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Description of the Neochoerus specimens from the Late Pleistocene (Rancholabrean) of Chiapas, and comments on the taxonomic identity of the fossil capybaras from other Mexican localities

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The capybara Neochoerus aesopi is an extinct giant rodent that inhabited North, Central, and South America during the Rancholabrean/Lujanian (late Pleistocene). In Mexico, only N. aesopi has been reported from Tlapacoya, Mexico State; Chapala lake, Jalisco; and La Cinta-Portalitos, on the border of Michoacán and Guanajuato. Here, we describe N. aesopi remains from the late Pleistocene at Los Mangos locality, Villaflores municipality, Chiapas, Mexico. In addition, the capybara material from Jalisco and Puebla, referred as Hydrochoerus sp. and Neochoerus sp., respectively, is reexamined. The mandibular and dental morphological characteristics and measurements of the specimens examined from Jalisco and Puebla allow this material to be referred as N. aesopi. The definitive identification of this species broadens its spacial range in North America.
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Neochoerus in the late Pleistocene of Chiapas
Boletín de la Sociedad Geológica Mexicana
/ 72 (1) / 2020 /
To cite this article:
Carbot-Chanona, G., Eng-Ponce, J., Gómez-
Pérez, L.E. (2020), Description of the
Neochoerus specimens from the late Pleistocene
(Rancholabrean) of Chiapas, and comments
on the taxonomic identity of the fossil
capybaras from other Mexican localities.
Boletín de la Sociedad Geológica Mexicana,
72 (1), A021019.
Peer Review under the responsability of
Universidad Nacional Autónoma de México.
This is an open access article under the CC BY-NC-SA
El capibara Neochoerus aesopi es un roedor
gigante extinto que habitó Norte, Centro y
Sudamérica durante el Rancholabreano/
Lujaniano (Pleistoceno tardío). En
México, sólo N. aesopi ha sido reportado
para Tlapacoya, Estado de México; el lago
de Chapala, Jalisco y La Cinta-Portalitos,
en los límites de Michoacán-Guanajuato.
Aquí describimos los restos de N. aesopi
encontrados en los sedimentos del Pleisto-
ceno tardío que afloran en la localidad Los
Mangos, en el Municipio de Villaflores,
Chiapas, México. También, reexamina-
mos el material de capibaras de Jalisco
y Puebla (referido como Hydrochoerus sp.
y Neochoerus sp., respectivamente). Las
características morfológicas mandibulares
y dentales, así como las medidas de los
especímenes examinados de Jalisco y
Puebla permiten referirlos también como
N. aesopi. La identificación definitiva de
esta especie amplía su rango geográfico en
América del Norte.
Palabras clave: Capibara, Neo-
choerus, Hydrochoerus, tax-
onomía, Pleistoceno, México.
The capybara Neochoerus aesopi is an
extinct giant rodent that inhabited
North, Central, and South America
during the Rancholabrean/Lujanian
(late Pleistocene). In Mexico, only N.
aesopi has been reported from Tlapa-
coya, Mexico State; Chapala lake,
Jalisco; and La Cinta-Portalitos, on
the border of Michoacán and Gua-
najuato. Here, we describe N. aesopi
remains from the late Pleistocene
at Los Mangos locality, Villaflores
municipality, Chiapas, Mexico. In
addition, the capybara material
from Jalisco and Puebla, referred as
Hydrochoerus sp. and Neochoerus sp.,
respectively, is reexamined. The man-
dibular and dental morphological
characteristics and measurements of
the specimens examined from Jalisco
and Puebla allow this material to be
referred as N. aesopi. The definitive
identification of this species broadens
its spacial range in North America.
Keywords: Capybara, Neochoe-
rus, Hydrochoerus, taxonomy,
Pleistocene, Mexico.
Manuscript received: March 10, 2019.
Corrected manuscript received: April 10, 2019.
Manuscript accepted: April 18, 2019.
1 Museo de Paleontología “Eliseo Palacios Agu-
ilera”, Dirección de Paleontología, Secretaría
de Medio Ambiente e Historia Natural. Calza-
da de Los Hombres Ilustres s/n, 29000, Tuxtla
Gutiérrez, Chiapas, Mexico.
2 Laboratorio de Paleontología, Facultad de
Biología, Universidad Michoacana de San
Nicolás de Hidalgo. Av. Francisco J. Múgica
s/n, Ciudad Universitaria, 58030, Morelia,
Michoacán, Mexico.
* Corresponding author: (Carbot-Chanona)
Gerardo Carbot-Chanona1,*, Joaquín Eng-Ponce2, Luis Enrique Gómez-Pérez1
Description of the Neochoerus specimens from the late Pleistocene (Rancholabrean) of
Chiapas, and comments on the taxonomic identity of the fossil capybaras from other
Mexican localities
Descripción de especimenes de Neochoerus del Pleistoceno (Rancholabreano) tardío de Chiapas, y
comentarios sobre la taxonomía de los capibaras fósiles de otras localidades mexicanas
Neochoerus in the late Pleistocene of Chiapas
Boletín de la Sociedad Geológica Mexicana
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2 Artícle A021019
1. Introduction
The capybaras (Rodentia: Caviidae: Hydrocho-
erinae) are large rodents that lived in North and
South America from the Miocene to the recent.
Only two genera are known from the late Pleis-
tocene, Hydrochoerus and Neochoerus (Kurtén and
Anderson, 1980). Hydrochoerus is represented by
two living species: H. hydrochaeris and H. isthmius.
Today, Hydrochoerus hydrochaeris inhabits Venezuela,
Brazil, Paraguay, Uruguay, and eastern Colombia.
It also inhabits the Amazon basin of Ecuador,
Peru, and Bolivia, as well as northeastern to south-
ern Argentina (Mones and Ojasti, 1986). The
species has a late Pleistocene fossil record from
Curaçao, Uruguay, Brazil, and Argentina (Mones,
1991; Kerber and Ribeiro, 2011) and Hydrochoe-
rus isthmius inhabits Panama, western Colombia,
and western Venezuela (Woods and Kilpatrick,
2005) and does not have a fossil record. Only
two species of Hydrochoerus are represented in the
fossil record: H. ballesterensis from late Pliocene to
early Pleistocene of the Villa Ballester, Argentina
(Mones, 1991), and H. gaylordi from late Pliocene
to early Pleistocene of Grenadines Bank, island
of Grenada, Lesser Antilles island-arc (MacPhee
et al., 2000).
Neochoerus is an extinct genus closely related to
Hydrochoerus (Vucetich et al., 2014), with a fossil
record throughout the late Pliocene to the late
Pleistocene of North and South America (Mones,
1991). Neochoerus was erected by Hay (1926) for the
species Hydrochoerus pinckneyi, which he described
based on a single M3 (third upper molar) from the
Pleistocene of South Carolina (Hay, 1923).
Currently, six species are recognized: (i) Neo-
choerus occidentalis from Blancan-Irvingtonian (late
Pliocene–early Pleistocene) of Sonora and Jalisco
(Carranza-Castañeda, 2016); (ii) N. cordobai from
Blancan III (early Pliocene) of Guanajuato (Car-
ranza-Castañeda, 2016), referred as Phugatherium
dichroplax by Vucetich et al. (2015); (iii) N. tarijensis
from Ensenadian (middle Pleistocene) of Tarija,
Bolivia; (iv) N. fontanai from late Pliocene to early
Pleistocene of Villa Ballester, Buenos Aires,
Argentina (although Mones [1991] considered it
a nomen dubium); (v) N. sulcidens from the Lujanian
(late Pleistocene) of Brazil and Uruguay; and (vi)
N. aesopi from the Rancholabrean/Lujanian (late
Pleistocene) of North, Central, and South Amer-
ica (Mones, 1991; Lucas et al., 2008). Occasionally,
N. pinckneyi from South Carolina, USA (Hay, 1923,
1926) has been considered valid by some authors
(e. g., Álvarez, 1969; Kurtén and Anderson, 1980;
Rufolo, 1998; Carranza-Castañeda, 2016), but it
was considered a synonymy of N. aesopi by Mones
(1991), because both taxa came from the same
The only North American Rancholabrean spe-
cies, N. aesopi, has been described in Mexico from
Tlapacoya, Mexico State (referred to as N. pinckneyi;
Álvarez, 1969); La Cinta-Portalitos locality, on the
border of Michoacán and Guanajuato; and Cha-
pala lake, Jalisco (Lucas, 2008; Eng-Ponce, 2018).
Other records of the genus include N. cordobai
from the Blancan to Irvingtonian of Guanajuato
(Carranza-Castañeda and Miller, 1988), and N.
occidentalis from Irvingtonian of Jalisco and Sonora
(Carranza-Castañeda et al., 1981; Shaw, 1981;
Shaw and McDonald, 1987; Carranza-Castañeda,
2016). In addition, specimens referred to Hydro-
choerus from the late Pleistocene of Media Luna
lagoon, San Luis Potosí; Térapa, Sonora; Chapala
lake, Jalisco; and Valsequillo, Puebla (Hernán-
dez-Junquera, 1977; Pichardo, 1997; Mead et al.,
2006; Carranza-Castañeda, 2016), and indetermi-
nate hydrochoerids from Los Tanques, Zacatecas
(Lozano-Ramos et al., 2006) have been reported.
The fossil record of capybaras in Mexico is poorly
known. Therefore, the aim of this work is to for-
mally describe the capybaras specimens recovered
from Chiapas state, adding the rst locality with
these rodents in south-southeastern Mexico. We
also comment on the taxonomic identity of the
late Pleistocene capybara specimens from other
localities in Mexico.
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Figure 1 Location (A), and stratigraphic section (B) of the Los Mangos, Villaflores, Chiapas, Mexico.
2. Study area
The material described in this work was collected
from the Los Mangos locality, near downtown Vil-
laores, at 16°14ʹ25ʺN and 93°13ʹ28ʺW (Figure
1A). A sequence of 4 m thick lacustrine sediments
crops out there (Figure 1B). The base of the sec-
tion is composed of 1 m of coarse to ne sand with
granular gravel. Over the base section, there is a
0.50 m layer of light brown silty clay where Neo-
choerus aesopi material reported here was collected,
in association with Glyptotherium oridanum, Odocoil-
eus virginianus, Equus mexicanus, E. conversidens, and
Bison sp. remains (Gómez-Pérez and Carbot-Cha-
nona, 2012; Carbot-Chanona and Gómez-Pérez,
2014). Stratigraphically above this bed is a 1.50
m layer composed of alternating beds of brown
silt and reddish-brown ne sand. In this section, G.
oridanum remains have been collected. The next
layer is composed of sandy silt and ne sand, 1
m thick. The upper part of the sequence consists
of soil with organic matter. The presence of Bison
sp. is indicative of the Rancholabrean NALMA
(North American Land Mammal Ages biochro-
nology, late Pleistocene) for the bearing deposits
(Bell et al., 2004).
3. Materials and methods
Specimens used in this study include: IHNFG-
4865, a fragment of maxilla with complete right
M3; IHNFG-4866, an almost complete lower jaw,
with left and right p4-m3 tooth rows and both
Neochoerus in the late Pleistocene of Chiapas
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incisives preserved; IHNFG-4873, left hemi-man-
dible with an incisive, p4 and m1; IHNFG-5760,
occipital part of the skull; and IHNFG-5761, a
pelvic girdle. Specimens were recovered using
the traditional vertebrate paleontology methods,
and cleaned with needles, airscribe, and soft
bristle brushes to remove sediment. The broken
parts were joined with commercial glue insoluble
to water, and the ssures were lled with epoxy
clay. Specimens are housed at Paleontological
Collection of the Paleontological Museum “Eliseo
Palacios Aguilera”, Secretaría de Medio Ambiente
e Historia Natural, Chiapas, Mexico.
We use the nomenclature for upper and lower
dentition of capybaras (Figure 2) proposed by
Mones (1975a, 1991), adapted and used by other
authors (e. g. Kerber and Ribeiro, 2011; Vucetich
Figure 2 Nomenclature of the lower (A) and upper teeth (B), modified from Mones (1991), and some mandible measurements (C) taken
from Carranza-Castañeda (2016). Dental abbreviations: i, lower incisor; p4, fourth lower premolar; m1, first lower molar; m2, second
lower molar, m3: third lower molar; M3, third upper molar; h.1-5i., first-fifth internal fissure; h.1-3e., first-third external fissure; c.1-3e.,
first-third external column; c.1-3i., fist-third internal column; h.s.e., secondary external fissure; h.f.e., fundamental external fissure;
h.t.i., tertiary internal fissure; h.s.i., secondary internal fissure; h.s.i.a., anterior secondary internal fissure; h.s.i.p., principal secondary
internal fissure; h.p.i., primary internal fissure; HFI, fundamental internal fissure; H2-12I, second-twelveth internal fissure; HPE, principal
external fissure; Pr.I, first prism; Pr.II, second prism; Pr.V, fifth prism; Pr.XII, twelfth prism; Pr.XIII, thirteenth prism; Pr.s.a., secondary
anterior prism of p4; Pr.Ia-Pr.Ia’, anterior plate of first prism; Pr.Ib-Pr.Ib’, posterior plate of first prism; Pr.IIa-Pr.IIa’, anterior plate of
second prism; Pr.IIb-Pr.IIb’, posterior plate of second prism. Measurements abbreviation: L, length; W, width; DL, diastema length; TL,
toothrow length; IDA, internal distance between the alveoli of p4; DMF, distance of the masseteric fossa through the Pr.I of the m1.
Neochoerus in the late Pleistocene of Chiapas
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et al., 2015; Carranza-Castañeda, 2016). Upper
and lower dentition are identied by uppercase
and lowercase letters, respectively (e. g., M1, m1).
For the cranial, mandibular and postcranial ele-
ments the nomenclature was based on König and
Liebich (2007), Bode et al. (2013) and Brombini et
al. (2018). In the text, we employ the name Neo-
choerus cordobai because it is the rst name used in
the original description (see Carranza-Castañeda
and Miller, 1988). Carranza-Castañeda (2016)
used the name N. cordobae and did not explain the
reason for the change of the taxonomic name, and
there is no previous work where modications in
the nomenclature are discussed.
The measurements were obtained with a digital
caliper with 0.01 mm accuracy following Mones
(1991) and Carranza-Castañeda (2016), as shown
in Figure 2. The measurements of Neochoerus pinck-
neyi, N. aesopi (mean), N. sulcidens (mean), N. tarijensis
(mean), N. cordobai, N. occidentalis, and Hydrochoerus
hydrochaeris used for comparison were obtained
from the literature (Carranza-Castañeda and
Miller, 1988; Mones, 1991; Sanders, 2002; Kerber
and Ribeiro, 2011; Carranza-Castañeda, 2016).
The measurements of N. occidentalis from Sonora
were obtained from the gures presented in Car-
ranza-Castañeda (2016) using ImageJ software
(Rasband, 2012). The comparative bivariate plots
were elaborated in JMP version 8 (SAS, 2008),
using the measurements of Appendix 1 and 2
(Supplementary Material).
The photographs were taken with a digital
camera Canon XS, using a lightbox and indi-
rect lighting. Later, the images were processed in
Adobe Illustrator to erase the background. The
nal gures were made in CorelDraw X8.
AMNH, American Museum of Natural History,
Ney York, USA; AWC, Arizona Western College,
Arizona, USA; IHNFG, Instituto de Historia
Natural, Fósil Geográco, Chiapas, Mexico (his-
torically is the acronym for the Paleontological
Collection of the Secretaría de Medio Ambiente e
Historia Natural, Chiapas, Mexico); INAH, Insti-
tuto Nacional de Antropología e Historia, Ciudad
de Mexico, Mexico; MCN-D, Museu de Ciências
da Pontifícia Universidade Católica do Rio Grande
do Sul, Uruguaiana, Brazil; MCN-PV, Coleção de
Paleovertebrados do Museu de Ciências da Pon-
tifícia Universidade Católica do Rio Grande do
Sul, Uruguaiana, Brazil; MCPU, Museu de Ciên-
cias da Pontifícia Universidade Católica do Rio
Grande do Sul, Uruguaiana, Brazil; MCPU-PV,
Coleção de Paleovertebrados do Museu de Ciên-
cias da Pontifícia Universidade Católica do Rio
Grande do Sul, Uruguaiana, Brazil; MCPU-M,
Coleção de Mastozoologia do Museu de Ciên-
cias da Pontifícia Universidade Católica do Rio
Grande do Sul, Uruguaiana, Brazil; MLP, Museo
de La Plata, La Plata, Argentina; MPGJ, Museo
de Paleontología Geociencias, Querétaro, Mexico;
TMM, Jackson School of Geosciences, Vertebrate
Paleontology Laboratory, The University of Texas
at Austin, Texas, USA.
4. Results
Class MAMMALIA Linnaeus, 1758
Orden RODENTIA Bowdich, 1821
Infraorder Hystricognathi Tullberg, 1899
Family Caviidae Fischer, 1817 sensu Waterhouse,
Subfamily Hydrochoerinae (Gray, 1825) Gill, 1872
Genus Neochoerus Hay, 1926
Neochoerus aesopi (Leidy, 1853)
Holotype. Fragment of the incisive (position inde-
terminate), described as Oromys aesopi, collected by
Prof. Holmes on the Ashley River, Charleston,
South Carolina, USA (Leidy, 1853). Housed at the
AMNH under the catalog number FM 485.
Neochoerus in the late Pleistocene of Chiapas
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Figure 3 IHNFG-4866, nearly complete mandible from Los Mangos locality, Villaflores, Chiapas, in occlusal (A) and left lateral (B) view.
Detail of the left toothrow in occlusal view (C); the red circle indicates the unusual union between the Pr.IIa’ and Pr.IIb’. Abbreviations: apr,
angular process; conpr, condylar process; corpr, coronoid process; mcr, masseteric crest; mfo, masseteric fossa. Dental abbreviations
as in Figure 2.
Neochoerus in the late Pleistocene of Chiapas
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Synonymy. Oromys aesopi (Leidy, 1853); Hydrochoe-
rus aesopi (Leidy, 1856); Hydrochoerus magnus (Ger-
vais and Ameghino, 1880); Hydrochoerus robustus
(Leidy, 1887); Hydrochoerus holmesi (Simpson, 1928);
Neochoerus magnus (Kraglievich, 1930); Neochoerus
robustus (Kraglievich, 1930); Prohydrochoerus sirasakae
(Spillmann, 1941); Protohydrochoerus schirasakae [sic]
(Spillmann, 1948); Neochoerus (Neochoerus) sirasakae
(Hostteter, 1952); Neochoerus sirasakae (Mones,
1975b); Neochoerus pinckneyi (Mones, 1991).
IHNFG-4866 is a nearly complete mandible.
However, the right condylar and angular process
are missing (Figures 3A and 3B). Both tooth rows
are complete and included the p4-m3. The dias-
tema length (DL) is shorter (nearly 90 mm) than
the toothrow length (TL: 100.5 mm in the left too-
throw, 110 mm in the right toothrow). The inter-
nal distance between the alveoli of the p4 (IDA) in
its lingual portion is 34 mm. The masseteric crest
is robust and more retracted than in Hydrochoerus
hydrochaeris and begins below the Pr.I (rst prism)
of p4. The masseteric fossa in the two portions of
the mandible is located below the Pr.I of the m1
and the distance of the masseteric fossa (DMF)
through the Pr.I of the m1 is 97 mm.
Like in all rodents, the lower incisors lack
enamel in their lingual portion (Hillson, 2005).
They are robust and have an anteromedial canal
with longitudinal grooves in the labial portion.
The alveolus of the incisors extends below the
h.s.i. (secondary internal ssure) of the m1. Both
p4 show the Pr.s.a. (secondary anterior prism), Pr.I
and Pr.II are joined by a small enamel bridge. The
h.4i. (fourth internal ssure) is not present and
the h.2e. (second external ssure) extends to more
than 90% of the total width of the prism. The
junction of Pr.I and Pr.II is anked by h.1e. (rst
external ssure) in the labial portion and in the
lingual portion by the h.s.i.p. (principal secondary
internal ssure) leaving a narrow enamel bridge.
The Pr.s.a. has a Y shape like the Pr.I, while Pr.II
has a V shape. The length of the p4 is greater than
the length of the m2, this feature is characteristic
of N. aesopi (Mones, 1991).
The m1 presents the Pr.IIa joined to Pr.IIb in
the labial portion by a thin bridge of enamel; the
h.p.i. (primary internal ssure) is deep, exceeding
90% of the width of the prisms but does not sep-
arate them. The Pr.I and Pr.IIb are Y shape, while
the Pr.IIa are V shape. Both m2 possess complete
Pr.Ia and Pr.IIb. On the left molar the h.t.i. (ter-
tiary internal ssure) does not divide the Pr.IIa
into Pr.IIa’ (anterior plate of the second prism)
and Pr.IIb’ (posterior plate of the second prism)
and maintain the union of the enamel bridge in
the labial portion (Figure 3C). This feature has
been observed in juveniles and young adults of H.
hydrochaeris, but it is a rare feature in adults (Mones,
1975a) and cannot be seen in the right m2 because
that area is damaged. The right m3 has the Pr.I
divided into two plates; the Pr.IIb has an abnormal
widening making the h.s.e. shorter. The left m3
has a complete Pr.I; the h.s.i. exceeds 90% of the
total width and the h.s.e. is deep, exceeding 90%
of the width of the molar. The complete prisms
have a V shape.
IHNFG-4865 is a right maxillary fragment with
the M3 (Figure 4A). It is composed of 16 prisms
of which Pr.I is incomplete in its mesial portion
and Pr.XVI is represented only by a fragment of
enamel laminae. The length of the M3 is 59.12
mm and the width is 20.67 mm. The prisms in the
mesial portion are robust and tend to thin out at
their distal portion.
IHNFG-4873 corresponds to the anterior
portion of the left hemimandible of a juvenile
with incisor, p4, m1, and an associated unidenti-
ed upper molar fragment (Figures 4B and 4C).
The specimen preserves the distal portion of the
masseteric crest and the masseteric fossa is located
below the Pr.II of m1. It retains most of the inci-
sor, which presents the anteromedial groove and
poorly marked longitudinal striations. The p4
shows the Pr.s.a. and Pr.I in Y shape while Pr.II
has V shape. The Pr.s.a. is similar to the adult
Neochoerus in the late Pleistocene of Chiapas
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Figure 4 Dental, cranial and postcranial material of Neochoerus aesopi from Los Mangos locality, Villaflores, Chiapas. IHNFG-4865,
right M3 in occlusal view (A); IHNFG-4873, left hemimandible in lateral (B) and occlusal (C) views; IHNFG-5760, parietal (D); IHNFG-5761,
pelvic girdle (E and F). Bar scale in all cases equal to 50 mm. Abbreviations: ac, acetabulum; an, acetabular notch; co, condyle; fmg,
foramen magnum; mcr, masseteric crest; o, occipital bone; pcp, paracondylar process; stu, sacral tuberosity; tmrf, tuberosity for the m.
rectus femoris. Dental abbreviations as in Figure 2.
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specimen with the exception of the h.5i. (fth
internal ssure), which is deeper. The h.4i. is little
marked and, like the adult, the union between Pr.I
and Pr.II is very thin. Only the shape of the prisms
can be observed in the m1 and, unlike the adult
specimen, the Pr.I and Pr.IIa have a V shape and
Pr.IIb has a Y shape.
IHNFG-5760 is an occipital portion of the
skull (Figure 4D) and is similar to the occipital
of Hydrochoerus hydrochaeris. The occipital bone is
almost at, with a smooth depression in each side
of the foramen magnum. The condyles are thin
and border the lower part of the foramen mag-
num. The foramen magnum is oval in shape. The
paracondylar processes are small and are at the
level of the upper end of the occipital condyle.
IHNFG-5761 is a pelvic girdle partially con-
served and resembles the pelvis of the extant capy-
bara H. hydrochaeris. In ventral view, the hip bones
are elongated and narrow and with an Y shape.
The ilium is straight. The distal part of both ilium
is missing but it is notorious that the ilium wing
lay in a sagittal plane. The upper side of the body
of the right ilium preserves the proximal part of
the sacral tuberosity, which is thin in lateral-medial
direction. The body of the ilium bears a prominent
tuberosity for the m. rectus femoris. Only the iliopu-
bic eminence of the ilium is preserved. The pubis
is not preserved and is only observed as part of the
branch of the pubis. The acetabulum is deep and
circular in shape, with a smooth acetabular notch
located in the posterior margin (Figure 4E).
5. Discussion
The Neochoerus genus can be distinguished from the
close relative Hydrochoerus by the following: Neochoe-
rus is almost twice as large; the rostrum is longer;
the anterior portion of the zygomatic arc is more
rounded and oriented backward; the anterorbital
bar and lacrimal are more robust; the skull roof
is wider; the supraoccipital is wider and more
excavated; the masseteric crest is retracted; the
coronoid process is greatly reduced; and the M3
has 14 to 17 prisms, while Hydrochoerus has 12–13
prisms (Mones, 1991; Flynn, 2008). In the mandi-
ble IHNFG-4866, the masseteric crest is retracted
and the coronoid process is slightly elevated, while
in the M3 IHNFG-4865 16 prisms are observed.
In addition, the measurements of IHNFG-4865
and IHNFG-4866 fall within the observed range
of Neochoerus (Figures 5A and 5B). All these charac-
teristics allow us to assign the fossil material from
Chiapas to the genus Neochoerus.
The North American species in the genus
Neochoerus can be dierentiated by its size and
dental morphology. In the oldest species, N. cordo-
bai and N. occidentalis, the central laminas of the
M3 bear small invaginations in the labial side
(Carranza-Castañeda and Miller, 1988; Carran-
za-Castañeda, 2016), called extraordinary exter-
nal ssures (Mones, 1991). Apparently, this feature
is a primitive dental character in the capybaras,
because it is also present in the M3 of the Pliocene
taxa Phugatherium, “Chapalmatherium” and Hydro-
choeropsis (Deschamps et al., 2013; Vucetich et al.,
2014). This dental morphological characteristic is
not present in the M3 of N. aesopi.
Another dierence between N. cordobai, N. occi-
dentalis, and N. aesopi is observed in the DL. The
DL in N. cordobai and N. occidentalis is between 60
and 70 mm, while in N. aesopi it is 70–90 mm. In
specimen IHNFG-4865, the M3 does not have
the extraordinary external ssures on the laminas
like N. aesopi. In the same way, the mandible of
IHNFG-4866 has a DL of 90.05 mm, longer than
the DL of N. cordobai and N. occidentalis, falling into
the range of N. aesopi.
Material of capybaras from Chapala lake, Jalisco;
Terapa, Sonora; Media Luna lagoon, San Luis
Potosí; and Valsequillo, Puebla, have been referred
to Hydrochoerus (Álvarez, 1971; Hernández-Jun-
quera, 1977; Pichardo, 1997; Mead et al., 2006;
Carranza-Castañeda, 2016).
Neochoerus in the late Pleistocene of Chiapas
Boletín de la Sociedad Geológica Mexicana
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Figure 5 Bivariate plot of M3 and p4 measurements. Black asterisks: Neochoerus aesopi from Villaflores, Chiapas; red dots: N. aesopi
from Chapala Lake, Jalisco (INAH, Mexico City, not catalogued); black dot: N. aesopi from Valsequillo, Puebla (INAH CDMX, “66-I; Y-I”);
purple dot: N. pinckneyi (= N. aesopi, Sanders, 2002); blue dots: N. aesopi mean (Mones, 1991); pink dots: N. sulcidens mean (Mones,
1991); gray dot: N. tarijensis mean (Mones, 1991); yellow dot: N. cordobai (Carranza-Castañeda and Miller, 1988); orange dots: N.
occidentalis (Carranza-Castañeda, 2016); green triangles: Hydrochoerus hydrochaeris (Kerber and Ribeiro, 2011). Red lines: trend of the
genus Neochoerus; green lines: trend of the genus Hydrochoerus.
Neochoerus in the late Pleistocene of Chiapas
11Boletín de la Sociedad Geológica Mexicana
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Álvarez (1971) referred the specimens from
Chapala lake as Hydrochoerus. Recently, Carran-
za-Castañeda (2016) reviewed this material and
mentioned that some specimens have character-
istics of Hydrochoerus, and referred the specimens
labeled with the numbers 78 and 126 as Hydro-
choerus sp. (g. 9, p. 310). Nevertheless, a review of
these specimens from Chapala (housed at the Lab-
oratorio de Arqueozoología, INAH), by one of the
authors (JEP) showed that these specimens have the
Neochoerus mandibular characteristics mentioned
by Mones (1991) that allows the dierentiation of
Neochoerus from Hydrochoerus. Such dierences are
more evident in the DL and the TL. In H. hydro-
chaeris the range of the DL is 35–52.1 mm, while
in H. isthmius it is 34.6–41.7 mm (Mones, 1991). In
Neochoerus the DL has a longer range (60–90 mm).
In the same way, in the Neochoerus species, the
TL range is between 90 and 112 mm (N. cordobai
= 112 mm, N. aesopi = 90–110 mm, N. sulcidens
= 102.6 mm, N. tarijensis = 101 mm), while in
Hydrochoerus the TL range is 61.5–91.4 mm (H.
hydrochaeris = 64–91.4 mm, H. isthmius = 61.5–71.5
mm) (Mones, 1991). Specimen 78 from Chapala
has a DL of 71.97 mm and a TL of 99.26 mm,
measurements within the range of Neochoerus.
Additionally, the masseteric crest begins between
the Pr.s.a and the Pr.I (like in Neochoerus), while in
Hydrochoerus it begins in the anterior part of the
Pr.s.a. On the other hand, specimen 126 has a DL
of 40.3 mm and a TL of 89.87 mm, measurements
within the range of Hydrochoerus. However, the
p4 length is greater than the m2 length, and the
masseteric crest begins in the posterior part of the
Pr.s.a, characteristics of N. aesopi (Mones, 1991).
The DL and TL measurements of the specimen
are indicative of one young individual.
The M3 also exhibits dierences between
Neochoerus and Hydrochoerus. Although the general
morphology is similar, the number of prisms var-
ies. In Neochoerus, the number of prisms is 14 to 17,
while in Hydrochoerus it is 12 to 13 (Mones, 1991;
Flynn, 2008). In some individuals from Chapala,
the M3 has 14 prisms (also mentioned by Carran-
za-Castañeda, 2016), which allows assigning the
specimens to Neochoerus. The size of the M3 in
some specimens from Chapala falls into the range
of Hydrochoerus, whereas the taxonomic assignation
to Neochoerus or Hydrochoerus is dicult (Figure 5A).
However, the variation in the size of the teeth
of capybaras is a consequence of age, which does
not aect signicantly the morphological charac-
teristics (Vucetich et al., 2005). Therefore, the small
size of some individuals is the result of age, and
not due to specic dierentiation.
The bivariate plot of the p4 (Figure 5B) shows
that the size of this molar is more informative
and a better indicator for Neochoerus to Hydrochoerus
dierentiation, although it is the most morpholog-
ically variable tooth (Álvarez, 1971).
Finally, the presence of Hydrochoerus in Chapala
lake is rejected, because the coexistence of two
or more species with the same ecological require-
ments within the same area is not possible.
Hydrochoerus remains have been reported from
Valsequillo, Puebla (Pichardo, 1997). However,
these remains have not been illustrated. Later,
Pérez-Crespo et al. (2014, 2019) mentioned the
presence of Neochoerus sp. in Valsequillo. However,
they are not specic on the basis of the taxonomic
The examination of the incomplete skull from
Valsequillo (housed at Laboratorio de Arqueo-
zoología, INAH, labeled with the number “66-I;
Y-I”) allow us to assign this specimen to Neochoerus
aesopi. The taxonomic assignation is based on the
morphological characteristics of the skull and the
M3. The skull roof is wider than Hydrochoerus, with
the supraoccipital wider and more excavated; lac-
rimal more robust and higher, and the M3 with 15
laminae, and these without extraordinary external
ssures. The size of M3 indicates that this speci-
men is from a juvenile (Figure 5A).
Neochoerus in the late Pleistocene of Chiapas
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Fossil remains of capybaras from Térapa have
been referred to Hydrochoerus sp. (Mead et al., 2006)
and Hydrochoeridae indeterminate (Nunez et
al., 2010). However, this material has never been
described or illustrated. Unfortunately, the reposi-
tory of these fossils is not mentioned and therefore
a revision is not possible. Further, the fossil of capy-
baras from Media Luna lagoon, San Luis Potosí,
assigned as Hydrochoerus sp. (Hernández-Junquera,
1977), was never formally deposited in a museum
and is now missing (Ferrusquía-Villafranca, 2018,
pers. com.). Nevertheless, we do believe that the
capybaras from Térapa and Media Luna lagoon
are Neochoerus, and, considering the temporal
range (late Pleistocene, Rancholabrean) assigned
for both faunas, it is possible to refer this material
as N. aesopi.
Such armation is based upon two assump-
tions: (1) Mones (1984) considered that the reports
of Hydrochoerus in North America are misidenti-
cations of Neochoerus, and (2) the review of the
specimens from Chapala and Valsequillo, identi-
ed as Hydrochoerus, showed that they are actually
The paleoecological aspects of the extinct capy-
baras have been inferred by comparison with the
extant species of Hydrochoerus. Recent capybaras
are semiaquatic and live within lowlands habitats
in the proximity of water, like forested riverbanks,
former riverbeds, brackish wetlands, and man-
grove swamps (Mones and Ojasti, 1986).
Fossil capybaras are usually recovered from
uvial, lacustrine or swampy deposits (Vucetich et
al., 2013), so the lifestyle related to water is sup-
ported. Therefore, the presence of Neochoerus aesopi
in Los Mangos locality indicates the existence of
permanent water bodies in the area during the late
Pleistocene, which is consistent with the lithology
of the outcrops in the study locality. The feeding
habits of Neochoerus can also be inferred through
comparison with feeding habits of H. hydrochaeris.
Hydrochoerus hydrochaeris consumes grasses,
aquatic plants, and occasionally bark, stems, and
leaves (Ojasti, 1973). Recent observations show
that H. hydrochaeris has preference for Hymenachne
amplexicaulis (an aquatic grass) during the wet sea-
son, and feeds on Eleocharis interstincta (a reed) and
Paratheria prostrata (a grass) during the dry season
(Barreto and Quintana, 2013).
Based on the feeding habits of H. hydrochaeris, it
is possible to infer that N. aesopi from Los Mangos
locality fed on dierent types of grasses, reeds,
and shrubbery. This assumption is supported by
the microwear and stable isotopes analyses of δ13C
and δ18O on N. aesopi from La Cinta-Portalitos,
Michoacán-Guanajuato and Valsequillo, Puebla,
and shows that some individuals have a mixed
feeder diet based on C3/C4 plants and other
individuals were C4 grazers (Pérez-Crespo et al.,
2014; Eng-Ponce et al., 2017; Eng-Ponce, 2018).
These data are similar to that obtained from N.
tarijensis from Bolivia, species referred to as a C3/
C4 mixed feeder (MacFaden and Shockey, 1997).
6. Conclusions
The formal description of the capybara fossil
remains from Villaores, Chiapas, allows us to
conrm the specic taxonomy assignation as
Neochoerus aesopi, which adds a new locality for this
taxon in Mexico. It also documents the southern-
most record, until now, for North America, and
increases the spatial range of Neochoerus in the late
The historical presence of Hydrochoerus in
Chapala lake, Jalisco, and Valsequillo, Puebla, is
rejected based upon the review of the specimens
housed in Laboratorio de Arqueozoología, INAH,
and conrms that the only species present in both
areas is Neochoerus aesopi. In the same way, we refer
Neochoerus in the late Pleistocene of Chiapas
13Boletín de la Sociedad Geológica Mexicana
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the capybaras from Térapa and Media Luna
lagoon as N. aesopi. The presence of N. aesopi from
Sonora to Chiapas allows us to hypothesize that
this was the only capybara species present in the
late Pleistocene of Mexico.
The specimens described in this study were col-
lected with the support of the project “Prospec-
ción y resguardo del patrimonio paleontológico
de Chiapas”, nanced by the Government of
Chiapas state. We thank Joaquín Arroyo-Cabrales
for the permission to review the capybaras from
Valsequillo and Chapala housed at Laboratorio
de Arqueozoología, INAH. We are grateful to the
wikipaleo community for sharing bibliography,
and Torrey Nyborg for the English review of the
Finally, we wish to thank Alvaro Mones and an
anonymous reviewer for the helpful suggestions
they made, and Francisco J. Vega for the editorial
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... Phugutherium was present in central México by the Pliocene (early Blancan NALMA) at 3.6 Ma (Vucetich et al. 2015). Neochoerus is found in southern México in the Rancholabrean NALMA (Carbot-Chanona et al. 2020) and in Central México in the early Blancan at 3.5 Ma. These are the oldest verified record of any capybara in North America (Carranza-Castañeda Abstract: We describe a new species of capybara from late Pleistocene deposits (Rancholabrean NALMA) in northern San Diego County, California, USA which tentatively dates to Marine Isotope Stage (MIS) 5 interglacial (~130 ka to 80 ka). ...
... Hydrochoerus has been thought to have been present from the late Pliocene (late Blancan) to the latest Pleistocene (Rancholabrean) in the United States, but not in the Recent (Ahearn 1981; Morgan 2005). The fact that the earliest records of Neochoerus in North American are in the north rather than the south would seem to suggest that its origin was in the north; but the relative lack of fossil producing Previous work: For the purposes of the present study, we adopt the taxonomic classification of capybaras proposed by Vucetich et al. (2013Vucetich et al. ( , 2014Vucetich et al. ( , 2015 and followed in the three most recent papers on North American (NA) capybaras (Albright et al. 2019;Baskin et al. 2020;Carbot-Chanona et al. 2020). Two lineages with a total of three genera are recognized by Vucetich et al. (2015): (1) Phugatherium, with P. dichroplax as the only NA species; and (2) a lineage consisting of Neochoerus, with the NA species N. aesopi; and a Central and South American sister taxon, Hydrochoerus, including the extant H. hydrochaeris and H. isthmius. ...
... We are not convinced by the arguments of Mones (1991), accepted by most recent authors, that all of the specimens of N. pinckneyi referred by him to N. aesopi are correctly allocated, particularly those dating to the Blancan NALMA. Given the significant range in size of the three species allocated to Hydrochoerus, the most parsimonious interpretation, and the one followed here, is that the specimens identified as H. holmesi in the bivariate plot of Ahearn (1981), and those described by others as N. aesopi (Baskin et al. 2020;Carbot-Chanona et al. 2020) are simply younger conspecifics of the large, presumably fully adult individuals identified as Neochoerus pinckneyi. This confusion is exacerbated by the difficulty in aging capybara specimens independent of tooth size. ...
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We describe a new species of capybara from late Pleistocene deposits (Rancholabrean NALMA) in northern San Diego County, California, USA which tentatively dates to Marine Isotope Stage (MIS) 5 interglacial (~130 ka to 80 ka). The specimen represents a new species of Hydrochoerus based on morphological characters of the upper incisor (I1) and the upper (maxillary) third molar (M3). Hydrochoerus hesperotiganites sp. nov. differs from other described species of Hydrochoerus in its larger size, wider skull roof, more robust zygomatic process of the maxilla and descending zygomatic process of the lacrimal and in details of the otic region. The new species is the only confirmed record of fossil Hydrochoerus in North America and is the northwestern-most record of any capybara in North America. All previous records of fossil capybara from North America represent one of two extinct genera, Neochoerus or Phugatherium. Northward dispersal of capybaras from central and southern México probably occurred along the coasts of Sinaloa and Sonora, entering the north or northeast flowing drainages which enter the Gulf of California, then further north into the San Simon drainage to the Gila River and ultimately intothe Colorado River, or directly northward along the coast of Sonora to the mouth of the Colorado River.
... Neochoerus is known from the Pliocene and Pleistocene (Blancan to Rancholabrean) of North and Central America (Carranza-Castañeda, 2016) and from the middle to late Pleistocene (Ensenadan to Lujanian) of South America (Vucetich et al., 2015). Hydrochoerus, its sister genus, is known from the middle Pleistocene to Recent of South and Central America (Vucetich et al., 2015); records north of Panama have been discounted (Carbot-Chanona et al., 2020). Phugatherium and Hydrochoeropsis are known from the Pliocene of South America (Vucetich et al., 2015). ...
... 5a). These fissures are not diagnostic for Phugatherium (Carbot-Chanona et al., 2020). They are present but reduced in the M3 of Pliocene Neochoerus and absent in N. aesopi (Carbot-Chanona et al, 2020). ...
... These fissures are not diagnostic for Phugatherium (Carbot-Chanona et al., 2020). They are present but reduced in the M3 of Pliocene Neochoerus and absent in N. aesopi (Carbot-Chanona et al, 2020). ...
A capybara jaw (Rodentia, Caviidae, Hydrochoerinae) and an isolated lower tooth fragment were recovered from dredge spoils on Pelican Island in Galveston Bay, Gulf Coast of Texas. The attached matrix on the jaw and most of the dredged material is clay, indicative of the latest Pleistocene Beaumont Formation which underlies the Holocene deposits. In the latest Pleistocene (Rancholabrean) of the United States, capybaras are known from along the Gulf and Atlantic coasts in Texas, Florida, Georgia, South Carolina, and Virginia.These Rancholabrean capybaras have been assigned to three different taxa: Neochoerus pinckneyi Hay, 1923 for the largest size specimens, Hydrochoerus holmesi Simpson, 1928 for the somewhat smaller specimens, or Neochoerus aesopi Leidy, 1853, a name that had been considered invalid because it was not adequately diagnosed, if there is only one late Pleistocene species of North American capybara. The p4 in the new Texas mandible is much smaller than the genotype of N. pinckneyi from the Aransas River in South Texas and similar in size to H. holmesi from the Pleistocene of Florida and Recent H. hydrochaeris. However cheek tooth size and occlusal pattern in Recent capybaras varies significantly with age. Hydrochoerus holmesi cannot be distinguished from N. pinckneyi. None of the late Pleistocene capybaras of South Carolina, including the type and referred specimens of N. aesopi, have any characteristics to differentiate them from H. holmesi or N. pinckneyi. We therefore assign all the Texas and South Carolina specimens to N. aesopi.
Mathematical models are a helpful tool that can help paleoecology research advance in similar ways as the ones already used in theoretical ecology. In this article, we use a mathematical model based on differential equations to estimate the past Mammuthus columbi population in the Valsequillo Basin, Puebla, Mexico. We calibrated the model based on the biological and etiologic parameters of the African elephant Loxodonta africana. In addition to the mean population, the analysis allows inferring the population dynamics of the M. columbi on the Valsequillo Basin. The model is based on the ecological interactions between M. columbi and its food resource. It was found that the population must have been oscillating before an equilibrium was reached. Several potential scenarios based on on-site food production (grass) are here analyzed. It was found that a good efficiency of the M. columbi to find food can lead to recurrent cycles of abundance and famine. In this situation, the M. columbi populations must have emigrate and then immigrate in periodic circles to avoid starvation
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Equids are among the most common mammals found in faunal assemblages of Late Pleistocene age in Mexico. Much of what is known about the Equus species is the result of studies conducted in central and northern Mexico; much less is known about species in lower latitudes of Mexico. Here we describe three species that inhabited Oaxaca and Chiapas states. The fossil localities are in northwestern and central Oaxaca, as well as the central part of Chiapas. In Oaxaca, the largest species, Equus mexicanus, and the medium-sized Equus conversidens are represented by mandibles, skulls, diverse isolated teeth and some postcranial bones, while the smallest species, Haringtonhippus francisci is represented by a skull fragment and few isolated teeth. In Chiapas, E. mexicanus is represented by a mandible and several isolated teeth, E. conversidens by several mandibles and diverse isolated teeth, and H. francisci by isolated teeth and two mandibles. AMS radiocarbon and uranium dating of some of the equid localities in Oaxaca and Chiapas indicate that they were at least present since approximately 44,000 Cal BP years, they were common around 30,000 Cal BP years, and were still present at the end of the Pleistocene, around 12,000 years ago. The record of H. francisci from Chiapas is the youngest in North America. A cluster analysis of extended mesowear data and a discriminant analysis showed that Equus conversidens from Chiapas was obligate grazer, whilst the rest of the equids were variable grazers. Geographic distribution of localities in southern Mexico indicates that during the Pleistocene the equid species moved across the Transvolcanic Belt-Sierra Madre del Sur temperate biogeographic corridor and the Tamaulipas-Central America Gulf Lowlands tropical corridor.
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Beschreibung Put yourself in the box seat at exam time ... The days of cramming dry anatomical facts are over. It’s time to look at anatomy as an opportunity to appreciate a fascinating world of relationships and interconnections. Featuring: - The complete spectrum of systematic and topographic anatomy: clearly structured and vividly presented, featuring superb high-quality images - A combined text and atlas: takes into account a variety of species, an ideal resource for developing a comprehensive understanding of anatomical structures and relationships - Integrated sectional anatomy and contemporary diagnostic imaging: a window into the application of anatomy in diagnostics Highlights you won’t want to miss: - A new chapter on avian anatomy: the fundamental structural features of birds, at a glance - Over 1100 exceptional images: anatomical specimens and histological images, thin slice plastinations, colour schematics, diagnostic imaging, sectional anatomy - Numerous references to clinical and applied anatomy: including equine endoscopy, arthrocentesis, examination of the udder, rectal examination and laparotomy - A unique bonus: CT, MRI and ultrasonographic images Bringing anatomy to life!
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The environment of four late Pleistocene Mexican sites, with human presence, was inferred using carbon and oxygen stable isotope relationships from herbivores enamel, which lived at those sites and was obtained from previous studies. Those analyses showed the presence of forest with grasslands at the sites Fin del Mundo, Rancho La Amapola, and Valsequillo, while Tocuila had grasslands and more humid environmental conditions than at present. At the four localities, these environments favored the coexistence of several herbivorous species and allowed the establishment of the first people in Mexico.
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Studies on the family H ydrochoeridae, XIV. A systematic Revision (Mam-malia: Rodentia): In this paper we present a new generic and specific arrangement of th e family, with a sharp reduction of the number of names as well as new combinations. Reviewed diagnosis fo r family and subfamilies are given. A few controversial points are briefly discussed. Este trabajo representa un extracto de las conclusiones sistemáticas de nuestra "Monografía sobre la familia Hydrochoeridae", que debido a su extensión, su publicación se verá demorada por algún tiempo. De la lista publicada por nosotros (1975a), debe eliminarse "Protohydrochoerus" tahuamanii SPILLMANN 1949, que es un Dinomyidae, y que por otra parte debe considerarse un nomen vanum. En ese mismo trabajo no se incluyó el nombre Hydrochoerus antiquus AMEGHINO 1914: 101, por tratarse de un nomen nudum, ni Hydrochoerus carinatus REINHARDT 1867: 341 (ex LUND), que también es un nomen nudum y es sinónimo de Neochoerus sulcidens (LUND). 1) Este artículo constituye el último de la serie. Las anteriores contribuciones fueron
The Yolomécatl area, northwestern Oaxaca, Sierra Madre del Sur Morphotectonic Province, Mexico, lies between 17°25′N and 17°30′N latitude, 97°29′W and 97°36′W longitude, at 2200–2500 m above sea level, and includes ∼90 km² of rugged territory, where lithostratigraphic units of Late Jurassic to Quaternary age crop out. The Tertiary succession, which unconformably overlies Mesozoic formations, includes the Nduayaco ‘Group,’ a stack of intermediate lava flows, and the Yolomécatl Formation, a lacustrine/fluvial sequence ∼650 m thick, sparsely interbedded by tuff sheets. One tuff with an ⁴⁰Ar/³⁹Ar date of 40.3 ± 1.0 Ma places this formation and the southernmost Eocene local fauna from North America in the late middle Eocene (Bartonian). The volcanic Nicananduta ‘Group’ (∼27 Ma) overlies the Yolomécatl Formation. The Yolomécatl local fauna includes, among others, two new taxa: Douglassciurus oaxacaensis, sp. nov., so far the oldest sciurid in the world, and the enigmatic Protozetamys mixtecus, gen. et sp. nov., which despite its early age (late middle Eocene), already shows adaptations to process fibrous or abrasive food. If the caviomorph affinities of Protozetamys are correct, they would suggest dispersal northward of a South American rodent lineage. These finds strengthen the hypothesis that this region (southeastern Mexico) was a center of diversification and extend the record of Paleogene mammals southward ∼553 km (∼3°30′ latitude), i.e., from Marfíl, Guanajuato (in central Mexico), to Yolomécatl, Oaxaca (in southeastern Mexico). Citation for this article: Ferrusquía-Villafranca, I., L. J. Flynn, J. E. Ruiz-González, J. R. Torres-Hernández, and E. Martínez-Hernández. 2018. New Eocene rodents from northwestern Oaxaca, southeastern Mexico, and their paleobiological significance. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1514615.
El “carpincho” es un roedor de gran talla ampliamente distribuido en la zona de llanos y humedales de Sudamérica. La información anatómica sobre el esqueleto axial de esta especie es escasa. El objetivo del ensayo fue describir el esqueleto axial de Hydrochoerus hydrochaeris. Se utilizaron tres cadáveres (dos machos y una hembra). Los huesos se obtuvieron por maceración, siendo luego tratados con hipoclorito de sodio al 20%. Las descripciones anatómicas se avalaron con registros fotográficos. Se halló un total de 34 huesos de la cabeza (incluidos los huesos del oído y considerando el cornete nasal dorsal como parte del hueso etmoides), 36 vértebras (7 cervicales, 13 torácicas, 6 lumbares, 4 sacras y 6 caudales), 26 costillas, y el esternón con 6 esternebras. Osteológicamente los huesos de la cara resultaron más fuertes que los del cráneo. Se espera que los estudios anatómicos de H. hydrochaeris contribuyan a mejorar su manejo sanitario y productivo.
The Caviomorphs rodents collected in the late Blancan sedimentary sequence of San Buenaventura, in the Tecolotlán Basin, Jalisco, are described. The study and comparison with Neochoerus cordobae fossils collected in the early Blancan San Miguel Allende region have revealed that the Buenaventura specimens have more progressive characters than N. cordobae. Distinguishing features of the new species are: 1) the secondary internal flexid (h.t.i.), in the second prism of m2, divides the prism in two isolated plates; 2) the secondary external flexid (h.s.e.), in m3 exceeds 50% of the prism, and 3) the secondary internal flexid (h.s.i.), in both m1 and m3 has a 90% depth of the prism. These characters are shared with a specimen collected from late Blancan-Irvingtonian sedimentary deposits exposed at Golfo de Santa Clara, Sonora, which is referred to Neochoerus occidentalis. The taxonomic position of Neochoerus cordobae and Phugatherium dichroplax from the late Blancan fauna of 111 Ranch, Arizona is also discussed. The presence of Neochoerus occidentalis in Tecolotlán and in the Golfo de Santa Clara faunas is evidence that the western part of Mexico was a corridor where mammals migrated toward the northern region of Mexico and in general to the SW portion of North America.
Through the use of the 13C/12C and 18O/16O isotopic relationships found at enamel and osteodentine, here it is inferred the diet and preferred habitat in which five extinct herbivore species from the Late Pleistocene of Valsequillo, Puebla, Mexico. The horses, mammoths, and sloths showed a diet mainly based in C4, meanwhile the capybaraand gomphotheres were mixed C3/C4 feeders. The vegetation in which those animals lived was open with some trees, similar to the one proposed in other studies based in some macromammals species found in the locality.