The Microbunodon Event in the late Oligocene, however, led to its extinction as it faced a combination of a warming climate plus subsequent habitat turnover and competition from a new wave of migrating species.

[9][10][11] Genevieve Bouvrain and Denis Geraads reviewed Bachitherium as a genus in 1984, examining the cast of a sub-complete skeleton from the Oligocene limestone locality of Cereste, France in addition to previously collected Quercy materials.

[14] In 1987, the British palaeontologist Christine Marie Janis wrote a journal questioning and revising traguline clades such as Bachitherium, in which the recent discovery of the complete skeleton of the genus and her investigation of the European dental material of it could enable a reassessment of the ruminant.

[16] In 2008, Jan van der Made reviewed the Oschiri fauna from the Mediterranean island of Sardinia, which dates back to MN3 (the early Miocene, or within the Burdigalian), or some 20 Ma.

[9] In 2017, Mennecart et al. said that the islands of Sardinia and Corsica separated from the mainland by the early Miocene, in which then the Sandinian insular Neogene fossils represented the oldest case of endemism in the Mediterranean Sea.

However, they also warned that except for Sardomeryx oschiriensis, the assigned names are to be taken with caution since the materials are generally fragmented and mainly based on postcranial remains, which most often are prone to insular adaptations from the now-extinct animals.

[19] The researchers also reviewed reports of the supposed previously oldest Bachitheriidae from the German localities of Herrlingen1, Möhren13, Ronheim1, and Weinheim (Palaeontological Museum, Munich) that date back to 32.5 Ma (MP22).

The Tragulidae (its members commonly known as "chevrotains" or "mouse deer") is the only extant family of the infraorder and are, as a result, considered living fossils, since they had changed little in the evolutionary record.

[19][23][24] Several researchers such as Innessa Anatolevna Vislobokova have considered the two superfamilies within the infraorder, the Traguloidea (Tragulidae, Gelocidae, Leptomerycidae, Archaeomerycidae, Lophiomerycidae, Bachitheriidae) and Hypertraguloidea (Hypertragulidae, Praetragulidae), to be valid.

[26][27][28] In 2015, Bastien Mennecart and Grégoire Métais created a hypothesis on the phylogenetic relationships of Oligocene ruminants by compiling a matrix of 40 dental, cranial, and postcranial features known from them.

The taxa included in the analysis are 20 ruminant species representative of the European and Asian "Gelocidae" (a known wastebasket family), Bachitheriidae, late Oligocene or early Miocene Pecora of ambiguous affinities, Lophiomerycidae, Tragulidae, Leptomerycidae, Archaeomerycidae, and Hypertragulidae.

Below are two phylogenetic trees of the defined Oligocene ruminants, the first based on a 50% majority consensus and the second based on a strict consensus:[29] Archaeomeryx optatus Miomeryx altaicus Leptomeryx evansi Hypertragulus calcaratus Lophiomeryx chalaniati Gelocus communis Archaeotragulus krabiensis Iberomeryx minor Notomeryx besensis Indomeryx cotteri Bachitherium curtum Bachitherium insigne Gobiomeryx dubius Mosaicomeryx quercyi Prodremotherium elongatum Pseudomeryx gobiensis Amphitragulus elegans Amphitragulus quercyi Dremotherium guthi Dremotherium feignouxi Archaeomeryx optatus Leptomeryx evansi Hypertragulus calcaratus Notomeryx besensis Indomeryx cotteri Miomeryx altaicus Lophiomeryx chalaniati Gelocus communis Archaeotragulus krabiensis Iberomeryx minor Bachitherium curtum Bachitherium insigne Gobiomeryx dubius Mosaicomeryx quercyi Prodremotherium elongatum Amphitragulus elegans Amphitragulus quercyi Dremotherium guthi Dremotherium feignouxi Pseudomeryx gobiensis Mennecart and Métais stated that the systematic position of the monogeneric family Bachitheriidae is somewhat problematic since the uncertain phylogenetic position of the Bachitheriidae with other Oligocene ruminants is due to its postcranial and dental features being similar to other ruminant lineages.

Bachitherium is phylogenetically related to other tragulines based on its caniniform P1 and traguloid-shaped astragali, but the selenodont molars and fusion of the carpal bones were probably a result of parallel evolution.

[31] Nonetheless, the complete skeleton and various other remains of Bachitherium allow for distinguishing it as a distinct family compared to other members of the Tragulina infraorder such as the Gelocidae, Lophiomerycidae, Hypertragulidae, Leptomerycidae, and Tragulidae.

The European Tragulidae (including Iberomeryx of the Paleogene and Dorcatherium of the Neogene) and Bachitheriidae are defined by special traguline-shaped lower premolars that feature a lack of metaconids and two elongated parallel cristids forming the edges of the back valley of the cusp.

[9] In September 1995, prior to Sudre's publication on B. guirounetensis, he and Jean-Noël Martinez used the dimensions of the astragali of Paleogene artiodactyls to estimate their body masses, since the astragalus is the most frequently postcranial bone in fossil assemblages from its reduction of vulnerability to fragmentation due to its stocky shape and compact structure.

Therefore, its palaeobiogical niches would have been equvivalent to modern-day chevrotains or duikers (tribe Cephalophini/subfamily Cephalophinae), both of which live in humid wooded habitats in Africa and/or southern Asia with freshwater bank sources.

Based on dental microwear analysis, the diet of B. curtum was closest to those of selective browsers, consuming leaves, fruits, and dicotyledonous herbages that would have been common in humid forested environments.

When alarmed, the species is reported to rush to the nearest river and submerge, swimming upstream, and coming to the surface beneath water banks or overhanging vegetation.

[38] The oldest tragulid, known from the Krabi Basin of southern Thailand as Archaeotragulus, dates back to the late Eocene, further supporting the Tragulidae being the most basal extant ruminant family.

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.

Fossil evidence indicates that the late Eocene mammals of eastern Europe during the Priabonian age include the palaeothere Plagiolophus, the anthracotheres Bakalovia and Prominatherium, the brontotheres Sivatitanops?

curtum with the marsupial Amphiperatherium, rodents (Pseudocricetodon, Paracricetodon), gelocid Gelocus, lophiomerycid Lophiomeryx, cainothere Paroxacron, suoid Doliochoerus, entelodont Entelodon, anthracotheres Anthracotherium and Elomeryx, rhinocerotid Ronzotherium, ursid Cephalogale, amphicyonid Pseudocyonopsis, and hyaenodont Hyaenodon.

The two species were found in the same locality as the marsupial Amphiperatherium (multiple species), nyctitheriid Darbonetus, erinaceid Tetracus, bats, rodents (theridomyids, sciurids, eomyids, cricetids, murids, and glirids), hyaenodonts Hyaenodon and Thereutherium, amphicynodont Amphicynodon, enigmatic feliforms (Stenogale, Stenoplesictis, Palaeogale), nimravid Nimravus, palaeothere Plagiolophus, rhinocerotid Ronzotherium, anoplotheriid Diplobune, cainotheres Plesiomeryx and Caenomeryx, and the tragulid Iberomeryx.

The locality has also recorded multiple nimravids (Quercylurus, Nimravus, Dinailurictis), the feliform Stenoplesictis, palaeothere Plagiolophus, rhinocerotoids (Ronzotherium, Eggysodon, Cadurcotherium), chalicothere Schizotherium, suoid Doliochoerus, dichobunid Metriotherium, cainothere Caenomeryx, anthracothere Anthracotherium, and the lophiomerycid Lophiomeryx.

[60][64] MP25 (middle Oligocene) records the last appearances of the entelodont Entelodon, amynodont Cadurcotherium, palaeothere Plagiolophus, and all Paleogene European nimravids, the latter of which are suggested to have gone extinct by 28 Ma.

[9][64][69] The French locality of Pech Desse, an MP28-dated location with B. lavocati, also has fossil remains of the lophiomerycid Lophiomeryx, anthracothere Paenanthracotherium, pecorans Prodremotherium and "Amphitragulus" quercyi, cainotheres Plesiomeryx and Caenomeryx, hyaenodont Hyaenodon, and the ursid Cyonarctos.

[76][77] Bachitherium is also a focus of further recent efforts within France to promote palaeontological heritage, including as a representation of the post-Grande Coupure faunas of the Quercy fossil record.

More specifically, the Causses du Quercy Geopark's management sought to promote conservation of the Oligocene-aged phosphorite deposits in part by educating nearby inhabitants to understand the generally niche palaeontological heritage in their areas to become the locality's future guarantors.

[78][79] The other animals chosen to represent other areas were the chalicothere Schizotherium ("Limognitherium"), marsupial Peratherium, amphimerycid Pseudamphimeryx, tody Palaeotodus, and two bats of the genus Vaylatsia.