# Scarus

Scarus is a genus of parrotfishes. With 52 currently recognised extant species, it is by far the largest parrotfish genus. The vast majority are found at reefs in the Indo-Pacific, but a small number of species are found in the warmer parts of the eastern Pacific and the western Atlantic, with a single species, Scarus hoefleri in the eastern Atlantic.
The genus name Scarus comes from the Greek word σκάρος (skáros), which refers to parrotfishes.

## Evolution

Scarus is most closely related to its sister genus Chlorurus. Most recent phylogenetic analyses find that the two genera diverged during the late Miocene (Messinian). In both genera, most of their diversification occurred some time later, within the last 3.5 million years during the Pliocene. In contrast, coral reefs in their modern form were established much earlier, during the Miocene.
Most Scarus species occur in reef habitats. However, some of the more basal species such as S. zufar occur in rockier, more peripheral habitats, suggesting that this may be the ancestral habitat type for the genus.
A 2012 phylogenetic analysis of 45 Scarus species recovered 10 major monophyletic clades.

## Description

Adults of most species reach maximum lengths of between 30 and 50 cm (12–20 in), but the rainbow parrotfish (Scarus guacamaia) can grow to lengths of 1.2 m (3.9 ft) and is the second largest species of parrotfish after the humphead parrotfish. S. guacamaia weighs a hundred times more than the smallest Scarus species Scarus iseri, which only reaches a maximum length of 27 cm.
In comparison to its sister genus Chlorurus, Scarus species in general have less obtuse head profiles, less extensive cheek areas, and smaller dental plates, although a few relatively basal species of Scarus are exceptions to this. This may possibly reflect comparatively lower biting power, and a disparity in the ability to excavate calcareous reef subtrata.

### Sexual dichromatism

Most Scarus species are very colourful, and most are sexually dichromatic, with strikingly different initial (male and female) and terminal (male only) phases. However in a few species, initial phase and terminal phase colouration remains the same. Examples of such sexually monochromatic species include S. guacamaia, S. coelestinus, S. perrico, S. niger,, and S. coeruleus.

## Ecology

Scarus species are important herbivores in reef ecosystems, feeding predominantly on algae and dead coral. In the process, they facilitate bioerosion and create sediment.
Lifespan varies across different species. More short-lived species, such as the common parrotfish (S. psittacus), live for up to 6 years. Other species are more long-lived; the endangered greenback parrotfish (S. trispinosus) has been recorded living for over 20 years, and is the largest herbivorous reef fish in the South Atlantic. Its close relative, the midnight parrotfish (S. coelestinus), has been recorded reaching 31 years of age. Such large bodied and long-lived species are highly vulnerable to over-exploitation by fisheries.
Many species within the genus are sympatric with each other, and often are sympatric with their sister species; Scarus frequently underwent sympatric speciation through adaptive radiation.

## Species

There are currently 52 recognised species in this genus:
| Species | Common name |
| Scarus altipinnis (Steindachner, 1879) | filament-finned parrotfish |
| Scarus arabicus (Steindachner, 1902) | Arabian parrotfish |
| Scarus caudofasciatus (Günther, 1862) | red-barred parrotfish |
| Scarus chameleon Choat & Randall, 1986 | chameleon parrotfish |
| Scarus chinensis (Steindachner, 1867) | |
| Scarus coelestinus Valenciennes, 1840 | midnight parrotfish |
| Scarus coeruleus (Edwards, 1771) | blue parrotfish |
| Scarus collana Rüppell, 1835 | Red Sea parrotfish |
| Scarus compressus (Osburn & Nichols 1916) | azure parrotfish |
| Scarus dimidiatus Bleeker, 1859 | yellow-barred parrotfish |
| Scarus dubius (Bennett, 1828) | regal parrotfish |
| Scarus falcipinnis (Playfair, 1868) | sicklefin parrotfish |
| Scarus ferrugineus Forsskål, 1775 | rusty parrotfish |
| Scarus festivus Valenciennes, 1840 | festive parrotfish |
| Scarus flavipectoralis Schultz, 1958 | yellowfin parrotfish |
| Scarus forsteni (Bleeker, 1861) | Forsten's parrotfish |
| Scarus frenatus Lacépède, 1802 | bridled parrotfish |
| Scarus fuscocaudalis Randall & Myers, 2000 | darktail parrotfish |
| Scarus fuscopurpureus (Klunzinger, 1871) | purple-brown parrotfish |
| Scarus ghobban Forsskål, 1775 | blue-barred parrotfish |
| Scarus globiceps Valenciennes, 1840 | globehead parrotfish |
| Scarus gracilis (Steindachner 1869) | |
| Scarus guacamaia Cuvier, 1829 | rainbow parrotfish |
| Scarus hoefleri (Steindachner, 1881) | Guinean parrotfish |
| Scarus hypselopterus Bleeker, 1853 | yellowtail parrotfish |
| Scarus iseri (Bloch, 1789) | striped parrotfish |
| Scarus koputea Randall & Choat, 1980 | Marquesan parrotfish |
| Scarus longipinnis Randall & Choat, 1980 | highfin parrotfish |
| Scarus maculipinna Westneat, Satapoomin & Randall, 2007 | spot-fin parrotfish |
| Scarus niger Forsskål, 1775 | dusky parrotfish |
| Scarus obishime Randall & Earle, 1993 | yellowtail parrotfish |
| Scarus oviceps Valenciennes, 1840 | dark-capped parrotfish |
| Scarus ovifrons Temminck & Schlegel, 1846 | knobsnout parrotfish |
| Scarus perrico Jordan & Gilbert, 1882 | bumphead parrotfish |
| Scarus persicus Randall & Bruce, 1983 | gulf parrotfish |
| Scarus prasiognathos Valenciennes, 1840 | Singapore parrotfish |
| Scarus psittacus Forsskål 1775 | common parrotfish |
| Scarus quoyi Valenciennes, 1840 | Quoy's parrotfish |
| Scarus rivulatus Valenciennes, 1840 | rivulated parrotfish |
| Scarus rubroviolaceus Bleeker, 1847 | ember parrotfish |
| Scarus russelii Valenciennes, 1840 | eclipse parrotfish |
| Scarus scaber Valenciennes, 1840 | fivesaddle parrotfish |
| Scarus schlegeli Bleeker, 1867 | yellowband parrotfish |
| Scarus spinus (Kner) | greensnout parrotfish |
| Scarus taeniopterus Lesson, 1829 | princess parrotfish |
| Scarus tricolor Bleeker, 1847 | tricolour parrotfish |
| Scarus trispinosus Valenciennes, 1840 | greenback parrotfish |
| Scarus vetula Bloch & Schneider, 1801 | queen parrotfish |
| Scarus viridifucatus J.L.B. Smith, 1956 | roundhead parrotfish |
| Scarus xanthopleura Bleeker, 1853 | red parrotfish |
| Scarus zelindae Moura, Figueiredo & Sazima, 2001 | Zelinda's parrotfish |
| Scarus zufar Randall & Hoover, 1995 | Dhofar parrotfish |

## In political thought

In Cesare Ripa's Renaissance iconography, the scarus fish symbolised civil "Union," i.e. the joining of individuals into a collective body. Plutarch had written that scarus fish "swim together in shoals and ingeniously and heroically free each other when caught in a net." The scarus thus "denoted reciprocal assistance in the fight for survival."