Chaetodon Explained

Chaetodon is a tropical fish genus in the family Chaetodontidae. Like their relatives, they are known as "butterflyfish". This genus is by far the largest among the Chaetodontidae, with about 90 living species included here,[1] though most might warrant recognition as distinct genera.

Species

There are currently 87 recognized species in this genus:

Chaetodon sensu stricto

C. robustus group

Lepidochaetodon group

Subgenus Exornator (including Burgessius, Heterochaetodon and possibly Rhombochaetodon; tentatively placed here)

Subgenus Lepidochaetodon (including Tifia)

Subgenus Rhombochaetodon (including Roaops, might belong in Exornator; tentatively placed here)

Megaprotodon group

Subgenus "Citharoedus" (tentatively placed here)

Subgenus Corallochaetodon (tentatively placed here)

Subgenus Discochaetodon

Subgenus Gonochaetodon (tentatively placed here)

Subgenus Megaprotodon

Subgenus Tetrachaetodon

Rabdophorus group

Including Aspilurochaetodon, Chaetodontops

Incertae sedis

Most are probably either Chaetodon sensu stricto or C. robustus group.

Proposed subgenera

Several subgenera have been proposed for splitting out of this group. It is becoming clear how the genus might be split up, with a range[2] [3] of DNA sequence data in large parts agreeing with S.D. Blum's landmark 1988 phylogenetic assessment of osteology.[4]

Basically, a core group around the type species Chaetodon capistratus would remain in Chaetodon, while maybe four clades would be split off. These could use the names Lepidochaetodon, Megaprotodon and Rabdophorus, and there is one unnamed group containing the three-banded butterflyfish (C. robustus) and its relatives. But the monophyly of the Lepidochaetodon group is not fully established; it is both unclear whether Rhombochaetodon is a lineage distinct from Exornator, and whether Lepidochaetodon is indeed closer to these than to any other Chaetodon, particularly to some lineages otherwise placed in Megaprotodon.

Prognathodes, for some time contained in Chaetodon, is worthy of recognition as full genus, as is Roa.[5]

Historically, more distantly related fish were placed in Chaetodon too, for resembling them in details – e.g. the common scat Scatophagus argus, which has a similar shape and size, as well as armored larvae like the Chaetodontidae – or simply because they are colorful, smallish, and unusual-looking – e.g. the quite unrelated paradise fish, as C. chinensis.

The classification proposed in Fessler and Westneat is based on the species of Chaetodon they sampled and these sorted into the following clades:

Fossil record

The oldest fossils that are usually assigned to Chaetodon date from the late Oligocene, about 25 million years ago. But since it is not easy to distinguish this genus from close relatives, it may be that the Oligocene fossils are actually of other Chaetodontidae. The fossil record of this family is scant indeed, only Chelmon (or some similar genus like Chelmonops or Coradion) being known from Miocene remains. As even crude molecular clocks suggest that the ancestors of the Chaetodon and the Chelmops lineage diverged in the Late Eocene already, nothing more can be said without new fossils being discovered.[6] [7]

References

Notes and References

  1. FishBase (2006)
  2. Fessler, Jennifer L. . Westneat, Mark W . 2007 . Molecular phylogenetics of the butterflyfishes (Chaetodontidae): Taxonomy and biogeography of a global coral reef fish family . Molecular Phylogenetics and Evolution . 45 . 1 . 50–68 . 10.1016/j.ympev.2007.05.018.
  3. Hsu, Kui-Ching . Chen, Jeng-Ping . Shao, Kwang-Tsao . amp . 2007 . Molecular phylogeny of Chaetodon (Teleostei: Chaetodontidae) in the Indo-West Pacific: evolution in geminate species pairs and species groups . Raffles Bulletin of Zoology Supplement . 14 . 77–86 . 2008-09-02 . 2007-08-11 . https://web.archive.org/web/20070811042056/http://rmbr.nus.edu.sg/rbz/biblio/s14/s14rbz10_Hsu-pp77-86.pdf . dead .
  4. Blum (1988)
  5. Kuiter, R. H. 2004. Description of a new species of butterflyfish, Roa australis, from northwestern Australia (Pisces: Perciformes: Chaetodontidae). Records of the Australian Museum v. 56 (no. 2): 167-171.
  6. Sepkoski (2002), Fessler & Westneat (2007)
  7. http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=35985 Paleobiology Database

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