Aussie Researchers Reckon This Big-headed Fish Is the Key to Evolution

Aussie Researchers Reckon This Big-headed Fish Is the Key to Evolution
Image: Flinders University

Roughly 385 million years ago, fish first started to leave the water – a crucial development in the evolution of many land-based species. Now, with Flinders University studying the fossil of a big-headed ancient fish, we have a better idea of how fishies from many millennia ago made the jump (walk) to land.

The research was conducted on one specified big-headed fish – the Cladarosymblema narrienense, a fish from the Carboniferous period, which was about 330 million years ago. This fish was found in Queensland and is ancestor to land animals and four-limbed vertebrate tetrapods.

This big-headed fish didn’t have time for nonsense. Scans of its fossil found that it had quite a large brain – more similar to its land-fairing descendants than its water-swimming counterparts. This was uncovered using Australia’s largest CT scanner at Flinders University.

“This fish from Queensland is one of the best-preserved of its kind in the entire world,” says John Long, a Strategic Professor in Palaeontology at Flinders University.

“This helps us to understand the functional morphology and relationships of Cladarosymblema,” added Dr. Alice Clement, the lead author of the new paper on the topic and a member of the Flinders Palaeontology Group.

“Additionally, a cranial endocast (mould of the internal cavity of this fish’s unusually large skull) gives clues as to the shape of the brain of this animal. The area for the pituitary gland (so-called the ‘master gland’) is relatively large, suggesting a significant role in regulating various important endocrine glands.”

So, what does this research mean? It means that the megalichthyid fish form a monophyletic group (or, a natural clade). This is to say a group with a common ancestor, which the Cladorasymblema is found to be one of the derived members of said group.

It’s also an indicator that fish could have evolved bigger brains before squirming onto the shores of the Earth to live out as terrestrials. Makes sense – work out at the library before working out at the gym* (*Note that fish did not have access to libraries in the Carboniferous period).

Fish rule.