Write things. Estivate. Acclimate. Repeat.

The musings, brain droppings, and research interests of Nick D. Waters

What manner of beast are you? It's a Carefree talussnail (S. cf. carefreeensis), US.AZ.GI.MZ04 locality, but not where I expected it to be. It's morphology is entirely consistent with the type locality at US.AZ.MA.CWC. Understanding what I was looking at, over 10 years since it was photographed and collected, was revelatory.

When I collected it I did not have the level of awareness that I do now. Native snails can be very far ranging, and due to that very fact that they are native, exhibit variation. When a species is defined we need to become cognizant of the breadth of that by sampling further abroad, ideally find the extent of the entire range, and account for it in the description lest we incompletely describe a species or worse yet, split a taxon unnecessarily.

In the good old days, every rock had something new and one could get away with describing a species based on shell morphology alone if there was nothing else on hand. If you were well funded or ran an entire Malacology department, then your students and staff could collate additional details and fix things on the fly, and publish updates with relative ease. That is no longer possible, and species descriptions, done well, take years. Describing species today carries ramifications far beyond the academic practice of taxonomy. Biodiversity conservation is key to managing natural resources.

Ambigua Species Complex

October 30, 2026.

This page concerns teasing apart the evolutionary history of the Sonorella ambigua complex, for lack of a better name at present.

Miller (1967 Dissertation) considered S. ashmuni and S. ambigua to be part of a single group. My molecular data show that Ashmuni are a very closely related, recent taxon, whereas Ambigua are more diverse. Further, were we to include Ashmuni and Ambigua together, we would also have to include species he did not, including at minimum S. neglecta, S. dalli, S. sitiens. I will proceed by using the molecular results to guide selection of character traits that inform relationships within the complexes. Evidence of hybridization will be telling if morphological comparison and molecular data disagree. At present I only have mitochondrial data available. Nuclear DNA in the form of ITS2, 28S, or H3 would be very helpful.

Miller's Ashmuni group includes the following, from Figure 3, page 246 of his dissertation, consolidated:

Sonorella ambigua complex

S. ambigua ambigua

S. a verdensis

S. micromphala

S. carefreeensis sp. nov. Waters et al. in prep.

Several forms described in times past were lumped. Subspecies were abandoned. In the light of molecular data, differences in external morphology are proving useful and thus snails featuring distinctive proportions and coloration will be treated as potential cryptic species in the interim. Traits that immediately warrant attention are general body wall coloration, gland density, tail length, and skirt proportions. Features of the head and tentacle are less immediately obvious but need study. Some snails have shell features that are sharply contrasting as well. They are at least telling insofar that a population or set of populations are distinctive from their neighbors.

This page will be updated with photographs of living specimens from Type localities, historical, and new sites. I will also be posting images of the verge for the sake of comparison and work with Miller and Pilsbry's definition of the complex. Molecular evidence will also be brought forth.

Malacological study involves many subdisciplines. I will pursue information as its found and to erect a framework to describe the itnerrelationships of snails from multiple sources. All of this will feed a phylogeny, and we can map that to elucidate evolutionary hypotheses, which for me is the icing on a very delicious cake.

It is wonderful to discover species, laborious to describe them, and thoroughly enjoyable to sit at my computer and ponder their phylogeny with a hot cup of Mocha and the kids laughing in the background over whatever it is they are doing at that moment.