Sometimes, I am able to ascertain the identity of the coral to a species level. Usually, I am able to give a genus designation. Sometimes, I can go no farther than family. Occasionally, I am struck with a "damifino," as though spoken profoundly from the wisdom of Ron Shimek. Many times, I have directly challenged others, who have applied a species-level designation to a photograph, to explain the basis upon which they made their taxonomic diagnosis. I do this for good reason, and hopefully this article will provide the readers with a beginning point to understand the requirements and limitations of coral taxonomy in greater detail. I plan to cover most of the major coral groups in a few installments of this series - with not too much information to overwhelm, nor enough to make anyone an expert (nor could I, as I am hardly an expert in this field, either). It will be enough, though, so that many of you may begin knowing how to identify your corals to some level, or at least for you to understand why I waver, or wave my hands in the air, when confronted by this frequent request of, "What is this coral?"

Scleractinian corals are some of the easiest corals to address in terms of taxonomy, but can still be - and often are - exceedingly difficult to identify. For aquarists with living corals, identification will, in almost all cases, only be possible to genus. Even with a dead coral skeleton, identification to the level of species may be very difficult.

Aquarists (and scientists) often use well-known references, such as Corals of Australia and the Indo-Pacific (Veron 1986), to identify their corals. Amazingly, they will place a species level designation on their coral at home because it "looks like the one on p. xxx." Equally as often, they will base their identification on a coral which someone else has called "species x," or from an aquarium website with a coral named "species y," or the like. Some of the major sources of such designations are livestock sellers. Almost with reckless abandon, some very polymorphic and unspeakably cryptic corals have species names attached like the surname "Smith" to a man named "John."

This coral has been incorrectly designated as Lobophyllia pachysepta.	This is the "real" Lobophyllia pachysepta.

Without question, the predilection to add the species name "capricornis" to any flat, plating, or whorled, turbinate Montipora is my own personal favorite. I once spent five days examining a piece of Montipora, sold to me as M. capricornis, trying to affix a species name to it. I had six separate taxonomic reference sources at my disposal, including some of the original species descriptions for various Montipora species. I used a dissecting scope, a hand lens, a ruler, a micrometer and sketches to help me decipher what species I had. Eventually, I gave up. I could not tell what I had in front of me.

To illustrate this point, I looked at the first ten pages of photos from a search on google.com using the search term "Montipora capricornis." I would question the correct identification of M. capricornis on all of them, but of thirty or so sites, only two had what appeared might be the real thing. I then asked members on reefcentral.com to provide photos of corals they believed to be M. capricornis. After receiving a bevy of possible photos, I chose images that were clear enough to see and represented a spectrum of foliose Montipora species. Without question, there are some beautiful corals here, and without question they all display a foliose, plating, or turbinate growth form.

Now for the quiz:

Only one of the images is, to my knowledge, conclusively Montipora capricornis.

Click here to view the quiz images.

Can you tell which one?

There are also at least seven different species here, and possibly more. Do you know which ones are definitely other species?

The answer is that the lumpy pink coral, number 15 , is M. capricornis. Of the other images, numbers 1, 3, 9, 26, 27, 32, 34, and 40 look like they could be M. capricornis, but would require skeletal examination. I would not consider it likely that any of the others would be that coral, although normal variations might prove me incorrect. Number 15 is not necessarily a normal growth form of M. capricornis, which often more closely resembles the other more turbinate growth forms. But, this example makes two points at once: First, that there are many coral species that may closely resemble one another, that cannot be distinguished by means of a photo alone, and usually not in a living coral. Second, that a coral that is well known for "looking a certain way" may grow in such a manner due to various environmental and/or physical conditions so that it is completely unrecognizable by those same normal characteristics.

The second favorite example of mine involves the species of the genus Acropora. Aquarists seem to have, more than any other genus of stony coral, an almost uncanny need to assign a species name to Acropora. No one seems to care so much when a coral is described as Favia sp., or even if it's a Favia or a Montastraea species. But, call it an "Acropora" without a species designation and you just aren't in the hip "SPS circle." Almost every commercial site I could visit had Acropora for sale using species names. Given the Montipora example above from a pool of perhaps a dozen similar-looking species, I am sure you can imagine the photos I could exemplify for a genus with almost four hundred known species, with over half displaying branching or somewhat "staghorn-like" morphologies. It took Carden Wallace the better part of her life to be able to write a 421 page book to speciate this genus (Wallace 1999), and aquarists all too often simply look at a picture in a book and mark a coral for sale or in their tank as, for example, "Acropora yongei."

Despite the excellence of identification books like the epic "Corals of the World" (Veron 2000), I am sure even Charlie Veron would concur that one could not look at a photograph in his books and be able to assign a species to a coral in the vast majority of cases. Even when one reads about "characteristics," they are usually found to be of little help. Even when one has a "key to the species" to read, it is usually of little help (although we are getting much closer at this point).

There are several reasons:

First, and perhaps foremost, is the variability of many species. The degree to which variations among similar corals may overlap taxonomical traits is staggering. For some, there is almost a continuum of traits with no sharp defining point on which to say, "This is species x, and this is species y." On the other hand, some may be so apparent that a simple glance is all that is required, and you could say with a great deal of certainty that this is indeed "species z." Examples of such obvious species would be Heliofungia actiniformis, Acropora palmata, and Catalaphyllia jardinei.

Second, and also important, is that the corals collected for the aquarium trade are very small and often do not have enough mature growth to be able to accurately assess defining characteristics. Once placed in an aquarium, and even if allowed to grow large, the conditions of the aquarium are so different from the natural world as to provide no guarantee that such distinguishing features will ever be available; they may be present, and they may not be present - ever.

Third, and perhaps the defining reason, is that coral tissue covers the skeleton. In a few cases, a retracted polyp allows one to identify enough skeletal features to perhaps be able to identify a coral to species. Far more often, this doesn't happen. Alternately (and in even fewer cases), the living polyp can be used to identify a species where skeletal features may not. An example is with the genus Euphyllia, where both skeleton and polyp are required to affix a species name. Also possible is that there is some amount of tissue loss somewhere on the colony for one to see enough skeletal features to make an identification. This will only work for the most obvious cases, and anything more indistinct will require careful skeletal consideration.

What if I were to tell you that, unless the coral is unique, very distinct, monotypic (one species in the genus) or nearly monotypic, or perhaps endemic, you would not be able to ever - EVER - be able to say with 100% certainty that the coral you have in your tank belongs to a specific species? Perhaps not even then!

Here is a general format of what one would have to do in order to determine the species designation of a stony coral:

First, become aware of all terminology used to describe coral skeletal features. If you do not know what a colline, coenosteum pit, dissepiment, or style is, stop now. Equally troublesome, descriptive and vague words are used to describe these features; words that only make sense to those who have looked at thousands of skeletons. Phrases like, "thick fleshy walls," and "spongy columella" dot the literature of coral systematics.

Second, one would have to examine the holotype and paratypes. The holotype is the original specimen used to assign a new species, and paratypes are other examples, in addition to the holotype, that represent the new species. That is, one has to have an example of a known species in order to make comparisons. These are usually found in museums or the personal collections of taxonomists. Ideally, one would have many examples, physically present, to compare the variability across a species range and habitat tolerances, including atypical morphs of the known species, and any that share similar features. For some corals, it may be possible to go forward without type specimens, but if you want to be absolutely sure...

Third, one needs the taxonomical references to describe the species in question. This means not only original descriptions, but also all revisions and other pertinent works. For example, for the Caribbean brain coral, Colpophyllia natans, you would need:

Roos, PJ. 1971. The shallow-water stony corals of the Netherlands Antilles.
Studies on the fauna of Curacio and other Caribbean islands. 130: 108pp.

Cairns, SD. 1982. Stony corals (Cnidaria: Hydrozoa, Scleractinia) of Carrie
Bowe Cay, Belize. Smithsonian Contributions to Marine Science 12:
271-302.

Zlatarski, VN, and Estalella NM. 1982. Les Scleractiniaries de Cuba avec
donnes sur les organismes associes. Editions Acad Bulgare Sci Sofia.
472 pp.

Fenner, DP. 1993. Species distinctions among several Caribbean stony
corals. Bulletin of Marine Science 53 (3): 1099-1116.

Additionally, you would probably want the original description from 1772, and supplementary references such as Humann (1993), Veron (2000), and others. For Indo-Pacific corals, all volumes of the series "Scleractinia of Eastern Australia" (Veron 1976, 1977, 1980, 1982, 1984) are almost mandatory - and yet they contain material that is now outdated or changed by revisions in Veron (2000). So, both are really required, as are most of his other works (and there are many besides his more well-known books). This, of course, is in addition to any appropriate literature reviews, revisions, and descriptions by others. I list several revisions under the genus subheadings for various corals in Aquarium Corals (Borneman, 2001).

Some of the references for corals are very difficult to locate, and library loans aren't a possibility for many of them. Travel to the holding facility will be required. I had to fly to four different cities in the US, and one in Australia, to acquire enough reference material (in addition to the books and countless papers I already had from local libraries, photocopies, and loans) to be able to feel even reasonably safe with the identities of corals in Aquarium Corals. As it turns out, even that wasn't enough - Doug Fenner, a coral taxonomist and friend of mine, has pointed out several probable mistakes in that book.

Next, one could perhaps begin to look at the coral in question. Using a taxonomic key, one progressively works through it, bit by bit, looking not at just one part of the coral specimen, but many, and making sometimes arbitrary judgements about what is the "average" condition across the coral. While sometimes things are very clear, sometimes they are not. Let it also be noted that this is taking place on a prepared skeleton, and not with a living coral because the tissue will hide the skeletal features used to identify it. For some corals, there are relatively few identifying features. For others, there are many.

For example, let's return to Montipora capricornis.

Here's what I would do if I were interested in seeing if a coral I have in my tank is actually a M. capricornis.

The process begins by carefully breaking off several pieces of the living coral (without crushing or damaging the fragile skeleton) and then boiling it and bleaching it to obtain a cleaned piece of skeleton. I could use a Water Pik to remove the tissue, but I would be concerned about the force of the jet of water damaging the skeletal elements on this particular coral.

With the skeleton in hand, I would separate the species in question into one of twelve groups that designate the genus. In this case, it would be the group with "laminar species without conspicuous coensoteum ridges (Veron 2000)." Incidentally, this would probably eliminate most of the so-called "Montipora capricornis-es" from the aquarium-related sources above. I would then look at Veron (2001) and see that the characters are described as, "flat plates in tiers or whorls, sometime with columns, sometimes encrusting or forming irregularly contorted laminae. Corallites are immersed. There are no tuberculae or papillae. The coenosteum is coarse. Color is uniform purple, blue or brown (note: color is often a poor determinant of identity, and colors can change greatly. I also note that M. capricornis are mostly found in lagoons, and this may help explain the color. If they are in a clear brightly-lit aquarium, the color may not be very characteristic at all). Their range does include areas where coral collection takes place, but I have no idea where the specimen in question came from originally. There are two similar species (to an expert!) in this group - M. turgescens and M. florida. There are four species in the group of "laminar species without conspicuous coensosteum ridges." I have an unidentified species, and I am not a coral taxonomist by any means, and so I can't rule any of them out. This is as far as I can go using Veron (2001).

I do, however, note that the taxonomic reference is: Veron, JEN (1985). New Scleractinia from Australian Coral Reefs. Rec Western Australian Mus 12: 147-183. I don't have this reference. The identification guide given is, "Corals of Australia and the Indo-Pacific (Veron 1986);" a reference I do have. Unfortunately, it is little more help. So, I go to WorldCat, a web-based reference database, and find the libraries that own the requisite reference. I notice that Texas Tech has it (note to self: pick up this reference), and so I will need to proceed to acquire that source material. So, without the M. capricornis reference, I have another option: continue with a process of elimination of the two or four similar species. I also note that I do not have the 1967 Nemenzo reference required for Montipora florida, and so proceed to M. turgescens. I note that, incidentally, this is not one of the four species in the "laminar species without conspicuous coenosteum ridges" category. Sigh. Fortunately, I do have that reference (Veron and Wallace 1984).

With Veron and Wallace (1984), I am confronted with ten photomicrographs of corallums of this species that represent only some of the variations of the 101 (!) type species that are available from 19 sites only in eastern Australia. I also note the range of this coral includes Eastern Africa, the Red Sea, the Indo-Pacific and the central Pacific. So, there are many more variations likely than what I see here. I continue my reading.

The following characters for M. turgescens are from Veron and Wallace (1984). My comments are in parentheses.

"Colonies are massive, flattened, or hemispherical, or plate-like or columnar (this means just about any growth form is possible). The surface may be raised into a pattern of convex subcircular mounds, 3-12 mm in diameter (a large variation!). Corallites are uniformly distributed on and between these mounds and are immersed, with calices 0.7-0.9 mm in diameter. The thecal rim is usually distinguishable. Septa are tapered and are in two complete cycles reaching 2/3R and 1/2R deep within the corallite, where some may have thickened or fused margins. They are usually short near the corallite rim. They are composed of regular rows of spines, those of both cycles being of similar size. Immature corallites are budded in undifferentiated reticulum and appear as clusters of thin irregular septal spines, similar to reticulum spinules, but without elaborations. The reticulum is uniform in structure, spongy, with an outer covering of highly elaborated spinules.
The present series has very uniform corallite and coenosteal structures but varies greatly in the degree of development of the surface mounds (I need to know if there are more series in possession since this reference). These may be small or absent on flat or concave surfaces and also vary greatly in size on convex surfaces, much of this variation being found in single coralla. In some coralla, they may be small enough to form the walls of single corallites which consequently appear to be exsert and similar to the mixed corallites of M. nodosa and M. australiensis.
Living colonies are uniform in colour, usually brown, cream or purple.

Then, affinities are listed to M. nodosa, M. australiensis, M. mollis, and M. spongodes, and distinguishing characters are noted. If one is not familiar with those species, a similar process of examination using the characters for those corals should be done, as well.

So, knowing that some of this reference may be dated or incorrect, and that these characters are true for the species examined from Eastern Australia, and that variations exist, I can now decide if I can eliminate this coral from being the specimen in front of me. If I can't eliminate it based on what I can see or describe, it remains a possibility. I would then continue with all other possibilities, and eventually arrive at something that may or may not fit closely with any one species, and may even ultimately have to admit it "most closely resembles "Montipora xxxxxxx." In fact, this is more or less what happened to me when I tried to identify that coral sold to me as M. capricornis.

Is it any wonder that it might be sort of, well,… wrong, to call the Montipora in your tank Montipora capricornis?

With that in mind, I conclude this installment of the series. Next month, I will offer some practical solutions to "getting close" in identifications with living stony corals in our tanks, and will use some photos of coral skeletons in my collection to point out key features and identify specific characters used in taxonomy. The following month, I will discuss identification in non-stony corals.

Thanks to Charlie Veron for allowing the use of photos from Corals of the World, and to the members of Reef Central for providing all the photos of their Montipora spp., whether or not they were used in the article.

References:

Borneman, Eric H. 2001. Aquarium Corals: Selection, Husbandry, and
Natural History. Microcosm/TFH, Neptune City. 464pp.

Humann, Paul. 1993. Reef Coral Identification. New World Pulications,
Jacksonville. 239pp.

Veron, JEN. 2000. Corals of the World. Australian Institute of Marine Science,
Townsville. 3 Volumes.

Veron, J.E.N. 1986. Corals of Australia and the Indo-Pacific. University of Hawaii Press, Honolulu, Hawaii. 644 pp.

Veron, J.E.N., and Wallace, Carden C.. 1984. Scleractinia of Eastern Australia.
Part I. Family Acroporidae. Australian Institute of Marine Science Monograph Series, Vol. 6. Australian Government Publishing Services, Canburra. 485pp.

Veron, J.E.N., and Pichon, Michel. 1982. Scleractinia of Eastern Australia. Part IV.
Family Poritidae. Australian Institute of Marine Science Monograph Series, Vol. 5. Australian Government Publishing Services, Canburra. 159pp.

Veron, J.E.N., and Pichon, Michel. 1980. Scleractinia of Eastern Australia. Part III.
Families Agariciidae, Siderastreidae, Fungiidae, Oculinidae, Merulinidae, Mussidae, Pectiniidae, Caryophyliidae, Dendrophyliidae. Australian Institute of Marine Science Monograph Series, Vol. 4. Australian Government Publishing Services, Canburra. 422+pp.

Veron, J.E.N., Pichon, Michel, and Wijsman-Best, Maya. 1977. Scleractinia of
Eastern Australia. Part II. Thamnasteridae, Astroccoeniidae, Pocilloporidae. Australian Institute of Marine Science Monograph Series, Vol. 3. Australian Government Publishing Services, Canburra. 233pp.

Veron, J.E.N., and Pichon, Michel. 1976. Scleractinia of Eastern Australia. Part I.
Families Faviidae, Trachyphyliidae. Australian Institute of Marine Science Monograph Series, Vol. 1. Australian Government Publishing Services, Canburra. 86pp.

Wallace, Carden. 1999, Staghorn Corals of the World: A Revision of the Coral
Genus Acropora. CSIRO, Collingwood. 421pp.