[1] In 1988, based on additional fossil materials from Le Bretou as well as older Quercy collections from the University of Montpellier, he relocated P. cournovense into its own genus Robiatherium, classified within the Anoplotheriidae.

[3] Some researchers considered the selenodont families Anoplotheriidae, Xiphodontidae, and Cainotheriidae to be within Tylopoda due to postcranial features that were similar to the tylopods from North America in the Palaeogene.

[4] 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.

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.

[10] The phylogenetic tree published in the article and another work about the cainotherioids is outlined below:[11] Eurodexis russelli Dichobune leporina Amphimeryx murinus Xiphodon castrense Paratoceras coatesi Eotylopus reedi Parvitragulus priscus Lophiomeryx chalaniati Archaeomeryx optatus Mixtotherium cuspidatum Anoplotherium latipes Dacrytherium ovinum Robiacina lavergnesis Robiacina minuta Robiacina quercyi Palembertina deplasi Paroxacron bergeri Paroxacron valdense Oxacron courtoisii Cainotherium laticurvatum Caenomeryx filholi Caenomeryx procommunis Plesiomeryx cadurcensis 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.

The phylogenetic tree as produced by the authors is shown below:[9] Bunophorus Gunophorus Diacodexis Protodichobune Eurodexis Buxobune Mouillacitherium Meniscodon Hyperdichobune Dichobune robertiana Dichobune leporina Homacodon Gobiohyus Khirtharia Entelodon Palaeocheorus Perchoerus Haplobunodon Cuisitherium Lophiobunodon Mixtotherium Robiacina Dacrytherium Diplobune Xiphodon Paraxiphodon Cainotherium Paroxacron Archaeomeryx Amphimeryx Pseudamphimeryx Aumelasia Hallebune Amphirhagatherium Cebochoerus Gervachoerus Choeropotamus Siamotherium The Xiphodontidae is characterized in part by the elongated premolars (P/p), molariform P4 teeth, upper molars (M/m) with 4 to 5 crescent-shaped cusps, and selenodont (crescent-shaped ridges) lower molars with 4 ridges, compressed lingual cuspids, and crescent-shaped labial cuspids.

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.

[19]< Other mammal groups present in the Late Eocene of western Europe represented the leptictidans (Pseudorhyncocyonidae),[20] primates (Adapoidea and Omomyoidea),[21] eulipotyphlans (Nyctitheriidae),[22] chiropterans,[13] herpetotheriids,[23] apatotherians,[24] and endemic rodents (Pseudosciuridae, Theridomyidae, and Gliridae).

[26] In addition to snakes, frogs, and salamandrids, rich assemblage of lizards are known in western Europe as well from MP16-MP20, representing the Iguanidae, Lacertidae, Gekkonidae, Agamidae, Scincidae, Helodermatidae, and Varanoidea.

[27] Within the MP17a locality of Fons 4, Paraxiphodon is known to have coexisted with the likes of the herpetotheriids Amphiperatherium and Peratherium, glirid Glamys, theridomyid Elfomys, omomyid Necrolemur, hyaenodont Hyaenodon, palaeotheres (Anchilophus, Lophiotherium, Pachynolophus, Plagiolophus, Palaeotherium), dichobunid Mouillacitherium, cebochoerid Cebochoerus, choeropotamid Choeropotamus, anoplotheriid Dacrytherium, and other xiphodonts (Xiphodon, Dichodon, Haplomeryx).