Re: TYPE specimens (kinda long)

Charles Powell (
Fri, 20 Oct 1995 12:51:28 -0500

Hi Fernando (and everyone else who's interested)-

In reading your discussion about type specimens I wonder isn't there some
kind of Code of Botanical Nomenclature? If there is that should answer all
your questions. I know, there is one for Zoological and Stratigraphic
Nomenclature and my comments are based on an interpretation of the first of

When describing a new taxon a single holotype is picked as a "name holder"
for that taxon. The description is then based on a whole series of
specimens which (hopefully) show the range of variability exhibited by that
species population, but the holotype is generally considered an "average"
specimen. Specimens which show variations from the "average" specimen are
designated paratypes. The description of the new taxon is based on all the
specimen available (a population, or even a number of populations) and
include all variability, usually as ranges in size, shape, or whatever
(i.e. between 2 and 10 mm long). The following is an example of a new
fossil Atrina (clam shell) from a manuscript I've recently submitted for
publication which shows what I mean.
Diagnosis.--Shell about average size for genus with a straight dorsal
margin and "S"-shaped ventral margin and minor external sculpture.
Description.--Shell is ham-shaped, with a straight dorsal margin and a
slight "S"-shaped ventral margin. The umbones are moderately pointed and
generally unornamented. The ventral slope shows slight raised ridges which
correspond to previous growth of the ventral margin, whereas the posterior
slope is smooth, showing only fine growth lines. The dorsal margin of the
shell has two to possibly five ridges which extend from above the umbones
to the posterior slope and then become obscure. Specimens are generally
flattened, but appear to have been moderately inflated. The interior of
the valve was not observed. The holotype is about 140 mm long, 84.2 mm
wide, with an undetermined thickness because the specimen has been crushed.

Discussion.--Atrina rosewateri n. sp. appears most similar to a specimen
of A. (Servatrina) pectinata illustrated by Rosewater (1961, pl. 161, figs.
1, 2). Atrina pectinata occurs in the Indo-Pacific from Sri Lanka and
India west to Australia, Indonesia, and Japan, from the Pliocene to
Holocene. Except for the larger size of A. pectinata and minor details of
the sculpture, including more abundant radial ribs, usually with minute
spines, the Imperial Formation specimens are nearly indistinguishable from
the specimen illustrated by Rosewater. Another closely related species is
the Holocene A. oldroydi Dall, 1901, from southern California to Baja
California Norte, which differs in having radial ribs on the posterior
slope and in having a shorter more rounded dorsal margin. Atrina stephensi
Hanna from the Imperial Foramtion in Imperial County is similar but can be
easily distinguished by its concave dorsal margin.

For clarification the "Diagnosis" briefly tells the reader how this new
species can be distinguished from other taxa in the genus. The
"Discussion" section to compare the new taxa to similar taxa which don't
necessarily have to be in the same genus (although usually are) and/or give
ecological data, etc.

I think I've answered your first two questions and the last, above. In
response to the third... First, if more than one type specimen is present
they are called syntypes (formerly called co-types). Someone will come
along later a pick one of them as a lectotype (preferably a syntype that
has been previously illustrated) and that will be the new "holotype." If
among the syntypes there is more than one taxa present then the first
reviewer decides which specimen represents what the original author
intended and that is given the original name and the taxon will be
redefined to exclude other taxa. The other specimens can then be named
whatever you wish.

Hope this helps.

Charles Powell, II
Paleontology & Stratigaphy
U. S. Geological Survey
345 Middlefield Rd.
Menlo Park, CA 94025
Tel.: 415-329-4985