[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Dinosaurs and Mesozoic mammals from Mexico + Bauru Group vertebrates + Desmatochelys (free pdfs)



Ben Creisler
bcreisler@gmail.com


A number of recent open access papers for the Mesozoic in Latin America:



A. A. Ramírez-Velasco & R. Hernández-Rivera (2015)
Diversity of Late Cretaceous dinosaurs from Mexico.
Boletín Geológico y Minero, 126 (1): 63-108
http://www.igme.es/boletin/2015/126_1/8-Articulo%204.pdf


For many years the diversity of dinosaurs of Mexico during the Late
Cretaceous has been poorly understood. This is due to the limited
taxonomical determinations and the abundant undescribed material. This
paper presents a new review of the up-to-date osteological record of
Late Cretaceous dinosaurs from Mexico, based on published papers,
unpublished data and direct observation of the material housed in
Mexican paleontological collections and in the field. Some diagnostic
dinosaur bones were taxonomically reassigned and others reported in
the literature were located in collections. We document new localities
with dinosaur remains in Fronteras Sonora, Manuel Benavides and
Jiménez Chihuahua, General Cepeda and Saltillo Coahuila. Additionally
we report new material relating to tyrannosaurids, ornithomimids,
ankylosaurs, ceratopsids and hadrosaurids which extends their
geographic and temporal distribution in Mexico. This investigation has
revealed a dinosaur faunal assemblage consistent with others studies
of North American Late Cretaceous faunas, abundant large bodied
dinosaurs and poorly represented small dinosaurs. The lack of
oviraptorosaurs, lepoceratopsids and thescelosaurids suggests the need
to develop new method in the search for small dinosaurs in order to
gain a more complete picture of dinosaur communities in Mexico and
North America during the Late Cretaceous.


===



M. Montellano Ballesteros (2015)
Síntesis sobre el registro fósil de los mamíferos mesozoicos
mexicanos. [Overview of the fossil record of the Mexican Mesozoic
mammals]
Boletín Geológico y Minero, 126 (1): 7-20
http://www.igme.es/boletin/2015/126_1/5-Articulo%201.pdf



The Mesozoic mammal fossil record in Mexico is poor, but it spans from
the Jurassic to the Cretaceous, and is diverse in its forms. For many
years, the only Mesozoic mammalian record was that from the Campanian
El Gallo Formation, in Baja California. The described mammals included
Mesodma sp. cf. M. formosa, ?Stygimys sp., Pediomys sp. and
Gallolestes pachymandibularis. In 2004 paleontological field work was
taken up again with the objective of collecting microvertebrates. The
fossil mammal remains are rare; but there is the important discovery
of a skull and a complete lower jaw of the multituberculate Cimolodon.
The faunal association is peculiar; it may be due to the age of the
fauna and its geographic position. In the Jurassic outcrops of the La
Boca Formation, in the Huizachal Canyon, Tamaulipas, remains of
mammaliaforms and the tritylodontid Bocatherium mexicanum were
recovered. Bocaconodon tamaulipensis is a mammaliform of
morganucodont-grade; Victoriaconodon inaequalis, a primitive
triconodontid and Huasteconodon wiblei, a ?gobiconodontid triconodont.
The diversity of forms suggests that at the end of the Early Jurassic
several mammaliaform taxa with variations in the dental pattern and in
the lower jaw morphology existed. The Huizachal fauna is composed of
more derived mammaliaforms than those present during the Late Triassic
and Early Jurassic and more primitive than those present in the middle
Jurassic. In the Campanian Cerro del Pueblo Formation, in Coahuila,
the presence of multituberculates and marsupials: Turgidodon sp. cf.
T. russelli, Pediomys sp., cf. P. elegans is registered.


=====

A. G. Martinelli  & V. P. A. Teixeira. 129-158
The Late Cretaceous vertebrate record from the Bauru Group in the
Triângulo Mineiro, southeastern Brazil.
Boletín Geológico y Minero, 126 (1): 129-158
http://www.igme.es/boletin/2015/126_1/10-Articulo%206.pdf


We summarize here the Late Cretaceous vertebrate record of the
Triângulo Mineiro (western portion of the Minas Gerais State,
southeastern Brazil). All the specimens come from the Bauru Group
(Bauru Basin) from the Adamantina (Campanian), Uberaba (Campanian) and
Marília (Maastrichtian) formations. Vertebrate-bearing sites are
distributed throughout the Triângulo Mineiro, but the Uberaba County
has the largest diversity of Late Cretaceous vertebrate from the Bauru
Group, mainly concentrated in the Serra da Galga Member of the Marília
Formation. So far, the following taxa have been recognized in the
Triângulo Mineiro, from the Adamantina Formation: Amiiformes indet.,
cf. Atractosteus sp. (Lepisosteiformes), Mesoeucrocodylia indet.,
Sphagesaurus sp. (Sphagesauridae), Campinasuchus dinizi and
Pissarrachampsa sera (Baurusuchidae), Maxakalisaurus topai
(Titanosauria), Titanosauria indet., and Abelisauridae indet.; from
the Uberaba Formation: Titanosauria indet. and Megaraptora indet.;
from the Marília Formation: Ceratodus sp. (Dipnoi), Vidalamiine indet.
(Amiiformes), Lepisosteiformes indet., Siluriformes indet.,
Characiformes indet., Perciformes indet., Baurubatrachus pricei and
Uberabatrachus carvalhoi (Neobatrachia), Cambaremys langertoni,
Peiropemys mezzalirai and Pricemys caiera (Podocnemididae) and
Podocnemididae indet., Pristiguana brasiliensis (Iguania), Itasuchus
jesuinoi (Trematochampsidae), Labidiosuchus amicum (Notosuchia),
Peirosaurus torminni and Uberabasuchus terrificus (Peirosauridae),
Trigonosaurus pricei, Baurutitan brittoi, Uberabatitan ribeiroi,
Aeolosaurini indet. (Titanosauria), Abelisauroidea indet.,
Abelisauridae indet., cf. Carcharodontosauridae indet., Maniraptora
indet., Avialae indet., and Enantiornithes indet. The Triângulo
Mineiro region has a great paleontological potential which will
generate future results amplifying the diversity and knowledge of the
Late Cretaceous vertebrates of Brazil.


===



Edwin A. Cadena & James F. Parham (2015)
Oldest known marine turtle? A new protostegid from the Lower
Cretaceous of Colombia.
PaleoBios 32:1–42
32. ucmp_paleobios_28615
http://escholarship.org/uc/item/147611bv



Recent studies suggested that many fossil marine turtles might not be
closely related to extant marine turtles (Chelonioidea). The
uncertainty surrounding the origin and phylogenetic position of fossil
marine turtles impacts our understanding of turtle evolution and
complicates our attempts to develop and justify fossil calibrations
for molecular divergence dating. Here we present the description and
phylogenetic analysis of a new fossil marine turtle from the Lower
Cretaceous (upper Barremian-lower Aptian, >120 Ma) of Colombia that
has a minimum age that is >25 million years older than the minimum age
of the previously recognized oldest chelonioid. This new fossil taxon,
Desmatochelys padillai sp. nov., is represented by a nearly complete
skeleton, four additional skulls with articulated lower jaws, and two
partial shells. The description of this new taxon provides an
excellent opportunity to explore unresolved questions about the
antiquity and content of Chelonioidea. We present an updated global
character-taxon matrix that includes D. padillai and marine turtles
known from relatively complete specimens. Our analysis supports D.
padillai as sister taxon of D. lowi within Protostegidae, and places
protostegids as the sister to Pan-Dermochelys within Chelonioidea.
However, this hypothesis is complicated by discrepancies in the
stratigraphic appearance of lineages as well as necessarily
complicated biogeographic scenarios, so we consider the phylogeny of
fossil marine turtles to be unresolved and do not recommend using D.
padillai as a fossil calibration for Chelonioidea. We also explore the
definition of “marine turtle,” as applied to fossil taxa, in light of
many littoral or partially marine-adapted fossil and extant lineages.
We conclude that whereas the term “oldest marine turtle” depends very
much on the concept of the term being applied, we can confidently say
that D. padillai is the oldest, definitive, fully marine turtle known
to date.

===


A. Arcucci, M. Beatriz Prámparo, L. Codorniú, G. Giordano, G.
Castillo-Elías, G. Puebla, N. Mego, M. A. Gómez  & E. Bustos-Escalona
(2015)
Biotic assemblages from Early Cretaceous lacustrine systems in the San
Luis Basin, mid-western Argentina.
Boletín Geológico y Minero, 126 (1): 109-128
http://www.igme.es/boletin/2015/126_1/9-Articulo%205.pdf



Significant paleobiological data has emerged from the San Luis Basin
(Early Cretaceous, Aptian-Albian in Central Argentina) during the last
decades. Two units in this basin include lake paleo-environments with
important fossil contents in an excellent state of preservation that
could be considered as Konservat Lagerstätten deposits. The
association of fossil leaves and pollen grains from the La Cantera
Formation is one of the most ancient and complete angiosperm records
in South America and the bryophyte association of the same unit
constitutes one the most complete records of its type in Argentina.
Insects from five different orders have been identified in this
association, and three endemic species of aquatic insects from the La
Cantera Formation have been described as belonging to the Notonectidae
and Corixidae families, including the oldest member of the Anisopinae
subfamily. The Pterodaustro guinazui association from the Lagarcito
Formation is one of the few fossil associations recorded worldwide
from which it is possible to make studies on the life history
parameters of pterosaurs-like growth patterns and ontogeny. The
Pleuropholid fish from the Lagarcito Formation are the only record of
this group in Argentina and the second in South America. Several new
species of ostracods and conchostracea have also been recorded from
the same units. Despite the amount of paleontological information now
available from the San Luis basin, much work remains to be done on
these fossil associations and the interpretation of their depositional
environments.