Media release – 11 March 2009

Rattlesnakes rattled!

Rattlesnake classification has just had a major shake up.

In fact it’s been the first such shake up in nearly a century!

Recent studies of the DNA of the group showed various lineages to be far more ancient than earlier thought.

However there was confusion as to which groups of snakes had actually been named at the genus level in the past.

It turned out that just 5 of 16 obvious subgroups had been named.

In a paper published this week, Australian zoologist Raymond Hoser reclassified the group assigning names to the other 9 groups and working out which species were closest to which.

Taking a conservative stand, all groups had diverged at least 10 million years from a common ancestor to warrant being named at the genus or subgenus level.

By contrast for great apes (including humans) anything with a divergence of more than 4 million years is placed in a separate genus.

Recent papers have placed the rattlesnakes origins back to nearly 30 million years.

Formerly all fifty-odd species were lumped into a single genus “Crotalus”, with some people placing three small species in a second genus Sistrurus.

Hoser’s paper, while seemingly radical in terms of the number of new genera named, has been described by himself as “merely stating the obvious”.

In 2004, Hoser controversially placed the world’s longest snake, the Reticulated Python, in it’s own genus, Broghammerus, taking it away from the better known genus “Python”.  Later DNA studies, the results of which were published in 2008, upheld the Hoser position, showing that they had diverged from their nearest python relatives about 30 million years ago.

Broghammerus reticulatus” is now generally accepted.

Hoser said this week, “No doubt there will be short term resistance from some quarters to use the new generic names, but, the concept of fifty odd rattlesnakes, many of radically different forms and ancient lineages, being in the same genus, is simply not tenable”.

The paper is:


“A reclassification of the Rattlesnakes; species formerly exclusively referred to the Genera Crotalus and Sistrurus.”

Originally published in hard copy in Australasian Journal of Herpetology, Issue 6 (9 March 2009):1-21.


The web link is at:

For further information:

Raymond Hoser – Australia +61 3 9812 3322

+61 412 777 211


See paper’s abstract here:


See list of rattlesnake species under the new classification here:




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