Paramacellodidae is an extinct

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 ...

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s that first appeared in the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

around 170 million years ago (Ma) and became extinct at the end of the Cretaceous around 66 Ma. It was one of the earliest groups of lizards to have undergone an evolutionary radiation, with members found across the supercontinent

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...

. The phylogenetic relationships and constituent species of Paramacellodidae are uncertain. Many studies regard them to be scincomorphs, a large group that includes

skink Skinks are lizards belonging to the family Scincidae, a family in the infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. Ski ...

s and their closest extinct relatives, and possibly also to Cordyoidea, a group that includes

spinytail lizard The genus ''Cordylus'' (Sauria: Cordylidae) includes a wide variety of species of small to medium spiny lizards from Africa, collectively called girdle-tailed lizards or girdled lizards. All are diurnal and ovoviviparous (live-bearing, without she ...

s and relatives. Like modern skinks, paramacelloidids had rectangular bony plates called

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s covering most of their bodies, including their backs, undersides, and tails. They also had short and robust limbs. Paramacellodids are distinguished from other lizards by the combination two traits in their dentition, the teeth are labiolingually expanded at their bases, and the tooth apices are lingually concave. The family was named in 1983 to include two well-known genera, ''

Paramacellodus ''Paramacellodus'' is an extinct genus of scincomorph lizards from the Early Cretaceous of England and France, and the Late Jurassic of Portugal and the western United States. The type species, ''Paramacellodus oweni'', was named in 1967 from the ...

'' and ''

Becklesius ''Becklesius'' is an extinct genus of Paramacellodid lizard known from the Late Jurassic to Late Cretaceous of Europe, the type species, ''B. hoffstetteri'' is known from Kimmeridgian aged sediments of the Alcobaça Formation in Portugal. An in ...

'', from the Late Jurassic and Early Cretaceous of Europe. A third genus, ''

Sharovisaurus ''Sharovisaurus'' is an extinct genus of scincomorph lizard from the Late Jurassic of Kazakhstan. It belongs to an extinct family of Mesozoic lizards called Paramacellodidae, which existed across most of Laurasia during the Late Jurassic and Earl ...

'', was named in 1984 from the Late Jurassic of Kazakhstan, and a fourth, '' Mimobecklesisaurus'', in 1985 from the Late Jurassic of China. Remains of ''Paramacellodus'' were later described from the

Morrison Formation The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...

in Utah. Possible paramacellodid remains have also been found in Late Cretaceous deposits in Mongolia, as well as the Late Jurassic Tendaguru Formation in Tanzania, which would indicate that the family was also present in

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

. In 2020, this was confirmed with the discovery of the first paramacellodid from Brazil, ''Neokotus sanfranciscanus'', from the Early Cretaceous Sanfranciscana Basin. Three other early scincomorphs—''

Pseudosaurillus ''Pseudosaurillus'' is a genus of extinct lizard from the Early Cretaceous of southern England. The type and only species is ''Pseudosaurillus becklesi'', named in 1967 by R. Hoffstetter limited jaw and tooth material from the Berriasian Lulworth ...

'', '' Saurillodon'', and '' Saurillus''—have also commonly been referred to Paramacellodidae, although some recent phylogenetic studies find them to be non-paramacellodid scincomorphs. Collectively, paramacellodids and taxa formerly referred to Paramacellodidae may represent a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

grade of basal scincomorphs closely related to Scincoidea. In 2002, the newly named genus ''

Atokasaurus ''Atokasaurus'' is an extinct genus of scincomorph lizard from the Early Cretaceous of Oklahoma. The type and only species is ''Atokasaurus metarsiodon'', named in 2002 on the basis of a single isolated lower jaw bone found within the Antlers Fo ...

'' from the Early Cretaceous Antlers Formation in Oklahoma was described as a "paramacellodid-grade" scincomorph to reflect this phylogenetic ambiguity. In the Late Cretaceous, paramacellodids are only known from the European Archipelago.

References

{{Taxonbar, from=Q16587035 Jurassic lizards Cretaceous lizards Lizard families Prehistoric reptile families Middle Jurassic reptiles Late Jurassic reptiles Early Cretaceous reptiles Middle Jurassic first appearances Early Cretaceous extinctions