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Snake taxonomy has gotten wild

Posted: September 15th, 2019, 10:14 pm
by jonathan
On one hand this might be old news for everyone else. On the other hand I might have details completely wrong. But this is what I think I've just learned.

When I was a kid, the snake families were easy. You had colubrids, which were just about everything (especially if you lived in Oregon). Then you had Vipers, Elaphids, and Boas/Pythons as the other families. Oh, and remember that there's Blind Snakes out there somewhere.

That was it. Five families. Pretty straightforward, and pretty easy to see. It might not even have been correct at the time when I learned it, but it's the basics that most casual herp enthusiasts like me understood.

Now, let me see if I can get the current situation right....

Caenophidia is the infraorder that contains 80% of snake species in the world, including all the Colubrids, Vipers, Elaphids, Slug Snakes, Odd-scaled Snakes, Asian Water Snakes, and Wart Snakes, which are somehow all related to each other. There are seven existing super-families in Caenophidia.

Colubroidea is the superfamiliy at the center. This is now the "Colubrids", but there's plenty of arguments over whether numerous groups inside of it, including Natricidae (new world garter/water snakes and old world grass snakes/keelbacks) should be their own separate families.

Elapoidea is the closest relative to Colubroidea. But the superfamily Elapoidea doesn't just include traditional Elaphids (cobras, kraits, sea snakes, etc.), but also the Lamprophiids (a huge group of ~70 former colubrid genera such as the Sand Snakes, Mock Vipers, and African House Snakes), the Stiletto Snakes, and a few obscure obscure genera that were once thought to be colubrids. In fact, if you want to keep the traditional idea of colubrids as an intact family, then you have to consider elaphids to be just another subfamily of colubrids.

Homalopsidae is the next closest relative, the Asian Water Snakes. Note that Elaphids are more closely related to "true" Colubrids than Asian Water Snakes are.

Viperidae is the next most closely related superfamily, consisting of all the traditional Vipers and Pit Vipers

Pareidae, the Slug Snakes, come next. Again, these are former colubrids who turn out to be further from the colubrids than the vipers and elaphids are.

Xenodermidae, the Odd-scaled Snakes, are next. These are the weird primitive looking east/southeast Asian snakes like the Dragon Snake.

Acrochordidae, the Wart Snakes, round out Caenophidia. Sometimes they are placed outside of Caenophidia altogether.

Booidea is the next infraorder, which helpfully contains "almost everything that looks like a boa", including New World Boas and Anacondas, and the Mexican Dwarf Boas as well as Sand Boas of Asia/Africa and the various "boas" of Madagascar, New Guinea, and Calabar. A couple obscure families of snakes called Bolyeriidae (the Round Island Boas) and Xenophidion (Spinejaw Snakes) may be the closest things to a link between Booidea and Caenphidia and are sometimes placed outside of Booidea.

Pythonoidea ends up being completely different from Booidea, and includes not just all the Old World Pythons but also the Mexican Burrowing Python and the Sunbeam Snakes of Southeast Asia.

Uropeltoidea, and not boas, are the closest living relatives to the Pythonoidea. They include the Shieldtail Snakes and the Asian Pipe Snakes, small nondescript burrowing species.

Amerophidia is a weird superfamily that contains just 3 genera which aren't related to anything else and don't look anything like each other either. They are Anilius (just one species, the False Coral Snake of South America), Trachyboa (the Eyelash Boas of Panama, Columbia, and Ecuador), and Tropidophis (the Caribbean "wood snakes" or "West Indies dwarf boas").

Scolecophidia, the Blind Snakes, end up being the biggest outliers....but there's five different families of blind snakes and they may be more different from each other than, say, a boa is from a viper. Typhlopidae is the main one that everyone knows about, but 40% of blind snakes turn out to be from one of the four families outside of Typhlopidea and may not even be related to Typhlopidea at all but are just the result of convergent evolution.

Okay, I think I got that right?