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Colchicine
at Wed Mar 31 10:09:35 2004 [ Email Message ] [ Show All Posts by Colchicine ]
After reviewing Dwight Platt's 1969 publication on the Natural History of Hognoses I thought I would post some of the interesting information on their evolutionary history.
The author states that the fossil record of hognoses rests for the most part on scattered vertebrae around 5+ million years ago. Apparently hognoses are a primitive group of colubrids, but obviously they are very specialized. Heterodon retained a number of primitive viper like characters, while Xenodon evolved musculature resembling advanced colubrid snakes.
In his 1952 publication, Edgren claims that the Western species is the most "bizarre" and most highly evolved of the hognoses. The eastern species more closely resembles a generalized colubrid with a smaller rostral scale with less projection, a longer head, a somewhat longer tail, and it's larger size is probably a primitive trait as well.
Now here is when it gets really interesting: the Eastern and the Western species apparently were already separated evolutionarily before they could be classified as the genus Heterodon. My take on this is that they separated from their ancestral stock, and what we see today with the three species of Heterodon is a perfect example of parallel evolution. In order to help you understand this, let's not forget that our system of classification is inherently flawed since we are subjectively drawing lines where one species ins and where another begins. In other words, we all know that the Western, Eastern, and Southern hognoses are similar because not only are they classified together in the same genus, but they at least superficially resemble each other. BUT! It is entirely humans that have put these animals together that may not necessarily belong together in the same genus.
I have learned that literature like this may be extremely dated and that some of this information may not at all be true. However I have not come across other literature that describes an updated version of the evolutionary history of hognoses, although according to Eckerman's review, there are some recent publications. Once I've posted this I plan on sending a link to several people who may be able to provide some input and perhaps we can have a good discussion about this topic and get some of the details ironed out.
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...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)
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 Evolutionary History of Heterodon - Colchicine, Wed Mar 31 10:09:35 2004
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