This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
Spinosaurids (Diapsida: Spinosauridae) and sphenacodontids (Synapsida: Sphenacodontidae) share not only a characteristic tall neural spines, but also an atypical – compared to their close respective relatives – ecology, i.e. apparently piscivorous and possibly semiaquatic mode of life. This similarity might hold clue for the role of their sails. It is here suggested that sails of these animals 1) served thermoregulatory function, warming the animals, otherwise submerged in the water, as well as 2) enabled them to hunt for fish in a way similar to the technique of Recent diapsid, black heron (Egretta ardesiaca).
The following was added:
After the publication of this preprint, I was contacted by my colleague, Maciej Ziegler, who pointed out, that he envisioned a similar parallel between Spinosaurus and Egretta as me, and published the idea few years ago, in a popular text in Polish. As at that time we were working together on a project including, amongst others, his text, it is possible that I might have read his work. Yet, I don’t remember doing so, and besides, I started to think about the idea only after seeing black heron on TV, sometime at the end of 2016 or beginning of 2017. Whether we acquired our idea strictly independently, or was I incepted, Maciej Ziegler should be cited as first to notice similarities between Spinosaurus and Egretta.