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Temporal range: Late Carboniferous, 300 Ma
Spinoaequalis schultzei reconstruction.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Order: Araeoscelidia
Genus: Spinoaequalis
deBraga & Reisz, 1995
  • S. schultzei deBraga & Reisz, 1995 (type)

Spinoaequalis is an extinct genus of diapsid reptile.

The 30 cm (1 ft) long creature, known from fossils found in Kansas, United States, was one of the first diapsids, along with Petrolacosaurus. It was also the first reptile to return to the water, evolving shortly after Hylonomus, the oldest confirmed reptile. Spinoaequalis was not fully aquatic, frequently returning to dry land. It probably swam using its laterally flattened, fanned tail. Its name means "symmetrical spine" referring to its deep, laterally compressed tail. Spinoaequalis has been found along with beautifully preserved marine fish, suggesting it occasionally left fresh water streams for the sea.

Spinoaequalis was described and named by Michael deBraga and Robert Reisz in 1995.[1]


  1. ^ deBraga, Michael; Reisz, Robert R. (1995). "A new diapsid reptile from the uppermost Carboniferous (Stephanian) of Kansas" (PDF). Palaeontology. 38 (1): 199–212. Archived from the original (pdf) on 2011-09-28.