Herpetological Review 42(3), 2011
339pointS of view     
 Although scientific names are the accepted means of refer-
ring to species in the scientific literature, common names con-
tinue to serve important functions in both scientific and popular 
communication. That fact is evident from the inclusion of both 
scientific and common names in checklists published by vari-
ous taxonomically specialized scientific societies (e.g., American 
Ornithologists? Union 1998 [birds]; Baker et al. 2003 [mammals]; 
Crother et al. 2008 [amphibians and ?reptiles?]; Nelson et al. 2004 
[?fishes?]). In this context, a relatively minor yet somewhat radi-
cal change concerning the use and formation of common names 
in a recent checklist of iguana species (Iguana Taxonomy Work-
ing Group 2011) deserves explanation. The change is minor in 
that it involves only a single letter, ?s,? reflecting the plural in-
stead of singular nature of each name, but it is radical in that 
it affects the names of all species in the checklist and breaks a 
long-standing tradition. A description of the rationale for this 
change was outside of the scope of the checklist, and therefore 
I, as the instigator, am presenting the rationale here. I hope to 
convince herpetologists (and biologists in general) that the tra-
ditional use of singular common names as the equivalents of the 
scientific names of species is inconsistent with modern species 
concepts and the meanings of the words from which the names 
are formed, and therefore, that plural common names should be 
used instead. Although some may consider the inconsistency to 
be insignificant (and thus the proposed solution to be one to a 
?non-problem?), it reflects a fundamental and inappropriate as-
sumption about the basic nature of taxa.
 The term ?common? (in ?common name?) is used here to 
mean ?ordinary? or ?familiar? (as opposed to ?widespread? or 
?general?) in the sense of being composed of ordinary or famil-
iar words; it is therefore roughly synonymous with ?vernacu-
lar,? meaning ?of the everyday language or dialect of a group of 
people.? The common names used by different groups of people 
can be distinguished by specifying a region, country, or language 
(e.g., ?English common names?). Other properties of common 
names can also be conveyed by using appropriate adjectives 
(e.g., ?standard English names? for English common names pro-
posed in an attempt to standardize usage). I will restrict consid-
erations in this commentary to English common names, though 
they likely apply to those of other languages. With one excep-
tion, I will also restrict my comments and examples to names of 
amphibian and reptile species, though they obviously apply to 
those of other taxa as well.
MODERN SPECIES CONCEPTS AND THEIR IMPLICATIONS 
FOR COMMON NAMES
 Although debate continues concerning the precise definition 
of the species category (reviewed by de Queiroz 1998; Mayden 
1997; Wilkins 2006), all modern species concepts equate species 
more generally with population level lineages?that is, with pop-
ulations or metapopulations (groups of connected populations) 
that extend through time as the result of ancestry and descent 
among their component organisms (de Queiroz 1998, 1999, 
2007). Implicit in this general concept of species is the view that 
the species category is a level in the hierarchy of biological or-
ganization (Brown 1995; de Queiroz 2011; Mayr 1982), which in-
cludes at least cells, organisms, colonies, and populations/spe-
cies, and perhaps entities at lower levels (e.g., genes) and higher 
levels (e.g., communities) as well. In this hierarchy of biological 
organization, entities at higher levels (e.g., species) are made up 
of those at lower levels (e.g., organisms). 
 In agreement with the recognition of a hierarchy of biological 
organization, different names are usually used for entities that 
occupy different hierarchical levels. For example, ?Lonesome 
George? is the name of an organism that is part of the species 
named ?Chelonoidis (formerly Geochelone) abingdonii.? The 
common names of species, however, are often used in a way that 
is inconsistent with such distinctions; that is, the same common 
names are often used to refer both to individual organisms and 
to the species of which they are parts. For example, it would not 
be unusual for someone to say, ?I saw a zebra-tailed lizard near 
Pisgah Crater in the Mojave Desert,? using the name ?zebra-
tailed lizard? to refer to an individual organism. It would also not 
be unusual for someone to say, ?The zebra-tailed lizard occurs in 
the Mojave Desert,? using the same name, including the singular 
number, to refer to an entire species. This second use, however, 
is inconsistent with modern species concepts and the meanings 
of the words from which the common name is formed. 
 The common names of amphibian and reptile species are 
often formed by adding adjectives (e.g., ?red-cheeked,? ?So-
noran?), including participles (e.g., ?barking?) and attributive 
nouns (e.g., ?canyon,? ?rat?), or possessive nouns (e.g., ?Baird?s?) 
to base names. Those base names?words such as ?frog,? ?sala-
mander,? ?turtle,? ?lizard,? ?snake,? and ?alligator??are common 
nouns in that they refer to the members of groups of organisms. 
Those groups are now commonly conceptualized as the classes 
or sets of organisms that make up particular clades, or some-
times paraphyletic groups (e.g., ?lizards?). A snake, for example, 
is an individual organism; it is an individual member of the set 
of organisms making up the clade Serpentes or Ophidia. There-
fore, when we refer to a single organism in this set, we use the 
singular noun ?snake? (e.g., ?Amy anaesthetized a snake before 
performing surgery on it?), and when we refer to several such 
organisms, we use the plural noun ?snakes? (e.g., ?Steve has been 
radio-tracking 10 snakes at the same time?).
 When common names are formed using common nouns of 
the kind just described, it is inconsistent to use the singular form 
of those names as equivalents of the scientific names of species. 
The reason that this use is inconsistent is that singular common 
names properly refer to individual organisms, not to entire spe-
cies, whereas scientific names of species properly refer to en-
tire species, not to individual organisms. A zebra-tailed lizard, 
for example, is not a species; it is an organism that is a member 
kevin de QueiroZ
Division of Amphibians and Reptiles, National Museum of Natural History,
Smithsonian Institution, Washington, DC 20560-0162, USA
e-mail: dequeirozk@si.edu
Herpetological Review, 2011, 42(3), 339?342.
? 2011 by Society for the Study of Amphibians and Reptiles
plural versus Singular common names for  
Amphibian and reptile Species
Herpetological Review 42(3), 2011
340      pointS of view
or part of a species (Callisaurus draconoides). Conversely, Cal-
lisaurus draconoides is not a lizard, zebra-tailed or otherwise; it 
is a species the organismal parts of which are (zebra-tailed) liz-
ards. Therefore, because species are almost always composed of 
more than one organism, the name ?Callisaurus draconoides? is 
not equivalent to ?[the] zebra-tailed lizard? but to ?zebra-tailed 
lizards.? And thus, the incorrectly stated sentence ?The zebra-
tailed lizard occurs in the Mojave Desert,? is correctly stated 
using either a singular species name: ?Callisaurus draconoides 
occurs in the Mojave Desert,? or a plural common name: ?Zebra-
tailed lizards occur in the Mojave Desert.? 
 Interestingly, the problem I am discussing is largely restrict-
ed to the common names of species. Analogous inconsisten-
cies involving the common names of higher taxa (clades) are 
rare to non-existent. For example, it is not customary to equate 
the name ?Squamata? with ?[the] lizard? but with ?lizards.? Nor 
is it customary to equate ?Phrynosoma? with ?[the] horned liz-
ard? but with ?horned lizards.? Nevertheless, it is customary to 
equate ?Phrynosoma solare? with ?[the] regal horned lizard,? 
though consistency dictates that we ought to equate it with 
?regal horned lizards.? All of the taxa just mentioned, whether 
clades or species, are composed of more than one organism. 
SCIENTIFIC NAMES AND COMMON NAMES OF SPECIES
 In contrast to English common names, the scientific names 
of amphibian and reptile species (as well as those of species in 
other clades) are commonly formed from Latin or Latinized 
words. Those words are often common nouns in their original 
language (e.g., ?rana? is Latin for ?frog?), but as scientific names, 
they are treated differently. In both popular and scientific dis-
course, the scientific names of species are commonly used in 
the singular, implying that they refer to species as wholes rather 
than to the organismal parts of species. In agreement with the 
treatment of scientific species names as singulars, several au-
thors have argued that the scientific names of species are proper 
nouns (e.g., Ghiselin 1974; Hull 1976). Proper nouns, by defini-
tion, refer to individual entities (in this case, particular species) 
and thus are necessarily singular. Given that scientific names are 
singular, it is correct to say ?Plethodon petraeus has a restricted 
distribution? but incorrect to say ?Plethodon petraeus have a re-
stricted distribution.? 
 The use of scientific names as proper nouns is perhaps most 
natural in languages that are relatively distantly related to Latin 
(e.g., English and German more so than Spanish and Italian). Be-
cause the Latin or Latinized words from which scientific names 
are formed are more likely to be unfamiliar to speakers of such 
languages, it is natural to treat them as proper nouns, that is, 
as words (names) that simply refer to individual things, rather 
than common nouns, which refer to sets or classes of individual 
things and therefore often describe properties possessed by the 
members of those sets or classes. Just as the name ?Doris Co-
chran? simply refers to a particular person, the name ?Apalone 
mutica? simply refers to a particular species. That the name 
?Doris Cochran? means ?of the sea? and ?red? or ?crimson? and 
the name ?Apalone mutica? means ?soft? and ?unarmed? is ir-
relevant to their functions of referring to an individual person or 
species. That is to say, scientific names can be (and perhaps of-
ten are) used to refer to particular species regardless of whether 
the users of those names know or care about the meanings of the 
Latin or Latinized words from which the names are formed. Con-
sequently, scientific names need not be descriptively accurate. 
For example, just as the name ?George? works perfectly well for 
referring to a person who is not a farmer, the name ?Coluber 
constrictor? works perfectly well for referring to a species whose 
members do not commonly constrict their prey.
 Like the scientific names of species, the common names of 
species are sometimes interpreted as proper nouns (e.g., Parkes 
1978; Potter 1984). That interpretation, however, is inconsistent 
with certain practices involving common names. Rather than 
simply referring to species, common names often describe one 
or more properties of species or their component organisms. 
This situation is reflected in changes in common names to im-
prove their descriptive accuracy, a practice that is expressly for-
bidden with scientific names. For example, the common name 
?poison arrow frog? was changed to ?poison dart frog? (and ?dart-
poison frog?), and the names ?Mexican hook-nosed snakes? and 
?plateau hooked-nosed snakes? were changed to ?eastern hook-
nosed snakes? and ?western hook-nosed snakes? (Crother et al. 
2008), in all cases to improve descriptive accuracy. In contrast, 
the name ?Coluber constrictor? cannot be changed for the sake of 
improving descriptive accuracy. Although that rule is imposed by 
a formal system of zoological nomenclature, which does not ap-
ply to common names, the way that the system operates reflects 
the fact that the primary function of scientific names is simply 
for referring to taxa and not for describing the properties of their 
included organisms.  
 The interpretation of common names as proper nouns is also 
inconsistent with the meanings of the words from which they are 
formed. Because the base words from which common names are 
formed are common nouns (e.g., ?gecko?), modifying them with 
descriptive adjectives (e.g., ?banded?) and/or possessive nouns 
(e.g., ?Switak?s?) creates names that are also common nouns. De-
claring them to be proper nouns or capitalizing them does not 
change that fact. Using them in the singular goes further toward 
making them function as proper nouns in that the species to 
which they refer are individual population level lineages; how-
ever, many uses of common names in the singular are incon-
sistent with their interpretation as proper names of species. For 
example, the statement ?The Eastern Red-backed Salamander 
is a small species? is either incorrect or incorrectly stated. If the 
name ?Eastern Red-backed Salamander? is the name of a spe-
cies, that species (Plethodon cinereus) is not small: It has an ex-
tensive geographic distribution (Highton and Webster 1976), and 
its component organisms are extremely abundant, resulting in a 
high species biomass (Burton and Likens 1975). Alternatively, if 
the statement is about the average body size of the salamanders 
that make up the species and not about the species as a whole, 
then the proper name of the species should not be used. That is, 
it would be more appropriate to say ?Eastern red-backed sala-
manders are small animals.? Again, this confusion results from 
using a word that refers to a kind of organism as the name of a 
species. 
USE OF SINGULAR COMMON NAMES AS A HOLDOVER
 The likely explanation for the inconsistent but traditional 
use of singular common names for species is that it is a holdover 
from an earlier age. This practice originated in the pre-evolu-
tionary era (see Daudin 1802?03 and Shaw 1802 for French and 
English examples), when species were conceptualized at least 
partly as essences or types (e.g., Hull 1965; Mayr 1976, 1982). 
Species were also conceptualized as self-perpetuating groups of 
organisms (de Queiroz 2011); however, without the principle of 
Herpetological Review 42(3), 2011
341pointS of view     
evolution, the similarity and reproductive compatibility among 
their members was explained by their being of the same essence 
or type in the mind of their creator (Darwin 1859). Under es-
sentialism, the name of a species is the name of an essence, an 
eternal, abstract Idea or Form of which living organisms are its 
concrete manifestations (Hull 1965). Under typology, a species is 
a type, a class or category of entities (i.e., a group defined by a set 
of shared characteristics) of which organisms are its instances or 
examples. In either case, the essence or type of a species consists 
of those properties that are necessary and sufficient for species 
membership, and traditionally, those properties took the form of 
organismal traits (de Queiroz 1992, 1995; Sober 1980). Thus, spe-
cies were conceptualized either as eternal, ideal organisms (es-
sentialism) or as categories of organisms (typology). Also associ-
ated with these views is the idea that any traits that vary among 
the members of a species are incidental or accidental, since they 
are not important to the essence or type of the species. 
 The perspective just described contrasts with modern spe-
cies concepts, according to which species are viewed not as es-
sences or types but as population level lineages. That is to say, 
species are viewed as entities at a level of biological organization 
above the level of organisms, rather than as kinds or categories 
of organisms (and nothing more). Thus, under modern species 
concepts, organisms are parts or components of species rather 
than examples, instances, or manifestations of them. In addi-
tion, the organisms of a species are not required to share any 
particular set of traits (though they often do), and traits that vary 
among them are not viewed as intrinsically any less important 
than those that happen to be fixed. Moreover, as entities at a 
higher level of biological organization, species possess proper-
ties unique to the population level (e.g., population structure) in 
addition to the properties of their component organisms (e.g., 
body size). These and related views have been termed ?popula-
tion thinking? and are in contrast with those of essentialism and 
typology (e.g., Mayr 1959, 1976; O?Hara 1997; Sober 1980).
 The use of singular common names in situations that, un-
der modern species concepts, call for the use of plurals can be 
understood as a vestige of essentialist or typological species 
concepts. According to those doctrines, particularly when or-
ganismal traits are treated as the essential or defining characters, 
the name of a species (whether scientific or common) refers to 
a single organism: the single eternal, ideal organism of which 
tangible organisms are concrete manifestations, or the single 
concept of an organism possessing the properties that define the 
class of which actual organisms are examples or instances. To the 
extent that the essence or type of a species is conceptualized as 
an organism, it is appropriate to use singular common names, 
such as ?the wood turtle,? to refer to essentialist or typological 
species. Thus, the inappropriate use of singular common names 
based on terms that refer to organisms (e.g., ?frog,? ?turtle,? etc.) 
can be explained as a holdover from an era in which species were 
conceptualized as essences or types.
THE COMMON NAMES OF HOMO SAPIENS
 Interestingly, people are less prone to using singular com-
mon names inappropriately when referring to our own species. 
Thus, we rarely, equate the scientific name ?Homo sapiens? with 
the singular common names ?[the] human? or ?[the] human be-
ing;? instead, we use the plural common names ?humans? and 
?human beings.? For example, it would be normal to say, ?Hu-
mans (Homo sapiens) are bipedal primates,? but it would sound 
archaic to say, ?The human (Homo sapiens) is a bipedal primate.? 
Sometimes the singular common name ?man? is used, though 
this practice is decreasing, presumably because it has inappro-
priate connotations with regard not only to number (singular 
versus plural) but also to gender. The singular common names 
?mankind? and ?humankind? are also used. Those names, how-
ever, refer to the human species as a whole or the totality of 
human beings. Unlike the common names of amphibians and 
reptiles, they are never used to refer to individual people. For ex-
ample, although one might say, ?Henry is a tuatara who became 
a father at the age of 111,? one would not say, ?Leonard Stejneger 
was a mankind who published a monograph on the herpetology 
of Japan.? Because we have different common names for refer-
ring to our own species as a whole and the organisms of which 
it is composed, inappropriate use of the singular ?human? to re-
fer to the human species as a whole is rare. In contrast, because 
humans have not developed separate common names for dis-
tinguishing between other species and their component organ-
isms, inappropriate use of singular common names is not only 
common, it is the norm. 
 These patterns of use suggest that humans are less typo-
logical when referring to our own species than when referring 
to other species. Perhaps the reason is that we grant more im-
portance to, or are more aware of, differences among individual 
humans than differences among the individual organisms of 
other single species. But regardless of the reason for this differ-
ence, the common names of other species, including those of 
amphibians and reptiles, ought to conform to the same stan-
dards that we adopt for the names of our own species. One way 
to achieve this would be to develop common names that clearly 
refer to other species as wholes rather than to their component 
organisms. For example, we could use names such as ?the ma-
rine iguana species? or ?marineiguanakind? for Amblyrhynchus 
cristatus. Up to the present time, however, such names have not 
been widely used for species other than Homo sapiens. As long as 
we continue to use common names that refer to kinds of organ-
isms (i.e., names formed from base words such as ?toad,? ?newt,? 
?tortoise,? ?iguana,? ?boa,? and ?crocodile? without ?species? or 
?-kind?) as equivalents of the scientific names of species, those 
names should be used in the plural. 
CAPITALIZATION
 The considerations about common names described above 
also bear on the issue of capitalization. Under the interpretation 
of the common names of species as proper names (e.g., Parkes 
1978; Potter 1984), those names are commonly capitalized. How-
ever, because common names are more appropriately interpret-
ed not as the names of species as wholes but as names of the 
sets of organisms of which species (as population lineages) are 
composed (de Queiroz 1995), common names are not, strictly 
speaking, the names of individual species. Therefore, they are 
not proper nouns and need not be capitalized (compare Atkins 
1983). This conclusion is consistent with the use of common 
names for the organisms comprising our own and other species 
(?humans,? ?dogs,? ?cats,? etc.), which generally are not capital-
ized. I am not arguing however, that common names should not 
be capitalized. There may be other reasons for capitalizing com-
mon names, such as distinguishing the common names of spe-
cies from general descriptions of organisms (e.g., ?Green Frogs? 
versus ?green frogs?) and ease of recognition while reading (Nel-
son et al. 2002; Parkes 1978). However, the act of capitalizing a 
Herpetological Review 42(3), 2011
342      pointS of view
common name does not thereby by make it a proper noun any 
more than does capitalizing a word in a section heading or at the 
beginning of a sentence. 
CONCLUSION
 In summary, plural rather than singular common names 
should be treated as equivalent to the scientific names of spe-
cies. This practice is more consistent with modern species 
concepts and the meanings of the words from which common 
names are formed; it more clearly distinguishes between differ-
ent hierarchical levels of biological organization; and it elimi-
nates a vestige of typological or essentialist thinking. Moreover, 
although using plural common names for species may at first 
seem strange because it departs from a long-standing tradition, 
the change is relatively minor, it now has precedents in a check-
list (Iguana Taxonomy Working Group 2011) and a taxonomic 
revision (Torres-Carvajal et al. 2011), and it should not be par-
ticularly difficult to become accustomed to. 
 Acknowledgments.?I thank B. Crother, H. Greene, B. Hedges, R. 
McDiarmid, and members of the Iguana Taxonomy Working Group 
(ITWG) for discussions related to this essay. Brian Crother also 
provided comments on the manuscript. Although the ITWG adopted 
use of plural common names in its checklist of iguana species, not 
all members (or the other people acknowledged) necessarily favored 
that convention, and even those who did may not agree with all 
aspects of the arguments that I have presented here. 
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