''Suzanniwana'' 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 ...

iguania Iguania is an infraorder of squamate reptiles that includes iguanas, chameleons, agamids, and New World lizards like anoles and phrynosomatids. Using morphological features as a guide to evolutionary relationships, the Iguania are believed ...

n lizards that lived in western North America during the earliest

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 ...

, approximately 56 million years ago. Two species are known from the

Bighorn Basin The Bighorn Basin is a plateau region and intermontane basin, approximately 100 miles (160 km) wide, in north-central Wyoming in the United States. It is bounded by the Absaroka Range on the west, the Pryor Mountains on the north, the Bigho ...

of Wyoming: the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

''S. patriciana'' named in 2009, and the species ''S. revenanta'' named in 2013. ''Suzanniwana'' lived during the

Paleocene–Eocene Thermal Maximum The Paleocene–Eocene thermal maximum (PETM), alternatively ”Eocene thermal maximum 1 (ETM1)“ and formerly known as the "Initial Eocene" or “Late Paleocene thermal maximum", was a geologically brief time interval characterized by a ...

, a brief period of

global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

that resulted in warmer and drier conditions in the Bighorn Basin. It likely stemmed from a lineage that had migrated into the basin from regions farther to the south, following a latitudinal band of constant climatic conditions that moved northward as the planet warmed (a phenomenon known as habitat tracking). ''Suzanniwana'' shares many skeletal features with modern casquehead lizards of the family

Corytophanidae Corytophanidae is a family of iguanian lizards, also called casquehead lizards or helmeted lizards, endemic to the New World. Nine species of casquehead lizards from three genera are recognized. Geographic range Corytophanids are found from Mex ...

and may be a

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

-corytophanid. It also closely resembles '' Geiseltaliellus'', an iguanian from the middle Eocene

Messel pit The Messel Formation is a Formation (geology), geologic formation in Hesse, central Germany, dating back to the Eocene Epoch (geology), epoch (about 47 Ma). Its geographic range is restricted to the Messel pit. There it unconformably overlie ...

in Germany.

References

Eocene lepidosaurs Corytophanidae Paleogene animals of North America Fossil taxa described in 2009 {{paleo-lizard-stub