To confirm this, Ryberg and her colleagues gathered samples of fossil wood and examined the tree rings.
In order to derive age estimates for the Culebra and La Boca formations, we collected seven samples of fossil coral and bivalves from two sections containing the La Boca and upper Culebra formations and analyzed them for their 87Sr/86Sr ratios (Figure 7; Table 2).
Results of the analysis of an abundant sample of fossils in Wales from near the beginning of the Devonian Period is shown in the figure.
This approach appears obvious, but it has its subtlety, acknowledging that any known sample of fossils represents a species that was successful at the time but was not necessarily the direct ancestor of later species.
Notwithstanding this fundamental scaling correction, many paleoecologists continue to refer to almost any sample of fossils – of almost any size – as a "community".
More to the point, the periodic sampling of fossils over millions of years is sufficient to provide documentation of the sequential acquisition of specialized features in all of the major dinosaur lineages.
The comparative sample of fossils was originally presented and described by Scott et al [11], and includes South African Australopithecus africanus (n = 10) and Paranthropus robustus (n = 9) from Sterkfontein and Swartkrans respectively.
In doing so, the available sample of fossil specimens was increased substantially, making it possible to test prevailing locomotor hypotheses for many taxa with new specimens.
One sample of fossil wood has been identified as Guibourtia coleosperma (Caesalpiniaceae), a relatively uncommon tree, which today grows in Angola, Botswana, Namibia, Zambia and Zimbabwe.
For the first time, the sample of fossil taxa includes most of the best-known arthropods from all major Cambrian to Devonian Konservat Lagerstätten, including Chengjiang, Sirius Passet, the Emu Bay Shale, the Burgess Shale, Swedish Orsten, Herefordshire and Hunsrück.
