Kleyton M. Cantalice, Jesús Alvarado-Ortega, Jesús A. Diaz-Cruz, Bruno A. Than-Marchese and Stephanie Pacheco-Ordaz

1. The importance of Paleocene fossil fishes from Southeastern Mexico to understand
the origin and diversification of some marine modern groups
Cantalice KM1*, Alvarado-Ortega J1, Diaz-Cruz JA1, Than-Marchese BA2, Pacheco-Ordaz S3
1 Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad de México, México
2 Instituto de Ciencias Biológicas, Universidad de Ciencias y Artes de Chiapas, Tuxtla Gutiérrez, Chiapas, México
3 Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México
INTRODUCTION Belisario Domínguez and División del Norte quarries
The fossil fishes from Paleocene of Southeastern Mexico were
accidentally found by archeologists exploring the Ancestral site of
Palenque (A). Inside the temples, they discover several fossil
specimens, including two yellowish slabs containing fishes (B).
Posterior prospections around the archeological city lead to know
two fossil localities with the same features of the rocks found
inside the temples: the Belisario Domínguez and División del
Norte quarries.
The Palace, one of the slab was on
rubble in this site of the
Archeological city of Palenque. The
other is a tap of tomb found in
another site: the Bat group.
The two slabs containing fossil
fishes (MUPAL 2587, 2731) found in
the Archaeological city of Palenque
and their respective schematic
drawings evidenced the presence of
distinct fishes.
* Corresponding author, email: kleytonbio@yahoo.com.br
The Belisario Domínguez quarry is under the coordinates
17°25'28.60"N and 91°58'46.80"W, while the División del Norte is
in 17°16'12.17"N and 97°40'40.7"W, both inside a dense jungle
close to the archeological city of Palenque (C). These quarries
belong to the Tenejapa-Lacandón Formation. The sediments
consist of limestone marls deposited in laminated and parallel
strata, which predominantly show yellowish-creamy colors and
eventually have dark-grey silicified bands (D-G). Both microfossil
index and isotope studies indicates the Danian Age (63 ± 1.5 Ma),
the first floor of the Cenozoic Era.
Extract points of Belisario Domínguez (D-F) and División del Norte (E-
G) quarries, showing the laminated strata almost completely covered
by vegetation, which makes it difficult both the fossil extraction and
determination of the length and deepness of these fossil beds.
Geographic ubication of Paleocene sites in SE Mexico. The Belisario
Domínguez is in the limits of Palenque and Salto de Agua city; while
División del Norte is separated of the archeological city of Palenque just by
a mountain.
A
B
C
D E
F G

2. MATERIAL AND METHODS
Exceptional preservation
Although currently only a small portion of both
quarries have been exploited, is remarkable the
number of fossil specimens collected in these sites.
To date, foraminifers, ostracods, and plant remains
also compose the biodiversity of Paleocene
quarries of Southeastern Mexico, however, the fish
diversity is extraordinary and exceptionally well-
preserved (A-C). Articulated fish remains are rare to
Early Paleocene, which make the fossil fishes of
these localities the “Rosetta stone” to understand
the early diversification of some marine groups
that currently are diverse and widely distributed
along with saltwater and brackish environments.
Types of fossil fish preservation in Paleocene quarries of
Chiapas, Mexico: (A) disarticulated bones; (B) isolated
complete specimens; (C) specimens in several grades of
preservation in massive mortality.
Annual expeditions to Chiapas have been performing since 2008 and
a considerable number of fossil specimens were collected (D).
Currently, they are housed at the National Collection of Paleontology
of Mexico (Colección Nacional de Paleontología- UNAM) (E). At least
200 rock samples containing fossils of these localities are in the
geographical reference section of the collection waiting to be
studied; while 17 samples formally used in scientific researches are
definitively catalogued into the Type section.
When possible, the morphological features are included in a data
matrix (J) along with other taxa to evidence the ancestry (i.e.
phylogenetic) relationships of the fossil studied (K). Usually, the
matrix is obtained with Mesquite software (L). Parsimony-based
phylogenies are obtained with TNT (M), while Mr. Bayes software
(N) is used to Bayesian inferences.
At the laboratory, the work comprises to perform a fine cleaning
of small patches of sediments using both mechanical tools and
chemical substances. Furthermore, when necessary silicon
molds (F) and transferring resin techniques (G) are employed to
the better observation of the material.
After the preparation, the work consists of the morphological
description and comparative anatomy. To perform this, measures,
counts, and the osteological description are retrieved and
compared with other species and the data in the literature.
A B
C
D E
H
I
F
J K
L M N
G

3. RESULTS
Species diagnosis Phylogenetic relationships
Fossilized birth-death
The aim of this study also is using the fossil species described for calibration of
divergence-time estimation in phylogenetic trees. The biggest challenges faced so far
are: (1) the lack previous morphology-based phylogenies to include the species; (2) the
lack of congruence between morphological and molecular classifications, that prevents
the use of these species to estimate an absolute timescale calibration
*To date, we are focusing here,
the percomorphs, an extremely
diverse group of fishes that
comprises the latest divergent
spiny-rayed fish lineage.
A total of 8 taxa are recognized. Furthermore
At least four more new species are under study.
Superclass Actinopterygii
Subclass Neopterygii
Order Pycnodontiformes
Family Pycnodontidae
Genus Pycnodus (A)
Infraclass Teleostei
Cohort Elopomorpha
Order Anguilliformes (B)
Supercohort Osteoglossomorpha
Family Osteoglossidae
Genus Phaerodus (C)
Supercohort Clupeocephala
Cohort Otomorpha
OrdeirClupeiformes
Family Clupeidae (D)
Cohort Euteleosteomorpha
Subsection Acanthomorphata
Division Acanthopterygii
Subdivision Percomorphaceae*
Kelemejtubus castroi (E)
Series Syngantharia
Oder Syngnathiformes
Family Eekaulostomidae
Eekauslostomus cuevasae (F)
Series Ovalentaria
Family Pomacentridae
Chaychanus gonzalezorum (G)
Series Eupercaria
Order Perciformes
Suborder Serranoidei
Family Serranidae
Paleoserranus lakamhae (H)
Maximum parsimony tree showing
the marine Paleocene fossil species
Eekaulostomus cuevasae as the
earliest divergent taxon of the
superfamily Aulostomoidea. There is
a strong evidence that flutemouth
fishes are primary armored and,
posteriorly, derived into species
with small scales or even without
scales recovering the body, as we
can see in the present day.
Superfamily
Aulostomoidea
A
B
C
D
E
F
G
H

4. DISCUSSION
Temporal expansion
Biogeographic expansion The rise of modern reef fauna?
The importance of Paleocene fossil fishes of Mexico
Fauna after the disaster
Flutemouths DamselfishesSeabasses
Bolca fishes
SE Mexico fishes
The K/Pg massive extinction was a
remarkable event that drastically
changed the life around the planet. Since
they are dated as the beginning of the
Paleogene, the SE Mexico fossil localities
provide important information about
biodiversity just after this event.
Furthermore, these localities are only
500km from the Crater of Chicxulub,
formed by a meteorite that should be
one the responsible for this massive
extinction.
Percomorph fishes discovered in SE Mexico fossil
localities have not been reported for the Danian Age yet.
Most of their relatives are reported in Eocene limestones
from Bolca, an emblematic Lagerstätten from Italy or in
the London Clay Formation, United Kingdom. This means
that the fauna in Early Paleocene outcrops of SE Mexico
is pushing back 13 Ma the minimal age of some marine
groups!
Percomorph fossil species found in Early Paleocene outcrops of Mexico are closely related
with modern groups that currently inhabiting coral reef systems. Nevertheless, the
presence of corals is not confirmed in these localities; the environment interpreted is a
shallow marine habitat with the bottom compose mainly by seagrass beds. This piece of
evidence is an important key to understand how modern fishes dominate coral reef
systems, resulting in the most diverse vertebrate group widely distributed along with
marine environments nowadays.
Fossil fishes closely related with the extinct percomorphs of SE Mexico are
mainly distributed in European localities. It means that the species herein
reported are not only the oldest reports but also the firsts notifications in
America to their respective groups. This is a strong evidence that the Caribbean
Sea was important to the early diversification of some modern marine
percomorphs.

5. CONCLUSIONS MAIN REFERENCES
Thanks! ¡Gracias! Obrigado!
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https://repository.si.edu/handle/10088/9786
• Belisario Domínguez and Division del Norte quarries are two marine Paleocene
fossil localities in Southeastern Mexico remarkable by the number of well-
preserved specimens;
• The Danian Age (Early Paleocene) and their geographic ubication make these
localities unique to understand the biodiversity just after the K/Pg boundary;
• To date, foraminifers, ostracods, plants, and several fossil fishes composes the
biodiversity of Paleocene marine environments of SE Mexico;
• The fishes are the most representative group with eight taxa formally described and
at least more four taxa are under description;
• Fossil species of the subdivision Percomorphaceae described in the Paleocene of SE
Mexico indicate an early diversification of some groups in the beginning of the
Paleogene and suggest to the Caribbean Sea as the point of origin and
diversification for some marine fishes;
• When included in a phylogenetic context, the Paleocene fishes of SE Mexico reveals
unprecedent information about evolutionary trends through the time.