Observation 220860: Clavascidium lacinulatum (Ach.) M. Prieto
When: 2015-10-26
35.4026° -120.2787° 608m
Who: J-Dar
0 Sequences

Dry open oak woodland-scrubland interface with patches of bare rocky red soil partially vegetated with mosses and terricolous lichens.

Squamulous, perethecia present, some younger squamules pruinose. Rhizinate.


Perethecia (black dot) on squamule
Underside of squamule showing rhizines
Squamule rhizine
Squamule cross-section

Proposed Names

-56% (1)
Recognized by sight
-16% (2)
Recognized by sight
15% (2)
Based on microscopic features: Rhizinate

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Chalk one up for the splitters!
By: J-Dar
2015-10-28 18:18:19 PDT (-0700)


The sister relationship of Heteroplacidium and Placidium
sensu Gueidan et al. (2009) is highly supported (100% both ML
BS and PP). Moreover, the first split within the latter, corresponding
to nonrhizinate and rhizinate Placidium species, is
highly supported ( Figs. 3, 4 ). Because both clades are monophyletic
and can be easily differentiated by the presence of
rhizines, we propose that Clavascidium (synonymized as Placidium
by Gueidan et al., 2009 ) be adopted as a valid generic
name for species of Placidium with rhizines (see Taxonomic
Two distinct sister groups can be distinguished within the
Placidium clade sensu Gueidan et al. (2009) . Clade D is composed
of members of Clavascidium characterized by the presence
of rhizines and includes species with clavate to (sub)
cylindrical asci ( Fig. 4 ). The latter character was traditionally
used for separating Placidium from the rest of genera included
in Catapyrenium s.l., especially to distinguish Clavascidium
from Placidium ( Breuss, 1996 ). However, both ascus types are
present in the current delimitation of Placidium , although species
with clavate asci are mainly found within Clavascidium .
This group includes the type species of Clavascidium ( C. umbrinum
) and members of the four varieties described for Placidium
lacinulatum ( Breuss, 2002 ; Lendemer, 2004 ), here
transferred to Clavascidium . Although the classification at the
species level does not agree fully with the resulting monophyletic
groups, our results support a clade including specimens
with black rhizines and dark exciples ( C. lacinulatum var.
atrans , C. umbrinum, C. pseudorufescens , and Clavascidium

Sure go ahead
By: Jason Hollinger (jason)
2015-10-28 16:45:52 PDT (-0700)

I didn’t know about the name change. Go ahead and deprecate Placidium lacinulatum in favor of this new name. Someone apparently thinks P. squamulosum is sufficiently different now as to place it in a different genus, ha!

What about Clavascidium?
By: J-Dar
2015-10-28 15:51:12 PDT (-0700)

Do you guys need to update the name change for this species?

Good job!
By: Jason Hollinger (jason)
2015-10-28 15:35:56 PDT (-0700)

Yes, that’s what I’m calling rhizines in P. lacinulatum. Otherwise it is identical to P. squamulosum. (I’m not at all convinced they’re separate species. Sometimes those rhizines are very sparse, apparently intermediate between the two. The range, habitat, etc. are all identical. Anatomy, spores, etc. are all identical. Chemistry too.)

Any time!
By: J-Dar
2015-10-28 14:55:57 PDT (-0700)

In our area, there are two species of Placidium:
Placidium lacinulatum (now Clavascidium lacinulatum) and
Placidium squamulosum

I think I was able to photograph rhizines extending past the dense rhizohyphae, which would make this P. lacinulatum.

Not hourly
By: Jason Hollinger (jason)
2015-10-28 09:05:00 PDT (-0700)

But if you can get me onto one of those ranches some day… ;)

By: J-Dar
2015-10-28 08:30:19 PDT (-0700)

Thanks, I was struggling with the general taxonomic category for this one, it seemed superficially like some Acarospora, then Sarcogyne looked right if I could convince myself that the squamules may actually be apothecia. I’ll take some to the office today and put it under the compound scope and check out the cell structure. Do you charge hourly for your ID’s and explanations?

Common mistake
By: Jason Hollinger (jason)
2015-10-28 08:06:25 PDT (-0700)

Those squamules look an awful lot like apothecia, don’t they?

This is a tricky group. I recommend not worrying too much about finding perithecia or pycnidia. (Although in principle you need both to follow the key in the Sonoran Flora, vol. 2 I think.) The most important characters seem to be microscopic anatomy:

1) This genus has particularly thick cortex with relatively large isodiametric (polygonal to blocky) cells (paraplectenchymatous) in the upper cortex. Compare with Catapyrenium, Heterobasidium, Verrucaria compacta group for example.

2) The medulla usually has at least some large isodiametric cells, but sometimes are mixed with a few to abundant long narrow tangled hyphae (prosoplectenchymatous). This is an important taxonomic character.

3) The lower surface sometimes has “rhizines”. These are very hard to find. It seems best to dampen and gently pluck off a single well-developed squamule with soil still attached below. Dunk this in water and gently clean it off. Rhizines will start to show up quickly as long slender limp ropy structures which don’t detach as readily as the fine weft of cobwebby rhizohyphae surrounding them.

I belabor the point only because I was failing to see them despite looking for them explicitly for years. Learn from my errors and frustration!

Created: 2015-10-27 20:37:58 PDT (-0700)
Last modified: 2015-10-29 13:52:10 PDT (-0700)
Viewed: 90 times, last viewed: 2017-12-12 18:09:49 PST (-0800)
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