May be you have come across various species of lizards in your home, park or zoo and wonder whether they have backbones or not. How could their internal organs be protected or supported? Could they be having similar anatomy as mammals or other animals?
So, Are Lizards Vertebrates or Invertebrates? The simple answer is, all species of Lizard are vertebrates (they have backbone also called the vertebral column/spinal column).
The lizard’s spinal column is divided into cervical, dorsal, caudal regions and sacral apart from legless lizards whose backbone is divided into caudal and precaudal.
The main function of the backbone is to offer protection to the spinal cord. It also provides an option for attachment of body muscles.
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Lizards including bearded dragons are vertebrates whose spinal column is divided into cervical, dorsal, caudal and sacral vertebrae. Some species may have lumbar region too.
The main function of vertebral column in Lizards is to protect the spinal cord (this house the nervous system and aid in body coordination). In addition, the backbone offers support to the body and attachment of muscles, pectoral and pelvic girdle for easier locomotion.
a. Vertebral column in lizards.
Lizard (apart from legless lizards) have vertebral column also called spinal column or backbone that is divided into four parts i.e. cervical, dorsal, sacral and sacral vertebrae. Some lizard species may also have lumbar region.
These vertebral sub-divisions are formed mainly to help perform a given functions in lizards. The major function of vertebral column it to ensure sufficient protection of spinal cord – which runs vertically and centrally within vertebral column from the head to tail. The spinal cord helps in condonation of the nervous system of the entire lizard.
Related: Do Lizards Have Teeth?
i. The cervical vertebrae.
This vertebra is found at the neck region of the lizards. The cervical vertebrae help support the neck and assist in free movement of the neck – side by side, up and down or around.
The special type of cervical vertebrae called atlas is well adapted to help in nodding while axis allows rotary motion. In most lizards, the vertebral are articulated and fused is such a way that they seem vestigial. In some lizard species, most of these bones are advanced to form dorsal vertebrae.
The cervical vertebrae also provide the option for attachment of neck muscles and skull resting point.
ii. Dorsal vertebrae.
This is also called Thoracic vertebrae. The Dorsal vertebrae offer the point for attachment of the ribs. The ribs provide protection for the lungs, heart and the liver. The sternum and scapula are also attached on these vertebrae.
The number of dorsal vertebra varies according to the species. The small lizards such as chameleon lizards and savannah lizards may have 8 to 12 dorsal vertebra. The medium size lizards such as Nile monitor lizards may have 11 to 17 thoracic vertebra while large lizards such as Komodo dragon may have 16 to 25 dorsal vertebra.
iii. Lumbar Vertebrae.
These are vertebrae that are found between the dorsal and the sacral vertebral. These vertebrae do not carry any rib. Most lizards do not have Lumbar vertebrae thus their dorsal and sacral vertebrae are directly interconnected.
Lumbar vertebrae are only found in few large lizard species such as monitor lizards and Komodo lizards. The lumbar vertebrae provides an option for the attachment of body muscles. These vertebrae also enable lizards to fold coil easily.
iv. The Sacral Vertebrae.
The Sacral vertebral is the found in sacrum section. It is connected with pelvic to offer option for support and attachment of pelvic muscles.
The sacral vertebral has 1 to 7 bones in lizards. The number varies according to the lizard species. The first 3 sacral bones are fuse to form a strong support at the pelvis girdle.
The sacral vertebra has a short stout rib-like protrusion, which offer point of muscle attachment. Moreover, these vertebrae have short arches and spines.
v. The Caudal Vertebrae.
This is also called the tail vertebrae. In some lizards, the caudal vertebrae are fused with sacral vertebrae. These vertebrae have short stouts on the sizes that provide for the attachment of the muscles. There are 1 to a maximum of 30 caudal vertebra in lizards.
The small-tailed lizards such as stumpy-tailed lizards have few vertebra while long tailed lizards such as skinks, basilisk and chameleon lizards have large number of caudal vertebrae (10 to 30).
The arches and spines in caudal vertebrae continuously decreases up to the last vertebra. The caudal vertebral are adapted to provide easier movement of the tail.
Related: Are Blue Tailed Lizards Poisonous?
b. The Vertebral Column of Legless Lizard.
Legless lizards are lizard species that have lost their legs independently at a point in life or their legs have reduced into point of no use in locomotion. These lizards crawl on the ground like snakes.
The legless lizard has its backbone divided into two sections i.e. the precaudal and caudal vertebrae. These sections collectively support the lizard and protect the spinal cord from external damage as well as offer support and attachment for body muscles.
i. Precaudal Vertebrae.
The precaudal vertebrae consist of bones that are found before the tail/caudal or pelvic region. In precaudal vertebrae, bone are interconnected to form one chain that help the lizards in locomotion.
The cervical, dorsal/thoracic and lumbar are connected into one unit. These vertebrae offer option of attachment of body muscles and the ribs.
Most legless lizards have the first to fifth bones in the precuadal vertebrae fused thus having minimum movement/turning.
ii. Caudal Vertebrae.
The sacral and tail vertebrae in legless lizards are fused to form caudal vertebrae. Legless lizards do not have lumbar vertebrae and pelvic girdle (if any is very small).
The caudal vertebrae forms the tail region, which is powerful for defense action. The first 5 to 10 vertebral bones are fused to give ample strength to the legless lizard at the caudal origin.
The caudal vertebra has stout that protrude laterally to provide option for attachment of back muscles. Moreover, the caudal vertebrae have short spines and arches that decreases gradually till the tip of the tail.
c. Functions of the Backbone/spinal column
The major function of spinal column in lizards is to protect the spinal cord, which controls the nervous systems. The spinal cord runs vertically from the head to the tail and it’s centrally located through the hollow sections left along the vertebral column.
The backbone also provides option of attachment of the body muscles and point of growth of other body somatic cells. The muscles grows from the backbone and accumulate enough to help coordinated movement of the lizards.
The backbone provides the point of connections for other appendicular skeleton. The femur, the humerus and scapula are jointed to the backbone using either ball and socket joint or hinge joint to enable easier locomotion. The appendages are interlinked and their entire weight is housed at the backbone.
In addition, the backbone provides extra support and protection to internal organs such as the heart, liver, lungs and intestine. The clavicle, ribs and pelvis girdle are well jointed on the backbone to help in provide further internal protection.
Is lizard a reptile or amphibian
All lizards are reptiles including monitor lizards. They are cold-blooded animals (ectothermic). Unlike amphibians (which have smooth and slippery skin), Lizards have skin which is covered with scare – this one features of all reptiles. The following are characteristics/fears of reptiles (lizards):
1. They are cold blooded. This means that their body temperature changes according to the change in temperature on its environment. Because of the ectothermic metabolism of the lizards, they are forced to bask under the sun to raise its body temperature. A warm lizard is more active that a cold one.
2. Their skin is covered with scale or scutes. Reptiles develop hard skin that is made of scale using protein keratin. Reptiles such as turtles and armored crocodile have scutes which form deeper layer under the skin. All lizards’ skin is covered with scale.
3. Most reptiles lay eggs. Like most reptiles, lizards are oviparous – they lay eggs, which have hard shells. Their eggs are laid mainly on land. Lizards also take care of the eggs until they hatch. The eggs of amphibians (frogs) do not have hard shell. The eggs are enclosed in a jelly substance that offer protection – the female frog never take care of its eggs once laid in water.
4. They breathe by use of lungs. Reptiles (lizards) breathe though the lungs in their entire life – even when in water. Contrary, amphibians such as frogs and toad breath through lungs, skin or gills (at young stage – tadpole).
5. They have four walking legs (apart from legless lizards). The reptiles (lizards) have four legs that are used for locomotion/walking. Amphibians such as frog, newt or toad have two hind legs for jumping and two front legs adapted for landing. Their legs can’t walk as in the case of lizards.
Do Lizards Have Backbones?
Yes. Lizards have backbones since they are classified as vertebrates. The backbone is used to give support to body organs, muscles and cells. Moreover, the Backbone of lizards offers option for attachments of body muscles.
The backbone provides point link for appendicular skeleton such as ribs, femur, humerus, sternum or scapula as well as protect internal organs such as heart, lungs, livers and kidneys.
The hard bone spines and arches formed by the spinal column of lizards provide suitable defense tool against its enemies.
Major facts about Lizard as a reptile.
1. The Survival Mechanism.
Lizards have adapted to living in the harshest conditions without getting extinct due to their feeding diversity. Lizards feeds on variety of food such as small insects, crustaceans, snakes, birds and ever lard animals such as baby turtles.
Lizards such as Komodo dragon and tree crocodile are known for predation culture. They even attack human beings for food.
Lizards are able to camouflage and escape any predator. For example, the chameleon lizards are able to change color randomly to march the background and use this mechanism to escape the predator.
The venomous lizards use the poison to paralyze their prey before swallowing them. The strong tail of predator lizards is used a weapon to grasp and knock down their prey or defend themselves in case of attack.
Lizards often escape in case they notice dangers to hideouts that make predators difficult to reach them e.g. under the roof, in the thorn bushes or holes/cracks.
2. The lizard Habitat.
Lizards are found everywhere in the world. They mostly live on the ground. Lizards do not make nests. You will spot some lizards in trees, marshy areas or riverbanks (Nile monitor and Asian Water monitor)
Though lizards are ectothermic (cold blooded), you will find them in cold region as well as in arid and semi-arid areas e.g. Savannah monitor. Leopard geckos are crepuscular.
Lizards such as marine iguanas dwell under the water though they often come to the shore to bask and lay eggs. Lizards, which dwell on trees, have short wide toes that are well adapted to climbing.
Conclusion
All Lizard species are vertebrates. They have backbone, also called the vertebral column/spinal column, whose main function is to protect the spinal cord and offer option for attachment of body muscles and appendicular skeleton.
The lizard’s spinal column is divided into cervical, dorsal, sacral and vertebrae apart from legless lizards whose backbone is divided into precaudal and caudal vertebrae.