Brontotheriidae

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Brontotheriidae
Skeletal reconstruction of Megacerops

Skeletal reconstruction of Megacerops

Temporal occurrence
Eocene
53.4 to 33.9 million years
Locations
Systematics
Mammals (mammalia)
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Hippomorpha
Brontotheriidae
Scientific name
Brontotheriidae
Marsh , 1873

The Brontotheriidae ( synonym Titanotheriidae ), sometimes also called thunder-hoofed animals in German (derived from the scientific name from the Greek words βροντή ( brontḗ ) for "thunder" and θηρίον ( theríon ) for "animal"), are an extinct family of rhinoceros-like ungulates from the chronostratigraphic series of the Eocene . The majority of the fossils were found in North America and Asia , a few also in Eastern Europe . A characteristic feature was a massive build. In the larger and often better known genera of the group, there was a paired or battering ram-like horn on the snout above the eye socket , which, in contrast to that of the rhinos, consisted of bone substance; however, the trait does not occur in all members of the family. Brontotherien lived in dense forests and were all herbivores with extensive specialization in leaf nutrition. Little is known about their social behavior. Their tribal history lasted almost 20 million years and most likely began in North America around 53 million years ago with quite small, tapir-sized representatives. At the end of the Eocene there were climatic changes with comparatively cooler conditions and associated with more open landscapes, which was possibly the reason for their extinction. In the biological systematics , the Brontotherien are often placed in the vicinity of the horses due to the structure of their teeth , but in general the relationships between the large extinct groups of odd ungulates have not yet been fully clarified.

features

Habitus

Live reconstruction of nude titanium

Brontotheria were mostly large to very large animals, the largest representatives such as Megacerops could reach a shoulder height of 2.0 to 2.5 m and possibly weighed 2 to 3 t. This makes them roughly comparable to today's white rhinoceros . However, some of the early forms, such as Eotitanops and Palaeosyops , remained significantly smaller and only about tapir-sized with heights of 1 m or less . The skull was mostly robust and quite large in comparison to the body, in later forms it had characteristic bony horn formations. The rest of the body was generally rhinoceros-like with a strong trunk and a spine with long spinal processes on the anterior thoracic vertebrae. These served as starting points for massive neck muscles, which were strong enough to hold the mostly low-hanging head. The strong and short limbs resembled those of today's rhinos, but the lower extremities were on average shorter. The front feet had four toes and the hind feet three; a striking feature of early odd-toed ungulates , which today is only known from the tapirs. Overall, the Brontotherien were not quite as massive as today's rhinos.

Skull and dentition features

Skull of Megacerops viewed from below, the W-shaped cutting ridges on the molars are clearly visible
Skull of Rhinotitan

The skull was comparatively large in all Brontotheria and in the large representatives was 60 cm to sometimes over 80 cm long. Above all, the evolutionarily advanced forms also had widely spreading and sometimes clearly arched zygomatic arches . In many Brontotherien representatives, the brain skull was quite wide, only early forms had a rather narrow skull. The skull showed prominent parasagittal ridges on the parietal bones as muscle attachment points. The occiput , which was sometimes greatly elongated , was also typical, especially in later, horn-bearing representatives, which usually ran at an acute angle when viewed from the side and often resulted in a low head posture. The horns characteristic of the late Brontotheria sat on the rostrum at the transition from the frontal to the nasal bone . The front part of the nasal bone stood free over the upper and middle jaw bones , similar to the rhinos and horses, but different from the tapirs with their nasal bones set far back. Other characteristics shared by all Brontotheria included a shortened rostrum and a distinctly elongated posterior skull area behind the eyes.

The lower jaw usually had a strong structure and a rather short symphysis . The majority of the Brontotheria showed a complete set of teeth with three incisors , one canine , four premolars and three molars per jaw branch. Only the evolutionarily youngest forms had anterior teeth reduced by one incisor and sometimes a missing anterior premolar. The incisors of many representatives had a small, spherical shape. The generally low-crowned ( brachyodont ) molars were equipped with crescent-shaped ( bunoselenodont ) enamel cusps on the chewing surfaces, which additionally had typical W-shaped edges on the upper teeth and were suitable for grinding harder plant material.

horns

Skull of Embolotherium

In contrast to the horns of the rhinos, the horns of the Brontotheria did not consist of keratin , but were outgrowths of skull bones and therefore remained fossilized. They formed from the back of the nasal bone and were covered by the front areas of the frontal bone . The majority of the horn-bearing Brontotheria usually had two paired horns, which were often located above the orbit , with the width of the nasal bone becoming significantly larger in this area. Also deviating from the rhinos, the horns did not end pointed, but were rounded. At the base they had a round to oval cross-section and partially protruded obliquely outwards, at the ends the horns could also be slightly forked, as in Megacerops . In many cases, however, the horn formations consisted only of larger or smaller bone swellings, which was particularly typical of the older forms, which are historically older. In some Asian Brontotheria the horns were often very close together or were fused together and thus formed a bony ram, which was most clearly shown in Embolotherium . It is mostly assumed that the horns, like those of the giraffes , were covered with skin, but they have no tubules for blood vessels on the surface . However, with Embolotherium it has meanwhile been proven that the entire ram was included in the soft tissue covering of the forehead and that the forehead had such a distinctive face.

Fossil finds

Recovery of Brontotherien fossil remains by employees of the National Museum of Natural History in the northwestern United States , 1931

Finds of Brontotherien are known in large numbers and come from North America and Eurasia . Due to the nature of fossil deposits and different recovery and preparation methods, the quality of the finds fluctuates both spatially and temporally, which means that some representatives are better known than others. A few areas of discovery are to be emphasized, in which fossil remains of the Brontotherien were passed down particularly numerous or of excellent quality. The central-western area of ​​North America, mainly the north-western part of the USA with the High Plains and the Rocky Mountains of South Dakota , Nebraska and Wyoming, turned out to be a true "treasure trove" . To the north, the discovery area extends to Saskatchewan and British Columbia in southwest Canada . The first finds were made in this fossil-rich area. In this context, the Badlands must be mentioned in particular , where innumerable material comes from the Chadron Formation in the catchment area of ​​the White River . This rock formation is to be assigned to the Upper Eocene and mainly contained the remains of Megacerops . After the old synonym name Titanotherium for this genus, which is no longer in use , the layers leading to the found are called Titanotherium beds to this day . Also to be emphasized is the Duchesne River Formation in Utah , which can be classified as somewhat older, with high-quality remains of Duchesneodus , a close relative of Megacerops . The Clarno Formation in Oregon with well-preserved fossil finds of Eubrontotherium is also of outstanding importance . A little further away, numerous finds from California are known, including almost freshly born young Parvicornus . The northernmost finds in North America to date came to light in the Margaret Formation on Ellesmere Island in the Canadian Arctic Archipelago north of the Arctic Circle . They date in the transition from the Lower to the Middle Eocene and are largely placed to Eotitanops and Palaeosyops .

Outside of North America, very good sites can be found in East Asia , with the Gobi Desert being outstanding here . From the various rock formations exposed there, such as the Irdin-Manhan Formation , the Shara-Murun Formation or the Ulan-Gochu Formation of the Middle and Upper Eocene, numerous fossil remains of Gnathotitan and Rhinotitan come , but also from the massive Embolotherium . The history of finds began here largely in the 1920s with expeditions to the American Museum of Natural History , but numerous finds were also discovered in the period afterwards. The outcrops of Balochistan in South Asia , from which some of the oldest remains of Brontotheria in Asia come, are also important. Especially since the 1990s, the importance of Central Asia as an important region for research on this group of odd ungulates has been increasing, for example the extremely well-preserved fossil remains of Aktautitan from Kazakhstan .

Paleobiology

Diet

Skull and head reconstruction from Palaeosyops

The characteristic bunoselenodonte tooth enamel pattern on the chewing surfaces of the molars and the low crown height of these are usually signs that the animals were feeding on a soft vegetable diet ( browsing ). This is confirmed by microscopic analyzes of the tooth surfaces of various Brontotheria genera such as Eotitanops , Telmatherium , Metarhinus , Duchesneodus or Megacerops . The numerous narrow scratches and small cavities that were found suggest a diet that was more specialized in leaf nutrition, in which only occasionally small-grain bottom sediments were taken in. Only in the earliest forms could a higher proportion of fruit have played a role, similar to what was the case with the earliest horses . Mixed vegetable foods made from bark and branches or seeds can largely be excluded. Since today's herbivores predominantly have a different chewing pattern, the researchers assume that Brontotherien were extremely picky about foraging for food. Furthermore, it could be determined that especially later representatives of the Brontotherien from the Upper Eocene had significantly more traces of small scratches on the tooth chewing surfaces, which could either be related to a change in preferred food or to general changes in the landscape. In addition, isotope analyzes on the enamel of the molars showed that the latest Brontotheria such as Megacerops obtained almost 100% of their food from leaves and that they were also quite dependent on water. Above all, the dependence on fluids in turn indicates a digestive system similar to today's odd-toed ungulates, in which a large part of the food in the rectum is broken down (rectal fermenter).

Gender differences

Skull of Megacerops , the different shape of the horns is now considered a sex difference

Within the individual Brontotheria genera, differences in body structure can be identified, which are often viewed as gender dimorphism . In many, especially hornless, representatives there are deviations in the tooth structure, which in some individuals usually includes a larger canine tooth that protrudes far beyond the neighboring teeth and which is less clearly developed in other individuals. In connection with large canines, there are often more robust skulls, which have more massive muscle attachment points for the masticatory muscles, especially on the zygomatic arches, which is then expressed in large swelling of the bones. The combination of more robust skulls and large canines is mostly associated with male animals, where similar characteristics can also be observed, for example, in today's horses . Another probable gender difference is to be noted in the horn size of some horn-bearing Brontotheria, where again animals with larger horns and sometimes more robust nasal bones are considered male, while female animals, on the other hand, have more delicate formations. This is known from forms such as Megacerops , Duchesneodus and Embolotherium . It is noteworthy in this context that some of the latest Brontotherien no longer have any difference between the sexes in the tooth structure, so that the canines are similar in size in all fossils found. Above all, this can be proven with Embolotherium , which had a distinctive bony ram on the skull, but also on the basis of the finds by Duchesneodus , which however had two single horns. Possibly there was a secondary reduction in tooth dimorphism in connection with the development of horn formations. Something similar can be found in today's horn and antler bearers of the artifacts : representatives with head weapons usually do not have enlarged canine teeth, in those like the musk deer or the waterbuck , which do not develop antlers, these are at least greatly elongated in the upper jaw. Similar developments are also known with the rhinos.

Social behavior

Two representatives of Megacerops in a live reconstruction

Little is known about the social behavior of the Brontotherien. A marked sex difference is usually typical for the mating of a male with several females in a close social group or among territorial animals. The canines and horns may have served as a display behavior during the rut . Isolated ribs with healed fractures could also indicate rival fights. Individual horns also have evidence of secondary growth, possibly triggered by impact during fighting. But since bony horns are less tough than those made of keratin , it is more likely that possible fights were mostly carried out in sliding or pushing competitions than by pushing and ramming.

Locomotion

The basic rhinoceros-like structure of the body skeleton indicates a rather clumsy gait due to the proportions of the limbs. However, there are individual deviations that allow further statements about the movement of the Brontotherien. The hind legs in particular had an approximately symmetrical knee joint , so that both joint roles of the thigh bone were similar in size, comparable to those of today's elephants . Rhinos, on the other hand, have strongly asymmetrical knee joints, which formed due to their extreme increase in body mass in the course of their tribal history. They enable a very fast run up to a gallop - a type of movement in which all four feet are in the air at the same time in one phase - in open terrain, which elephants are not capable of. For the very large brontotheria such as Megacerops , due to the similar structure of the knee and the great weight, it is assumed that here too a fast run must have been the maximum speed when moving. The same can be assumed for Embolotherium , which had very massive long bones, which suggest a rather clumsy gait. On the other hand, for example, the rhinotitan, which is historically older, had much slimmer limbs, which possibly also allowed more agile locomotion.

Biological functions

In some forms such as Metarhinus , Sphenocoelus and Telmatherium , the actual internal nasal passages at the base of the skull are closed and replaced by openings shifted further back towards the ploughshare . As a result, the air you breathe is directed through the nose to the olfactory mucosa . In the area of ​​the ethmoid bone , a kind of nasal septum is formed that divides the internal airways into two separate tubes. It thus appears possible that Brontotherien breathed obligatorily through the nose and not through the mouth. Something similar is also known of today's horses , which are considered the closest recent relatives of the Brontotherien, as well as, with individual restrictions, of the rhinos . A function in a possible aquatic way of life could also be considered with less probability. Theoretically, the displacement of the internal airways to the rear would support the air supply when the throat is filled with water, but this has not yet been anatomically clear.

Paleoenvironment

Due to the eating habits of the Brontotherien with their preferred food and the required water, the animals are likely to have lived largely in dense, closed forests interspersed with rivers and swamps with humid climatic conditions. Among other things, the isotope studies on teeth from the Chadron Formation in the catchment area of ​​the White River , which belongs to the Upper Eocene, suggest this. These are supported by a large part of the geological and paleontological find conditions . Analyzes of the palaeoflora of the also Upper Ocene Australian Creek Formation in British Columbia , which contained tooth remains from Brontotherien, allow a reconstruction of coniferous and deciduous mixed forests under moderate climatic conditions. The annual average temperature is estimated at around 13 ° C with an average for the coldest month of −4 ° C. The annual average precipitation was 115 cm. In contrast, the Brontotherien also showed a certain adaptability to extreme environmental conditions, as the legacies of the Lower Middle Eocene Margaret Formation on Ellesmere Island in the far north of Canada suggest. The former environment can be assumed to be comparable to that of the Australian Creek and Chadron Formations, but it was subject to the effects of the polar day and the polar night with alternating light and dark for several months. This probably caused regular shortages of food crops in the annual cycle. To what extent the animals spent the entire year here in the far north is still unclear, but young animals have been documented for some forms, which make a permanent presence likely.

Systematics

External system

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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The three main lines (mostly viewed as subordinates) of the unpaired ungulates are the Ceratomorpha, Ancylopoda and Hippomorpha, whereby the Brontotheria are often assigned to the Hippomorpha and thus are closely related to the horses. The Tapiromorpha represent a superordinate taxon, which underlines the closer relationship of the Ceratomorpha and Ancylopoda.

The Brontotheriidae are an extinct family from the order of the odd ungulate (Perissodactyla). The unpaired ungulates are traditionally divided into two major suborders, the Hippomorpha and the Ceratomorpha , with ancylopoda later being introduced as a third. The Brontotherien are usually placed next to the Hippomorpha and are therefore more closely related to the horses than to the rhinos , which represent representatives of the Ceratomorpha, despite their different appearance in the developed forms . The relationship with the early horses can be seen in numerous skull features, such as the structure of the broad nasal bone or the short symphysis of the lower jaw and, furthermore, the teeth. The closest related group are the also extinct Lambdotheriidae , with which the Brontotheria together form the superfamily Brontotherioidea . But there are also views that the Brontotherien together with the Lambdotherien occupy a very basal position within the odd-toed ungulates, as they combine numerous very original features of this mammal order. In this case, the Brontotheria and their relatives are assigned to their own suborder Titanotheriomorpha. However, the exact relationships between the horses and the Brontotherien and again to the other odd-toed ungulates have not yet been precisely researched.

Internal system

Originally, the individual Brontotheria genera were assigned to different subfamilies such as Brontotheriinae, Telmatheriinae or Embolotheriinae. The internal systematics of the family was largely only well investigated for the North American representatives, while that of the Eurasian forms was only rarely taken into account. Although these were also organized in individual subfamilies, there were problems in connection with the American representatives. This fact was only remedied during a major revision of the Brontotherien by Matthew C. Mihlbachler in 2008. This was followed in 2010 by Bryn J. Mader, a partial revision of the earliest representatives, which Mihlbachler had given little consideration. After these two revisions, three subfamilies remained for the time being within the Brontotheri, whereby that of the Brontotheriinae contains all more modern forms. As a result, all other higher taxa were shifted to the level of tribes , sub- tribes and intermediate tribes . Here again the Brontotheriina represent all Brontotheriina with horn formations, while the Telmatheriina only show bone swellings and the Rhadinorhinina no such features. The intermediate branches of the Brontotheriita and Embolotheriita differ in the construction of the horns. The former usually have two separate horns, the latter closely spaced or overgrown and sometimes shaped like a battering ram. The individual groups and lines of the Brontotherien are not geographically bound, but show a diverse network of relationships across the different continents of their prevalence at the time. This suggests a multiple and in different directions running fauna exchange between the individual land masses during the tribal history of the Brontotherien.

Overview of the genera

Internal systematics of the Brontotheriidae according to Mihlbachler 2008 and Mader 2010
  Brontotheriidae  

 Eotitanopinae


   

 Palaeosyopinae


   

 Brontotheriinae


   

 Brontotheriini


   

 Rhadinorhinina


   

 Telmatheriina


   

 Brontotheriina


   

 Brontotheriita


   

 Embolotheriita










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A total of more than 40 genera from the Brontotheriidae family are known today; the last extensive revision of the family took place in 2008, as mentioned above. The following structure was proposed, whereby modifications according to Mader from 2010 and more recent discoveries have been incorporated:

  • Family: Brontotheriidae Marsh , 1873
  • Palaeosyops (= Limnohyops , Limnohyus , Eometarhinus ) Leidy , 1870

Some taxa are regarded as uncertain in their genus status, but are sometimes listed as follows in the literature:

  • Arctotitan Wang , 1978
  • Mulkrajanops Kumar & Sahni , 1985
  • Sivatitanops Pilgrim , 1925

Tribal history

Adaptive radiation

General evolutionary trends of the Brontotherien can be found in the increase in body size and the formation of bony horns at the transition from the nasal to the frontal bone. The skull underwent very clear changes, which in the original representatives was still very flat or slightly arched. The increasing lengthening of the occiput with the resulting low head position also caused a sometimes clearly saddled forehead line. Furthermore, there were shortenings in the anterior area of ​​the snout , which led to a change in the position of the orbit in relation to the position of the teeth. The early Brontotheria had an eye window above or slightly behind the third molar, while later ones had this above the first or second molar. This also showed that the modern representatives had a very extensive posterior skull. In the dentition, the premolars were modified, becoming more and more similar to the molars, and a diastema was formed in some lines . Due to the change in diet of early representatives of more on fruits based on leaf-rich diet of emerged over evolutionary history from the bunodonten molars clearly lophodonte (with transversely positioned enamel strips) to selenodonten designed (with crescent-like enamel strips) molars. The number of teeth hardly changed, only a few late Brontotheria had one less incisor each in their front teeth. The fauna exchange most likely took place over the far north.

Origin and development

Lower jaw fragment from Danjiangia
Development of the Brontotherien after Henry Fairfield Osborn (1857–1935) from 1929

The evolution of this group is well known due to the excellent fossil record from North America and East and Central Asia , but its origin is not yet fully understood. Some researchers believe that the Brontotherien originated in North America. There the earliest forms appeared in the Lower Eocene around 53 million years ago (locally stratigraphically called Wasatchian ). Lambdotherium , which was originally regarded as the most basic form of Brontotherium, but now belongs to a family of its own, is considered a possible starting form. Early finds come with two partial skeletons from the Fossil Butte Member of the Green River Formation in the Green River Basin in the northwestern United States . These date in the local stratigraphic Faunenzone Lostcabinian and are around 52 million years old. Overall, the early North American Brontotheria were still quite small forms such as Eotitanops or Palaeosyops , which had a shoulder height of one meter and less and were still polled; for the former, a weight of around 140 kg is calculated. While they were at that time a relatively rare faunal, but finds are also from the very far north of North America, among others, from the Margaret lineup today's Ellesmere Island and the Buchanan Lake Formation of today's Axel Heiberg Island demonstrated that back then they were still overgrown by swamp forests. According to some other researchers, the group could also originate in Asia. Here is Danjiangia a possibly very early member of the Lingcha lineup in the Chinese province of Henan occupied. It shows some similarities with Lambdotherium , but with a dating in the Paleocene- Eocene transition region around 56 million years ago, it is somewhat older (locally stratigraphically called Bumbanium ). Other early forms from Asia have been reported with Balochititanops from the Ghazij formation in the Kingri region in Baluchistan ; they occurred around the same time as their North American relatives.

The heyday of the Brontotherien, however, was the Middle Eocene, about 50 to 37 million years ago, about two dozen genera are known from that epoch. The strong increase in body size was particularly striking. For the early Middle Eocene finds of the still quite primeval bunobrontop from the Pondaung Formation of Myanmar a weight of 510 to 990 kg is estimated, however the genus is mostly only known from teeth. On the other hand, the weight estimates for the genetically but historically younger forms Wickia and Metatelmatherium, which appear around the same time, are around 1.6 to 2.1 t. Contrary to this trend of increasing body size, however, dwarf forms occasionally emerged. The process has not yet been fully clarified, but dwarfs occurred several times in the course of the tribal history of the Brontotherien and are covered with nanotitanops and xylotitan , among other things . The general increase in height was also associated with an increase in skull size. As with Dolichorhinus, the skulls developed into very elongated shapes, with the eyes well forward. Clear horn formations can be observed for the first time in the late Middle Eocene, but the development took place in several stages. In some forms, the frontal bone began to grow over the nasal bone with small, triangular-shaped bony outgrowths. This is known, among other things, from Telmatherium , which has been passed down through unusually rich fossil material from the Twin Buttes from the Bridger Basin in Wyoming . The genus was often adopted earlier as the sister taxon to all other horn-bearing Brontotheria. Small bony outgrowths then formed later, as demonstrated in the Asian rhinotitan and the North American protitanotherium . Only then did the classic horns form. Also in the late Middle Eocene, Brontotherien reached Europe for a short time, but this group of odd ungulates is only rarely found there. A fragment of the lower jaw of Brachydiastematherium was found near Cluj-Napoca in Romania . The tooth finds and remains of the lower jaw from Kameno and Cherno More , both Bulgaria , are somewhat younger and date from the Upper Eocene, but their exact systematic position is disputed. Overall, the mid-Eocene Brontotheria were the most diverse group of large mammals in both North America and Asia. It is noteworthy that there was no independent radiation on either of the two continents ; rather, the phylogenetic development is strongly interlinked. Some researchers suggest up to a dozen independent intercontinental waves of propagation traveling in both directions.

In the Upper Eocene, 37 to 34 million years ago, the number of different Brontotheria forms gradually decreased. About ten genres are known from this period, but most of them are in the early phase of the epoch. All proven Brontotheria were horn-bearing and mostly very large, like the Megacerops , which may weigh up to 3 tons . Two different lines developed: those with two widely spaced horns closely related to Megacerops and those with two closely spaced or fused horns that are closely related to Embolotherium . Towards the end of the Eocene there were climate changes in the form of a drop in temperature, which intensified in the course of the Oligocene and during which the first grasses spread in connection with open landscapes. It is possible that the Brontotherien were unable to adapt their highly specialized diet to these landscape changes in the middle and higher latitudes, where they were mainly common, and were displaced by more competitive herbivores, such as the ascending groups of rhinos and chalicotherias . Most of the Brontotherien disappeared before the end of the Eocene, only Megacerops persisted until about 34 million years ago.

Research history

Othniel Charles Marsh
The first lower jaw presented by Hiram A. Prout from a representative of Brontotherien from 1847

The exploration of the Brontotherien dates back to the 1840s and began in North America with the first discovery of the remains of this odd ungulate group. The first find, a mandibular fragment with the three posterior molars preserved, goes back to Hiram A. Prout and comes from the Badlands of the White River in South Dakota . In a short publication published in 1846, Prout referred to the lower jaw discovery as belonging to a huge palaeotherium , a primeval horse relative, and a year later he described the lower jaw in more detail. Joseph Leidy (1823-1891), who is considered to be one of the founders of palaeontology in North America, later (in 1852) referred to Titanotherium , where he used the name marginally, for further finds from the same region, including the remains of the lower jaw presented and illustrated by Prout mentioned. However, the French researcher Auguste Pomel (1821–1898) had already described this lower jaw find in 1849 under the name Menodus , which predated this name to Titanotherium . Pomel not only named the genus, but added the species Menodus giganteus to it, in contrast to Prout and later Leidy . Thus, it is the oldest binomial in research history that was assigned to a Brontotherien representative. In addition, the lower jaw and the associated species name is the first scientific name given to a fossil from the extremely rich area of ​​the Badlands of the White River. For a long time, Prout's fossil find was considered lost, it was supposed to be in the year of Pomel's publication during a major city fire lost in St. Louis , but reappeared in 1957 in the National Museum of Natural History in Washington, DC (now listed as USNM 21820). The name Menodus giganteus is now considered invalid, on the one hand due to the eventful history of the original find and the numerous genera and species listed after it, on the other hand it cannot be assigned to any of the currently valid species of Brontotheria (in the narrower sense of Megacerops ). As early as the 1850s, the American geologist Ferdinand Hayden (1829–1887) found an extremely rich fossil material in the badlands, including numerous Brontotherien, with which he made an important contribution to this very early research period. In the 1870s to 1890s research on Brontotherien was overshadowed by the Cope-Marsh feud , also known as "bone wars", led by the two American paleontologists Edward Drinker Cope (1840–1897) and Othniel Charles Marsh (1831–1899) . It was Marsh who first used the name Brontotherium in 1873 and defined it based on three skeletons from the Peabody Museum of Natural History at Yale University . However, Brontotherium is only synonymous with Megacerops . This name also originally comes from Leidy, which he published in 1870, and was introduced by him using a skull from Colorado , where he recognized similarities to his previously named genus Titanotherium . During this time, Cope and Marsh collected vast amounts of fossil material in North America, especially in the two Dakota states and Nebraska ; the latter hired John Bell Hatcher in the 1880s , who sent him 11,000 t of finds from 1886 to 1888 alone. Numerous genera were also named, some of which - as it turned out later - were identical to others. In addition to these outstanding finds, the only non-American fossils known in the 19th century were a few remains of teeth from southeastern Europe, which were published in the 1870s and 1890s.

In the same publication in which Marsh introduced the genus Brontotherium , he described this genus and Leidy's Titanotherium as belonging to the Brontotheriidae family (although written as Brontotheridae, the incorrect spelling was not officially corrected until 1902 by Oliver Perry Hay ), the name that is valid today. He also recognized the systematic membership of the odd-toed ungulate , but he only referred the younger forms to this group. On the other hand, he placed older genera such as Diplacodon in the Limnohyidae family. Only Cope united the two families in 1879. At the end of the 19th century, however, several names were in use for the Brontotheriidae family, including Menodontidae, which Cope established in 1881, or Titanotheriidae by the British scientist William Henry Flower from 1876. Independently of Flower and probably in ignorance of his script, Henry Fairfield Osborn (1857-1935) established the family term Titanotheriidae again in 1889 and used it throughout his life. Although this name is rarely used today, as it is a synonym for Brontotheriidae, it is derived from Leidy's Titanotherium .

At the beginning of the 20th century and after Marsh's death, it was Osborn who significantly advanced the research. Osborn, who worked at the American Museum of Natural History , got access to the records of Marsh and Cope and in the following time worked on a monograph on the Brontotherien (which he generally referred to as Titanotherien). In the 1920s he organized expeditions to East Asia to the Gobi Desert , which took place between 1922 and 1930 and are known as the Central Asiatic Expeditions of the American Museum of Natural History . During these expeditions, mostly led by Roy Chapman Andrews and Walter W. Granger , in addition to dinosaurs and other fossil animals, countless remains of Brontotheria with previously unknown forms were discovered, such as Embolotherium or Gnathotitan , which was the previously only suspected distribution of this odd ungulate group until Asia was proven. Osborn worked on the material step by step in numerous publications, in 1929 his more than 890 page comprehensive work with an additional 230 plates under the title Titanotheres of ancient Wyoming, Dakota, and Nebraska on the North American finds appeared; However, this still contained an appendix of more than 40 pages about the finds from East Asia. After Osborn's death in 1935, Walter W. Granger and William King Gregory continued his work.

literature

  • Matthew C. Mihlbachler: Species taxonomy, phylogeny, and biogeography of the Brontotheriidae (Mammalia: Perissodactyla). In: Bulletin of the American Museum of Natural History. No. 311, June 2008, ISSN  0003-0090 , pp. 1-475, (online) .

Individual evidence

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  4. ^ A b Matthew C. Mihlbachler, Spencer G. Lucas, Robert J. Emry and Bolat Bayshashov: A New Brontothere (Brontotheriidae, Perissodactyla, Mammalia) from the Eocene of the Ily Basin of Kazakstan and a Phylogeny of Asian “Horned” Brontotheres. In: American Museum Novitates 3439, 2004, pp. 1–43, doi : 10.1206 / 0003-0082 (2004) 439 <0001: ANBBPM> 2.0.CO; 2 .
  5. ↑ a b c d e f g h i j k l m n o p q Matthew C. Mihlbachler: Species taxonomy, phylogeny, and biogeography of the Brontotheriidae (Mammalia: Perissodactyla). In: Bulletin of the American Museum of Natural History 311, 2008, ISSN  0003-0090 , pp. 1-475.
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  8. ^ Matthew C. Mihlbachler and Nikos Solounias Niko: Anatomy and Evolution of the Bizarre “Battering Ram” of the Brontothere, Embolotherium (Mammalia, Perissodactyla). In: Journal of Morphology Special Issue : Seventh International Congress of Vertebrate Morphology, Boca Raton, Florida, July 27 to August 1, 2004. 260 (3), 2004, pp. 274-342 (p. 313).
  9. ↑ Bryn J. Mader and John P. Alexander: Megacerops kuwagatarhinus n. Sp., An unusual brontothere (Mammalia, Perissodactyla) with distally forked horns. In: Journal of Paleontology 69, 1995, pp. 581-587, ( online ).
  10. ↑ a b c Matthew C. Mihlbachler: A New Uintan Horned Brontothere from Wyoming and the Evolution of Canine Size and Sexual Dimorphism in the Brontotheriidae (Perissodactyla: Mammalia). In: Journal of Vertebrate Paleontology 31 (1), 2011, pp. 202-214, doi: 10.1080 / 02724634.2011.539653 .
  11. ↑ a b Jaelyn J. Eberle and David R. Greenwood: An Eocene brontothere and tillodonts (Mammalia) from British Columbia, and Their paleoenvironments. In: Canadian Journal of Earth Sciences 54, 2017, pp. 981-992.
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  13. ^ Matthew C. Mihlbachler and Thomas A. Deméré: A New Species of Brontotheriidae (Perissodactyla, Mammalia) from the Santiago Formation (Duchesnean, Middle Eocene) of Southern California. In: Proceedings of the San Diego Society of Natural History 41, 2009, pp. 1-36.
  14. ↑ a b c Jaelyn J. Eberle: Early Eocene Brontotheriidae (Perissodactyla) from the Eureka Sound Group, Ellesmere Island, Canadian High Arctic - Implications for Brontothere origins and high latitude dispersal. In: Journal of Vertebrate Paleontology , 26 (2), 2006, pp. 381-386.
  15. ↑ a b c d Jaelyn J. Eberle and David R. Greenwood: Life at the top of the Eocene greenhouse world - A review of the Eocene flora and vertebrate fauna from Canada's High Arctic. In: Geological Society of America Bulletin ; January / February 124 (1/2), 2012, pp. 3–23, ( PDF ).
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  18. ↑ Wang Ban Yue: A Skull of Embolotherium (Perissodactyla, Mammalia) from Erden Obo, Nei Mongol, China. In: Vertebrata Palasiatica 38 (3), 2000, pp. 237-240.
  19. ^ A b c Pieter Missiaen, Gregg F. Gunnell, and Philip D. Gringerich: New Brontotheridae (Mammalia, Perissodactyla) from the Early and Middle Eocene of Pakistan with implications for Mammalian palaeobiogeography. In: Journal of Paleontology 85 (4), 2011, pp. 665-677.
  20. ↑ a b Christine Janis: An Evolutionary History of Browsing and Grazing Ungulates. In: IJ Gordon and HHT Prins (eds.): The Ecology of Browsing and Grazing. , In: Ecological Studies 195, 2008, pp. 21–45.
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  22. ↑ Angana Homchaudhuri, Matthew C. Mihlbachler and Nikos Solounias: Dental microwear analysis of Eocene Brontotherioidea and implications for paleodietary interpretations of long extinct species. In: Journal of Vertebrate Paleontology 30 (suppl.), 2010, p. 107A.
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  24. ↑ a b Spencer George Lucas and Robert M. Schoch: Taxonomy of Duchesneodus (Brontotheriidae) from the late Eocene of North America. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of Perissodactyls. New York and Oxford, 1989, pp. 490-503.
  25. ↑ Christine M. Janis, Boris Shoshitaishvili, Robert Kambic and Borja Figueirido: On their knees: Distal Femur asymmetry in Ungulates and its relationship to body size and locomotion. In: Journal of Vertebrate Paleontology 32 (2), 2012, pp. 433-445, doi: 10.1080 / 02724634.2012.635737 .
  26. ↑ Benjamin McLaughin, Matthew C. Mihlbachler and Mick Ellison: The postcranial skeleton of embolotherium (brontotheriidae) from the Middle and Late Eocne of Central Asia. In: Journal of Vertebrate Paleontology 30 (suppl.), 2010, pp. 132A-133A.
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  29. ↑ a b Luke T. Holbrook and Joshua Lapergola: A new genus of Perissodactyl (Mammalia) from the Bridgerian of Wyoming, with comments on basal Perissodactyl phylogeny. In: Journal of Vertebrate Paleontology 31 (4), 2011, pp. 895-901, doi: 10.1080 / 02724634.2011.579669 .
  30. ↑ JJ Hooker and D. Dashzeveg: The origin of chalicotheres (Perissodactyla, Mammalia). In: Palaeontology 47 (6), 2004, pp. 1363-1386, ( PDF ).
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  32. ↑ Bryn J. Mader: Brontotheriidae. In: Christine M. Janus, Kathleen M. Scott and Louis L. Jacobs (eds.): Evolution of Tertiary mammals from North America, Vol. 1. Cambridge 1998, pp. 525-536.
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  34. ↑ a b c d e f Matthew C. Mihlbachler and Joshua X. Samuels: A small-bodied species of Brontotheriidae from the middle Eocene Nut Beds of the Clarno Formation, John Day Basin, Oregon. In: Journal of Paleontology 90 (6), 2016, pp. 1233-1244 doi: 10.1017 / jpa.2016.61 .
  35. ↑ Alexander Averianov, Igor Danilov, Wen Chen and Jianhua Jin: A new brontothere from the Eocene of South China. In: Acta Palaeontologica Polonica 63 (1). 2018, pp. 189–196 doi: 10.4202 / app.00431.2017 .
  36. ↑ a b Bin Bai, Yuan-Qing Wang and Jin Meng: The divergence and dispersal of early perissodactyls as evidenced by early Eocene equids from Asia. In: Communications Biology 1, 2018, p. 115 doi: 10.1038 / s42003-018-0116-5 .
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  40. ↑ Takehisa Tsubamoto, Naoko Egi, Masanaru Takai, Chit Sein and Maung Maung: Middle Eocene ungulate mammals from Myanmar: A review with description of new specimens. In: Acta Palaeontologica Polonica 50 (1), 2005, pp. 117-138, ( PDF ).
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