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A Systematic Study of the Big-eyed Armored Catfish Hypoptopoma, by Dr. Adriana Aquino |
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Our First Objective is to Test the Monophyly.
To define groups with a shared history, find a character shared by every member within the group that is unique to the group. This character shows that they share a common ancestor - the first one to acquire that character. All subsequent species inherited this character.
The Methodology is to Check the Traditional Diagnosis of the Genus. Here in the 21st Century, scientists are able to determine the history of the species they find today and put forward an hypothesis of common ancestry. This gives us a very special sense of being privileged spectators in the history of evolution. We're at the "tip of the iceberg," and from there we can reconstruct the history of our group. So, indirectly, that shared character supports the monophyly of the genus and in doing so, helps define what we term "a valid genus." While examining Hypoptopomaand related genera, I found two other genera with relatively large eyes. Both are the closest sister groups of Hypoptopoma,according to more recent phylogenetic hypotheses. Therefore we can discard "big eyes" as a character to identify the genus Hypoptopoma. 
Can we use the character 'large lateral eyes' to identify Hypoptopoma? The presence of 'large lateral eyes' is not unique to the genus Hypoptopoma.Rather, it defines the group that includes Oxyropsisand Nannoptopoma,as well as Hypoptopoma.This makes it a useful character at a level higher than, or more inclusive than, the genus itself. |
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page 13/14 |
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