The Argentine snake-necked turtle (Hydromedusa tectifera) is one of two South American snake-necked turtles in the genus Hydromedusa (Family - Chelidae). While they appear, at least externally, to resemble the Australian snake-necked turtles in the genus Chelodina, they are probably more closely related to my personal favorite, the bizarre Matamata (Chelus fimbriatus). The Hydromedusa genus is characterized by the extremely long neck and flattened head and neck. It is distinguished from the Australasian snake-necked genus Chelodina by the nuchal scute which is pushed back completely behind the marginal scutes into the row of vertebral scutes. Also, an intergular scute completely separates the gulars.
Two species of Hydromedusa are recognized: the Argentine or South American snake-necked turtle Hydromedusa tectifera, (Cope 1869); and the Brazilian or Maximillian's snake-necked turtle Hydromedusa maximiliani, (Mikan, 1820). The Hydromedusa tectifera range includes: northern Argentina, Uruguay, Paraguay and southern Brazil. The range of Hydromedusa maximiliani seems to be limited to the area in and around the Brazilian state of Sao Paulo, in southeastern Brazil. The two species are easily distinguished. Hydromedusa tectifera is larger (to over 11 inches), and is strongly keeled with rough vertebral and coastal scutes, becoming smoother with age. It has a black line on the side of its head and a yellowish-white streak running from its nostrils to the end of its neck. The smaller H. maximiliani has a smooth carapace reaching a little over 8 inches in length.
Sexual dimorphism is minimal in H. tectifera. Females reach a larger size, and mature males exhibit a plastral concavity centered on the midline of the rear plastral scutes.
In the wild, H. tectifera uses its snake-like neck to snorkel and dabble in the bottom. It is carnivorous, preying on small fish, amphibians and snails. The weak jaws are not suited to crushing the shells, but its flat narrow head helps it clean out the contents by allowing it to place its jaw right inside the shell opening. It is reported to be nervous and shy and to retain these characteristics in captivity.
My wife and I currently have two specimens in our possession: a female approximately 4 years of age, and a male (we hope!) that is younger. We just recently acquired the male so I will restrict my comments to the female which we have had for nearly two years. We have kept her outside from April to November and inside the rest of the year. Pritchard writes that H. tectifera hibernates during the colder months in the wild. My initial research regarding the climatic conditions in their home range indicates that it might be possible for them to remain outside all year round in parts of Southern California. However, I don't intend to risk leaving them outside in the winter until I have independent confirmation of this.