The hepevermia are worm-like fish snakes. They are ectothermic, covered in silicate scales, lack of eyelids, and lack external ears . Paired organs (such as kidneys) appear one in front of the other instead of side by side. The head is stout, not set off from the neck, and either rounded, sloped, or sloped with a ridge down the middle. Most of the skull is solid bone. They have no outer ears, and the eyes are deeply recessed and covered with skin and scales. The body is elongated, and the tail truncates in a manner that vaguely resembles the head. Many speciess use venom to immobilize or kill their prey.
The axial skeleton of the hepevermia consists of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic) and caudal (tail) vertebrae. Ribs are found exclusively on the thoracic vertebrae.
The jaws are able to disarticulate, allowing them to act like a hinge opening down up to 180°. While their teeth are attached to the jaw, they are constantly replaced throughout the animal's lifevia multiple rows of teeth growing along the edges of their upper and lower jaws. New teeth grow continuously in a groove just inside the mouth and move forward from inside the mouth on a "conveyor belt" formed by the skin in which they are anchored. Many species have a venomous bite
The skin is covered in dermal-teeth-like silica scales, arranged as a helical network surrounding their body. This works as an outer skeleton. Most species use specialized belly scales to travel, gripping surfaces. The body scales may be smooth, keeled, or granular.
Hepeverm vision is remarkable. Generally, vision is best in arboreal species and worst in burrowing species. Most can detect movement and have binocular vision, with both eyes capable of focusing on the same point. They smell a speialized organ in the mouth which gives a sort of directional sense of smell and taste simultaneously. The part of the body which is in direct contact with the surface of the ground is very sensitive to vibration. Some species also have infrared-sensitive receptors in deep grooves between the nostril and eye,
Hepeverms possess a three-chambered heart, encased in a pericardial sac, located at the bifurcation of the bronchi. The heart is able to move around, however, due to the lack of a diaphragm. This adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus. The spleen is attached to the gall bladder and pancreas and filters the blood. The thymus gland is located in fatty tissue above the heart and is responsible for the generation of immune cells in the blood. The cardiovascular system of snakes is also unique due to the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart.
There is only a singular lung. The lung operates unidirctionally, with air being inhaled via the mouth and spent air exhaled via an anterior opening.
Herpeverms have developed several different modes of locomotion to deal with particular environments. Each mode is discrete and distinct from the others, and transitions between modes are abrupt. These include: aquatic and terrestrial lateral undulation, "sidewinding", "concertina movement", "rectilinear locomotion", and a variuety of arboral locomotion forms.
All herpeverms employ internal fertilization, accomplished by means of paired, forked hemipenes, which are stored inverted in the male's tail, which are often grooved, hooked, or spined in order to grip the walls of the female's cloaca. Most species lay eggs, abandoning them shortly after laying. Some individual species construct nests and stay in the vicinity of the hatchlings after incubation. And a few species are viviparous