What is the Difference Between Acrania and Craniata?

Acrania and Craniata are two groups within the phylum Chordata that represent lower and higher chordates, respectively. The key difference between them is the presence or absence of a cranium or skull.

Acrania:

• Also known as Cephalochordata, they possess no fetal skull (cranium).
• They are exclusively marine small-sized chordates.
• They do not have a brain, skull, jaws, eyes, or auditory organs, making them the most primitive chordates.
• They can be found in more than two dozen species in the subphylum Cephalochordata.

Craniata:

• Belong to the subphylum Vertebrata within the phylum Chordata.
• They possess a well-defined cranium to safeguard the brain.
• They include all major classes such as Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia.
• Their aquatic vertebrates have persistent pharyngeal gill slits that help in respiration, and they generally have a distinct heart that helps in blood circulation.

Despite their differences, Acrania and Craniata share some similarities, such as the presence of a nerve cord, notochord, and pharyngeal slits.

Comparative Table: Acrania vs Craniata

Acrania and Craniata are two groups within the phylum Chordata that represent lower and higher chordates, respectively. The key difference between them is the presence or absence of a cranium or skull. Here is a table comparing the differences between Acrania and Craniata:

Acrania, also known as Cephalochordata, are primitive chordates that lack a cranium, brain, skull, jaws, eyes, and auditory organs. They comprise more than two dozen species in the subphylum Cephalochordata and are exclusively marine small-sized chordates. Craniata, also known as vertebrates, belong to the subphylum Vertebrata of the phylum Chordata and include all the major classes such as Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. They possess a well-defined skull, endoskeleton, chambered heart, blood vessels, blood corpuscles, and excretory organs such as kidneys.