Duerotherium

In 2009, Spanish palaeontologists Miguel-Ángel Cuesta and Ainara Badiola described a newly erected anoplotheriine genus from the Mazaterón Formation near the village of Mazaterón, which are located within the Duero Basin. The genus and type species Duerotherium sudrei was created based on a fragment of a left fragment of a maxilla with a dental series of P3-M3 (specimen STUS 11562), which was deposited in the "Sala de las Tortugas" of the University of Salamanca. The genus etymology derives from the Duero Basin for where the fossil was described plus the Greek / meaning "beast" or "wild animal". The etymology of the species name was dedicated in honour of Jean Sudre for his studies on endemic European Palaeogene artiodactyls. Classification commune'', National Museum of Natural History, France Duerotherium belongs to the Anoplotheriidae, a Palaeogene artiodactyl family endemic to Western Europe that lived from the Middle Eocene to the Early Oligocene (~44 to 30 Ma, possible earliest record at ~48 Ma). The exact evolutionary origin of anoplotheriids remain uncertain, but they were exclusively distributed in Europe when it was an archipelago that was isolated by seaway barriers from other regions such as Balkanatolia and the rest of eastern Eurasia. The Anoplotheriidae's relations with other artiodactyl groups are not well-resolved. The Anoplotheriidae consists of two subfamilies, the Dacrytheriinae and Anoplotheriinae, and Duerotherium belongs to the latter. The Dacrytheriinae is the older subfamily and first appeared in the Middle Eocene (in the Mammal Palaeogene zones unit MP13, possibly up to MP10), although some authors consider them to be a separate family, as Dacrytheriidae. Anoplotheriines made their first appearances by the late Eocene (MP15-MP16; ~41–40 Ma) with Duerotherium and Robiatherium. After a significant gap of anoplotheriines in MP17a-MP17b, the derived anoplotheriids Anoplotherium and Diplobune made their first appearances by MP18, although their exact origins remain unknown. == Description ==

The dental formula of the Anoplotheriidae is for a total of 44 teeth, consistent with the primitive dental formula for early-middle Palaeogene placental mammals. Anoplotheriids have selenodont (crescent-shaped ridge form) or bunoselenodont (bunodont and selenodont) premolars (P/p) and molars (M/m) made for leaf-browsing diets. The canines (C/c) of the Anoplotheriidae are overall undifferentiated from the incisors (I/i). The lower premolars of the family are piercing and elongated. The upper molars are bunoselenodont in form while the lower molars have selenodont labial cuspids and bunodont (or rounded) lingual cuspids. The subfamily Anoplotheriinae differs from the Dacrytheriinae by the molariform premolars with crescent-shaped paraconules and the lower molars that lack a third cusp between the metaconid and entoconid. Duerotherium is diagnosed based on its dental traits based on the maxilla fragment. The P3 (third upper premolar) is elongated mesiodistally (front-to-back) and triangular in shape and has a protocone cusp that is positioned back in relation to the mouth and noticeable talon positioned slightly back. The morphology of the tooth of Duerotherium is similar to the P3 tooth of Dacrytherium based on the positions of the cusps, although the latter differs in being mesiodistally elongated compared to the former. The morphology of P4 is typical of the Anoplotheriinae and has only has one externally-positioned cusp. The upper molars of Duerotherium also have similar morphologies to those of other anoplotheriines. They are bunoselenodont and have large and conical protocone cusps in the near-front of the paracone in the front areas of the teeth. The metaconule is slightly asymmetric, and the postmetaconule ridge is moderate in form. The parastyle and metastyle cusps are divergent, revealing a moderate W-shaped ectoloph ridge. The molars are heterodont and increase in size from M1 to M3. In a top (or occlusal) outline view, the M1 is quadrate in shape while M2-M3 appears more trapezoidal. It differs from each anoplotheriine genus based on various specific morphologies of the molars. Duerotherium is described as a small-sized anoplotheriine that is slightly larger than Robiatherium but smaller than Ephelcomenus. D. sudrei is especially smaller than Anoplotherium and most species of Diplobune. It might be similar in size to Diplobune minor. == Palaeoecology ==

of Europe and Asia during the Middle Eocene with possible artiodactyl and perissodactyl dispersal routes. For much of the Eocene, a hothouse 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 Ma), most of the ungulate form dentitions shifted from bunodont cusps to cutting ridges (lophs) for folivorous diets. Land-based connections to the north of the developing Atlantic Ocean were interrupted around 53 Ma, meaning that North America and Greenland were no longer well-connected to western Europe. From the Early Eocene up until the Grande Coupure extinction event (56–33.9 Ma), the western Eurasian continent was separated into three landmasses: western Europe (an archipelago), Balkanatolia, and eastern Eurasia (Balkanatolia was in between the Paratethys Sea to the north and the Neotethys Ocean to the south). The Mazaterón Formation of the Duero Basin dates to the middle Late Eocene (Robiacian of Europe) and ranges in faunal level from MP15–MP16. Fossils of testudines, crocodilians, rodents, primates, hyaenodonts, artiodactyls, and perissodactyls were collected from the site. The mammalian taxa collected from the Eocene of the Iberian region differ from contemporary faunas in other areas of Europe, supporting the hypothesis of a division of the Iberian Peninsula as a semi-separate bioregion. == References ==