''Macrorhineura'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of rhineurid

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

n or worm lizard, including the type and only species ''Macrorhineura skinneri'', named in 1970 on the basis of the front half of a skull from the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 Ma to 15.97 ± 0.05 Ma (million years ago). It was prece ...

Sharps Formation in

Wounded Knee, South Dakota Wounded Knee ( lkt, Čaŋkpé Opí) is a census-designated place (CDP) on the Pine Ridge Indian Reservation in Oglala Lakota County, South Dakota, United States. The population was 364 at the 2020 census. The town is named for the Wounded Knee Cr ...

. Although the skull is incomplete, features such as a pointed, shovel-shaped snout indicate that it belongs to the family Rhineuridae. Within Rhineuridae, ''Macrorhineura'' is most closely related to ''

Ototriton ''Ototriton'' is an extinct genus of rhineurid amphisbaenian or worm lizard from the Early Eocene of the western United States, including the type and only species ''Ototriton solidus''. Paleontologist F. B. Loomis named ''Ototriton'' in 1919 ...

'' and '' Hyporhina'', two genera from the

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

and

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

of Colorado and Wyoming, based on the shared feature of equally sized

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

teeth in the lower jaw. Together they form a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

or evolutionary grouping of mid-continental rhineurids, which became isolated from a more western clade of rhineurids that includes '' Dyticonastis'' and '' Spathorhynchus''. Rhineurids were relatively common across much of North America during the

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

, but their range contracted in the

Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...

as the climate became colder, leaving only one living species in Florida, ''

Rhineura floridana ''Rhineura floridana'', known commonly as the Florida worm lizard, graveyard snake, Goin CJ, Goin OB, Zug GR (1978). ''Introduction to Herpetology, Third Edition''. San Francisco: W.H. Freeman and Company. xi + 378 pp. . (''Rhineura floridana ...

''. The presence of ''Macrorhineura'' in the Miocene shows that mid-continental rhineurids persisted into the Neogene, although by this time their distribution range was already shrinking.

References

Amphisbaenians Miocene lepidosaurs Miocene reptiles of North America Prehistoric lizard genera Fossil taxa described in 1970 {{paleo-lizard-stub