Estudo e descrição de uma nova icnoespécie de artrópode da formação Botucatu (jurássico superior — cretáceo inferior) da bacia do Paraná, Estado de São Paulo, Brasil
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Date
2017-04-10Author
Peixoto, Bernardo de Campos Pimenta e Marques
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Here we describe the new ichnospecies Lithographus araraquarensis isp. nov.. A
trackway composed by two rows, whose internal width between the rows is
less than 1/3 of the external width; with alternating to staggered series,
composed of three elliptical tracks that can vary from slightly elongated,
tapered or circular. The slabs were found in the Araraquara region, São Paulo
State, in the yellowish/reddish sandstones of the Botucatu Formation,
interpreted as a testimony of a gigantic aeolian depositional system, a sandsea
(erg), with an arid climate that developed during the Late Jurassic to Early
Cretaceous in the Center-South part of Gondwana. Through comparisons with
neoichnological studies and morphological deduction, the production of these
trackways is assigned to the pterygote insects, which have walked over the
unconsolidated sandy substrate. Lithographus araraquarensis isp. nov. was
probably produced by beetles that had a flexible diet and were part of the
fauna of detritivores omnivores that fed on biomass particles that accumulated
in the slipface of the dunes of the Botucatu paleodesert, being able to adopt
herbivorous and saprophagous diet when opportune. The description of this
new trackway amplifies the knowledge about the faunistic composition of the
Botucatu paleodesert and provides subsidies to better understand its
paleoenvironment and the ecological relations prevailing at the time. Probably,
the producer of Lithographus araraquarensis isp. nov., together with the
producers of Taenidium isp. and Skolithos linearis, ware a source of food for
primary consumers, represented by arachnids, such as scorpions and spiders,
and small mammaliforms. The above trophic level was constituted by theropod
dinosaurs of the group Coelurosauria and Carnosauria, and large
mammaliforms, which predated smaller theropods and dinosaurs of the
Ornithopoda group. Any new occurrences of Lithographus araraquarensis isp.
nov. in stratigraphic units of other localities, representing other times, should
be analyzed in the light of the ichnofacies model. The recurrence of
Lithographus araraquaraensis isp. nov. in aeolian units, and with differentiated
abundance in relation to non-aeolian units, could indicate an analogous
paleoenvironment to the Botucatu Formation, that is, an arid desert. Both the
confirmation and the refutation of recurrence would enrich the theoretical
framework of the invertebrate ichnofacies Octopodichnus-Entradichnus for
eolian environment.