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The first finds were probably made by a fossil dealer in the early 1990s from an unknown location. The two fragments of the upper jaw were coated with phosphate, and the preparation of the finds revealed the tooth of a fossil shark, which dates to the late Paleocene (
''Phosphatherium'' is thought to have had a broad diet. The
''Phosphatherium escuillei'' is a basal
One of the main factors of ''Phosphatherium'' body is its nontraditional musculoskeletal system. The shape of its head is composed of attributes of a snout, more vividly, turning into
a mouth with a rounded jawline. Similar mammals in its order retained a more snout-like nose, which was also a factor that pertained to it having a semiaquatic lifestyle. Furthermore, sexual dimorphism can be noticed on ''Phosphatherium'' face by a varying degrees of muscle attachments on its upper jaw.heterodont, meaning it possessed more than one type of tooth morphology. This is evident because they possessed more than one type of molar upon fossil examinations. The various dental formations of heterodonts suggest that this animal, unlike later proboscideans, may have been omnivorous.
The unique traits of ''Phosphatherium'' teeth suggest them to be
(I2) was enlarged and conical in shape, but was perpendicular to the bone. In the lower jaw, on the other hand, the first incisor (I1) showed clear enlargements. However, both teeth did not yet form true tusks. The anterior dentition did not show a closed row of teeth, in the upper jaw there was an additional small proboscidean
The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. From ...
that lived from the Late Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...
to the early stages of the Ypresian
In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...
age until the early Thanetian
The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age ( ...
some 56 million years ago in North Africa. Research has suggested that ''Phosphatherium'' existed during the Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
period.
Description
''P. escuillei'' possessed rather flat features, centered around a low skull and a long, straight dorsal profile. The skull itself was rather disproportionate, consisting of an elongated cranial region and a rather short rostrum. The sagittal crest, the ridge along the dorsomedian line of its skull, spans across nearly half of the skull itself. The nasal cavity is high and wide, suggesting a large snout in life.
One of the main factors of ''Phosphatherium'' body is its nontraditional musculoskeletal system. The shape of its head is composed of attributes of a snout, more vividly, turning into
a mouth with a rounded jawline. Similar mammals in its order retained a more snout-like nose, which was also a factor that pertained to it having a semiaquatic lifestyle. Furthermore, sexual dimorphism can be noticed on ''Phosphatherium'' face by a varying degrees of muscle attachments on its upper jaw.heterodont, meaning it possessed more than one type of tooth morphology. This is evident because they possessed more than one type of molar upon fossil examinations. The various dental formations of heterodonts suggest that this animal, unlike later proboscideans, may have been omnivorous.
The unique traits of ''Phosphatherium'' teeth suggest them to be intraspecific
Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.
Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...
. Some features of ''P. escuilliei''sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
. This suggests physiological differences existed between males and females, which ultimately suggest behavioral differences.incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...diastema
A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition ...
behind the first premolar. The premolars as a whole were quite simply built and not very molarised, i.e. they hardly resembled the molar. These had a bilophodont structure with two clearly formed transverse enamel ridges. The rearmost molar of the mandible, however, had a third enamel bar. In general, the teeth were brachyodont
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
.
Discovery
The first finds were probably made by a fossil dealer in the early 1990s from an unknown location. The two fragments of the upper jaw were coated with phosphate, and the preparation of the finds revealed the tooth of a fossil shark, which dates to the late Paleocene (Thanetian
The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age ( ...
) and thus confirms the ancient age of the finds. The holotype (copy number MNHN PM2) consists of a right upper part of the jaw with the last two premolars and the first two molars (P3 to M2). It is now in the Muséum National d'Histoire Naturelle
The French National Museum of Natural History, known in French as the ' (abbreviation MNHN), is the national natural history museum of France and a ' of higher education part of Sorbonne Universities. The main museum, with four galleries, is loc ...
in Paris. The first scientific description took place in 1996 by Emmanuel Gheerbrant and colleagues. The name Phosphatherium is made up of the Greek words φωςφορος (phosphoros "light-bearing") and θηρίον ( thērion "animal") and refers to the fact that it is stored in phosphate-containing sediments. The only known species is Phosphatherium ''escuilliei''. The species name ''escuilliei'' honors the person who found the type fossils, François Escuillié. The first description was largely limited to the tooth features, a more extensive template of the then known find material was only published two years later.
The first fossil finds were discovered in the north-eastern part of the Ouled Abdoun Basin
The Oulad Abdoun Basin (also known as the Ouled Abdoun Basin or Khouribga Basin) is a phosphate sedimentary basin located in Morocco, near the city of Khouribga. It is the largest in Morocco, comprising 44% of Morocco's phosphate reserves, and a ...
in a phosphate-containing layer. However, they only comprised two fragmented upper jaws. However, the exact location of this find was not known. Further and much more extensive finds were discovered in the early 2000s in the same basin in the ''Grand Daoui'' area. This consists of numerous skull fragments, mandibles and some limb elements.Eritherium'' and ''Daouitherium
''Daouitherium'' ("Sidi Daoui beast" from the name of the site where it was discovered) is an extinct genus of early proboscideans (a group including modern elephants and their extinct relatives) that lived during the early Eocene (Ypresian sta ...
''.
Taxonomy
''Phosphatherium'' is known primarily from twomaxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...
fragments dated to the latest Paleocene deposits of the Ouled Abdoun Basin, Morocco
Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...
, which date from the Thanetian
The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age ( ...
epoch. It is one of the oldest and smallest members of the Proboscidea, with an estimated shoulder height of about and body mass of . Like its later relative, ''Moeritherium
''Moeritherium'' ("the beast from Lake Moeris") is an extinct genus of primitive proboscideans. These prehistoric mammals are related to the elephant and, more distantly, sea cows and hyraxes. They lived during the Eocene epoch.
Description
''M ...
'', the animal was probably an amphibious browser that fed on aquatic plants, akin to a very small tapir
Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inh ...
. Both animals are included in the family Numidotheriidae
Numidotheriidae is an extinct family of primitive proboscidean that lived from the late Paleocene to the early Oligocene periods of North Africa.
Fragmentary fossils (mainly teeth) of the early Eocene genera, ''Daouitherium'' and ''Phosphatheri ...
, together with ''Numidotherium
''Numidotherium'' ("Numidia beast") is an extinct genus of early proboscideans, discovered in 1984, that lived during the middle Eocene of North Africa some 46 million years ago. It was about 90-100 cm tall at the shoulder and weighed about 250- ...
''.
Below is a phylogenetic tree based on Tabuce ''et al''. 2019.Palaeobiology
''Phosphatherium'' is thought to have had a broad diet. The dental microwear Dental microwear analysis is a method to infer diet and behavior in extinct animals, especially in fossil specimens. Typically, the patterns of pits and scratches on the occlusal or buccal surface of the enamel are compared with patterns observed ...
patterns observed on their teeth show lengthy scratches on the molars of juveniles. Correspondingly, similar patterns are found on adult individuals. Through study of the wear and specifically scratches on the teeth of ''Phosphatherium'', the food items it ingested include shrubs and bushes, indicating a mixed feeding preference. Adult molars are found to have a much higher density of scratches, indicating abrasive food sources and possibly insects and small animals. Overall, ''Phosphatherium'' is thought to be an omnivorous browser mainly determined by its preferences, as well as the availability of resources.
Considering its highly adapted folivorous jaw and tooth structure, ''Phosphatherium'' provides evidence of the high age of African endemism
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
. The dental structure of ''Phosphatherium'' suggests its diet consisted mainly of leaves, which indicates it may have fulfilled a niche role in its environment, although diet can only be inferred. The discovery of this animal has ultimately helped reinforce the African origin of proboscideans, and provide insight into the radiation of modern orders of placental
Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...
mammals.
References
* http://mygeologypage.ucdavis.edu/cowen/historyoflife/Phosphatherium.html {{Taxonbar, from=Q134951 Paleocene proboscideans Eocene proboscideans Ypresian extinctions Transitional fossils Paleocene mammals of Africa Eocene mammals of Africa Prehistoric placental genera Prehistoric monotypic mammal genera Fossil taxa described in 1996