Nonmarine turtles from the Aguja Formation (Late Cretaceous, Campanian) of Chihuahua, Mexico
Por:
Lopez-Conde, Oliver A., Chavarria-Arellano, Maria L., Montellano-Ballesteros, Marisol
Publicada:
1 oct 2020
Resumen:
Fragments of turtle shell are known from several Upper Cretaceous
formations in Mexico, including Corral de Enmedio and Packard Shale,
Sonora; Aguja and Cerro del Pueblo, Coahuila; San Carlos, Chihuahua; El
Gallo, Baja California; and Ocozocoautla, Chiapas. Turtles are important
members of Upper Cretaceous vertebrate assemblages throughout North
America and are considered a useful tool to define biogeographic
patterns. The Upper Cretaceous sedimentary rocks exposed in the Aguja
Formation record the final transgressive/regressive sequence of the
Western Interior Cretaceous Seaway and the subsequent transition from a
marine to terrestrial environment. The total area of outcrops is small
compared to correlative exposures of these strata elsewhere in North
America, in spite of this, numerous invertebrate and vertebrate fossils
have been collected. The Aguja Formation in Texas preserves one of the
southernmost well-studied Upper Cretaceous (Campanian) terrestrial
vertebrate faunas in North America; contrary to what happens with the
outcrops in northern Chihuahua, where the record of terrestrial
vertebrates is scarce and especially those related to Testudines.
Non-marine strata of the Aguja Formation do not appear to be present
farther south in Mexico, and this is the reason why the Aguja fauna is
relevant to documenting latitudinal variation in Campanian continental
faunal associations. In this paper, the richness of Upper Cretaceous
turtles collected from three localities within the Aguja Formation in
Chihuahua is reviewed. Six taxa are recognized based on shell fragments
with distinctive sculpture patterns: stem cryptodires, including cf.
Baenidae, c.f. Denazinemys nodosa and cf. Compsemys victa, and crown
group cryptodires including trionychians (trionchids and Basilemys sp.)
and a kinosternoid (cf. Yelmochelys rosarioae). With the recognition of
these taxa, new records are reported for the Aguja Formation (e.g. cf.
Yelmochelys rosarioae) and Mexico (e.g. c.f. Denazinemys nodosa). The
knowledge of Cretaceous turtle richness of the Aguja Formation and
Mexico is increased and confirms the proposal of the variability
richness along the North American localities. This latitudinal
variability suggests that at any time turtles would have had a
climatically controlled northern limit of distribution, and the richness
of turtles would have decreased as this limit was reached.
Filiaciones:
Lopez-Conde, Oliver A.:
Univ Nacl Autonoma Mexico, Inst Geol, Ciencias Biol, Circuito Invest S-N,Ciudad Univ, Ciudad De Mexico 04510, Mexico
Chavarria-Arellano, Maria L.:
Univ Nacl Autonoma Mexico, Fac Ciencias, Dept Biol Evolut, Ciudad De Mexico 04510, Mexico
Montellano-Ballesteros, Marisol:
Univ Nacl Autonoma Mexico, Inst Geol, Circuito Invest S-N,Ciudad Univ, Ciudad De Mexico 04510, Mexico
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