Sub-articulated animals
| Sub-articulated animals | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
.jpg)
Giant anteater ( Myrmocophaga tridactyla ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Xenarthra | ||||||||||||
| Cope , 1889 |
A , side view of the twelfth and thirteenth thoracic vertebrae. B , back of the second lumbar vertebra. C , anterior view of the third lumbar vertebra, × ⅔. az , anterior zygapophysis; az 1 , az 2 , az 3 , additional anterior articular surfaces; cc , attachment point of the rib; m , metapophysis; pz , posterior zygapophysis; pz 1 , pz 2 , pz 3 , additional posterior articular surfaces; t , transverse process; tc , attachment point of the rib. (From Flower's Osteology .)
The secondary articulated animals (Xenarthra), occasionally also out as tooth arms (Edentata), form a superordinate order of the higher mammals . It comprises two orders: the tooth arms (pilosa), consisting of anteaters and sloths , and the armored collateral animals (cingulata), which are now only represented by the armadillos . It is named for its additional vertebral processes on the spine. Previously listed as an order themselves, they are now considered to be one of the four main groups of higher mammals and have therefore been upgraded to a higher order. In contrast to the three other groups, their close relationship is traditionally undisputed and morphologically substantiated.
features
Due to their specialization in different habitats and ways of life, the three groups of secondary articulated animals differ significantly in their appearance. The length of the recent species varies from 12.5 centimeters in the girdle mole to 120 centimeters in the giant anteater . The weight fluctuates accordingly between 85 grams and 40 kilograms - the extinct giant sloths were, however, significantly larger.
Convergences of the specialized ant-eaters
Compared with the other superorders there are some interesting cases of convergent evolution: for example, have to Ursäugern associated echidna (Tachyglossidae) and the Laurasiatheria associated pangolins (Pholidota) as the Xenarthra animals attributed anteaters (Vermilingua) as an adaptation to the consumption lost their teeth from insects and worms and developed an elongated tongue.
distribution
The Xenarthra come today, from the well to the south of North America to place nine-banded armadillo ( Dasypus novemcinctus apart), exclusively in the tropics of Central and South America before, although they were able to find in prehistoric times in Africa, North America and Europe. In the geological age of the Eocene , they were also common in Antarctica .
Evolution and systematics
Tribal history
The origin of the secondary articulated animals is assumed today mainly on the basis of serological and molecular biological studies in the Cretaceous period about 90 to 100 million years ago. The fossil record for the three taxa living today, on the other hand, does not assume until the late Paleocene (about 55 million years ago) for the armadillos, in the Middle Eocene (about 45 million years ago) for the sloth and in the early Miocene (about 20 million years ago) for the anteater.
Because of the earliest preserved fossil discovery of an anteater in Europe, the Eurotamandua joresi from the Middle Eocene of Messel Pit near Darmstadt is believed the Xenarthra either in Africa or in the area of the fault lines of the later South America and Antarctica formed and the Tethys also Reached Europe. This thesis is controversial, which means that the question of the origin of the European anteater is still largely open. A phylogenetic study based on morphological features of recent and fossil taxa from 1998 placed Eurotamandua joresi at the base of the anteater or, alternatively, at the base of all tooth arms. You need another study instead suggest that E. joresi is identical to the originating also from the Messel Pit and a pangolin identified Fossil eomanis krebsi ; they classify the latter as a juvenile of E. joresi . This is contradicted by the discoverer of both fossils, Gerhard Storch and his colleagues, by pointing out various serious differences in the bones.
If the secondary animals did not already come from South America, they probably immigrated there from Antarctica at the turn of the Cretaceous and Tertiary periods . On the continent there was a relatively large variety of species within this group of animals. Fossils have been recorded for over 200 species, including giant forms such as the giant sloth or the Glyptodontidae . Some researchers believe that the South American ungulates (Meridiungulata), an extinct group of herbivorous animals, may be related to the siblings.
External system
The secondary articulated animals are now considered to be one of the four major taxa within the higher mammals (Eutheria) , especially on the basis of molecular biological studies, alongside the Afrotheria , the Euarchontoglires and the Laurasiatheria .
While the Laurasiatheria and the Euarchontoglires form the common group of the Boreoeutheria with a high degree of probability , the position of the sibling animals and the Afrotheria in relation to the Boreoeutheria has not yet been fully clarified - all three possible variants are being discussed and confirmed in various molecular biological studies.
One variant positions the secondary animals as the most original group at the base of the higher mammals and thus as the sister group of all other taxa, which in this case are summarized as Epitheria . This variant is proposed both molecularly and morphologically, based on the structure of the inner ear.
| Higher mammals (Eutheria) |
|
||||||||||||
|
|
Alternatively, the Afrotheria are suggested as the most original group.
| Higher mammals (Eutheria) |
|
||||||||||||
|
|
A third theory finally summarizes the Afrotheria and the secondary articulated animals as a taxon called Atlantogenata and contrasts this with the Boreoeutheria.
| Higher mammals (Eutheria) |
|
||||||||||||
|
|
Internal system
The monophyly of the secondary joint animals is considered undisputed and is supported by a number of morphological features, including the eponymous additional joints of the spine, pelvic and skull features, and by various molecular biological studies. In contrast to the known fossil species, the number of species of recent sibling animals is very limited. Today, with only 36 species, they represent only 1.2% of the species diversity of higher mammals . They are divided into two orders:
- the tooth arms (pilosa), which comprise the six species of the sloth (Folivora) and the ten species of the anteater (Vermilingua)
-
- Sloths (folivora)
- Three toed sloths (Bradypodidae) with four species of the genus Bradypus
- Two -toed sloths (Megalonychidae) with two species of the genus Choloepus
- Anteaters (Vermilingua)
- Pygmy anteaters ( Cyclopes ) with a total of seven species
- Giant anteater ( Myrmecophaga tridactyla )
- Tamanduas ( Tamandua ) with two species: the Northern Tamandua ( T. mexicana ) and the Southern Tamandua ( T. tetradactyla ).
- the Armored Xenarthra (Cingulata) to which the present-day armadillos (21 species) and the extinct glyptodontidae that pampatheriidae that Peltephilidae and Palaeopeltidae count
-
- Dasypodidae (long-nosed armadillos)
- Long-nosed armadillos ( Dasypus ) with seven species, including the nine-banded armadillo ( D. novemcinctus )
-
- Chlamyphorinae (girdle mole)
- Belt gullet ( Chlamyphorus truncatus )
- Burmeister girdle gullet ( Calyptophractus retusus )
- Euphractinae
- Pygmy armadillo ( Zaedyus pichiy )
- Six-banded armadillo ( Euphractus sexcinctus )
- Bristle armadillos ( Chaetophractus ) with two species
- Tolypeutinae
- Giant armadillo ( Priodontes maximus )
- Ball armadillos ( Tolypeutes ) with two species
- Naked- tailed armadillos ( Cabassous ) with four species
A cladogram of the secondary joint animals living today looks accordingly as follows:
| Sub-articulated animals (Xenarthra) |
|
||||||||||||
|
|
References
literature
- Gerhard Storch : Xenarthra (Edentata), articulated animals, tooth arms . In: W. Westheide and R. Rieger: Special Zoology. Part 2: vertebrates or skulls . Spektrum Akademischer Verlag, Munich 2004, pp. 574-575, ISBN 3-8274-0307-3 .
- Ronald M. Nowak: Walker's Mammals of the World . 2nd Edition. The Johns Hopkins University Press, Baltimore 1999, pp. 147-168, ISBN 0-8018-5789-9 .
Web links
References and comments
- ↑ Timothy J. Gaudin and Daniel G. Branham: The Phylogeny of the Myrmecophagidae (Mammalia, Xenarthra, Vermilingua) and the Relationship of Eurotamandua to the Vermilingua. Journal of Mammalian Evolution 5 (3), 1998; Pp. 237–265 ( doi: 10.1023 / A: 1020512529767 )
- ^ FS Szalay, F. Schrenk: The middle Eocene Eurotamandua and a Darwinian phylogenetic analysis Kaupia 7, 1998; Pp. 97-186
- ↑ Inés Horovitz, Gerhard Storch, Thomas Martin: Ankle structure in Eocene pholidotan mammal Eomanis krebsi and its taxonomic implications. Acta Palaeontologica Polonica 50 (3), 2005; Pp. 545-548
- ↑ William J. Murphy, Eduardo Eizirik, Stephen J. O'Brien, Ole Madsen, Mark Scally, Christopher J. Douady, Emma Teeling, Oliver A. Ryder. Michael J. Stanhope, Wilfried W. de Jong, Mark S. Springer: Resolution of the Early Placental Mammal Radiation Using Bayesian Phylogenetics, in Science 294, 2001; Pp. 2348-2351
- ↑ Gillian C. Gibb, Fabien L. Condamine, Melanie Kuch, Jacob Enk, Nadia Moraes-Barros, Mariella Superina, Hendrik N. Poinar and Frédéric Delsuc: Shotgun Mitogenomics Provides a Reference Phylogenetic Framework and Timescale for Living Xenarthrans. Molecular Biology and Evolution 33 (3), 2015, pp. 621-642