In the new research, paleontologists described and illustrated the endocasts (braincases) of six Paleozoic lungfish species from superb 3D fossil material, which are very informative for the understanding of brain evolution of lungfishes, the living sister group to land vertebrates.
Paleozoic lungfish endocasts in dorsal, ventral, and left lateral views. Image credit: Clement et al., doi: 10.7554/eLife.73461.
Lungfish — freshwater vertebrates belonging to the order Dipnoi — have persisted for 400 million years from the Devonian period to present day.
The evolution of their skull and dentition is relatively well understood, but this is not the case for the central nervous system.
While the brain has poor preservation potential and is not currently known in any fossil lungfish, substantial indirect information about it and associated structures can be obtained from cranial endocasts.
“Our discovery shows that the brains of lungfish have been evolving constantly throughout their 400-million-year history, but it suggests they have likely always relied on their sense of smell rather than vision to navigate their environments,” said Dr. Alice Clement, a paleontologist at Flinders University.
“This is quite unlike other fish which use sight much more powerfully.”
“Understanding how lungfish brains have changed throughout their evolutionary history helps an understand of what the brains of the first tetrapods might have looked like too — this can give us an idea of which senses were more important than others (such as vision vs olfaction).”
Using synchrotron and computed tomography, Dr. Clement and colleagues created 3D models of the cranial endocasts of six Paleozoic lungfish species: Iowadipterus halli, Gogodipterus paddyensis, Pillararhynchus longi, Griphognathus whitei, Orlovichthys limnatis, and Rhinodipterus ulrichi.
“The ongoing work is significant in broad evolutionary and paleontological science,” said Dr. Tom Challands, a paleontologist at the University of Edinburgh.
“Our paper effectively doubles the number of lungfish endocasts known, as their preservation quality is often damaged by a fossil being crushed or broken, and the brain itself has very poor preservation potential and is not currently known in any fossil lungfish.”
“Studying our ‘fishy cousins’ lungfish continues to help us understand how fish first left the water some 350 million years ago and started to become land animals (tetrapods), and later humans,” Dr. Clements said.
“Perhaps some of their nervous system traits remain in us still.”
The findings were published in the journal eLife.
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Alice M. Clement et al. Morphometric analysis of lungfish endocasts elucidates early dipnoan palaeoneurological evolution. eLife, published online July 12, 2022; doi: 10.7554/eLife.73461
Source link: https://www.sci.news/paleontology/paleozoic-lungfish-endocasts-10990.html
