Response to Comment on "Small Bilaterian Fossils from 40 to 55 Million Years Before the Cambrian"

Abstract

The comment of Bengtson and Budd (1) is predicated on a preconception that any structures in sectioned Doushantuo microfossils that are claimed to represent cellular features in the original animal must instead be diagenetic artifacts. This preconception is demonstrably false. There are many examples of cellular structures in sections through other Doushantuo microfossils (Fig. 1, A to D, and F) preserved in phosphorite, as are the Vernanimalcula sections (2). Indeed, a scanning electron microscopy (SEM) image (Fig. 1E) displays a very similar cleavage form, as does the section in Fig. 1D. Both large and small blastomeres are demonstrated in both images. In the sections, the locations of at least two essentially definitive cellular features of the original embryonic cells, vis, their boundaries [(that is, cell walls) (Fig. 1, A to D and F)] and their nuclei (Fig. 1A) can easily be seen. Thus, it is counterfactual to deny preservation of structural morphology at the cellular level in this kind of material.