Taxacom: Calcisphaera Williamson, 1880 - microfossil incertae sedis (Calcitarcha) or charophyte?

[Tony Rees]

I am seeking an answer as to whether the calcified microscopic fossil genus
Calcisphaera Williamson, 1880 (treated mainly as a botanical form) should
be treated as a microfossil incertae sedis (Calcitarcha) or assigned to
charophyta (as representing a charophyte spore aka gyrogonite). Williamson,
1880 originally assigned 7 species to the genus but failed to designate a
type; of these, C. laevis (and possibly all of the others but one) is today
considered a calcisphere microfossil in the group Calcitarcha, while C.
robusta is considered a charophyte spore. The correct assignment of the
genus therefore turns on which species is considered the type.

Andrews (1955 and 1970) in "Index of Generic Names of Fossil Plants" gives
the type as C. laevis, however Index Nominum Genericorum gives the type as
C. robusta following Miller, 1889 who designated that species as the
lectotype. Apparently Andrews' designation (which was subsequently
supported by Peck & Morales, 1966 and Grambast-Fessard et al., 1989)
followed "Article PB. 4 of the [then current] International Code of
Botanical Nomenclature" which states: "The type of a genus of fossil plants
is the first described species which shows such characters as are necessary
for distinguishing the genus from other taxa."" (that text from Peck &
Morales, 1966), thus according to that logic, Miller's designation of C.
robusta as the type was not only unnecessary but invalid.

However subsequently Samoilova, 1985, in a proposal to Taxon, recognised
Miller's designation of C. robusta as the type and treated Calcisphaera as
a charophyte genus, with apparent priority over another genus, Trochiliscus
Karpinsky, 1906, if the two genera are treated as synonymous. Bu in a
response to that proposal, Grambast-Fessard et al., 1989 stated: "The taxon
Calcisphaera has not been retained [in Charophyta] as it includes species
belonging to distinct taxonomic units; the first one described, C. laevis,
designated as the type species, is not a charophyte but belongs to the
animal kingdom (Peck and Morales, 1966: 314)."

Later, Versteegh et al., 2009, on formally proposing the group Calcitarcha,
noted the earliest forms to be those described by Williamson, 1880
as Calcisphaera, and included that genus name in their list of Calcitarcha
genera without further comment regarding its typification.

Currently AlgaeBase offers a confused statement: it recognises Calcisphaera
as a charophyte, with C. robusta as type species, but references
Grambast-Fessard et al., 1989 as the most recent treatment followed (in
fact as stated above, those authors state the exact opposite).

So the question arises, does the current (or perhaps even a former)
botanical Code support Peck & Morales, 1966 assertion that in fossil plants
where no type is selected, the first mentioned species automatically
becomes the type? That statement appears to originate in the Paris Code
(1956), probably also in the 1952 Code, which indeed states:
"Article PB. 4. The type of a genus of fossil plants is the first described
species which shows such characters as are necessary for distinguishing the
genus from other taxa. The type of a species of fossil plants is the first
described and figured specimen showing such characters as are necessary for
distinguishing the species from other species." (
https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.iapt-taxon.org%2Fhistoric%2F1956.htm&data%7C02%7Ctaxacom%40lists.ku.edu%7Cd5b0204b442648c163a008dddbbfcc16%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638908339008342760%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdataœZ1Pq9o3NuL%2BgRM9hSOtKbAfVc%2Bh893roLgo5JsdFM%3D&reserved=0)

So Andrews in 1955 would (according to my reading) be correct in using C.
laevis as the tye species and ignoring Miller's subsequent designation of
C. robusta.

However I am not sure that is the situation today; the current ICNafp does
not seem to contain this Article or wording; the nearest I can find (which
is not specifically dealing with fossil plants is:
10.5. The author who first designates (Art. 7.10, 7.11, and F.5.4) a type
of a name of a genus or subdivision of a genus must be followed, but the
choice may be superseded if the author used a largely mechanical method of
selection (Art. 10.6). A type chosen using a largely mechanical method of
selection is superseded by any later choice of a different type not made
using such a method, unless, in the interval, the supersedable choice has
been affirmed by its adoption in a publication that did not use a
mechanical method of selection.

(A "mechanical method of selection" appears to comprise taking the first
species listed).

So where does this leave us? Is C. laevis or C. robusta the correct type
for this genus, and accordingly, is it to be treated as Calcitarcha or
Charophyta? (If indeed it is to be placed as a charophyte, then C. laevis
and other similar species would require a new generic name in order to be
placed in the Calcitarcha).

Your answers appreciated,

Regards - Tony Rees, Interim Register of Marine and Nonmarine Genera
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References in chronological order:

Williamson, W.C. (1880). On the organization of the fossil plants of the
coal-measures.?Part X. Including an examination of the supposed
radiolarians of the carboniferous rocks. Philosophical transactions of the
Royal Society of London 171(2): 493-539, plates 14-21.
Available at
https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Froyalsocietypublishing.org%2Fdoi%2Fepdf%2F10.1098%2Frstl.1880.0014&data%7C02%7Ctaxacom%40lists.ku.edu%7Cd5b0204b442648c163a008dddbbfcc16%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638908339008386083%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=pqMZuSCAIZKFaIP9xeQ%2FM26ZvLpwGYc3dsc07uUzDrg%3D&reserved=0

Miller, S.A. (1889). North American geology and palaeontology for the use
of amateurs, students, and scientists. pp. 664, 1194 figures. Cincinnati:
Western Methodist Book Concern.

Andrews, H.N. (1955). Index of generic names of fossil plants, 1820?1950.
U.S.. Geological Survey Bulletin 1013: 1?262

Peck, R.E. and Morales, G.A. (1966). The Devonian and Lower Mississippian
charophytes of North America. Micropaleontology, 12(3), pp.303-324.
doi:10.2307/1484549

R. B. Samoilova (1985). (781) Proposal to Conserve Trochiliscus against
Calcisphaeria and Moellerina (Fossil, Trochiliscaceae). Taxon, 34(1),
157?158. doi:10.2307/1221585

N. Grambast-Fessard, M. Feist and Z. Wang. (1989). Concerning Rejected
Proposal 781 to Conserve Trochiliscus (Fossil Charophyta). Taxon, 38(4),
641?643. doi:10.2307/1222654

Versteegh, G.J., Servais, T., Streng, M., Munnecke, A. and Vachard, D.
(2009). A discussion and proposal concerning the use of the term
calcispheres. *Palaeontology*, *52*(2), pp.343-348.
 doi:10.1111/j.1475-4983.2009.00854.x

AlgaeBase (2025). Calcisphaera W.C. Wiiliamson, 1880:
https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.algaebase.org%2Fsearch%2Fgenus%2Fdetail%2F%3Fgenus_id%3D53072&data%7C02%7Ctaxacom%40lists.ku.edu%7Cd5b0204b442648c163a008dddbbfcc16%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638908339008400646%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=JDLNeQU31pD7f7j0ANmTbNNTxa1Gx%2BM7zOzUdel6XGo%3D&reserved=0