It and other xiphodont genera went extinct by the Grande Coupure extinction/faunal turnover event, coinciding with shifts towards further glaciation and seasonality plus dispersals of Asian immigrant faunas into western Europe.

The causes of its extinction are attributed to negative interactions with immigrant faunas (resource competition, predation), environmental turnover from climate change, or some combination of the two.

In 1848, after having recognized ungulates as a taxonomic group defined by the Artiodactyla and Perissodactyla, British naturalist Richard Owen erected the genus Dichodon based on its "peculiar" dentition, classifying it as a member of the former.

[3] In 1852, German palaeontologist Christian Erich Hermann von Meyer, writing to his colleague Heinrich Georg Bronn, told of fossils of Dichodon from the locality of Frohnstetten whose dentition did not resemble that of the species D. cuspidatus.

[5][6] The same year, British naturalist William Henry Flower expressed doubt regarding whether Dichodon was distinct enough from Xiphodon based on the different last premolar morphologies.

[13] All species of Dichodon previously recognized as valid since Stehlin's 1910 revisions were listed by Jerry J. Hooker in 1986, although he emended D. subtile to D. subtilis and D. frohnstettense to D. frohnstettensis out of correcting naming incongruencies.

[14] In 1988, Sudre established another species named D. vidalenci based on isolated teeth from Le Bretou in France, which he noted had very elongated premolars, and listed Dichodon sp.

[21] The phylogenetic relations of the Xiphodontidae as well as the Anoplotheriidae, Mixtotheriidae and Cainotheriidae have been elusive due to the selenodont morphologies (or having crescent-shaped ridges) of the molars, which were convergent with tylopods or ruminants.

[22] 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.

[17] 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 (the latter family is represented only by Xiphodon in the cladogram).

[25] The phylogenetic tree published in the article and another work about the cainotherioids is outlined below:[26] 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 2022, Weppe created a phylogenetic analysis in his academic thesis regarding Palaeogene artiodactyl lineages, focusing most specifically on the endemic European families.

The result, Weppe mentioned, matches up with previous phylogenetic analyses on the Cainotherioidea with other endemic European Palaeogene artiodactyls that support the families as a clade.

Within the Xiphodontidae, Weppe's phylogeny tree classified Haplomeryx as a sister taxon to the clade consisting of Xiphodon plus Dichodon, making the latter two close relatives.

[27] The mandible of Dichodon can resemble that of the anoplotheriid Dacrytherium but differs by the front, or body, portion being rectilinear in shape and the reduction of the convex form within the dental row.

[27] This is part of the problem behind the relatively incomplete anatomical record of the genus itself, but Dechaseaux determined that the skull of Dichodon would have resembled those of the Palaeogene camelid Poebrotherium and the oromerycid Protylopus.

[31] The known brain endocast (natural brain-shaped cast) of Dichodon is only partial, consisting of a front region with a left olfactory bulb and a back area.

[27] Both Xiphodon and Dichodon display complete sets of 3 three incisors, 1 canine, 4 premolars, and 3 molars on each half of the upper and lower jaws,[27][29] consistent with the primitive placental mammal dental formula of 3.1.4.33.1.4.3 for a total of 44 teeth.

[17] The larger-sized species compose of D. cervinum, D. cuspidatum, D. stehlini, and D. biroi while the others, namely D. frohnstettensis, D. simplex, D. subtilis, D. cartieri, D. lugdunensis, and D. ruetimeyeri, are smaller-sized.

[17][35] In 2019, Helder Gomes Rodriguez et al. published weight estimates of Palaeogene artiodactyls including Xiphodon, calculated from dental measurements or those of astragali, but not but not the other xiphodont genera Dichodon and Haplomeryx.

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.

[40] 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.

[34][19][43] The stratigraphic ranges of the early species of Dichodon also overlapped with metatherians (Herpetotheriidae), cimolestans (Pantolestidae, Paroxyclaenidae), rodents (Ischyromyidae, Theridomyoidea, Gliridae), eulipotyphlans, bats, apatotherians, carnivoraformes (Miacidae), and hyaenodonts (Hyainailourinae, Proviverrinae).

[45] In the Egerkingen α + β locality, D. cartieri fossils occur with those of the herpetotheriid Amphiperatherium, ischyromyids Ailuravus and Plesiarctomys, pseudosciurid Treposciurus, omomyid Necrolemur, adapid Leptadapis, proviverrine Proviverra, palaeotheres (Propalaeotherium, Anchilophus, Lophiotherium, Plagiolophus, Palaeotherium), hyrachyid Chasmotherium, lophiodont Lophiodon, dichobunids Hyperdichobune and Mouillacitherium, choeropotamid Rhagatherium, anoplotheriid Catodontherium, amphimerycid Pseudamphimeryx, cebochoerid Cebochoerus, tapirulid Tapirulus, mixtotheriid Mixtotherium, and the xiphodont Haplomeryx.

[15][21] Dichodon is recorded in Le Bretou along with the herpetotheriids Amphiperatherium and Peratherium, pseudorhyncocyonid Leptictidium, nyctitheriids Cryptotopos and Saturninia, notharctid Anchomomys, omomyid Necrolemur, rodents (Elfomys, Glamys, Paradelomys, Remys, Sciuroides), bats (Carcinipteryx, Hipposideros, Palaeophyllophora, Vaylatsia), proviverrine Allopterodon, carnivoraformes Quercygale and Paramiacis, palaeotheres (Anchilophus, Plagiolophus, Palaeotherium), lophiodont Lophiodon, cebochoerids Acotherulum and Cebochoerus, anoplotheriids (Catodontherium, Dacrytherium, Robiatherium), dichobunids Dichobune and Mouillacitherium, amphimerycid Pseudamphimeryx, robiacinid Robiacina, tapirulid Tapirulus, and the other xiphodonts Xiphodon and Haplomeryx.

[19][44][47][48] 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.

[51][34] The late Eocene records two species of Dichodon that are exclusive to single localities, namely D. cuspidatum at the Hordle Cliff (MP17) and D. stehlini from La Débruge (MP18).

[53] In the MP19 locality of Escamps, D. frohnstettensis is recorded to have cooccurred with the likes of the herpetotheriids Amphiperatherium and Peratherium, pseudorhyncocyonid Pseudorhyncocyon, nyctitheres Saturninia and Amphidozotherium, bats (Hipposideros, Vaylatsia, Stehlinia), theridomyids (Paradelomys, Elfomys, Blainvillimys, Theridomys), adapid Palaeolemur, hyainailourine Pterodon, amphicyonid Cynodictis, palaeotheres Palaeotherium and Plagiolophus, dichobunid Dichobune, choeropotamid Choeropotamus, anoplotheriids Anoplotherium and Diplobune, cainotheres Oxacron and Paroxacron, amphimerycid Amphimeryx, and the other xiphodonts Xiphodon and Haplomeryx.

The Turgai Strait, which once separated much of Europe from Asia, is often proposed as the main European seaway barrier prior to the Grande Coupure, but some researchers challenged this perception recently, arguing that it completely receded already 37 Ma, long before the Eocene-Oligocene transition.

[21][55][17] The extinctions of Dichodon and many other mammals have been attributed to negative interactions with immigrant faunas (competition, predations), environmental changes from cooling climates, or some combination of the two.