Raiders of the New Papers

["Jerry D. Harris" <jharris@dixie.edu>]

A few new tidbits; though readers of some of the paleo-oriented blogs will 
have already seen a couple of these, I don't think they've been mentioned 
here yet...

Humphries, S., Bonser, R.H.C., Witton, M.P., and Martill, D.M. 2007. Did 
pterosaurs feed by skimming? Physical modelling and anatomical evaluation of 
an unusual feeding method. PLoS Biology 5(8):e204. doi: 
10.7371/journal.pbio.0050204.

ABSTRACT: Just because a component of an extinct animal resembles that of a 
living one does not necessarily imply that both were used for the same task. 
The lifestyles of pterosaurs, long-extinct flying reptiles that soared 
ancient skies above the dinosaurs, have long been the subject of debate 
among palaeontologists. Similarities between the skulls of living birds 
(black skimmers) that feed by skimming the water surface with their lower 
bill to catch small fish, and those of some pterosaurs have been used to 
argue that these ancient reptiles also fed in this way. We have addressed 
this question by measuring the drag experienced by model bird bills and 
pterosaur jaws and estimating how the energetic cost of feeding in this way 
would affect their ability to fly. Interestingly, we found that the costs of 
flight while feeding are considerably higher for black skimmers than 
previously thought, and that feeding in this way would be excessively costly 
for the majority of pterosaurs. We also examined pterosaur skulls for 
specialised skimming adaptations like those seen in modern skimmers, but 
found that pterosaurs have few suitable adaptations for this lifestyle. Our 
results counter the idea that some pterosaurs commonly used skimming as a 
foraging method and illustrate the pitfalls involved in extrapolating from 
living to extinct forms using only their morphology.


Erickson, G.M., Rogers, K.C., Varricchio, D.J., Norell, M.A., and Xu, X. 
2007. Growth patterns in brooding dinosaurs reveals the timing of sexual 
maturity in non-avian dinosaurs and genesis of the avian condition. Biology 
Letters. doi: 10.1098/rsbl.2007.0254.

ABSTRACT: The timing of sexual maturation in non-avian dinosaurs is not 
known. In extant squamates and crocodilians it occurs in conjunction with 
the initial slowing of growth rates as adult size is approached. In birds 
(living dinosaurs) on the other hand, reproductive activity begins well 
after somatic maturity. Here we used growth line counts and spacing in all 
of the known brooding non-avian dinosaurs to determine the stages of 
development when they perished. It was revealed that sexual maturation 
occurred well before full adult size was reached-the primitive reptilian 
condition. In this sense, the life history and physiology of non-avian 
dinosaurs was not like that of modern birds. Palaeobiological ramifications 
of these findings include the potential to deduce reproductive lifespan, 
fecundity and reproductive population sizes in non-avian dinosaurs, as well 
as aid in the identification of secondary sexual characteristics.



Roopnarine, P.D., Angielczyk, K.D., Wang, S.C., and Hertog, R. 2007. Trophic 
network models explain instability of Early Triassic terrestrial 
communities. Proceedings of the Royal Society of London B 274:2077-2086. 
doi: 10.1098/rspb.2007.0515.

ABSTRACT: Studies of the end-Permian mass extinction have emphasized 
potential abiotic causes and their direct biotic effects. Less attention has 
been devoted to secondary extinctions resulting from ecological crises and 
the effect of community structure on such extinctions. Here we use a trophic 
network model that combines topological and dynamic approaches to simulate 
disruptions of primary productivity in palaeocommunities. We apply the model 
to Permian and Triassic communities of the Karoo Basin, South Africa, and 
show that while Permian communities bear no evidence of being especially 
susceptible to extinction, Early Triassic communities appear to have been 
inherently less stable. Much of the instability results from the faster 
post-extinction diversification of amphibian guilds relative to amniotes. 
The resulting communities differed fundamentally in structure from their 
Permian predecessors. Additionally, our results imply that changing 
community structures over time may explain long-term trends like declining 
rates of Phanerozoic background extinction.


Mustoe, G.E. 2007. Coevolution of cycads and dinosaurs. The Cycad Newsletter 
30(1):6-9.

INTRODUCTION: Cycads were a major component of forests during the Mesozoic 
Era, their shade of their fronds falling upon the scaly backs of multitudes 
of dinosaurs that roamed the land. Paleontologists have long postulated that 
cycad foliage provided an important food source for reptilian herbivores, 
but the extinction of dinosaurs and the contemporaneous precipitous decline 
in cycad populations at the close of the Cretaceous have generally been 
assumed to have resulted from different causes. Ecologic effects triggered 
by a cosmic impact are a widely-accepted explanation for dinosaur 
extinction; cycads are presumed to have suffered because of their inability 
to compete with fast-growing flowering plants that appeared during the 
mid-Cretaceous "angiosperm explosion." This paper explores a different 
hypothesis, i.e., that the evolutionary fates of cycads and dinosaurs were 
inextricably intertwined, and the Late Cretaceous extinction of theese 
reptiles was the triggering event that cuased cycads to diminish to their 
present status as "living fossils." The main tenet of this hypothesis is 
cycads depdended on herbivorous dinosaurs to disperse their seeds, and the 
disappearance of these herbivores led to a precipitous decline in the 
geographic range and numerical abundance of cycads. Evidence comes from the 
toxicology of extant cycads, their seed dispersal strategies, anatomical 
characteristics of herbivorous dinosaurs, and the geographic distribution 
and taxonomic diversity of modern and fossil cycads.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

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