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Lufengosaurus(?) (sauropodomorph) embryos from Early Jurassic of China show rapid growth

From: Ben Creisler

A new paper in Nature;

Robert R. Reisz, Timothy D. Huang, Eric M. Roberts, ShinRung Peng,
Corwin Sullivan, Koen Stein, Aaron R. H. LeBlanc, DarBin Shieh,
RongSeng Chang, ChengCheng Chiang, Chuanwei Yang & Shiming Zhong
Embryology of Early Jurassic dinosaur from China with evidence of
preserved organic remains.
Nature 496: 210–214 (11 April 2013)

Fossil dinosaur embryos are surprisingly rare, being almost entirely
restricted to Upper Cretaceous strata that record the late stages of
non-avian dinosaur evolution. Notable exceptions are the oldest known
embryos from the Early Jurassic South African sauropodomorph
Massospondylus and Late Jurassic embryos of a theropod from Portugal.
The fact that dinosaur embryos are rare and typically enclosed in
eggshells limits their availability for tissue and cellular level
investigations of development. Consequently, little is known about
growth patterns in dinosaur embryos, even though post-hatching
ontogeny has been studied in several taxa. Here we report the
discovery of an embryonic dinosaur bone bed from the Lower Jurassic of
China, the oldest such occurrence in the fossil record. The embryos
are similar in geological age to those of Massospondylus and are also
assignable to a sauropodomorph dinosaur, probably Lufengosaurus. The
preservation of numerous disarticulated skeletal elements and
eggshells in this monotaxic bone bed, representing different stages of
incubation and therefore derived from different nests, provides
opportunities for new investigations of dinosaur embryology in a clade
noted for gigantism. For example, comparisons among embryonic femora
of different sizes and developmental stages reveal a consistently
rapid rate of growth throughout development, possibly indicating that
short incubation times were characteristic of sauropodomorphs. In
addition, asymmetric radial growth of the femoral shaft and rapid
expansion of the fourth trochanter suggest that embryonic muscle
activation played an important role in the pre-hatching ontogeny of
these dinosaurs. This discovery also provides the oldest evidence of
in situ preservation of complex organic remains in a terrestrial

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