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{{Short description|Extinct genus of carnivorans}}
{{good article}}
{{Automatic taxobox
| fossil_range = Late [[Miocene]] to Early [[Pleistocene]], {{fossilrange|10.1|2}}
| image = Enhydriodon hendeyi africanus dentition.jpg
| image_caption = Lower jaw dentitions of ''Enhydriodon hendeyi'' (A-C) and ''Enhydriodon africanus'' (D-F)
| taxon = Enhydriodon
| authority = [[Hugh Falconer|Falconer]], 1868
|display_parents = 2
| type_species = {{extinct}}'''''Enhydriodon sivalensis'''''
| type_species_authority = Falconer, 1868
| subdivision_ranks = Other species
| subdivision = {{species list
|{{extinct}} '''''E. kamuhangirei'''''|Morales & Pickford, 2005
|{{extinct}} '''''E? soriae'''''|Morales & Pickford, 2005
|{{extinct}} '''''E. dikikae'''''|Geraads, Alemseged, Bobe & Reed, 2011
|{{extinct}} '''''E. afman'''''|Werdelin & Lewis, 2013
|{{extinct}} '''''E. omoensis'''''|Grohé, Uno, & Boisserie, 2022
}}
| synonyms = {{collapsible list|bullets = true|title=<small>Genus synonymy</small>
| ''Amyxodon'' <small>Falconer & [[Proby Cautley|Cautley]], 1835</small>
}}
{{collapsible list|bullets = true
|title=<small>Synonyms of ''E. sivalensis''</small>
| ''Amyxodon sivalensis'' <small>Falconer & Cautley, 1835</small>
}}
{{collapsible list|bullets = true
|title=<small>Synonyms of ''E. ekecaman''</small>
| ''E. pattersoni'' <small>[[R. J. G. Savage|Savage]], 1978</small>
}}
}}
'''''Enhydriodon''''' is an [[extinct]] [[genus]] of [[mustelids]] known from [[Africa]], [[Pakistan]], and [[India]] that lived from the late [[Miocene]] to the early [[Pleistocene]]. It contains nine confirmed [[species]], two debated species, and at least a few other undescribed species from Africa. The genus belongs to the tribe [[Enhydriodontini]] (which also contains ''[[Sivaonyx]]'' and ''[[Vishnuonyx]]'') in the otter [[subfamily]] [[Lutrinae]]. Enhydriodon means "otter tooth" in [[Ancient Greek]] and is a reference to its dentition rather than to the ''[[Enhydra]]'' genus, which includes the modern [[sea otter]] and its two prehistoric relatives.
The exact sizes and lengths of ''Enhydriodon'' species are unknown given the lack of complete [[fossils]] of it and most related fossil lutrines. Indian subcontinental species are estimated to be of weights similar to that of the extant [[sea otter]], but African species are estimated to be heavier than extant lutrines. In particular, several species such as ''E. kamuhangirei'', ''E. dikikae'', and ''E. omoensis'' were estimated to weigh over {{cvt|100|kg}}. Given these weight estimates, the three species likely reached sizes comparable to extant [[bear]]s or [[lion]]s, making them the largest known mustelids to exist, although a lack of complete specimens makes precise estimates impossible.
Its advanced dentition is well-known, its broad, [[bunodont]] [[carnassials]] allowing the lutrine to consume prey by crushing them rather than shearing them like the modern sea otter and unlike most other extant otters. As such, it is grouped among the bunodont otters, a categorical term referring to fossil lutrines with non-bladelike carnassials in the [[premolars]] or [[molars]] of the Miocene to Pleistocene and the sea otter of the sole extant ''Enhydra'' genus. Its I<sup>3</sup> teeth (or third [[incisors]]) are [[canine tooth|canine-like]] and much larger than its other incisors (although shorter than its canines), a trait not seen in extant and extinct lutrine genera. It is hypothesized that Indian species of ''Enhydriodon'' were semiaquatic and consumed [[bivalves]] because their bunodont dentitions would have allowed them to consume hard-shelled invertebrates. It is unknown whether African species were generally aquatic, semiaquatic, or terrestrial, but their potential diets suitable for bunodont dentitions include bivalves, [[catfish]], reptiles, eggs, and carrion. ''E. omoensis'' of [[Ethiopia]] in particular could have been a terrestrial locomotor that at least semiregularly hunted or scavenged terrestrial prey with [[C4 carbon fixation|C<sub>4</sub>]] plant diets which if true makes its behaviour unlike any extant otters. It is unknown whether the species is an outlier amongst African bunodont otter species, but it has been suggested that ''Enhydriodon dikikae'' and ''Sivaonyx beyi'' were both large terrestrial bunodont otters of Africa as well.
The taxonomic status of ''Enhydriodon'' species have been complicated by its affinities and similarities with other bunodont lutrine genera like ''Sivaonyx'' and ''[[Paludolutra]]'' up to the modern day, although ''Paludolutra'' is presently considered a distinct genus not closely related to ''Enhydriodon''. Currently, the Enhydriodontini tribe is considered evolutionarily closer to the modern ''Enhydra'' genus than any other known bunodont otter genus that may have gained bunodont dentition as a result of [[parallel evolution]], but the extent to which they are closely related remains unresolved.
==Taxonomy==
=== Early history ===
[[Image:Enhydriodon Sivalensis Sketch Cranium.png|thumb|left|1868 Illustrations of the 2 crania of ''E. sivalensis'' (Figure 3-4 are different views of the same specimen). The drawings were based on specimens at the [[British Museum]].]]
''Enhydriodon'' was first erected in 1868 by [[Hugh Falconer]] based on several crania from [[Siwalik Hills]], India that he attributed to ''E. sivalensis''.<ref name="Siva">{{cite book|author = [[Hugh Falconer]] |year = 1868 |title = Palæontological Memoirs and Notes of the Late Hugh Falconer: Fauna Antiqua Sivalensis |publisher = R. Hardwicke |location = United Kingdom |isbn=112-0-015839|url=https://books.google.com/books?id=hb4wAQAAMAAJ&pg=PA334-IA2}}</ref><ref name="India">{{cite journal |first1=B.C. |last1=Verma |last2=Gupta |first2=S.S. |title=Enhydriodon sivalensis, a giant fossil otter from the Saketi Formation (Upper Pliocene), Siwalik group, Sirmur district, Himachal Pradesh |journal=Journal of the Palaeontological Society of India |date=1992 |volume=37 |pages=31–36}}</ref> He explained that the scientific name, meaning "otter tooth", is derived from the [[Ancient Greek]] terms ἐνυδρίς (otter) and ὀδούς (tooth) and is not a reference to the genus ''[[Enhydra]]'', which includes the modern [[sea otter]] (''Enhydra lutris''). According to Falconer, the Siwalik Hill fossils belonging to ''E. sivalensis'' were previously classified by Falconer and [[Proby Cautley]] under the genus and species name ''Amyxodon sivalensis'' in an 1835 synopsis of the fossil genera in the Siwalik Hills that the two palaeontologists found, in which the fossil taxon was considered to be a [[carnivoran]] of an unknown [[family (taxonomy)|family]], although no [[holotype]] or diagnostic descriptions were attributed to it. As a result of the rename, ''Amyxodon'' had been considered a "[[nomen nudum|dead name]]" or synonym of ''Enhydriodon'' despite being the older genus name. Using the available specimens of ''E. sivalensis'', Falconer calculated that there were four [[premolar]]s and [[molar (tooth)|molars]] in the species's upper jaw (the [[dentition|dental formula]] was calculated as {{DentalFormula|upper=3.1.4|lower=2.1.5}}), one less than in the extant genus ''[[Lutra]]'' but matching the total count of ''Enhydra''. He described the upper [[carnassial]] of ''E. sivalensis'' as the most unique feature of its upper jaw, being nearly square and its coronal lobes being developed from conical [[mamelon (dentistry)|mamelons]] unlike the two extant lutrine genera.<ref name="Siva"/><ref>{{cite journal|last1=Cautley|first1=Proby Thomas|last2=Falconer|first2=Hugh|year=1835|title=Synopsis of Fossil Genera and Species from the upper deposits of the tertiary strata of the Sivalik Hills, in the collection of the authors.|journal=Journal of the Asiatic Society of Bengal|volume=4|issue=12}}</ref>
During the 19th and 20th centuries, more species of ''Enhydriodon'' such as ''E. campanii'' were introduced and more lutrine genera with [[bunodont]] dentition such as ''[[Sivaonyx]]'' and ''[[Vishnuonyx]]'' were described, creating a particularly complicated history for the earliest-described prehistoric otter genus. In 1931, [[Guy Ellcock Pilgrim|Guy Pilgrim]] described more fossils discovered in the Siwalik Hills, including a newer species named ''E. falconeri''. He also implied that ''Enhydriodon'' and ''Sivaonyx'', despite their similarities, were differentiated by the structure of the maxillary 4th premolar (P<sup>4</sup>) and apparent lack of the anterior upper premolar (P<sup>1</sup>) that is presumed to be reflected at the bottom jaw as well (both of which are debated up to today).<ref name="Falconeri">{{cite book|author = [[Guy Ellcock Pilgrim|Guy E. Pilgrim]] |year = 1932 |title = The Fossil Carnivora of India |publisher = Palaeontologia Indica |location = India |pages=80–88}}</ref> In the same year that ''E. falconeri'' was described, [[Ernst Stromer]] described ''E. africanus'' of the late [[Pliocene]], its fossil teeth being located in [[South Africa]] and the first described species from the continent of Africa.<ref name="Lutrinae">{{cite journal|last=Willemsen|first=Gerard F.|year=1992|title=A revision of the Pliocene and Quaternary Lutrinae from Europe|journal=Scripta Geologica|volume=101|pages=89–94}}</ref>
=== Perceived relationships with ''Paludolutra'' and ''Enhydra'' ===
In 1976, [[Charles Repenning]] brought about the idea that ''Enhydriodon'' was related to the extant ''Enhydra'' genus due to the supposed species of the former being an evolutionary "branch" of "crab-eating otters" in Italy, Spain, and California, eventually leading to the modern sea otter.<ref>{{cite journal|last=Repenning|first=Charles A.|year=1976|title=Enhydra and Enhydriodon From The Pacific Coast of North America|journal=Journal of Research of the U.S. Geological Survey.|volume=4|issue=3|pages=305–315}}</ref> He correctly introduced the idea that ''Enhydra'' was related to ''Enhydriodon'' given their bunodont dentitions, but the supposed European "branch" of the ''Enhydriodon'' genus was later reclassified by Johannes Hürzeler and Burkart Engesser into the newer genus ''[[Paludolutra]]'' in 1976, although it remained relatively obscure in the palaeontological record until later research revised its taxonomic state.<ref>{{cite journal|last1=Hürzeler|first1=Johannes|last2=Engesser|first2=Burkart|year=1976|title=Les faunes de mammifères néogènes du Bassin de Baccinello (Grosseto, Italie)|language=French|journal=Comptes Rendus de l'Académie des Sciences de Paris|volume=283|pages=333–336}}</ref><ref name ="Enhydriodontini">{{cite journal|last1=Morales|first1=Jorge|last2=Pickford|first2=Martin|year=2005|title=Giant bunodont Lutrinae from the Mio-Pliocene of Kenya and Uganda|journal=Estudios Geológicos|language=Spanish|volume=61|issue=3|pages=233–245|doi=10.3989/egeol.05613-666|doi-access=free}}</ref>
The taxonomies of individual lutrine species and genera continued to be revised into the 21st century as more prehistoric otter species were described while palaeontologists continually revised the fossil bunodont lutrine species to different genera. ''Paludolutra'' was originally reclassified as a [[subgenus]] of ''Enhydriodon'' by Gerard F. Willemsen in 1992.<ref name="Lutrinae"/> However, in January 2005, [[Martin Pickford]] and colleagues diagnosed ''Paludolutra'' as a synonym of ''Sivaonyx'' on the basis of Pilgrim's diagnosis of the latter, rejecting Willemsen's synonymy of ''Paludolutra'' to ''Enhydriodon''. Additionally, they erected a species of ''Enhydriodon'' named ''E. hendeyi'' from the type locality of [[Langebaanweg]], South Africa, which dates to the lower Pliocene and was named after the palaeontologist Quinton B. Hendey, who they said described the first known specimens that were since attributed to the species.<ref>{{cite journal|last1=Pickford|first1=Martin|last2=Soria|first2=Dolore|last3=Morales|first3=Jorge|year=2005|title=Carnivores from the Late Miocene and Basal Pliocene of the Tugen Hills, Kenya|journal=Revista de la Sociedad Geológica de España|volume=18|issue=1–2|pages=39–61}}</ref> In December of the same year, Jorge Morales and Pickford instead described ''Paludolutra'' as a distinct genus that might be related to ''Sivaonyx'' based on dentition convergences.<ref name ="Enhydriodontini"/> In 2007, the two palaeontologists reaffirmed that the dental [[morphology (biology)|morphology]] of ''Paludolutra'' was distinct enough to be reclassified as a genus based on full generic differentiation, suggesting that the species ''P. campanii'', ''P. lluecai'', and ''P. maremmana'' would no longer be classified under ''Enhydriodon'' under the basis of ''Paludolutra'' being a subgenus.<ref name="Pickford">{{cite journal|last=Pickford|first=Martin|year=2007|title=Revision of the Mio-Pliocene bunodont otter-like mammals of the Indian Subcontinent|language=Spanish|journal=Estudios Geológicos|volume=63|issue=2|pages=108–124|doi=10.3989/egeol.07631192}}</ref><ref name="Siamo">{{cite journal|last1=Wang|first1=Xiaoming|last2=Grohé|first2=Camille|last3=Su|first3=Denise F.|last4=White|first4=Stuart C.|last5=Ji|first5=Xueping|last6=Kelley|first6=Jay|last7=Jablonski|first7=Nina G.|last8=Deng|first8=Tao|last9=You|first9=Youshan|last10=Yang|first10=Xin|year=2017|title=A new otter of giant size, Siamogale melilutra sp. nov. (Lutrinae: Mustelidae: Carnivora), from the latest Miocene Shuitangba site in north-eastern Yunnan, south-western China, and a total-evidence phylogeny of lutrines|journal=Journal of Systematic Palaeontology|volume=16|issue=1|pages=1–24|doi=10.1080/14772019.2016.1267666|bibcode=2018JSPal..16...39W |s2cid=58892181 |url=https://escholarship.org/uc/item/11b1d0h9 }}</ref>
=== Modern revisions of African species ===
[[File:Enhydriodon Omoensis Femur Views.png|thumb|''E. omoensis'' right femur faced at different sides]]
In 2003, [[Lars Werdelin]] erected the species ''E. ekecaman'' from the [[Kanapoi]] palaeontological site of the [[Turkana Basin]] in Kenya (early Pliocene, ca. 5.2-4.0 Ma), describing it as one of the earliest members of the African ''Enhydriodon'' lineage. The species was named after the [[Turkana language]] term "ekecaman", which means "fisherman" because he suggested that fish may have been a diet for the species. He also declared the species "''E. pattersoni'' ", described by [[R. J. G. Savage]] in 1978, as a [[nomen nudum]] of ''E. ekecaman'' since no type specimen or valid diagnosis was designated to it, a view supported by Morales and Pickford in December 2005.<ref>{{cite journal|last=Werdelin|first=Lars|year=2003|title=Carnivores from the Kanapoi Hominid site, Turkana Basin, northern Kenya|journal=Contributions in Science|volume=498|pages=115–132|doi=10.5962/p.214388 |s2cid=82943977 |doi-access=free}}</ref><ref name ="Enhydriodontini"/>
''E. africanus'', ''E. ekecaman'', and ''E. hendeyi'' were reclassified into ''Sivaonyx'' by Pickford and Morales in December 2005, where they additionally described a new species named ''Sivaonyx kamuhangirei''.<ref name ="Enhydriodontini"/> The reclassification of African fossil bunodont otters into ''Sivaonyx'' had brought about continuous debate regarding the practicality of the differences between ''Enhydriodon'' and ''Sivaonyx'', with some researchers claiming neutrality due to preferred focuses on researching the individual species instead of their genus placements. In 2022, the four species were eventually reclassified into ''Enhydriodon'' in a research paper by Camille Grohé et al. ''E. soriae'' was also initially sorted unto ''Sivaonyx'' but was eventually assigned to ''Enhydriodon'', although its genus placement remains disputed.<ref name="giantmustelid">{{cite journal|last1=Valenciano|first1=Alberto|last2=Govender|first2=Romala|year=2020|title=New insights into the giant mustelids (Mammalia, Carnivora, Mustelidae) from Langebaanweg fossil site (West Coast Fossil Park, South Africa, early Pliocene)|journal=PeerJ|volume=8 |pages=e9221 |doi=10.7717/peerj.9221|pmid=32547866|pmc=7271888 |doi-access=free }}</ref><ref name="Omoe">{{cite journal|last1=Grohé|first1=Camille|last2=Uno|first2=Kevin|last3=Boisserie|first3=Jean-Renaud|year=2022|title=Lutrinae Bonaparte, 1838 (Carnivora, Mustelidae) from the Plio-Pleistocene of the Lower Omo Valley, southwestern Ethiopia: systematics and new insights into the paleoecology and paleobiogeography of the Turkana otters|language=French|journal=Comptes Rendus Palevol|volume=30|issue=30 |pages=684–693|doi=10.5852/cr-palevol2022v21a30|s2cid=252106648 |doi-access=free}}</ref> In 2005, Morales and Pickford sorted ''Enhydriodon'' into the newly created [[Enhydriodontini]] tribe, which they described as hosting genera of extinct bunodont otters from the Siwalik Hills and Africa including ''Vishnuonyx'', ''Sivaonyx'', and ''Paludolutra''. In 2007, Pickford synonymized the species "''E. aethiopicus'' ", previously described by Denis Geraads et al. in 2004, to ''Pseudocivetta ingens'', an extinct member of the [[Viverridae]] family.<ref name="Pickford"/> In 2017, ''Enhydra'' was explicitly excluded from the Enhydriodontini tribe despite its similarities, and ''Paludolutra'' was reclassified as a sister taxon to the tribe.<ref name ="Enhydriodontini"/><ref name="Siamo"/>
In 2011, Denis Geraads and colleagues described ''E. dikikae'' based on its remains of a partial skull and femurs in the Lower Awash of [[Dikika]], Ethiopia, the locality dating to the middle Pliocene. It was described as having a notably heavier skull (albeit broken) than other ''Enhydriodon'' species or the modern sea otter. The species named was based directly on the site of Dikika.<ref name="Dikikae">{{cite journal|doi=10.1080/02724634.2011.550356 | volume=31 | title=Enhydriodon dikikae, sp. nov. (Carnivora: Mammalia), a gigantic otter from the Pliocene of Dikika, Lower Awash, Ethiopia | journal=Journal of Vertebrate Paleontology | year=2011 | pages=447–453| last1=Geraads | first1=Denis | last2=Alemseged | first2=Zeresenay | last3=Bobe | first3=René | last4=Reed | first4=Denné | issue=2 | bibcode=2011JVPal..31..447G | s2cid=84797296 }}</ref> It was deemed as the largest species of ''Enhydriodon'' until another species also from Ethiopia, ''E. omoensis'', was described from the Lower Omo Valley in 2022, dating from the late Pliocene up to the Plio-[[Pleistocene]] boundary. Similar to ''E. dikikae'', the species name was derived directly from the site in which it was recovered.<ref name="Omoe"/> In a September 2022 conference by Alberto Valenciano, Morales, and Pickford (the same month as the research paper on ''E. omoensis''), however, they referred to certain lutrine species previously reclassified to ''Enhydriodon'' as ''Sivaonyx'', namely ''S. hendeyi'' and ''S. africana''.<ref>{{cite conference|last1=Valenciano|first1=Alberto|last2=Morales|first2=Jorge|last3=Pickford|first3=Martin|year=2022|title="Lutra" libyca from the Mio/Pliocene of Wadi Natrun (Egypt): a new systematics proposal|conference=The 2nd International Symposium on Vertebrate Paleontology 20th-22nd September 2022|pages=31–32|url=https://www.researchgate.net/publication/364210301}}</ref>
===Classification===
[[File:Adult Sea Otter in Morro Bay.jpg|thumb|''Enhydriodon's'' closest extant relative, the [[sea otter]]. It is the only extant bunodont otter.]] ''Enhydriodon'' belongs to the tribe Enhydriodontini in the subfamily [[Lutrinae]], which first appeared in Eurasia and Africa during the late [[Miocene]] epoch.<ref name ="Enhydriodontini"/> It is perhaps the most well-known prehistoric otter given its old taxonomic history and it being a primary source of comparisons to other bunodont otter genera. It is generally thought that ''Enhydriodon'' was a result of a Miocene-Pleistocene trend that gave prehistoric lutrines bunodont teeth and large sizes compared to their extant relatives. It is classified as a member of the bunodont otters group, a categorical term commonly used by researchers that also includes ''Sivaonyx'', ''Paludolutra'', ''Vishnuonyx'', ''[[Torolutra]]'', ''[[Enhydritherium]]'', ''[[Djourabus]]'', ''[[Paralutra]]'', ''[[Tyrrhenolutra]]'', ''[[Siamogale]]'' and ''Enhydra''.<ref name="Siamo"/><ref name="Vishnuonyx">{{cite journal|last1=Kargopoulos|first1=Nikolaos|last2=Valenciano|first2=Alberto|last3=Kampouridis|first3=Panagiotis|last4=Lechner|first4=Thomas|last5=Böhme|first5=Madelaine|year=2021|title=New early late Miocene species of Vishnuonyx (Carnivora, Lutrinae) from the hominid locality of Hammerschmiede, Bavaria, Germany|journal=Journal of Vertebrate Paleontology|volume=41|issue=3|doi=10.1080/02724634.2021.1948858|bibcode=2021JVPal..41E8858K |s2cid=240538139 }}</ref><ref>{{cite web|title=Enhydritherium terraenovae|date=30 March 2017 |url=https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/enhydritherium-terraenovae/|publisher=Florida Museum of Natural History|accessdate=10 October 2022|language=en}}</ref> Bunodont otters are defined as large to very large mustelids of North America, Eurasia, and Africa that had robust dentition compared to most of the extant otters, generally allowing them to prey upon hard-armored creatures.{{efn|Bunodont dentition refers to molars with round rather than sharp cusps, features that the sea otter and extinct lutrine relatives ("bunodont otters") have.<ref>{{cite journal|last1=Constantino|first1=Paul J.|last2=Lee|first2=James J.-W.|last3=Morris|first3=Dylan J.|last4=Lucas|first4=Peter W.|last5=Hartstone-Rose|first5=Adam|last6=Lee|first6=Wah-Keat|last7=Dominy|first7=Nathaniel J.|last8=Cunningham|first8=Andrew|last9=Wagner|first9=Mark|last10=Lawn|first10=Brian R.|year=2011|title=Adaptation to hard-object feeding in sea otters and hominins|journal=Journal of Human Evolution|volume=61|issue=1|pages=89–96|doi=10.1016/j.jhevol.2011.02.009|pmid=21474163 |bibcode=2011JHumE..61...89C }}</ref>}}<ref name="giantmustelid"/><ref name="Vishnuonyx"/> Despite sharing the feature of bunodont dentition, there are at least several clades of lutrines belonging to this category rather than one, so the term "bunodont otters" therefore is categorical rather than taxonomic and covers lutrines during the same periods with similar dentitions rather than one that directly defines their taxonomic state.<ref name="Siamo"/>
The following [[cladogram]] by Xiaoming Wang et al. in 2018 defines some of the following extant and extinct otter species and genera within the subfamily Lutrinae based on a 50% majority consensus (the bunodont otter genera are bolded beginning from "''Paralutra jaegeri''"):<ref name="Siamo"/>
{{clade| style=font-size:85%; line-height:85%
|label1=[[Lutrinae]]
|1={{clade
|1=''[[Pteronura brasiliensis]]'' (giant river otter)
|2={{clade
|1={{clade
|1=''[[Lontra canadensis]]'' (North American river otter)
|2=''[[Lontra felina]]'' (marine otter)
}}
|2={{clade
|1={{clade
|1=''[[Lutra lutra]]'' (Eurasian otter)
|2=''[[Aonyx capensis]]'' (African clawless otter)
}}
|2={{clade
|1={{clade
|1=†'''''[[Paralutra|Paralutra jaegeri]]'''''
|2={{clade
|1=†'''''[[Siamogale|Siamogale melilutra]]'''''
|2=†'''''[[Siamogale|Siamogale thailandica]]'''''
}}
}}
|2={{clade
|1={{clade
|1={{clade
|1='''''[[Enhydra lutris]]''''' (sea otter)
|2=†'''''Enhydriodon'''''
}}
|2={{clade
|1=†'''''[[Vishnuonyx]]'''''
|2=†'''''[[Sivaonyx]]'''''
}}
}}
|2={{clade
|1=†'''''[[Tyrrhenolutra|Tyrrhenolutra helbingi]]'''''
|2={{clade
|1=†'''''[[Paralutra|Paralutra garganensis]]'''''
|2={{clade
|1=†'''''[[Enhydritherium|Enhydritherium terranovae]]'''''
|2=†'''''[[Paludolutra]]'''''
}}
}}
}}
}}
}}
|3={{clade
|1=†'''''[[Lutra aonychoides]]'''''
}}
}}
}}
}}
}}
As shown in the above phylogeny, ''Enhydriodon'' shared a closer morphology with its other extinct relatives and ''Enhydra'' than the other extant lutrines that lack bunodont carnassial teeth (''Lutra aonychoides'' was described as not being related to ''Lutra''). Although the majority consensus tree displays a close morphological relation between ''Enhydriodon'' and ''Enhydra'', the authors of the consensus tree also created a [[Bayesian inference]] tree proposing that ''Enhydra'' as an isolated clade separate from typical members of Enhydriodontini ("''Paralutra''" ''jaegeri'' was proposed as an isolated clade from ''Siamogale'' as well). Regardless, they argued that ''Enhydra'' is closer to the clade composing of ''Enhydriodon'', ''Sivaonyx'', and ''Vishnuonyx'' than any other bunodont otter genus. The researchers explained that the acquisition of bunodont dentition occurred [[parallel evolution|at least three times]] in the evolution of lutrines, reflected by the phylogeny tree's clades: in ''Sivaonyx''-''Enhydriodon''-''Enhydra'', in ''Paludolutra''-''Enhydritherium'', and in ''Siamogale''.<ref name="Siamo"/> Non-bunodont otters likely branched out separately from bunodont otters during or before the Pliocene epoch, but their poor fossil records and restriction to Plio-Pleistocene deposits in comparison leave little understanding in their evolutionary phylogenies.<ref>{{cite journal|last1=Raghavan|first1=P.|last2=Pickford|first2=M.|last3=Patnaik|first3=R.|last4=Gayathri|first4=P.|year=2007|title=First fossil small-clawed otter, Amblonyx, with a note on some specimens of Lutra, from the Upper Siwaliks, India|journal=Estudios Geológicos|language=Spanish|volume=63|issue=2|pages=144–145|doi=10.3989/egeol.07632200|doi-access=free}}</ref>
==Description==
===Skull===
[[Image:Enhydra lutris 10zz.jpg|thumb|left|Skull of ''[[Enhydra lutris]]''. Its I<sup>3</sup>, while larger than its other incisors, is not hypertrophied in size unlike the ''Enhydriodon's'' I<sup>3</sup>.<ref name="Pickford"/>]]
There are currently only two known partial skulls that are attributed to ''Enhydriodon'': one of ''E. sivalensis'' of the Siwalik Hills and the other of ''E. dikikae'' of the Awash Valley. It is currently unknown whether the skulls' features of either species are well-representative of other species of ''Enhydriodon'', but the known ''E. dikikae'' and ''E. sivalensis'' skulls have somewhat different features from each other.<ref name="Dikikae"/>
The ''E. sivalensis'' skull, identified as belonging to a fully-grown individual, is relatively well-preserved with identifiable [[temporal bone|temporal crests]], [[frontal bones|frontal]], [[maxillae]], [[premaxillae]], [[nasal bones|nasal]], [[muzzle (anatomy)|muzzle]], and [[palatine bone]] parts. However, it has also suffered from wear and being slightly twisted clockwise. Most notably, the [[dental arch]] is complete, although the left M<sup>1</sup> and left I<sup>1</sup> are both missing and most of the teeth are broken from their crowns. It has a large brain case, a broad and short muzzle, and a large nasal opening. Outlines of the [[orbit (anatomy)|orbits]] around the skull's frontals can also be identified.<ref name="India"/>
The broken skull belonging to ''E. dikikae'' contains a short and [[prognathic|non-prognathic]] snout, parts of the orbits, a nearly complete upper dental arch that is missing both I<sup>1</sup>s and a right I<sup>2</sup>, and part of the lower jaw. The muzzle on the ''E. dikikae'' skull is short, a small anterior orbital border positioned just above the posterior side of the [[canine tooth|canine]]. The front part of the snout is identified as short, thereby comparable with the snout of ''Enhydra''. Although the evolution of bunodont otters like ''Enhydriodon'' is unclear, it is proposed that ''E. dikikae's'' short snout and very large canine size both clearly make the species different-looking and more [[apomorphy and synapomorphy|evolutionarily derived]] (or evolutionarily recent) than ''E. sivalensis''.<ref name="Dikikae"/>
===Dentition===
''Enhydriodon's'' dentition is well-defined by its extremely broad, bunodont carnassials in the molars and premolars similar to the modern sea otter. The ''Enhydriodon'' and ''Sivaonyx'' species differences are usually attributed to dentition, so the premolar teeth or molar teeth fossils are examined to discern the two bunodont otter genera. The generic differences (larger P<sup>4</sup> hypocone, conical post-protocone cusps, and apparent lack of anterior upper premolars for ''Enhydriodon'') by tooth measurements have been difficult to prove due to the fragmentary nature of the fossils and relative inconsistencies of tooth measurements/dimensions by species.<ref name="Pickford"/><ref name="Dikikae"/> The reclassification of all "African ''Sivaonyx''" species other than ''S. beyi'' to ''Enhydriodon'' in 2022 has been attributed to "[a] metaconid higher than the protoconid on M<sub>1</sub>, presence of a carnassial notch and one or more cusps between the protocone and the hypocone on P<sup>4</sup>, and/or distolingual expansion on M<sup>1</sup>."<ref name="Omoe"/>
''Enhydriodon'' as the latest-appearing genus is suggested to have the most bunodont dentition of the Enhydriodontini tribe, which includes the earliest-appearing ''Vishnuonyx'' and then ''Sivaonyx''. ''Enhydriodon's'' dentition suggests a near suppression of carnassial functions in favour of crushing as the predominant function. The I<sup>3</sup> (or third upper [[incisor]]) of ''Enhydriodon'' is much larger than its I<sup>1</sup> (smallest incisor) and I<sup>2</sup>, appearing larger and more canine-like in comparison to ''Paludolutra'' and ''Enhydra''. In comparison to other bunodont lutrine genera where the upper incisor is known, its third incisors are only marginally larger than their first and second incisors.<ref name="Pickford"/> The right I<sup>1</sup> of a skull of E. sivalensis, for instance, measures {{cvt|3|mm}} in anteroposterior diameter (APD) and {{cvt|4.5|mm}} in transverse diameter (TD). The skull's right I<sup>2</sup> measures {{cvt|5.2|mm}} in APD and {{cvt|5.5|mm}} in TD. In comparison, the right I<sup>3</sup> is the largest incisor of the holotype, with measurements of {{cvt|10.5|mm}} in APD and {{cvt|8|mm}} in TD (the canines are larger than the incisors, measuring {{cvt|17.1|mm}} in APD and {{cvt|13.8|mm}} in TD).<ref name="India"/> The large I<sup>3</sup> trait also applies to ''E. dikikae'', which was described after Pickford's general description of the ''Enhydriodon'' genus as having a much larger I<sup>3</sup> than I<sup>1</sup> - I<sup>2</sup> and being more conical in shape. DIK-56's I<sup>3</sup> tooth measures {{cvt|12.4|mm}} in mesiodistal width (MD) and {{cvt|11.6|mm}} in buccolingual width (BL) compared to its I<sup>2</sup> measurements of {{cvt|5.5|mm}} in MD and {{cvt|9.7|mm}} in BL. Like ''E. sivalensis'', the I<sup>3</sup> is shorter than the canines, with C<sup>1</sup> measuring {{cvt|16.9|mm}} in MD plus {{cvt|15|mm}} in BL and C<sub>1</sub> measuring {{cvt|19.5|mm}} in MD and {{cvt|15.3|mm}} in BL.<ref name="Dikikae"/>
=== Limbs ===
[[File:Sivaonyx beyi Enhydriodon (Sivaonyx) hendeyi Aonyx capensis femora.jpg|thumb|Views of the left proximal [[epiphysis]] of the femur (A-B), complete left femur (C-D), and astragalus (H-I) of ''Enhydriodon hendeyi'' in comparison to a ''Sivaonyx beyi'' left femur (E) plus a left femur (F-G) and left astragalus (J-K) of the African clawless otter.]]
Postcranial remains of bunodont otters, including ''Enhydriodon'', are scarce, leaving too little information on the overall anatomies of many genera. The only known species of ''Enhydriodon'' with postcranial remains are ''E. hendeyi'', ''E. dikikae'', and ''E. omoensis''.<ref name="giantmustelid"/>
''E. hendeyi'' fossil remains include a fragmentary [[humerus]], an [[ulna]], two [[femurs]], and an [[Talus bone|astragalus]] (also known as a talus bone). The femora of ''E. hendeyi'' are smaller than those of ''S. beyi'' and ''E. dikikae'' but also larger than those of ''Enydritherium'', ''Satherium'', and the extant African clawless otter. The astragalus is similar to ''E. omoensis'' but differs by the smaller head and thinner neck as well as a larger distal projection of the bone's [[tubercle (bone)|tubercle]]. The talus bone's trochlea (grooved surface forming the joints of bones) is shallow and mediolaterally wide while its tubercle is projected in the approximate center, both of which produce a robust and deep groove (or furrow) of the [[tendons]] of the [[Anatomical terms of motion|plantar flexion]] muscles for extension of the foot at the ankle compared to the African clawless otter.<ref name="giantmustelid"/>
The postcranial remains of ''E. dikikae'' are known by the proximal (upper part) left femur, distal (lower part) right femur, and a humerus. The proximal left femur is known by a large tubercle along the posterior area of the neck, middle-aligning [[lesser trochanter]], and a similar position of the [[medial condyle of the femur]]. The femur specimens indicate large overall sizes of the femurs of ''E. dikikae'' compared with even the largest extant otters. The humerus (complete but weathered and cracked) is much longer and slightly robust compared to that of ''Sivaonyx beyi'', and its [[deltoid tuberosity]] is well-formed. The [[humerus|lateral supracondylar crest]] is longer compared to ''S. beyi'' while the [[medial epicondyle of the humerus|medial epicondyle]] is not as prominent in size. The [[olecranon fossa]] is small and more circular compared to ''S. beyi''.<ref name="Dikikae"/>
''E. omoensis'' is represented only by a single complete left femur which has a short neck and a round head that is oriented in a proximal direction (close to the center) rather than a medial direction (in the center), the former being shifted at 40° relative to the longitude of the [[diaphysis]] section of the bone. The lateromedial width of the [[epiphysis]] is narrow. The femur also has a large [[femoral head]] located on the ventromedial head (aligning to the middle underside of it), a [[greater trochanter]] that bends on the back and is lower than the femoral head, a short and deep [[trochanteric fossa]], and a strong lesser trochanter that is centered more in the middle than on the ventral (or underside) and is thereby visible in a back view. The medial condyle of the femur is larger than the [[lateral condyle of femur|lateral condyle]] of the same bone. The [[intercondylar fossa of femur|intercondylar fossa]] of the femur is rectangular and wide.<ref name="Omoe"/>
===Body Mass===
[[File:Enhydritherium terraenovae.jpg|thumb|left|Skeleton of ''[[Enhydritherium]]'', a bunodont otter genus, in a bipedal position. Bunodont otters including ''Enhydra'', ''Enhydritherium'' and ''Enhydriodon'' are typically estimated to be larger/heavier than non-bunodont otters.]] Some ''Enhydriodon'' species, particularly a few that had resided in Africa, are the [[Largest prehistoric animals#Carnivores (Carnivora)|largest known mustelids]] to have ever existed based on weight estimates, but their precise sizes and weights remain unknown given the lack of complete specimens in their fossil records. Some species like ''E. latipes(?)'' are poorly studied compared to others and therefore lack confirmed size or weight estimates.<ref name="latipes">{{cite journal|last=Koufos|first=George D.|year=2011|title=The Miocene carnivore assemblage of Greece|journal=Estudios Geológicos|language=Spanish|volume=67|issue=2|pages=296–297|doi=10.3989/egeol.40560.190|doi-access=free}}</ref> It is generally estimated that some species of ''Enhydriodon'' are similar in weight to modern large-sized otters while others are estimated as much larger than them (It should also be noted that weight estimates are more often made for bunodont otters like ''Enhydriodon'' than size estimates, although size comparisons to modern animals may be referenced).<ref name="Omoe"/>
The two species of ''Enhydriodon'' native to the subcontinent of India had modest weight estimates, comparable with most other bunodont otter genera as well as extant otter genera. Falconer's 1868 memoir described ''E. sivalensis'' as a lutrine the size of a [[jaguar|panther]].<ref name="Siva"/> In 1932, Pilgrim diagnosed ''E. falconeri'' as being smaller than ''E. sivalensis'', although no size or weight estimates were offered for it by him.<ref name="Falconeri"/> In 2007, Pickford estimated ''E. sivalensis'' to be the largest prehistoric otter in India, ranging from {{cvt|22|kg}} minimum to {{cvt|25|kg}} maximum in body weight, its skull possibly being wolf-sized. He also estimated the body of ''E. falconeri'' based on its lower M<sub>1</sub> teeth dimensions to be similar to the [[African clawless otter]] (''A. capensis''), averaging to {{cvt|16|kg}}.<ref name="Pickford"/>
Africa's ''Enhydriodon'' species are estimated to be some of the largest species of otters to ever exist, reflecting on the Miocene-Pleistocene trend of bunodont otters growing larger than their non-bunodont cousins. Pickford described ''E. kamuhangirei'' of the Western Rift Valley, Uganda (at the time ''Sivaonyx kamuhangirei'') to possibly exceed {{cvt|100|kg}} in weight, making it the largest-known prehistoric otter at the time, although he mentioned that the undescribed fossil otters in Ethiopia (likely sorted later under ''E. dikikae'' and/or ''E. omoensis'') could have possibly been larger than it.<ref name="Pickford"/> ''E. hendeyi'' (then ''Sivaonyx hendeyi'') was estimated to be wolf-sized and around {{cvt|40|kg}} while''E. africanus'' and ''E. ekecaman'' are thought to be of similar sizes.<ref>{{cite news|author1= Alberto Valenciano Vaquero|author2 = Romala Govender|url = https://theconversation.com/gigantic-wolverines-otters-the-size-of-wolves-fossils-offer-fresh-insights-into-the-past-140752|title = Gigantic wolverines, otters the size of wolves: fossils offer fresh insights into the past|publisher = The Conversation|date = 21 June 2020|access-date = 27 November 2022}}</ref><ref name="Omoe"/> ''E. dikikae'' of Ethiopia was estimated to have weighed {{cvt|100|kg}} minimum and {{cvt|200|kg}} maximum (the latter mentioned to be more likely), its holotype suggesting a bearlike size. Compared with most other ''Enhydriodon'' or ''Enhydra'' species, it had an estimated skull length of about {{cvt|25|cm}}.<ref name="Dikikae"/> ''E. omoensis'' was later estimated to weigh more than {{cvt|200|kg}}, making it heavier than ''E. dikikae'' and modern [[lions]]. According to Grohé et al., ''E. omoensis'' was potentially "lion-sized", making it the largest mustelid species to ever exist.<ref name="Omoe"/>
==Palaeobiology==
[[Image:Sea Otter enjoying a clam (33086393883).jpg|thumb|A sea otter eating a clam, similar to suggested diets of certain ''Enhydriodon'' species]]
As fossil bunodont otter genera including ''Enhydriodon'' generally lack complete specimens and postcranial elements, their locomotion and ecological niches remain uncertain. A common theory of the Indian subcontinental species of ''Enhydriodon'' is that based on their robust, bunodont dentition similar to ''Enhydra'', ''E. falconeri'' and ''E. sivalensis'' were both specialized for commonly eating [[shellfish]].<ref name="Lutrinae"/> This claim was made first by Willemsen from analogies of the diet of ''Enhydra'' (abalones and marine bivales) and ''[[Aonyx]]'' (freshwater crabs), but there is little palaeontological evidence to directly support this claim. Regardless, it is suggested that the thick enamel in the posterior dentition of Indian ''Enhydriodon'' species makes them more [[molluscivore|molluscivorous]] than cancrivorous (in contrast, Indian ''Sivaonyx'' species are suggested to have combined shearing functions of the carnassials with overall bunodont crowns to prey more on [[crustaceans]], although bivalves could potentially have been secondary prey for it). The possibility of ''Enhydriodon'' preying on [[bivalves]] is supported by the presence of fossilized freshwater bivalve genera ''[[Parreysia]]'' and ''[[Lamellidens]]'' in the same locations as them, both of which are common throughout the entire Siwalik sedimentary column which spans from 15-2 mya, ranging with the presence of the Enhydriodontini tribe in the Indian subcontinent (India and Pakistan).<ref name="Pickford"/>
The larger ''Enhydriodon'' species in the African continent are suggested to have preyed upon a wider variety of foods in addition to their primary prey including softer prey despite their bunodont dentitions, making their potential diets distinct from those of their Indian subcontinental counterparts. One suggested type of prey was large fish with hard external coverings such as [[catfish]].<ref name="femur">{{cite journal|last=Lewis|first=Margaret E.|year=2008|title=The femur of extinct bunodont otters in Africa (Carnivora, Mustelidae, Lutrinae)|language=French|journal=Comptes Rendus Palevol|volume=7|issue=8|pages=607–627|doi=10.1016/j.crpv.2008.09.010|bibcode=2008CRPal...7..607L }}</ref> Several catfish genera were present in Africa starting from their first appearances during the late Miocene coinciding with the presence of ''Enhydriodon'', including the extant genera ''[[Clarotes]]'', ''[[Bagrus]]'', ''[[Auchenoglanis]]'', and ''[[Chrysichthys]]'' and the extinct genus ''[[Nkondobagrus]]''.<ref>{{cite journal|last=Stewart|first=Kathlyn M|year=2001|title=The freshwater fish of Neogene Africa (Miocene–Pleistocene): systematics and biogeography|journal=Fish and Fisheries|volume=2|issue=3|pages=177–230|doi=10.1046/j.1467-2960.2001.00052.x|bibcode=2001AqFF....2..177S }}</ref> In contrast to the slow-moving, abundant catfish, crabs in Africa were excluded as potential prey for African species of ''Enhydriodon'' given the lack of fossilized crabs at Dikika, unlikeliness for biomasses of crabs to support populations of large otters, and apparent incompatibility for enamel dentition. Fast-swimming fish might have been unlikely to have been regular food sources due to the specialized dentition for crushing hard food in addition to large animals likely not having the ability to catch fast prey. Other armored prey, such as juvenile crocodiles, turtles, and ostrich eggs, were also suggested prey of ''E. dikikae''.<ref name="Dikikae"/>
[[File:Enhydriodon sivalensis restoration.jpg|thumb|Hypothetical [[life restoration]] of ''E. sivalensis'' swimming, its appearance being similar to its relative, the sea otter]]
Femora and dental remains of African ''Enhydriodon'' could possibly hint at a semiaquatic as well as terrestrial lifestyle, meaning that it could eaten both aquatic prey and terrestrial prey. The speculations of ''Enhydriodon's'' lifestyle, however, have been contradictory to each other, so there is, therefore, no majority consensus on it. In 2008, it was speculated that smaller African species of ''Enhydriodon'' based on their smaller femur sizes were more locomotor generalists similar to most mustelids while larger species were fully aquatic since their femur structures shared similarities to ''Enhydra''. However, the Omo and Hadar femoras' proximal ends pointed to a more aquatic nature than most lutrines, while their relative lengths resembled that of terrestrial generalist mustelids, including semiaquatic otters.<ref name="femur"/><ref name="Omoe"/> ''Sivaonyx beyi'' of [[Chad]], speculated to weigh {{cvt|56.4|kg}} to {{cvt|60.1|kg}}, had non-specialized limb proportions that implied generalist-terrestrial locomotion and poor aquatic adaptations.<ref>{{cite journal|last1=Peigné|first1=Stéphane|last2=De Bonis|first2=Louis|last3=Likius|first3=Andossa|last4=Mackaye|first4=Hassane Taïsso|last5=Vignaud|first5=Patrick|last6=Brunet|first6=Michel|year=2008|title=Late Miocene Carnivora from Chad: Lutrinae (Mustelidae)|journal=Zoological Journal of the Linnean Society|volume=152|issue=4|pages=793–846|doi=10.1111/j.1096-3642.2008.00377.x|url=https://zenodo.org/record/5442989 }}</ref> Because of the hypothesis that ''S. beyi'' was a terrestrial predator, ''E. dikikae'' is speculated to have been mostly terrestrial based on its shared fossil location with both aquatic and terrestrial fauna at Dikika.<ref name="Dikikae"/> The palaeobiologies and [[niche differentiation|niche partitionings]] of ''E. ekecaman'' and ''E. cf. dikikae'' in [[Kanapoi]], Kenya remain unclear as their fossil materials, uncovered in the 1960s, were not specifically pronounced beyond "Kanapoi", which future research would have to cover.<ref>{{cite journal|last1=Werdelin|first1=Lars|last2=Manthi|first2=Fredrick Kyalo|year=2012|title=Carnivora from the Kanapoi hominin site, northern Kenya|journal=Journal of African Earth Sciences|volume=64|pages=1–8|doi=10.1016/j.jafrearsci.2011.11.003|bibcode=2012JAfES..64....1W }}</ref> It is also pointed out that African species of bunodont otters like ''Enhydriodon'' and ''Sivaonyx'' were always found in sites in association with permanent bodies of water as opposed to the Upper Laetolil Beds in [[Laetoli]], Tanzania which lacked such a feature, putting a question to the extent of the possibly terrestrial lifestyle of African ''Enhydriodon'' and ''Sivaonyx'' species.<ref>{{cite journal|last1=Werdelin|first1=Lars|last2=Lewis|first2=Margaret E.|year=2020|title=A contextual review of the Carnivora of Kanapoi|journal=Journal of Human Evolution|volume=140|page=102334 |doi=10.1016/j.jhevol.2017.05.001|pmid=28625408 |bibcode=2020JHumE.14002334W |s2cid=23285088 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:nrm:diva-2412 }}</ref>
''E. hendeyi'' was analysed based on femoral robustness index (FRI) and the femoral epicondylar index (FEI), in which its FRI value is comparable to the extinct ''S. beyi'', ''Enhydritherium'', and ''[[Satherium]]'' (the latter two which are analogous to the large sea otter and [[giant river otter]] (''Pteronura brasiliensis'') respectively and have larger values in femoral indexes than most other extant otters) while its FEI value is analogous to the extant African clawless otter and [[Asian small-clawed otter]] (''Aonyx cinereus''). Since both the African clawless otter and Asian small-clawed otter are typically less associated with water bodies compared to other extant otters, it is hypothesized that ''E. hendeyi'' and ''S. beyi'' were both semiaquatic locomotors that had lower associations with water than aquatic locomotors ''Enhydritherium'' and ''Satherium'', although ''S. beyi'' was said to be more terrestrial than ''E. hendeyi''. Meanwhile, the lowest values correspond with ''E. dikikae'', which has similar values to terrestrial [[fossorial|semifossorial]] (adapted to digging and living somewhat underground) musteloids such as the [[American badger]] and the [[striped skunk]], thereby reinforcing the hypothesis that ''E. dikikae'' was a more generalized terrestrial mustelid similar to ''S. beyi''.<ref name="giantmustelid"/>
With the overall lack of consensus on the lifestyle of African ''Enhydriodon'' species considered, a 2022 study on ''E. omoensis'' measured the [[isotopes of carbon|stable carbon]] and [[oxygen isotope ratio cycle|oxygen isotope ratios]] of ''Enhydriodon'' species in comparison to extant terrestrial mammals such as [[felids]], [[hyaenids]], and [[bovids]] along with semiaquatic mammals such as [[hippopotamid]]s. The authors explained that using oxygen isotopic ratios, or [[δ18O]], can be used to understand a taxon's dependency on water, in which extant aquatic and semiaquatic taxa, which includes river and sea otters, have significantly lower oxygen isotopic deviations compared to terrestrial carnivorans. The researchers who studied ''E. omoensis'' found that its tooth enamel δ18O values had a standard deviation of 2.7%, falling outside the δ18O standard deviations of the sea otter, and the [[North American river otter]] (''Lontra canadensis''), which were recorded to be 0.6% and 0.3%-0.9% respectively. The standard deviation of Omo ''Enhydriodon'' aligns itself more within the range of extant terrestrial carnivorans such as hyaenids, suggesting that ''E. omoensis'' was not as semiaquatic as initially thought. The results of the study contradict the 2008 assumption that the Omo ''Enhydriodon'' species was aquatic.<ref name="Omoe"/>
Grohe et al. initially considered that the diet of ''Enhydriodon'' could have been the oyster ''[[Etheria elliptica]]'', which was present in the continent at the same time range. Based on investigations using carbon stable isotopes, a diet of pure oysters would result in an enamel δ13C value of −11.3%. The diet of ''E. omoensis'', however, was not based purely on ''Etheria'' as its minimum-maximum carbon values (-9.7% to -4.7%) are ~2-7% more positive than the expected pure oyster diet value. Its enamel δ13C values fall within the range of mixed [[C3 carbon fixation|C<sub>3</sub>]]-[[C4 carbon fixation|C<sub>4</sub>]] feeders, only partly falling within the range of diets of aquatic feeders of C<sub>3</sub> plants such as fish, turtles, or bivalves. The δ13C standard deviation of Omo ''Enhydriodon'', however, falls outside the range of studied extant freshwater otter populations. It is instead considered that ''E. omoensis'' consumed terrestrial prey with a C<sub>4</sub> diet at least semi-regularly via hunting and/or scavenging. The large bunodont dentition of the species suggests [[durophagy|durophageous]] abilities that allowed it to feed on carrion, including bones, in potentially a similar manner to hyeanas or bone-crushing mustelids.<ref name="Omoe"/>
==Palaeoecology==
===Pakistan and India===
[[Image:Dinocrocuta gigantea.jpg|thumb|A restoration of ''[[Dinocrocuta]] gigantea'', a species of [[Percrocutidae|percrocutine hyaenid]], which lived in the [[Indian subcontinent]] and coexisted with ''E. falconeri'' and other hyaenids during the late Miocene]]
''E. falconeri'' and ''E. sivalensis'', while both ''Enhydriodon'' species that were present in the Siwalik Hills in India and Pakistan during the [[Neogene]] period, did not coexist for the same epochs based on their formation deposit appearances. ''E. falconeri'' remains were present at the Nagri Formation ([[Dhok Milan]] and [[Sethi Nagri]], [[Pakistan]]) and the Dhok Pathan Formation (Dhok Pathan and [[Hasnot]], Pakistan), both formations dating back to the middle Siwaliks representing late Miocene. The species was also present at the Tatrot Formation ([[Tatrot]], India) of the Upper Siwaliks from the early or middle [[Pliocene]]. In the Nagri and Dhok Pathan Formations, ''E. falconeri'' was shown to have existed with several archaic mammalian carnivorous families that went extinct before the Pliocene, such as [[Hyainailourinae|hyainailourine]] [[hyaenodont]]s and [[amphicyonid]]s. The early otter species also existed with various extinct carnivorous members of extant families during the late Miocene representing other [[mustelids]], ursids, felids ([[felinae|felines]] and [[machairodontine]]s), hyaenids ([[Percrocutidae|percrocutinae]] hyaenids [[Ictitheriinae|ictitheres]], and hyaenines), viverrids, and [[herpestid]]s. It is suggested that the extinction of the amphicyonids and percrocutids left empty predatory niches that were quickly filled by other hyaenid genera, which became highly diversified and coexisted with felids in the subcontinent.<ref name="siwaliks">{{cite journal|last1=Jasinski|first1=Steven E.|last2=Abbas|first2=Sayyed Ghyour|last3=Mahmood|first3=Khalid|last4=Babar|first4=Muhammad Adeeb|last5=Khan|first5=Muhammad Akbar|year=2022|title=New Carnivoran(Mammalia: Carnivora) specimens from the Siwaliks of Pakistan and India and their faunal and evolutionary implications|journal=Historical Biology: An International Journal of Paleobiology|volume=35 |issue=11 |pages=1–36|doi=10.1080/08912963.2022.2138376|s2cid=253346978 }}</ref>
Other extinct members of extant and extinct mammalian families were found in the Nagri Formation and thereby existed with ''E. falconeri'' including bovids, [[giraffid]]s, [[anthracothere]]s, [[tragulid]]s, [[suidae|suids]], [[hipparion]]ine [[equid]]s, [[rhinocerotid]]s, [[chalicothere]]s, [[gomphothere]]s, [[hominid]]s, and [[spalacid]]s.<ref>{{cite journal|last1=Khan|first1=Muhammad Akbar|last2=Akhtar|first2=Muhammad|last3=Ikram|first3=Tasneem|title=True Ungulates From The Nagri Type Locality (Late Miocene), Northern Pakistan|journal=Journal of Animal and Plant Sciences|volume=22|pages=1–59}}</ref> An extinct reptilian species of [[gharial]], ''[[Gavialis]] lewisi'' (?), is reported from the Dhok Pathan Formation of Pakistan and is Pliocene in age.<ref name="gavialis">{{cite journal|last=Martin|first=Jérémy|year=2018|title=The taxonomic content of the genus Gavialis from the Siwalik Hills of India and Pakistan|journal=Papers in Palaeontology|volume=5|issue=3|pages=483–497|doi=10.1002/spp2.1247|s2cid=134966832 |url=https://hal.archives-ouvertes.fr/hal-02123647/file/2019Gavialis.pdf }}</ref> Mammal genera that were found in the Dhok Pathan Formation are generally consistent with the mammal genera found within the Nagri Formation but also include other bovids, giraffids, [[Cervinae|cervine]] [[cervids]], anthracotheres, suids, hipparionines, rhinocerotids, "tetralophodont gomphotheres", [[cercopithecid]]s, and [[hystricidae|hystricids]].<ref>{{cite journal|last1=Khan|first1=Muhammad Akbar|last2=Akhtar|first2=Muhammad|last3=Iliopoulos|first3=George|year=2012|title=Tragulids (Artiodactyla, Ruminantia, Tragulidae) from the middle Siwaliks of Hasnot (Late Miocene), Pakistan|journal=Rivista Italiana di Paleontologia e Stratigrafia|volume=118|issue=2|pages=325–341|doi=10.13130/2039-4942/6009}}</ref><ref>{{cite journal|last1=Ghaffar|first1=Abdul|last2=Akhtar|first2=Muhammad|last3=Babar|first3=Muhammad Adeeb|last4=Roohi|first4=Ghazala|year=2018|title=Cervidae from Dhok Pathan and Hasnot areas (Dhok Pathan Formation, Northern Pakistan) with comments on the age of these sediments|journal=Revista Brasileira de Paleontologia|volume=21|issue=2|pages=132–140|doi=10.4072/rbp.2018.2.04|s2cid=59060740 |doi-access=free}}</ref><ref>{{cite journal|last1=Abbas|first1=Ghyour|last2=Babar|first2=Muhammad Adeeb|last3=Khan|first3=Muhammad Akbar|last4=Un Nisa|first4=Badar|year=2021|title=New proboscidean material from the Siwalik Group of Pakistan with remarks on some species|journal=PaleoBios|volume=38|issue=1|pages=1–12|doi=10.5070/P9381054113|s2cid=237772570 |doi-access=free}}</ref><ref>{{cite journal|last1=Babar|first1=Muhammad Adeeb|last2=Aftab|first2=Kiran|last3=Khan|first3=Muhammad Akbar|last4=Abbas|first4=Ghyour|year=2021|title=Tetraconodon and Sivachoerus (Suidae) from Dhok Pathan and Hasnot area of Potwar Plateau, northern Pakistan|journal=Arabian Journal of Geosciences|volume=14|issue=2473|pages=1–6|doi=10.1007/s12517-021-08684-x|bibcode=2021ArJG...14.2473B |s2cid=244120161 }}</ref>
[[Image:Hipparion sp 87348.jpg|thumb|right|The arrival of [[Hipparionini]] equids such as ''[[Hipparion]]'' to Eurasia are representative of major Eurasian faunal turnovers of the late Miocene]]
The transition from the middle Miocene to the late Miocene reflected a period in which the evergreen to deciduous tropical forests once covering a large part of the Indian subcontinent shrank and were replaced by [[grasslands]] because of global cooling, drier conditions, and the intensification of Asian [[monsoons]].<ref>{{cite book|last1=Wang|first1=Xiaoming|last2=Flynn|first2=Lawrence|last3=Fortelius|first3=Mikael|editor-first1=Xiaoming |editor-first2=Lawrence J. |editor-first3=Mikael |editor-last1=Wang |editor-last2=Flynn |editor-last3=Fortelius |date=2013|title=Fossil Mammals of Asia: Neogene Biostratigraphy and Chronology|language=english|publisher=Columbia University Press|chapter=Chapter 17: Indian Neogene Siwalik Mammalian Biostratigraphy: An Overview|pages=423–444|doi=10.7312/wang15012-017|isbn=9780231520829 }}</ref> A change from the Nagri [[floodplains]] to the Dhok Pathan floodplains suggests less draining in the fluvial system of the latter compared to the former with Dhok Pathan's smaller [[rivers]] having more seasonal flow than before. This reflects the general trend of late Miocene [[climate forcing]] resulting in more seasonality, bringing about large faunal turnovers. The drier and more seasonal climates along with fluvial changes gradually brought about larger, open [[woodland]]s predominantly consisting of C<sub>4</sub> plants near the [[Potwar Plateau|Potwar Miocene rivers]] while communities exclusively or predominantly consisting of C<sub>3</sub> plants diminished greatly and eventually disappeared by 7.0 Ma along with the C<sub>3</sub> feeders that depended more on closed vegetation. These changes occurred shortly after the arrivals of the hipparionines and marked decreases in mammal groups within the Indian subcontinent such as the extinctions of the hominid ''Sivapithecus'' and the deinothere ''[[Deinotherium]]'' as a result of the fragmentation of closed habitats in favour of open habitats that would eliminate food for C<sub>3</sub> browsers and frugivores.<ref>{{cite journal|last1=Barry|first1=John C.|last2=Morgan|first2=Michèle E.|last3=Flynn|first3=Lawrence J.|last4=Pilbeam|first4=David|last5=Behrensmeyer|first5=Anna K.|last6=Raza|first6=S. Mahmood|last7= A. Khan|first7=Imran|last8=Badgley|first8=Catherine|last9=Hicks|first9=Jason|last10=Kelley|first10=Jay|year=2002|title=Faunal and Environmental Change in the Late Miocene Siwaliks of Northern Pakistan|journal=Paleobiology|volume=28|issue=2|pages=1–71|doi=10.1666/0094-8373(2002)28[1:FAECIT]2.0.CO;2|s2cid=18408360 }}</ref><ref>{{cite journal|last=Nelson|first=Sherry V.|year=2007|title=Isotopic reconstructions of habitat change surrounding the extinction of Sivapithecus, a Miocene hominoid, in the Siwalik Group of Pakistan|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=243|issue=1–2|pages=204–222|doi=10.1016/j.palaeo.2006.07.017|bibcode=2007PPP...243..204N |url=http://doc.rero.ch/record/15644/files/PAL_E3104.pdf }}</ref><ref>{{cite journal|last1=Patnaik|first1=Rajeev|last2=Singh|first2=Ningthoujam Premjit|last3=Paul|first3=Debajyoti|last4=Sukumar|first4=Raman|year=2019|title=Dietary and habitat shifts in relation to climate of Neogene-Quaternary proboscideans and associated mammals of the Indian subcontinent|journal=Quaternary Science Reviews|volume=224|page=105968 |doi=10.1016/j.quascirev.2019.105968|bibcode=2019QSRv..22405968P |s2cid=210307849 }}</ref>
[[File:Elephant threesome (51340109244).jpg|thumb|left|''[[Elephas]]'' was a typical grazer of C<sub>4</sub> plants from the Pliocene-Pleistocene. It adapted its diets to mixed feeding of C<sub>3</sub> plants by middle Pleistocene while ''[[Stegodon]]'' was a consistent C<sub>4</sub> browser that failed to adapt and went extinct.<ref>{{cite journal|last1=Ma|first1=Jiao|last2=Wang|first2=Yuan|last3=Jin|first3=Changzhu|last4=Hu|first4=Yaowu|last5=Bocherens|first5=Hervé|year=2019|title=Ecological flexibility and differential survival of Pleistocene Stegodon orientalis and Elephas maximus in mainland southeast Asia revealed by stable isotope (C, O) analysis|journal=Quaternary Science Reviews|volume=212|pages=33–44|doi=10.1016/j.quascirev.2019.03.021|bibcode=2019QSRv..212...33M |s2cid=135056116 }}</ref>]]
The carnivoran fossil records of the Tatrot Formation in India are scarce, but amongst the extinct members that existed with ''E. falconeri'' in the Pliocene were other lutrines, machairodontines, and hyaenids.<ref name="siwaliks"/> Herbivorous mammals found at the Tatrot Formation on the Potwar Plateau contain highly diverse assemblages of bovids but also include cervids, suids, [[elephantid]]s, [[stegodont]]ids, hipparionines, anthracotheres, hippopotamids, giraffids, and tragulids.<ref>{{cite journal|last1=Jukar|first1=Advait Muhesh|last2=Sun|first2=Boyang|last3=Nanda|first3=Avinash C.|last4=Bernor|first4=Raymond L.|year=2019|title=The first occurrence of ''Eurygnathohippus'' Van Hoepen, 1930 (Mammalia, Perissodactyla, Equidae) outside Africa and its biogeographic significance|journal=Bollettino della Società Paleontologica Italiana|volume=58|issue=2|pages=171–179|doi=10.4435/BSPI.2019.13}}</ref><ref>{{cite journal|last1=Khan|first1=Muhammad Akbar|last2=Jamil|first2=Madeeha|last3=Mahmood|first3=Khalid|last4=Babar|first4=Muhammad Adeeb|year=2014|title=Some New Remains of Cervids (Cervidae, Ruminantia) from Tatrot Formation of Northern Pakistan|journal=Biologia|volume=60|issue=2|pages=225–230}}</ref><ref>{{cite journal|last=Kumar|first=Suresh|year=2022|title=New Fossils of Sivatherium Giganteum (Giraffidae, Mammalia) from the Upper Siwaliks of the Indian Subcontinent|journal=Acta Palaeontologica Romaniae|volume=18|issue=2|pages=85–92|doi=10.35463/j.apr.2022.02.04|s2cid=248233024 |doi-access=free}}</ref> The crocodilians ''[[Crocodylus]]'' and ''[[Rhamphosuchus]]'', the pelican ''[[Pelecanus]]'', turtles (''[[Batagur]]'', ''[[Geoclemys]]'', ''[[Hardella]]'', and ''[[Pangshura]]''), and the freshwater crab ''[[Acanthopotamon]]'' are reported from at least the Tatrot or Pinjor Formations of India as well, indicating an active freshwater habitat that ''E. falconeri'' and later ''E. sivalensis'' were present in.<ref name="gavialis"/><ref>{{cite journal|first1=Stidham|last1=Thomas A.|last2=Krishan|first2=Kewal|last3=Singh|first3=Bahadur|last4=Ghosh|first4=Abhik|last5=Patnaik|first5=Rajeev|year=2014|title=A Pelican Tarsometatarsus (Aves: Pelecanidae) from the Latest Pliocene Siwaliks of India|journal=PLOS ONE|volume=9|issue=11|pages=1–8|doi=10.1371/journal.pone.0111210|pmid=25365300 |pmc=4218845 |bibcode=2014PLoSO...9k1210S |doi-access=free }}</ref><ref>{{cite journal|last1=Garbin|first1=Rafaella C.|last2=Bandyopadhyay|first2=Saswati|last3=Joyce|first3=Walter G.|year=2020|title=A taxonomic revision of geoemydid turtles from Siwalik-age of India and Pakistan|journal=European Journal of Taxonomy|issue=652|pages=1–67|doi=10.5852/ejt.2020.724.1165|s2cid=229387265 |doi-access=free}}</ref><ref>{{cite journal|last1=Klaus|first1=Sebastian|last2=Singh|first2=Bahadur|last3=Hartmann|first3=Lukas|last4=Krishan|first4=Kewal|last5=Ghosh|first5=Abhik|last6=Patnaik|first6=Rajeev|year=2017|title=A fossil freshwater crab from the Pliocene Tatrot Formation (Siwalik Group) in Northern India (Crustacea, Brachyura, Potamidae)|journal=Palaeoworld|volume=26|issue=3|pages=566–571|doi=10.1016/j.palwor.2016.08.003}}</ref>
Amongst carnivoran taxa, ''Enhydriodon'' is the longest-lasting [[caniform]] genus to have ever existed within the Siwaliks of the Indian subcontinent, identified from the Nagri-Pinjor formations. However, the species identified within the Pinjor Formation of the Plio-Pleistocene epochs is ''E. sivalensis'', which suggests that ''E. falconeri'' after a long time of relative success eventually might have gone through [[anagenesis]] by the Pliocene. Other carnivoran genera that were found in the Pinjor Formation included the newly arrived [[canids]] as well as mustelids, ursids, felids (machairodontines, pantherines, and felines), hyaenids, and viverrids.<ref name="siwaliks"/> Other mammalian genera found within the Pinjor Formation includes hominids, cercopithecids, rodents of various families, proboscideans, equines of the [[Equini]] tribe, rhinocerotids, suids, cervids, giraffids, and bovids.<ref>{{cite journal|last1=Nanda|first1=Avinash C.|last2=Sehgal|first2=Ramesh K.|last3=Chauhan|first3=Parth R.|year=2018|title=Siwalik-age faunas from the Himalayan Foreland Basin of South Asia|journal=Journal of Asian Earth Sciences|volume=162|pages=54–68|doi=10.1016/j.jseaes.2017.10.035|bibcode=2018JAESc.162...54N |s2cid=134929306 }}</ref>
===Ethiopia===
[[File:Enhydriodon East Africa.png|thumb|right|upright=2.2|Geographical and stratigraphic distribution of ''Enhydriodon'' in East Africa by species]]
''E. dikikae'' and ''E. omoensis'' were large lutrine species found in different locations within modern-day [[Ethiopia]]. ''E. dikikae'' fossils were found within the bottom two sequences of the [[Hadar Formation]] of the [[Awash Valley|Lower Awash Valley]], Ethiopia, indicating that its fossils range from 4 Ma to 3.2 Ma. Fossils of ''E. omoensis'' were located at the [[Usno Formation]] and [[Shungura Formation]] of the [[Lower Omo Valley]] in Ethiopia, the fossils ranging from 3.44 Ma to 2.53 Ma. ''E. dikikae'' was named after the Dikikae Basal Member of the Hadar Formation while ''E. omoensis'' had its name derived from the Lower Omo Valley.<ref name="Dikikae"/><ref name="Omoe"/>
There are four [[stratigraphic unit#member|members]] of the Dikika composite sequence as part of the Pliocene Hadar Formation, from base to top: the Basal, Sidi Hakoma, Denen Dora, and Kada Hadar members. All together, they are dated to ca. 3.5-2.9 Ma and are best known for the numerous remains of ''[[Australopithecus afarensis]]''.<ref name="Hadar">{{cite journal|last1=Geraads|first1=Denis|last2=Alemseged|first2=Zeresenay|last3=Bobe|first3=René|last4=Reed|first4=Denné|year=2015|title=Pliocene Carnivora (Mammalia) from the Hadar Formation at Dikika, Lower Awash Valley, Ethiopia|journal=Journal of African Earth Sciences|volume=107|pages=28–35|doi=10.1016/j.jafrearsci.2015.03.020|bibcode=2015JAfES.107...28G }}</ref> ''E. dikikae'' fossils are known from the formation's Basal and Sigi Hakoma members and are unknown in the other top two members.<ref name="Dikikae"/>
Based on methods of determining palaeoenvironments such as ecomorphological analysis, dental microwear of bovids, and carbon and oxygen isotopes of enamel, the Basal Member (BM) has the greatest abundance of bovids and suids in the Hadar Formation, suggesting that the environments of which they were present in were possibly woody grasslands as well as riverine forests. The [[Aepycerotini]] were common within the member, fitting with the [[tribe (taxon)|tribe's]] preference for [[ecotone|ecotonal]] habitats between grasslands and woodlands.<ref name="Hakoma">{{cite book |last1=Campisano |first1=Christopher J. |title=African Paleoecology and Human Evolution |last2=Rowan |first2=John |last3=Reed |first3=Kaye E. |author-link3=Kaye Reed |publisher=Cambridge University Press |year=2022 |editor-last1=Reynolds |editor-first1=Sally C. |pages=214–228 |language=english |chapter=Chapter 18: The Hadar Formation, Afar Regional State, Ethiopia: Geology, Fauna, and Paleoenvironmental Reconstructions |doi=10.1017/9781139696470.018 |editor-last2=Bobe |editor-first2=René}}</ref>
The Sidi Hakoma Submember 1 (SH-1), ranging from ~3.45 to 3.35 Ma, had similar fauna and thereby similar habitats to other members within the Hadar Formation but also likely included wetlands in certain regions. Taxa such as a species within the forest-dwelling [[Cephalophini]] tribe and five species of primates were recovered from the member, further indicating a large riverine forest with, predominantly, woodlands in the surrounding area. ''[[Aepyceros]]'' was the most abundant bovid, and SH-1 had the lowest proportion of grazing bovids at any sub-member of the Hadar Formation. The vegetation of SH-1 might have closely resembled those at the Guinea or Sudanese [[savannas]] that interdigitate with the central African [[rainforest]], which creates habitat mosaics of grasslands, woodlands, and some forest belts. The [[ostracod]] assemblage of the Basal and Sidi Hakoma Members indicate sources of freshwater input, in which their shells also indicate only a three-month dry season, characteristic of the central African savannas. The single dry season, indicating a nine-month rainy season, is a distinctive factor of the Sidi Hakoma member from the modern climate in East Africa, which has a bimodal dry season format (two dry seasons) rather than a single one. The Sidi Hakoma Submember 2 (SH-2) is similar to SH-1 and is thought to have been associated with woodlands with some grassy plains, of which ''Aepycerotini'' was the most common.<ref name="Hakoma"/>
Sidi Hakoma Submember 3 (SH-3) indicates the presence of woodlands and grasslands with more lakeside [[wetlands]] compared to the previous sub-members, with increased presences of [[Reduncinae|reduncine bovids]] and the highest abundance of [[Tragelaphini|tragelaphin bovids]], which indicate either more closed habitats or wetlands. It also contains the largest micromammal assemblages of extant [[murid]] genera such as the extant ''[[Acomys]]'', ''Golunda'' and ''[[Oenomys]]'' and the extinct ''[[Saidomys]]'', of which ''Golunda'' is now extinct in Africa. Sidi Hakoma Submember 4 indicates wetland habitats that surround lakes within drier environments. A further increase of Reduncinae bovids and a decrease in [[Alcelaphinae|alcelaphin bovids]] indicates said lakeshore environments and surrounding wetlands. The bovid abundance data suggests similar amounts of tree cover for SH-3 and SH-4 with the difference being that the latter was slightly drier than the former.<ref name="Hakoma"/>
[[File: Lucy (Australopithecus) National Museum of Ethiopia.jpg|thumb|left|upright=0.7|Skeleton of Lucy, the most well-known ''Australopithecus afarensis'' fossil, at the [[National Museum of Ethiopia]].]]
The Hadar Formation represents many fossils of ''Australopithecus afarensis'', most notably the partial skeleton known as "[[Lucy (Australopithecus)|Lucy]]". The aggregate time span of the species is at least 0.7 myr, from 3.7 Ma to 3.0 Ma.<ref>{{cite journal|last1=Alemseged|first1=Zeresenay|last2=Wynn|first2=Jonathan G.|last3=Kimbel|first3=William H.|last4=Reed|first4=Denné|last5=Geraads|first5=Denis|last6=Bobe|first6=René|year=2005|title=A new hominin from the Basal Member of the Hadar Formation, Dikika, Ethiopia, and its geological context|journal=Journal of Human Evolution|volume=49|issue=4|pages=499–514|doi=10.1016/j.jhevol.2005.06.001|pmid=16026815 |bibcode=2005JHumE..49..499A }}</ref> The Hadar Formation is also known for its representation of a great diversity of bovid species that represented most major tribes in Africa. The bovid tribes that were found in the formation included the Aepycerotini, Alcelaphini, [[Antilopini]], [[Bovini]], [[Caprini]], Cephalophini, [[Hippotragini]], [[Neotragini]], Reduncini, and Tragelaphini. Other groups, represented by extinct species of extant or extinct genera, include giraffids, hippopotamuses, suids, canids, felids (machairodontines were the most common), hyaenids, other mustelids, viverrids, rhinoceroses, equids, [[catarrhines]], deinotheres, and elephantids were all also found within the locality. Small mammal groups include [[bat]]s, leporids, old world porcupines, murid rodents, [[spalacid]]s, [[squirrels]], and [[aardvark]]s.<ref name="Hakoma"/><ref name="Hadar"/>
Other Pliocene-age formations within Ethiopia show similar trends of great diversity in the Bovidae family from its multiple tribes along with suids, hippopatamids, cercopithecids, hominids, and equids of generally the same genera as the Hadar Formation. Most herbivores present in the Shungura Formation show either consistent C<sub>4</sub> diets or had generally shifted from mixed C<sub>3</sub>-C<sub>4</sub> diets to generally C<sub>4</sub> diets as indicated from changes in dentition by formation member. These trends suggest that the African herbivores in the Pliocene were increasingly shifting to C<sub>4</sub> herbivory as opposed to browsing and mixed feeding as a result of the increasing dominance of C<sub>4</sub> grasslands in Africa. There were a few exceptions, however, as Giraffidae and Deinotheriidae were both consistently C<sub>3</sub> browsers within the formation while the bovid tribes Aepycerotini and Tragelaphini were predominantly mixed feeders with little change in diet.<ref name="herbivory">{{cite journal|last1=Bobe|first1=René|year=2011|title=Fossil Mammals and Paleoenvironments in the Omo-Turkana Basin|journal=Evolutionary Anthropology|volume=20|issue=6|pages=254–263|doi=10.1002/evan.20330|pmid=22170694 |s2cid=205826374 }}</ref><ref>{{cite journal|last1=Negash|first1=Enquye W.|last2=Alemseged|first2=Zeresenay|last3=Bobe|first3=René|last4=Grine|first4=Frederick|last5=Sponheimer|first5=Matt|last6=G. Wynn|first6=Jonathan|year=2020|title=Dietary trends in herbivores from the Shungura Formation, southwestern Ethiopia|journal=Proceedings of the National Academy of Sciences|volume=117|issue=36|pages=21921–21927|doi=10.1073/pnas.2006982117|pmid=32839326 |pmc=7486712 |bibcode=2020PNAS..11721921N |doi-access=free }}</ref><ref>{{cite journal|last1=Bibi|first1=Faysal|last2=Souron|first2=Antoine|last3=Bocherens|first3=Hervé|last4=Uno|first4=Kevin|last5=Boisserie|first5=ean-Renaud|year=2013|title=Ecological change in the lower Omo Valley around 2.8 Ma|journal=Biology Letters|volume=9|issue=1|pages=1–4|doi=10.1098/rsbl.2012.0890|pmid=23234862 |pmc=3565503 |s2cid=10791621 }}</ref> Fossil fish remains are also known from the Shungura Formation, namely the genera ''[[Polypterus]]'', ''[[Sindacharax]]'', ''[[Synodontis]]'', ''[[Auchenoglanis]]'', and ''[[Lates]]''.<ref>{{cite journal|last1=Stewart|first1=Kathlyn M.|last2=Murray|first2=Alison|year=2008|title=Fish remains from the Plio-Pleistocene Shungura Formation, Omo River basin, Ethiopia|journal=Geobios|volume=41|issue=2|pages=283–295|doi=10.1016/j.geobios.2007.06.004|bibcode=2008Geobi..41..283S }}</ref>
==Notes==
{{Notelist}}
==References==
{{
{{Musteloidea|Mae.|state=collapsed}}
{{Taxonbar|from=Q27962593}}
[[Category:Otters]]
[[Category:
[[Category:Miocene mustelids]]
[[Category:Fossil taxa described in 1868]]
[[Category:Miocene mammals of Africa]]
[[Category:Pliocene mammals of Africa]]
[[Category:Pleistocene mammals of Africa]]
[[Category:Miocene mammals of Asia]]
[[Category:Pliocene mammals of Asia]]
[[Category:Taxa named by Hugh Falconer]]
[[Category:Prehistoric carnivoran genera]]
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