The Arabian Chameleon Species Explained

Arabian Chameleon Taxa

There are four chameleon taxa living on the Arabian Peninsula:

• Chamaeleo arabicus
  
• Chamaeleo calcarifer
  
• Chamaeleo calyptratus
  
• Chamaeleo chamaeleon orientalis
  

Additionally, on Socotra Island, a Gondwanan fragment, an endemic Chamaeleo monachus is found. As it is totally isolated, it is not considered in the comparison.

Ranges

Their evolutionary history is complex and represents a radiation of a chameleon lineage from the Horn of Africa across and around the Red Sea, using land bridges and biocorridors to southern Arabia and across Persia to India and Sri Lanka (the latter two inhabited by their close ally, Chamaeleo zeylanicus).

• C. arabicus lives along the southern Arabian coast from Lahej in southern Yemen to the Dhofar Mountains and the adjacent coast, with an isolated population on Masirah Island.

• C. calcarifer occupies the Asir Mountains in the Kingdom of Saudi Arabia, dropping down to valleys at its western foothills.

• C. calyptratus inhabits high elevations of the Hijaz Mountains and its wadis, not reaching the Tihama.

• C. chamaeleon orientalis extends its range from northern Asir Mountains to northern Hijaz, up to the vicinity of Sana'a.

The first three taxa are perfectly allopatric, but the range of C. chamaeleon orientalis stretches over areas inhabited by C. calcarifer and C. calyptratus. However, it inhabits higher elevations and does not occur syntopically with either of them.

Morphological Comparison

Through the character displacement process, the characteristic features have evolved interestingly, and the species are well defined morphologically. While their general morphology remains similar—all have elevated casques (CC), gular crests (GC), and occipital lobes (OL)—the total size (TS), combination, size, and shape of these features differ among the species as follows:

C. arabicus:

• CC: second smallest

• GC: second smallest

• OL: second largest, with conical scales on the margin

• TL: max 42 cm

C. calcarifer:

• CC: second largest

• GC: second largest

• OL: second smallest

• TL: max 64 cm

C. calyptratus:

• CC: largest

• GC: largest

• OL: smallest

• TL: max 72 cm

C. c. orientalis:

• CC: smallest

• GC: smallest

• OL: largest

• TL: max 27 cm

Coloration

Their coloration shows the same basic pattern but uses different colors. Females are quite similar, but males show typical colorations:

• C. arabicus: turquoise blue

• C. calcarifer: shades of bright green

• C. calyptratus: turquoise green-bluish with yellow crossbars and lots of orange

• C. c. orientalis: greenish and grayish

Taxonomic Note

C. calcarifer was long under-collected due to poor accessibility of its range. However, as hundreds of specimens are documented nowadays, it seems clear it is a separate species and not a subspecies of C. calyptratus.