Bulletin 34 - March 1988: Identification for the World's Sea Turtles



Identification for the World's Sea Turtles

by J.N.B. Brown

The following notes are taken from "Sea Turtles" by Robert Bustard, published by William Collins Sons & Co., Glasgow.

Although only three species have so far been identified in the Arabian Gulf and Gulf of Oman at the latest update of 20.11.1987, that is not to state that other species might not occur from time to time. The three positive recordings are the Green, Leatherback and Loggerhead turtles. It is hoped that this key will be an aid to identification and possibly lead towards the recordings of further species.

I. A. Four costal scutes on either side of carapace (Fig. la, CI - C4) i nuchal (N) separated from first costal (Cl) by first vertebra (VI).
1. One pair of elongated prefrontals (Fig.2 , pf); scutes of the shell do not overlap.
a. Scales on upper surfaces of distil half of front flippers large (Fig.3). Areas of much smaller scales between the phalanges lacking. Postocular count usually four. Shell colour usually light to dark brown with darker markings giving a mottled effect.
Green Turtle (Chelonia mydas)

b. Distil half of front flippers with single rows of large scales extending along phalanges. Many minute scales or wrinkled skin present on intervening areas (Fig.3). Three postoculars. Shell greatly depressed, marginals (M) curve upward. Shell colour olive-grey.
Flatback (Chelonia depressa)

2. Two pairs of prefrontals (Fig.2,pf) i scales of the shell overlapping like the tiles on a roof. Shell colour amber with streak-like markings of red-brown, black and yellow.

Hawksbill (Eretmochelys imbricata)



B. Five or more costal shields on either side of carapace (Fig.lb-c, CI-C5); nuchal (N) in contact with first costal (Cl) (Fig.lb-c); two pairs of prefrontals or a group of five or more shields and scales on the prefrontal region (Fig.2c).

1. Five (rarely six) costal shields on either side of carapace (Fig. 1b, C1 - C5).
a. Shell always considerably longer than wide. Inframarginal scutes lack pores. Shell colour reddish brown to brown.
Loggerhead (Caretta caretta)

b. Carapace extremely broad in relation to length; may be even broader than long. Inframarginals with a pore (minute opening) at hind border. Carapace grey-brown to blackish or olive-green.
Kemp's Ridley (Lepidochelys kempi)

2. Six to nine costal shields on either side of carapace (Fig.1c). Shell relatively broad. Shell colour grey-green to dark brown.
Olive Ridley (Lepidochelys olivaceas)
II. Shell covered with a thick leathery skin and strongly tapering towards the rear (Fig.1d). Forelimbs lack claws. Colour of upper parts blackish. Small irregular white or pinkish spots often present.
Leatherback (Dermochelys coriacea)


Olive Ridley (Pacific) - Lepidochelys olivacea

Leatherback (widely-distributed in warm seas, common in parts of Atlantic) - Dermochelys coriacea

Green (widely-distributed)- Chelonia mydas

Hawksbill (tropical & sub-tropical seas) - Eretmochelys umbricata

Loggerhead (widely distributed in warm seas, common along Atlantic coast of Central America Brazil and USA) - Caretta caretta

Kemp's Ridley (common in parts of the Atlantic) - Lepidochelys kempi

Flatback - Chelonia depressa



Further references:

'Green Turtle', ENHG Bulletin 5, July 1978.
'The Loggerhead Turtle', ENHG Bulletin 7, April 1979 & 21, November 1983.
'Recent Turtle Records', ENHG Bulletin 24, November 1984.

 


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