How are agnathans different from jawed vertebrates?

Agnathans, which comprise the group of primitive jawless fishes such as lampreys and hagfishes, are distinguished from jawed vertebrates (gnathostomes) primarily by the absence of several key anatomical features.123

Compared to gnathostomes, agnathans lack the following:
* Jaws: They do not possess the hinged jaw structures used by other vertebrates for biting and chewing.134
* Vertebrae: Despite being classified as vertebrates, they lack a true vertebral column.13
* Lateral fins: They do not have paired fins supported by fin rays.13
* Ear structures: They lack a horizontal semicircular canal in the ear.13
* Genital ducts: They lack the specialized ducts for reproduction found in jawed vertebrates.13

Additionally, while agnathans share the same basic physiological systems as gnathostomes, these systems are generally simpler in structure. Notably, their gills are pouchlike and open through pores, rather than being the slitlike structures found in jawed fishes.31