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Campanian terrestrial arthropods from the Cerro del Pueblo

Formation, Difunta Group in northeastern Mexico















Instituto de Biología, UNAM, Ciudad Universitaria, Coyoacán, 04510 México D.F., México;


Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, POB  106, 840 05 Bratislava 45, Slovak Republic;

Arthropoda Laboratory of the Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya 123, 117868 Moscow, Russia


Instituto de Geología, UNAM, Ciudad Universitaria, Coyoacán, 04510 México D.F., México;;


Coordinación de Paleontología, SEP Coahuila-Museo del Desierto, Saltillo, 25000 Coahuila, México;

(Manuscript received July 20, 2005; accepted in revised form December 8, 2005)

Abstract: The Campanian assemblage of arthropods from the Cerro del Pueblo Formation in northeastern Mexico
display some primitive characteristics. It consists of a small spider, a dragonfly assigned to the Libelluloidea, and
cockroach  Xonpepetla rinconensis Cifuentes-Ruiz et Vršanský, gen. et sp. nov. – the latest record of the family
Blattulidae and appears to be derived from the Aptian or Albian Cretaceous cockroaches of the genus Elisama Giebel,
1856 from the Crato Formation, Brazil.

Key words: Creataceous, Campanian, NE Mexico,  Insecta, Odonata, Blattaria ( = Blattodea), new genus, new species,


The fossil record of terrestrial arthropods in Mexico is
scarce. A preliminary report on Cretaceous and Oli-
gocene insects from northeastern and central Mexico was
presented by Cifuentes-Ruiz et al. (2002). Most of the
few arachnid reports from Mexico come from the Mi-
ocene Simojovel amber in Chiapas (Petrunkevitch 1963,
1971; Perrilliat 1989; Poinar 1992; Santiago-Blay & Poi-
nar 1993; García-Villafuerte & Vega 2002), where insects
are well known and diverse (Poinar & Doyen 1992; Poin-
ar & Brown 2002; Engel 2004 etc.). A Cretaceous spider
has been reported from the Albian Tlayúa Formation in
Puebla (Feldmann et al. 1998). One odonate larva (Feld-
mann et al. 1998) and a pair of tipulid wings (Pantoja-
Alor 1992) were described from the Lower Cretaceous
Tlayúa Formation of Tepexi de Rodríguez, Puebla. An-
other odonate larva has been reported from the Lower
Cretaceous Sierra Madre Formation in Chiapas (Vega et
al. 2003b). An Upper Permian insect was described by
Carpenter & Miller (1937) from Valle Las Delicias in
Coahuila. More recently, Epicauta sp. was described
from Pliocene beds of Jalisco (Zaragoza-Caballero & Ve-
lasco-de León 2003).

The Cerro del Pueblo Formation is the oldest unit of the

Difunta Group (Figs. 1—2). It was deposited in sedimentary
basins Parras and La Popa with a total thickness of more
than 4000 m (McBride et al. 1974). Since its original de-
scription (Murray et al. 1962), the Cerro del Pueblo For-
mation has attracted the attention of diverse investigators
due to its diversity of fossils including pollen, leaves,
fruits, coprolites, corals, gastropods, bivalves, ammonites,

crustaceans, annelids, echinoids, reptile tracks and dino-
saur bones (Wolleben 1977; Rodríguez de La Rosa &
Cevallos-Ferriz 1994, 1998; Rodríguez de La Rosa et al.
1998, 2002; Hernández et al. 1995; De León-Dávila et al.
1999; Kirkland et al. 2000; Brinkman et al. 2002; Kirk-
land & Aguillón-Martínez 2002; Eberth et al. 2003; Perril-
liat et al. 2003; Vega et al. 2003a, 2004). Ammonites
include sphenodiscid forms (unpublished observation).
Eberth et al. (2004) reported Inoceramus vanuxemi from
Rincón Colorado and La Escondida sections of the Cerro
del Pueblo Formation, and based on reports of this species
in localities with baculitids (Kauffman et al. 1993), they
suggested  I. vanuxemi can be considered as a Middle—Late
Campanian index fossil.

The Campanian age has been recently suggested for

the Cerro del Pueblo Formation based on magnetostrati-
graphic data (Eberth et al. 2004). These authors measured
a total thickness of 449 m for the formation at the study
localities here reported, deposited between magneto-
zones  32n.3r—32n.2n, an interval that corresponds to the
Western Interior biozones of Baculites reesidei and  B. jens-
eni, and suggest a maximum age of 72.5 Ma for the Cerro
del Pueblo Formation. Eberth et al. (2004) also reported that
these sediments were deposited in an embayment where
sediments prograded to the east and northwest, and formed
a thick uppermost Cretaceous to Lower Tertiary Difunta
Group sequence in the Parras Basin (Figs. 2—3).

The assemblage appear to be the only Campanian one

known worldwide.

Vein nomenclature for the dragonfly wing (Rieck &

Kukalová-Peck 1984): RA = radius anterior; RP = radius
posterior (RP1, RP2);  IR = interradial (IR1, IR2); MA = me-

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Fig. 1.  Location of study area in northeastern Mexico, and placement of
localities IGM 3500 (A) and IGM 3501 (B).

Fig. 2. Cretaceous and Tertiary stratigraphic units of the Parras Basin, with relative stratigraphic position of studied samples (arrow).

dia anterior. For the cockroach: A = anal; CuP = cu-
bitus posterior; Sc = subcosta; R = radius; CuA =
cubitus anterior; M = media.

Localities and paleoenvironment

Material was collected in two localities from

the  basal portion of the Cerro del Pueblo Forma-
tion. The first one (A Locality; Rincón Colorado 2;
IGM 3500) is found next to the dirtroad that
leads to Rincón Colorado town, approximately
40 km  west of Saltillo (Fig. 1), 25°45

’20” N,


’21” W. Lithology is represented by olive-

grey mudstone, in which scarce palm and other
angiosperm leaves were found. The second (B Lo-
cality; Presa San Antonio; IGM 3501) is in Ejido
Presa San Antonio, approximately 70 km west of
Saltillo (Fig. 1), at 25° 28

’ 05” N, 101° 42’ 48” W.

Fine olive sandstone crops out here, and relevant
dinosaur remains have been recovered from the
same locality. Both lateral and vertical facies
changes can be detected in relatively short dis-
tances. The formation consists of cyclic alternations
of marine, estuarine and freshwater environments.
The described specimens were deposited in lakes
or small ponds, associated with the deltaic system
that prevailed in northeastern Mexico during
Campanian times (Fig. 3). The organisms here de-
scribed formed part of a dynamic environment

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where aquatic systems supporting subaquatic vegetation
changed rapidly both geographically and temporarily on
the ancient east coast of northeastern Mexico. However,
insects were able to live in humid areas with high mean
temperature and were able to interact with plants, as sug-
gested by galleries with insect coprolites reported in sev-
eral fruit types of this formation (Rodríguez de la Rosa &
Cevallos-Ferriz 1994). Further studies on plant-animal in-
teractions are promising.

This is the first report of terrestrial arthropods from this

unit and contributes to the understanding of the paleo-
ecology of this interesting formation.

The specimens are deposited in the Colección Nacional

de Paleontología, Instituto de Geología, Universidad Na-
cional Autónoma de México, under acronyms IGM.

Systematic paleontology

Order  Araneida Clerck, 1757

?Suborder  Opisthothelae Pocock, 1892

Infraorder incertae sedis (Fig. 4)

M a t e r i a l :

 IGM 8825; part and counterpart of com-

plete specimen; Cerro del Pueblo Formation, Coahuila,
Mexico. Campanian.

D e s c r i p t i o n :

 Body small  (Table 1).  Two halves of

the type preserved ventrally, ovate form. Prosoma suboval,
coxosternal region with wide, low sternum, unsegmented,
subcircular opisthosoma: sternum oval, longer than wide,
length about four-tenths length of body, width half of its
length. Left pedipalp coxa and first three left leg coxae sub-
circular, almost as wide as long. Fourth left leg coxa small,
half the length of third left leg coxa, three-quarters its
width. Impressions of the second left leg femur, and of the
right leg femur present; articulation between left pedipalp
trochanter and its femur preserved. Trochanter rectangular,

Fig. 3. Paleogeographic reconstruction for northeastern Mexico during
Campanian times, showing probable location of Parras Basin (PB).

broader than long, length seven-tenths its width. Portion of
pedipalp femur much longer than wide, length four times its
width. Portion of first leg femur longer than wide, length
about twice its half. Portion of second left leg femur, more
or less complete, much longer than wide, length more than
three times its width.

Impression of the right pedipalp femur is observed at the

front of the most anterior region of the prosoma, as a result
of deformation during fossilization. Right pedipalp femur
stout, longer than wide, length about twice its width.

Opisthosoma subcircular, almost as long as wide, length

about half of total length of body. Its width eight-tenths
maximum width (prosoma width).

Abdominal segments difficult to distinguish. Pedicel

partially visible between the fourth coxae.

Table 1: Measurements of the specimen IGM 8825.

Fig. 4. SEM of a spider IGM 8825. 1 – Sternum; 2 – Right pe-
dipalp femur; 3 – Right leg femur; 4 – First left pedipalp coxa;
5 – First left leg coxa; 6 – Second left leg coxa; 7 – Third left
leg coxa; 8 – Fourth left leg coxa; 9 – Left pedipalp trochanter;
10 – Left pedipalp femur; 11  – First left leg femur; 12  – Sec-
ond left leg femur; 13 – Pedicel.

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R e m a r k s :

 The specimen could not be a mesothelae, be-

cause of a wide sternum (instead of a narrow one – Raven
1985), it lacks the sternite of the first abdominal segment,
and the fourth coxae are not invaginated at their postero-
median corners (Platnick & Gertsch 1976).

Other diagnostic characters like the spinnerets or the

chelicerae are not visible, preventing taxonomic place-
ment at the infraorder level. However, mygalomorph char-
acteristics (Selden 2002), such as relatively robust
podomeres are visible in the specimen. Nevertheless, this
placement also appears questionable (K. Eskov, pers.
comm.), since pedipald is clearly shorter than legs, while
mygalomorph pedipalp is long and leg-like. Also pedi-
palp coxae are subcircular, while in mygalomorphs they
are more or less rectangular.

Order  Odonata Fabricius, 1793

Suborder ?Anisoptera Sélys, 1854 in Sélys & Hagen 1854

gen. et sp. incertae sedis (Fig. 5)

M a t e r i a l : 

IGM 8826; single fragment of fore wing.

Cerro del Pueblo Formation, Coahuila, Mexico. Campa-

D e s c r i p t i o n :

 The convexity and concavity of the

wing veins, as well as the intercalary veins apparent. Post-
nodal crossveins present; pterostigma well developed,
length four times its width, about two-tenths total frag-
ment length, width one-tenth maximum width, parallel
ending; four crossveins beneath.

RA, RP1, IR1, RP2, IR2, RP3—4, MA present. RA, RP1

parallel. RP2 and IR2 nearly parallel with two rows of
cells beginning halfway along pterostigma. RP2 arching
anteriorly just before level of pterostigma, then abruptly

bent; close and parallel to IR1. IR2 and RP3—4 strongly
divergent with many rows of cells between them distally.
RP 3—4 and MA sigmoidally curved with one row of cells
between them.

M e a s u r e m e n t s :

 Fragment length/width 13.7/6.8 mm.

Pterostigma  length/width: 2.4/0.6 mm.

R e m a r k s :

 Systematics of fossil Odonata is based on

the structure of adult wings. From the six odonate subor-
ders, there are only three which have Cretaceous representa-
tives: Anisozygoptera, Anisoptera and Zygoptera (Carpenter

The following features in the wing fragment are diagnos-

tic of the Odonata: distinctive complex venation, a con-
spicuous pterostigma on the anterior margin of the wing
distally; convexity and concavity of the main wing veins.

Although additional taxonomically relevant venational

characters are absent, a well developed pterostigma is
present, as well as the typical venational pattern of
Anisoptera i.e., RP with three main branches (Rieck &
Kukalová-Peck 1984; Carpenter 1992). Nevertheless, ac-
cording to D. Vasilenko (pers. comm.), a similar venation
of wing apex can be found in some Anisozygoptera, e.g.,
in the Late Jurassic Turanothemis  (Turanothemistidae) de-
scribed by Pritykina (1968).

Order  Blattaria Latreille, 1810

Suborder  Polyphagoidea Walker, 1868

Family  Blattulidae Vishniakova, 1982

Xonpepetla  Cifuentes-Ruiz et Vršanský, gen. nov.

T y p e   s p e c i e s : Xonpepetla rinconensis 

described be-


C o m p o s i t i o n :

 Type species only.

D i a g n o s i s : 

Robust cockroach with short and very

wide forewings (autapomorphies). Venation regular, with
the exception of area between CuA and CuP; subcostal
area narrow and short (autapomorphy); radial field wide
(plesiomorphy) with most veins simple (apomorphy); CuA
reduced to several veins (apomorphy). Clavus narrow and
long (autapomorphy), reaching almost half of the wing.

D e s c r i p t i o n :

 Forewing without coloration, short and

very wide, venation simplified with rather thick veins. Sub-
costa simple, costal area narrow and short; most of R sim-
ple; M rich (plesiomorphy), CuA with few branches. Clavus
narrow and long with sharphly curved CuP. A simple.

R e m a r k s : 

The new genus is highly advanced as

shown by numerous autapomorphies. This make its phylo-
genetic position rather unclear. On the other hand, plesio-
morphies exclude the relationship of the genus to other
advanced blattulids such as Tarakanula Vršanský, 2003
or Laurasian representatives of the genus Elisama.

Therefore the most probable ancestor of the new genus

is close to the Gondwanian representatives of Elisama
such as E. americana Vršanský, 2002 which share the
wide R, simplified venation (synapomorhy) and rather
thick veins. Thus, the absence of a dark macula near the
CuA basis may be considered for an apomorphy (unless
absent in E. americana).

E t y m o l o g y : 

After xonpepetl (Aztec for cockroach).

Fig. 5. Dragonfly IGM 8826. 1 – a forewing; 2 – a forewing.

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Xonpepetla rinconensis Cifuentes-Ruiz et Vršanský,

gen. et sp. nov. (Figs. 6—7)

H o l o t y p e :

 IGM 8827. both forewings. Cerro del Pueb-

lo Formation, Coahuila, Mexico. Campanian.

Additional material: IGM 8828. Hindleg. The same lo-

cality and horizon as the type.


Forewing wide, length/width: 9.3/3.6 mm.

Total number of veins at the margin about 40, with intercalar-
ies present between all branches including A. Costal space
short and narrow taking up less than a third of the wing

length. Sc short, simple and straight (slight asymmetry is
present in the only known pair of tegmina); R with 18
mostly simple veins; M9; CuA7, A5. CuP sharphly
curved, running close to CuA. Without coloration.

Additional material is represented by an adult hindleg,

part and counterpart, with preserved coxa, trochanter, fe-
mur and tibia; tarsus incomplete. Femur robust but not
elongated, with a spine on anterior margin of distal por-
tion. Tibia and tarsus with numerous spines. Coxa two-
tenths total leg length. Trochanter quadrangular, shorter
than coxa, its length one-twentieth total length. Its width
half maximum width (femur width).

Femur longer than coxa and trochanter, shorter than tib-

ia and tarsus, about three-tenths total length, widest to-
ward the middle; curved spine on the apex. Spine length
same as trochanter length, two-tenths its width.

Tibia and tarsus fragment length half of total length,

their width one-tenth maximum width. Short slender erect
spines along the lateral margins. Their length, half of fe-
mur spine length. Coxa length 4.2 mm, trochanter 1 mm,
width 1.0 mm, femur length/width 5.7/2.0 mm. Femur
spine length/width 1.0/0.2 mm. Tibia-tarsus fragment
length/width 9.3/0.6 mm.

R e m a r k s :

 Long coxae and short, wide femora of the

leg are characteristic for the Blattulidae. This determina-
tion is supported by its size. According to the relict char-
acter of the family in the Campanian, and a similar size of
the leg, it is most likely that the extremity fragment be-
longs to the same taxon. The presence of the two sister
species in the advanced Campanian cenoses seems unlike-
ly. Two finds representing the same taxon may be caused
by stochastical reasons but also it may indicate a compara-
tive abundance of the species and thus its near-water oc-
currence, and/or destabilized cenosis.

Only slight asymmetry of the wing indicate the individ-

ual was a good flier.

E t y m o l o g y :

 The specific name is based on Rincón Col-

orado, a regionally famous dinosaur-bearing locality in


There are few records of Cretaceous spiders – five Me-

sozoic mygalomorphs have been described by Selden
(2002), who highlights the records of Aranae from this pe-
riod and includes fossils from the Barremian or Aptian
strata of Koonwarra in South Australia (Jell & Duncan
1986), orbicularian araneomorphs from the Berriasian or
Valanginian deposits of the Sierra del Montsec in Spain
(Selden 1989, 1990, 1991); an unnamed lycosoid from
Orapa in Botswana (Upper Cretaceous – Rayner & Dip-
penaar-Schoeman 1995), and many new specimens are re-
ported from the Aptian or Albian Crato  Formation of
Brazil (Grimaldi 1991). After the description of Atocatle
ranulfoi  Feldmann, Vega, Applegate et Bishop, 1998, a
mesothelae species from the Albian Tlayúa Formation
(Feldmann et al. 1998),  the current find is the second old-
est spider reported from Mexico.

Fig. 6.  Xonpepetla rinconensis sp.nov. 1 – holotype IGM 8827,
dorsal view of both wings; 2 – the same.

Fig. 7. Hindleg, ?Xonpepetla rinconensis sp. nov. IGM 8828.

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Eskov & Zonshtein (1990) point out that orthognathous

chelicerae (present in mygalomophs and liphistiids) lying
on the same plane as the carapace cannot avoid being in
the same imprint during fossilization. So the imprint of a
spider containing the palps but not chelicerae, must surely
have belonged to a creature with labidognathous chelicer-
ae (present in araneomorphs). Chelicerae are not visible in
the specimen.

The infraorder Araneomorphae, sometimes referred to as

“true” spiders, includes some 90 families, 2700 genera,
and 32,000 species described (Coddington & Levi 1991).
Habitats within this group are highly variable, and include
vegetation, as well as soil-inhabiting, lapidicolous spiders
(Lehtinen 1967).

Anisoptera consists of five families with Cretaceous rep-

resentatives: Gomphidae, Aeshnidae, Aeschnidiidae, Peta-
luridae and Hemeroscopidae (Carpenter 1992). The
absence of a brace vein, the large area between veins IR2
and RP3-4, and the general venational pattern (i.e. moder-
ate wing reticulation, and longitudinal veins configura-
tion), could point to a rather recent group within the
Libelluloidea (Jarzembowski & Nel 1996), although this
lineage is present from the Middle Jurassic (Rasnitsyn &
Pritykina 2002).

The occurrence of cockroaches in a new Campanian lo-

cality is not surprising. The cockroaches represent domi-
nant elements of Cretaceous cenoses, including over 200
species in 8 families (Vršanský 1997, 1998a,b, 1999a,b,
2000, 2002, 2003a,b, 2004; Vršanský et al. 2002a). Local-
ities from the American continent are characterized by low
diversity. Several hundred Gondwanian cockroaches from
the Aptian or Albian Santana Formation comprise only 4
species in 3 families (Vršanský 2004), and in the Turonian
sediments of New Jersey, there are 4 species of 4 families
(P. Vršanský, in preparation). Nevertheless, in both locali-
ties, modern families dominate.

The dominant occurrence (2/2) of the Jurassic—Creta-

ceous family Blattulidae in the Campanian assemblages of
Mexico, which is the latest known record of the family, is
more surprising. Additionally, the newly described genus
and species possess many plesiomorphies within the fami-
ly, indicating some degree of isolation of the assemblage.

The family Blattulidae has been designated by Vishnia-

kova (1982) in order to separate distinct representatives
formerly placed in Mesoblattinidae (currently Caloblat-
tinidae Vršanský & Ansorge in Vršanský 2000). The fami-
ly had evolved from predecessors of Liberiblattinidae
Vršanský, 2002 during the latest Triassic or earliest Juras-
sic (Vršanský 2002) and representatives of the Blattulidae
are common in sediments but rare in resins, which might
indicate its open habitats close to water.

The derivation of the new genus and species from the

American taxa such as E. americana Vršanský, 2002  from
the Aptian or Albian sediments of Brazil, rather than from
the more advanced Turonian blattulids from Laurasia
might indicate absence of advanced Blattulidae in the
north Gondwana. Additionally, the Campanian find is also
the latest record of the family Blattulidae. The family also
occurs in other localities of Late Cretaceous age, but all of

them are represented by advanced taxa lacking strong ple-
siomorphies, which is the case for Xonpepetla rinconensis
sp. nov.

Other things being the same, it is an evidence for adapt-

ability of the group (known from at least 100 species),
which was able to compete even with modern taxa up to the
Campanian. However, they did not pass through the K/T


– The latest record of the family Blattulidae is present-

ed from the Campanian strata of northeastern Mexico.

– Xonpepetla rinconensis Cifuentes et Vršanský sp.

nov. (Blattulidae) possessed a combination of numerous
autapomorphies and plesiomorphies, indicating that the
progressive representatives of the family, known from
much older deposits of Laurasia were possibly rare at the
assemblage of the Cerro del Pueblo Formation.

– The second oldest spider record from Mexico is

present in the Campanian strata of northeastern Mexico. It
is likely to represent an opistothelae araneomorph (the
oldest record from Mexico in such a case).


We thank Prof. Alexandr P. Rasnitsyn

(PIN, Moscow), Dr. Jozef Michalík (GlU SAV, Bratislava),
Dr. Maria del Carmen Perrilliat (IGl, UNAM, Mexico), Dr.
Kirill Eskov and Mgr. Dmitrij V. Vasilenko (PIN, Mos-
cow), M.C. César and G. Durán (IB, UNAM) for reviewing
the manuscript. Research of P.V. was partially supported
by the VEGA Project No. 6002, MVTS and Literary Fund.


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