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I'm thinking about doing some museum work on Drymarchon taxonomy, and so I pulled out a few preserved specimens today, of the 60 or so we have at LA Cty NH museum. I had thought that there were some identifying features separating unicolors and melanurus (BTs) other than the melanurus' dark tail end. Labial pattern, or something. But I can't find anything, at least after a quick look.

Does anyone who knows both have any observations here ? How about differences in the neonates ?

The taxonomy of the central american/mexican forms is pretty unclear, and there are many hundreds of Drys from those regions in museum collections, so some morphological and/or genetic work should resolve some key issues.

thanks
Craig

I am not sure if that is a feature separating melanurus but it could be. I looked at my unicolor and they don't have it but neither does my juvenile melanurus.

Does anyone else notice this? Is it a trait only found in melanurus?

Large old males tend to show some keels.

I have been keeping track of locality as much as is possible through Importers and paying attention to coloration on zoo specimens in their country of origin. My thoughts are that a pure unicolor is just that, uniform from head to tail. Within that complex I have noticed two forms but do not have locality data. Unicolor that is bright yellow with little or no black tick marks on the body and those which have an olive green cast with more ticking. I have noticed about four variations in Blacktail Cribos. High contrast, those with jet black tails, Those with Dark tails (reddish, brownish or dark yellow) tiger striped specimens and specimens that are maroon. I am sure some will be found to be locality specific. My opinion and I stress my opinion is that a blacktail in its pure form has a jet black tail. Once that population is isolated by geography and once Unicolor Pure animals are isolated by geography there will be a fairly extensive intergrade zone. It’s my understanding that Unicolor is found in Nicaragua and parts of Costa Rica. Some people use ventral tick marks as a way of gauging purity. I consider most of the Blacktails that come in from Honduras to be intergrade but I have one animal that would pass for unicolor. I will examine my high contrast animals to see if there is anything that stands out.

Just finished examining a high contrast male yellow unicolor and noticed something. Where the black starts on the Blacktail the unicolor has four apical pits per scale that continues past vent. The intergrade and blacktails do not have this nore does the olive unicolor.

thanks - that's interesting and very helpful. Color variation is so labile in most animals that, even though we use it and often start calling different morphs by color-based names ("red-tailed boas", it's often not very meaningful. Meaning intra-populational variation in color can be as great as interpopulational (like thinking that Okeetee Corns really all come from South Carolina, etc.). Something 'harder' like presence or absence of apical pits is potentially more important. I've never heard of that variation before, and it will, unlike color, show up in pickled museum animals.

I'll let you know what I learn as I look into this stuff.

Craig

The EMBL reptile data base will usually come up by typing Colubridae into your browser. It’s like one stop shopping when it comes to information search. You can access reptiles from all over the world and get just about any published information or a link to it plus pictures. A tool you should not do without on your quest. I have already compiled much along the same lines as what you are working on but it is fragmented at the moment and I have not had the time to sit down and compile the data.

http://www.embl-heidelberg.de/~uetz/families/Colubridae.html This is how my browser comes up.

One thing is puzzling me. I have found pictures of Black Tailed specimens at opposite ends of their range. Tiger striped animals in Guatemala and Columbians with Black tails. It's almost as if they are Unicolored in the Center of their range. They range from Mexico to Vesesuela.

another possibility is that our range and locality field data are incomplete and there are black-tailed and non-black tailed cribo morphs occurring in the known ranges of both unicolors and melanurus. It's a pretty trivial difference, really - you can probably think of known taxa that have that much variation without any subspecies disinctions.

I agree. That seems to make the most sense. Hatchling unicolor have Black tails at birth. Trans pecos ratsnakes are a good example there is a pocket of animals near Terlingua that are what is known as blond. It crops up in other areas but is consintrated around terlingua.

I have a few importers who have been gracious enough to share locality data with me. I poke around and see if unicolor pops up in populations thought to be inhabited by blacktail only.

this is the beautiful thing about museum collections - possible to see variation like this, including from localities that may no longer exist if the specimens were collected 50 years ago. Just takes a lot of time.

Another very valuable website is the 'combined collection index' of the Calif Academy of Science - you can get to a few dozen museum collections that are cataloged online, and look at detailed locality info for specimens. Got to go to the museums to actually see the snakes, however.

I have a young cb female unicolor that does not have a black tail - since neonates of many species have traits that show ancestral taxonomic links (like baby robins with their thrush-spotted breasts) I'd love to get a look at a large number of melanurus/unicolor babies.

Craig

Keep us Posted. Good Stuff.