top of the two
hills, where proportionally larger surfaces of outcrops
are available: 166 specimens (86.5%) originate from
the interval between 140 and 180 m above the base of
the Cerro Los Quesos section.
Based on the systematic eld determination of the
mapped specimens, important information on the
composition of the fossil assemblage is obtained. The
Cerro Los Quesos assemblage is dominated by
cetaceans (91.7% of the specimens), with 42.2% of
the total represented by mysticetes, 8.8% by odonto-
cetes, and 40.6% by indeterminate cetaceans (with a
Figure 5. Stratigraphic distribution of fossil vertebrates at Cerro Los Quesos.
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majority of the latter probably being balaenopteroid
Because of the possible occurrence of the phocoenid
Lomacetus ginsburgi and the kogiid S. cochlearis,two
species only collected so far in the AGL level, a corre-
lation of the Cerro Los Quesos beds with those of the
AGL level at Aguada de Lomas (a locality of the Sacaco
area 150 km SE to Cerro los Quesos) is tentatively
suggested. As a matter of fact, the time range provided
by the radiometric dating at Cerro Los Quesos (7.55
6.71 Ma) approximately matches the rough estimation
(7.57 Ma) proposed by Muizon (1988) for the AGL
level at Aguada de Lomas (see also Ehret et al., 2012;
Lambert & Muizon, 2013).
Similar to the work done in Cerro Colorado, this
study provides a vast amount of data to be used in
different studies: (1) reconstruction of the ecological
structure of the vertebrate assemblage at Cerro Los
Quesos; (2) observation of faunal changes across the
section and tentative correlation with sedimentological
changes (more specically the deposition of diatomites
and volcanic ash layers); (3) taphonomic analysis of the
exceptional conservation of this fossil assemblage
(including multiple fully articulated large mysticete
skeletons); (4) systematic and phylogenetic studies of
signicant specimens belonging to new taxa (speci-
mens of cetaceans and sharks have been collected
and are currently under preparation), in a strati-
graphic, sedimentologic, and faunal framework mark-
edly more precise than in earlier work.
In addition, this work represents the second step of a
long-term and multidisciplinary project undertaking
(1) the production of similar maps of fossil vertebrates
from other localities of the Pisco Formation, and (2)
from localities of the older and seemingly fossiliferous
Chilcatay Formation (e.g. Ullujaya, see Bianucci,
Urbina, & Lambert, 2014;Lambert, Bianucci, &
Urbina, 2014b; Lambert, de Muizon, & Bianucci,
2015b), as well as (3) attempts to correlate stratigraphi-
cally distant localities and to compare their marine ver-
tebrate content and changes through time.
Finally, the results of this work together with future
studies in other localities should be added to data gath-
ered from Cerro Colorado in a general database for the
paleontological content of Pisco Basin fossiliferous
localities. Such a database will be made available to
the community for various future projects (involving
research, mining, construction, recreation, and tourist
activities in the Pisco Basin area), with the general
aim of preserving and valuing this exceptional Peru-
vian heritage.
The geological map was compiled by scanning hand
drafts as black and white TIF les, and then digitizing
the linework using the Corel Draw X3 graphics
package. By using the GIS Data processing application
Global Mapper 12, contour lines for the topographic
base map were generated from digital elevation models
(DEMs) based on the Shuttle Radar Topography Mis-
sion 26 (SRTM) as released by the United States Geo-
logical Survey (SRTM3 USGS version 2.1). Positions of
fossil specimens were superimposed on the outcrop
pattern of distinctive marker bed horizons by using
Global Mapper 12 to convert a Google Earth kmz le
containing their position into Corel Draw.
We would like to thank W. Aguirre, E. Díaz, J. Tejada,
N. Valencia, and R. Varas-Malca for their kind and
endless help in the eld and at the MUSM, and
T. DeVries for valuable comments about various gen-
eral aspects of the geology and stratigraphy of the
Pisco Formation. We also wish to thank J. Reumer
(Natuurhistorisch Museum Rotterdam, NMR) for his
participation in the eldtrip in 2008. C. Brochu, P.D.
Gingerich, and M. Murad-al-shaikh reviewed the
manuscript and provided constructive comments.
Disclosure statement
No potential conict of interest was reported by the authors.
This research was supported by a grant of the Italian Minis-
tero dellIstruzione dellUniversità e della Ricerca (PRIN
Project 2012YJSBMK), by the University of Pisa
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... Previous studies have focused on exposures of the Pisco Formation along the lower Ica Valley, which features several hills (locally known as "cerros") with abundant fossil vertebrate assemblages [25,26]. The Pisco Formation in this area is about 470 m thick and comprises three depositional sequences/allomembers named P0, P1, and P2, respectively ( Figure 1C) [10,33,53,54]. ...
... Most recently, work in the Ica Valley has focused on an interdisciplinary approach to reconstructing the age, palaeoenvironmental setting, preservation, and ecological structure of the Pisco vertebrate assemblages, with an initial focus on the particularly rich sites of Cerro Colorado and Cerro Los Quesos [21,22,[25][26][27]29,53,54,[89][90][91]. This long-term research effort, subsequently extended to other sites and strata [10,13,14,23,24,28,30,33,55,92,93], provides a solid basis for elucidating the interplay of upwelling, volcanic ash fertilization, primary productivity, trophic ecology, diatom deposition, and fossil diagenesis in the ancient Humboldt Current Ecosystem. ...
... For some 15 field seasons, we conducted a detailed census of the vertebrate fossils at the localities of Cerro Colorado, Cerro Los Quesos, and Cerro Submarino [24][25][26], supplemented by data from Cerro Ballena, Cerro Blanco, Cerro Geoduck, Cerro Hueco la Zorra, Cerro La Bruja, Cerros Cadenas de los Zanjones, Cerros la Mama y la Hija, Corre Viento, Laguna Seca, and Quebrada del Toro Chico. We searched for fossils via systematic surface prospecting and, for each specimen, recorded: (i) its exact location, (ii) a preliminary identification, (iii) a concise description, and (iv) taphonomic observations regarding articulation, completeness, disposition and orientation, bite marks, associated faunal elements (including putative digestive tract content), the presence of a concretion, the extent of erosion, and associated sedimentary structures (see also Bosio et al. [30]); furthermore, whenever possible, we also recorded: (v) basic measurements (including the total length of the skeleton, and the condylobasal length and bizygomatic width of the cranium), and (vi) the degree of fusion of the vertebral epiphyses. ...
Full-text available
The northward-flowing Humboldt Current hosts perpetually high levels of productivity along the western coast of South America. Here, we aim to elucidate the deep-time history of this globally important ecosystem based on a detailed palaeoecological analysis of the exceptionally preserved middle–upper Miocene vertebrate assemblages of the Pisco Formation of the East Pisco Basin, southern Peru. We summarise observations on hundreds of fossil whales, dolphins, seals, seabirds, turtles, crocodiles, sharks, rays, and bony fishes to reconstruct ecological relationships in the wake of the Middle Miocene Climatic Optimum, and the marked cooling that followed it. The lowermost, middle Miocene Pisco sequence (P0) and its vertebrate assemblage testify to a warm, semi-enclosed, near-shore palaeoenvironment. During the first part of the Tortonian (P1), high productivity within a prominent upwelling system supported a diverse assemblage of mesopredators, at least some of which permanently resided in the Pisco embayment and used it as a nursery or breeding/calving area. Younger portions of the Pisco Formation (P2) reveal a more open setting, with wide-ranging species like rorquals increasingly dominating the vertebrate assemblage, but also local differences reflecting distance from the coast. Like today, these ancient precursors of the modern Humboldt Current Ecosystem were based on sardines, but notably differed from their present-day equivalent in being dominated by extremely large-bodied apex predators like Livyatan melvillei and Carcharocles megalodon.
... The Pisco Formation, exposed in the Ica Desert of southern coastal Peru, is a globally significant fossil deposit known for its outstanding assemblage of Miocene sharks and rays, bony fishes, marine turtles and crocodiles, seabirds, cetaceans, and pinnipeds [10][11][12][13][14][15][16][17][18][19][20][21]. Four decades of research on these specimens have unveiled an unusual quality and quantity of palaeontological information, thus qualifying the Pisco Formation as a Fossil-Lagerstätte (as per the original definition by Seilacher [22]) [14,23,24]. ...
... More recently, a multidisciplinary team of palaeontologists, stratigraphers, sedimentologists, micropalaeontologists, and mineral scientists conducted a multi-year investigation of the taphonomic processes at play during the deposition of the Pisco Formation. Results from this programme include detailed censuses of key localities [17,18,35], their contextualisation into a comprehensive chronostratigraphic and palaeoenvironmental framework [19,[36][37][38], detailed investigations of exceptionally preserved specimens [25,26,[28][29][30], and preliminary insights into early diagenetic processes [23,24,39,40]. ...
... Starting in 2006, and for some 15 field seasons, our multidisciplinary team focused on establishing a detailed census of the fossil vertebrates cropping out at several fossil-rich exposures of the Pisco Formation. Preliminary results of this long-term research effort included the production of detailed thematic maps displaying the spatial and stratigraphic distribution of hundreds of fossil vertebrates from the key localities of Cerro Colorado, Cerro Los Quesos, and a broad area in the vicinity of Cerro Submarino [17,18,35]. Here, we apply a similar approach to a total of 16 localities (Fig 2), including the aforementioned three, which together involves first-hand observations on 890 vertebrate fossils. ...
Full-text available
The Miocene Pisco Formation, broadly exposed in the Ica Desert of southern Peru, is among the most outstanding Cenozoic marine Fossil-Lagerstätten worldwide. It is renowned for its exceptional preservation and abundance of vertebrate fossils, including a rich assemblage of whales and dolphins (Cetacea). Here, we integrate taphonomic data on 890 marine vertebrate fossils, gathered through 16 different localities. Our observations range from the taxonomic distribution, articulation, completeness, disposition and orientation of skeletons, to the presence of bite marks, associations with shark teeth and macroinvertebrates, bone and soft tissue preservation, and the formation of attendant carbonate concretions and sedimentary structures. We propose that the exceptional preservation characterising many Pisco vertebrates, as well as their exceptionally high abundance, cannot be ascribed to a single cause like high sedimentation rates (as proposed in the past), but rather to the interplay of several favourable factors including: (i) low levels of dissolved oxygen at the seafloor (with the intervention of seasonal anoxic events); (ii) the early onset of mineralisation processes like apatite dissolution/recrystallisation and carbonate mineral precipitation; (iii) rapid burial of carcasses in a soupy substrate and/or a novel mechanism involving scour induced self-burial; and (iv) original biological richness. Collectively, our observations provide a comprehensive overview of the taphonomic processes that shaped one of South America’s most important fossil deposits, and suggest a model for the formation of other marine vertebrate Fossil-Lagerstätten.
... Dunbar et al., 1990), which are widely known for their exceptionally preserved fossil assemblages (e.g. DeVries, 2016DeVries, , 2019Esperante et al., 2015;Bianucci et al., 2016aBianucci et al., , b, c, 2018aGariboldi et al., 2015;Gioncada et al., 2016Gioncada et al., , 2018aStucchi et al., 2016;Landini et al., 2017aLandini et al., , b, 2019Marx et al., 2017a, b;Lambert et al., 2018Lambert et al., , 2020Lambert et al., , 2021Bosio et al., 2021a, b;Collareta et al., 2021b;Sanfilippo et al., 2021;Kočí et al., 2021). ...
Full-text available
The Cenozoic succession of the East Pisco Basin preserves the sedimentary record of several episodes of deformation of the forearc crust along the Peruvian margin. The 1:50,000 scale geological map presented here encompasses an area of about 1,000 km2 lying astride the Ica River, and contributes to our understanding of the timing and mode of basin filling and deformation. Our novel two-fold megasequence framework provides a sound basis for establishing a first-order tectono-stratigraphic setting of the mid-Eocene–upper Miocene succession exposed in the study area. We interpret that the mid-Eocene to lower Oligocene succession studied in this work (megasequence P) was deposited in a single forearc basin, which was dissected into the present-day West and East Pisco basins by a fault-bounded basement high during the late Oligocene, and subsequently overlain by the Miocene fill of the East Pisco basin (megasequence N).
... One of the most privileged locations for unraveling the evolutionary history of cetaceans is undoubtedly the East Pisco Basin of southern Peru. Here, fossil marine vertebrates (mammals, birds, reptiles, and bony and cartilaginous fishes) occur within a semi-continuous, Eocene to Pliocene stratigraphic succession (e.g., Muizon & DeVries, 1985;Brand et al., 2004;Esperante et al., 2008Esperante et al., , 2015Lambert et al., 2010bLambert et al., , 2015aParham & Pyenson, 2010;Collareta et al., 2015Collareta et al., , 2017aCollareta et al., , 2020bCollareta et al., , 2021bBianucci et al., 2016b, c;Gioncada et al., 2016;Di Celma et al., 2017;Landini et al., 2017Landini et al., , 2019Bosio et al., 2021;Boskovic et al., 2021). In the course of the last forty years, palaeontological investigations on the fossil record of the Pisco Basin have led to describing a plethora of new species of archaeocete, odontocete and mysticete taxa, as well as to identifying crucial fossils that illustrate the skeletal anatomy, morphofunctional adaptations and palaoecological habits of cetaceans through most of the Cenozoic. ...
Full-text available
The East Pisco Basin is one of the forearc basins that formed during the Cenozoic along the coast of Peru due to the subduction of the Farrallon-Nazca plate beneath the South American plate. The sedimentary fi ll of this basin is extensively exposed along the coastal Ica Desert, and includes a succession of Eocene to Pliocene marine sediments that account for a ~50-myr-long history of semi-continuous deposition. These rocks are characterized by an outstanding fossil content that remarkably contributed to our understanding of the evolutionary history of the main groups of Cenozoic marine vertebrates. In the Ica desert, the most common and signifi cant vertebrate remains belong to cetaceans. Knowledge on the fossil cetaceans of the East Pisco Basin has grown dramatically in the last fi fteen years thanks to several international research projects involving, among many others, the authors of the present article. These research eff orts have led to the discovery of several hundred fossil skeletons, the most signifi cant of which have been collected, prepared and partly published. Furthermore, interdisciplinary studies were also conducted in order to provide a high resolution chronostratigraphic framework for this fossil record. Remarkable cetacean specimens (42.6 Ma) Yumaque strata are home to the quadrupedal protocetid archaeocete Peregocetus pacifi cus, which documents the fi rst arrival of cetaceans in the Pacifi c Ocean. Geologically younger (36.4 Ma) Yumaque deposits have yielded the holotype skeleton of Mystacodon selenesis, the oldest mysticete ever found. This ancestor of the modern baleen whales had a skull provided with a complete dentition and retained hindlimbs, albeit reduced in size. In the Otuma Formation, a nine-m-long basilosaurid (Cynthiacetus peruvianus) has been discovered. The Chilcatay Formation records the fi rst great radiation of the odontocetes, represented by Inticetidae (Inticetus vertizi), basal Platanidelphidi (Ensidelphis riveroi), Squalodelphinidae (Furcacetus fl exirostrum, Huaridelphis raimondii, Macrosqualodelphis ukupachai and Notocetus vanbenedeni), Platanistidae (aff. Araeodelphis), Physeteroidea (Rhaphicetus valenciae and cf. Diaphorocetus), Chilcacetus cavirhinus, indeterminate Eurinodelphinidae, and Kentriodontidae (Kentriodon). Overall, this roughly coeval assemblage displays a considerable disparity in terms of skull shape and body size that is possibly related to the development of diff erent trophic strategies, ranging e.g., from suction to raptorial feeding. In the Pisco Formation, starting from P0, the baleen-bearing whales (Chaeomysticeti) represent the most frequent cetacean fossils (only a few mysticetes are known from the Chilcatay strata). Two chaeomysticete lineages are found in the Pisco Formation: Cetotheriidae (from Tiucetus rosae in P0 to Piscobalaena nana in P2) and Balaenopteroidea (from Pelocetus in P0 to several undescribed species of Balaenopteridae in P2, testifying to a progressive trend toward gigantism). Odontocetes are rare in P0, the "kentriodontid" Incacetus broggii being the only species described from these strata, but they become more abundant and diverse in P1 and P2. In P1, the commonest toothed whale is Messapicetus gregarius, a member of Ziphiidae featuring an extremely elongated rostrum and a complete set of functional teeth. Another ziphiid from P1 is Chimuziphius coloradensis, known only from the fragmentary holotype cranium. The P1 strata also record the appearance of the crown Delphinida, with the superfamily Inioidea being represented by two small pontoporiids (Brachydelphis mazeasi and Samaydelphis chacaltanae) and one iniid (Brujadelphis ankylorostris). Moreover, P1 is also home to the stem physeteroid Livyitan melvillei; featuring a three-m-long skull and teeth reaching 36 cm in length, L. melvillei was one of the largest raptorial predators and, possibly, the biggest tetrapod bite ever found. Acrophyseter is another macroraptorial sperm whale, distinctly smaller than L. melvillei, known from both P1 and P2. Even smaller in size are the kogiids Platyscaphokogia landinii and Scaphokogia cochlearis, both of which are known from the upper strata of P2. The same allomember is also home to the ziphiids Chavinziphius maxillocristatus and Nazcacetus urbinai, the "kentriodontids" Atocetus iquensis and Belenodelphis peruanus, and undescribed members of Phocoenidae.
... Large-scale works on cetacean assemblages from Peru have revealed different patterns even with similar taxonomic compositions of the mysticete fauna. Bianucci et al. (2016) showed that the large cetacean assemblage of Cerro Los Quesos (late Miocene, Pisco Formation, Peru) mainly comprises mysticetes with a higher proportion of balaenopteroids. At Cerro Los Quesos, however, partially articulated skeletons are observed in situ with occurrence of hard nodules enveloping the bones that suggest high microbial activity before burial. ...
The Tertiary Piedmont Basin (TPB) is located in northwestern Italy and represents the western portion of a long and wide basin occupying the area that is now known as the Po Plain. Largely continuous sedimentation occurred in this basin from the early Miocene to the Pleistocene; two Pliocene marine formations are well known from this basin: Argille Azzurre and Sabbie d'Asti formations. Both these formations are rich in marine fossils including numerous cetacean specimens. We analysed the Pliocene mysticete partition of the TPB cetacean record including 55 baleen whale specimens from two museum collections to interpret the taphonomic factors influencing the preservation potential of the basin. Careful observations of bones were performed to find evidence of causes of death, floating and transport, interactions with sharks, timings of burial and whale fall activity. Analysis of preservation of specific bones (vertebrae, mandible, forelimb) was performed in order to discriminate between different mechanisms of transport in the water column or on the seafloor. We found that biostratinomic agents were active all along the basin in both the formations; these included scavenging, bottom currents and the activities of bacteria and whale fall communities. Intense shark-cetacean interactions are recorded by shark bite traces on mysticete bones. Patterns of preservation of vertebrae and loss of paired appendages are used as evidence of floating and transport on the seafloor. A mix of early and late burials is inferred on a specimen basis allowing for the characterisation of the complete biostratinomic history of each mysticete specimen. We suggest that many factors are responsible for good preservation in the TPB mysticete record; these include relative timing of burial and intensity of biostratinomic processes active prior to burial.
... Therefore, in light of the nomenclatural approach suggested by the NACSN (2005), the aforementioned unconformity-bounded "formations" might be better regarded as alloformations . Overall, the deposits cropping out in the East Pisco Basin are renowned to paleontologists worldwide for hosting well-diversified and exquisitely preserved assemblages of marine fossils that include both vertebrates (e.g., Lambert et al., 2010Lambert et al., , 2017Lambert et al., , 2020Collareta et al., 2015Collareta et al., , 2017Collareta et al., , 2020Collareta et al., , 2021Bianucci et al., 2016aBianucci et al., , b, c, 2018Landini et al., 2017Landini et al., , 2019Marx et al., 2017;Gioncada et al., 2016, b) and macro-invertebrates (DeVries and Frassinetti 2003Di Celma et al., 2017Coletti et al., 2018Coletti et al., , 2019Collareta et al., 2019;Bosio et al., 2020aBosio et al., , 2021Kočí et al., 2020). ...
Exquisitely preserved fossils of a new reef-building vermetid species from shallow-marine lower Miocene (Burdigalian) deposits of the Chilcatay Formation and upper Miocene (Tortonian) sediments of the Pisco Formation of Peru are here reported and described in detail for the first time. These finds are assigned to the living genus Thylacodes and recognized as representatives of a new species, Thylacodes devriesi sp. nov. This new taxon is known by long, almost straight tube-like shells that display peculiar ornamentations in form of striated lamellae and are arranged in an organ-pipe fashion. This discovery represents an important addition to the knowledge of the systematics and distribution of Thylacodes in South America in the geological past. Paleoenvironmental and taphonomic inferences drawn by the fossil remains of this reef-forming species are herein discussed for both the Chilcatay and Pisco formations in the broader framework of the South American fossil record of Vermetidae.
The Eocene sediment successions of the East Pisco Basin (southern Peru) host an exceptionally rich and well-preserved assemblage of vertebrate fossils. However, due to the dearth of geochronological and biostratigraphic controls as well as of stratigraphic correlations, our understanding of these rocks and their fossil content remains elusive. This paper provides a comprehensive calcareous nannofossil, diatom, and silicoflagellate biostratigraphic framework for the Eocene strata exposed at four localities along the Ica River Valley, permitting a robust chronological calibration of the marine vertebrate fauna entombed therein and a better definition of important appearance/ extinction events. The Paracas Formation, deposited directly on top of the Proterozoic and Paleozoic rocks of the crystalline basement, is formed by a siliciclastic-bioclastic gravel-sized deposit (Los Choros member) and calcareous-terrigenous siltstone (Yumaque member) that was deposited from the Lutetian (47.8–41.2 Ma) through the Bartonian (41.2–37.7 Ma) to the early Priabonian (37.7–33.9 Ma). The unconformably overlying Otuma Formation consists of a basal sand, followed by calcareous siltstone intercalated by diatomite layers towards the top. In the study area, the Otuma Formation is Priabonian in age and is truncated at the top by an unconformity at the base of the overlying Miocene Chilcatay Formation. Due to the angular nature of the unconformity, the upper Otuma strata reach the Oligocene elsewhere. Average sedimentation rates range from 17 to 24 m/My in the Yumaque member of the Paracas Formation and increase to 147–170 m/My in the Otuma Formation. The microfossil assemblages witness a coastal setting with warm-temperate conditions for the Paracas Formation that become slightly cooler (though still temperate) in the upper Otuma Formation. Diatomaceous layers in the upper Otuma Formation indicate an overall increase in nutrient availability, which could reflect the global reorganization of ocean currents at the Eocene-Oligocene transition. However, the taxonomic composition of the diatom assemblage suggests seasonal rather than persistent upwelling conditions.
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The highly productive waters of the Humboldt Current System (HCS) host a particular temperate ecosystem within the tropics, whose history is still largely unknown. The Pisco Formation, deposited during Mio-Pliocene times in the Peruvian continental margin has yielded an outstanding collection of coastal-marine fossils, providing an opportunity to understand the genesis of the HCS ecosystem. We present a comprehensive review, completed with new results, that integrates geological and paleontological data from the last 10 My, especially focusing on the southern East Pisco Basin (Sacaco area). We discuss the depositional settings of the Pisco Formation and integrate new U/Pb radiometric ages into the chronostratigraphic framework of the Sacaco sub-basin. The last preserved Pisco sediments at Sacaco were deposited ~ 4.5 Ma, while the overlying Caracoles Formation accumulated from ~ 2.7 Ma onwards. We identified a Pliocene angular unconformity encompassing 1.7 My between these formations, associated with a regional phase of uplift. Local and regional paleoenvironmental indicators suggest that shallow settings influenced by the offshore upwelling of ventilated and warm waters prevailed until the early Pliocene. We present an extensive synthesis of the late Miocene–Pleistocene vertebrate fossil record, which allows for an ecological characterization of the coastal-marine communities, an assessment of biodiversity trends, and changes in coastal-marine lineages in relation to modern HCS faunas. Our synthesis shows that: (i) typical endemic coastal Pisco vertebrates persisted up to ~ 4.5 Ma, (ii) first modern HCS toothed cetaceans appear at ~ 7–6 Ma, coinciding with a decline in genus diversity, and (iii) a vertebrate community closer to the current HCS was only reached after 2.7 Ma. The genesis of the Peruvian coastal ecosystem seems to be driven by a combination of stepwise transformations of the coastal geomorphology related to local tectonic pulses and by a global cooling trend leading to the modern oceanic circulation system.
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Invertebrate taphonomy can provide significant information about the post-mortem processes that affected the fossil record. In the East Pisco Basin of southern Peru, a Panopea Ménard de la Groye, 1807 shell bed was found in the upper Miocene strata of the Pisco Formation, hinting at a peculiar biostratinomic and diagenetic history. This bed contains abundant invertebrate fossil molds cemented by dolomite. The specimens of the deep infaunal bivalve, Panopea sp., occur together with bivalves representative of shallow infaunal species (Trachycardium sp. and Dosinia ponderosa [Gray, 1838]) and balanid barnacles, which are sessile encrusters. The Panopea specimens host compound molds evidencing an abundant encrusting fauna, including serpulids, ?foraminifera, bryozoans, and barnacles that colonized the inner surfaces of the valves before their final burial. We hypothesize that short-term, storm-related processes exhumed the living bivalves, resulting in a sedimentological concentration of relatively well-preserved shells. After the death of the exhumed bivalves, the inner surfaces of the articulated Panopea shells, representing hard-substratal, sheltered environments on an otherwise unstable sandy seafloor (i.e., “benthic islands”), were colonized by different encrusting organisms. Following the final burial, dolomite precipitated, cementing the sediment infill of the valves. Lastly, a decrease of pH occurred at the sulfate reduction-methanogenesis boundary, inducing the dissolution of the shell carbonate.
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Lomacetus ginsburgi is the first known fossil Phocoeninae and represents the sister group of the living Phocoeninae.-English summary
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Free download: The enormous concentration of marine vertebrates documented within the Pisco Formation is unique for Peru and South America and places this unit among the prime fossil Lagerstätten for Miocene to Pliocene marine mammals worldwide. In order to provide a robust stratigraphic framework for the fossil-bearing locality of Cerro Los Quesos, this study presents a 1:10,000 scale geological map covering an area of about 21 km2, a detailed measured section spanning 290 m of strata, and a refined chronostratigraphy for the studied succession well constrained by diatom biostratigraphy and high-resolution 40Ar/39Ar isotopic dating of three interbedded ash layers. Within the apparently monotonous, diatomite-dominated sedimentary section, the Pisco Formation has been subdivided into six local members, with stratigraphic control over the different outcrops facilitated by the establishment of a detailed marker bed stratigraphy based on 15 readily distinguishable sediment layers of different nature.
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This outcrop-based study reports diffuse joints and veins, normal to strike-slip fault zones and minor folds that developed, from Miocene to Quaternary, within the clastic to siliceous sedimentary record of the forearc Pisco Basin of southern Peru. Patterns, orientations, dimensional parameters and other outcrop-scale characteristics of the various deformation features are illustrated and their genetic mechanisms and timing of development are inferred. These new structural data and interpretations allow a better constraint of the structural style and evolution of the Pisco Basin, and can represent useful guidelines for characterizing the outcrop-scale deformation affecting similar forearc basins along the Peruvian coast.Major results of this study are that the development of the documented deformation features, their patterns, dimensional parameters and kinematics seem influenced by local perturbations of the paleostress field by mechanic processes partly independent of plate tectonics forces. These processes include strain localization on both pre-existing and progressively forming new structural discontinuities, and cyclic switches of the horizontal, principal stress axes σ2 and σ3. In particular, we discuss how different normal fault patterns, from sub-parallel to multidirectional/polygonal, could form in a same deformation phase in response of the local σ2/σ3 magnitude ratio, as an evolution of stratabound, mutually orthogonal vein sets.
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Instead of teeth, modern mysticetes bear hairfringed keratinous baleen plates that permit various bulkfiltering predation techniques (from subsurface skimming to lateral benthic suction and engulfment) devoted to various target prey (from small invertebrates to schooling fish). Current knowledge about the feeding ecology of extant cetaceans is revealed by stomach content analyses and observations of behavior. Unfortunately, no fossil stomach contents of ancient mysticetes have been described so far; the investigation of the diet of fossil baleen whales, including the Neogene family Cetotheriidae, remains thus largely speculative. We report on an aggregate of fossil fish remains found within a mysticete skeleton belonging to an undescribed late Miocene (Tortonian) cetotheriid from the Pisco Formation (Peru). Micro-computed tomography allowed us to interpret it as the fossilized content of the forestomach of the host whale and to identify the prey as belonging to the extant clupeiform genus Sardinops. Our discovery represents the first direct evidence of piscivory in an ancient edentulous mysticete. Since among modern mysticetes only Balaenopteridae are known to ordinarily consume fish, this fossil record may indicate that part of the cetotheriids experimented some degree of balaenopteridlike engulfment feeding. Moreover, this report corresponds to one of the geologically oldest records of Sardinops worldwide, occurring near the Tortonian peak of oceanic primary productivity and cooling phase. Therefore, our discovery evokes a link between the rise of Cetotheriidae; the setup of modern coastal upwelling systems; and the radiation of epipelagic, small-sized, schooling clupeiform fish in such highly productive environments.
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Although modern beaked whales (Ziphiidae) are known to be highly specialized toothed whales that predominantly feed at great depths upon benthic and benthopelagic prey, only limited palaeontological data document this major ecological shift. We report on a ziphiid-fish assemblage from the Late Miocene of Peru that we interpret as the first direct evidence of a predator-prey relationship between a ziphiid and epipelagic fish. Preserved in a dolomite concretion, a skeleton of the stem ziphiid Messapicetus gregarius was discovered together with numerous skeletons of a clupeiform fish closely related to the epipelagic extant Pacific sardine (Sardinops sagax). Based on the position of fish individuals along the head and chest regions of the ziphiid, the lack of digestion marks on fish remains and the homogeneous size of individuals, we propose that this assemblage results from the death of the whale (possibly via toxin poisoning) shortly after the capture of prey from a single school. Together with morphological data and the frequent discovery of fossil crown ziphiids in deep-sea deposits, this exceptional record supports the hypothesis that only more derived ziphiids were regular deep divers and that the extinction of epipelagic forms may coincide with the radiation of true dolphins.
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free download: This paper describes a ∼200 m-thick section of the Pisco Formation exposed at Cerro Colorado, an important fossiliferous site in the Ica desert. In order to properly place the fauna in its correct relative position, this study establishes the stratigraphic framework within which the different fossil-bearing intervals of this site can be compared and may prove invaluable in future high-resolution studies on the faunal change. Most of the Pisco Formation deposits exposed at Cerro Colorado consist of gently dipping fine-grained sandstones, diatomaceous siltstones and diatomites with minor ash layers and dolomites deposited within nearshore and offshore settings. To facilitate detailed stratigraphic correlations within the Pisco strata for a 30 km2 area, eight marker beds have been defined and large-scale (1:10,000 scale) geological mapping conducted to determine fault positions, styles and offsets. The geological map shows that there are two important angular unconformities in the study area. The first one is the interformational basal unconformity of the Pisco Formation against folded, faulted, and planated Oligo-Miocene rocks of the Chilcatay Formation. The second is a low-angle intraformational erosional discontinuity of up to 4° angular discordance that allows the subdivision of the Pisco stratigraphy exposed in the study area into two informal allomembers. Dating of the exposed succession by diatom biostratigraphy suggests that the age of the lower allomember is late Miocene, whereas the upper allomember is late Miocene or younger.
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Hundreds of fossil marine vertebrates cropping out at Cerro Colorado (Pisco Basin, Peru) are identified and reported on a 1:6500 scale geological map and in a joined stratigraphic section. All the fossils are from the lower strata of the Pisco Formation, dated in this area to the late middle or early late Miocene. They are particularly concentrated (88%) in the stratigraphic interval from 40 to 75 m above the unconformity with the underlying Chilcatay Formation. The impressive fossil assemblage includes more than 300 specimens preserved as bone elements belonging mostly to cetaceans (81%), represented by mysticetes (cetotheriids and balaenopteroids) and odontocetes (kentriodontid-like delphinidans, pontoporiids, ziphiids, and physeteroids, including the giant raptorial sperm whale Livyatan melvillei). Seals, crocodiles, sea turtles, seabirds, bony fish, and sharks are also reported. Isolated large teeth of Carcharocles and Cosmopolitodus are common throughout the investigated stratigraphical interval, whereas other shark teeth, mostly of carcharinids, are concentrated in one sandy interval. This work represents a first detailed census of the extraordinary paleontological heritage of the Pisco Basin and the basis for future taphonomic, paleoecological, and systematic studies, as well as a much needed conservation effort for this extremely rich paleontological site.
The morphology and shallow structure of the Peru continental margin has been mapped using bathymetric and seismic reflection profiles f r om lat 6° S to 16° S. Other geophysical and geologic data are used to constrain interpretations of the margin's deeper structure and to relate the offshore to the onshore Andean geology. Two prominent structural ridges, subparallel to onshore Andean trends, control the distribution of the offshore Cenozoic sedimentary basins. The Coastal Cordillera, which surfaces north of lat 6° Sand south of lat 14°S, can be traced onto the offshore as an Outer Shelf High (OSH); it is evidently cored with Precambrian and Paleozoic metasediments and crystalline rocks. A series of shelf basins is situated between the Coast Range/ OSH and the Andean Cordillera: f r om north to south, these are the Sechura, Salaverry, and East Pisco Basins. A second set of upper-slope basins flanks the Coast Range/OSH to the southwest, limited seaward by an Upper-Slope Ridge (USR) of deformed sediment: from north to south, these are the Trujillo, Lima, and West Pisco Basins. The Yaquina Basin lies within divergent arms of the USR. The shelf and upper-slope basins are set on continental massif. An anastomosing network of elongate ridges and ponded sediments is the surficial expression of the subduction complex, which apparently begins just seaward of the USR. The effect of the late Paleocene/Eocene Andean orogeny has been extrapolated offshore as a distinct interface of seismic velocity in the Salaverry Basin. Though Cenozoic marine sedimentation in the shelf basins did not begin until after this event, sedimentation in the upper-slope Trujillo Basin may have been more continuous through the early Tertiary. In the Trujillo Basin, the bulk of the nearly 4 km thick sedimentary section is of Paleogene age, while in the adjoining upper-slope Lima Basin to the southeast, the bulk of the nearly 2 km thick sedimentary section is of late Miocene or younger age. Apparently, post-Oligocene tectonism caused uplift, deformation, and a gross reduction of sedimentation in the Trujillo Basin; this event is evidenced by boundaries of differential structural deformation in seismic reflection profiles. In middle to late Miocene time, while orogenic activity affected the inland Andean Cordillera, the upper-slope Lima Basin subsided and began its depositional record. Unconformites in shelf basins apparently reflect the inland tectonism at this time. The boundary between the Lima and Trujillo Basins, and between the contrasting styles of upperslope tectonic movement, is near lat 9.5° S, coincident with the present day intersection of the Mendana Fracture Zone with the continental margin. A final phase of upper-slope deformation closed the Pliocene. Like earlier tectonic activity, the major break in structural style of this epoch occurs near lat 9.5° S: compressional faulting and folding characterize the younger sediments of the Trujillo Basin, while the Lima Basin appears as a broad, open syncline, distrubed only in its southernmost occurrence.