[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Darwinopterus notes



 Free Darwinopterus download:


http://rspb.royalsocietypublishing.org/content/early/2009/10/12/rspb.2009.1603.full.pdf

Thanks a lot!

The supp. inf. (a Word file) is accessible from here: http://rspb.royalsocietypublishing.org/content/early/2009/10/12/rspb.2009.1603/suppl/DC1

It starts as follows:

>>
A. Age of the Tiaojishan Formation

The strata in western Liaoning that yielded *Darwinopterus* gen. nov. are referred to as the Lanqi Formation (Bureau of Geology and Mineral Resources of Liaoning Province 1989), but appear to be equivalent to the Tiaojishan Formation of Hebei and Inner Mongolia. The Tiaojishan Formation was named prior to the Lanqi Formation, thus it has been suggested that the latter name be replaced by the former (Wang et al. 2000), a proposal we accept here. The Tiaojishan Formation is generally regarded as Middle (Zhang & Zheng 1991; Liu et al. 2006; Cheng & Li 2007) to Upper Jurassic (Chang et al. 2009) (Late Bathonian-Early Kimmeridgian) in age, although it may date to the early Middle Jurassic (Aalenian) in Jianchang County (Davis et al. 2001). The unit has been dated using radiometric techniques at 169-152 Mya by Liu et al. (2006) and 165-156 Mya by Zhang et al. (2008).
<<

Compare:
http://stratigraphy.science.purdue.edu/gssp/index.php?parentid=35
Kimmeridgian-Tithonian boundary 150.8 +- 4 Ma ago
Oxfordian-Kimmeridgian boundary 155.6 +- 4
Callovian-Oxfordian = MJ-LJ boundary 161.2 +- 4
Bathonian-Callovian boundary 164.7 +- 4
Bajocian-Bathonian boundary 167.7 +- 3.5
Aalenian-Bajocian boundary 171.6 +- 3

I'd say it was a bit irresponsible to put "from the Middle Jurassic of China" into the abstract and the introduction. It has about a 50 % chance of being true.

 And I'm also disappointed to read this from the
 Suppplmentary Data: "The search was terminated at 500,000 trees due
 to memory limitations." That's a sign that something is wrong. The Lü
 study needs to use more of the available taxa.

And a lot more characters! 117 characters for 56 taxa -- that's less than twice as many. Under three times I wouldn't bother publishing.

Also, all characters were unordered. Some of them are continuous, like number 6: "Rostral index: 1.5 or less (0); 1.5-3.0 (1); >3.0 (2)". This is not defensible (Wiens, 2001, Syst. Biol.) -- the assumption that underlies ordering, namely that it is easier to change from a character state to a similar one than to a more different one, was _already_ used to divide the continuous character into states; if it's easier to go from 1.3 to 1.4 than to 1.6, it must also be easier to go from 1.3 to 2.0 than to 3.5, in other words, not ordering the character is logically inconsistent.

The consistency index is strangely _high_ (0.47).