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Excerpts from Jim Conrad's
Naturalist Newsletter
entry dated March 9, 2022, issued from near Tequisquiapan, elevation about 1,900m (6200 ft), ~N20.57°, ~ W99.89°, Querétaro state, MÉXICO
SABAZIA ON ON A FAULT LINE
The above wildflower caught my eye back in January (still flowering in March) not only because it was so attractive, but because it grew in an unusual geological setting. It was on what appeared to be thick layers of volcanic basalt (solidified flowing lava) or maybe local bedrock that had been violently tilted on edge because it was exactly on what geology maps identify as the Falla Tequisquiapan, or the Tesquisquiapan Fault.The above image shows the rock's flowing, slanting layering. The fault runs for maybe 8-10kms north and south, with the southern end in downtown Tequisquiapan. Below, you can see the rock outcrop's larger-scale tilted layering from farther away, our plant hardly visible in the picture's lower, right corner. Most of the day this plant remains is in the cliff's shadow, on the north face.
During my months of exploring this area I've not seen this species anyplace else, including on other exposed rock cliffs. This species seemed special to me, so I began "doing the botany."
The flowering head is typical of daisy-like species of the Composite or Aster Family, the Asteraceae. The white ray florets are 3-notched, a good field field mark, and the cluster of disc florets in the blossom's "eye" are grouped in a spherical cluster.
Seen from behind, the blossom's green collection of bracts forming a cuplike involucre are distinctive in that the bracts occur in only one series, instead of overlapping one another like roof shingles, which is more typical. Also, the involucre and stem, or pedicle, are thickly covered with short, gland-tipped hairs, which is a little unusual, too. Things get even more interesting when a head is broken open:
The brownish, frankfurter-shaped items are florets' ovaries. They're unusually hairy and with distinct ridges running their lengths. Yellow corollas also are covered with short, glandular hairs, and items arising where corolla tubes merge with the ovaries form a surprising and unusual collection. They're better developed and more visible on ovaries that have matured into cypsela-type fruits, as shown below:
Jagged, irregularly formed scales form a kind of crown, plus they're accompanied by 3 or 4 long, slender, hairy bristles. This combination of features I can't remember seeing on any flower I've ever looked at. Surely with such an unusual collection of features, this would be easy to identify. Moreover, I hadn't taken a good look at the ray flower, a couple of removed ones shown below:
This species' ray flowers produce viable fruits, which is good to note, since in many groups the ray flowers are sterile. Finally, the leaves needed to be documented, for they were distinctive, too:
These leaves near the flowering heads had long petioles, and the blades were hairy, somewhat rigid, and showing slight indentations along the margin. Deeper into the plant's shadowy body leaves became definitely "dentate."
Despite all these very good field marks, I've had a hard time identifying this species, and am not sure I've come up with the right name. It took "oscargsol," a specialist in Mexican Aster Family species, to recognize this as EUTETRAS PRINGLEI.
Autetras pringlei is a pretty good find, for it's endemic just to two or three states in upland central Mexico. As such, I don't find much literature dealing with it, other than in lists of its occurrence here and there.