Morphological characteristics of sea snake tail

The boundary between the body plate and the wrist is obvious. The diameter of body disc is generally 65,438+0 cm, rarely exceeding 2 cm, but the diameter of tendrils can reach 65,438+00 cm. Wrist is slender, generally 5 ~ 10 times the diameter of intervertebral disc, and the longest can reach 30 times. The wrist number of plesiosaur is mostly 5, 6 is rare, and 4 is abnormal. Internal organs don't extend to the wrist. The bones inside the wrist are vertebrae, which are connected with each other through joints. The intervertebral joint of plesiosaur is an intervertebral joint, that is, the transverse saddle-shaped protrusion of the anterior vertebra and the longitudinal saddle-shaped protrusion of the posterior vertebra, so the wrist can move vertically up and down, wrap around other objects and bend horizontally. The intervertebral joint of the real Serpent is a joint of the joint vertebrae, that is, several depressions of the anterior vertebra and 1 central protrusion and 1 central depression of the posterior vertebra, so the wrist can only bend horizontally. Can't move vertically up and down. There are small plates or scales on the plate and wrist of the real snake tail. The primary disk on the disk includes 1 intermediate trunk, and the five-spoke and five-substrate is often very large and obvious. There are 1 pairs of developed spokes at the base of each wrist on the disc, and their shapes are often the basis for classification. Some species have a pair of wrist combs near the outer edge of spokes, and each wrist comb consists of multiple combs.

When the groove is closed, the tube foot degenerates into anal tentacles. The mouth is in the center of the ventral surface, and there are 1 large mouth rafters around the spokes. The shape of 1 in the five rafters is large, and the sieve plate has pores of 1 or more. The position of the sieve plate moves from the opposite mouth surface to the mouth surface. Inside each mouth, there are 1 pairs of side mouth plates arranged in a figure of eight, and then there are jaws composed of left and right small plates inward, and there are often 1 to several mouth spines on both sides. There are 1 row of vertically arranged teeth at the top of the jaw (Figure 2). The structure of the mouth is an important basis for classification. The lower teeth of Echinocephalidae differentiate into clusters of dentate spines without oral spines. Ctenodontidae has both dental spines and oral spines. The spines in the subgingival cavity of Yang-year-old Podopods are arranged in pairs. There are 1 root thorns in the subgingival mouth of Ophiuchus, which are heart-shaped. The oral spines of Echinocephalidae are thin and sharp. The number of oral spines in Pistaceae is numerous and continuous. Most of each wrist joint in Ophiuchus is covered with four wrist plates, namely 1 dorsal wrist plate, 2 wrist plates and 1 ventral wrist plate. There are different numbers of carpal spines on the lateral carpal plate. There are two rows of tentacle holes between the ventral carpal plate and the lateral carpal plate, and there are often tentacle scales beside each hole.

Their bones can be added with solid walls to maintain their softness and flexibility; The small bones on the wrist are relatively large and can move under the control of muscles and connecting tissues, just like the vertebrae in the human spine; Only the wrist of the blue starfish has branches on the tail of the sea snake.

Ophiopogon japonicus larvae are long-wrist larvae with 4 pairs of long wrists and ciliated bands, which are not attached when metamorphosis. Planktonic larvae also have bones, which can provide corresponding support during their sensitive and accurate swimming.

The individual development of Ophiopogon goes through Ophiopogon larva.

After 3 ~ 4 years, the abnormal individual is mature and has a life span of about 5 years.