Ropes vertebrates Animal Kingdom. Fauna. Natural Patrimony Aragonese. Aragon. Spain. 
Aragon > Nature of Aragon > Fauna

Ropes vertebrates Animal Kingdom.

This group includes animals that have reached a greater degree of evolution.
  The structure of the animals included in this group has three main characteristics:

  1. The existence of a dorsal cord or notocordio permanently in the individual or at least during some phase of its development.
  2. Existence of a main nerve cord, the spinal cord, which is located above the notocordium.
  3. Presence of branchial clefts in all groups, at least in embryonic phases.

General characters of the Cordados

The ropes are animals that are characterized by having, at some stage of their life or permanently, a notocordo or dorsal cord from which the spine is derived.

This rigid dorsal cord is located above the digestive system and below the nervous system, and acts as a skeletal support.

They also have a digestive tract with branchial communications in the pharynx, and a closed circulatory system, with a contractile organ or heart.

The nervous system consists of spinal cord, which always occupies the dorsal position, and brain, which develops from the anterior limb of such a duct.

The simplest representatives of this type of animals, the procordates, lack a skull and are called acraniums. Those who have it are called cranial, and understand to vertebrates.

The type of the Cordados is divided into several subtypes: Hemicordated, Urocordates, Cefalocordates and Vertebrates. The first two usually meet also under the denomination of Protocordados.


They are very different organisms from what a vertebrate can be.

Some look like digging worms with a tube or proboscis to dig in the sandy bottoms of coastal areas. Others are very similar to polyps.

They secrete protective tubular covers and have branched and ciliated tentacles but all have some of the characteristics of the ropes.

They are divided into three groups: Enteropneustos, pterobranchs and pogonophores.

Typical species:

A pterobranch: Rabdopleura
A enteropneusto: Balanoglosus
A pogonophore: Siboglium

Urocordated or tunicated

These are animals provided with a kind of mantle, secreted by themselves, that surrounds the body and receives the name of tunic and have a dorsal cord limited to the region flow or tail ..

Celoma is underdeveloped and lack segmentation. The gill slits have a double function: respiratory and as a filtration element to capture the plankton.
  The circulatory system is open.
The majority are hermaphrodites and many species also form colonies reproducing vegetatively.

They are divided into Ascidiaceae, Taliaceae and Larvaceae.

The ascites or ascidiaceae

In these marine animals the dorsal cord is limited to the tail of the larvae. The adults are shaped like a sack and their body is covered by the tunic, formed by a cellulose-like substance.

Metamorphosis of ascites

The larva of the ascidia is of free life during a brief time and its aspect is of tadpole.

It has a notocordio or dorsal cord that occupies the entire length of the tail. That is why they are also called urocordados.

Then the larva is fixed at the bottom by papillae and undergoes deformation.

The tail and dorsal cord disappear and the anterior region bulges to its final adult form.

Sometimes the ascidiaceae form colonies embedded in the rocks. The tunic of several individuals fuses forming gelatinous masses with a common cavity and with a large variety of coloration.

Taliaceous tunicates

They are organisms that are part of the marine plankton, transparent body, with a very thin tunic. Adults are barrel-shaped, at whose ends the mouth and cloacal opening.

They are surrounded by circular muscles that, by contractions, allow their movement.

They are devoid of dorsal cord in the adult state.

They are hermaphrodites and their reproduction is alternate, sexually and asexually.

Larvaceous tunicates

The larvaceous, also called appendicular, are small planktonic organisms with a rounded or ovoidal body with a long tail located ventrally, covered by a notocordio or dorsal cord.

They do not possess true tunic, but they secrete a gelatinous covering like a capsule, inside which the animal moves with some freedom and that can leave and build a new one.

Cephalocordates or acraniums

This small group includes 30 species of marine animals called amphioxes that are of great importance to science by representing the basic scheme found later in all vertebrates. They constitute a very primitive type of Cordados devoid of skull, spine and even limbs.
The body of the amphioxes is similar to that of a fish, flattened laterally and with sharp ends, carrying a fin-shaped projection on the back and another on the dorsal part.

In these procordates, the dorsal cord or notocordium develops throughout the length of the animal and permanently.

The nervous system is tubular and runs almost throughout the body. Next to the pharynx has gill slits, which flow into an internal cavity and open to the outside through a hole.

The circulatory system is closed without a true heart.

The body is covered by an epidermis rich in glandular elements.

The musculature is divided into segments.

Its external appearance is of fish of 5 to 8 cm. almost transparent, without fins or eyes, known as "lancet fish".


They are the most evolved ropes, with the body divided into head, trunk and tail. The embryo of all vertebrates has a notocordio, although only preserved in adults of very few groups. An important feature is the presence of an internal skeleton in the form of a spine (which replaces the notocordium when it disappears in the adult), formed by bone or cartilaginous elements called vertebrae.

On each side of that column an even number of unevenly developed appendages appear in the various groups.
They breathe through gills or lungs, which have their origin in the pharynx.
The celoma is well developed and the circulatory system is closed, with a heart divided into several chambers.

Other information about fauna in Aragón:

A small list of species in Aragon would be the following:

Vertebrates Invertebrates








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