Research history First descriptions In 1782, the French naturalist
Robert de Lamanon described a fossil skull including the upper and lower jaws that was collected from the quarries of
Montmartre, a hill near
Paris that belonged to the nobleman
Philippe-Laurent de Joubert. He recognized that the
molars and
incisors were roughly similar to those of
ruminants but noted that the dentition lacked modern analogues. Consequently, he hypothesized that the animal was extinct, had an amphibious lifestyle, and fed on both plants and fish. Since 1796, the French naturalist
Georges Cuvier innovated the idea of vanished worlds of extinct animals, but as his observations of fossils were mostly limited to drawings and fragmentary fossils stored at the
National Museum of Natural History, France, his palaeontological insight was limited early on. Later in the same year, he instead suggested that the fossils belonged to a
pachyderm that was most closely related to tapirs and had trunks like them. He also figured out that the animals of Montmartre were of multiple species with different sizes and numbers of toes. The genus name
Palaeotherium means "ancient beast", which is a compound of the
Greek prefix () meaning 'old' or 'ancient' and the suffix () meaning 'beast' or 'wild animal'. He debunked Lamanon's hypothesis that
Palaeotherium was an omnivorous amphibian and suspected that it had trunks akin to those of tapirs. He erected the second of these species,
P. magnum, in 1804, explaining that it had similar but larger-sized dentition than
P. medium. In describing the third and small-sized species,
P. minus, he began to focus on the study of postcranial material rather than just cranial and dental material. In 1805, Cuvier erected
P. crassum based on the three-toed forefeet, which were similar to tapirs and rhinoceroses in the shape of the
metacarpal bones. In 1812, he named another species,
P. curtum, based on metacarpal bones that were slightly smaller than those of
P. crassum. As of 1968, four of the
Palaeotherium species named by Cuvier were considered valid and remained classified in
Palaeotherium (
P. medium,
P. magnum,
P. crassum,
P. curtum), six were valid but were eventually reclassified to different genera by different palaeontologists (
P. minus,
P. tapiroïdes,
P. buxovillanum,
P. aurelianense,
P. occitanicum, and
P. isselanum), and three were considered invalid (
P. giganteum,
P. latum, and
P. indeterminatum). In 1812, Cuvier defined
Palaeotherium as containing only tridactyl (or three-toed) species. He also speculated on life appearance and behaviour of several
Palaeotherium species, but cautioned that such interpretations are limited by the fragmentary fossil material. He suggested that
P. magnum would have resembled a horse-sized tapir with sparse hair.
P. crassum and
P. medium would also have had a tapir-like appearance, with proportionally longer legs and feet in the latter. Cuvier also published a speculative skeletal reconstruction of
P. minus and hypothesized that it was smaller than a sheep and potentially cursorial given its slender legs and face. Finally, he theorized that
P. curtum would have been the bulkiest species. In 1822, Cuvier published a reconstruction of the skeleton of
P. magnum, outlining that it was the size of a
Javan rhinoceros, was stocky in build, and had a massive head. The same year,
Palaeotherium was also depicted in drawings by the French palaeontologist
Charles Léopold Laurillard under the direction of Cuvier. Three sculptures representing
Palaeotherium magnum,
Palaeotherium medium and "
Plagiolophus minus" (=
Plagiolophus) are part of the
Crystal Palace Dinosaurs exhibition in the
Crystal Palace Park in London, which has been open to the public since 1854 and was created by the English sculptor
Benjamin Waterhouse Hawkins. Both the
P. magnum sculpture, the largest of the three, and the medium-sized
P. medium sculpture were posed in a standing position, whereas the smaller "
P. minus" sculpture depicts a sitting animal. The resemblance of the models to tapirs reflects early perceptions of the life appearance of
Palaeotherium. However, the sculptures differ from living tapirs in several ways, such as shorter and taller faces, higher eye positions, slimmer legs, longer tails, and the presence of three toes on the forelimbs unlike the four toes of tapirs. Of the three sculptures,
P. medium most closely resembles a tapir, and it has remained mostly intact.
P. medium was depicted as having thick skin and a slender face and trunk, representing outdated perceptions that it was a slow animal. The original
P. magnum sculpture was last known from a 1958 photograph before it was lost at some point afterward (it was replaced by a new republicated model in 2023); the photograph reveals that it was the largest of the three sculptures and had a robust and muscular build with large and deep eyes, a proportionally large head, and bulky legs. The model's trunk was wide and descended below the lower lip. The overall anatomy appears to be based on elephants.
Palaeotherium proved to be a significant find to the field of palaeontology in multiple other aspects. For one, both the skeletal reconstruction drawing and the life restoration in Cuvier's works were incorporated into textbooks and handbooks around the world up to the 20th century. The genus was also incorporated into old
orthogenesis models of the
evolution of the horse theory as early as 1851 by British biologist
Richard Owen and followed by other 19th century European naturalists such as
Jean Albert Gaudry and
Vladimir Kovalevsky.
Later 19th century taxonomy In the 19th century, several of Cuvier's
Palaeotherium species have been reclassified under different genera. but the latter two were eventually moved to
Paralophiodon and
Lophiaspis, respectively, in the 20th century. In 1862, Swiss zoologist
Ludwig Ruetimeyer considered the previously recognised genera
Plagiolophus and
Propalaeotherium as distinct from
Palaeotherium; these contain the species
P. minor and
P. isselanum, respectively. The 19th century also saw the erection of several new
Palaeotherium species. In 1853, French palaeontologist
Auguste Pomel erected the species
P. duvali based on limb bones that he thought were less stocky than those of
P. curtum. In his 1839–1864 osteography, Blainville erected
P. girondicum, pointing out that its fossils were from the
Gironde Basin and that Cuvier only briefly referenced it in an 1825 publication. In 1869, Swiss palaeontologists
François Jules Pictet de la Rive and
Aloïs Humbert erected the species
Plagiolophus siderolithicus based on molars that are similar to those of
P. minor but were smaller in size. The same year, German palaeontologist
Oscar Fraas erected
P. suevicum based on teeth that he thought had distinct
enamel. The French naturalist
Paul Gervais, in 1875, described fossil bones and teeth from the French commune of
Dampleux, noting that they belonged to a species smaller than other
Palaeotherium species and with dental dimensions similar to those of
Plagiolophus minor. He assigned the fossils to the newly erected species
P. eocaenum.
Palaeotherium skeletons In 1873, the French geologist
Gaston Casimir Vasseur uncovered the first complete skeleton of
Palaotherium, attributed to
P. magnum, from a gypsum quarry in the commune of
Vitry-sur-Seine. The quarry was owned by the civil engineer Fuchs, who donated the skeleton to the National Museum of Natural History, France. The skeleton was described by Gervais in the same year, who noted that the neck was longer than expected and that the build was less stocky than that of tapirs and rhinoceroses. The skull of the specimen measures long. The naturalist said that the excavation of the specimen was difficult but completed by multiple skillful workers. In his monography on palaeotheres, published the same year, Stehlin considered most species of
Palaeotherium as potentially
valid, but noted that most taxonomists were reluctant to invalidate species erected by Cuvier. Stehlin considered
P. girondicum to be a form of
P. magnum, and described two forms of
P. curtum from jaw fragments from La Débruge. He also named three new species –
P. Mühlbergi, based on dental material from the Swiss municipality of
Obergösgen;
P. Renevieri, based on new finds from Mormont and a mandible identified by Pictet in 1869; and
P. Rütimeyeri, from the municipality of
Egerkingen, which he described as having primitive premolars. In 1917, French palaeontologist
Charles Depéret recognized two additional species of
Palaeotherium –
P. Euzetense and
P. Stehlini. In 1968, upcoming German palaeontologist
Jens Lorenz Franzen, then a graduate student, made major revisions of
Palaeotherium in his dissertation. He invalidated several species as dubious names (
P. giganteum (considered to have been a
rhinocerotid instead),
P. gracile,
P. parvulum,
P. commune,
P. primaevum, and
P. gervaisii) and synonymized many others with
P. magnum (
P. aniciense,
P. subgracile),
P. medium (
P. brivatense,
P. moeschi),
P. crassum (
P. indeterminatum),
P. curtum (
P. latum and
P. buseri),
P. duvali (
P. kleini), and
P. muehlbergi (
P. velaunum). He additionally invalidated many species that had been erected throughout the 19th and early 20th centuries. He also erected
P. pomeli based on fossils from a locality in Castres and reclassified "
Plagiolophus"
siderolithicum as a species of
Palaeotherium. Furthermore, Franzen converted some species into subspecies (
P. magnum girondicum,
P. magnum stehlini,
P. medium suevicum, and
P. medium euzetense) and named six additional subspecies. In 1980, both she and José-Vicente Santafé Llopis established a second Iberian species,
P. franzeni, from the Spanish municipality of
Sossís based on differences in dentition. In 1985, the French palaeontologist Jean-Albert Remy named a new subspecies,
P. muehlbergi thaleri, in honor of fellow palaeontologist Louis Thaler; these fossils, consisting of two skulls with mandibles, were from the commune of
Saint-Étienne-de-l'Olm. In 1991, Casanovas-Cladellas and Santafé Llopis erected
P. llamaquiquense from partial jaw material from the Spanish locality of Llamaquique in the city of
Oviedo, where the name derived from. The next year in 1992, Remy proposed the creation of two subgenera of
Palaeotherium based on cranial characteristics:
Palaeotherium and
Franzenitherium. In 1993, the Spanish palaeontologist Miguel Ángel Cuesta Ruiz-Colmenares established the species
P. giganteum based on teeth from the
Mazaterón site in the
Duero Basin, considering it to be the largest species of
Palaeotherium known. In 1998, Casanovas-Cladellas
et al. erected the subspecies
P. crassum sossissense from a fragmented right maxilla with dentition from Sossís in Spain. They also invalidated the previously named
P. franzeni and reassigned the material to
P. magnum stehlini.
Classification and evolution , the French naturalist who described
Palaeotherium and
Anoplotherium in 1804
Palaeotherium is the type genus of the Palaeotheriidae, largely considered to be one of two major
hippomorph families in the superfamily
Equoidea, the other being the
Equidae. Alternatively, some authors have proposed that equids are more closely related to the
Tapiromorpha than to the Palaeotheriidae. It is also usually thought to consist of two families, the
Palaeotheriinae and
Pachynolophinae; a few authors alternatively have argued that pachynolophines are more closely related to other perissodactyl groups than to palaeotheriines. Some authors have also considered the Plagiolophinae to be a separate subfamily, while others group its genera into the Palaeotheriinae.
Palaeotherium has also been suggested to belong to the tribe
Palaeotheriini, one of three proposed tribes within the Palaeotheriinae along with the
Leptolophini and
Plagiolophini. The Eurasian distribution of the palaeotheriids (or palaeotheres) were in contrast to equids, which are generally thought to have been an endemic radiation in North America. Some of the most basal equoids of the European landmass are of uncertain affinities, with some genera being thought to potentially belong to the Equidae. Palaeotheres are well-known for having lived in western Europe during much of the Palaeogene but were also present in eastern Europe, possibly the Middle East, and, in the case of pachynolophines (or pachynolophs), Asia. The MP13 unit saw the appearances of later pachynolophines such as
Pachynolophus and
Anchilophus along with definite records of the first palaeotheriines such as
Palaeotherium and
Paraplagiolophus. The palaeotheriine
Plagiolophus has been suggested to have potentially made an appearance by MP12. It was by MP14 that the subfamily proceeded to diversify, and the pachynolophines were generally replaced but still reached the late Eocene. In addition to more widespread palaeothere genera such as
Plagiolophus,
Palaeotherium, and
Leptolophus, some of their species reaching medium to large sizes, various other palaeothere genera that were endemic to the Iberian Peninsula, such as
Cantabrotherium,
Franzenium, and
Iberolophus, appeared by the middle Eocene. Later since 1992, two subgenera are officially recognized for
Palaeotherium. The first of these subgenera is
Palaeotherium, which includes the type species
P. magnum along with
P. medium,
P. crassum,
P. curtum,
P. castrense,
P. siderolithicum, and
P. muehlbergi. The second subgenus is
Franzenitherium, which includes the type species
P. lautricense as well as
P. duvali and was named in honor of Franzen's review of
Palaeotherium. The subgenus
Palaeotherium is distinct from another subgenus
Franzenitherium based on specialized traits. For example, the orbit of
Palaeotherium being aligned in front of the skull's midlength is a specialized trait compared to that of
Franzenitherium being aligned more with the skull's midlength. Several
Palaeotherium species are too fragmentary to be placed in any of the subgenera. The following table lists all valid species and subspecies of
Palaeotherium, the subgenus that each is classified to, the Mammal Palaeogene faunal units that they are recorded from based on fossil deposit appearances, the authors who named the taxa, and the year that they were formally named: == Description ==