might also be explained by the presence of more than one species, although there are no anatomical features that could be correlated with these potential species. It could also be explained by assuming an attritional death assemblage, in which mortality rates (and thus the number of preserved fossils) are highest in young and in very old individuals. The idea of a dinosaur-like mode of growth was criticized by Winfried and Dieter Peters in 2008, who argued that the body size of the smaller size class was too large to possibly have represented the youngest growth state. Analyzing an extended data set, these researchers identified a third size class that supposedly represented this youngest growth state. As it would be highly unlikely that Confuciusornis showed two distinct growth spurts, a feature unseen in known amniotes, they concluded that the two larger size classes represented the two sexes rather than growth stages (sexual size dimorphism). The long tail feathers would have occurred in both sexes, one of which was the largest. This interpretation is consistent with an avian-style mode of growth, as it was suggested by the earlier histological studies. It is also consistent with comparisons to modern birds, in which long tail feathers are typically unrelated to the sexes. The absence of long tail feathers in many specimens was suggested to be the result of stress-induced shedding prior to death. Chiappe and colleagues defended their findings in a 2010 comment, arguing that the assumed short, avian-like growth period is unlikely. The calculation presented by De Ricqlès in 2003 of a growth phase of less than 20 weeks was based on the assumption that bone diameters grew by 10 µm per day, which is subjective. Rather, histology reveals the presence of different tissue types in the bone that grew at different rates, as well as pauses in growth as indicated by the lines of arrested growth. Thus, growth periods must have been longer than in modern birds and likely took several years, as is true for the modern kiwi. The observed size distribution can, therefore, be feasibly explained by assuming a dinosaurian-style growth. In an invited reply in 2010, Peters and Peters stated that Chiappe and colleagues did not comment on their main argument, the gap in body size between the smaller size class and inferred hatchlings, which accounts for one order of magnitude and would be most consistent with a sexual