Glyptosaurinae is an extinct

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

anguid Anguidae refers to a large and diverse family of lizards native to the Northern Hemisphere. Common characteristics of this group include a reduced supratemporal arch, striations on the medial faces of tooth crowns, osteoderms, and a lateral fold ...

lizards that lived in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

and 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 ...

Description

Glyptosaurines are known primarily from their

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, scale-like pieces of bone that are embedded in the skin and cover much of their bodies. The shape and extent of the osteoderms in glyptosaurines are similar to those seen in an unrelated group of lizards called

Monstersauria Monstersauria is a clade of anguimorph lizards, defined as all taxa more closely related to ''Heloderma'' than '' Varanus''. It includes ''Heloderma'', as well as several extinct genera, such as '' Estesia'', '' Primaderma'' and '' Gobiderma'', ...

, which includes the living

Gila monster The Gila monster (''Heloderma suspectum'', ) is a species of venomous lizard native to the Southwestern United States and the northwestern Mexican state of Sonora. It is a heavy, typically slow-moving reptile, up to long, and it is the only v ...

and

beaded lizard The Mexican beaded lizard (''Heloderma horridum'') is a species of lizard in the Family (biology), family Helodermatidae, one of the two species of venomous beaded lizards found principally in Mexico and southern Guatemala. It and congener (biolo ...

. The osteoderms of glyptosaurines are unusually complex, consisting of four distinct layers of bony tissue. These tissues may have derived from both the

dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...

(the lower layer of the skin) and the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

(the outer layer of the skin) during their development in the embryo. The tissue forming the outermost layer of glyptosaurine osteoderms is similar to

tooth enamel Tooth enamel is one of the four major Tissue (biology), tissues that make up the tooth in humans and many other animals, including some species of fish. It makes up the normally visible part of the tooth, covering the Crown (tooth), crown. The ...

and has even been given its own name, osteodermine. Glyptosaurines have been split into the subgroups Melanosaurini and Glyptosaurini, although recent

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analyses show that Melanosaurini in its traditional sense is

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 ...

, representing an

evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Definition An evolutionary grade is a group of ...

of glytosaurines more basal ("primitive") than Glyptosaurini. Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

from Conrad and Norell (2008) showing the interrelationships of glyptosaurines and their relationship to other anguid lizards:

Evolutionary history

The earliest known Glyptosaurines like ''

Odaxosaurus ''Odaxosaurus'' is an extinct genus of anguid lizards that existed in western North America from the Late Cretaceous to the Paleocene. Fossils of the type species ''Odaxosaurus piger'' and the species ''O. priscus'' are widespread throughout Late ...

'' are known from the

(

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

) of North America. They arrived in Europe at the beginning of the Eocene (

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

). Only a single species, '' Stenoplacosaurus mongoliensis'' dating to the Mid-Eocene, is known from Asia. Glyptosaurines declined after the Mid-Eocene, become extinct in Europe by the end of the period as part of the "

Grande Coupure Grande means "large" or "great" in many of the Romance languages. It may also refer to: Places * Grande, Germany, a municipality in Germany *Grande Communications, a telecommunications firm based in Texas *Grande-Rivière (disambiguation) *Arroi ...

". The youngest known remains of glyptosaurines is '' Peltosaurus granulosus'' from the Monroe Creek and upper Sharps formations of Sharps Corner, South Dakota, dating to the mid

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 ...

, between 27.4 and 26.4 million years ago.

References

Anguids Late Cretaceous first appearances Cretaceous lizards Paleocene lepidosaurs Eocene lizards Oligocene lepidosaurs Paleogene extinctions Prehistoric reptiles of Asia Prehistoric reptiles of Europe Prehistoric reptiles of North America Fossil taxa described in 1872 {{paleo-lizard-stub