Pareiasaur
Encyclopedia
The Pareiasaurs - Family
Pareiasauridae - are a clade
of medium-sized to large herbivorous
anapsid
reptiles that flourished during the Permian
period.
Their build was quite stocky, often with rather short tails and small heads. These ungainly-looking animals had very large bodies, ranging from 60 to 300 cm (2 to 9.8 ft) long, and weights of 600 kilograms (1,322.8 lb) would not have been unusual. They also had strong limbs, broad feet, and short tails. They were protected with bony scute
s (osteoderm
s) set in the skin, as a defense against predators. Their heavy skull
s were ornamented with multiple knobs and ridges.
The leaf-shaped multi-cusped teeth resemble those of iguana
s, caseids
, and other reptilian herbivores. This dentition, together with the deep capacious body, which could have housed an extensive digestive tract, indicate that these fearsome-looking animals were herbivore
s.
Michael Lee has argued that pareiasaurs include the direct ancestors of modern turtle
s. They had turtle-like skull features, and in several genera the scutes had developed into bony plates, possibly the precursors of a turtle shell. Jalil and Janvier, in a large analysis of pareiasaur relationships, also found turtles to be close relatives of the "dwarf" pareiasaurs, such as Pumiliopareia. However, the exact relationships of turtles remains controversial, and critics have argued that pareiasaur scutes are not homologous
with the turtle shell.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Pareiasauridae - are a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of medium-sized to large herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
anapsid
Anapsid
An anapsid is an amniote whose skull does not have openings near the temples.While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related...
reptiles that flourished during the Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
period.
Their build was quite stocky, often with rather short tails and small heads. These ungainly-looking animals had very large bodies, ranging from 60 to 300 cm (2 to 9.8 ft) long, and weights of 600 kilograms (1,322.8 lb) would not have been unusual. They also had strong limbs, broad feet, and short tails. They were protected with bony scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s (osteoderm
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
s) set in the skin, as a defense against predators. Their heavy skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
s were ornamented with multiple knobs and ridges.
Iguana
Iguana is a herbivorous genus of lizard native to tropical areas of Central America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena...
s, caseids
Caseidae
The Caseidae were a widespread group of very primitive herbivorous synapsids, which appeared during the later early Permian and persisted until the late middle Permian. Although ranging in size from 1 to 5½ meters in body length, caseids were surprisingly conservative in their skeletal anatomy and...
, and other reptilian herbivores. This dentition, together with the deep capacious body, which could have housed an extensive digestive tract, indicate that these fearsome-looking animals were herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s.
Michael Lee has argued that pareiasaurs include the direct ancestors of modern turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s. They had turtle-like skull features, and in several genera the scutes had developed into bony plates, possibly the precursors of a turtle shell. Jalil and Janvier, in a large analysis of pareiasaur relationships, also found turtles to be close relatives of the "dwarf" pareiasaurs, such as Pumiliopareia. However, the exact relationships of turtles remains controversial, and critics have argued that pareiasaur scutes are not homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
with the turtle shell.