Odd-toed ungulates

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Odd-toed ungulates
African donkey (Equus asinus)

African donkey ( Equus asinus )

Systematics
without rank: Synapsids (Synapsida)
Class : Mammals (mammalia)
Subclass : Higher mammals (Eutheria)
Superordinate : Laurasiatheria
without rank: Scrotifera
Order : Odd-toed ungulates
Scientific name
Perissodactyla
Owen , 1848
The white rhinoceros is the largest living odd ungulate.

The Unpaarhufer or Unpaarzeher (Perissodactyla, formerly also Mesaxonia) are an order of the mammals (Mammalia). In contrast to the ungulates they are characterized by a mostly odd number of toes. The order includes three recent families, the horses (Equidae), rhinoceroses (Rhinocerotidae) and tapirs (Tapiridae) with a total of around 17 species. In the 19th century, the zoologist Richard Owen , who also coined the term odd-toed ungulates , was the first to recognize that these three very different looking families are related to one another .

features

General

As an adaptation to different habitats and ways of life, the odd-toed ungulates have developed clear differences in physique. There are common features in the structure of the limbs and teeth. All living and the vast majority of extinct species are quite large animals. The rhinos, the second largest land-living mammals after the elephants, belong to this group. The extinct Paraceratherium , a hornless, rhino-related animal from the Oligocene , is even considered to be the largest land mammal of all time. Some original representatives of the order, such as the primitive horse Hyracotherium, were quite small with only 20 cm shoulder height. Apart from dwarf breeding of the domestic horse and the house urchin, today's odd ungulates reach a head trunk length of 180 to 420 centimeters and a weight of 150 to 3500 kilograms. While rhinos are only sparsely hairy and have a thick epidermis , tapirs and horses have a thick, short coat of hair. Most species are gray or brown in color, but zebras wear a typical stripe dress, and young tapirs have white vertical stripes.

limbs

Hoof of a domestic horse

The main axis of both the front and rear feet runs through the central ray, the third toe is accordingly the largest in all species. The remaining rays have been reduced to varying degrees, least of all in the tapirs. These animals still have four toes on their front feet, an adaptation to the soft subsoil of their habitat, and three on their back feet. Today's rhinos have three toes on their front and rear feet. The reduction of the lateral rays is most advanced in horses, these animals only have a single toe (monodactyly). The feet are provided with hooves , which, however, only cover the toe almost completely in horses; in rhinos and tapirs only the front edge is covered with a hoof, the underside is soft - rhinos also have a soft sole cushion.

Within the legs, the ulna and fibula are reduced in size, in horses these bones are even fused with the spoke or shin in the lower half . An autapomorphy (a common feature that clearly distinguishes this group from other groups) is the saddle-shaped talonavicular joint - the ankle joint between the ankle bone (talus) and scaphoid bone (navicular bone ) - which severely restricts mobility. The thigh is relatively short, the collarbone is missing.

Skull and teeth

Tapirs, here the lowland tapirs, are the only odd-toed ungulates family to have a trunk .

Unpaired ungulates have an elongated head, which is primarily due to a long upper jaw (maxillary). The different snout shapes of the individual families go back to differences in the construction of the intermaxillary bone (premaxillary). The tear bone (lacrimale) has a cusp protruding into the eye socket ; an autapomorphy is the wide contact between the tearbone and the nasal bone (nasal). Another characteristic feature is a massive pine, especially among the grass-eating species. The temporomandibular joint is high and the mandibular branch is enlarged.

Rhinos have one or two horns, which, unlike the horns of the ungulates , are made of agglutinated keratin rather than bone .

The number and structure of the teeth differ depending on the food. Incisors and canines can be very small or completely absent (for example in the two African rhinoceros; in horses, mostly only males have canines - " hook teeth "). Due to the elongated upper jaw, there is a gap between the front teeth and the molars called a diastema . The premolars (front molars) are mostly developed like molars ; The shape of the surface and the height of the molars (rear molars ) depend heavily on whether soft leaves or hard grass are the main components of the diet. There are three or four premolars and always three molars per half of the jaw, so the tooth formula for the odd-toed ungulate is: I 0–3 / 0–3 · C 0–1 / 0–1 · P 2–4 / 2–4 · M 3 / 3.

Internal anatomy

In the structure of the digestive tract , the odd-toed ungulates differ greatly from the mostly herbivorous even- toed ungulates . Odd ungulates are - similar to rodents - rectal fermenters, which means that digestion mostly takes place in the large intestine . In contrast to that of the ungulates, the stomach is always simple and unicameral; The fermentation takes place in the very large appendix (which holds up to 90 liters in horses) and in the double- looped colon (colon). The intestine is very long (up to 26 meters in horses). The utilization of food is relatively low, which has probably led to the fact that there are no longer any small odd-toed ungulates, as large animals have less food requirements per kilogram of body weight and the surface-volume ratio is smaller (which is better for the heat balance).

In the area of ​​the urogenital tract , the females are originally characterized by a "two-horned uterus " ( uterus bicornis ). The ovaries of rhinos and tapirs lie in a pocket of the peritoneum (ovarian pocket , bursa ovarica ), in horses the ovary pocket only partially covers the ovary. Horses differ in the structure of the ovary from all other mammals: The ovarian tissue with the follicles, usually referred to as “bark”, is located inside the organ in horses, while the vascular medulla is outside. The ovarian cortex only reaches the surface at one point. This point is also visible from the outside as a retraction and is known as the "ovulation pit" ( fossa ovarii ), only at this point ovulation can occur. In male odd-toed ungulates, the testicles of rhinos and tapirs are inguinal (in the groin region ), only horses have a scrotum .

Distribution area

As with the Indian rhinoceros , the range of most species has declined over the past few decades.

The current distribution area of ​​the odd ungulates consists only of a small part of what was once a larger occurrence that spanned almost the entire earth. Wild representatives of this group can be found today in Central and South America , in eastern and southern Africa, and in central, southern and southeastern Asia . During the heyday of the odd ungulates from the Eocene to the Oligocene , the area of ​​distribution extended with great diversity over a large part of the globe with the exception of Australia and Antarctica , they reached the South American continent with horses and tapirs after the formation of the Isthmus of Panama in the Pliocene around 3 years ago Millions of years. In North America they died out around 10,000 years ago in Europe with the disappearance of tarpans in the 19th century. Hunting and restriction of the habitat have meant that today's wild species often only occur in fragmented relic populations. In contrast to this, domestic horses and house donkeys have achieved worldwide distribution as farm animals; feral animals of both species are now also found in regions that were originally not home to odd ungulates, such as Australia.

Lifestyle and diet

Depending on their habitat, the different species of odd ungulates lead a different way of life. They are more crepuscular or nocturnal animals. Tapirs live solitary and predominantly inhabit tropical rainforests and other forests. Rhinos also tend to live as solitary animals and are more likely to be found in dry savannahs in Africa and in humid swamp or forest areas in Asia. Finally, horses inhabit open areas such as grasslands, steppes or semi-deserts and live together in groups. Unpaired ungulates are exclusively herbivores that feed on grass, leaves and other parts of plants to varying degrees. A distinction is usually made between mainly grass-eating forms (white rhinoceros, equidae) and leaf-eating forms (tapirs, other rhinos).

A young lowland tapir

Reproduction and development

Unpaired ungulates are characterized by a long gestation period and a small litter size, usually a single young is born. The gestation period is between 330 and 500 days, the longest in rhinos. New-born odd-toed ungulates flee the nest , young horses and rhinos can follow the mother after just a few hours; only tapir babies spend their first days of life in a sheltered camp.

The young are suckled for a relatively long time, often into the second year of life and reach sexual maturity at around two to eight years of age. They are rather long-lived animals; several species have been shown to be almost 50 years old in human care.

Systematics

External system

Internal systematics of Laurasiatheria and phylogenetic position of the odd ungulate according to Maureen A. O'Leary et al. 2013
  Laurasiatheria  

 Eulipotyphla (insect eater)


  Scrotifera  
  Ferae  

 Pholidota (pangolins)


   

 Carnivora (predators, including Pinnipedia (seals))



   

 Chiroptera (bats)


  Euungulata  

 Perissodactyla (odd-toed ungulate)


   

 Cetartiodactyla  (artifacts and whales)






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Traditionally, the odd ungulates were grouped together with other hoofed mammals such as the even- toed ungulate , snails , proboscis and others as " ungulates " (ungulata). A close relationship to the sleepers in particular was suspected and based on similarities in the structure of the ear, the course of the carotid artery and the toes.

Due to molecular genetic investigations, however, considerable doubts about the relationship of the ungulates have recently become clear, presumably these represent a polyphyletic group, which means that the similarities are based only on convergent evolution and not on a common descent. Today, elephants and hyrax are mostly classified under the Afrotheria , so they are not closely related to the odd-toed ungulates. These in turn are listed in the Laurasiatheria , a superordinate order that originated in the Laurasia continent . The molecular genetic findings indicate that the sister taxon of the odd- toed ungulates form the cetartiodactyla , which contains the ungulates (Artiodactyla) and whales (Cetacea); both groups together form the Euungulata . Farther out are the bats (Chiroptera) and the Ferae (a common taxon made up of predators (Carnivora) and pangolins (Pholidota)). In an alternative scenario there is also a closer connection between the odd-toed ungulates, the predators and the bats, this common group then being called pegasoferae .

Internal systematics of the Euungulata according to Welker et al. 2015
  Euungulata  

 Cetartiodactyla  (artifacts and whales)


  Panperissodactyla  

 Perissodactyla  (odd-toed ungulate)


   

 " Meridiungulata " (South American ungulates †;
  especially Notoungulata and Litopterna )




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According to studies that were published in March 2015, the odd ungulates are closely related to at least some of the so-called Meridiungulata ("South American ungulates"), a very diverse group of crouching mammals occurring in South America from the Paleocene to the Pleistocene , whose systematic uniformity is largely unclear. Due to their palaeogeographical distribution, these were partly associated with the Afrotheria , which was also supported by some anatomical features such as the structure of the spine or the ankle bone . However, with the help of protein sequencing and a comparison with fossil collagen , obtained from the remains of some phylogenetically young representatives of the “Meridiungulata” (especially Macrauchenia from the group of Litopterna and Toxodon from the group of Notoungulata ), a close relationship to the odd-toed ungulates could be worked out. Both kinship groups, the odd-toed ungulates and the Litopterna-Notoungulata, are now combined in the parent taxon of Panperissodactyla . This kinship group is within the Euungulata opposite the pair of ungulates and whales (Cetartiodactyla). Two years later the result could be confirmed with the help of molecular genetic studies at least for the Litopterna line. The separation of these from the line that led to the unpaired ungulates took place around 66.15 million years ago, which roughly corresponds to the Cretaceous-Tertiary boundary . As a starting point for the development of the two groups, the " condylarthra " can probably be considered, which represent a heterogeneous group of primeval ungulates that mainly inhabited the northern hemisphere in the Paleogene . Studies from 2020 suggest, on an anatomical basis, at least for the Litopterna, a sister group relationship to the odd-toed ungulates.

Internal system

Recent representatives

Internal system of recent odd ungulates according to Tougard et al. 2001, Steiner and Ryder 2012 and Cozzuol et al. 2013
  Perissodactyla  
  Equidae  

 Equus ferus


   

 Equus asinus


   


 Equus kiang


   

 Equus hemionus



   

 Equus zebra


   

 Equus quagga


   

 Equus grevyi







   
  Tapiridae  

 Tapirus indicus


   

 Tapirus bairdii


   

 Tapirus kabomani


   

 Tapirus pinchaque


   

 Tapirus terrestris






  Rhinocerotidae  



 Rhinoceros unicornis


   

 Rhinoceros sondaicus



   

 Dicerorhinus sumatrensis



   

 Ceratotherium simum


   

 Diceros bicornis






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One differentiates in the order of the odd ungulate (Perissodactyla) three recent families with around 17 species - within the horses the exact number of species is still controversial. Rhinos and tapirs are more closely related and stand opposite the horses. According to molecular genetic analyzes, the horses were separated from the other odd-toed ungulates in the Paleocene around 56 million years ago, while the rhinos and tapirs split up in the Lower Middle Eocene around 47 million years ago.

  • Order: Unpaarhufer (Perissodactyla Owen , 1848)

The house horse was domesticated from the wild horse and the house donkey from the African donkey . In some classifications, the khur ( Equus khur ) and the Achdari ( Equus hemippus ) as well as the Hartmann mountain zebra ( Equus hartmannae ) and the northern white rhinoceros ( Ceratotherium cottoni ) are separate species.

Fossil representative

Live reconstruction of the Chalicotheriids Anisodon grande
(formerly Chalicotherium grande )

Fossil odd ungulates occurred in large numbers with a wide variety of forms, the following groups are among the most important lines of development:

  • The Brontotherioidea belonged to the earliest known large mammals, consisting of the families of the Brontotheriidae (synonym Titanotheriidae), the best known representative of which is Megacerops , and the more basal group of Lambdotheriidae . Especially in their later phase they were characterized by a bony horn at the transition from the nasal bone to the frontal bone and generally by flat molars suitable for soft plant food. At the beginning of the Upper Eocene , the Brontotheroidea, which were almost exclusively restricted to North America and Asia, died out.
  • The Equoidea (equine species) also developed in the Eocene. The Palaeotheriidae , which are mainly known from Europe and whose most famous representative was Hyracotherium , became extinct in the Oligocene. The (actual) horses (Equidae), however, flourished and spread. In the development of this group, the reduction in the number of toes, the lengthening of the limbs and the progressive adaptation of the teeth to hard grass forage can be clearly observed on the basis of fossil finds.
  • The Chalicotherioidea represented another characteristic group consisting of the families of the Chalicotheriidae and the Lophiodontidae . Within the Chalicotheriidae there was the development of claws instead of hooves and a drastic elongation of the front legs. The best-known genera include Chalicotherium and Moropus . The Chalicotherioidea did not become extinct until the Pleistocene .
  • The Rhinocerotoidea (rhinoceros relatives) came from the Eocene to the Oligocene with a great variety of forms, there were dog-sized leaf-eaters, semi-aquatic animals (some living in water) and also huge, long-necked animals - only few of them had horns on their noses. The actual rhinoceros (Rhinocerotidae) originated in the Middle Eocene, five species survive to this day. In addition, several fossil families are documented that were largely present in the Eocene and Oligocene . In a more classical perspective, a distinction is made between the Amynodontidae , hippopotamus-like animals that live in water, and the rather long-legged Hyracodontidae . The latter developed extremely large, long-necked forms such as Paraceratherium (formerly also known as Baluchitherium or Indricotherium ), the largest known land mammal. However, since the Hyracodontidae turned out to be a "garbage can taxon", there have been various attempts at a new classification in recent times. The Indricotheriidae (also Paraceratheriidae) and the Eggysodontidae are partially separated from the Hyracodontidae. As a result, the now actual Hyracodontidae are more basal within the Rhinocerotoidea.
  • The Tapiroidea (tapir-like) reached their greatest diversity in the Eocene, when several genera were native to Eurasia and North America. Most likely they retained a primeval physique, the only remarkable thing is the development of a trunk . The extinct families include the Helaletidae , which appeared quite rich in forms in North America and Eurasia, well-known genera here are Helaletes , Heptodon , Colodon or Desmatotherium . In addition to this basal group, the Deperetellidae were rather restricted to Eurasia. They include forms such as Deperetella , Teleolophus, and Irenolophus .

Higher classification of the unpaired ungulates

Internal systematics of the perissodactyla according to Holbrook and Lapergola 2011
  Perissodactyla  
  Tapiromorpha  

 Isectolophidae (†)


   
  Ancylopoda  

 Lophiodontidae (†)


   

 Chalicotheriidae (†)



  Ceratomorpha  
  Tapiroidea  

 Helaletidae (†)


   

 Tapiridae



  Rhinocerotoidea  

 Amynodontidae (†)


   

 Hyracodontidae (†)


   

 Rhinocerotidae







  Hippomorpha  
  Equoidea  

 Palaeotheriidae (†)


   

 Equidae



  Brontotherioidea  

 Lambdotheriidae (†)


   

 Brontotheriidae (†)





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Internal systematics of the perissodactyla according to Hooker and Dashzeveg 2004
  Perissodactyla  
  Titanotheriomorpha  

 Brontotheriidae (†)


  Lophodontomorpha  
  Ancylopoda  

 Isectolophidae (†)


  Chalicotherioidea  

 Lophiodontidae (†)


   

 Chalicotheriidae (†)




  Euperissodactyla  
  Ceratomorpha  

 Tapiroidea 


   

 Rhinocerotoidea 



  Hippomorpha  

 Palaeotheriidae (†)


   

 Equidae






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The relationships between the large groups of odd ungulates have not yet been fully clarified. Initially after Richard Owen established the term perissodactyla in 1848, today's representatives were classified as equal. In the first half of the 20th century, with the inclusion of fossil forms, a stronger systematic differentiation of the unpaired ungulates began, whereby these were divided into the two major suborders of the Hippomorpha and the Ceratomorpha . According to the current view, the Hippomorpha include today's horses and their fossil representatives (Equoidea), while the Ceratomorpha include the tapirs and rhinos plus their extinct, extended relatives (Tapiroidea and Rhinocerotoidea). The names Hippomorpha and Ceratomorpha were introduced by Horace Elmer Wood in 1937 , in response to criticism that had arisen after his three years earlier proposed name Solnungula for the kin group of horses and Tridactyla for the rhinoceros-tapir complex. The extinct Brontotheriidae were also placed among the Hippomorpha by Wood and were therefore closely related to the horses. Some researchers consider this assignment to be justified on the basis of similar tooth features, but there is also the view of a very basal position within the odd ungulates, whereby they then belong to the group of Titanotheriomorpha.

Originally, Wood also saw the Chalicotheriidae as members of the Hippomorpha, but in 1941 William Berryman Scott compared them as claw-bearing odd-toed ungulates and referred them to the new suborder Ancylopoda (whereby he identified Ceratomorpha and Hippomorpha as being odd-toed ungulates in the group of Chelopoda united). The term Ancylopoda had already been established in 1889 by Edward Drinker Cope for the Chalicotherien. Further morphological investigations from the 1960s, however, showed an intermediate position of the Ancylopoda between the Hippomorpha and Ceratomorpha. Leonard Burton Radinsky saw all three large groups of odd ungulates as equal, which he justified, among other things, with the extremely long and independent phylogenetic development of the three lines. In the 1980s, Jeremy J. Hooker recognized a general similarity between the Ancylopoda and the Ceratomorpha in dental construction, especially in the earliest representatives, which in 1984 led to the union of the two suborders in the intermediate order Tapiromorpha (at the same time he expanded the Ancylopoda to include the Lophiodontidae). The name Tapiromorpha in turn goes back to Ernst Haeckel , who coined it in 1873; For a long time, however, it was considered synonymous with Ceratomorpha, since Wood ignored it in 1937 when establishing the Ceratomorpha due to its vastly different use in the past. Also in 1984, Robert M. Schoch used the conceptually similar term Moropomorpha, which is now synonymous with Tapiromorpha. Within the Tapiromorpha, the Isectolophidae , which are now extinct, are compared to the Ancylopoda-Ceratomorpha group as a sister group and are therefore to be regarded as the most original representatives of this kinship complex.

In addition to the large groups of odd ungulates, which are widely recognized here, there are also other higher taxa which, depending on the systematic classifications used, are important, but are usually only rarely used. Jerry J. Hooker and Demberelyin Dashzeveg introduced the Lophodontomorpha in 2004, which includes all odd ungulate groups with the exception of the Brontotheria and their immediate relatives. The Euperissodactyla, which in turn unite the Ceratomorpha and the Hippomorpha, go back to both authors. On the other hand, Malcolm C. McKenna and Susan K. Bell propagated the Selenida in their survey work on the structure of mammals in 1997, in which they included the Brontotherien and Chalicotherien together with their relationship.

Development history

Origins

The history of the development of the odd-toed ungulate is relatively well handed down through fossils ; numerous finds reveal the radiation of this group, which used to be much richer in shape and more widespread. The origins of the unpaired ungulates are unclear, in some cases an origin is assumed in North America, which would be associated with the rapid development of the Phenacodontidae . On the other hand, Asia could also be seen as the actual center of evolution. Radinskya from the end of the Paleocene of East Asia is considered to be one of the oldest close relatives of the odd ungulate . The skull, measuring just over 8 cm, belongs to a very small and original animal, which, with the slightly π-shaped design of the enamel on the rear molars, shows similarities to unpaired ungulates, especially the rhinos and their relatives. Other features such as the formation of the tooth tubercles could also speak for a closer relationship with the Tethytheria , which include the proboscis . Finds from western India support the view of an Asian origin and limit the center of origin to South Asia . Remains of Cambaytherium and Kalitherium , which make up the family of the Cambaytheriidae , come from the Cambay Shale Formation , which dates to the Lower Eocene around 54.5 million years ago . Their teeth show similarities to the early odd-toed ungulates and Tethytheria , comparable to Radinskya . Above all, there is also extensive body skeleton material from Cambaytherium . Among other things, the saddle-shaped indentation of the navicular joint at the lower end of the ankle bone and the mesaxonic design of the front and rear feet - the main axis of the foot went through the central ray (ray III) - speak for a close relationship with the odd-toed ungulate. However, since the feet, unlike the earliest unpaired ungulates, were still five-pointed, the Cambaytheria are now regarded as their sister group. It is possible that the ancestors of the odd-toed ungulates crossed an island bridge from the Afro-Arab land mass to the Indian subcontinent , which was an island at the time and drifted north towards Asia. From the same formation, Vastanolophus, one of the most primeval known representatives of the odd ungulate, was described, which, however, has only had two teeth so far.

Tribal history

Hyracotherium , an early relative of the horses, is one of the oldest known odd ungulates

The odd ungulates appear relatively suddenly at the beginning of the Lower Eocene , around 56 million years ago, in both North America and Asia . The oldest North American finds come from Sifrhippus , a representative of the horses from the Willwood Formation in northwestern Wyoming. At around the same time, a relative of the horses from the Lingcha formation in northwestern China is also known to be Erihippus . In addition, with Orientolophus, a representative of the root group of the rhinoceros-tapir line, with Protomoropus an early form of the Ancylopoda and with Danjiangia a first member of the Brontotheriidae . Only a little later, other distant ancestors of the tapirs and rhinos appear in Asia, such as Ganderalophus or Meridiolophus , as well as Litolophus , which is in the evolutionary line of the Chalicotheriidae . In North America, Eotitanops from the group of Brontotheriidae is documented. Thus, in the course of the Lower Eocene, the most important large groups can be identified by primitive representatives. In the beginning, the members of the different lineages looked very similar with an arched back and generally four toes on the front and three on the hind feet. Hyracotherium , which is considered to be a representative of the horse relatives, looked very similar to Hyrachyus , the first representative of the line that led to today's rhinos and tapirs . All were relatively small compared to later forms and lived as fruit and foliage eaters in forests. The first giant forms emerged with the Brontotherien in the Middle and Upper Eocene, whereby the well-known Megacerops from North America reached up to 2.5 m shoulder height and could have weighed a good 3 t. The decline of the Brontotherien at the end of the Eocene is related to the emergence of more competitive herbivores.

Especially at the end of the Eocene, other successful lines of the odd ungulate emerged, such as the Chalicotheriidae and the rhinos and their close relatives, whose development also began with very small forms. The Hyracodontidae , the closest fossil relatives of the rhinos, provided Paraceratherium, the largest land-living mammal of all time. This weighed up to 20 t and lived in Eurasia in the Oligocene . Other flourishing groups at that time were the Amynodontidae with Amynodon , Cadurcodon or Sellamynodon , as well as the Eggysodontidae . With the beginning of the Miocene , the odd ungulates reached Africa for the first time about 20 million years ago, which was now connected to Eurasia with the closure of the Tethys . However, the subsequent exchange of fauna brought new groups of animals to the old settlement areas of the odd-toed ungulate, such as the proboscis , whose competition also led to the extinction of some odd-to-ungulate lines. The rise of ruminants , which occupy similar ecological niches and whose digestive system is considered to be more efficient, is also associated with the decline in the diversity of the odd ungulate. However, climatic changes in the course of the Miocene towards cooler and drier climates, which accompanied the spread of open landscapes, played a major role in the decline of the odd ungulate. However, some lines, such as those of the horses and rhinos, also flourished, with numerous representatives adapting to the harder grass diet through anatomical modifications. This created open land forms that colonized the newly created landscape types. With the formation of the Isthmus of Panama in the Pliocene and the subsequent Great American Fauna Exchange , the odd ungulates, here the horses and tapirs, reached one of the last habitats accessible to them around 3 million years ago in South America. However, the odd ungulates were also affected by the extinction of large mammals at the end of the Pleistocene , for example the horses of North and South America and the woolly rhinoceros disappeared at this time . Whether human hunting ( overkill hypothesis ), climatic changes that accompanied the end of the Ice Age , or a combination of both factors was responsible for this extinction is controversial.

Research history

Richard Owen , 1856

The knowledge that the odd ungulate form a systematic unit goes back to the middle of the 19th century. Before that, today's representatives of the odd ungulates were mostly assigned to other groups. Linnaeus (1707-1778) introduced in 1758 in his seminal work Systema Naturae , the horse ( Equus ) to the side of the hippopotamus ( Hippopotamus ). At that time these also contained the tapirs ( tapirus ), more precisely the lowland tapir , which at that time was the only known tapir species in Europe and classified the Linnaeus as Hippopotamus terrestris . Linnaeus referred both genera to the Belluae group. The rhinoceros ( Rhinoceros ) he united against it with the Glires , a group today consisting of the rabbit-like and the rodents . It was not until Mathurin-Jacques Brisson (1723–1806) separated the tapirs from the hippos in 1762 with the introduction of the term le tapir . He also separated the rhinos from the rodents, but did not unite the three current families of odd ungulates. In the transition to the 19th century, the individual Unpaarhufer genera were so with various other groups the trunk animals or today Paarhufern associated, in that time, the establishment of falls of the term "pachyderm" (Pachydermata), the Étienne Geoffroy Saint-Hilaire (1772- 1844) and Georges Cuvier (1769-1832) in 1795 as Pachydermes (and which, in addition to rhinos and elephants, also included hippos, pigs , peccaries , tapirs and hyrax ). However, the horses were largely considered to be a separate group from the other mammals and were often led under the designation Solleidula or Solipèdes , which both means "equine".

In 1816 it was Henri Marie Ducrotay de Blainville (1777-1850) who divided the ungulates according to the structure of the feet, thus distinguishing animals with an even number of toes from those with an odd number of toes. He pushed the horses as solleidulate close to the tapirs and rhinos as multungulate animals and referred to all of them as onguligrades à doigts impairs , which came very close to the concept of the odd ungulate as a systematic unit. Richard Owen (1804-1892) referred to Blainville in his study of fossil mammals of the Isle of Wight and introduced the name Perissodactyla. Like Blainville, however, he included the hyrax in addition to horses, rhinos and tapirs. In the following years, Owen referred to the odd-toed ungulates, such as Coryphodon , Toxodon or Nesodon , which today all belong to other mammalian orders.

Othniel Charles Marsh (1831-1899) introduced the term Mesaxonia in 1884. He used this for today's members of the odd ungulate, including their extinct relatives, but expressly excluded hyraxes. Mesaxonia is now considered a synonym for Perissodactyla. Sometimes it was used as a subordinate term for the actual odd-toed ungulates (rhinos, horses, tapirs), while perissodactyla stood as a term for the entire order including the hyrax. The assumption that the hyrax are part of the odd ungulates persisted well into the 20th century. It was only with the advent of molecular genetic testing methods that it was recognized that the hyrax are not closely related to the odd-toed ungulates, but are related to the proboscis and manatees .

Odd-toed ungulates and humans

The quagga became extinct at the end of the 19th century.

The house horse and donkey play an important role in human history, especially as riding, work and pack animals, the domestication of both species began several millennia before the birth of Christ. Due to the motorization of agriculture and the spread of automobile traffic, this purpose has declined sharply in the western industrialized countries, riding is mostly only practiced as a hobby or sport. In the less developed regions of the world, the use of these animals is still widespread. To a lesser extent, horses and donkeys are also kept for their meat and milk.

In contrast to this, the populations of almost all other species of the odd ungulate have declined drastically due to hunting and the destruction of their habitat. The quagga is extinct, the Przewalski horse is considered to be extinct in the wild.

Current risk levels according to IUCN (as of 2012):

literature

  • Martin S. Fischer: Mesaxonia (Perissodactyla), unpaired ungulates . In: Wilfried Westheide, Reinhard Rieger (Ed.): Special Zoology. Part 2: vertebrates or skulls . Spektrum Akademischer Verlag, Heidelberg and Berlin 2004, pp. 646–655, ISBN 3-8274-0307-3 .
  • Ronald M. Nowak: Walker's Mammals of the World . 6th edition. Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9 (English).
  • Thomas S. Kemp: The Origin & Evolution of Mammals. Oxford University Press, Oxford 2005. ISBN 0-19-850761-5 .
  • AH Müller: Textbook of Palaeozoology , Volume III: Vertebrates, Part 3: Mammalia. 2nd Edition. Gustav Fischer Verlag, Jena and Stuttgart 1989. ISBN 3-334-00223-3 .
  • Don E. Wilson, DeeAnn M. Reeder (Eds.): Mammal Species of the World . 3rd edition. The Johns Hopkins University Press, Baltimore 2005, ISBN 0-8018-8221-4 .

Individual evidence

  1. ↑ a b Maureen A. O'Leary, Jonathan I. Bloch, John J. Flynn, Timothy J. Gaudin, Andres Giallombardo, Norberto P. Giannini, Suzann L. Goldberg, Brian P. Kraatz, Zhe-Xi Luo, Jin Meng , Xijun Ni, Michael J. Novacek, Fernando A. Perini, Zachary S. Randall, Guillermo W. Rougier, Eric J. Sargis, Mary T. Silcox, Nancy B. Simmons, Michelle Spaulding, Paúl M. Velazco, Marcelo Weksler, John R. Wible and Andrea L. Cirranello: The Placental Mammal Ancestor and the Post-K-Pg Radiation of Placentals. Science 339 (6120), 2013, pp. 662-667, doi: 10.1126 / science.1229237
  2. ↑ D. Tab Rasmussen, Mario Gagnon and Elwyn L. Simons: Taxeopody in the carpus and tarsus of Oligocene Pliohyracidae (Mammalia: Hyracoidea) and the phyletic position of Hyraxes. PNAS 87, 1990, pp. 4688-4691
  3. ↑ a b c d e Robert M. Schoch: A brief historical review of Perissodactyl classification. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of perissodactyls. New York and London 1989, pp. 13-23
  4. ↑ Martin S. Fischer: Hyracoids, the sister group of perissodactyls. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of perissodactyls. New York and London 1989, pp. 37-56
  5. ^ A b Dan Graur, Manolo Gouy and Laurent Duret: Evolutionary Affinities of the Order Perissodactyla and the Phylogenetic Status of the Superordinal Taxa Ungulata and Altungulata. Molecular Phylogenetics and Evolution 7 (2), 1997, pp. 195-200
  6. ↑ Jingyang Hu, Yaping Zhang and Li Yu: Summary of Laurasiatheria (Mammalia) Phylogeny. Zoological Research 33 (E5−6), 2012, pp. E65 − E74
  7. ↑ Hidenori Nishihara, Masami Hasegawa and Norihiro Okada: Pegasoferae, an unexpected mammalian clade revealed by tracking ancient retroposon insertions. PNAS 103, 2006; P. 9929–9934 ( full text, PDF available )
  8. Jump up ↑ a b Frido Welker, Matthew J. Collins, Jessica A. Thomas, Marc Wadsley, Selina Brace, Enrico Cappellini, Samuel T. Turvey, Marcelo Reguero, Javier N. Gelfo, Alejandro Kramarz, Joachim Burger, Jane Thomas-Oates, David A. Ashford, Peter D. Ashton, Keri Rowsell, Duncan M. Porter, Benedikt Kessler, Roman Fischer, Carsten Baessmann, Stephanie Kaspar, Jesper V. Olsen, Patrick Kiley, James A. Elliott, Christian D. Kelstrup, Victoria Mullin, Michael Hofreiter, Eske Willerslev, Jean-Jacques Hublin, Ludovic Orlando, Ian Barnes and Ross DE MacPhee: Ancient proteins resolve the evolutionary history of Darwin's South American ungulates. Nature 522, 2015, pp. 81-84, doi: 10.1038 / nature14249
  9. ^ Richard A. Fariña, Sergio F. Vizcaíno and Gerardo De Iuliis: Megafauna. Giant beasts of Pleistocene South America. Indiana University Press, 2013, pp. 1-436 (pp. 86-87) ISBN 978-0-253-00230-3
  10. ↑ Federico L. Agnolin and Nicolás R. Chimento: Afrotherian affinities for endemic South American “ungulates”. Mammalian Biology 76, 2011, pp. 101-108
  11. ↑ Michael Buckley: Ancient collagen reveals evolutionary history of the endemic South American 'ungulates'. Proceedings of the Royal Society B 282, 2015, S. 20142671, doi: 10.1098 / rspb.2014.2671
  12. ↑ Michael Westbury, Sina Baleka, Axel Barlow, Stefanie Hartmann, Johanna LA Paijmans, Alejandro Kramarz, Analıá M. Forasiepi, Mariano Bond, Javier N. Gelfo, Marcelo A. Reguero, Patricio López-Mendoza, Matias Taglioretti, Fernando Scaglia, Andrés Rinderknecht, Washington Jones, Francisco Mena, Guillaume Billet, Christian de Muizon, José Luis Aguilar, Ross DE MacPhee and Michael Hofreiter: A mitogenomic time-tree for Darwin's enigmatic South American mammal Macrauchenia patachonica. Nature Communications 8, 2017, p. 15951, doi: 10.1038 / ncomms15951
  13. ↑ Ross MacPhee, Frido Welker, Jessica Thomas, Selina Brace, Enrico Cappellini, Samuel Turvey, Ian Barnes, Marcelo Reguero, Javier Gelfo and Alejandro Kramarz: Ancient protein sequencing resolves litoptern and notoungulate superordinal affinities. In: Esperanza Cerdeño (Ed.): 4th International Palaeontological Congress. The History of Life: A view from the Southern Hemisphere. September 28 - October 3, 2014 Mendoza, Argentina. Mendoza, 2014, p. 186
  14. ↑ Nicolás R. Chimento and Federico L. Agnolin: Phylogenetic tree of Litopterna and perissodactyla indicates a complex early history of hoofed mammals. Scientific Reports 10, 2020, p. 13280, doi: 10.1038 / s41598-020-70287-5
  15. ↑ a b Christelle Tougard, Thomas Delefosse, Catherine Hänni and Claudine Montgelard: Phylogenetic Relationships of the Five Extant Rhinoceros Species (Rhinocerotidae, Perissodactyla) Based on Mitochondrial Cytochrome b and 12S rRNA Genes. Molecular Phylogenetics and Evolution 19, 2001, pp. 34-44
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  28. ↑ a b Horace Elmer Wood: Perissodactyl suborders. Journal of Mammalogy 18 (1), 1937, p. 106
  29. ^ William Berryman Scott: Part V: Perissodactyla. In: William Berryman Scott and Glenn Lowell Jepsen (Eds.): The Mammalian Fauna of the White River Oligocene. Transactions of the American Philosophical Society New Series 28 (5), 1941, pp. 747-964 (p. 747)
  30. ↑ Leonard B. Radinsky: Paleomoropus, a new early Eocene chalicothere (Mammalia, Perissodactyla), and a revision of Eocene chalicotheres. American Museum Nouitates 2179, 1964, pp. 1-28
  31. ↑ JJ Hooker: A primitive ceratomorph (Perissodactyla, Mammalia) from the early Tertiary of Europe. Zoological Journal of the Linnean Society of London 82, 1984, pp. 229-244
  32. ^ Robert Milton Schoch: Two unusual specimens of Helaletes in the Yale Peabody Museum collections, and some comments on the ancestry of the Tapiridae (Perissodactyla, Mammalia). Postilla, Peabody Museum, Yale University 193, 1984, pp. 1-20
  33. ^ Luke T. Holbrook: Comparative osteology of early Tertiary tapiromorphs (Mammalia, Perissodactyla). Zoological Journal of the Linnean Society 132, 2001, pp. 1-54
  34. ↑ Malcolm C. McKenna and Susan K. Bell: Classification of mammals above the species level. Columbia University Press, New York, 1997, pp. 1-631 (pp. 469-490)
  35. ^ Leonard B. Radinsky: The Adaptive Radiation of the Phenacodontid Condylarths and the Origin of the Perissodactyla. Evolution 20 (3), 1966, pp. 408-417
  36. ↑ Malcolm C. McKenna, Chow Minchen, Ting Suyin and Luo Zhexi: Radinskya yupingae, a Perissodactyl-like mammal from the Late Palaeocene of China. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of perissodactyls. New York and London 1989, pp. 24-36
  37. ↑ K. Christopher Beard: East of Eden: Asia as an important center of taxonomic origination in mammalian evolution. Bulletin of the Carnegie Museum of Natural History 34, 1998, pp. 5-39
  38. ↑ Kenneth D. Rose: The beginning of the age of mammals. Johns Hopkins University Press, Baltimore, 2006, pp. 1–431 (pp. 242–244 and pp. 266–267)
  39. ↑ Sunil Bajpai, Vivesh Kapur, Debasis P. Das, BN Tiwari, N. Saravanan and Ritu Sharma: Early Eocene land mammals from Vastan Lignite Mine, District Surat (Gujarat), western India. Journal of the Palaeontological Society of India 50 (1), 2005, pp. 101-113
  40. ↑ Sunil Bajpai, Vivesh Kapur, JGM Thewissen, Debasis P. Das and BN Tiwari: New Early Eocene cambaythere (Perissodactyla, Mammalia) from the Vastan Lignite Mine (Gujarat, India) and an evaluation of cambaythere relationships. Journal of the Palaeontological Society of India 51 (1), 2006, pp. 101-110
  41. ↑ Kenneth D. Rose, Thierry Smith, Rajendra S. Rana, Ashok Sahni, H. Singh, Pieter Missiaen and A. Folie: Early Eocene (Ypresian) continental vertebrate assemblage from India, with description of a new anthracobunid (Mammalia, Tethytheria) . Journal of Vertebrate Paleontology 26 (1), 2006, pp. 219-225
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  46. ↑ David J. Froehlich: Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla). Zoological Journal of the Linnean Society, 134, 2002, pp. 141-256
  47. ↑ Bin Bai, Yuan-Qing Wang and Jin Meng: The divergence and dispersal of early perissodactyls as evidenced by early Eocene equids from Asia. Communications Biology 1, 2018, p. 115, doi: 10.1038 / s42003-018-0116-5
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  67. ↑ Data according to IUCN Red List of Threatened Species , Version 2012.2, accessed on February 23, 2013

Web links

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This version was added to the list of articles worth reading on October 31, 2007 .