First record of the genus Microchoerus (Omomyidae, Primates) in the western Iberian Peninsula and its palaeobiogeographic implications

The primate remains from Roc de Santa (Late Eocene, NE Spain) revisited: New taxonomic allocation

The scarce primate remains from the late Eocene locality of Roc de Santa (Central Pyrenees, NE Spain) were first documented in 1975. This material included a mandibular fragment with P₃-M₂ and a maxillary fragment with P³-M³ assigned to Adapis magnus (later transferred to the genus Leptadapis), and an isolated M₃ attributed to Necrolemur antiquus. However, these specimens were never described in detail. We have thoroughly studied these specimens, with the exception of the mandibular fragment, which has been lost. The maxillary fragment is much smaller than in Leptadapis magnus and shows clear morphological differences from that species; this specimen is assigned to Microchoerus hookeri. Similarly, the isolated M₃ resembles that of M. hookeri in size and morphology, and can therefore be attributed to this taxon. In addition, we describe an upper incisor never reported previously, which can also be allocated to M. hookeri, representing the first description of this tooth for the species. Therefore, we conclude that the previous taxonomic determinations were mistaken and all the available primate specimens from Roc de Santa can be confidently assigned to the species M. hookeri, previously described from the same-age localities of Sossís, Spain, and Eclépens-B, Switzerland.

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

Primates reached a great abundance and diversity during the Eocene, favored by warm temperatures and by the development of dense forests throughout the Northern Hemisphere. Here we describe new primate material from La Verrerie de Roches, a Middle Eocene karstic infill situated in the Jura Region (Switzerland), consisting of more than 80 dental remains. The primate assemblage from La Verrerie de Roches includes five different taxa. The best represented primate is Necrolemur aff. anadoni, similar in size and overall morphology to Necrolemur anadoni but resembling in some features the younger species Necrolemur antiquus. Microchoerines are also represented by two species of Pseudoloris, P. pyrenaicus and Pseudoloris parvulus, constituting the unique joint record of these two species known up to now. Remains of Adapiformes are limited to one isolated tooth of a large anchomomyin and another tooth belonging to the small adapine Microadapis cf. sciureus. The studied primate association allows assigning La Verrerie de Roches to the Robiacian Land Mammal Age. More specifically, this site can be confidently situated between the MP15 and MP16 reference levels, although the primate assemblage probably indicates some degree of temporal mixing. This is the first record of P. pyrenaicus and a form closely related to N. anadoni out of the Iberian Peninsula. The identification of these microchoerines in Switzerland gives further support to the connection of NE Spain and Central Europe during the Middle Eocene.

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

BACKGROUND

The Eocene was the warmest epoch of the Cenozoic and recorded the appearance of several orders of modern mammals, including the first occurrence of Euprimates. During the Eocene, Euprimates were mainly represented by two groups, adapiforms and omomyiforms, which reached great abundance and diversity in the Northern Hemisphere. Despite this relative abundance, the record of early Eocene primates from the European continent is still scarce and poorly known, preventing the observation of clear morphological trends in the evolution of the group and the establishment of phylogenetic relationships among different lineages. However, knowledge about the early Eocene primates from the Iberian Peninsula has been recently increased through the description of new material of the genus Agerinia from several fossil sites from Northeastern Spain.

METHODS

Here we present the first detailed study of the euprimate material from the locality of Masia de l'Hereuet (early Eocene, NE Spain). The described remains consist of one fragment of mandible and 15 isolated teeth. This work provides detailed descriptions, accurate measurements, high-resolution figures and thorough comparisons with other species of Agerinia as well with other Eurasian notharctids. Furthermore, the position of the different species of Agerinia has been tested with two phylogenetic analyses.

RESULTS

The new material from Masia de l'Hereuet shows several traits that were previously unknown for the genus Agerinia, such as the morphology of the upper and lower fourth deciduous premolars and the P2, and the unfused mandible. Moreover, this material clearly differs from the other described species of Agerinia, A. roselli and A. smithorum, thus allowing the erection of the new species Agerinia marandati. The phylogenetic analyses place the three species of Agerinia in a single clade, in which A. smithorum is the most primitive species of this genus.

DISCUSSION

The morphology of the upper molars reinforces the distinction of Agerinia from other notharctids like Periconodon. The analysis of the three described species of the genus, A. smithorum, A. marandati and A. roselli, reveals a progressive change in several morphological traits such as the number of roots and the position of the P1 and P2, the molarization of the P4, the reduction of the paraconid on the lower molars and the displacement of the mental foramina. These gradual modifications allow for the interpretation that these three species, described from the early Eocene of the Iberian Peninsula, are part of a single evolutionary lineage. The stratigraphical position of Masia de l'Hereuet and Casa Retjo-1 (type locality of A. smithorum) and the phylogenetic analyses developed in this work support this hypothesis.

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

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 M₁ and M₂, single paracone in the upper molars and premolars and, particularly, by the lack of mesostyle in most M¹ and M², 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.

Agerinia smithorum sp. nov., a new early Eocene primate from the Iberian Peninsula

The new species Agerinia smithorum (Adapiformes, Primates) from the early Eocene of the Iberian Peninsula is erected in this work. An emended diagnosis of the genus is provided, together with a broad description of the new species and comparisons with other samples assigned to Agerinia and other similar medium-sized cercamoniines. The new species is based on the most complete specimen of this genus published to date, a mandible preserving the alveoli of the canine and P1 , the roots of the P2 and all teeth from P3 to M3 . It was found in Casa Retjo-1, a new early Eocene locality from Northeastern Spain. The studied specimen is clearly distinguishable from other cercamoniines such as Periconodon, Darwinius, and Donrussellia, but very similar to Agerinia roselli, especially in the similar height of P3 and P4 and the general morphology of the molars, therefore allowing the allocation to the same genus. However, it is undoubtedly distinct from A. roselli, having a less molarized P4 and showing a larger paraconid in the M1 and a tiny one in the M2 , among other differences. The body mass of A. smithorum has also been estimated, ranging from 652 to 724 g, similar to that of A. roselli. The primitive traits shown by A. smithorum (moderately molarized P4 , large paraconid in the M1 and small but distinct in the M2 ) suggest that it could be the ancestor of A. roselli.

On the determination of the Microchoerus (Omomyidae, Primates) remains from Sant Cugat de Gavadons (Late Eocene, Ebro Basin, NE Spain)

OBJECTIVES

The presence of Microchoerus in Sant Cugat de Gavadons (Late Eocene, Ebro Basin, Northeastern Spain) was first noted by M. Crusafont, who described a fragment of maxilla with two teeth that he interpreted as P(4) and M(1) and referred this specimen to the species Microchoerus ornatus. The objective of this work is to study in detail this fossil and check if the previous taxonomic determination was correct.

METHODS

We reexamine the single specimen from Sant Cugat de Gavadons, providing for the first time detailed descriptions, measurements and illustrations. We also compare this fossil with the holotype of Microchoerus ornatus from Mormont Entreroches (Switzerland) and with the type material of all other described species of Microchoerus.

RESULTS

Although the scarcity of material from Sant Cugat de Gavadons and the strong wear of the two available teeth (which in fact correspond to P(3) and P(4)) do not allow a determination at the specific level, it is clear that this form presents notable differences with the type of M. ornatus and must not be referred to this species.

DISCUSSION

Neither the anatomical identification of the two teeth of this maxillary fragment, nor the specific determination of the specimen from Sant Cugat de Gavadons was correct. The ascription of this fossil to Microchoerus ornatus, which represented the only mention of the species in the Iberian Peninsula, is no longer valid. Therefore, the known geographical range of M. ornatus remains restricted to Switzerland.

Necrolemur anadoni, a new species of Microchoerinae (Omomyidae, Primates) from the Middle Eocene of Sant Jaume de Frontanyà (Pyrenees, Northeastern Spain)

OBJECTIVES

The material of Necrolemur (Microchoerinae, Omomyidae, Primates) from the Middle Eocene (Robiacian) locality of Sant Jaume de Frontanyà (Eastern Pyrenees) is described. This is the first confirmable record of this genus from Spain.

METHODS

A mandible fragment bearing P4 -M3 and 15 isolated teeth have been carefully described and compared with all the known species of Necrolemur (namely Necrolemur antiquus, Necrolemur zitteli and Necrolemur cf. zitteli from Egerkingen α) and with Nannopithex filholi.

RESULTS

The studied material shows substantial differences from all previously described forms of Necrolemur and can be erected as a new species. Necrolemur anadoni sp. nov. is characterized by its small size, weak enamel wrinkling, lower molars with the trigonid significantly narrower than the talonid, distinct paraconid in the M1 but poorly differentiated M2 and M3 paraconids, relatively short M3 hypoconulid lobe, M(1-2) with tubercular buccal metaconule, crest-shaped lingual metaconule, hypocone connected to the protocone by a weak postprotocingulum, and M(3) with a very reduced talon basin. It exhibits intermediate size and morphological features between the older Nannopithex filholi and the more recent Necrolemur antiquus.

CONCLUSIONS

This finding allows reinterpretation of the phylogenetic relationships of the known species of Necrolemur. Necrolemur anadoni is considered a direct descendant of Nannopithex filholi and the ancestor of Necrolemur antiquus, whereas Necrolemur zitteli would be a descendant of N. antiquus. Finally, Necrolemur cf. zitteli from Egerkingen most likely evolved independently from N. filholi, being thus separated from the N. filholi-N. anadoni-N. antiquus lineage.

New material of Pseudoloris parvulus (Microchoerinae, Omomyidae, Primates) from the Late Eocene of Sossís (northeastern Spain) and its implications for the evolution of Pseudoloris

The species Pseudoloris parvulus, identified in several Middle and Late Eocene European sites, was previously known in the Iberian Peninsula by a single mandible preserving P4-M3 from Sossís (Southern Pyrenean Basins, northeastern Spain), described in the 1960s. Further field work at this Late Eocene site has led to the recovery of a large number of mammal remains, including the additional material of P. parvulus described in this paper. Some specimens of P. parvulus from this locality have also been recently found in the collections of the Naturhistorisches Museum Basel, Switzerland. The whole sample consists of 11 mandible fragments including several teeth, three upper dental series and nearly 80 isolated teeth including all of the dental elements, and represents the most complete sample of the genus described from the Iberian Peninsula. This abundant material allows us to provide an emended diagnosis for the species and to observe several directional changes in the dental morphology of the lineage including the species Pseudoloris saalae, Pseudoloris isabenae, Pseudoloris pyrenaicus and P. parvulus. These directional changes include the progressive reduction of the paraconid in the lower molars and the increase in size of the hypocone, metaconule and paraconule in the upper molars. Moreover, despite the overall resemblance among all of the samples ascribed to P. parvulus, we also recognize some differences, particularly an increase in size and better development of the hypocone from the oldest populations of the species, such as Le Bretou, to the most recent ones, like Sossís and Perrière. Therefore, this study sheds new light on the evolution of this genus, which inhabited Europe from the Middle Eocene to the Early Oligocene.