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New Articles and Papers: Albertosaurus, azhdarchids, etc.



From: Ben Creisler bh480@scn.org

In case these items have not been mentioned yet:

Biology Letters 
Issue: FirstCite Early Online Publishing

Tyrannosaur ageing
Robert E. Ricklefs

Abstract: 
Rate of ageing in tyrannosaurs was calculated from parameters of Weibull
functions fitted to survival curves based on the estimated ages at death of
fossilized remains. Although tyrannosaurs are more closely related to birds
than to mammals, they apparently aged at rates similar to mammals of
comparable size. Rate of growth in body mass of tyrannosaurs was similar to
that of large mammals, and their rates of ageing were consistent with the
estimated extrinsic mortality, which is strongly correlated with the rate
of ageing across birds and mammals. Thus, tyrannosaurs appear to have had
life histories resembling present-day large terrestrial mammals. Rate of
ageing in warm-blooded vertebrates appears to be adjusted in response to
extrinsic mortality and potential lifespan, independently of both
physiological and developmental rates. However, individuals in species with
the slowest rates of ageing suffer the highest proportion of ageing-related
mortality, hence potentially strong selection to further postpone
senescence. Thus, the longest observed lifespans in birds, tyrannosaurs and
mammals might be close to the maximum possible.
..............
Geological Magazine
Advance publication

A re-evaluation of Chinshakiangosaurus chunghoensis Ye vide Dong 1992
(Dinosauria, Sauropodomorpha): implications for cranial evolution in basal
sauropod dinosaurs
PAUL UPCHURCH, PAUL M. BARRETT, ZHAO XIJIN and XU XING

Abstract
Re-description of the left dentary of Chinshakiangosaurus chunghoensis
reveals that it possesses an unusual combination of ?prosauropod? and
?sauropod? character states. Cladistic analysis places Chinshakiangosaurus
as one of the most basal sauropods known currently. Mapping of dentary and
dental characters onto the most parsimonious topologies yields insights
into the sequence of acquisition of a number of feeding-related characters.
For example, it seems that basal sauropodomorphs (traditional prosauropod
taxa) possessed a fleshy cheek that attached to the mandible along a marked
ridge, and that the same structure was present in the most basal sauropods.
The early sauropod skull developed a lateral plate that reinforced the
bases of the tooth crowns labially, and had wrinkled tooth enamel and a
concavity on the mesial portion of the lingual part of each crown, while
retaining a fleshy cheek and a relatively weak symphysis. More advanced
sauropods (eusauropods) lost the cheek, perhaps in order to increase the
gape of the jaws in response to a change in feeding style that involved
collection of larger quantities of poor quality foliage.
.................

Geological Journal
Advance online publication

The synonymy of the Late Cretaceous mosasaur (Squamata) genus Lakumasaurus
from Antarctica with Taniwhasaurus from New Zealand and its bearing upon
faunal similarity within the Weddellian Province 
James E. Martin, Marta Fernández 

Abstract
Novas et al. (2002. Ameghiniana 39:245-249) described and named a new
mosasaur as Lakumasaurus antarcticus from the Late Cretaceous marine
deposits of the Antarctic Peninsula. The specimen was recovered from the
late Campanian Santa Marta Formation on James Ross Island. A number of
characters indicate the affinities of Lakumasaurus with the Tylosaurinae.
However, other characters of Lakumasaurus are unusual among tylosaurines,
particularly the dentition bearing fine striae, teeth with non-serrated
anterior carinae, anterior teeth without posterior carinae, relatively
straight lateral margins on frontal and relatively small size.
Investigation of mosasaurs from New Zealand confirms that these characters
occur in the type specimen of Taniwhasaurus oweni Hector 1874, collected
from the late Campanian Conway Formation of Haumuri Bluff. Size and similar
morphological characters indicate the synonymy of Lakumasaurus with
Taniwhasaurus. The synonymy of Lakumasaurus with Taniwhasaurus adds
significantly to the evidence of endemism among marine reptiles in
Antarctica, New Zealand and Patagonia (Weddellian Province) during the Late
Cretaceous. Taniwhasaurus along with the possible co-occurrence of
Moanasaurus are the first mosasaurs at a generic level to indicate
Gondwanan endemism. The mosasaur evidence is complemented by the plesiosaur
Aristonectes, which occurs in the Maastrichtian of Argentina and Antarctica
and appears similar to Kaiwhekea from the Maastrichtian of New Zealand, and
by Mauisaurus, an elasmosaurid which occurs in the Maastrichtian of
Antarctica and medial Campanian-Maastrichtian of New Zealand. 
....................

Geology Today
Volume 23 Issue 1 Page 33 - January 2007 

Titans of the skies: azhdarchid pterosaurs
Mark Witton

Abstract
Pterosaurs, the flying reptiles of the Mesozoic, often play second fiddle
in popularity to their contemporaries, the dinosaurs. Such treatment
conceals the remarkable diversity and biology of this group: not only were
pterosaurs the first vertebrates to achieve powered flight, but they also
existed for 160 million years?longer than any other flying vertebrates.
Named after the Uzbek mythical dragon 'azhdarkho', the Azhdarchidae are
among the most enigmatic of all pterosaurs. As with most pterosaurs,
azhdarchid remains are rare, and their fossil record is largely represented
by isolated bones or incomplete skeletons. Despite the collection of
azhdarchid fossils over the last 100 years, recognition of these pterosaurs
as a distinct group was not achieved until relatively recently. It is now
clear that the azhdarchids were a highly successful group that probably
first appeared in the Early Cretaceous, gradually spreading across the
globe until the latest Cretaceous when they, as one of the last remaining
groups of pterosaurs, became extinct. Although most notable for achieving
wingspans comparable with light aircraft, other aspects of azhdarchid
morphology and ecology make them not just aberrant animals but also unusual
pterosaurs.



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