Journal Club: What we should be careful when estimating auditory function of dinosaurs.

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Today's journal article

Manley GA, Köppl C. When dinosaurs hear like barn owls: pitfalls and caveats in assessing hearing in dinosaurs. 

Why I picked this article

FOSSILS! This is an opinion piece, but I wanted to make an exception to share this opinion piece as part of my journal club series, because thinking about the hearing capabilities of dinosaurs and research surrounding it, based on fossils, is too exciting a topic to ignore. 

Let's hear what the authors had to say about hearing of dinosaurs. 

Some of the key points in the article

Fossils of dinosaurs can be researched using imaging techniques - typically, the "endosseous cochlear duct (ECD)" can be identified in the fossils, for comparison with existing related species like birds. Authors, however, point out caveats that: 

  • When analysing ECD length, it does not necessarily represent the size of the "auditory basilar papilla", an equivalent of the cochlea in birds, that correlates somewhat with the complexity of hearing. The size of the basilar papilla in birds can be very independent of the animal size or ECD. 
  • Similarly, if ECD length does not correlate with the length of the basilar papilla, then it is not a good measure of the hearing frequency range of the animal. 
  • Furthermore, authors suggest that the sensitivity of hearing (how small a sound it can detect) cannot be predicted from ECD. 

Authors make some recommendations around interpreting cochlear anatomical data: 

  • When comparing the size of ECD relative to the animal size, interpretation can differ whether it is size of ECD relative to body mass, skull size or brain height. A conclusion shouldn't be made on one alone.
  • While a general "trend" may exist about the relationship between auditory organ size and body size, etc, across species, some exceptions and deviations are possible, to a significant degree. 
  • When a novel (unique?) features are identified, how to interpret, and more importantly, "how to call it" requires significant caution, 

This opinion piece suggests that comparison with birds should be made with care. 

Many of the criticisms and suggestions were made in reference to the publication in Science by Choiniere et al. (2021) about the characterisation of the species Shuyuuia deserti, the "desert bird" characterised by the fossil. (DOI: 10.1126/science.abe7941)

From Fig 2b&c, Choiniere et al. (2021) DOI: 10.1126/science.abe7941

Haruna's takeaway

A lot of what this opinion piece is raising caution about, in terms of interpreting anatomical data, actually applies to all anatomical analysis and comparison across species. They are very good points. I resonated particularly with the last point around interpreting "novel features". When you are used to looking at one type of scan (e.g. bird), and look at another anatomical data from a different species, it can look very different, and some features will look as if they are new features. But if someone gives a "name" or description like "xxx-like structure", and if this is actually a wrong interpretation, then it can cause confusion to the subsequent studies. Anatomical terms, especially historical ones that changed over time, can become a barrier to consistency and clarity about the field. I guess this is particularly an issue in a small specialised research field, where reproducibility checks by other research groups can be difficult, like rare species/fossils. 

It's hard enough to measure and fully understand auditory function in existing species.... let alone extinct ones! It's also interesting how some research uses comparison of inner ear anatomy to help inform evolution. Maybe we'll participate in research like that, one day, if there is an opportunity. 

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This is Haruna's 21/100 of the 100-day challenge to post a science blog article every day! I love inner ear biology & cochlear physiology.