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Modeling sauropod tracks + Early Cretaceous vertebrates from Guangxi, China

Ben Creisler

New online papers:

Eugenio Sanz, Antonio Arcos, Carlos Pascual, and Ignacio Menendez Pidal (2015)
Three-dimensional elasto-plastic soil modelling and analysis of sauropod tracks.
Acta Palaeontologica Polonica (in press)

This paper reports the use of FEA to model dinosaur tracks.
Satisfactory reproductions of sauropod ichnites were simulated using
3D numerical models of the elasto-plastic behaviour of soils. Though
the modelling was done of ichnites in situ at the Miraflores I
tracksite (Soria, Spain), the methodology could be applied to other
tracksites to improve their ichnological interpretation and better
understand how the type and state of the trodden sediment at the
moment the track is created is a fundamental determinant of the
morphology of the ichnite. The results obtained explain why the
initial and commonly adopted hypothesis—that soft sediments become
progressively more rigid and resistant at depth—is not appropriate at
this tracksite. We explain why it is essential to consider a more
rigid superficial layer (caused by desiccation) overlying a softer
layer that is extruded to form a displacement rim. Adult sauropods
left trackways behind them. These tracks could be filled up with water
due to phreatic level was close to the ground surface. The simulation
provides us with a means to explain the differences between similar
tracks (of different depths; with or without displacement rims) in the
various stratigraphic levels of the tracksite and to explain why
temporary and variable conditions of humidity lead to these
differences in the tracks. The simulations also demonstrate that track
depth alone is insufficient to differentiate true tracks from
undertracks and that other discrimination criteria need to be taken
into account. The scarcity of baby sauropod tracks is explained
because they are shallow and easily eroded.


Early Cretaceous vertebrates from the Xinlong Formation of Guangxi
(southern China): a review.
Geological Magazine (advance online publication)
DOI: http://dx.doi.org/10.1017/S0016756815000394

The vertebrate assemblage from the Early Cretaceous non-marine Xinlong
Formation of the Napai Basin, in the south-western part of Guangxi
Zhuang Autonomous Region (southern China), is reviewed. The assemblage
includes chondrichthyans (at least six species of hybodont sharks
including Hybodus, Thaiodus, Heteroptychodus and Acrorhizodus),
actinopterygians (Halecomorphi and Ginglymodi), turtles (the adocid
Shachemys and the carettochelyid Kizylkumemys), crocodilians (cf.
Theriosuchus) and dinosaurs (the sauropods Fusuisaurus and
Liubangosaurus, carcharodontosaurid and spinosaurid theropods,
iguanodontians and a possible psittacosaurid). This assemblage shows
many similarities to those from non-marine formations of the Khorat
Group of north-eastern Thailand. It seems to be particularly close to
that from the Khok Kruat Formation, considered as Aptian in age, as
shown especially by sharks and turtles and by the presence of
iguanodontians. An Aptian age is therefore proposed for the Xinlong
Formation. A study of the stable oxygen and carbon isotope
compositions of reptile apatite suggests that this part of South China
experienced subtropical arid conditions during the deposition of the
Xinlong Formation. In its composition, the vertebrate fauna from the
Xinlong Formation seems to be more similar to coeval faunas from SE
Asia than to assemblages from northern China (including the Jehol
Biota). Although this may partly reflect different depositional and
taphonomic environments (fluvial for the Xinlong Formation versus
lacustrine for the Jehol Biota) it seems likely that, during Early
Cretaceous time, southern China and SE Asia were part of a distinct
zoogeographical province, different from that corresponding to
northern China. This may be the result of both climatic differences
(with relatively cool climates in northern China versus a subtropical
climate in the south) and geographical barriers such as mountain