Macrorhineura

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Macrorhineura
Temporal range: Early Miocene
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Rhineuridae
Genus: Macrorhineura
MacDonald, 1970
Type species
Macrorhineura skinneri
MacDonald, 1970
Macrorhineura skinneri Macrorhineura skinneri.png
Macrorhineura skinneri

Macrorhineura is an extinct genus of rhineurid amphisbaenian 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 Sharps Formation in Wounded Knee, South Dakota. 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 and Hyporhina , two genera from the Eocene and Oligocene of Colorado and Wyoming, based on the shared feature of equally sized dentary teeth in the lower jaw. Together they form a clade 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, but their range contracted in the Neogene as the climate became colder, leaving only one living species in Florida, 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. [1]

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Dyticonastis is an extinct genus of amphisbaenians, or worm lizards, that includes a single species, Dyticonastis rensbergeri, that lived during the late Oligocene and early Miocene in what is now Oregon. Fossils of the species come from the John Day Formation. It belongs to Rhineuridae, a family that includes many other extinct North American amphisbaenians but only one living species, Rhineura floridana, 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 and in having a widened snout tip. The only other rhineurids that share these features are species of the genus Spathorhynchus, which lived from the Middle Eocene to the Early Oligocene in what is now Wyoming. A 2007, phylogenetic analysis 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 during the earliest stages of the Laramide orogeny in the early Paleogene would have separated North American rhineurids into eastern and western populations, with the western population producing Dyticonastis and Spathorhynchus.

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Hyaenodonta is an extinct order of hypercarnivorous placental mammals from clade Ferae. Hyaenodonts were important mammalian predators that arose during the early Paleocene in Europe and persisted well into the late Miocene.

References

  1. Hembree, D.I. (2007). "Phylogenetic revision of Rhineuridae (Reptilia: Squamata: Amphisbaenia) from the Eocene to Miocene of North America". The University of Kansas Paleontological Contributions. 15: 1–20.