New records of early Paleocene (earliest Torrejonian) plesiadapiforms from northeastern Montana, USA, provide a window into the diversification of stem primates.

Plesiadapiforms (putative stem primates) appear in the fossil record shortly after the Cretaceous/Paleogene boundary and subsequently radiated throughout the Paleocene into a taxonomically and ecomorphologically diverse group. The oldest known plesiadapiforms come from early Puercan (the oldest North American Land Mammal 'age' [NALMA] of the Cenozoic) deposits in northeastern Montana, and all records of Puercan plesiadapiforms are taxonomically restricted to members of the Purgatoriidae and the enigmatic genus Pandemonium. Plesiadapiform diversity substantially increased in the following Torrejonian NALMA, but the sparse record of faunas between the Puercan and the well-known middle and late Torrejonian has hampered our understanding of this important interval in early primate evolution. Here we report new plesiadapiform dental fossils from early Torrejonian (To1) deposits from the Tullock Member of the Fort Union Formation in northeastern Montana that record several poorly known taxa including members of the Purgatoriidae, Paromomyidae and Pandemonium, and that document the largest and most diverse assemblage of To1 plesiadapiforms known. We describe a new species of the purgatoriid Ursolestes (Ursolestes blissorum, sp. nov.) that represents the largest plesiadapiform known from the early Paleocene and, among other taxa, provides additional evidence that the temporal range of purgatoriids extended into the Torrejonian. Large sample sizes of the oldest known paromomyid, Paromomys farrandi, allowed us to document intraspecific variability and one undescribed tooth locus. Our observations illuminate changes in dental morphology of some taxa that occurred in To1 and may inform the acquisition of certain diagnostic plesiadapiform dental characters. We evaluate plesiadapiform species richness, mean body mass and body-mass disparity through the Paleocene and reveal unrecognized levels of richness in To1 and a general trend of stable body mass and body-mass disparity. Our findings contribute to documented patterns of plesiadapiform provincialism in the early Paleocene and shed light on the early stages of their Torrejonian radiation.

A robust alternative to assessing three-dimensional relative enamel thickness for the use in taxonomic assessment.

OBJECTIVE: Three-dimensional relative enamel thickness (3DRET) is important for assessing hypotheses about taxonomy, phylogeny, and dietary reconstruction for primates. However, its weaknesses have not been thoroughly investigated. Here, we analyze its weaknesses and propose an index aiming at better taxonomic discrimination. MATERIALS AND METHODS: The dimensionless 3D index, ratio of enamel-thickness to dentine-thickness (3DRED), which is defined as the cubic root of the ratio of 3D average enamel thickness (3DAET) to 3D average dentine thickness (3DADT), is proposed here. To compare 3DRET and 3DRED and their sensitivity to voxel size, a fossil orangutan molar was scanned 14 times with different resolutions ranging from 10 to 50 µm. Enamel thickness analysis was carried out for each resultant digital model. In addition, enamel thickness measurements of 179 mandibular permanent molars (eight genera) were analyzed, followed by investigating the relationship between 3DRET and 3DAET and between 3DRED and 3DAET. RESULTS: Regarding sensitivity, 3DRED is more robust than 3DRET. In addition, 3DRET is correlated with 3DAET by linear curve with regression coefficients approximating or larger than 0.8 in most cases, while 3DRED shows less correlation with 3DAET. Furthermore, there are clear separations between different taxa in the bivariate plot of 3DRED against 3DAET, indicative of the taxonomic value of 3DRED. CONCLUSION: Under certain conditions, 3DRED promises to be a robust and reliable alternative to 3DRET in taxonomic study.

New fossils, systematics, and biogeography of the oldest known crown primate Teilhardina from the earliest Eocene of Asia, Europe, and North America.

Omomyiform primates are among the most basal fossil haplorhines, with the oldest classified in the genus Teilhardina and known contemporaneously from Asia, Europe, and North America during the Paleocene-Eocene Thermal Maximum (PETM) ∼56 mya. Characterization of morphology in this genus has been limited by small sample sizes and fragmentary fossils. A new dental sample (n = 163) of the North American species Teilhardina brandti from PETM strata of the Bighorn Basin, Wyoming, documents previously unknown morphology and variation, prompting the need for a systematic revision of the genus. The P4 of T. brandti expresses a range of variation that encompasses that of the recently named, slightly younger North American species 'Teilhardina gingerichi,' which is here synonymized with T. brandti. A new partial dentary preserving the alveoli for P1-2 demonstrates that T. brandti variably expresses an unreduced, centrally-located P1, and in this regard is similar to that of T. asiatica from China. This observation, coupled with further documentation of variability in P1 alveolar size, position, and presence in the European type species T. belgica, indicates that the original diagnosis of T. asiatica is insufficient at distinguishing this species from either T. belgica or T. brandti. Likewise, the basal omomyiform 'Archicebus achilles' requires revision to be distinguished from Teilhardina. Results from a phylogenetic analysis of 1890 characters scored for omomyiforms, adapiforms, and other euarchontan mammals produces a novel clade including T. magnoliana, T. brandti, T. asiatica, and T. belgica to the exclusion of two species previously referred to Teilhardina, which are here classified in a new genus (Bownomomys americanus and Bownomomys crassidens). While hypotheses of relationships and inferred biogeographic patterns among species of Teilhardina could change with the discovery of more complete fossils, the results of these analyses indicate a similar probability that the genus originated in either Asia or North America.

Skeletal morphology of the early Paleocene plesiadapiform Torrejonia wilsoni (Euarchonta, Palaechthonidae).

Plesiadapiforms, like other Paleogene mammals, are known mostly from fossil teeth and jaw fragments. The several families of plesiadapiforms known from partial skeletons have all been reconstructed as arborealists, but differences in postcranial morphology among these taxa indicate a diversity of positional behaviors. Here we provide the first detailed descriptions and comparisons of a dentally associated partial skeleton (NMMNH P-54500) and of the most complete dentary with anterior teeth (NMMNH P-71598) pertaining to Torrejonia wilsoni, from the early Paleocene (late Torrejonian To3 interval zone) of the Nacimiento Formation, San Juan Basin, New Mexico, USA. NMMNH P-54500 is the oldest known partial skeleton of a plesiadapiform and the only known postcrania for the Palaechthonidae. This skeleton includes craniodental fragments with all permanent teeth fully erupted, and partial forelimbs and hind limbs with some epiphyses unfused, indicating that this individual was a nearly fully-grown subadult. Analysis of the forelimb suggests mobile shoulder and elbow joints, a habitually flexed forearm, and capacity for manual grasping. The hip joint allowed abduction and lateral rotation of the thigh and provides evidence for frequent orthograde postures on large diameter supports. Other aspects of the hind limb suggest a habitually flexed thigh and knee with no evidence for specialized leaping, and mobile ankle joints capable of high degrees of inversion and eversion. Although it is likely that some variability exists within the group, analysis of this skeleton suggests that palaechthonids are most like paromomyids among plesiadapiforms, but retain more plesiomorphic postcranial features than has been documented for the Paromomyidae. These observations are congruent with craniodental evidence supporting palaechthonids and paromomyids as closely related within the Paromomyoidea. The skeleton of T. wilsoni also demonstrates that many regions of the postcranium were already well adapted for arboreality within the first few million years of the diversification of placental mammals following the Cretaceous-Paleogene extinction event.

The role of dietary competition in the origination and early diversification of North American euprimates.

The conditions under which early euprimates (adapids and omomyids) originated and evolved is an area of longstanding debate. The leading hypotheses of euprimate origins promulgate diet as a core component of the early evolution of this group, despite the role of dietary competition in euprimate originations never being tested directly. This study compared three competition models (non-competition, competitive displacement, competitive coexistence) with observed patterns of dietary niche overlap, reconstructed from three-dimensional molar morphology, at the time of the euprimate radiation in North America (at the Paleocene-Eocene boundary). Overlap of reconstructed multidimensional dietary niches between euprimates and members of their guild were analysed using a modified MANOVA to establish the nature of the competitive environment surrounding euprimate origins in North America (an immigration event). Results indicated that adapids entered the mammalian guild in the absence of competition, suggesting dietary adaptations that were unique within the community. Conversely, omomyids experienced strong, but transitory, competition with nyctitheriids, suggesting that omomyids possessed the ability to out-compete this group. These results show that adapids and omomyids experienced different competitive scenarios upon their arrival (origination) in North America and confirm the significance of diet (and dietary adaptations) in euprimate origination and early diversification in mammalian communities.

New fossils from Tadkeshwar Mine (Gujarat, India) increase primate diversity from the early Eocene Cambay Shale.

Several new fossil specimens from the Cambay Shale Formation at Tadkeshwar Lignite Mine in Gujarat document the presence of two previously unknown early Eocene primate species from India. A new species of Asiadapis is named based on a jaw fragment preserving premolars similar in morphology to those of A. cambayensis but substantially larger. Also described is an exceptionally preserved edentulous dentary (designated cf. Asiadapis, unnamed sp. nov.) that is slightly larger and much more robust than previously known Cambay Shale primates. Its anatomy most closely resembles that of Eocene adapoids, and the dental formula is the same as in A. cambayensis. A femur and calcaneus are tentatively allocated to the same taxon. Although the dentition is unknown, exquisite preservation of the dentary of cf. Asiadapis sp. nov. enables an assessment of masticatory musculature, function, and gape adaptations, as well as comparison with an equally well-preserved dentary of the asiadapid Marcgodinotius indicus, also from Tadkeshwar. The new M. indicus specimen shows significant gape adaptations but was probably capable of only weak bite force, whereas cf. Asiadapis sp. nov. probably used relatively smaller gapes but could generate relatively greater bite forces.

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.

Breaking the rules: Phylogeny, not life history, explains dental eruption sequence in primates.

OBJECTIVES: Although a great deal is known about the biology of tooth development and eruption, there remains disagreement about the factors driving the evolution of dental eruption sequence. We assessed postcanine eruption sequence across a large sample of primates to test two hypotheses: (1) Dental eruption sequence is significantly correlated with life history and body size variables that capture postnatal growth and longevity (Schultz's Rule), and (2) Dental eruption sequence is conserved phylogenetically. MATERIALS AND METHODS: We assessed postcanine dental eruption sequence for 194 individuals representing 21 primate genera spanning eight families. With the inclusion of an additional 29 primate genera from the literature, this is the most comprehensive report on dental eruption sequence in primates to date. We used a series of phylogenetic analyses to statistically compare dental eruption sequence to life history and body size and test for phylogenetic signal in these traits. RESULTS: Dental eruption sequence is conserved phylogenetically in primates, and body and brain size are both significantly associated with dental eruption sequence. Ancestral state reconstruction supports the hypothesis that the third molar erupted before one or more of the premolars in the ancestor of primates and derived clades within primates evolved an eruption sequence in which the third molar erupts after the premolars. DISCUSSION: Schultz's Rule, as it is currently written and applied, is not supported by this extended data set. Our results demonstrate that dental eruption sequence is a far better predictor of phylogeny and will likely prove useful in phylogenetic hypotheses about relationships between extinct and extant mammalian taxa. The evolution of dental eruption sequence is likely driven by factors that significantly influence body size and mandibular symphyseal fusion.

Postcrania of the most primitive euprimate and implications for primate origins.

The fossil record of early primates is largely comprised of dentitions. While teeth can indicate phylogenetic relationships and dietary preferences, they say little about hypotheses pertaining to the positional behavior or substrate preference of the ancestral crown primate. Here we report the discovery of a talus bone of the dentally primitive fossil euprimate Donrussellia provincialis. Our comparisons and analyses indicate that this talus is more primitive than that of other euprimates. It lacks features exclusive to strepsirrhines, like a large medial tibial facet and a sloping fibular facet. It also lacks the medially positioned flexor-fibularis groove of extant haplorhines. In these respects, the talus of D. provincialis comes surprisingly close to that of the pen-tailed treeshrew, Ptilocercus lowii, and extinct plesiadapiforms for which tali are known. However, it differs from P. lowii and is more like other early euprimates in exhibiting an expanded posterior trochlear shelf and deep talar body. In overall form, the bone approximates more leaping reliant euprimates. The phylogenetically basal signal from the new fossil is confirmed with cladistic analyses of two different character matrices, which place D. provincialis as the most basal strepsirrhine when the new tarsal data are included. Interpreting our results in the context of other recent discoveries, we conclude that the lineage leading to the ancestral euprimate had already become somewhat leaping specialized, while certain specializations for the small branch niche came after crown primates began to radiate.

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.

The evolutionary radiation of plesiadapiforms.

Very shortly after the disappearance of the non-avian dinosaurs, the first mammals that had features similar to those of primates started appearing. These first primitive forms went on to spawn a rich diversity of plesiadapiforms, often referred to as archaic primates. Like many living primates, plesiadapiforms were small arboreal animals that generally ate fruit, insects, and, occasionally, leaves. However, this group lacked several diagnostic features of euprimates. They also had extraordinarily diverse specializations, represented in eleven families and more than 140 species, which, in some cases, were like nothing seen since in the primate order. Plesiadapiforms are known from all three Northern continents, with representatives that persisted until at least 37 million years ago. In this article we provide a summary of the incredible diversity of plesiadapiform morphology and adaptations, reviewing our knowledge of all eleven families. We also discuss the challenges that remain in our understanding of their ecology and evolution.

First virtual endocasts of adapiform primates.

Well-preserved crania of notharctine adapiforms from the Eocene of North America provide the best direct evidence available for inferring neuroanatomy and encephalization in early euprimates (crown primates). Virtual endocasts of the notharctines Notharctus tenebrosus (n = 3) and Smilodectes gracilis (n = 4) from the middle Eocene Bridger formation of Wyoming, and the late Eocene European adapid adapiform Adapis parisiensis (n = 1), were reconstructed from high-resolution X-ray computed tomography (CT) data. While the three species share many neuroanatomical similarities differentiating them from plesiadapiforms (stem primates) and extant euprimates, our sample of N. tenebrosus displays more variation than that of S. gracilis, possibly related to differences in the patterns of cranial sexual dimorphism or within-lineage evolution. Body masses predicted from associated teeth suggest that N. tenebrosus was larger and had a lower encephalization quotient (EQ) than S. gracilis, despite their close relationship and similar inferred ecologies. Meanwhile, body masses predicted from cranial length of the same specimens suggest that the two species were more similar, with overlapping body mass and EQ, although S. gracilis exhibits a range of EQs shifted upwards relative to that of N. tenebrosus. While associated data from other parts of the skeleton are mostly lacking for specimens included in this study, measurements for unassociated postcrania attributed to these species yield body mass and EQ estimates that are also more similar to each other than those based on teeth. Regardless of the body mass prediction method used, results suggest that the average EQ of adapiforms was similar to that of plesiadapiforms, only overlapped the lower quadrant for the range of extant strepsirrhines, and did not overlap with the range of extant haplorhines. However, structural changes evident in these endocasts suggest that early euprimates relied more on vision than olfaction relative to plesiadapiforms, despite having relatively small endocranial volumes compared to extant taxa.

Molar shape variability in platyrrhine primates.

Recent phylogenetic analyses suggest that platyrrhines constitute a monophyletic group represented by three families: Cebidae, Atelidae, and Pitheciidae. Morphological variability between and within these three families, however, is widely discussed and debated. The aim of this study was to assess molar shape variability in platyrrhines, to explore patterns of interspecific variation among extant species, and to evaluate how molar shape can be used as a taxonomic indicator. The analyses were conducted using standard multivariate analyses of geometric morphometric data from 802 platyrrhine lower molars. The results indicated that the interspecific variation exhibited a highly homoplastic pattern related to functional adaptation of some taxa. However, phylogeny was also an important factor in shaping molar morphological traits, given that some phenotypic similarities were consistent with current phylogenetic positions. Our results show that the phylogenetic and functional signals of lower molar shape vary depending on the taxa and the tooth considered. Based on molar shape, Aotus showed closer similarities to Callicebus, as well as to some Cebidae and Ateles-Lagothrix, due to convergent evolutionary trends caused by similar dietary habits, or due to fast-evolving branches in the Aotus lineage, somewhat similar to the shape of Callicebus and Cebidae.

Phylogeny, paleontology, and primates: do incomplete fossils bias the tree of life?

Paleontological systematics relies heavily on morphological data that have undergone decay and fossilization. Here, we apply a heuristic means to assess how a fossil's incompleteness detracts from inferring its phylogenetic relationships. We compiled a phylogenetic matrix for primates and simulated the extinction of living species by deleting an extant taxon's molecular data and keeping only those morphological characters present in actual fossils. The choice of characters present in a given living taxon (the subject) was defined by those present in a given fossil (the template). By measuring congruence between a well-corroborated phylogeny to those incorporating artificial fossils, and by comparing real vs. random character distributions and states, we tested the information content of paleontological datasets and determined if extinction of a living species leads to bias in phylogeny reconstruction. We found a positive correlation between fossil completeness and topological congruence. Real fossil templates sampled for 36 or more of the 360 available morphological characters (including dental) performed significantly better than similarly complete templates with random states. Templates dominated by only one partition performed worse than templates with randomly sampled characters across partitions. The template based on the Eocene primate Darwinius masillae performs better than most other templates with a similar number of sampled characters, likely due to preservation of data across multiple partitions. Our results support the interpretation that Darwinius is strepsirhine, not haplorhine, and suggest that paleontological datasets are reliable in primate phylogeny reconstruction.

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.

Convergent evolution of anthropoid-like adaptations in Eocene adapiform primates.

Adapiform or 'adapoid' primates first appear in the fossil record in the earliest Eocene epoch ( approximately 55 million years (Myr) ago), and were common components of Palaeogene primate communities in Europe, Asia and North America. Adapiforms are commonly referred to as the 'lemur-like' primates of the Eocene epoch, and recent phylogenetic analyses have placed adapiforms as stem members of Strepsirrhini, a primate suborder whose crown clade includes lemurs, lorises and galagos. An alternative view is that adapiforms are stem anthropoids. This debate has recently been rekindled by the description of a largely complete skeleton of the adapiform Darwinius, from the middle Eocene of Europe, which has been widely publicised as an important 'link' in the early evolution of Anthropoidea. Here we describe the complete dentition and jaw of a large-bodied adapiform (Afradapis gen. nov.) from the earliest late Eocene of Egypt ( approximately 37 Myr ago) that exhibits a striking series of derived dental and gnathic features that also occur in younger anthropoid primates-notably the earliest catarrhine ancestors of Old World monkeys and apes. Phylogenetic analysis of 360 morphological features scored across 117 living and extinct primates (including all candidate stem anthropoids) does not place adapiforms as haplorhines (that is, members of a Tarsius-Anthropoidea clade) or as stem anthropoids, but rather as sister taxa of crown Strepsirrhini; Afradapis and Darwinius are placed in a geographically widespread clade of caenopithecine adapiforms that left no known descendants. The specialized morphological features that these adapiforms share with anthropoids are therefore most parsimoniously interpreted as evolutionary convergences. As the largest non-anthropoid primate ever documented in Afro-Arabia, Afradapis nevertheless provides surprising new evidence for prosimian diversity in the Eocene of Africa, and raises the possibility that ecological competition between adapiforms and higher primates might have played an important role during the early evolution of stem and crown Anthropoidea in Afro-Arabia.

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.

Late Middle Eocene primate from Myanmar and the initial anthropoid colonization of Africa.

Reconstructing the origin and early evolutionary history of anthropoid primates (monkeys, apes, and humans) is a current focus of paleoprimatology. Although earlier hypotheses frequently supported an African origin for anthropoids, recent discoveries of older and phylogenetically more basal fossils in China and Myanmar indicate that the group originated in Asia. Given the Oligocene-Recent history of African anthropoids, the colonization of Africa by early anthropoids hailing from Asia was a decisive event in primate evolution. However, the fossil record has so far failed to constrain the nature and timing of this pivotal event. Here we describe a fossil primate from the late middle Eocene Pondaung Formation of Myanmar, Afrasia djijidae gen. et sp. nov., that is remarkably similar to, yet dentally more primitive than, the roughly contemporaneous North African anthropoid Afrotarsius. Phylogenetic analysis suggests that Afrasia and Afrotarsius are sister taxa within a basal anthropoid clade designated as the infraorder Eosimiiformes. Current knowledge of eosimiiform relationships and their distribution through space and time suggests that members of this clade dispersed from Asia to Africa sometime during the middle Eocene, shortly before their first appearance in the African fossil record. Crown anthropoids and their nearest fossil relatives do not appear to be specially related to Afrotarsius, suggesting one or more additional episodes of dispersal from Asia to Africa. Hystricognathous rodents, anthracotheres, and possibly other Asian mammal groups seem to have colonized Africa at roughly the same time or shortly after anthropoids gained their first toehold there.

Species in the primate fossil record.

Species in the fossil record are population pools of genetic and phenetic variation at a place and time, morphologically recognizable and distinguishable from others by empirical standards. Change through time can be substantial, requiring subdivision of lineages that becomes more arbitrary as they become more complete. Evolution is about form, space, and time; it is about variation and change. Interpretation of species in the fossil record touches all of these.

A pragmatic approach to the species problem from a paleontological perspective.

The ideal scenario for paleontologists would be for the species they designate to be equivalent to the species recognized for modern animals, in the sense that they were formed as a result of the same evolutionary processes. This would mean, for example, that we could be confident that in combining extant and extinct taxa in phylogenetic analyses we would be dealing with equivalent operational taxonomic units. Notwithstanding the many thousands of pages that have been spent arguing over species concepts, the only concept that has won widespread acceptance for the designation of modern species is Mayr's Biological Species Concept (BSC).(1) In fact, whenever we complete a cladistic analysis, we assume reproductive isolation of our terminal taxa because otherwise their similarities could be the product of interbreeding rather than common ancestry. Fundamentally, we all behave as though the BSC is true.