''Dyticonastis'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

amphisbaenia Amphisbaenia (called amphisbaenians or worm lizards) is a group of typically legless lizards, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. A ...

ns, or worm lizards, that includes a single species, ''Dyticonastis rensbergeri'', that lived during the late

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

and early

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

in what is now Oregon. Fossils of the species come from the John Day Formation. It belongs to

Rhineuridae Rhineuridae is a family of amphisbaenians (commonly called worm lizards) that includes one living genus and species, '' Rhineura floridana'', as well as many extinct species belonging to both ''Rhineura'' and several extinct genera. The living '' ...

, a family that includes many other extinct North American amphisbaenians but only one living species, ''

Rhineura floridana ''Rhineura floridana'', known commonly as the Florida worm lizard, graveyard snake, or thunderworm, is a species of amphisbaenian in the family Rhineuridae. The species is the only extant member of the genus ''Rhineura'', and is found primarily ...

'', from Florida. ''Dyticonastis rensbergeri'' occurs the farthest west of all rhineurid species. Like all rhineurids, ''Dyticonastis'' has a shovel-like snout adapted for burrowing underground, but it differs from most other members of the group in having a relatively shallow angle to its snout wedge (about 30 degrees) and in having a widened snout tip. The only other rhineurids that share these features are species of the genus ''

Spathorhynchus ''Spathorhynchus'' is an extinct genus of amphisbaenians or worm lizards that existed from the Middle Eocene to the Early Oligocene in what is now Wyoming. It includes two species, the type species ''S. fossorium'', named in 1973 from the Middle ...

'', which lived from the Middle

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

to the Early Oligocene in what is now Wyoming. A 2007,

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

of amphisbaenians found that ''Dyticonastis'' and ''Spathorhynchus'' are each other's closest relatives, suggesting that both taxa may have evolved through vicariant speciation; the growth of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...

during the earliest stages of the

Laramide orogeny The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 80 to 70 million years ago, and ended 55 to 35 million years ago. The exact duration and ages of beginning and end of the o ...

in the early

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

would have separated North American rhineurids into eastern and western populations, with the western population producing ''Dyticonastis'' and ''Spathorhynchus''.

References

Amphisbaenia Oligocene lepidosaurs Miocene lepidosaurs Oligocene reptiles of North America Miocene reptiles of North America Prehistoric lizard genera Fossil taxa described in 1976 {{paleo-lizard-stub