2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Epiornis birds fed at night and relied not on sight, but on smell.
Aepiornis, the largest bird ever to live, appeared to be nocturnal and nearly blind, according to Proceedings of the Royal Society B. American biologists came to this conclusion after reconstructing and analyzing the endocranium (relief on the inner side of the skull) of two species of Aepyornis.
Epiornis birds lived in Madagascar and, apparently, were exterminated by humans from 500 to a thousand years ago. From the found remains, it is known that these were the largest birds on the planet. According to researchers, epyornis could weigh over 400 kilograms and reach three meters in height. Epiornis belonged to the group of ratites (like ostriches, cassowaries or emus), and judging by the genetic data, their closest relatives were the New Zealand kiwi, birds with very poor eyesight, but a good sense of smell, which lead a nocturnal lifestyle. However, there is very little information about the lifestyle of the Aepyornis. Previously, paleontologists only twice examined the structure of the brain of epyornis (one of the works was published in 1942) and found that the visual lobes of the brain in these birds are very small.
Biologists from the University of Texas at Austin Christopher Torres and Julia Clarke decided to study the structure of the brain of Aepyornis with modern methods in the hope of learning more about the habits of these birds. Scientists using computed tomography have reconstructed and analyzed the endocranes of two species of Aepyornis, Aepyornis maximus and A. Hildebrandti. The skeletons of these birds are kept in the National Museum of Natural History in Paris. Basically, the authors paid attention to the size of the visual cortex and olfactory bulbs in the brain of Aepyornis. For comparison, the researchers reconstructed the endocranes of one of the tanager and sandpiper birds, and also used the already known data on the size of olfactory bulbs in 11 species of extinct and living ratites.
The results of the reconstruction showed that the visual cortex in both species of epyornis was greatly reduced in comparison with other birds with the exception of the kiwi. From this, scientists concluded that the epyornis, as well as the kiwi, had very poor eyesight and were nocturnal. At the same time, the olfactory bulbs in A. maximus, like in kiwi, were rather large, while in A. h ildebrandti they were smaller. The researchers concluded that large olfactory bulbs and small sizes of the visual cortex were characteristic of the common ancestor of the kiwi and epyornis birds. Later, in the process of evolution in A. h ildebrandti, the olfactory bulbs decreased. Based on the phylogenetic analysis carried out by the authors of the study, large olfactory bulbs were characteristic of ratites living in the forest, and small ones - for those who lived in open spaces. From this, the scientists concluded that A. maximus was a forest dweller, while A. h ildebrandti preferred grassy plains.
Evolution of sight and smell in ratites
Recently, zoologists revised the classification of epyornis birds and singled out their largest representative in a separate genus. The birds, which could weigh 640 kilograms, were named Vorombe titan.
