Rods and cones in an enantiornithine bird eye from the Early Cretaceous Jehol Biota

Tanaka, Gengo; Zhou, Baochun; Zhang, Yunfei; Siveter, David J.; Parker, Andrew R.

doi:10.1016/j.heliyon.2017.e00479

Cited by 3 publications

(1 citation statement)

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“…However, other structural data are open to subjective interpretation. One example is likely the recent report of rods, cones, and oil droplets from a fossil bird retina based on low-resolution electron micrographs (Tanaka et al, 2017). Other structures show high levels of variation in size and shape more consistent with abiotically self-organizing structures than biologically formed structures (Brasier et al, 2006), such as putative dinosaur erythrocytes (Bertazzo et al, 2015) which are most likely degraded organic material, possibly exogenous, shaped by the low pressure or vacuum conditions of electron microscopy (Saitta et al, 2017b).…”

Section: Electron Microscopy and Pattern Seekingmentioning

confidence: 99%

A perspective on the evidence for keratin protein preservation in fossils: An issue of replication versus validation

Saitta

Vinther

2019

Palaeontol Electron

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The preservation potential of biomolecules within vertebrate integument through deep time has recently been subject to much research and controversy. In particular, the preservation potential of proteins, such as collagen and keratin, is currently debated. Here, we examine claims from a recent study (Schweitzer et al., 2018, PLoS One), which concludes that feather keratin has a high preservation potential. We argue that this work provides insufficient evidence for protein preservation due to issues of methodology and data interpretation. Additionally, we contrast their approach and claims to those of other recently published studies in relation to the question of keratin protein preservation in fossils. We worry that most of the perceived evidence for Mesozoic polypeptide survival stems from repeated replication of methods prone to false detection, rather than triangulation by validating these claims with alternative methods that provide independent lines of evidence. When alternative explanations exist for the evidence cited as support for dinosaur proteins far exceeding their predicted preservation limits, it is most parsimonious to reject the more extreme taphonomic hypotheses. The evidence is instead more consistent with a mode of preservation in which keratinous structures do not fossilize organically as polypeptides, but rather as largely pigment and/or calcium phosphate remnants, which were originally held within the keratin matrix that is now lost. Unsupported taphonomic models (e.g., keratin polypeptide preservation) have the potential to influence our interpretation of fossil data, potentially resulting in erroneous paleobiological or evolutionary conclusions, as illustrated in another recent paper (Pan et al., 2019, PNAS) that we also discuss.

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