Microchoerus hookeri nov. sp., a new late Eocene European microchoerine (Omomyidae, Primates): New insights on the evolution of the genus Microchoerus

Abstract

The study of Eocene primates is crucial for understanding the evolutionary steps undergone by the earliest members of our lineage and the relationships between extinct and extant taxa. Recently, the description of new material from Spain has improved knowledge of European Paleogene primates considerably, particularly regarding microchoerines. Here we describe the remains of Microchoerus from Sossís (late Eocene, Northern Spain), consisting of more than 120 specimens and representing the richest sample of Microchoerus from Spain. This primate was first documented in Sossís during the 1960s, on the basis of scarce specimens that were ascribed to Microchoerus erinaceus. However, the studied material clearly differs from M. erinaceus at its type locality, Hordle Cliff, and shows some characters that allow the erection of a new species, Microchoerus hookeri. This new species is characterized by its medium size, moderate enamel wrinkling, generally absent mesoconid and small hypoconulid in the M and M, single paracone in the upper molars and premolars and, particularly, by the lack of mesostyle in most M and M, a trait not observed in any other species of Microchoerus. Some specimens from Eclépens B (late Eocene, Switzerland), determined previously to be Microcherus aff. erinaceus, are also ascribed to M. hookeri. M. hookeri represents the first step of a lineage that differentiated from Necrolemur antiquus and, later, gave rise to several unnamed forms of Microchoerus, such as those from Euzet and Perrière, finally leading to M. erinaceus. This discovery sheds new light on the complex evolutionary scheme of Microchoerus, indicating that it is most probably a paraphyletic group. A detailed revision of the age of the localities containing remains of Microchoerus and the description of the still unpublished material from some European localities, are necessary to clarify the phylogenetic relationships among the members of this microchoerine group.

The fossil assemblage from Pontils, a middle Eocene primate-bearing locality from Northeastern Spain

“…Although its incompleteness prevents taking measurements, direct comparison shows that this tooth is larger than those of Necrolemur anadoni from Sant Jaume de Frontanyà-1 (Minwer-Barakat et al, 2015b) and N. aff. anadoni from La Verrerie de Roches (Minwer-Barakat et al, 2017a), similar in size to Necrolemur antiquus from La Bouffie (Godinot, 2003) and smaller than Microchoerus hookeri from Sossís (Minwer-Barakat et al, 2017b). This specimen is therefore identified as Necrolemur sp.…”

A new primate assemblage from La Verrerie de Roches (Middle Eocene, Switzerland)

“…Necrolemur shows size and morphological features that are intermediate between those of Nannopithex and Microchoerus: it mainly differs from Nannopithex in its larger size, more developed hypocone generally connected to the protocone, and double metaconule in the upper molars, wider trigonid and absence of a well developed paraconid in the M 2 and M 3 . Necrolemur can be distinguished from Microchoerus by its smaller size, less accentuated enamel wrinkling, absent or very small mesoconid and hypoconulid in the M 1 and M 2 , less developed metaconules and paraconule, and by the absence of the mesostyle that is present in the upper molars of almost all the species of Microchoerus (with the exception of Microchoerus hookeri, see Minwer-Barakat et al, 2017).…”

“…During the Robiacian, Omomyiformes are represented by the genus Nannopithex and its putative descendant Necrolemur (Minwer- Barakat et al, 2015a), as well as the small-sized and rather diverse genus Pseudoloris. Microchoerus has also been reported from some Robiacian localities, although this genus has recently been suggested to be a paraphyletic group, and the taxonomic allocation of some Middle Eocene forms must be reconsidered (Minwer-Barakat et al, 2017). Regarding the adapiforms, during the Robiacian they are represented in Europe by the anchomomyins Anchomomys cf.…”

Agerinia marandati sp. nov., a new early Eocene primate from the Iberian Peninsula, sheds new light on the evolution of the genus Agerinia

“…Recent works dealing with European Eocene primates have focused on the description of new material (Hooker, 2007; Hooker, 2012; Hooker & Harrison, 2008; Marigó, Minwer-Barakat & Moyà-Solà, 2011; Marigó, Minwer-Barakat & Moyà-Solà, 2013; Gebo, Smith & Dagosto, 2012; Gebo et al, 2015; Minwer-Barakat, Marigó & Moyà-Solà, 2012; Minwer-Barakat et al, 2013; Femenias-Gual et al, 2015), the revision of previous taxonomic assignations (Minwer-Barakat, Marigó & Moyà-Solà, 2013; Minwer-Barakat, Marigó & Moyà-Solà, 2016; Marigó et al, 2014) and the establishment of relationships between different taxa (Smith, Rose & Gingerich, 2006; Marigó, Minwer-Barakat & Moyà-Solà, 2010; Marigó, Minwer-Barakat & Moyà-Solà, 2013; Minwer-Barakat et al, 2017), with some exceptions focused on the diet (Ramdarshan, Merceron & Marivaux, 2012), the locomotor behaviour (Marigó et al, 2016) and the endocranial anatomy (Ramdarshan & Orliac, 2016) of several species. However, only a few contributions have been published regarding European primates from the early Eocene, recently including the revision of Agerinia roselli from Les Saleres and the description of the new species Agerinia smithorum from Casa Retjo-1 (Femenias-Gual et al, 2016a and Femenias-Gual et al, 2016b, respectively).…”