''Llistrofus'' 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 early

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

microsaur Microsauria ("small lizards") is an extinct, possibly polyphyletic order of tetrapods from the late Carboniferous and early Permian periods. It is the most diverse and species-rich group of lepospondyls. Recently, Microsauria has been considere ...

within the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Hapsidopareiidae Hapsidopareiontidae is an extinct family of tuditanomorph microsaurs. Hapsidopareiontids are known from the Early Permian of the United States and possibly Germany and the Czech Republic. Hapsidopareiontids are characterized by a large tempora ...

that is known from

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

Discovery

''Llistrofus'' was described by Canadian paleontologists Robert Carroll and Pamela Gaskill in 1978. The genus name is an anagram of

Fort Sill Fort Sill is a United States Army post north of Lawton, Oklahoma, about 85 miles (136.8 km) southwest of Oklahoma City. It covers almost . The fort was first built during the Indian Wars. It is designated as a National Historic Landmark ...

, the historic name of the

Richards Spur Richards Spur is a Permian fossil locality located at the Dolese Brothers Limestone Quarry north of Lawton, Oklahoma. The locality preserves clay and mudstone fissure fills of a karst system eroded out of Ordovician limestone and dolomite, with the ...

locality from which material of ''Llistrofus'' was collected. The species name, ''L. pricei'', is given for the Brazilian paleontologist

Llewellyn Price Llewellyn Ivor Price (October 9, 1905 – June 9, 1980) was one of the first Brazilian paleontologists. His work contributed not only to the development of Brazilian but also to global paleontology. He collected '' Staurikosaurus'', the first ...

. The holotype of this taxon is currently reposited at the

Field Museum of Natural History The Field Museum of Natural History (FMNH), also known as The Field Museum, is a natural history museum in Chicago, Illinois, and is one of the largest such museums in the world. The museum is popular for the size and quality of its educational ...

. The skull of the holotype was reappraised by Bolt & Rieppel in 2009. New material from Richards Spur was described by Gee et al. (2019).

Description

''Llistrofus'' is readily identified by the presence of a large temporal emargination, a feature shared with '' Hapsidopareion lepton'' that unites the

. Carroll & Gaskill (1978) differentiated ''Llistrofus'' from ''Hapsidopareion'' by four features: (1)

postorbital The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ve ...

contacting the

tabular Table may refer to: * Table (furniture), a piece of furniture with a flat surface and one or more legs * Table (landform), a flat area of land * Table (information), a data arrangement with rows and columns * Table (database), how the table data ...

; (2)

postparietal Postparietals are cranial bones present in fish and many tetrapods. Although initially a pair of bones, many lineages possess postparietals which were fused into a single bone. The postparietals were dermal bones situated along the midline of the ...

contacting the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal The quadratojugal is a skull bone present in many vertebrates, including ...

; (3) frontals entering the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

; and (4) presence of a

quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...

. Bolt & Rieppel (2009) revised the diagnosis following additional preparation of the holotype's skull and list three features (only one of which is shared with the previous work): (1) skull length approximately twice that of ''Hapsidopareion''; (2) frontals entering the orbit; and (3) cultriform process of the

parasphenoid The parasphenoid is a bone which can be found in the cranium of many vertebrates. It is an unpaired dermal bone which lies at the midline of the roof of the mouth. In many reptiles (including birds), it fuses to the endochondral (cartilage-derived) ...

offset from the basal plate by a narrow base. Gee et al. (2019) further revised the diagnosis based on additional material from Richards Spur and listed 11 features: (1) frontals entering the orbit; (2) prefrontal entering the naris; (3)

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

contributing to ventral narial margin; (4) postfrontal excluded from the temporal emargination; (5) postorbital contacting the tabular; (6) denticles on the

vomer The vomer (; lat, vomer, lit=ploughshare) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxill ...

; (7) teeth on the palatine smaller than the marginal teeth; (8) absence of a pterygoid-premaxilla contact; (9) a

splenial The splenial is a small bone in the lower jaw of reptiles, amphibians and birds, usually located on the lingual side (closest to the tongue) between the angular and surangular The suprangular or surangular is a jaw bone found in most land verteb ...

that contributes to the symphysis; (10) presence of a Meckelian foramen; and (11) presence of a retroarticular process.

Classification

''Llistrofus'' is recovered as the sister taxon to ''Hapsidopareion'' in phylogenetic analyses, producing the

. A 2022 phylogenetic analysis recovered it within

Recumbirostra Recumbirostra is a clade of tetrapods which lived during the Carboniferous and Permian periods. They are thought to have had a fossorial (burrowing) lifestyle and the group includes both short-bodied and long-bodied snake-like forms. At least one ...

References

{{Taxonbar, from=Q6662178 Microsauria

Discovery

Description

Classification

See also

References