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| | Turtles (Lat. Testudines) are Reptiles of the Order Testudines, existing over a period of 250 million years. The Order Testudines consists of approximately 230 species, grouped in 12 families and 2 sub orders, spread across the earth and living both in water and on land.
Shell:
It is possible to accurately differentiate the modern turtles from other animals due to the presence of shell. Shell consists of upper shell – Carapace and Plastron (lower shell), which encases the belly. In many turtles, the outer shell is covered from top by symmetric horny scales called scutes. From front and back, the shell has holes, through which the turtle moves its limbs. In some species, mobile portions of shell can tightly close both the holes (or one of the holes) at the time of danger. Shape of the shell is linked with the living style of the turtles: In land based species, shell is high, dome-shaped and often diamond-shaped and in freshwater species – the shell is low, flat and smooth and aquatic turtles have streamline tear-drop shaped shell.
Neck, spinal, side and marginal shields are fusion on carapace and throat, inter throat, brachial, pectoral, abdominal, femoral, anal, axillary, inguinal and inter marginal shields are segregated on plastron. Each shield grows individually and concentric annotinous rings grow on shield.
In soft turtles, shell is cover with softy skin from top.
Reproduction:
All turtles reproduce by means of eggs. After pairing, which in many cases takes place on land, the female turtles lay eggs in jug-shaped chamber, which is excavated using hind legs. Then the chamber is filled up with eggs and the nesting chamber is closed using her hind legs and plastron. Eggs are usually round or ovoid shape and of white color. The egg is covered with solid calcareous shell. For aquatic and some side-necked turtles, the eggs are covered with soft leather shell. Number of eggs in a clutch depends on the species and fluctuates from few pieces to hundreds. Many turtles can lay eggs several times during the reproductive season.
Origin:
Till date, evolution chain from Parareptiles upto turtles is unclear. But conventionally, turtles are considered descendants of Permian cotylosaurus. First turtle Proganochelys quenstedi appeared in Mesozoic age in Triassic period (200 million years back). Out of 26 families, only 12 families could survive to our time. Now, many «modern» turtles are on the edge of extinction. Many fossil turtles are known, amongst which the largest was myolania with length of approximately 5 meters. Turtle may probably had huge and powerful tail, practically of same length as that of the shell. Tail is set with two rows of bony flat thorns. Lengthy blunt “horns”, directed towards back and sideways, are located at the ends of triangular turtle. |
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The end of the Labor Day weekend coincides with the beginning of 