Somehow I missed this: Clubtail dragonfly, genus Ophiogomphus

I was looking through my dragonfly photos this morning when it suddenly dawned on me that this nymph -- which I found in the Doyles on 9/2 of last year -- was not the clubtail dragonfly that I normally see.  The nymphs that I normally see have wingpads that are parallel to the body: they look like this.

Perplexed, I decided to key out both types and here's what I found.

17a  Naked antennal segment 4 generally about 1/2 as long as hairy segment 3..........Progomphus
17b  Segment 4 of antennae vestigal or nearly so.......18

We've got the latter as I'll show in a moment.  So on to 18.

18a Wingpads strongly divergent........... Ophiogomphus
18b Wingpads laid parallel along back........19

Here you go.

Ophiogomphus for sure.  Hmm...  But I'm quite sure that I thought the other nymph was Ophiogomphus.  Time to explore.  On to 19.

19a Body very flat: abdomen nearly circular in dorsal view; paired tubercles on top of head....... Hagenius
19b Abdomen more nearly cylindrical; no tubercles on head....... 20

19a describes genus Hagenius, and I've found quite a few of those over the years.

We move on to 20.

20a Antennal segment 3 flattened and oval, nearly as wide as long.... 21
20b Long antennal segment 3 more or less cylindrical....... 22

Definitely "nearly as wide as long."  On to 21.

21a Antennal segment 3 widest proximally..... Stylogomphus
21b Antennal segment 3 widest near middle, about 2 times as long as wide and rounded apically....Lanthus

Lanthus.  Got it.  And I find that one a lot.  But for me, Ophiogomphus is a new one.  Have to add that one to my list of taxa.