Counting Subcaudal Scales?

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MCHerper
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Counting Subcaudal Scales?

Post by MCHerper » June 19th, 2016, 10:22 am

Quick question: when looking at diagnostic criteria for snake species, is it typical to see total numbers of subcaudal scales, or do you count the rows? In other words, for an unknown species, would I typically count each individual scale, or count the shortest row and add one? Thanks for your help!

Jimi
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Re: Counting Subcaudal Scales?

Post by Jimi » June 19th, 2016, 7:15 pm

Whether divided or entire, just count the rows. And even in taxa with divided subcaudals, there comes a point where there's only a single subcaudal per row. There are usually several or even quite a few of these. Whether it's a pair or a single it counts as a row.

Happy counting! Ha ha. I find taking a picture (even if through glass, like a bottle bottom) helps - if you lose count it's easy to start over. And to get an independent count, etc.

cheers

Richard F. Hoyer
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Re: Counting Subcaudal Scales?

Post by Richard F. Hoyer » June 19th, 2016, 9:18 pm

MCHerper,
Not so quick of an answer. What species are you interested in and does it have caudals that are divided or entire? For taxonomic purposes, I have recorded caudals counts in three species two of which have divided caudals and one with entire caudals.

The latter species is the Rubber Boa which presents a set of problems that requires setting a standardized method for making such counts. The same applies to counting ventral plates as well.

In the boa, it is not uncommon to have a variety of anomalies in the form of single half size caudals on one or the other side of the tail, to have a series of such half size caudal, or to have a number of such anomalies. My method is to base my counts on whatever side produces the highest count when such half size caudal are present. I do the same with the ventral counts. There are some other types of ventral and caudal anomalies in the boa but they do not present a problem as do the half size ventrals or caudals that can occur on one or the other side of the snake.

In the two species of Sharp-tailed Snakes which have divided caudals, I standardized my counts to be taken on the right side only. That is, with the snake upside down, I only counted the row of caudals on my left which is the right side of the snake. Caudal anomalies were not all that frequent in those two species but a few such anomalies did occur where instead of split caudals, some caudals where entire. But that does not pose a problem with the method I used for both species.

As it turned out, the number of caudal scales was one of the two defining traits between the two species in that there was no overlap in caudal numbers when males and females were treated and compared separately.

I have always taken total and tail lengths and then calculated percent relative tail lengths by dividing the tail length by the total length. This defines or characterizing the difference that may exist in that trait between the sexes and between species. It so happens that percent relative tail length is the other trait in which there is no overlap between the two species of Sharp-tailed Snakes provided males and female are compared separately

Not certain if the above helps.

Richard F. Hoyer (Corvallis, Oregon)

MCHerper
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Re: Counting Subcaudal Scales?

Post by MCHerper » June 20th, 2016, 4:10 am

Thank you Jimi and Richard! The above are very helpful. My apologies for the oversight-I should have indicated that I was specifically interested in Colubridae species with divided scales, such as Carphophis, Diadophis, Storeria, Opheodrys, etc.

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BillMcGighan
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Re: Counting Subcaudal Scales?

Post by BillMcGighan » June 22nd, 2016, 1:17 pm

MCHerper, because I'm old school, I'm sorry more authors and herpers are not in tune to scale meristics as they used to be.
For what it's worth, here's a discussion (albeit not conclusive) that we had in the SE a few years ago where subcaudal pair became the center of attention.
http://www.fieldherpforum.com/forum/vie ... dal#p49982

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Kelly Mc
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Re: Counting Subcaudal Scales?

Post by Kelly Mc » June 23rd, 2016, 12:37 pm

Bill, i know what you mean - there is great emphasis on pattern variability and not as much on scale counts and formation than what i was exposed to on a solitary self schooled basis.

I remember being a kid and being absorbed by the diagram pages at the forefront of my field guides. I loved the names and terms, loved the origins and phonic feel of them. Still do.

MCHerper
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Re: Counting Subcaudal Scales?

Post by MCHerper » June 24th, 2016, 3:41 pm

Thanks Kelly and Bill!

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