the fifth toe was very long, filling a metatarsal-like role as seen in other tanystropheids. Classification Historical interpretations (1920s-1980s) Knowledge on the anatomy of Tanystropheus was transformed by Bernhard Peyer’s discoveries in the 1920s and 1930s, but its relationship to other reptiles remained enigmatic for much of the 20th century. Most paleontologists (including modern authorities) agree that Tanystropheus was closely related to Macrocnemus, a smaller and less specialized reptile found in the same geological strata. Beyond this conclusion, Peyer initially suggested that Tanystropheus was related to other long-necked Triassic reptiles. Sauropterygians such as plesiosaurs and nothosaurs were one possibility, and another was the fragmentary German reptile Trachelosaurus. Later, Peyer classified Tanystropheus and Macrocnemus closer to “protorosaurs”, a term initially used for Permian reptiles such as Protorosaurus and Araeoscelis. In the early and mid-20th century, it was commonplace for Permian and Triassic reptiles of uncertain affinity to intermingle together in classification schemes. Names such as “Eosuchia”, “Euryapsida”, "Younginiformes", “Protorosauria”, and others were all applied by different authors with little consistency. The Early Triassic reptile Prolacerta, from South Africa, also became involved upon its discovery. Prolacerta was the namesake of yet another term introduced into the convoluted space of reptile taxonomy: “Prolacertiformes”. As the century progressed, two competing hypotheses for the affinities of Tanystropheus developed from the groundwork set by Peyer. Both hypotheses were justified by patterns of skull fenestration (the shape of holes in the skull behind the eye) and cranial kinesis (the flexibility of joints within the skull). One idea was that Tanystropheus and kin (particularly Macrocnemus and Prolacerta) were ancestral to “lacertilian”, an antequated term for lizards. This hypothesis was supported up until the 1980s by German and Swiss paleontologists, including Rupert Wild, and Peyer’s successor at Zürich, Emil Kuhn-Schnyder. The other idea maintained that Tanystropheus was a “protorosaur”, closer to Protorosaurus and Araeoscelis and unrelated to Prolacerta. This was popular among American paleontologists like Alfred Romer. Some publications from the mid-20th century argued that "protorosaurs" were "euryapsids" (reptiles with only an upper temporal fenestra) related to sauropterygians, though later accounts admitted that Euryapsida was likely polyphyletic, with its members lacking a common ancestor. In 1975, a paper by South African paleontologist C.E. Gow argued that none of these hypotheses were entirely correct. He proposed that Prolacerta, and by extension Macrocnemus and Tanystropheus, occupied an extinct spur on the reptile family tree near the ancestry of archosaurs, a diverse