The biological world is organized using a system of classification to help scientists manage the immense diversity of life on Earth. Animals are divided into groups based on fundamental physical characteristics. The subphylum Vertebrata represents animals defined by the presence of a backbone, or vertebral column. The number of species currently documented in this group is vast and constantly monitored by scientific bodies.
Defining Vertebrates and the Current Species Count
Vertebrates belong to the subphylum Vertebrata, a division within the phylum Chordata. Their primary shared feature is the vertebral column, a segmented series of bones or cartilage that protects the spinal cord. This group includes all fishes, amphibians, reptiles, birds, and mammals. Vertebrates are a relatively small fraction of the total animal kingdom, as invertebrates like insects and mollusks account for the vast majority of species.
The number of known vertebrate species is currently tracked by authoritative databases. The total is placed at approximately 76,000 living species globally. This figure is not static, representing the cumulative effort of taxonomists to catalog every distinct animal with a backbone. The species count continues to climb as new scientific methods deepen the understanding of biological relationships.
Distribution Across Major Taxonomic Classes
The total number of known vertebrates is distributed unevenly across the major classes. The largest and most diverse group are the fishes, which include jawless, cartilaginous, and bony species. Fish account for well over half of all described vertebrate species, with current estimates exceeding 33,000 species. Ray-finned fish (class Actinopterygii) constitute the vast majority of this number, representing about 50% of all vertebrates.
The next largest class is Reptilia, which includes turtles, snakes, lizards, and crocodilians. This group is estimated to contain over 12,500 described species. Birds (class Aves) are one of the most thoroughly studied groups, with current counts recognizing approximately 10,800 to 11,200 species worldwide.
Amphibians, including frogs, salamanders, and caecilians, are a smaller group with nearly 9,000 species currently known. Mammals (class Mammalia) represent the smallest group of vertebrates in terms of species count. Recent figures place the number of mammal species between 6,600 and 6,900.
Why the Species Count is Constantly Changing
The total number of vertebrate species is not a fixed figure because the field of taxonomy is dynamic and continually evolving. One major factor driving change is the ongoing process of scientific discovery. New species are regularly identified and documented, often in remote or under-explored areas. This process directly adds to the total count of known vertebrates.
Taxonomic Reclassification
Taxonomic reclassification involves scientists revising the relationships between known organisms. Advances in genetic sequencing frequently reveal that what was once considered a single species is actually two or more distinct species, a process known as “splitting.” Conversely, two species previously thought to be separate may be combined into one, which is referred to as “lumping.” These revisions significantly influence the overall species count.
Species Loss
The third factor affecting the count is the loss of species through extinction. When a species is officially recognized as extinct, it is removed from the list of living species. This removal reduces the overall tally of known vertebrates.