Observation 194138: Thelomma occidentale (Herre) Tibell
When: 2014-12-20
(35.4514° -120.6437° 280m)
Who: J-Dar
No herbarium specimen

Notes: On old wood ranch fence, occurs only on top surface.

Proposed Names

0% (2)
Recognized by sight
46% (2)
Eye3 Eyes3
Used references: Nash V.2
Based on chemical features: Spot tests, see comment below.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Wow, exciting
By: Jason Hollinger (jason)
2015-02-01 00:12:08 GMT (+0000)

That really is what it should be given it’s on a fence post, but it’s so rare I refused to believe it. :) Well done! Great specimen.

Spot tests
By: J-Dar
2015-02-01 00:03:09 GMT (+0000)

Thallus K-, C-, KC- and mazaedium also negative for these three spot tests.

T. mammosum should have KC+ rose-red thallus and K+ Red mazaedium, while T. occidentale is negative for all. As far as range goes, this is south the mapped distribution for T. occidentale at CNALH, but Nash describes Sonoran distribution as southern CA and Baja.

I’ll add T. occidentale with a Could Be vote and let the experts weigh in!

On further consideration…
By: Jason Hollinger (jason)
2014-12-21 02:41:15 GMT (+0000)

T. occidentale is rare, and more northern. T. californicum should have conspicuous radiating marginal lobes. I think you have another rock lichen growing on wood: T. mammosum. It’s by far the most common Thelomma in southern California. No surprise it would occasionally find its way onto wood. Interestingly, though, it may never have been officially reported from wood…

By: Jason Hollinger (jason)
2014-12-21 02:29:43 GMT (+0000)

Only two species on wood in California:



Created: 2014-12-21 00:40:30 GMT (+0000)
Last modified: 2015-02-01 00:10:17 GMT (+0000)
Viewed: 85 times, last viewed: 2016-10-28 18:35:32 BST (+0100)
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