HISSS (Herpetological Investigations: Systematic Serpentes Sourcebook)

This database is intended to be a resource to aid in the identification of snakes from around the world.  Although there are regional guides to snakes for most countries, very few exist for larger geographical regions (i.e. Europe, West Africa, East Africa, South Africa, Central America) and none cover the entire planet except superficially.  The most comprehensive snake book is by O'Shea (2018) but only deals with 600 of the nearly 4300 currently recognized species and does not provide an identification key.  There is a dearth of basic scale counts in the literature.  Even among field guides, only a small proportion of them provide morphological data for the included species, the exceptions being publications that provide scale counts in addition to identification keys such as Stejneger (1907), Wall (1921), Taylor (1922), Pope (1935), Bourret (1936), Smith (1943), Silva (1980), Pérez-Santos & Moreno (1988, 1990), Zhao et al. (1998), Savage (2002), Carreira et al. (2005), Lang & Vogel (2005), Zhao (2006), Lemos-Espinal & Smith (2007a-b), Dixon & Lemos-Espinal (2010), Lemos-Espinal & Dixon (2010, 2016), Gaulke (2011), Lang (2011, 2013, 2017), McCranie (2011), Cox et al. (2013), Starace (2013), Cogger (2014), Stuebing et al. (2014), Pereira-Filho et al. (2017), Lemos-Espinal et al. (2018, 2019), Chippaux & Jackson (2019), Charlton (2020), Matsui & Mori (2021), Solórzano (2022), David et al. (2023), Spawls et al. (2023), Trape (2023), and Eipper & Eipper (2024).

The main source for identification of snake species by amateurs, hobbyists, and professional herpetologists alike are the dichotomous keys that are produced for most families and genera, usually updated with every new revision.  However, there are numerous snake genera for which morphological data and keys are not available.  Since there is no database of systematically important morphological data available, identification keys rely on couplets in which a selection is made based on one or more characters.  These keys can lead to erroneous conclusions when the user has characters that are anomalous, misinterpreted, indistinguishable, or even absent.  And for a key to lead to an incorrect identification, it only has to mislead or fail in a single couplet.  This compilation of morphological data on snakes of the world is based upon 1) my examination of many thousands of specimens, 2) published scientific and lay literature, and 3) unpublished data from colleagues and museum collections. 

The most reliable morphological data are those collected from examined specimens and this compilation, based as it is in large part on published records, cannot be expected to be complete nor fully accurate.  However, any errors are my responsibility and it is my hope that other researchers will contact me to point out such errors and to expand (or contract) the ranges of scale counts based on their personal data collection.  Scale count ranges for certain taxa, particularly those that have recently been split into one or more new species based upon molecular studies, pose a problem in determining the actual range of values for the original taxon.  Sometimes the ranges do not change (as when the ranges of the new taxa fall within those of the older one) but often one extreme of the other, or even both, are reduced as they refer to one of the new taxa.  In such cases, when the scale count ranges of the original taxon are very narrow, due to a small sample size of examined material, I conservatively retain the original values until better clarification is possible.  I prefer to overestimate the ranges of data rather than underestimate them for purposes of identification.

I plan on continuously updating this sourcebook and any assistance in improving and fine-tuning the data would be most welcome.  Much of the data is based upon only a few specimens and larger sample sizes would be greatly beneficial in estimating the entire range for various characters.  Anyone contributing data will be recognized in future editions.