Characteristics of Chordata

A notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail are four of the most distinguishing characteristics of Chordata.

Key Takeaways

.orgochord Cord of nerves A pharyngeal cut

Characteristics of Chordata

The members of the Chordata phylum share four features, which can be observed at various stages of development (often, only during embryogenesis) (:

The four common features of chordates are: notochords, dorsal hollow nerve cords, pharyngeal slits, and a postanal tail.


Notochords, the structures that form the embryonic stage of chordates and the adult stage of some chordate species, give them their name.Between the digestive tube and the nerve cord, it provides skeletal support throughout the body.Notochords are critical components in the body of some chordates. They act as primary axial supports throughout the animal's life.

In vertebrates, the notochord is present during embryonic development, when it induces the development of neural tube, which supports the developing embryonic body.For most adult vertebrates, the notochord is replaced with the vertebral column (spine).

Dorsal Hollow Nerve Cord

During development, ectoderm forms a hollow tube during the dorsal hollow nerve cord.In chordates, it is found at the top of the animal, dorsally to the notochord.Contrary to chordates, other animal species have either ventrally or laterally located solid nerve cords.Most chordate embryos contain a nerve cord that develops into the brain and spinal cord, which are the main components of the central nervous system.

Pharyngeal Slits

A pharyngeal slit is an opening that extends to the outside environment from the pharynx (the region just posterior to the mouth).A pharyngeal slit permits water that enters the mouth during feeding to exit. These slits are commonly found in organisms that live in aquatic environments.Chordates invertebrates use the pharyngeal slits to filter food out of the water that enters their mouths.The pharyngeal slits of vertebrate fish develop into gill arches - boney or cartilaginous supports for the gills.

.Among these animals, pharyngeal slits develop into jawbones and bones of the inner ear.

Post-anal Tail

A post-anal tail extends beyond the anus and extends posteriorly from the body.Aquatic organisms use their tails to propel themselves. They contain skeletal elements and muscles that enable them to move.In some terrestrial vertebrates, the tail also aids in balance, courtship, and indicating danger.It appears during embryonic development, but disappears as an adult in humans and other apes.

Chordates and the Evolution of Vertebrates

There are two subphyla of invertebrates in Chordata: Urochordata (tunicates) and Cephalochordata (lancerta).

Key Takeaways

Archive of data Cenochordata Assile

Chordates and the Evolution of Vertebrates

Chordates are best known as vertebrates.Chordata includes the subphylum Vertebrata as well as two invertebrate subphyla: Urochordata and Cephalochordata.Chordates, like the two groups mentioned above, also possess the four distinctive features of chordates at some stage of their development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.Urochordates and cephalochordates do not develop bony backbones like vertebrates do.


Tunicates are members of Urochordata.In tunicates, the tunic is a cellulose-like carbohydrate material that covers the outer body.In spite of the fact that tunicates are classified as chordates, their larval form has all four common structures.The notochord, the dorsal hollow nerve cord, and the post-anal tail are absent from adults.

Photo: (a) This image shows a tunicate colony of Botrylloides violaceus.(b) The larval stage of the tunicate possesses all features characteristic of chordates: a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail.Its notochord, nerve cord, and tail disappear during adulthood.

Almost all tunicates are hermaphrodites.Tunicate larvae hatch from eggs inside the body of an adult tunicate.The tunicate larva swims for a few days before it finds a suitable surface to attach to, usually in a dark or shady place.As it grows, it attaches via the head to the surface and undergoes metamorphosis into the adult form, where the notochord, nerve cord, and tail disappear.

Most tunicates live sessile lives on the ocean floor and feed from suspension.Tunicates feed primarily on plankton and detritus.In the body of the tunicate is an incurrent siphon where seawater enters.During digestion, the mucous net (pharyngeal slits) filters the suspended material out of this water and passes it into the intestine.Into the excurrent siphon, which discards wastes and water, the anus empties.Tunicates are found in shallow ocean waters throughout the world.


In the adult stage, Cephalochordata possess a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.There is no brain in them, but the notochord extends into the head, earning them the name "cephalopoda.".One of the oldest cephalochordates is Pikaia, which is extinct in this subphylum.Pikaia fossils were found in the Burgess shale in Canada, dating them to the middle of the Cambrian period, so they are more than 500 million years old.

The lancelets, named for their blade-like shape, are living members of the Cephalochordata.Lancelets only measure a few centimeters in length and are usually found buried in sand at the bottom of warm, temperate and tropical seas.They feed on suspended particles.Lancelets and Pikaia may belong to the chordate group of animals, from which vertebrates descended.

The lancelet has a head, as do all cephalochordates.In adults, lancelets retain the four defining features of chordates: the notochord, the dorsal hollow cord, the pharyngeal slits, and the post-anal tail.Filtered water enters the pharyngeal slits from the mouth, which removes food particles.Water collected in the atrium is vented through the atriopore.

Key Takeaways

Crâne Genes Explosion of the Cambrian age

Craniata and Vertebrata

Chordata is a subdivision of the clade Craniata.A cranium (a bony, cartilaginous, or fibrous structure surrounding the brain, jaw, and facial bones) is possessed by members of the Craniata.The clade Craniata contains all vertebrates and the hagfishes (Myxini), which are devoid of a backbone.Hagfish are the only known living animals that do not have vertebrae in their bodies.


Hagfish: Although the hagfish doesn't have a backbone, it belongs to the Craniata clade thanks to its bony skull.

Caddia, including this fish (Dunkleosteus), have craniums, mandibles, and facial bones.

The vertebrates are characterized by the presence of a backbone, like the one running through the middle of the fish.In the Craniata group of vertebrates, the cranium is a characteristic feature.

Vertebrate Evolution

Within the Chordata phylum, the closest relatives of vertebrates are the invertebrate chordates.Researchers can determine different phylogenetic groups' evolutionary histories using molecular analysis of vertebrate and invertebrate genomes (genomics).

These genomic analyses suggest vertebrates are closer to cephalochordates (cephalochordates) than to tunicates (urochordates).Consequently, cephalochordates diverged first from urochordates, whereas vertebrates developed subsequently from cephalochordates.There is a fossil of an organism 530 million years old with a brain and eyes like a vertebrate, but no skull like a craniate.The genomes of a lancelet, tunicate, lamprey, fish, chicken, and human have been compared, confirming that there were two entire genome duplications during early Vertebrata evolution.

There is fossil evidence supporting the idea that vertebrates appeared during the Cambrian explosion. The Cambrian explosion was the relatively brief window of time in the Cambrian period during which many animal groups appeared and rapidly diversified.Animal phyla evolved during the Cambrian explosion.

Characteristics of Vertebrates

Vertebrates are further classified by their bony bone structure as a subphylum of Chordata.

Key Takeaways

There are three vertebral columns Syncrotate NOTOCHROME

Characteristics of Vertebrates

There are five subphyla of vertebrates, within the phylum Chordata and kingdom Animalia. .There are two phyla of deuterostomes: Chordata and Echinodermata. Their name translates as "second mouth.". .The phylum Chordata contains two groups of invertebrate chordates, but the most identifiable and familiar group are the vertebrates.

Phylum chordata: All chordates possess a notochord.Differentiation between vertebrates is based on their vertebral column.

A chordate, a vertebrate has similar anatomy and morphology with the same qualifying characteristics: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a postanal tail. .In addition to the jawless fishes, bony fishes, sharks, and rays found in the ocean, vertebrates include amphibians, reptiles, mammals, and birds.

The subphylum Vertebrata contains animals with backbones, gills, and central nervous systems in at least one developmental phase.Vertebrates include amphibians, reptiles, mammals, and birds, as well as sharks and rays.

More than 64,000 vertebrate species have been described, but they are only a small portion of all species that have existed in the past.Among vertebrates, there are a variety of sizes, ranging from the frog Paedophryne amauensis (as small as 7.7 mm (0.3 inch)) to the blue whale (as large as 33 meters (110 feet).The rest of the animal species are invertebrates, which lack a backbone. Most vertebrates are specialized for specific tasks.

Anatomy and Morphology

The vertebrates all have the same basic chordate body plan: a rigid rod running through the length of the animal (vertebral column), with a hollow tube of nerve tissue (the spinal cord) above it and the gastrointestinal tract below.Vertebrates have a mouth on the anterior end of the animal and an anus on the posterior end.There is a tail posterior to the anus at some point in the animal's development.

The Vertebral Column

Animals classified as vertebrates have a spinal column.Vertebrate notochords connect the notochord to the vertebral column, which is composed of boney vertebrae separated by discs.The dorsal vertebrae are always found on the dorsal side of the animal.The sturgeon fish, for example, retains its notochord through adulthood even when it has lost vertebrae.


Fossilized skeleton of the dinosaur Diplodocus carnegii illustrates an extreme example of the vertebral column.

Central Nervous System

Chordata includes only vertebrates, who have brains as well.Chordates are animals with a hollow, dorsal nervous system that runs along both sides of the notochord.A nerve tube's anterior end expands and differentiates into three brain vesicles in vertebrates.

Vertebrate Classification

Vertebrates account for the largest group of chordates, with more than 62,000 species.Physiological and anatomical characteristics are used to group vertebrates.Groups traditionally included in the system are Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia.

The gnathostomes (finfishes, reptiles, birds, and mammals) are animals with jaws. This group includes fish and tetrapods (amphibians, reptiles, birds, and mammals).There are two types of tetrapods: amphibians and amniotes.Mammals, reptiles, and birds are all members of the amniote family.The amniotic embryo, whether it is built in an externally-shelled egg or carried by the female, is provided with a water-retaining environment and is protected by amniotic membranes.