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 botanical subfamily names with "-oideae", and zo ...

anguid Anguidae refers to a large and diverse family of lizards native to the Northern Hemisphere. It contains 9 genera and 89 extant species. Common characteristics of this group include a reduced supratemporal arch, striations on the medial faces of t ...

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 by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

and the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

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 amph ...

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 Anguimorpha, 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 ''Gobid ...

, 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 Mexico, Mexican state of Sonora. It is a heavy, slow-moving reptile, up to long, and it is the only ve ...

and

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

. 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 (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...

(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 Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

(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 animals, including some species of fish. It makes up the normally visible part of the tooth, covering the Crown (tooth), crown. The other ...

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 () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses show that Melanosaurini in its traditional sense is

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, 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. Phylogenetics The concept of evolutionary grades ...

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

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

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'' 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. Campa ...

) 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) * Ar ...

". The youngest known remains of glyptosaurines is '' Peltosaurus granulosus'' from the Monroe Creek and upper Sharps formations of

Sharps Corner, South Dakota Sharps Corner is an unincorporated community in Oglala Lakota County, South Dakota, United States. The locale is contained within the Pine Ridge Indian Reservation The Pine Ridge Indian Reservation (), also called Pine Ridge Agency, is an Ogl ...

, dating to the mid

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

, between 27.4 and 26.4 million years ago. The extinction of glyptosaurines was likely due to a cooling climate during the Oligocene.

References

Anguidae Late Cretaceous first appearances Oligocene extinctions Reptile subfamilies {{paleo-lizard-stub