''Phosphatherium escuillei'' is a basal
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.
![Phosphatherium skull 1996](https://upload.wikimedia.org/wikipedia/commons/5/59/Phosphatherium_skull_1996.jpg)
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'''s teeth and jaw structures also show noticeable variation, which is related to 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 ...]
(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
behind the first premolar. The premolars as a whole were quite simply built and not very molarised, i.e. they hardly resembled the
. These had a bilophodont structure with two clearly formed transverse
. The rearmost molar of the mandible, however, had a third enamel bar. In general, the teeth were
.