Holotype lumbar vertebra of Tregophis braevirachis MSU-W 783. Figure F from Holman (1975): (a) dorsal view, (b) posterior view, (c) ventral view, (d) anterior view.
Vertebrae of Tregophis brevirachis in dorsal view: (A) UNSM 100256, (B) UNSM 100254. Scale bars = 2 mm. From Parmley and Hunter (2010).
Holotype trunk vertebra (MSUVP 783) of Tregophis brevirachis Holman, from Trego County, Kansas. Clockwise from top left: dorsal, ventral, anterior, and posterior aspects. Line = 2 mm. From Holman (2000).
REPTILIA (Reptiles) SQUAMATA (PART) (Snakes) BOIDAE (Boas)

Kansas Dwarf Boa
Tregophis brevirachis Holman, 1975

Conservation Status:


A small erycine boid. Holman (1975) suggested that the taxon differed from all other known extinct and extant North American boids mainly in having the posterior margin of the neural arch deeply incised but, also, in having a short, thick, triangular neural spine (viewed from above) and an indistinct hemal keel.
Based on the size of the Wakeeney and Pratt Slide vertebrae (length through the pre- and postzygapophysis: Wakeeney vertebra 2.8 mm (0.11 in); mean of Pratt Slide vertebrae, 3.7 mm (0.15 in)) compared with modern Lichanura vertebrae, this erycine was a snake in the approximately 600–750 mm (23.6-27.6 in) total length range.

Originally described from a single trunk vertebra from the Wakeeney local fauna (Miocene: late Clarendonian [10.5–9.5 Ma]) of Trego County, Kansas (Holman, 1975). It is also known three trunk vertebrae (UNSM 100254, 100256, 100257) discovered at the Pratt Slide local fauna (Miocene: late Clarendonian [10.5–9.5 Ma]) in Brown County, Nebraska.
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  • Occurrence Summary:  
  • 2
  • 2
    Museum Vouchers 
  • 0
    Other Observations 
Some county occurrences indicated below may be too imprecise to map above.
County Breakdown: County Name (# occurrences):
Trego (2);

Natural History:

On the basis of its vertebral uniqueness and because only one vertebra was known, Rage (1977, 1984) questioned the generic validity of Tregophis. As did Holman (2000). More recently, an additional three vertebrate were presented in Parmley and Hunter (2010).

1975 Holman, J. Alan. Herpetofauna of the WaKeeney local fauna (Lower Pliocene: Clarendionian) of Trego County, Kansas. Pages 49-66 in Studies on Cenozoic Paleontology and Stratigraphy in honor of Claude W. Hibbard. Museum of Paleontology, The University of Michigan, Ann Arbor, Michigan. pp.
2000 Holman, J. Alan. Fossil snakes of North America: Origin, evolution, distribution, paleoecology. Indian University Press, Bloomington. 357pp.
2010 Parmley, Dennis and Katie Beth Hunter. Fossil snakes of the Clarendonian (Late Miocene) Pratt Slide Local Fauna of Nebraska, with the description of a new Natricine Colubrid. Journal of Herpetology 44(4):526-543
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Travis W. Taggart © 1999-2024 — w/ Sternberg Museum of Natural History, Fort Hays State University