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RE: Jehol Biota food-web models + Middle Jurassic Daohugou plants + more papers
Maybe I'm missing something, but the number of specimens listed for each taxon
is WAY off, as listed in their Table 5. For example, the specimen count for
Caudipteryx sp. is listed as 2, but 6 have been published. Ironically, they
would have to know of at least 3 specimens, since the use of 'sp.' instead of
zoui in their table indicates multiple species were being counted, and there
were 2 C. zoui specimens published in the original description before C.
dongi's specimen was published. Similarly, Dilong's specimen count is listed
as 1, even though four specimens were described in the original paper.
Beipiaosaurus- 1 listed instead of 2, Huaxiagnathus 1 instead of 2, Mei 1
instead of 2, Sinornithosaurus 2 instead of more than 5 at least,
Sinosauropteryx 2 instead of 4, Sinovenator 1 instead of 4, Microraptor 2
instead of 25, 'Epidendorosaurus' is probably not even from the Yixian
Formation... The birds are even worse. Only 8 Confuciusornis?! Over 140
specimens have been
separately listed in the literature and several hundred were reported to exist
even as early as 1998. So that biomass would go from 34.4 kg per square km to
602 kg at bare minimum. Surely that would have some effect on the
calculations? Zheng et al. (2011) reported over 100 Jeholornis, nearly 100
Sapeornis and over two dozen Hongshanornis, but Matsukawa et al. only list 3,
3, and er... none respectively. Who knows why Hongshanornis is missing, but
they have one Gansus specimen listed despite it being from a completely
different formation. And being known from at least 70 specimens, not one.
Otogornis is also listed as Jiufotang, but is also from a different locality.
The masses are also way off, at least in comparison to each other. For
example, Yixianosaurus has a humerus 89 mm long, while Sinovenator's is 71 mm,
so cubing the ratio would make Yixianosaurus about twice the weight of
Sinovenator. But it's listed as five times heavier in the table. Finally, the
eeding modes' listed are often problematic.�!
� Every J
ehol bird was a omnivore, eh? Despite the wildly varying dentition and beak
shapes. Even more ridiculously, all of the Jehol amphibians were omnivores?!
I'm no amphibian expert, but I was under the impression almost all amphibians
are basically carnivores or insectivores, with the exception of algae-scraping
In conclusion, unless I'm missing something obvious about the paper, three of
the basic units of data Matsukawa et al. base their model on are completely
unreliable. A study like this cannot depend on published numbers of specimens
to approximate population ratios because after a taxon is described, only a few
other specimens are usually noted in the literature. What you'd need to do is
examine a huge collection, like the thousand or so Jehol coelurosaurs in the
STM, and hope there was little bias in what was collected. Even then, it only
shows you what died in the lakes, not what lived in the ecosystem. Do we
really think 80% of Yixian dinosaurs were Confuciusornis?
> Masaki Matsukawa, Kenichiro Shibata, Kenta Sato, Xu Xing and Martin G.
> Lockley (2014)
> The Early Cretaceous terrestrial ecosystems of the Jehol Biota based
> on food-web and energy-flow models.
> Biological Journal of the Linnean Society 113(3): 836–853
> DOI: 10.1111/bij.12368
> The ancient terrestrial ecosystems of the Lower Cretaceous Yixian
> Formation and the Jiufotang Formation, consecutive components of the
> Jehol Group in Northeast China were reconstructed using an energy-flow
> and food-web model. This model can be used to quantitatively estimate
> population densities for ancient terrestrial vertebrates based on food
> webs, net primary productivity, and three categories of
> energy-transfer efficiency. The results indicate that densities
> reached 866 individuals km−2 and 4122 individuals km−2 in two
> ecosystems, respectively. The main component of the vertebrate fauna
> of the Yixian Formation consisted of large herbivorous dinosaurs,
> while much smaller avians dominated the Jiufotang fauna. The model
> also indicates a temporal transition in the dinosaur fauna from the
> Yixian fauna to the Jiufotang fauna in which theropods decreased and
> ceratopsids became more abundant. We then compared these estimates of
> biodiversity with the Early Cretaceous Choyr fauna of Mongolia, and
> Tetori fauna of Japan using Simpson's diversity indices. Those
> indices, based on biomass, indicate that the biodiversities of the
> Jehol fauna lay between those of the Choyr and Tetori faunas. This
> range in biodiversity seems attributable to fundamental differences in
> vegetation and the environment.