Phiomia
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''Phiomia'' (after the
Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
''phiom'' "lake", an ancient name for the Fayum), is an extinct genus of basal elephantiform
proboscidean Proboscidea (; , ) is 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. Three liv ...
that lived in what is now Northern
Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
during the Late
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
to Early
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
some 37–30 million years ago. The
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
of ''Phiomia'', part of the mandible (lower jaw), was described in 1902 by Charles William Andrews and Hugh John Llewellyn. Unsure of its identity, they assigned it, tentatively, to the obsolete order
Creodonta Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ance ...
. Subsequently, it was recognised as a proboscidean. Briefly it was treated as a
junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...
of ''Palaeomastodon'', but the two are regarded as separate genera. Though five species have been assigned to ''Phiomia'' over the years, only two, ''P. serridens'' (the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
) and ''P. major'', are currently recognised. ''Phiomia'' was fairly small in terms of body size, with an estimated shoulder height in the case of ''P. serridens''. In some regards it resembled ''Palaeomastodon'', though was less basal and bore similarities to
gomphotheres Gomphotheres are an extinct group of proboscideans related to modern Elephant, elephants. First appearing in Africa during the Oligocene, they dispersed into Eurasia and North America during the Miocene and arrived in South America during the Ple ...
, to the point where it was briefly considered their ancestor. A retracted naris (nasal cavity) with strong muscle attachment sites, long snout and protruding mandible all suggest that ''Phiomia'' was among the first proboscideans to possess a true trunk. Both the upper jaw and mandibles were tusked, with those of the upper jaw being thin, recurved and blade-like, while those of the mandibles were flat, straight and broad.


Taxonomy


Early history

The
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
of ''Phiomia'', a partial left
mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...
(lower jaw), was recovered from strata belonging to the
Jebel Qatrani Formation The Jebel Qatrani Formation (also Gebel Qatrani, Gabal Qatrani or Djebel Qatrani) is a geologic formation located in the Faiyum Governorate of central Egypt. It is exposed between the Jebel Qatrani escarpment and the Qasr el Sagha escarpment, nor ...
, part of the Eocene-age Fayum fossil deposits of Egypt. In 1902, the mandible was described by Charles William Andrews and Hugh John Llewellyn Beadnell, as part of a paper naming several mammal genera from the Fayum. They assigned to it the
binomial name In taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, altho ...
of ''Phiomia serridens'', after the locality of its discovery (the name "Fayum" derives from the Greek ''phiom'', meaning "lake") and its serrated lower
incisors 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 ...
. Andrews and Beadnell were uncertain of ''Phiomia'''s relationships, though, believing it to have been carnivorous, tentatively suggested that it was a highly specialised member of the now-disused
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
Creodonta Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ance ...
. Following a review by Max Schlosser, in 1906, Andrews re-examined ''P. serridens'', and suggested a closer relationship to '' Palaeomastodon'', an early
proboscidean Proboscidea (; , ) is 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. Three liv ...
. He tentatively suggested that it may have represented a smaller species of that genus, or that it belonged, at the very least, to the same family, Palaeomastodontidae. In 1908, Andrews wrote a paper on ''Palaeomastodon''. By that point, he had become unconvinced that ''Phiomia'' could be reliably separated from it, and suggested due to its small body size that its holotype belonged to the same taxon as ''Palaeomastodon minor''. Thus, he formally synonymised the two.


Validity and internal systematics

The proposed synonymy between ''Phiomia'' and ''Palaeomastodon'' lasted only fourteen years. In 1922, Matsumoto Hikoshichirō once again separated the two, based on various characteristics of the skull and teeth. Notably, the morphology of the two genera's
cheek teeth Cheek teeth or postcanines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many folds or tubercles). Mammals have multicuspidate molars (three in placentals, four in marsupials, in each jaw quadrant) and ...
(the premolars and
molars The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...
) were different, with those of ''Palaeomastodon'' being bunolophodont (having inner cusps that are blunt cones, and outer cusps modified into ridges) and those of ''Phiomia'' being conventionally bunodont. Furthermore, based on a second mandible from the Jebel Qatrani, Matsumoto described a second ''Phiomia'' species, ''P. osborni'', and reassigned two species of ''Palaeomastodon'', thus adding ''P. minor'' and ''P. wintoni'' to ''Phiomia''. An additional ''Phiomia'' species, ''P. major'', was described in 2004 by William J. Sanders, John Kappelman, and D. Tab Rasmussen, based on teeth from the Chilga district of Ethiopia. In the paper describing it, the authors synonymised all of Matsumoto's taxa with ''P. serridens'', thus reducing ''Phiomia'' to just two species. Subsequent authors have maintained this synonymy.


Classification

Since its reclassification as a proboscidean, ''Phiomia'' has always been regarded as a fairly basal member of the order. Henry Fairfield Osborn believed that it was an early member of a long-jawed mastodont lineage, and that it was directly ancestral to ''Trilophodon'' (now a synonym of ''
Gomphotherium ''Gomphotherium'' (; "nail beast" for its double set of straight tusks) is an extinct genus of gomphothere proboscidean from the Neogene of Eurasia, Africa and North America. It is the most diverse genus of gompothere, with over a dozen valid sp ...
''). In Pascal Tassy's 1988 paper on the phylogeny of proboscideans, wherein he erected the
suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...
Elephantiformes, he classified ''Phiomia'' as a basal member of the group, intermediate between ''Palaeomastodon'' and the later '' Hemimastodon''. In 1992, the family Phiomiidae was erected to encompass ''Phiomia''. A phylogenetic analysis of basal proboscideans was performed by Lionel Hautier et al. (2021), which recovered ''Phiomia'' in a similar position. Below is a cladogram depicting the results of Hautier et al. (2021):


Description

''Phiomia serridens'' is estimated to have had a shoulder height of . ''P. major'' seems to have been larger, though by how much is uncertain due to its nature as a taxon known solely from teeth.


Skull and dentition

The skull of ''Phiomia'' is similar to that of ''Palaeomastodon''. It was fairly long in comparison to its width, more so than in that genus, though not to the extent of gomphotheres like ''Gomphotherium'' and '' Megabelodon''. The naris (nasal cavity) was retracted, to the extent where its topped just before the orbits. That it is surrounded by strong muscle attachment sites suggests the presence of a small trunk. ''Phiomia'''s
palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...
was fairly narrow, while that of ''Palaeomastodon'' was wider. The
symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...
of the mandible was very elongated, though again, not to the extent of the aforementioned gomphotheres; both genera were among the first proboscideans to meaningfully elongate the mandibular symphysis and tusks. Like ''Palaeomastodon'', ''Phiomia'' had a high
occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lobes of the ...
with a large nuchal crest, possibly to counterbalance the weight of the tusks, elongated mandible, and trunk. ''Phiomia'' had a
dental formula Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...
of . On both the lower and upper jaws, the
incisors 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 ...
had been modified into tusks. The upper tusks curved downwards, and were thin and blade-like, while the lower tusks were straight and flat, with rounded edges. Most of the premolars were brachydont (short-cusped), though the last premolar was like the molars in being long, narrow and bunodont. This is unlike the condition in ''Palaeomastodon'', whose teeth were bunolophodont. All of the cheek teeth bear a trefoil
cusp A cusp is the most pointed end of a curve. It often refers to cusp (anatomy), a pointed structure on a tooth. Cusp or CUSP may also refer to: Mathematics * Cusp (singularity), a singular point of a curve * Cusp catastrophe, a branch of bifu ...
pattern, unlike more basal proboscideans but like gomphotheres. ''Phiomia'''s cheek teeth are also shorter than those of ''Palaeomastodon''.


Palaeoenvironment

The environment of the Jebel Qatrani Formation, from which ''Phiomia serridens'' originates, has been described as a
subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...
to
tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
lowland plain by Bown, who further suggests the presence of streams and ponds. Based on the occurrence of birds that are associated with water (such as ospreys, early flamingos, jacanas, herons,
storks Storks are large, long-legged, long-necked wading birds with long, stout Beak, bills. They belong to the family (biology), family Ciconiidae, and make up the order Ciconiiformes . Ciconiiformes previously included a number of other families, suc ...
, cormorants and shoebills), Rasmussen and colleagues inferred that the environment featured slow-moving freshwater with a substantial amount of aquatic vegetation, which matches the prior hypothesis. Although
lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...
suggests that most fossils were deposited on sandbanks after being transported by currents, the authors argue that
swamps A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
could have easily formed along the banks of the river that was present during the Oligocene and may account for the mudstone found in certain quarries. They furthermore suggest that the fossil birds of Fayum, due to their affinities with modern groups, should be considered a more valuable indicator of the environment when compared with the fossil mammals, many of which belonged to families lacking modern examples. The absence of other birds typical for such an environment may be explained either through sampling bias or due to the fact that said groups had simply not yet been present in Oligocene Africa. Generally, Rasmussen and colleagues compare the environment of Jebel Qatrani to freshwater habitats in modern Central Africa. The discovery of snakehead fossils seem to support Rasmussen's interpretation, as the genus ''Parachanna'' today prefers slow-moving backwaters with plenty of vegetation. Other fish present meanwhile, notably ''Tylochromis'', suggest that deep, open water was likewise present. The river channels may have been overgrown with reeds,
papyrus Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, ''Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'' or ''papyruses'') can a ...
and featured floating vegetation like water lilies and ''
Salvinia ''Salvinia'' or watermosses is a genus of free-floating aquatic ferns in the family Salviniaceae. The genus is named in honor of 17th-century Italian naturalist Anton Maria Salvini, and the generic name was first published in 1754 by French bo ...
''. In a 2001 paper Rasmussen et al''.'' argued that the sandstone and mudstone of the formation likely formed as sediments were aggraded by a system of river channels that emptied towards the west into the Tethys. Here they reconstructed the environment as a tropical lowland swamp forest intermingled with marshes. They furthermore suggest that the environment would have experienced
monsoons A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
. Overall this indicates that this region was a part of an extensive belt of tropical forest that stretched across what is now northern Africa, which would gradually give rise to open woodland and even steppe the further one was to travel inland.


Notes


References

{{Taxonbar, from=Q134407 Elephantiformes Prehistoric placental genera Oligocene mammals of Africa Eocene proboscideans Oligocene proboscideans Priabonian genus first appearances Rupelian genus extinctions Fossil taxa described in 1902 Eocene mammals of Africa