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BFNA Title: Coscinodon |
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XX.
COSCINODON Sprengel, Einl.
Stud. Kryptog. Gew. 281. 1804 * [Greek
koskinon,
a sieve, alluding to the peristome] Roxanne I. Hastings Plants
small, 4.5--15 mm, in
dense cushions to loose mats, olive green to dark black-green. Stem leaves
oval to ovate-lanceolate, keeled distally, margins
plane, incurved, or recurved, distal lamina 1- or
2-stratose, specialized laminal and marginal chlorophyllose structures lacking, usually long-awned, mid-leaf cells quadrate to short rectangular,
straight to sinuose, usually thick-walled, basal
cells usually rectangular and smooth walled. Gemmae absent. Sexual condition autoicous
or dioicous; perichaetial
leaves enlarged. Seta short to long, straight. Capsule erect, immersed to exserted,
symmetric, campanulate, ovate or cylindric, with poorly differentiated
annulus, operculum conic to rostrate, falling
detached from the columella. Calyptra
campanulate, becoming cucullate
with age, erose at base, large, covering 1/2 to all
of capsule, plicate. Species
10 (5 in the flora): North America, South America, Eurasia. Species
in the genus Coscinodon
are widespread across North America but are largely absent from the interior
Great Plains and along the west coast. They all prefer dry acidic rocks. The
largely calcareous regions of the continental interior do not provide
suitable habitat for these species. Historically, North American authors have
often considered Coscinodon to be a subgenus
of Grimmia. Not until the 1980's did they
follow the European approach distinguishing these two genera. The separation
of these two genera is largely based on the sporophyte.
Coscinodon
have large, campanulate, plicate calyptra that
commonly cover the capsule, whereas Grimmia have smaller,
non-plicate calyptra that are not campanulate. It is often stated that Coscinodon have very long awns
compared to most Grimmia.
This is true for the widespread species, C.
calyptratus and C. cribrosus, and also C. yukonensis.
But C. arctolimnius
is muticous to short-awned
and C. hartzii
has awns not much longer than most Grimmia. SELECTED
REFERENCES Churchill, S. P. 1981. A phylogenetic analysis, classification and synopsis of the
genera of the Grimmiaceae (Musci).
In: V. A. Funk and D.R. Brooks, eds. 1981. Advances in Cladistics.
New York. Pp. 127--144. Hastings, R.
I. 1999. Taxonomy and biogeography of the genus Coscinodon
(Bryopsida, Grimmiaceae)
in North America, including a new species. Bryologist 102: 265--286. Hastings, R. I. and H. Deguchi.
1997. Taxonomy of Coscinodon arctolimnius (Bryopsida, Grimmiaceae) including a new subspecies from Asia.
Bryologist 100: 50--55. Ireland, R.
R. and H. Crum. 1976. Distribution of Grimmia
cribrosa in North America. Bryologist 79:
355--357. Muñoz,
J. 1998. Amended description of Coscinodon
calyptratus (Grimmiaceae)
and major range extensions into Eurasia and New Zealand. Bryologist 101:
89--92. Murray, B. M. 1992. Bryophyte
flora of Alaskan steppes. Brybrothera 1: 9--33. Steere, W. C. 1978.
The Mosses of Arctic Alaska. Brophyt. Biblioth. 14: 1--508. Steere, W.C.
1974. Grimmia (Coscinodon)
arctolimnia, a new species from Great Bear
Lake, Northwest Territories, Canada. Bryologist 77: 230--234. 1.
Leaves non-plicate; lamina distally 1-stratose; leaf margins plane or
revolute on one side at midleaf. 2. Autoicous; capsule exserted; peristome solid; leaves 1.4--2.4 mm, narrowly ovate-lanceolate, margins plane or revolute on one side at midleaf; western North America . . . 1. Coscinodon calyptratus 2. Dioicous; capsule immersed; peristome
scalloped; leaves 0.9--1.2 mm, broadly ovate-lanceolate,
margins plane; northern British Columbia to Alaska . . . 2. Coscinodon yukonensis 1.
Leaves plicate at least in distal lamina; lamina distally 2-stratose; leaf
margins inrolled distally. 3. Capsule
exserted; peristome
present, xerocastique; leaf plications
never to base; Arctic . . . 5. Coscinodon
hartzii 3. Capsule
immersed; peristome present and hygrocastique
or absent; leaf plications variable; temperate to
Arctic. 4. Peristome present; leaf margins incurved distally, never cucullate, plications not
always reaching base; apex frequently long-awned;
plants dark olive green; temperate to Arctic . . . 3. Coscinodon
cribrosus 4. Peristome absent; leaf margins incurved distally, apex
often cucullate if muticous,
inrolled if awned; plications extending to base; often muticous
or with short awns; plants dark black-green; Arctic . . . 4. Coscinodon arctolimnius 1.
Coscinodon calyptratus (Hooker) C. E. O. Jensen, Eur. N. Amer. Bryin. 2: 241.
1897 Grimmia calyptrata Hooker, Musci
Americani n. 60. 1828; Grimmia
columbica Kindberg; Coscinodon hookeri
Hampe Plants
7--10 mm, olive green.
Stem leaves ovate to ovate-lanceolate,
1.4--2.4 × 0.4--0.7 mm, margins plane or one margin revolute at mid-leaf,
apex plane, awn 0.4--1.4 mm, lamina non-plicate; distal laminal
cells 1-stratose; medial laminal cells 1-stratose; juxtacostal basal laminal cells
long-rectangular, 15--80 × 7--10 µm, evenly thin-walled; marginal basal laminal cells quadrate to long-rectangular, 16--60 × 7--15
µm, thin or thick end walls and thin lateral walls. Sexual condition autoicous. Seta 1.4--2.4 mm. Capsule exserted, cylindrical, commonly constricted at rim; peristome present, solid, xerocastique.
Most
common on dry sandstone and granitic boulders and
bedrock exposures but also limestone and volcanic outcrops; 300--3000 m;
Alta., B.C.; Ariz., Calif., Colo., Idaho, Minn., Mont., Nev., N.Mex., Oreg.,
S.Dak., Utah, Wash., Wis., Wyo.; Asia (Armenia, Kazakstan,
Pakistan). Coscinodon calyptratus is common and widespread in the dry
interior mountain areas of western North America. To the east it is largely
bounded by the front ranges of the Rocky Mountains and acidic outliers such
as the Black Hills of South Dakota. Two disjunct
sites in Wisconsin and Minnesota define the eastward extent of the species.
It is not found along the west coast mountains. The species is endemic to
North America. Specimens reported from central Asia and New Zealand by J. Muñoz (1998) are in error. The
former is an undescribed species of Coscinodon and
the latter is a Grimmia.
The non-plicate, 1-stratose leaves
with plane or one revolute margin, and exserted
capsule, clearly separate this species from all other North American Coscinodon. The autoicous
sexual condition of this species is unique for the genus but is often
difficult to ascertain on any particular specimen. This species is most
commonly confused with Grimmia longirostris (formerly
G. affinis)
than any other species of Coscinodon. Both species are autoicous,
have a similar robust habit, have leaves that are strongly keeled and may
have recurved margins and have long-exserted capsules. If fertile and with capsules the
species are easily distinguished as C. calyptratus has large, plicate calyptra
and has a thin-walled filmy annulus. In contrast, G. longirostris has smaller, smooth calyptra and a large, prominent annulus. Gametophytically C.
calyptratus has 1-stratose areolation across
the distal and medial lamina except for a 2-stratose margin. Its basal cells
tend to be evenly thin-walled. Grimmia longirostris has a 2-stratose distal lamina and a
wide 2-stratose margin at mid-leaf. Its basal cells tend to be thicker
walled. 2.
Coscinodon yukonensis R. I. Hastings, Bryologist 102: 278.
1999 Plants 7--10 mm, dark brown green. Stem
leaves broadly ovate-lanceolate, 0.9-1.2 × 0.4
mm, margins plane, apex plane, awn 0.2--1 mm, lamina non-plicate; distal laminal cells 1-stratose; medial laminal
cells 1-stratose; juxtacostal basal laminal cells rectangular to long-rectangular, 27--51 × 8--12
µm, thin- to thick-walled; marginal basal laminal
cells oblate to quadrate, 5--12 × 9--12 µm, evenly thick-walled. Sexual
condition dioicous. Seta 0.3--0.5 mm. Capsule
immersed, cupulate; peristome
present, scalloped, xerocastique. Only
known from siliceous or granite-slate outcrops; 1500--1700 m; B.C., Yukon;
Alaska. R.
I. Hastings (1999) recently described this species, which is known only from
northwestern North America. The specimens were all originally identified as C.
cribrosus, which it resembles in its immersed
capsules and superficially cribrose peristome teeth. However, C. yukonensis
is separated by its xerocastique peristome (i.e., opens when dry) and non-plicate, plane margined, 1-stratose leaves. Additionally, unlike C. cribrosus, the peristome
teeth are not perforated, rather the ornamentation has been "scalloped
out" down to the cell walls on either side of the teeth. Thus, while
superficially appearing perforated, the cell walls are intact. Its leaves
resemble those of C. calyptratus but they
are much smaller, more broadly ovate, and are never revolute. Additionally it
has an immersed capsule and the teeth are scalloped, not solid as in C. calyptratus. The marginal basal laminal
cells are oblate to quadrate, unlike any other Coscinodon
in North America. 3.
Coscinodon cribrosus (Hedwig) Spruce, Ann. Mag. Nat. Hist. Ser. 2, 3: 491.
1849 Grimmia cribrosa Hedwig, Spec. Musc.
Frond. 76. 1801; Coscinodon pulvinatus Sprengel; Coscinodon persoonii
Hampe Plants 4.5--7 mm, dark olive green. Stem
leaves oval to ovate-lanceolate, 1.1--1.9 × 0.4--0.7
mm, margins incurved distally, apex plane, awn 0.1--1.1 mm, lamina 2-plicate,
plications not always reaching base; distal laminal cells 2-stratose; medial laminal
cells 1-stratose; juxtacostal basal laminal cells quadrate to long-rectangular, 20--47 × 8--12
µm, evenly thick-walled; marginal basal laminal
cells quadrate to rectangular, 12--34 × 6--12 µm, thin or thick end walls and
thin lateral walls. Sexual condition dioicous.
Seta 0.8--1.2 mm. Capsule emergent, ovate to campanulate; peristome present,
cribrose, hygrocastique. Acidic,
dry sandstone, shale, and granitic boulders and
bedrock exposures but also found on volcanic outcrops and granodiorites;
0--3300 m; Greenland; Alta., B.C., Nfdl. and Labr., N.W.T., Nunavut, Ont., Que., Yukon; Alaska, Ariz.,
Colo., Maine, N.Mex., N.Y., S.Dak., Tenn.; Eurasia. Coscinodon cribrosus
is an uncommon moss known from widely disjunct
sites across North America. It has been suggested that this distribution is
due to a restricted occurrence on mineral rich rocks. The sites from
Ellesmere Island, Tennessee, Colorado, South Dakota, Thunder Bay and Alaska
support this contention as they are all reported to be either heavy metal or
copper-bearing deposits or the specimens are associated with the
"copper-moss," Mielichhoferia mielichhoferi. However, specimens in other areas have
been collected on sandstones and shales. The
species appears to be largely controlled by the extent of the Cretaceous epicontinental seaway that flooded much of central North
America from the Gulf of Mexico to the Yukon (R. I. Hastings 1999). The
species does not occur within the boundaries of the seaway except on isolated
granodiorite outcrops that were exposed subsequent
to the retreat of the seaway. Coscinodon cribrosus is recognized by its 2-plicate, 2-stratose
leaves with incurved margins and emergent capsule with a well-developed cribrose peristome. It is the
only species of Coscinodon that has a hygrocastique peristome, i.e.
its peristome opens when wet and is closed when
dry. 4.
Coscinodon arctolimnius (Steere) Steere, J. Hattori Bot. Lab.
42: 446. 1977 Grimmia arctolimnia Steere, Bryologist 77: 230. 1974 Plants 5--10 mm, dark black-green. Stem
leaves ovate-lanceolate, (0.8--)1.5--1.8 × (0.3--)0.6--0.8
mm, margins incurved distally, apex often cucullate,
awn 0.3--0.5 mm or absent, lamina 2-plicate; distal laminal
cells 2-stratose; medial laminal cells patchy
2-stratose; juxtacostal basal laminal
cells short-rectangular, 19--33 × 9--13 µm, evenly thick-walled; marginal
basal laminal cells quadrate to short-rectangular,
13--27 × 9--13 µm, evenly thin-walled. Sexual condition dioicous. Seta 0.3--0.5 mm. Capsule
immersed, ovoid to campanulate; peristome
absent. Subspecies
2 (1 in the flora). Mineralized
siliceous rock; 160 m; N.W.T.; Asia (Pakistan, Mongolia). Until
1996, Coscinodon arctolimnius
was considered to be endemic to the eastern shore of Great Bear Lake in the
Northwest Territories of Canada. W. C. Steere
(1974) suggested that the species evolved in this site as a result of radiation
induced genetic mutations on a population of C. cribrosus.
However, with the discovery of the new subspecies (R. I. Hastings and H. Deguchi 1997) C. arctolimnius
subsp. higuchi,
from both Pakistan and Mongolia, it appears that the species has a much wider
distribution. Although undoubtedly closely related to C. cribrosus, there is now no reason to assume that the
species evolved in North America. The Asian subspecies is distinguished in
part by a smaller leaf size, longer awns, more commonly cucullate
apex, and details of the structure of the plications.
Coscinodon arctolimnius
is separated from other North American Coscinodon
by its green-black color, cucullate leaf apex
(incurved if awned), and by the absence of a peristome. 5. Coscinodon hartzii C. E. O. Jensen, Mosser
fra-Ost Grønland. Medd. Grønland 15: 422. 1897 Plants
10--15 mm, pale olive
green. Stem leaves oval to ovate-lanceolate,
1.1--1.6 × 0.3--0.6 mm, margins incurved distally, apex plane, awn 0.1--0.6
mm, lamina 2-plicate, plications never extended to
base; distal laminal cells 2- to 3-stratose; medial
laminal cells 1-stratose; juxtacostal
basal laminal cells rectangular to
long-rectangular, 21--55 × 9--12 µm, evenly thick-walled; marginal basal laminal cells quadrate to long-rectangular, 12--51 × 9--15
µm, thin or thick end walls and thin lateral walls. Sexual condition dioicous. Seta 1.5--1.8 mm. Capsule exserted, cylindrical; peristome
present, cribrose, xerocastique.
Shale,
slate, and granitic rock in tundra; 980--1700 m;
Greenland; Yukon; Alaska. Coscinodon hartzii is endemic to Arctic regions of North
America. Until 1992, this species was known only from its type locality at
Scoresby Sound in e Greenland. B. M. Murray (1992) reported collections from
Mt. Michelson and the Philip Smith Mountains of Alaska. W. C. Steere's (1978) and J. Muñoz's
(1998) citations of C. calyptratus from
these sites have turned out to be C. hartzii.
A new location in se Yukon suggests that this species may be widespread
across northern North America. Coscinodon
hartzii is recognized by its weakly 2-plicate
leaves coupled with an exserted capsule and cribrose peristome. It commonly
also has 3-stratose regions in the distal parts of its stem leaves. |
