Pelomedusidae

(vertebrate zoology) The side-necked or hidden-necked turtles, a family of the order Chelonia.

(Pelomedusidae)

Class: Reptilia

Order: Testudines

Family: Pelomedusidae

Thumbnail description
Medium-sized, sideneck turtles with five claws on the hind feet, four to eight neural bones present, the pleural bones almost always meeting at the midline behind the neurals, mesoplastral bones present, and the pelvis fused to the plastron

Size
Up to 21.6 in (55 cm) carapace length

Number of genera, species
2 genera; 18 species

Habitat
Freshwater habitats, from permanent rivers and lakes to ephemeral ponds

Conservation status
Vulnerable: 2 species

Distribution
Africa, Madagascar, and the Seychelles Islands

Evolution and systematics

Pelomedusidae is most closely related to Podocnemidae, but diverged from that family at least by the Cretaceous (at least 110 million years ago). Fossils are known from the Miocene to the Recent, but all belong to the two living genera. No subfamilies are recognized.

Physical characteristics

These turtles are generally small to medium in size, usually less than 12 in (30 cm), with a relatively extensive plastron that may (in Pelusios) or may not (in Pelomedusa) have a hinge present between the pectoral and abdominal scutes. The neural series is highly variable (with four to eight present), and the pleural bones almost always meet at the midline posterior to the neurals. A pair of mesoplastral bones are present between the hyo- and hypoplasta, and may (in Pelusios) or may not (in Pelomedusa) be in contact. Five claws are present on the hind feet.

Distribution

Africa up to at least 10,200 ft (3,100 m) elevation, Madagascar, and the Seychelles Islands.

Habitat

As a group, these turtles occupy nearly any freshwater aquatic system, from permanent lakes or rivers to ephemeral pools which may contain water only a few weeks at a time.

Behavior

Surprisingly little is known about the behavior of these turtles. They frequently bask at the water's edge, and several species make extensive overland movements during the wet season. During the dry season, many species estivate underground. In the temperate climates of southern Africa, they will hibernate terrestrially or aquatically. When captured, they produce a pungent musk from glands located near the bridges (bony structures that connect the plastron and carapace).

Feeding ecology and diet

These turtles are all primarily carnivorous, feeding mainly on annelids, mollusks, crustaceans, insects, fish, amphibians, and carrion. Some are at least partly herbivorous, eating water lettuce, aquatic grasses, or fruits.

Reproductive biology

No species in this family has been well studied; most of what is known is based on anecdotal reports. Most species apparently nest in late spring or summer, from October to January. The eggs are elongate with leathery shells, and clutch sizes range from six to 48. Multiple annual clutches have not been confirmed for any species, but seem likely considering the length of the potential nesting season. All species that have been studied exhibit temperature-dependent sex determination, with warm temperatures producing females, intermediate temperatures producing mostly males, and still cooler temperatures again producing females.

Conservation status

The actual field status of most of the species in this family has not been adequately assessed. The only two species listed as Vulnerable on the IUCN Red List are the two with the most restricted distributions: Pelusios broadleyi in Lake Turkana in Kenya, and P. seychellensis in the Seychelles.

Significance to humans

These turtles are occasionally eaten by indigenous people, but their foul-smelling musk secretions probably serve to discourage more regular consumption. They are also in low demand for the pet trade.

Species accounts

Resources

Boycott, R. C., and O. Bourquin. The Southern African Tortoise Book: A Guide to Southern African Tortoises, Terrapins and Turtles. Privately published, KwaZulu-Natal, South Africa, 2000.

Branch, B. Field Guide to the Snakes and Other Reptiles of Southern Africa. Cape Town: Struik Publishers, 1998.

Spawls, S., K. Howell, R. Drewes, and J. Ashe. A Field Guide to the Reptiles of East Africa. San Diego: Academic Press, 2002.

Anderson, N. B. "Pelomedusidae; Pelusios sinuatus; Serrate Hinged Terrapin; Reproduction." African Herp News 23 (1995): 46.

Rödel, M. O. "Predation on Tadpoles by Hatchlings of the Freshwater Turtle Pelomedusa subrufa." Amphibia-Reptilia 20 (1999): 173–183.

[Article by: John B. Iverson, PhD]

Pelomedusidae
Podocnemis unifilis
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Order: Testudines Suborder: Pleurodira Family: Pelomedusidae

Wikispecies has information related to:

Pelomedusidae

Classification:

Family Pelomedusidae

• Genus Pelomedusa (Helmeted turtles)
• Genus Pelusios (African mud turtles)
• Genus Podocnemis

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