International Journal of Marine Science, 2016, Vol.6, No.14, 1-10
6
Chevalier that they are not able to always identify four
Echinopora
species, and the same is true of other genera.
The problem is not much better with the four species of
Platygyra
. The larger a collection is, the more samples of
one species at least from the same area are available, and the more uncertainty and doubts a taxonomist has, since
the limits of extreme values of features become more and more extensive, and variability curves become more and
more even and continuous.
In principle, this is all right. If these are specimens of the same species, a complex of values of features of all
samples must fit in the limits, determined by the given feature, and constitute a complete series of transitive values
of the feature. It is all correct, and will work only when the feature is clear and has a single meaning, no matter
whether it is qualitative or quantitative. If we limit ourselves to such a terse diagnosis as to say that
Favites
are
similar to
Favia
but they are cerioid (Wells, 1956), then it will be necessary to follow the diagnosis strictly.
Favia
have only placoid colonies, and
Favites
– only cerioid ones, but not subplacoid or subcerioid, as we can often read
in diagnoses and descriptions of Faviidae (Figure 1, 2).
3.2 Favia and/or Favites
Strictly speaking, all
Favia
have placoid colonies, especially if we mean type specimens. In other words,
all these
corals have massive colonies with corallites closely or distantly located from each other
(Figure 1, Figure 2). I
stress that these are detached corallites, mainly of a round shape, though this roundness can be close to a trigonal
or irregularly polygonal form (
F. laxa, F. speciosa
).
The opinion about purely cerioid Favia pallida and F.
rotumana (
Veron et al. 1977
) is not quite correct.
Type specimens of these species are typically placoid. They
have round corallites, slightly detached or adjoining. Every corallite has clearly developed endo- and exotheca.
Adjoining corallites are necessarily separated by a distinct groove. The same can be said of the majority of cited
pictures of these species (Hoffmeister, 1925; Wells, 1954; Chevalier, 1071; Scheerr and Pillai, 1974, 1983; Veron,
1986; Nakamori, 1986; etc.). Even in supposedly subcerioid specimens (Veron et al. 1977, p. 34, Figure 49-52;
Figure 62-63) endo- and exotheca (despite the irregular, almost polygonal form of corallites) and clearly detached
corals with discrete costal ridges are clearly seen. As to the truly cerioid specimen of
F. pallida
(p. 34, Figure 46,
in the same work), its attribution to the genus
Favia
seems to me doubtful, as it has typically cerioid corallites
with a common endotheca, here and there turning into septotheca, septa of the neighboring corallites are adjoining,
and these are features typical for
Favites
.
Regarding cerioid-placoid forms of
Favites rotundata
and
Favites complanata
(Veron et al. 1977), it is necessary
to note approximately the same circumstances as discussed above. First,
Favites rotundata
has now been placed in
the genus
Favia
, secondly, the type specimen and cited pictures of
Favites rotundata
specimens have clearly
polygonal (cerioid) corallites with a common septothecal wall and adjoining septa. A false boundary between
corals can be formed at the expense of light removal towards adjoining septa at their transition to a neighboring
corallite and replacement of an earlier cycle by a later one. And finally, the columella is formed by complexly
divided anastomosing trabeculae, which cannot be in
Favia
.
In conclusion, we shall consider one more example, testifying to the necessity of a strict approach to the character
of a “placoid coral”, which is attributed to the genus
Favites
by Veron and his co-authors (1977). In this case, first
of all, not only the purely placoid form of a colony and corallites alerts one to the problem, but also two cycles of
highly projecting septa with a very well developed crown of pali. These features are more typical for the genus
Plesiastrea
. In addition, the total number of septa (the third cycle is always rudimentary) rarely exceeds 30. In the
smallest representative of
Favia
the number of septa is 30-40 (the third and fourth cycles are always developed),
and on the average they have 40-60 septa.
Thus, in many cases taxonomic problems in identification and systematization of Faviidae arise in the result of
vagueness of definition of diagnostic classification characters or introduction of alien characters, not proper for
the given genus. Because of this process, an artificial extension of natural limits of species variability takes place,
with species falling out through the boundaries fixed for each genus.
