Mexican rattlesnake ID (also posted in the main forum)

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azatrox
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Mexican rattlesnake ID (also posted in the main forum)

Post by azatrox »

On a recent Mexico trip, the group found a couple molossus complex animals. Both of these animals are from the same general area (southeastern Sonora). There seems to be a question about whether these animals are C. m. molossus or C. m. nigriscens. I've done a bit of research and found 3 sources that state these animals to be C. m. nigrescens. They look different than the "traditional" nigriscens I've seen, but (with the molossus complex in particular) that really doesn't mean much as they are tremendously variable over much of their range.

Anyway, if any authorities on Mexican rattlesnakes want to chime in with their input, it would be appreciated. Thanks.

-Kris

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Crotalus
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Re: Mexican rattlesnake ID (also posted in the main forum)

Post by Crotalus »

It's hard to throw snakes from that area into one bucket or another - it's an intergrade zone mixing molossus molossus, molossus nigrescens, and molossus basiliscus. Same problem happens everywhere the SMOcc starts to hit the pacific coastal plain, but its a bit more complicated in Sonora because of molo molos.

You can pull snakes off the highway connecting sahuaripa to hermosillo that look like desert phase molo molo, then snakes from sahuaripa to the 16 that look like basis, and then highway 16 itself is sort of a mess with basiliscus looking nigrescens sprinkled all over the place. When you go east out of yecora and pop into chihuahua they definitely look a more molo nigrescens though. First snake looks pretty typical for those NW nigrescens from yecora or slightly west of yecora, the 2nd looks like you've dropped a bit lower and are starting to get some molo basi/molo molo influence.
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azatrox
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Re: Mexican rattlesnake ID (also posted in the main forum)

Post by azatrox »

Thanks JJ….Yeah, I quickly learned after posting this that defining molossus/basiliscus down there is a muddy mess…I wouldn’t be a bit surprised if they’re all just considered more or less the same animal in the future….

-Kris
will lattea
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Re: Mexican rattlesnake ID (also posted in the main forum)

Post by will lattea »

So the current understanding is that basiliscus is related to molossus and not durissus? Is it Crotalus molossus basiliscus or is basiliscus a full species? What is that based on? Where does totonacus fit in now? My sources are apparently out of date...

-Will
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Correcamino
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Re: Mexican rattlesnake ID (also posted in the main forum)

Post by Correcamino »

molossus/basiliscus is basically the mother form. Crotalus culminatus branched off of basilossus on one line. Simus and tzabcan branched off in a separate line. Durissus branched off of simus and migrated into South America. (Wuster et. al)

Although basiliscus isn't "officially" placed in molossus yet, anybody that has herped up and down western Mexico knows they are one and the same. Same goes for totonacus on the east coast.

Rumor has it that in all the recent DNA work, several different lineages have come out, molossus from western N.M. thru Az. and basiliscus are the same(I guess basiliscus would be sunk as molossus takes precedence), totonacus and eastern molossus (eastern N.M. and Texas are the same), and a couple lines if nigrescens which would include oaxacus. All just rumor so far, could come out with several species etc. Time will tell.

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