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{{Use dmy dates|date=November 2024}}
{{Automatic taxobox
| fossil_range = Middle [[Eocene]] to Late Eocene {{fossil range|43.5|37}}
| image = Pseudamphimeryx renevieri.jpg
| image_caption = ''Pseudamphimeryx renevieri'' mandible, [[Natural History Museum of Basel]]
| taxon = Pseudamphimeryx
| authority = [[Hans Georg Stehlin|Stehlin]], 1910
| type_species = {{extinct}}'''''Pseudamphimeryx renevieri'''''
| type_species_authority = [[François Jules Pictet de la Rive|Pictet]] & [[Aloïs Humbert|Humbert]], 1869
| subdivision_ranks = Other species
| subdivision = {{species list
|{{extinct}}'''''P. schlosseri'''''|[[Ludwig Ruetimeyer|Ruetimeyer]], 1891
|{{extinct}}'''''P. valdensis?'''''|Stehlin, 1910
|{{extinct}}'''''P. pavloviae'''''|Stehlin, 1910
|{{extinct}}'''''P. hantonensis'''''|[[Clive Forster-Cooper|Forster-Cooper]], 1928
|{{extinct}}'''''P. salesmei'''''|Sudre, 1978
}}
}}

'''''Pseudamphimeryx''''' is an extinct genus of [[Paleogene|Palaeogene]] [[artiodactyl]]s belonging to the family [[Amphimerycidae]] that was endemic to the central region of western Europe and lived from the Middle to Late [[Eocene]]. It was first erected in 1910 by the Swiss palaeontologist [[Hans Georg Stehlin]], who assigned to it multiple species and noted specific differences from another amphimerycid ''[[Amphimeryx]]''. As of present, it is known by six species, although the validity of ''P. valdensis'' has been questioned while the earliest-appearing species ''P. schosseri'' has been suggested to not be an amphimerycid.

''Pseudamphimeryx'' is very similar to ''Amphimeryx'' with its [[selenodont]] (crescent-like ridges) dentition and its fused "cubonavicular bone" ([[cuboid bone]] and [[navicular bone]]) of its hind legs, both of which are recorded in [[ruminant]]s in an instance of [[parallel evolution]]. Both amphimerycid genera had large [[orbit (anatomy)|orbits]] and long snouts. ''Pseudamphimeryx'' has very specific differences with ''Amphimeryx'' such as the occipital crest forms. Its selenodont dentition suggests that it had a preference for leaf-eating diets. It inhabited western Europe back when it was an [[archipelago]] that was isolated from the rest of Eurasia, meaning that it lived in a tropical-subtropical environment with various other faunas that also evolved with strong levels of endemism. This meant that it coexisted with a wide variety of other artiodactyls and perissodactyls. Although it survived a major [[faunal turnover]] by the Middle Eocene, it was eventually replaced by ''Amphimeryx'' in the Late Eocene.

== Taxonomy ==
[[File:Pseudamphimeryx renevieri Amphimeryx murinus mandibles.png|thumb|left|Mandibles of ''[[Pseudamphimeryx]] renevieri'' (left) and ''Amphimeryx murinus'' (right)]]
In 1910, the Swiss palaeontologist [[Hans Georg Stehlin]] erected the genus ''[[Pseudamphimeryx]]'', introducing it as an [[artiodactyl]] that differed from ''[[Amphimeryx]]'' only by specific cranial and dental traits. He first recognized the species ''Pseudamphimeryx Renevieri'', which was previously classified to ''[[Cainotherium]]'' then ''Xiphodontherium'' (the latter synonymized with ''Amphimeryx''); it was first named by the naturalists [[François Jules Pictet de la Rive]] and [[Aloïs Humbert]] in 1869. The second species that he classified to ''Pseudamphimeryx'' was ''P. Schlosseri'', first named as a species of ''[[Dichobune]]'' by [[Ludwig Ruetimeyer]] in 1891. Stehlin then named the species ''P. valdensis'' based on lower fossil [[molar (tooth)|molars]] from the Swiss locality of [[Mormont]], stating that it was smaller than ''P. renevieri'' in size. He also recognized two additional taxa from the [[Phosphorites du Quercy]] site: ''P. Renevieri'' var. ''Pavlowiae'' and ''P. decedens''.{{efn|Due to archaic species naming conventions, authors of the 19th and 20th centuries tended to capitalize species names based on individuals or places.}}<ref name="stehlin">{{cite journal|last=Stehlin|first=Hans Georg|year=1910|title=Die Säugertiere des schweizerischen Eocaens. Sechster Teil: Catodontherium – Dacrytherium – Leptotherium – Anoplotherium – Diplobune – Xiphodon – Pseudamphimeryx – Amphimeryx – Dichodon – Haplomeryx – Tapirulus – Gelocus. Nachträge, Artiodactyla incertae sedis, Schlussbetrachtungen über die Artiodactylen, Nachträge zu den Perissodactylen.|journal=Abhandlungen der Schweizerischen Paläontologischen Gesellschaft|volume=36|url=https://www.biodiversitylibrary.org/item/247842#page/5/mode/1up|access-date=30 August 2023|archive-date=5 August 2023|archive-url=https://web.archive.org/web/20230805150136/https://www.biodiversitylibrary.org/item/247842#page/5/mode/1up|url-status=live}}</ref><ref>{{cite book|last1=Pictet|first1=François Jules|last2=Humbert|first2=Aloïs Humbert|year=1869|title=Mémoire sur les animaux vertébrés: trouvés dans le terrain sidérolitique du Canton de Vaud et appartenant a la faune éocène: supplément|publisher=H. Georg|volume=2|url=https://www.biodiversitylibrary.org/item/112849#page/9/mode/1up}}</ref><ref>{{cite journal|last=Rütimeyer|first=Ludwig|year=1891|title=II. Ungulata Paridigitata|journal=Abhandlungen der Schweizerischen paläontologischen Gesellschaft|volume=18|pages=73–75|url=https://www.biodiversitylibrary.org/item/265968#page/77/mode/1up}}</ref>

In 1928, English palaeontologist [[Clive Forster-Cooper]] erected ''P. hantonensis'' based on two upper molars from [[Hordle]] in England.<ref>{{cite journal|last=Forster-Cooper|first=Clive|year=1928|title=Pseudamphimeryx hantonensis, sp. n., with notes on certain species of Artiodactyls from the Eocene deposits of Hordwell|journal=Annals and Magazine of Natural History|volume=2|issue=7|pages=49–55|doi=10.1080/00222932808672847|url=https://archive.org/details/in.ernet.dli.2015.20318/page/n59/mode/2up}}</ref> In 1978, French palaeontologist Jean Sudre recognized ''P. pavloviae'' as a distinct species and erected another named ''P. salesmei'' based on a [[mandible]] from the French locality of Salesmes.<ref name="artiodactyles">{{cite book|last=Sudre|first=Jean|year=1978|title=Les Artiodactyles de l'Eocéne moyen et supérieur d'Europe occidentale|publisher=University of Montpellier}}</ref><ref name="mormont">{{cite book|last1=Hooker|first1=Jerry J.|last2=Weidmann|first2=Marc|year=2000|title=Eocene Mammal Faunas of Mormont, Switzerland: Systematic Revision and Resolution of Dating Problems|publisher=Kommission der Schweizerischen Paläontologischen Abhandlungen|volume=120|pages=92–94}}</ref>

In 1974, the French palaeontologist Colette Dechaseaux noted that ''P. decedens'' had notably large [[orbit (anatomy)|orbits]] along with [[preorbital fossa]]e in front of them like in [[deer]]; these morphologies previously gave palaeontologists ideas of the appearance of the skull of ''Pseudamphimeryx''. She casted doubt that the species actually belonged to ''Pseudamphimeryx'' because of the molar forms. Similarly in 1978, Sudre expressed that ''P. decedens'' actually belonged to ''Pseudamphimeryx'', stating the the short [[premolar]]s, large [[orbit (anatomy)|orbits]], and preorbital fossae are not present in any other skull of other amphimerycid species. In 1984, Sudre tentatively reassigned ''P. decedens'' to the [[chevrotain|tragulid]] genus ''Cryptomeryx'' as ''C? decedens'', building on to Dechaseaux's study by confirming that the now-lost skull would have belonged to a small [[ruminant]].<ref name="reconstruction">{{cite journal|last=Dechaseaux|first=Colette|year=1974|title=Artiodactyles primitifs des phosphorites du Quercy|journal=Annales de Paléontologie. Vertèbres|volume=60|pages=59–100}}</ref><ref name="artiodactyles"/><ref>{{cite journal|last=Sudre|first=Jean|year=1984|title=Cryptomeryx Schlosser, 1886, Tragulidé de l'oligocène d'Europe; relations du genre et considérations sur l'origine des ruminants|journal=Palaeovertebrata|volume=14|issue=1|pages=1–31|url=https://palaeovertebrata.com/articles/view/114}}</ref> In 1986, however, Geneviève Bouvrain, Denis Geraads and Jean Sudre revised ''Cryptomeryx'' as a synonym of ''[[Lophiomeryx]]'',<ref>{{cite journal|last1=Bouvrain|first1=Geneviève|last2=Geraads|last3=Sudre|first3=Jean|year=1986|title=Révision taxonomique de quelques Ruminants oligocènes desphosphorites du Quercy.|journal=Comptes Rendus de l'Académie des Sciences de Paris|volume=302|issue=2|language=french|pages=101–104|url=https://www.researchgate.net/publication/291855583_A_taxonomic_revision_of_some_Oligocene_ruminants_from_the_Quercy_phosphorites}}</ref> but it was alternatively considered a synonym of ''Iberomeryx'' by Bastien Mennecart et al. in 2010. ''C? decedens'' had tentatively been placed in ''[[Iberomeryx]]'' in a 2012 PhD thesis by Mennecart.{{efn|The species "''L.''" ''gaudryi'', formerly the type species of the now-invalid ''Cryptomeryx'', is pending reassessment to another genus.}}<ref name="ruminantia">{{cite thesis|type=PhD|last=Mennecart|first=Bastien|year=2012|title=The Ruminantia (Mammalia, Cetartiodactyla) from the Oligocene to the Early Miocene of Western Europe: systematics, palaeoecology and palaeobiogeography|publisher=Université de Fribourg|url=https://core.ac.uk/download/pdf/20660663.pdf}}</ref><ref>{{cite journal|last1=Wang|first1=Bian|last2=Wang|first2=Qian|last3=Zhang|first3=Zhao-Qun|year=2023|title=New materials of Lophiomeryx (Artiodactyla: Lophiomerycidae) from the Oligocene of Nei Mongol, China|journal=Journal of Mammalian Evolution|volume=30|pages=1047–1066|doi=10.1007/s10914-023-09691-3}}</ref>

In 2000, the palaeontologists Jerry J. Hooker and Marc Weidmann suggested that ''P. pavloviae'' be emended back to ''P. pavlowiae'' based on Stehlin's original spelling and argued that ''P. valdensis'' was both a ''[[nomen dubium]]'' and potentially a junior synonym of ''P. renevieri''.<ref name="mormont">{{cite book|last1=Hooker|first1=Jerry J.|last2=Weidmann|first2=Marc|year=2000|title=Eocene Mammal Faunas of Mormont, Switzerland: Systematic Revision and Resolution of Dating Problems|publisher=Kommission der Schweizerischen Paläontologischen Abhandlungen|volume=120|pages=92–94}}</ref> In 2007, palaeontologists Jörg Erfurt and Grégoire Métais listed ''P. valdensis'' as a valid species without referencing Hooker and Weidmann's invalidation of the species.<ref name="endemic">{{cite book|editor-last1=Prothero|editor-first1=Donald R.|editor-last2=Foss|editor-first2=Scott E.|last1=Erfurt|first1=Jörg|last2=Métais|first2=Grégoire|year=2007|title=The Evolution of Artiodactyls|publisher=Johns Hopkins University Press|chapter=Endemic European Paleogene Artiodactyls|pages=59–84}}</ref>

=== Classification ===
[[File:Tragulus javanicus.jpg|thumb|Because of some similar anatomical traits of the [[Amphimerycidae|amphimerycids]] to those of ruminants (like the [[Java mouse-deer]] (''[[Tragulus]] javanicus''), pictured), they were previously considered ruminants by biologists. Today, their evolutionary relationship to ruminants and other artiodactyls proves unclear.]]
''Pseudamphimeryx'' belongs to the [[Amphimerycidae]], a [[Paleogene|Palaeogene]] [[artiodactyl]] family endemic to western Europe that lived from the middle to the earliest [[Oligocene]] (~44 to 33 Ma). Like the other contemporary endemic artiodactyl families of western Europe, the evolutionary origins of the Amphimerycidae are poorly known.<ref name="endemic"/> The family is generally thought to have made its first appearance by the unit MP14 of the [[Mammal Paleogene zones|Mammal Palaeogene zones]], making them the first selenodont dentition artiodactyl representatives to have appeared in the landmass along with the [[Xiphodontidae]].<ref name="turnover">{{cite journal|last=Franzen|first=Jens Lorenz|year=2003|title=Mammalian faunal turnover in the Eocene of central Europe|journal=Geological Society of America Special Papers|volume=369|pages=455–461|doi=10.1130/0-8137-2369-8.455|isbn=9780813723693 }}</ref> The first representative of the Amphimerycidae to have appeared was ''Pseudamphimeryx'', lasting from MP14 to MP17. ''Amphimeryx'' made its first appearance in MP18 as the only other known amphimerycid genus and lasted up to MP21, after the Grande Coupure faunal turnover event.<ref name="endemic"/>

Because of its similar anatomical traits with [[ruminant]]s, some palaeontologists had originally included it within the suborder Ruminantia while some others rejected the placement. Today, its similarities with ruminants is thought to have been an instance of [[parallel evolution]], in which amphimerycids and ruminants independently gained similar traits.<ref name="endemic"/><ref name="thesis">{{cite thesis|last=Weppe|first=Romain|year=2022|title=Déclin des artiodactyles endémiques européens, autopsie d'une extinction|language=french|publisher=University of Montpellier|url=https://theses.hal.science/tel-04160245|access-date=2023-08-30|archive-date=2023-08-11|archive-url=https://web.archive.org/web/20230811141229/https://theses.hal.science/tel-04160245|url-status=live}}</ref> While amphimerycids have typically been excluded from the Ruminantia due to dental characteristics, it does not eliminate the possibility of them being sister taxa to ruminants by the latter independently gaining longer legs and more [[selenodont]] (crescent-shaped) dentition.<ref>{{cite journal|last1=Janis|first1=Christine M.|last2=Theodor|first2=Jessica M.|year=2014|title=Cranial and postcranial morphological data in ruminant phylogenetics|journal=Zitteliana B|volume=32|pages=15–31|doi=10.5282/ubm/epub.22383}}</ref> Its affinities, along with those of other endemic European artiodactyls, are unclear; the Amphimerycidae, [[Anoplotheriidae]], Xiphodontidae, [[Mixtotheriidae]], and [[Cainotheriidae]] have been determined to be closer to either [[Tylopoda|tylopods]] (i.e. [[camelid]]s and [[merycoidodont]]s) or [[ruminant]]s. Different phylogenetic analyses have produced different results for the "derived" selenodont Eocene European artiodactyl families, making it uncertain whether they were closer to the Tylopoda or Ruminantia.<ref name="thesis"/><ref name="Revision of the Eocene artiodactyls"/><ref name="Cainotheriidae">{{cite journal|last1=Weppe|first1=Romain|last2=Blondel|first2=Cécile|last3=Vianey-Liaud|first3=Monique|last4=Escarguel|first4=Gilles|last5=Pélissié|first5=Thierry|last6=Antoine|first6=Pierre-Olivier|last7=Orliac|first7=Maëva Judith|year=2020|title=Cainotheriidae (Mammalia, Artiodactyla) from Dams (Quercy, SW France): phylogenetic relationships and evolution around the Eocene–Oligocene transition (MP19–MP21)|journal=Journal of Systematic Palaeontology|volume=18|number=7|pages=541–572|doi=10.1080/14772019.2019.1645754|bibcode=2020JSPal..18..541W|s2cid=202026238|url=https://hal.archives-ouvertes.fr/hal-02349546/file/caino_manuscrit_Review2.pdf|access-date=2023-09-19|archive-date=2022-03-07|archive-url=https://web.archive.org/web/20220307180222/https://hal.archives-ouvertes.fr/hal-02349546/file/caino_manuscrit_Review2.pdf|url-status=live}}</ref>

In an article published in 2019, Romain Weppe et al. conducted a phylogenetic analysis on the [[Cainotherioidea]] within the Artiodactyla based on mandibular and dental characteristics, specifically in terms of relationships with artiodactyls of the Palaeogene. The results retrieved that the superfamily was closely related to the Mixtotheriidae and Anoplotheriidae. They determined that the Cainotheriidae, [[Robiacinidae]], Anoplotheriidae, and Mixtotheriidae formed a clade that was the sister group to the Ruminantia while Tylopoda, along with the Amphimerycidae and Xiphodontidae split earlier in the tree.<ref name="Cainotheriidae"/> The phylogenetic tree used for the journal and another published work about the cainotherioids is outlined below:<ref name="Cainotherioidea">{{cite journal|last1=Weppe|first1=Romain|last2=Blondel|first2=Cécile|last3=Vianey-Liaud|first3=Monique|last4=Pélissié|first4=Thierry|last5=Orliac|first5=Maëva Judith|year=2020|title=A new Cainotherioidea (Mammalia, Artiodactyla) from Palembert (Quercy, SW France): Phylogenetic relationships and evolutionary history of the dental pattern of Cainotheriidae|journal=Palaeontologia Electronica|number=23(3):a54|doi=10.26879/1081|s2cid=229490410 |doi-access=free}}</ref>

{{clade| style=font-size:85%; line-height:85%
|1={{clade
|1=''[[Eurodexis|Eurodexis russelli]]''
|2=''[[Dichobune|Dichobune leporina]]''
|3={{clade
|1={{clade
|1='''''[[Amphimeryx|Amphimeryx murinus]]'''''
|2={{clade
|1=''[[Xiphodon|Xiphodon castrense]]''
|label2=[[Tylopoda]]
|2={{clade
|1=''[[Paratoceras|Paratoceras coatesi]]''
|2=''[[Eotylopus|Eotylopus reedi]]''}}}}}}
|2={{clade
|label1=[[Ruminantia]]
|1={{clade
|1=''[[Parvitragulus|Parvitragulus priscus]]''
|2={{clade
|1=''[[Lophiomeryx|Lophiomeryx chalaniati]]''
|2=''[[Archaeomeryx|Archaeomeryx optatus]]''}}}}
|2={{clade
|label1=[[Mixtotheriidae]]
|1=''[[Mixtotherium|Mixtotherium cuspidatum]]''
|label2=[[Anoplotheriidae]]
|2={{clade
|1=''[[Anoplotherium latipes]]''
|2=''[[Dacrytherium|Dacrytherium ovinum]]''}}
|label3=[[Cainotherioidea]]
|3={{clade
|label1=[[Robiacinidae]]
|1={{clade
|1=''[[Robiacina|Robiacina lavergnesis]]''
|2={{clade
|1=''[[Robiacina|Robiacina minuta]]''
|2=''[[Robiacina|Robiacina quercyi]]''}}}}
|label2=[[Cainotheriidae]]
|2={{clade
|1=''[[Palembertina|Palembertina deplasi]]''
|2={{clade
|label1=[[Oxacroninae]]
|1={{clade
|1=''[[Paroxacron|Paroxacron bergeri]]''
|2={{clade
|1=''[[Paroxacron|Paroxacron valdense]]''
|2=''[[Oxacron|Oxacron courtoisii]]''}}}}
|label2=[[Cainotheriinae]]
|2={{clade
|1=''[[Cainotherium|Cainotherium laticurvatum]]''
|2={{clade
|label1=''[[Caenomeryx]]''
|1={{clade
|1=''[[Caenomeryx|Caenomeryx filholi]]''
|2=''[[Caenomeryx|Caenomeryx procommunis]]''}}
|label2=''[[Plesiomeryx]]''
|2={{clade
|1=''[[Plesiomeryx|Plesiomeryx cadurcensis]]''
|2=''[[Plesiomeryx|Plesiomeryx huerzeleri]]''}}}}}}}}}}}}}}}}}}}}}}

In 2020, Vincent Luccisano et al. created a phylogenetic tree of the basal artiodactyls, a majority endemic to western Europe, from the Palaeogene. In one clade, the "bunoselenodont endemic European" Mixtotheriidae, Anoplotheriidae, Xiphodontidae, Amphimerycidae, Cainotheriidae, and Robiacinidae are grouped together with the Ruminantia. The phylogenetic tree as produced by the authors is shown below:<ref name="Revision of the Eocene artiodactyls">{{cite journal|last1=Luccisano|first1=Vincent|last2=Sudre|first2=Jean|last3=Lihoreau|first3=Fabrice|year=2020|title=Revision of the Eocene artiodactyls (Mammalia, Placentalia) from Aumelas and Saint-Martin-de-Londres (Montpellier limestones, Hérault, France) questions the early European artiodactyl radiation|journal=Journal of Systematic Palaeontology|volume=18|issue=19|pages=1631–1656|doi=10.1080/14772019.2020.1799253|bibcode=2020JSPal..18.1631L |s2cid=221468663 }}</ref>

{{clade| style=font-size:85%; line-height:85%
|label1=[[Artiodactyla]]&nbsp;
|1={{clade
|label2=
|1=''[[Bunophorus]]''
|2={{clade
|1=''[[Gunophorus]]''
|2=''[[Diacodexis]]''
}}
|3={{clade
|1={{clade
|1=''[[Protodichobune]]''
|2=''[[Eurodexis]]''
}}
|2={{clade
|1={{clade
|1=''[[Buxobune]]''
|2={{clade
|1=''[[Mouillacitherium]]''
|2=''[[Meniscodon]]''
}}
|3={{clade
|1={{clade
|1=''[[Hyperdichobune]]''
|2={{clade
|1=''[[Dichobune|Dichobune robertiana]]''
|2={{clade
|1=''[[Dichobune|Dichobune leporina]]''
|2={{clade
|1=''[[Homacodon]]''
|2={{clade
|label2=[[Suina]]&nbsp;
|1=''[[Gobiohyus]]''
|2={{clade
|1={{clade
|1=''[[Khirtharia]]''
|2=''[[Entelodon]]''
}}
|2={{clade
|1=''[[Palaeocheorus]]''
|2=''[[Perchoerus]]''
}}
}}
}}
}}
}}
}}
}}
|2={{clade
|label1=[[Haplobunodontidae]]&nbsp;
|1={{clade
|1=''[[Haplobunodon]]''
|2={{clade
|1=''[[Cuisitherium]]''
|2=''[[Lophiobunodon]]''
}}
}}
|2={{clade
|1=''[[Mixtotherium]]''
|2={{clade
|1=''[[Robiacina]]''
|2={{clade
|1={{clade
|1={{clade
|1=''[[Dacrytherium]]''
|2=''[[Diplobune]]''
}}
|2={{clade
|1=''[[Xiphodon]]''
|2=''[[Paraxiphodon]]''
}}
}}
|2={{clade
|1={{clade
|1=''[[Cainotherium]]''
|2=''[[Paroxacron]]''
}}
|2={{clade
|1=''[[Archaeomeryx]]''
|2={{clade
|1=''[[Amphimeryx]]''
|2='''''Pseudamphimeryx'''''
}}
}}
}}
}}
}}
}}
}}
}}
}}
|2={{clade
|1=''[[Aumelasia]]''
|2={{clade
|1={{clade
|1=''[[Hallebune]]''
|2=''[[Amphirhagatherium]]''
}}
|2={{clade
|label1=[[Cebochoeridae]]&nbsp;
|1={{clade
|1=''[[Cebochoerus]]''
|2=''[[Gervachoerus]]''
}}
|2={{clade
|1=''[[Choeropotamus]]''
|2=''[[Siamotherium]]''
}}
}}
}}
}}
}}
}}
}}
}}

In 2022, Weppe conducted a phylogenetic analysis in his academic thesis regarding Palaeogene artiodactyl lineages, focusing most specifically on the endemic European families. One large monophyletic set consisted of the [[Hyperdichobuninae]], Amphimerycidae, Xiphodontidae, and Cainotherioidea based on dental [[synapomorphies]], of which the hyperdichobunines are paraphyletic in relation to the other clades. In terms of the amphimerycids, while the clade consisting of ''P. renevieri'' and ''A. murinus'' was recovered as a sister group to the other endemic artiodactyl clades, the placement of ''P. schlosseri'' has rendered the Amphimerycidae paraphyletic in relation to the derived amphimerycid species and other families. He argued that the Amphimerycidae thus needs a systemic revision for which ''P. schlosseri'' would be assigned to a new genus and removed from the Amphimerycidae.<ref name="thesis"/>

== Description ==
=== Skull ===
The Amphimerycidae is defined in part as having an elongated snout and large orbits that are widened in their backs.<ref name="endemic"/> ''Pseudmphimeryx'' specifically is described as having a skull whose peak appears initially concave at the occipital crest's front, ascends slightly, and then finally slopes down. The skull is also diagnosed as having strong [[body orifice]]s in its [[basicranium]] and projecting occipital crests.<ref name="artiodactyles"/> ''Pseudamphimeryx'' and ''Amphimeryx'', both known by multiple skull specimens, have very similar forms but differ based on a few characteristics.<ref name="reconstruction"/> ''Amphimeryx'' is also distinguished from ''Pseudamphimeryx'' by the more well-developed occipital crest. Its skull additionally resembles those of both ''[[Dacrytherium]]'' and ''[[Tapirulus]]''.<ref name="skulls">{{cite journal|last1=Pearson|first1=Helga Sharpe|year=1927|title=On the Skulls of Early Tertiary Suidae, together with an Account of the Otic Region in Some Other Primitive Artiodactyla|journal=Philosophical Transactions of the Royal Society of London. Series B, Containing Papers of a Biological Character|volume=215|issue=421–430|pages=440–445|doi=10.1098/rstb.1927.0009|doi-access=free}}</ref>

The overall skull of ''Pseudamphimeryx'' is very elongated especially in comparison to ''[[Mouillacitherium]]'' but falls short of that of ''Amphimeryx''. The [[parietal bone]] and [[squamosal bone]] both make up a prominent portion of the [[cranial cavity]]'s wall. Both amphimerycid genera have especially prominent occipital and [[sagittal crest]]s, the latter of which divides into two less prominent branches behind the fronto-parietal suture that extend up to the [[supraorbital foramen]]. This is unlike ''Mouillacitherium'' where the crest's extension only goes up to the foramen's back.<ref name="reconstruction"/> The glenoid surface of ''Pseudamphimeryx'' is positioned slightly above the overall [[base of skull|base of the skull]] and has a slightly convex form as opposed to a flat one like in primitive ruminants. The glenoid region of the skull also has a deep concavity above it like in ruminants but unlike in anoplotheriids. The [[zygomatic arch]], or cheek bone, is thin.<ref name="skulls"/> The orientation of the occipital crest differs by amphimerycid genus, with that of ''Pseudamphimeryx'' being straight and vertical. Amphimerycids have primitive "mastoid" forms (in which the [[periotic bone]] of the ear is exposed to the skull's surface) akin to those of the [[Dichobunidae|dichobunids]] ''Dichobune'' and ''Mouillacitherium''.<ref name="reconstruction"/>

The [[frontal bone]]s of both amphimerycid genera are large plus flat, being particularly sizeable in their supraorbital portions; this trait is more pronounced in ''Amphimeryx''. That of ''Amphimeryx'' is close to the orbits' upper edges and is more prominent in position between the two orbits than that of ''Pseudamphimeryx''. The supraorbital foramen of ''Amphimeryx'' is wider than it is long and is proportionally larger than that of ''Pseudamphimeryx''. It is also more perpendicular to the [[sagittal plane]] in its back edge, which is not oriented backwards like in ''Pseudamphimeryx''. The [[lacrimal bone]] of both amphimerycids, but especially in ''Amphimeryx'', has an extensive ''[[pars facialis]]'' and is quadrangular in shape, narrowing at its front. The orbit is large, is positioned back in relation to the overall skull, is wide at its back area, and is more curved at its upper compared to lower edge. There is no difference between both amphimerycids in terms of the orbits, suggesting based on their morphologies that the snouts of both genera are elongated. The [[optic foramen]], located in the [[sphenoid bone]], extends more forward in ''Amphimeryx'' than in ''Pseudamphimeryx''. While the [[nasal bone]] is not as well-preserved in ''Amphimeryx'' fossils, the frontonasal suture is implied to have formed a W shape on the skull's upper surface like that of ''Pseudamphimeryx''. Both amphimerycid genera also have similar, although not identical, medial positions of the [[infraorbital foramen]] in the maxilla. The [[palatine bone]]s of ''Amphimeryx'' and ''Pseudamphimeryx'' are narrower at their front than back ends.<ref name="reconstruction"/>

The mandible of ''Pseudamphimeryx'' is undulated at the lower edge of its horizontal branch, or the mandibular corpus, and, like in ''Amphimeryx'', has a large and slightly rounded angular border. The [[coronoid process of the mandible]] is positioned lower in relation to the overall skull unlike in ruminants, and the [[temporomandibular joint]] is also lower than in ''Amphimeryx''.<ref name="reconstruction"/><ref name="endemic"/>

''Pseudamphimeryx'' is also known from a brain [[endocast]], although the endocasts of it and ''Amphimeryx'' were not as closely described in detail. Its [[neocortex]] was described by Dechaseaux as being of a primitive and simple type in the larger evolutionary scale of artiodactyls.<ref name="reconstruction"/><ref>{{cite journal|last=Dechaseaux|first=Colette|year=1969|title=Les grandes lignes de l'histoire de la fissuration du néopallium des artiodactyles|journal=Comptes rendus hebdomadaires des séances de l'Académie des sciences. D, Sciences naturalles|volume=268|pages=653–655}}</ref>

=== Dentition ===
[[File:Pseudamphimeryx renevieri maxilla dentition drawing.jpg|thumb|upright=0.75|''P. renevieri'' lower dentition]]
The dental formula of the Amphimerycidae is {{DentalFormula|upper=3.1.4.3|lower=3.1.4.3}} for a total of 44 teeth, consistent with the primitive dental formula for early-middle Palaeogene [[placental]] mammals.<ref name="artiodactyles"/><ref>{{cite journal|last1=Lihoreau|first1=Fabrice|last2=Boisserie|first2=Jean-Renaud|last3=Viriot|first3=Laurent|last4=Brunet|first4=Michel|year=2006|title=Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince|journal=Proceedings of the National Academy of Sciences |volume=103|issue=23|pages=8763–8767 |doi=10.1073/pnas.0603126103|pmid=16723392 |pmc=1482652 |bibcode=2006PNAS..103.8763L |doi-access=free }}</ref> The [[canine tooth|canines]] (C/c) are incisiform ([[incisor]] (I/i) form) and therefore differ little with the incisors themselves. The premolars (P/p) are elongated and may generally be separated by [[diastema]]ta (gaps between teeth). The lower premolars have three lobes, or developed areas on their crowns. The upper molars (M/m) are more developed in form and are generally subtriangular in shape, although some may be more rectangular. They have five crescent-shaped ([[selenodont]]) [[tubercle]]s and sometimes a partial [[hypocone]] cusp that may be present in all species.<ref name="artiodactyles"/><ref name="endemic"/> Amphimerycids differ from ruminants, particularly the basal clade [[Tragulina]], in the retentions of their first premolars and their high levels of specialization in their selenodonty and number of cusps in their molars.<ref name="tragulina">{{cite journal|last=Vislobokova|first=Innessa Anatolevna|year=2001|title=Evolution and classification of Tragulina (Ruminantia, Artiodactyla)|journal=Paleontological Journal|pages=69–145|url=https://www.researchgate.net/publication/262698724}}</ref> Their dentitions more closely resemble those of xiphodonts or dacrytheriines than of ruminants.<ref name="endemic"/>

''Pseudamphimeryx'' specifically is diagnosed in part as having moderate diastemata between P<sup>1</sup> and P<sup>2</sup>. P<sub>1</sub> is similarly separated from P<sub>2</sub> by a diastema but is closer to the lower canine. Its upper molars have five tubercles along with a single front [[cingulum (tooth)|cingulum]] each. In the lower molars, the labial cuspids are crescent-shaped whereas the lingual cuspids are subconical. The peak of the crescent formed by the [[metaconid]] and [[entoconid]] cusps is rounder in the molars of ''Pseudamphimeryx'' than in those of ''Amphimeryx'', a diagnostic trait separating the two genera.<ref name="artiodactyles"/><ref name="endemic"/>

In terms of non-diagnostic features of the amphimerycids, both genera have incisors that are shovel-shaped, have sharp edges on their crowns, and have horizontal positions in relation to the dental row. The canines are similar to incisors but differ by their somewhat asymmetrical shapes.<ref name="stehlin"/> P<sup>1</sup> and P<sup>2</sup> have both been described as narrow and elongated, but the former tooth is larger than the latter.<ref name="reconstruction"/> The overall selenodonty and brachyodonty (low-crowned teeth) of amphimerycids suggest that they were adapted towards [[folivorous]] (leaf-eating) dietary habits.<ref name="ungulates">{{cite journal|last=Blondel|first=Cécile|year=2001|title=The Eocene-Oligocene ungulates from Western Europe and their environment|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=168|issue=1–2|pages=125–139|doi=10.1016/S0031-0182(00)00252-2|bibcode=2001PPP...168..125B|url=http://doc.rero.ch/record/20314/files/PAL_E4294.pdf|access-date=2023-08-30|archive-date=2017-08-22|archive-url=https://web.archive.org/web/20170822051127/http://doc.rero.ch/record/20314/files/PAL_E4294.pdf|url-status=live}}</ref>

=== Postcranial skeleton ===
According to Sudre and Cécile Blondel in 1995 and Erfurt and Métais in 2007, there are three reports of postcranial fossils classified to ''Pseudamphimeryx'': a "cubonavicular" bone (fused [[cuboid bone]] and [[navicular bone]] of the hind legs) of ''P. pavloviae'' from La Bouffie plus ''P. salesmei'' from Salesmes and an [[talus bone|astragalus]] of ''P. renevieri'' from the French commune of Euzet. The latter fossil is suggested to prove the presence of a fused cubonavicular bone in ''P. renevieri''. The fused cubonavicular bone trait has also been reported in ''Amphimeryx'', which appeared after ''Pseudamphimeryx'' and is known from postcranial fossils from multiple localities, and is also generally a defining trait of ruminants in an instance of [[parallel evolution]].<ref name="endemic"/><ref>{{cite journal|last1=Sudre|first=Jean|last2=Blondel|first2=Cécile|date=1995|title=Le tarse des Amphimerycidae d'Europe — Paraphylie des Ruminantia?|journal=Geobios|volume=30|pages=43|doi=10.1016/S0016-6995(97)80068-X}}</ref>

The later relative ''Amphimeryx'', unlike ''Pseudamphimeryx'', is known by complete hind leg evidence including the cubonavicular bone. The overall morphology of the hind leg's bones are reminiscent of those of derived (including extant) ruminants. More specifically, ''Amphimeryx'' was functionally didactyl (two-toed) because, as in derived ruminants, its two middle toes, making up a single [[cannon bone]], are elongated while its two side digits are greatly reduced. On the other hand, ''Amphimeryx'' differs from ruminants by the primitive morphology of the astragalus.<ref name="astragalus1">{{cite journal|last1=Sudre|first1=Jean|last2=Martinez|first2=Jean-Noël|year=1995|title=The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass|journal=Lethaia|volume=28|issue=3|pages=197–209|doi=10.1111/j.1502-3931.1995.tb01423.x|bibcode=1995Letha..28..197M }}</ref><ref name="artiodactyles"/>

=== Size ===
The Amphimerycidae consists only of small-sized species within ''Amphimeryx'' and ''Pseudamphimeryx''.<ref name="endemic"/> According to Blondel, amphimerycid species would have ranged from {{cvt|0.4|kg}} to {{cvt|1.5|kg}} total.<ref name="ungulates">{{cite journal|last=Blondel|first=Cécile|year=2001|title=The Eocene-Oligocene ungulates from Western Europe and their environment|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=168|issue=1–2|pages=125–139|doi=10.1016/S0031-0182(00)00252-2|bibcode=2001PPP...168..125B|url=http://doc.rero.ch/record/20314/files/PAL_E4294.pdf|access-date=2023-08-30|archive-date=2017-08-22|archive-url=https://web.archive.org/web/20170822051127/http://doc.rero.ch/record/20314/files/PAL_E4294.pdf|url-status=live}}</ref> Similarly, Hooker et al. stated that ''Pseudamphimeryx'' was a tiny artiodactyl genus that weighed less than {{cvt|1|kg}} total.<ref>{{cite book|editor-last1=Benton|editor-first1=Michael James|editor-last2=Cook|editor-first2=E.|editor-last3=Hooker|editor-first3=Jerry J.|last1=Hooker|first1=Jerry J.|last2=Cook|first2=E.|last3=Benton|first3=Michael James|year=2005|title=Mesozoic and Tertiary Fossil Mammals and Birds of Great Britain|chapter=British Tertiary fossil mammal GCR sites|publisher=Joint Nature Conservation Committee|pages=68–124|url=https://data.jncc.gov.uk/data/a110a681-fb60-4cc1-ad7d-87cd7878ae4f/gcr-v32-mesozoic-tertiary-mammals-birds-c3.pdf}}</ref> In comparison, ''Amphimeryx'', while still small-sized compared to most other Palaeogene artiodactyls, was larger with estimated weights of {{cvt|1.846|kg}} based on its M<sub>1</sub> and {{cvt|1.511|kg}} based on the astragalus.<ref name="astragalus1"/>

Some species of ''Pseudamphimeryx'' had been differentiated based on size in addition to morphology, with Sudre differing ''P. pavloviae'' from ''P. renevieri'' (both of which coexisted with each other) by the former being larger in size and having more elongated premolars. Hooker and Weidmann suggested that Sudre's measures for proportional sizes between the two species could be potentially challenged by the variations in dental morphology and gaps in quantitative analyses. Therefore, they argued that additional statistical analyses need to be conducted that identify and separate different molar types (first to third molars) to better represent species size differences.<ref name="artiodactyles"/><ref name="mormont"/>

== Palaeoecology ==
{{further|Mammal Palaeogene zones}}

[[File:Middle Eocene Paleogeography Tethys Dispersals.jpg|thumb|left|[[Palaeogeography]] of Europe and Asia during the middle Eocene with possible artiodactyl and perissodactyl dispersal routes.]]
For much of the Eocene, a [[greenhouse effect|hothouse climate]] climate with humid, tropical environments with consistently high precipitations prevailed. Modern mammalian orders including the [[Perissodactyla]], Artiodactyla, and [[Primates]] (or the suborder Euprimates) appeared already by the early Eocene, diversifying rapidly and developing dentitions specialized for folivory. The omnivorous forms mostly either switched to folivorous diets or went extinct by the middle Eocene (47–37 Ma) along with the archaic "[[condylarths]]". By the late Eocene (approx. 37–33 mya), most of the ungulate form dentitions shifted from [[bunodont]] (or rounded) cusps to cutting ridges (i.e. lophs) for folivorous diets.<ref name="evolution">{{cite journal|last1=Eronen|first1=Jussi T.|last2=Janis|first2=Christine M.|last3=Chamberlain|first3=Charles Page|last4=Mulch|first4=Andreas|year=2015|title=Mountain uplift explains differences in Palaeogene patterns of mammalian evolution and extinction between North America and Europe|journal=Proceedings of the Royal Society B: Biological Sciences |volume=282|number=1809|page=20150136 |doi=10.1098/rspb.2015.0136|pmid=26041349 |pmc=4590438 }}</ref><ref name="chiroptera">{{cite journal|last=Maitre|first=Elodie|year=2014|title=Western European middle Eocene to early Oligocene Chiroptera: systematics, phylogeny and palaeoecology based on new material from the Quercy (France)|journal=[[Swiss Journal of Palaeontology]]|volume=133|issue=2 |pages=141–242|doi=10.1007/s13358-014-0069-3|s2cid=84066785 |doi-access=free|bibcode=2014SwJP..133..141M }}</ref>

Land connections between western Europe and North America were interrupted around 53 Ma. From the early Eocene up until the [[Grande Coupure]] extinction event (56–33.9 mya), western Eurasia was separated into three landmasses: western Europe (an archipelago), [[Balkanatolia]] (in-between the [[Paratethys Sea]] of the north and the [[Neotethys Ocean]] of the south), and eastern Eurasia.<ref name="balkanatolia">{{cite journal|last1=Licht|first1=Alexis|last2=Métais|first2=Grégoire|last3=Coster|first3=Pauline|last4=İbilioğlu|first4=Deniz|last5=Ocakoğlu|first5=Faruk|last6=Westerweel|first6=Jan|last7=Mueller|first7=Megan|last8=Campbell|first8=Clay|last9=Mattingly|first9=Spencer|last10=Wood|first10=Melissa C.|last11=Beard|first11=K. Christopher|year=2022|title=Balkanatolia: The insular mammalian biogeographic province that partly paved the way to the Grande Coupure|journal=Earth-Science Reviews|volume=226|page=103929 |doi=10.1016/j.earscirev.2022.103929|bibcode=2022ESRv..22603929L |doi-access=free}}</ref> The [[Holarctic]] mammalian faunas of western Europe were therefore mostly isolated from other landmasses including Greenland, Africa, and eastern Eurasia, allowing for endemism to develop.<ref name="chiroptera"/> Therefore, the European mammals of the late Eocene (MP17–MP20 of the Mammal Palaeogene zones) were mostly descendants of endemic middle Eocene groups.<ref name="equoids">{{cite journal|last1=Badiola|first1=Ainara|last2=Perales-Gogenola|first2=Leire|last3=Astibia|first3=Humberto|last4=Suberbiola|first4=Xabier Pereda|year=2022|title=A synthesis of Eocene equoids (Perissodactyla, Mammalia) from the Iberian Peninsula: new signs of endemism|journal=Historical Biology|volume=34|issue=8|pages=1623–1631|doi=10.1080/08912963.2022.2060098|bibcode=2022HBio...34.1623B |s2cid=248164842 }}</ref>

The Amphimerycidae, and by extent the first genus ''Pseudamphimeryx'', is first recorded by the appearance of ''P. schlosseri'' in the Swiss locality of Egerkingen α + β, dating back to MP14.<ref name="turnover"/><ref name="MP">{{cite book|last1=Aguilar|first1=Jean-Pierre|last2=Legendre|first2=Serge|last3=Michaux|first3=Jacques|year=1997|title=Actes du Congrès Bio-chroM'97. Mémoires et Travaux de l'EPHE Institut de Montpellier 21|chapter=Synthèses et tableaux de corrélations|publisher=École Pratique des Hautes Études-Sciences de la Vie et de la Terre, Montpellier|language=french|pages=769–850|url=https://www.researchgate.net/publication/286785439}}</ref><ref name="reference">{{cite book|last1=Schmidt-Kittler|first1=Norbert|last2=Godinot|first2=Marc|last3=Franzen|first3=Jens L.|last4=Hooker|first4=Jeremy J.|year=1987|chapter=European reference levels and correlation tables|title=Münchner geowissenschaftliche Abhandlungen A10|publisher=Pfeil Verlag, München|pages=13–31|url=https://www.researchgate.net/publication/234056546}}</ref> Both families would have coexisted with perissodactyls ([[Palaeotheriidae]], [[Lophiodontidae]], and [[Hyrachyidae]]), non-endemic artiodactyls ([[Dichobunidae]] and [[Tapirulidae]]), endemic European artiodactyls ([[Choeropotamidae]], Cebochoeridae, and Anoplotheriidae), and primates ([[Adapidae]]).<ref name="ungulates"/><ref name="turnover"/><ref>{{cite journal|last1=Bai|first1=Bin|last2=Wang|first2=Yuan-Qing|last3=Theodor|first3=Jessica M.|last4=Meng|first4=Jin|year=2023|title=Small artiodactyls with tapir-like teeth from the middle Eocene of the Erlian Basin, Inner Mongolia, China|journal=Frontiers in Earth Science|volume=11|pages=1–20|doi=10.3389/feart.2023.1117911 |bibcode=2023FrEaS..1117911B |doi-access=free }}</ref> The [[stratigraphic]] ranges of the early species of ''Amphimeryx'' also overlapped with [[metatheria]]ns ([[Herpetotheriidae]]), [[cimolesta]]ns ([[Pantolestidae]], [[Paroxyclaenidae]]), rodents ([[Ischyromyidae]], [[Theridomyoidea]], [[Gliridae]]), [[eulipotyphla]]ns, bats, [[apatotheria]]ns, [[carnivoraformes]] ([[Miacidae]]), and [[hyaenodont]]s ([[Hyainailourinae]], [[Proviverrinae]]).<ref name="MP"/> Other MP13-MP14 sites have also yielded fossils of turtles and [[Crocodylomorpha|crocodylomorphs]],<ref name="sebecid">{{cite journal|last1=Martin|first1=Jeremy E.|last2=Pochat-Cottilloux|first2=Yohan |last3=Laurent|first3=Yves|last4=Perrier|first4=Vincent|last5=Robert|first5=Emmanuel|last6=Antoine|first6=Pierre-Olivier|year=2022|title=Anatomy and phylogeny of an exceptionally large sebecid (Crocodylomorpha) from the middle Eocene of southern France|journal=Journal of Vertebrate Paleontology|volume=42|issue=4|doi=10.1080/02724634.2023.2193828|bibcode=2022JVPal..42E3828M |s2cid=258361595 }}</ref> and MP13 sites are stratigraphically the latest to have yielded remains of the bird clades [[Gastornithidae]] and [[Palaeognathae]].<ref>{{cite conference|last1=Buffetaut|first1=Eric|last2=Angst|first2=Delphine|year=2014|title=Stratigraphic Distribution of Large Flightless Birds in the Palaeogene of Europe|conference=STRATI 2013: First International Congress on Stratigraphy At the Cutting Edge of Stratigraphy|doi=10.1007/978-3-319-04364-7_190}}</ref>

In addition to ''P. schlosseri'', other mammals that appeared in Egerkingen α + β include the herpetotheriid ''[[Amphiperatherium]]'', ischyromyids ''[[Ailuravus]]'' and ''[[Plesiarctomys]]'', [[pseudosciurid]] ''[[Treposciurus]]'', [[omomyid]] ''[[Necrolemur]]'', adapid ''[[Leptadapis]]'', proviverrine ''[[Proviverra]]'', palaeotheres (''[[Propalaeotherium]]'', ''[[Anchilophus]]'', ''[[Lophiotherium]]'', ''[[Plagiolophus (mammal)|Plagiolophus]]'', ''[[Palaeotherium]]''), hyrachyid ''[[Chasmotherium]]'', lophiodont ''[[Lophiodon]]'', dichobunids ''[[Hyperdichobune]]'' and ''Mouillacitherium'', choeropotamid ''[[Rhagatherium]]'', anoplotheriid ''[[Catodontherium]]'', cebochoerid ''[[Cebochoerus]]'', tapirulid ''Tapirulus'', mixtotheriid ''[[Mixtotherium]]'', and the xiphodonts ''[[Dichodon (mammal)|Dichodon]]'' and ''[[Haplomeryx]]''.<ref name="MP"/>

The unit MP16 records the appearances of ''P. renevieri'' and ''P. pavloviae'', both of which are recorded from the MP16 French locality of Robiac. Other mammal genera that cooccur in the site include the herpetotheriids ''Amphiperatherium'' and ''[[Peratherium]]'', [[apatemyid]] ''[[Heterohyus]]'', [[nyctitheriid]] ''[[Saturninia]]'', rodents (''[[Glamys]]'', ''[[Elfomys]]'', ''[[Plesiarctomys]]'', ''[[Ailuravus]]'', ''[[Remys]]''), [[omomyid]]s ''[[Pseudoloris]]'' and ''Necrolemur'', adapid ''[[Adapis]]'', hyaenodonts ''[[Paroxyaena]]'' and ''[[Cynohyaenodon]]'', carnivoraformes ''[[Paramiacis]]'' and ''[[Quercygale]]'', palaeotheres (''[[Propalaeotherium]]'', ''[[Anchilophus]]'', ''[[Plagiolophus (mammal)|Plagiolophus]]'', ''[[Pachynolophus]]'', ''[[Palaeotherium]]''), lophiodont ''[[Lophiodon]]'', hyrachyid ''[[Chasmotherium]]'', cebochoerids ''[[Acotherulum]]'' and ''Cebochoerus'', choeropotamid ''[[Choeropotamus]]'', tapirulid ''Tapirulus'', anoplotheriids (''Dacrytherium'', ''[[Catodontherium]]'', ''[[Robiatherium]]''), robicinid ''[[Robiacina]]'', and xiphodonts (''[[Xiphodon]]'', ''Dichodon'', ''Haplomeryx'').<ref name="MP"/>

After MP16, a [[faunal turnover]] occurred, marking the disappearances of the lophiodonts and European hyrachyids as well as the extinctions of all European crocodylomorphs except for the alligatoroid ''[[Diplocynodon]]''.<ref name="turnover"/><ref name="sebecid"/><ref>{{cite journal|last=Martin|first=Jeremy E.|year=2015|title=A sebecosuchian in a middle Eocene karst with comments on the dorsal shield in Crocodylomorpha|journal=Acta Palaeontologica Polonica|volume=60|issue=3|pages=673–680|doi=10.4202/app.00072.2014|s2cid=54002673 |doi-access=free}}</ref><ref>{{cite journal|last=Antunes|first=Miguel Telles|year=2003|title=Lower Paleogene Crocodilians from Silveirinha, Portugal|journal=Palaeovertebrata|pages=1–26|volume=32|url=https://palaeovertebrata.com/articles/keyword/476}}</ref> The causes of the faunal turnover have been attributed to a shift from humid and highly tropical environments to drier and more temperate forests with open areas and more abrasive vegetation. The surviving herbivorous faunas shifted their dentitions and dietary strategies accordingly to adapt to abrasive and seasonal vegetation.<ref>{{cite journal|last1=Robinet|first1=Céline|last2=Remy|first2=Jean Albert|last3=Laurent|first3=Yves|last4=Danilo|first4=Laure|last5=Lihoreau|first5=Fabrice|year=2015|title=A new genus of Lophiodontidae (Perissodactyla, Mammalia) from the early Eocene of La Borie (Southern France) and the origin of the genus ''Lophiodon'' Cuvier, 1822|journal=Geobios|volume=48|issue=1|pages=25–38|doi=10.1016/j.geobios.2014.11.003|bibcode=2015Geobi..48...25R }}</ref><ref>{{cite journal|last1=Perales-Gogenola|first1=Leire|last2=Badiola|first2=Ainara|last3=Gómez-Olivencia|first3=Asier|last4=Pereda-Suberbiola|first4=Xabier|year=2022|title=A remarkable new paleotheriid (Mammalia) in the endemic Iberian Eocene perissodactyl fauna|journal=Journal of Vertebrate Paleontology|volume=42|issue=4|doi=10.1080/02724634.2023.2189447|bibcode=2022JVPal..42E9447P |s2cid=258663753 }}</ref> However, the environments were still subhumid and covered by subtropical evergreen forests. The Palaeotheriidae was the sole remaining European perissodactyl group, and frugivorous-folivorous or purely folivorous artiodactyls became the dominant group in western Europe.<ref name="Evolution of European carnivorous mammal assemblages">{{cite journal|last1=Solé|first1=Floréal|last2=Fischer|first2=Valentin|last3=Le Verger|first3=Kévin|last4=Mennecart|first4=Bastien|last5=Speijer|first5=Robert P.|last6=Peigné|first6=Stéphane|last7=Smith|first7=Thierry|year=2022|title=Evolution of European carnivorous mammal assemblages through the Paleogene|journal=Biological Journal of the Linnean Society|volume=135|issue=4|pages=734–753|doi=10.1093/biolinnean/blac002}}</ref><ref name="ungulates"/>

The late Eocene unit MP17 records as many as four total species of ''Pseudamphimeryx'': ''P. renevieri'', ''P. havloviae'', ''P. salesmei'', and ''P. hantonensis''.<ref name="reference"/><ref name="pondaung">{{cite journal|last=Métais|first=Grégoire|year=2006|title=New basal selenodont artiodactyls from the Pondaung Formation (late middle Eocene, Myanmar) and the phylogenetic relationships of early ruminants|journal=Annals of Carnegie Museum|volume=75|number=1|pages=51–67|doi=10.2992/0097-4463(2006)75[51:NBSAFT]2.0.CO;2}}</ref> MP17a confirms the continued occurrence of ''P. renevieri'' in the French locality of Fons 4; MP17b is the latest unit that ''Pseudamphimeryx'' occurs and records both ''P. renevieri'' and ''P. pavloviae'' from another French locality of Perrière. Starting at MP18, ''Amphimeryx'' makes its first appearance and therefore succeeds ''Pseudamphimeryx''.<ref name="MP"/><ref name="reference"/> In Perrière, ''Pseudamphimeryx'' fossils have been found along with those of the herpetotheriids ''Peratherium'' and ''Amphiperatherium'', [[pseudorhyncocyonid]] ''[[Pseudorhyncocyon]]'', apatemyid ''Heterohyus'', nyctitheriid ''Saturninia'', various rodents and bats, omomyids ''Pseudoloris'' and ''[[Microchoerus]]'', adapid ''[[Leptadapis]]'', [[hyaenodontid]] ''[[Hyenodon]]'', [[miacid]] ''Quercygale'', palaeotheres (''[[Lophiotherium]]'', ''Palaeotherium'', and ''Plagiolophis''), dichobunid ''Mouillacitherium'', cebochoerid ''Acotherulum'', mixtothere ''Mixtotherium'', anoplotheriid ''Dacrytherium'', tapirulid ''Tapirulus'', and the xiphodonts ''Dichodon'' and ''Haplomeryx''.<ref name="MP"/>

== Notes ==
{{Notelist}}


== References ==
== References ==

Latest revision as of 00:20, 29 November 2024

References

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