Estemmenosuchidae
Encyclopedia
Estemmenosuchidae are a family
of large, very early herbivorous
mammal-like reptiles (therapsids) that flourished during the Middle Permian
period. They are distinguished by horn-like structures, probably for display
or agonistic behavior. Apart from the best known genus, Estemmenosuchus
, the group is poorly known. To date, their fossils are known only from the Perm
region of Russia (a region referred to by Russian paleontologists as the Cis-Urals).
. The high and massive skull is equipped with a number of horns projecting both upwards and outwards, which were probably used for intra-specific display. The incisor
s and canine teeth are large, but those at the side are reduced, with a serrated apex, and may have helped to break up plant material, although they were too small to be of much use. The body is large and bulky, indicating a large digestive tract for digesting volumes of plant food. The skull superficially resembles that of Styracocephalus
, but the "horns" are formed from different bones.
n group, a group of early, primitive, but diverse therapsids – often of large size – that are known only from the Middle Permian period. They are however far more primitive and unspecialised than the better known dinocephalians of the South African Karoo
(Beaufort Group
), and mostly lived somewhat earlier. They are also unusual in that, despite their primitive nature and early date of appearance, they show herbivorous adaptations.
Because of this, there have been two main interpretations of their evolutionary relationships with other Dinocephalia.
Hopson and Barghusen in 1986, who provided the first cladistic
study of the Therapsida, coined the term Tapinocephalia
for herbivorous dinocephalians, as opposed to the "Anteosaur
ia" for the carnivorous forms. They suggested that Estemmenosuchids are very early/primitive members of the Tapinocephalia
.
However Thomas Kemp (1982) and Gillian King
(1988) argue instead that the Estemmenosuchidae are the most basal
Dinocephalia, being more primitive than
both the Anteosauria and the Tapinocephalia.
as the dominant megaherbivores of the Wordian
age (middle of the Middle Permian), before being themselves replaced by the Tapinocephalidae
during the Capitanian
age (late Middle Permian).
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...
of large, very early 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...
mammal-like reptiles (therapsids) that flourished during the Middle 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. They are distinguished by horn-like structures, probably for display
Animal communication
Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...
or agonistic behavior. Apart from the best known genus, Estemmenosuchus
Estemmenosuchus
Estemmenosuchus is a genus of large, early omnivorous therapsid that lived during the middle part of the Middle Permian period. It was among the largest animals of its day, and is characterised by distinctive horn-like structures, probably for intra-specific display...
, the group is poorly known. To date, their fossils are known only from the Perm
Perm
Perm is a city and the administrative center of Perm Krai, Russia, located on the banks of the Kama River, in the European part of Russia near the Ural Mountains. From 1940 to 1957 it was named Molotov ....
region of Russia (a region referred to by Russian paleontologists as the Cis-Urals).
Description
Estemmenosuchids are among the most distinctive of the Permian tetrapodsPermian tetrapods
Permian Tetrapods were amphibians and reptiles that lived during the Permian Period.During this time, amphibians remained common, including various Temnospondyli and Lepospondyli...
. The high and massive skull is equipped with a number of horns projecting both upwards and outwards, which were probably used for intra-specific display. The incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and canine teeth are large, but those at the side are reduced, with a serrated apex, and may have helped to break up plant material, although they were too small to be of much use. The body is large and bulky, indicating a large digestive tract for digesting volumes of plant food. The skull superficially resembles that of Styracocephalus
Styracocephalus
Styracocephalus is an extinct genus of Tapinocephalia.-References:* The Origin and Evolution of Mammals by T. S. Kemp*...
, but the "horns" are formed from different bones.
Evolutionary Relationships
Estemmenosuchids belong to the DinocephaliaDinocephalia
Dinocephalia are a clade of large early therapsids that flourished during the Middle Permian, but became extinct leaving no descendants.-Description:...
n group, a group of early, primitive, but diverse therapsids – often of large size – that are known only from the Middle Permian period. They are however far more primitive and unspecialised than the better known dinocephalians of the South African Karoo
Karoo Supergroup
The Karoo Supergroup is the largest stratigraphic unit in Southern Africa, covering almost two thirds of the present land surface, including central Cape Province, almost all of Orange Free State, western Natal, much of south-east Transvaal, Zambia, Zimbabwe and Malawi...
(Beaufort Group
Beaufort Group
The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup of geological strata in Southern Africa. It follows conformably after the Ecca Group and consists essentially of sandstones and shales, deposited in the Karoo Basin from the Middle Permian to the early part of the...
), and mostly lived somewhat earlier. They are also unusual in that, despite their primitive nature and early date of appearance, they show herbivorous adaptations.
Because of this, there have been two main interpretations of their evolutionary relationships with other Dinocephalia.
Hopson and Barghusen in 1986, who provided the first cladistic
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
study of the Therapsida, coined the term Tapinocephalia
Tapinocephalia
The tapinocephalians are one of the major groups of dinocephalian therapsids. Unlike anteosaurs and estemmenosuchids, tapinocephalians are mainly from Africa and only one species is found in the north - Ulemosaurus from Russia. The tapinocephalians are divided into three clades, Styracocephalidae,...
for herbivorous dinocephalians, as opposed to the "Anteosaur
Anteosaur
Anteosaurs are a group of large, primitive carnivorous Dinocephalians , with huge canines and incisors and short limbs, that are known from the Middle Permian of South Africa, Russia, and China. The largest grew to very large size, with skulls 50 to 80 cm long, and were the largest predators...
ia" for the carnivorous forms. They suggested that Estemmenosuchids are very early/primitive members of the Tapinocephalia
Tapinocephalia
The tapinocephalians are one of the major groups of dinocephalian therapsids. Unlike anteosaurs and estemmenosuchids, tapinocephalians are mainly from Africa and only one species is found in the north - Ulemosaurus from Russia. The tapinocephalians are divided into three clades, Styracocephalidae,...
.
However Thomas Kemp (1982) and Gillian King
Gillian King
Gillian King has worked in teaching and research in paleontology, as Assistant Curator at the Zoological Collections at Oxford University Museum, and a Fellow and Tutor as St Hilda's College, Oxford. She spent 15 years at Oxford and five years at the South African Museum in Cape Town, where she...
(1988) argue instead that the Estemmenosuchidae are the most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
Dinocephalia, being more primitive than
Outgroup
In cladistics or phylogenetics, an outgroup is a group of organisms that serves as a reference group for determination of the evolutionary relationship among three or more monophyletic groups of organisms....
both the Anteosauria and the Tapinocephalia.
Ecological succession
The Estemmenosuchids replaced the caseidsCaseidae
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...
as the dominant megaherbivores of the Wordian
Wordian
In the geologic timescale, the Wordian is an age or stage of the Permian. It is the middle of three subdivisions of the Guadalupian epoch or series. The Wordian lasted between 268.0 ± 0.7 and 265.8 ± 0.7 million years ago...
age (middle of the Middle Permian), before being themselves replaced by the Tapinocephalidae
Tapinocephalidae
Tapinocephalidae is an advanced family of tapinocephalians. They were all herbivores. They were giants of their time, weighing from 500 to 1000 kg and possibly over 1 or 2 tonnes in weight. They are known from South Africa and Russia. The tapinocephalid skull is very thick, probably used for...
during the Capitanian
Capitanian
In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian epoch or series. The Capitanian lasted between and...
age (late Middle Permian).