Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Four-Legged, Vertebrates — Vertebrates with Embryonic Membranes
Class Reptilia, or Reptiles — Subclass Anapsida — Order Testudines (Turtles) — Suborder Softshell Turtles

The suborder Softshell turtles comprises 25 species. They are sharply distinguished from all other turtles by the absence of horny plates on their shell. Their outer integument consists of soft, wrinkled, or tuberculate Skin. The underlying bony shell is poorly developed. Only the central part of the carapace forms a bony plate bordered by Cartilage. The HEAD features a long, mobile proboscis with the nostrils opening at its tip. The feet are webbed.

Softshell turtles are freshwater inhabitants, distributed across Africa, South Asia, and North America. A typical species is the Chinese softshell turtle (Trionyx sinensis), found in China, the Russian Far East (within the Ussuri and Sungari river basins), and Lake Khanka. This turtle spends the majority of its Life in Water, is a fast swimmer, and is capable of traveling several kilometers. It can remain submerged for long periods, breathing with the aid of its Pharynx, which features a rich network of Blood Vessels. Turtles come ashore to reproduce; they never venture far from the water and quickly dive back in when threatened. Their diet consists of fish, Mollusks, and crustaceans. They go into hibernation in the water at the beginning of October and reappear in mid-May. Egg-laying takes place in early June. In a shallow pit dug into a sandy shoal, the female deposits 30 to 70 eggs. The development period lasts 45 to 60 days, with the mass emergence of hatchlings at Lake Khanka occurring in mid-August. They are commercially harvested in China and Japan, whereas in Russia they are rare and listed in the Red Data Book.