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Guanlong (tyrannosauroid) manual digit mobility + dinosaur egg strength

Ben Creisler

Two recent papers in Chinese:

YU Yi-Lun; SULLIVAN, Corwin; XU Xing (2015)
Acta Palaeontologica Sinica 2015 (2):


Guanlong is a basal tyrannosauroid theropod dinosaur from the upper
part of the Shishugou Formation of the Junggar Basin in the Xinjiang
region of northwest China,which is Late Jurassic in age (Xu et
al.,2006).In this study we evaluated the ranges of flexion and
extension at the various joints within the hand of Guanlong, based on
laser scans of the well-preserved left manus of the holotype specimen
(IVPP V14531).The scans were processed using Rapidform XOV2 to create
three-dimensional digital models of the metacarpals and
phalanges,which were then imported into Autodesk Maya and used to
construct an articulated model of the complete manus. A system of
hierarchically arranged joints was constructed in Maya in order to
allow precise three-dimensional positioning of the model, as in
scientific rotoscoping studies in which a model is used to duplicate
the recorded movements of a living animal (Gatesy et al.,2010).Ranges
of joint motion are difficult to estimate precisely in fossil taxa.In
the present study,we generated both "limited"and "extreme"estimates of
mobility for each joint within the manus, using explicit anatomical
criteria.Extreme flexion or extension was defined by the point at
which the palmar (for flexion) or dorsal (for extension) lip of the
proximal articular surface of the more distal bone involved in the
joint contacted the shaft of the more proximal bone,preventing further
rotation.Limited flexion or extension was defined by the point at
which the edges of the palmar or dorsal edges of the smooth articular
surfaces of the two bones were as closely congruent as possible.In
Maya,each joint was rotated in either direction until the criterion
for extreme flexion or extension was fulfilled,and the smaller angle
at which the criterion for limited flexion or extension was fulfilled
was also noted.Physical manipulation of the fossil bones was used to
guide manipulation of the Maya model,and to confirm the plausibility
of the results.Previous studies of joint mobility in theropod  and
(Galton,1971; Gishlick,2001; Senter, 2005, 2006 a,b; Senter and
Robins, 2005) have estimated ranges of flexion and extension based on
the boundaries of the opposing articular surfaces,using essentially
the same criterion we have adopted for our limited estimates.These
studies have recognized the potential for error in their results,often
emphasizing the possibility that soft tissues might restrict motion to
a slightly narrower range than that indicated by the articular surface
boundaries. By contrast, Mallison’s (2010) illustrations of the manus
of the basal sauropodomorph Plateosaurus in flexed and extended
postures suggest that he followed an approach closer to our protocol
for estimating extreme ranges of motion,allowing rotation well beyond
joint surface boundaries.Our limited and extreme values for flexion
and extension represent somewhat conservative and very liberal
estimates of the range of motion,respectively,and it is likely that
the true endpoints of flexion and extension for each joint would have
lain between our limited and extreme estimates.For most joints the
extreme and limited values were rather far apart,the discrepancy
averaging 23°in the case of flexion and 39°in the case of
extension(excluding a joint whose geometry made the extreme criterion
difficult to apply for both flexion and extension).These large gaps
highlight the difficulty of precisely constraining ranges of joint
motion based on osteological criteria alone,and imply a need for
extensive data from living taxa regarding the relationship between
osteological features such as joint surface boundaries and actual
ranges of motion at manual joints.However,our limited values can serve
as the basis for some cautious comparisons to previous studies.The
manual joints of the allosauroid theropod Acrocanthosaurus (Senter and
Robins,2005)were almost uniformly capable of much greater extension
than those of the dromaeosaurid Deinonychus (Senter, 2006a),whereas
those of Deinonychus were generally capable of greater flexion. Our
results for limited flexion and extension indicate that the manual
joints of digits II and III in Guanlong were intermediate between
those of Acrocanthosaurus and Deinonychus with regard to the range of
extension,and varied widely but approximately within the range defined
by Acrocanthosaurus and Deinonychus with regard to flexion. Patterns
for digit IV were more distinctive:the metatarsophalangeal joint had
little mobility in either direction, the first interphalangeal (IP)
joint was even more biased towards extension than in
Acrocanthosaurus,the second IP joint was comparable in its mobility to
that of Acrocanthosaurus, and the third and final IP joint was
comparable to that of Deinonychus. Taken together,these results hint
at a rough trend towards greater capacity for manual flexion and
reduced capacity for manual extension on the line to paravian
theropods such as Deinonychus, but studies of many more taxa and
improved methods of estimating ranges of motion will be needed in
order to adequately test this possibility.

News story (in Chinese)



LI Ning; LI Bing; WANG Qiang; WANG Xiao-Lin (2015)
Acta Palaeontologica Sinica 2015 (2):

To find out the failure law of dinosaur eggs and its stability in
natural burial, the investigation into the three-dimensional stress
distribution of eggshells in the external force is a beneficial
method. ANSYS, large general-purpose finite element software,  makes
the investigation intuitive. The finite element models have been set
up separately for Ovaloolithus chinkangkouensis discovered in Laiyang,
Shandong Province, Macroolithus yaotunensis and Macroolithus rugustus
discovered in Nanhsiung, Guangdong Province, and a clutch of
undescribed elongatoolithids discovered in Ganzhou, Jiangxi Province.
The models were analogously computed for its threedimensional stress
distribution under 50 KPa evenly distributed load. In consequence, the
fine images of three-dimensional stress distribution in the external
force have been drawn. The results show the most vulnerable area is
between the diameters of blunt and sharp ends, and closer to the blunt
one. This conclusion is consistent with the failure law presented in
the referred specimens and the outlet position of dinosaur hatching
from the egg. The equivalent-stress difference between the diameters
of blunt and sharp ends is relative to the difference of the both
diameters. With the increment of the ratio of the equatorial radius to
shell thickness (R/h), the ability of the eggshells to fight the
external load decreases, resulting in vulnerable eggs.