Tribelesodon, originally considered to be a pterosaur by Francesco Bassani in 1886, is now recognized as a junior synonym to Tanystropheus.
Another junior synonym of Tanystropheus is Procerosaurus, whose type species, P. cruralis, was erected by von Huene in 1902.
Several supposed Tanystropheus species described from the southwest United States in the late 19th century were later determined to belong to a new genus of theropod dinosaur, Coelophysis.

The type species of Tanystropheus, T. conspicuus, is based on postcranial specimens from the Upper Muschelkalk of Germany and the Lower Keuper of Poland.
These remains were previously known as Macroscelosaurus (a nomen oblitum) before being named as Tanystropheus in 1855.
They were later regarded as undiagnostic, rendering T. conspicuus a nomen dubium.

T. antiquus, which was named in the late 1900s from the Gogolin Formation of Poland, was based on vertebrae shorter than those of other Tanystropheus species.
Its specimens were subsequently lost until they were rediscovered in the 21st century.
T. antiquus is currently considered one of the few valid species of Tanystropheus.

The best-known valid species of Tanystropheus is T. longobardicus, which comes from the Besano Formation (also known as the Grenzbitumenzone), an Anisian-Ladinian formation exposed at Monte San Giorgio on the Italy-Switzerland border.
The first T. longobardicus specimens were described in 1930s, and Monte San Giorgio continues to produce new specimens up to the present day.
In 2005, Dr. Silvio Renesto described a T. longobardicus specimen from Switzerland which preserved the impressions of skin and other soft tissue.
Five new specimens of T. longobardicus were described by Stefania Nosotti in 2007, allowing for a more comprehensive view of the anatomy of the species.

Tanystropheus specimens from the Makhtesh Ramon in Israel were described as a new species, T. haasi, in 2001.
However, this species may be dubious due to the difficulty of distinguishing its vertebrae from T. conspicuus or T. longobardicus.
Another new species, T. biharicus, was described from Romania in 1975.
It has also been considered possibly synonymous with T. longobardicus.
A small but well-preserved skull and neck, specimen PIMUZ T 3901, was found in the Meride Limestone at Monte San Giorgio.
It was given a new species, T. meridensis, in 1980.
The skull was later referred to T. longobardicus, rendering T. meridensis a junior synonym of that species.
Another species, T. fossai from the Norian-age Argillite di Riva di Solto in Italy, was given its own genus Sclerostropheus in 2019.

Specimens similar to T. longobardicus have been found in the Ladinian or early Carnian Zhuganpo Formation in the Guizhou province of China, as described by Li (2007) and Rieppel (2010).
In 2014, fossils of an indeterminate species of Tanystropheus were discovered in the Wolfville Formation in the Bay of Fundy in Nova Scotia, Canada.
Indeterminate Tanystropheus remains are also known from the Jilh Formation of Saudi Arabia and various Anisian-Ladinian sites in Spain, Italy, and Switzerland.

A 2019 revision of Tanystropheus found that only T. longobardicus and T. antiquus were valid species.
In 2020, large Tanystropheus specimens from Monte San Giorgio originally assigned to T. longobardicus were given a new species, T. hydroides.
Tribelesodon, originally considered to be a pterosaur by Francesco Bassani in 1886, is now recognized as a junior synonym to Tanystropheus. Another junior synonym of Tanystropheus is Procerosaurus, whose type species, P. cruralis, was erected by von Huene in 1902. Several supposed Tanystropheus species described from the southwest United States in the late 19th century were later determined to belong to a new genus of theropod dinosaur, Coelophysis. 
The type species of Tanystropheus, T. conspicuus, is based on postcranial specimens from the Upper Muschelkalk of Germany and the Lower Keuper of Poland. These remains were previously known as Macroscelosaurus (a nomen oblitum) before being named as Tanystropheus in 1855. They were later regarded as undiagnostic, rendering T. conspicuus a nomen dubium. 
T. antiquus, which was named in the late 1900s from the Gogolin Formation of Poland, was based on vertebrae shorter than those of other Tanystropheus species. Its specimens were subsequently lost until they were rediscovered in the 21st century. T. antiquus is currently considered one of the few valid species of Tanystropheus. 
The best-known valid species of Tanystropheus is T. longobardicus, which comes from the Besano Formation (also known as the Grenzbitumenzone), an Anisian-Ladinian formation exposed at Monte San Giorgio on the Italy-Switzerland border. The first T. longobardicus specimens were described in 1930s, and Monte San Giorgio continues to produce new specimens up to the present day. In 2005, Dr. Silvio Renesto described a T. longobardicus specimen from Switzerland which preserved the impressions of skin and other soft tissue. Five new specimens of T. longobardicus were described by Stefania Nosotti in 2007, allowing for a more comprehensive view of the anatomy of the species. 
Tanystropheus specimens from the Makhtesh Ramon in Israel were described as a new species, T. haasi, in 2001. However, this species may be dubious due to the difficulty of distinguishing its vertebrae from T. conspicuus or T. longobardicus. Another new species, T. biharicus, was described from Romania in 1975. It has also been considered possibly synonymous with T. longobardicus. A small but well-preserved skull and neck, specimen PIMUZ T 3901, was found in the Meride Limestone at Monte San Giorgio. It was given a new species, T. meridensis, in 1980. The skull was later referred to T. longobardicus, rendering T. meridensis a junior synonym of that species. Another species, T. fossai from the Norian-age Argillite di Riva di Solto in Italy, was given its own genus Sclerostropheus in 2019.
Specimens similar to T. longobardicus have been found in the Ladinian or early Carnian Zhuganpo Formation in the Guizhou province of China, as described by Li (2007) and Rieppel (2010). In 2014, fossils of an indeterminate species of Tanystropheus were discovered in the Wolfville Formation in the Bay of Fundy in Nova Scotia, Canada. Indeterminate Tanystropheus remains are also known from the Jilh Formation of Saudi Arabia and various Anisian-Ladinian sites in Spain, Italy, and Switzerland.
A 2019 revision of Tanystropheus found that only T. longobardicus and T. antiquus were valid species. In 2020, large Tanystropheus specimens from Monte San Giorgio originally assigned to T. longobardicus were given a new species, T. hydroides.
Tanystropheus