All Topics  
Mammaliaformes

 

 
   Email Print
   Bookmark   Link
 

 

Mammaliaformes
 
 
  Topics Mammaliaformes Topic Home

Mammaliaformes ("mammal-shaped") is a clade
Clade

A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.The term "monophyletic group" is used in this article in the conventional sense of "an a...
 that contains the mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s and their closest extinct
Extinction

In biology and ecology, extinction is the death of every member of a species or group of taxon. The moment of extinction is generally considered to be the death of the last individual of that species ....
 relatives. The precise phylogeny
Phylogenetics

In biology, phylogenetics is the study of evolutionary relatedness among various groups of organisms , which is discovered through molecular sequencing data and morphological data matrices....
 is disputed due to the scantness of evidence in the fossil record. However, it is thought that the Mammaliaformes were of three major groups: Allotheria
Multituberculata

The Multituberculata are a major branch of mammalia that survived for a long period of time but eventually became completely extinct at the end of the Paleogene period....
, the longest extinct lineage of pre-mammals; Docodonta
Docodonta

Docodonta is an order of extinct proto-mammals that lived during the mid- to late-Mesozoic era. Their most distinguishing physical features were their relatively sophisticated set of Molar , from which the order gets its name....
, including close relatives such as Morganucodon
Morganucodon

Morganucodon is an early mammalian genus which lived during the Upper Triassic. It first appeared about 205 million years ago. This has also been identified with Eozostrodon....
ta; and Symmetrodonta
Symmetrodonta

Symmetrodonta is a basal group of Mesozoic mammals characterized by the triangular aspect of the Molar s when viewed from above and the absence of a well-developed talonid....
, 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 form an outgroup to the rest of the clade, such as in the following example:...
 of modern mammals. Mammaliaformes radiated
Adaptive radiation

An adaptive radiation is a rapid evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single, rapidly diversifying lineage....
 from Cynodont
Cynodont

Cynodonts, or 'dog teeth', are a taxon of Therapsids which includes modern mammals and their extinct close relatives. They were one of the most diverse groups of therapsids....
ia.






Discussion
Ask a question about 'Mammaliaformes'
Start a new discussion about 'Mammaliaformes'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Mammaliaformes ("mammal-shaped") is a clade
Clade

A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.The term "monophyletic group" is used in this article in the conventional sense of "an a...
 that contains the mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s and their closest extinct
Extinction

In biology and ecology, extinction is the death of every member of a species or group of taxon. The moment of extinction is generally considered to be the death of the last individual of that species ....
 relatives. The precise phylogeny
Phylogenetics

In biology, phylogenetics is the study of evolutionary relatedness among various groups of organisms , which is discovered through molecular sequencing data and morphological data matrices....
 is disputed due to the scantness of evidence in the fossil record. However, it is thought that the Mammaliaformes were of three major groups: Allotheria
Multituberculata

The Multituberculata are a major branch of mammalia that survived for a long period of time but eventually became completely extinct at the end of the Paleogene period....
, the longest extinct lineage of pre-mammals; Docodonta
Docodonta

Docodonta is an order of extinct proto-mammals that lived during the mid- to late-Mesozoic era. Their most distinguishing physical features were their relatively sophisticated set of Molar , from which the order gets its name....
, including close relatives such as Morganucodon
Morganucodon

Morganucodon is an early mammalian genus which lived during the Upper Triassic. It first appeared about 205 million years ago. This has also been identified with Eozostrodon....
ta; and Symmetrodonta
Symmetrodonta

Symmetrodonta is a basal group of Mesozoic mammals characterized by the triangular aspect of the Molar s when viewed from above and the absence of a well-developed talonid....
, 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 form an outgroup to the rest of the clade, such as in the following example:...
 of modern mammals. Mammaliaformes radiated
Adaptive radiation

An adaptive radiation is a rapid evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single, rapidly diversifying lineage....
 from Cynodont
Cynodont

Cynodonts, or 'dog teeth', are a taxon of Therapsids which includes modern mammals and their extinct close relatives. They were one of the most diverse groups of therapsids....
ia. The Probainognathia
Probainognathia

The Probainognathians are a group of mostly carnivore cynodonts, and are one of the two main branches of the infraorder Eucynodontia, the other being the mainly herbivore Cynognathia....
ns of the Eucynodont clade probably evolved into the early mammaliaformes, but the branch Allotheria
Allotheria

Allotheria was a branch of successful mesozoic mammals. The most important characteristic was the presence of lower Molar Tooth equipped with two longitudinal rows of cusps....
 was so different that they may have come from an entirely different group of cynodonts.

Early mammaliforms were generally rodent
Rodent

Rodentia is an Order of mammals also known as rodents, characterised by two continuously growing Incisors#The_Rodent_incisor in the upper and lower jaws which must be kept short by gnawing....
-like in appearance and size, and most of their distinguishing characteristics were internal. In particular, the structure of the mammaliform (and mammal) jaw
Jaw

The jaw is either of the two opposable structures forming, or near the entrance to the mouth.The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals....
 and arrangement of teeth is nearly unique. Instead of having many teeth that are frequently replaced, mammals have one set of baby teeth and later one set of adult teeth which fit together precisely. This is thought to aid in the grinding of food to make it quicker to digest. Being warm-blooded requires more calories than "cold-blooded" animals, so quickening the pace of digestion is a necessity. Early mammaliaformes were probably nocturnal.

Mammaliforms have several common structures. Most importantly, mammaliforms have highly specialized molars
Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
, with cusp
Cusp

Cusp may refer to:*Cusp , a singular point of a curve*Cusp form in modular form theory*Cuspidal representation, a generalization of cusp forms in the theory of automorphic representations...
s and flat regions for grinding food. This system is also unique to mammals, although it seems to have evolved convergently
Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action....
 in pre-mammals multiple times.

Lactation
Lactation

Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, and the period of time that a mother lactates to feed her young....
 and fur
Fur

Fur is a Hair of any non-human mammal, also known as the pelage. It may consist of short ground hair, long guard hair, and, in some cases, medium awn hair....
, along with other characteristically mammalian features, are also thought to characterize the Mammaliaformes, but these traits are difficult to study in the fossil record. The fossilized remains of Castorocauda lutrasimilis
Castorocauda lutrasimilis

Castorocauda lutrasimilis is the name given to a small, semi-aquatic relative of mammals living in the middle Jurassic period, 164 million years ago, in lakebed sediments of the Daohugou Beds of Inner Mongolia....
 are a unique exception.

Some non-mammal mammaliformes still retain reptile
Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
-like traits. Some mammaliformes had reptile
Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
-like locomotion. Furthermore, these mammaliformes still had some bones on their lower jaw seen in reptiles.

Phylogeny

Cladogram from an online synthesis by Mikko Haaramo.

External links



See also

  • Evolution of mammals
    Evolution of mammals

    __FORCETOC__The evolution of mammals from synapsids was a gradual process which took approximately 70 million years, beginning in the mid-Permian....
  • Vertebrate paleontology
    Vertebrate paleontology

    Vertebrate paleontology seeks to discover the behavior, reproduction and appearance of extinct animals with vertebrae or a notochord, through the study of their fossilized remains....
  • Therapsid