A Freshwater palaeoecosystem from a new locality of the Cerro del Pueblo Formation (Campanian) in Coahuila, Mexico

1. Ricardo M. Ávila Hernándezᵃ*, Alexander M. Czajaᵃ, & Héctor E. Rivera-Sylvaᵇ
ᵃFacultad de Ciencias Biológicas de la Universidad Juárez del Estado de Durango, México
ᵇDepartamento de Paleontología de Museo del Desierto, México
Vertebrate paleofauna from a new locality of the Cerro del Pueblo
Formation (Campanian) in Coahuila, Mexico
Introduction
The state of Coahuila is known for having the largest
number of paleontological sites in the entire Mexican
Republic (Rivera-Sylva et al., 2014). It has a great
diversity of fossil remains of invertebrates, vertebrates
and plants (Villanueva-Amadoz et al., 2014), most of
them from the Upper Cretaceous of approximately 73
million years (Eberth et al., 2004; Vogt et al., 2016).
Especially the municipality of General Cepeda in the
town of Porvenir de Jalpa is an area rich in fossil records
and dinosaur ichnites(Vogt et al., 2016; Rivera-Sylva et
al., 2017; Rivera-Sylva et al., 2019) forming part of a
rock formation that extends from Parras to Saltillo, called:
Cerro del Pueblo Formation. It is worth mentioning that
the paleontological material is strongly eroded by
constant exposure to the elements, and it is also part of a
river runoff channel from a hill.
*Corresponding author: zooty2@yahoo.com.mx

2. Recently, a new locality with fossil content was discovered in the
municipality of General Cepeda, dated between 73 and 72 million
years in the Upper Creatceous of the Campanian (Eberth et al., 2004;
Vogt et al., 2016), and the coordinates 25°30’49.9” N y 101°41’59.5
W with a height of 1337 meters above sea level. All possible material
was collected and taken to the paleontological laboratory of the
Museo del Desierto in Saltillo for cleaning and photographic capture
with a camera Canon EOS Rebel T7, lens Canon EF-S 55-250mm
1:4-5.6 IS II. And a stereoscopic Carl Zeiss Suzhou; Axiocam Erc 5s.
Finally, for its identification will use articles and specialized
literature.
Methodology
1
2
3
4
5
6
Collect material
Transport material to the
museum.
Cleaning
Identification
Reconstruction
Locality
location
Photographs

3. Tyrannosauridae
Tyrannosauridae indet.
The only viable thing that was analyzed in this material was the number of
denticles per mm, giving us 2 denticles/mm, which is a characteristic already
reported in the state of Coahuila. And the LP-28 material was the only one to
present an ovoid shape in dorsal view and transverse base (Rivera-Sylva et al.,
2009; Rivera-Sylva et al., 2019).
Dinosauria
Theropoda
Coelurosauria
Dromaeosauridae
Dromaeosauridae indet.
Although the ungual is fragmented on its proximal and
distal side; its strange dorsal 60° and ventral 50° curvature
in the shape of a hook and flattened laterally makes it
identify as a dromaeosaurine. The manual phalanx has a
similar shape to the species Deinonychus antirrhopus
(Ostrom, 1969) with the lateral ligament fossae semi-
circular and positioned in the upper part of the lateral
condyle. The continuity of the bone shows to be thin
proximally to be a manual phalanx and in its cross section
it shows to be filled with sediment. The ilium shows a
deciduous postacetabular narrowing and the preacetabular
one remains in the same dimension towards its crest. The
pubic pedicel shows slightly but at a noticeable angle
towards the postacetabulum (Norell and Makovicky, 2004).
Eucryptodira
Trionychidae
Trionychidae indet.
It is common in this family to have this type of ornament and fortunately some
fragments managed to maintain the marginal shape of their shell; while others
on its ventral side show the shape of the ribs. The dimensions of the pits vary
between 1 and 3 mm in diameter in each fragment, in addition to that some
have thicknesses greater than the others, possibly belonging to different
ontogenetic and/or species states (Rodríguez-de la Rosa and Cevallos-Ferriz,
1998; Brinkman and Rodríguez de la Rosa, 2006; Brinkman DB, 2014; Rivera-
Sylva et al., 2019).
Dermatemydidae
Hoplochelys
Hoplochelys sp.
The genus agrees with the description of
pronounced dorsal ridges and a fine
dotted sculpture seen with a handlens.
(Rodríguez-de la Rosa and Cevallos-
Ferriz, 1998; Brinkman and Rodríguez de
la Rosa, 2006; Brinkman DB, 2014,
Rivera-Sylva et al., 2019).
Testudines
Cryptodira
Chelydridae
Chelydridae indet.
Adocidae
Adocidae indet.
The sculpture is generally dim with small
pits seen with a handlens (Sankey, 2006).
In this case, it is a rectangular fragment
with a patterned surface of small tubers,
without any other protruding
ornamentation (Brinkman and Rodríguez
de la Rosa, 2006; Rivera-Sylva et al.,
2019).
It comes to be confused with the ornamental
structure of the genus Hoplochelys, but in this
case the very marked curvature of a prominent
multi-crested carapace makes it have an irregular
and rough surface like Protochelydra (Cevallos-
Ferriz, 1998; Brinkman and Rodríguez de la
Rosa, 2006; Rivera-Sylva et al., 2019).
Results and Discussion
10
mm
20 mm
10 mm
10 mm
10
mm
20 mm
2
mm

4. The larger epoccipital expresses a partial fusion because it presents an extension that protrudes from the triangular shape to a different
direction, thus showing the continuity of the frill and without a mark of the articular groove except for the anterior view, which is delimited
by a continuous straight contour, being that of a sub-adult (Horner and Goodwin, 2008).
The tooth presents enamel on crown with all three carinae: the deeply keeled central carina and two smaller lateral secondary carinae
(Ostrom, 1966; Dodson et al., 2004). The mesial edge having striated and on the mesial side it shows an inverted“V”curve that indicates
continuity towards the lingual root (Dodson et al., 2004; Ostrom, 1966). And in the apical part of the tooth, there is a well from which the
tip of the next replacement tooth fitted; (Ostrom, 1966; Dodson et al., 2004).
Ornithiscia
Cerapoda
Parkosauridae
Parkosauridae indet.
In basal ornithpods there is a good report of several
species on their caudal vertebrae, all of which are
amphicoelous and progressively lower and thinner in
the distal direction of the tail. This is because the
most proximal centers make them more concave
ventrally due to the chevron marks that are more
pronounced and the more distal ones reduce their
articulation and are thinner ventrally (Norman et al.,
2004). Recently, Rivera-Sylva et al. (2018) the first
presence of this family has been described, which
helps reinforce its existence with this material.
LP-31 present features of hadrosaurine tooth except for its length and the absence
of denticles, since in most it is fragmented or worn during the life of the animal, a
sign of this is that shows to be naturally worn and close to being ejected because
the crown only shows its lower lanceolate shape, apart from the labial side it
shows a semi-smooth surface of black coloration without fragmenting. (Horner et
al., 2004; Rivera-Sylva et al., 2019). The coracoid has similar “D” shape to the
species Magnapaulia laticaudus (Prieto-Márquez et al., 2012) in glenoid fossa.
But our material lacks a bicipital tubercle like Magnapaulia. However, they
present similar size with 10 cm width and 12 cm length. It belongs to
Hadrosaurinae subfamily.
Hadrosauridae
Hadrosauridae indet.
30
mm
10
mm
6
cm
6
cm
10 mm
30
mm
Ceratopsia
Ceratopsidae
Ceratopsidae indet.
Results and Discussion

5. Hadrosauridae
Trionychidae
Dromaeosauridae
Ceratopsidae
Terópodos indet.
Tyrannosauridae
Parksosauridae
Dermatemydidae
Chelydridae
Adocidae
References
-Brinkman, D. B. (2014). Turtles of the Mesozoic of Mexico. At H. E. Rivera-Sylva, K. Carpenter, & E. Frey, Dinosaurs and Other Reptiles From the Mesozoic of Mexico (pages. 30-43).
Bloomington: Indiana.
-Norell, M. A., & Makovicky, P. J. (2004). Dromaeosauridae. At D. B. Weishampel, P. Dodson, & H. Osmólska, Dromaeosauridae (pages. 196-209). London: University of California Press.
-Norman, D. B., Sues, H.-D., Witmer, L. M., & Coria, R. A. (2004). Basal Ornithopoda. At D. B. Weishampel, P. Dodson, & H. Osmólska, The Dinosauria (pages. 393-412). London: University
of California Press. Ostrom, J. H. (1969).
-Horner, J. R., & Goodwin, M. B. (2008). Ontogeny of Cranial Epi-Ossifications in Triceratops. The Society of Vertebrate Paleontology, 134-144.
-Horner, J. R., Weishampel, D. B., & Forster, C. A. (2004). Hadrosauridae. At D. B. Weishampel, P. Dodson, & H. Osmólska, The Dinosauria (pages. 438-463). London: University of California
Press.
-Rivera-Sylva, H. E., Frey, E., Stinnesbeck, W., Amezcua Torres, N., & Flores Huerta, D. (2019). Terrestrial vertebrate paleocommunities from the Cerro del Pueblo Formation (Late Cretaceous;
Late Campanian) at Las Águilas, Coahuila, Mexico. PALAEOVERTEBRATA, 1-12.
The new locality was named “La Ponchada” and it shows a sufficient diversity of families which
dinosauria class dominate with 65.29% presence. Hadrosauridae 30.61%, Dromaeosauridae 10.2%,
Ceratopside, Theropoda 8.16% everyone, and Tyrannosauridae, Parksosauridae 4.08% everyone. In
Testudines order dominate Trionychidae family with 26.53%, followed by Dermatemydidae with
4.08%, and finally Chelydridae, Adocidae with 2.04% everyone. This site is described as part of a
freshwater ecosystem near to an estuary.
Conclusion
4.08%
8.16%
2.04%
30.61%
26.53%
10.2%