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E. Christopher Kirk - One of the best experts on this subject based on the ideXlab platform.
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Internal nasal morphology of the Eocene primate Rooneyia viejaensis and extant Euarchonta: Using μCT scan data to understand and infer patterns of nasal fossa evolution in primates
Journal of human evolution, 2019Co-Authors: Ingrid K. Lundeen, E. Christopher KirkAbstract:Abstract Primates have historically been viewed as having a diminished sense of smell compared to other mammals. In haplorhines, olfactory reduction has been inferred partly based on the complexity of the bony turbinals within the nasal cavity. Some turbinals are covered in olfactory epithelium, which contains olfactory receptor neurons that detect odorants. Accordingly, turbinal number and complexity has been used as a rough anatomical proxy for the relative importance of olfactory cues for an animal's behavioral ecology. Unfortunately, turbinals are delicate and rarely preserved in fossil specimens, limiting opportunities to make direct observations of the olfactory periphery in extinct primates. Here we describe the turbinal morphology of Rooneyia viejaensis, a late middle Eocene primate of uncertain phylogenetic affinities from the Tornillo Basin of West Texas. This species is currently the oldest fossil primate for which turbinals are preserved with minimal damage or distortion. Microcomputed tomography (μCT) reveals that Rooneyia possessed 1 nasoturbinal, 4 bullar ethmoturbinals, 1 frontoturbinal, 1 interturbinal, and an olfactory recess. This pattern is broadly similar to the condition seen in some extant strepsirrhine primates but differs substantially from the condition seen in extant haplorhines. Crown haplorhines possess only two ethmoturbinals and lack frontoturbinals, interturbinals, and an olfactory recess. Additionally, crown anthropoids have ethmoturbinals that are non-bullar. These observations reinforce the conclusion that Rooneyia is not a stem Tarsiiform or stem anthropoid. However, estimated olfactory turbinal surface area in Rooneyia is greater than that of similar-sized haplorhines but smaller than that of similar-sized lemuriforms and lorisiforms. This finding suggests that although Rooneyia was broadly plesiomorphic in retaining a large complement of olfactory turbinals as in living strepsirrhines, Rooneyia may have evolved somewhat diminished olfactory abilities as in living haplorhines.
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Cranial anatomy of the Duchesnean primate Rooneyia viejaensis: new insights from high resolution computed tomography.
Journal of human evolution, 2014Co-Authors: E. Christopher Kirk, Parham Daghighi, Thomas E. Macrini, Bhart-anjan S. Bhullar, Timothy B RoweAbstract:Rooneyia viejaensis is a North American Eocene primate of uncertain phylogenetic affinities. Although the external cranial anatomy of Rooneyia is well studied, various authors have suggested that Rooneyia is a stem haplorhine, stem strepsirrhine, stem Tarsiiform, or stem anthropoid. Here we describe the internal cranial anatomy of the Rooneyia holotype based on micro-computed tomography and discuss the phylogenetic implications of this anatomy. Precise measurements of the natural endocast filling the braincase of the Rooneyia holotype reveal that the genus had a relative brain size comparable to some living callitrichines and strepsirrhines. Rooneyia was thus probably more encephalized than any other known omomyiform, adapiform, or plesiadapiform. Relative olfactory bulb size in Rooneyia was most comparable to some living strepsirrhines and the stem anthropoid Parapithecus. The nasal fossa of Rooneyia resembled that of living strepsirrhines in retaining an obliquely oriented nasolacrimal canal, four ethmoturbinals, and an olfactory recess separated from the nasopharyngeal meatus by a transverse lamina. The ear region of Rooneyia is characterized by large and complete canals for both the stapedial and promontory branches of the internal carotid artery. Rooneyia also retains a patent parotic fissure and thus had an extrabullar origin of the stapedius muscle. In most of these respects, Rooneyia exhibits the condition that is presumed to be primitive for crown primates and lacks a number of key crown haplorhine synapomorphies (e.g., a dorso-ventrally oriented nasolacrimal canal, loss of the olfactory recess, loss of ethmoturbinals 3-4, loss or extreme reduction of the stapedial canal due to involution of the stapedial artery). These data are consistent with the hypothesis that Rooneyia is an advanced stem primate or a basal crown primate but are inconsistent with prior suggestions that Rooneyia is a crown haplorhine.
Maeva Orliac - One of the best experts on this subject based on the ideXlab platform.
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Endocranial morphology of M icrochoerus erinaceus (Euprimates, Tarsiiformes) and early evolution of the Euprimates brain
American Journal of Physical Anthropology, 2016Co-Authors: Anusha Ramdarshan, Maeva OrliacAbstract:Objectives: Innovations in brain structure and increase in brain size relative to body mass are key features of Primates evolutionary history. Surprisingly, the endocranial morphology of early Euprimates is still rather poorly known, and our understanding of early euprimate brain evolution (Eocene epoch) relies on a handful of specimens. Materials and Methods: In this article, we describe the endocranial cast of the Tarsiiform Microchoerus erina-ceus from the late Early Eocene of Perrière (Quercy fissure filling, France) based on a virtual reconstruction extracted from CT scan data of the endocranial cavity of the complete, undeformed specimen UM-PRR1771. Results: The endocast of M. erinaceus shows the derived features observed in other Euprimates (e.g. sylvian fissure and temporal lobe), with limited neocortical folding, and a telencephalic flexure comparable to that of extant primates. Discussion: Comparison with the endocasts of other available late Eocene primates shows that they already exhibited a variety of brain morphologies, highlighting the complex history of the external features of the primate brain, as early as the Eocene. M. erinaceus was a fruit and gum eater considered as nocturnal based on its orbit size. However, its brain showed small olfactory bulbs-smaller than in the coeval diurnal taxa Adapis parisiensis-and a neocorticali-zation similar to folivorous taxa. These observations contrast with patterns observed in primates today where nocturnal taxa have larger olfactory bulbs than diurnal taxa, and call into question a direct correlation between frugivory and neocorticalization increase in primates. Am J Phys Anthropol 000:000-000,
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Endocranial morphology of Microchoerus erinaceus (Euprimates, Tarsiiformes) and early evolution of the Euprimates brain
American journal of physical anthropology, 2015Co-Authors: Anusha Ramdarshan, Maeva OrliacAbstract:Objectives Innovations in brain structure and increase in brain size relative to body mass are key features of Primates evolutionary history. Surprisingly, the endocranial morphology of early Euprimates is still rather poorly known, and our understanding of early euprimate brain evolution (Eocene epoch) relies on a handful of specimens. Materials and Methods In this article, we describe the endocranial cast of the Tarsiiform Microchoerus erinaceus from the late Early Eocene of Perriere (Quercy fissure filling, France) based on a virtual reconstruction extracted from CT scan data of the endocranial cavity of the complete, undeformed specimen UM-PRR1771. Results The endocast of M. erinaceus shows the derived features observed in other Euprimates (e.g. sylvian fissure and temporal lobe), with limited neocortical folding, and a telencephalic flexure comparable to that of extant primates. Discussion Comparison with the endocasts of other available late Eocene primates shows that they already exhibited a variety of brain morphologies, highlighting the complex history of the external features of the primate brain, as early as the Eocene. M. erinaceus was a fruit and gum eater considered as nocturnal based on its orbit size. However, its brain showed small olfactory bulbs—smaller than in the coeval diurnal taxa Adapis parisiensis—and a neocorticalization similar to folivorous taxa. These observations contrast with patterns observed in primates today where nocturnal taxa have larger olfactory bulbs than diurnal taxa, and call into question a direct correlation between frugivory and neocorticalization increase in primates. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.
Gregg F. Gunnell - One of the best experts on this subject based on the ideXlab platform.
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Deep time and the search for anthropoid origins.
American Journal of Physical Anthropology, 2005Co-Authors: Ellen R. Miller, Gregg F. Gunnell, Robert D. MartinAbstract:Recent fossil discoveries, phylogenetic analyses, revised reconstructions of continental drift, and accumulating molecular evidence have all yielded new information relating to anthropoid origins within the broader context of primate evolution. There is an emerging consensus among molecular studies that four superorders of eutherian mammals can be recognized: Afrotheria, Euarchontoglires (to which primates belong), Laurasiatheria, and Xenarthra. Overall, molecular phylogenies for mammals agree with some statistical analyses of the primate fossil record in indicating an early origin for primates around 85 Ma ago, and the divergence of haplorhines and strepsirrhines at ca. 77 Ma. Such an ancient date for the origin of haplorhines is some 17 Ma prior to the first known possible primate, and some 22 Ma before the earliest fossil evidence of undoubted euprimates. Because anthropoid fossils date back at least to the late Eocene and perhaps to the middle Eocene, and given indications of an early origin for primates, it is unlikely that ancestral anthropoids arose within any other currently known clade of fossil primates (adapiforms, omomyiforms, strepsirrhines, or Tarsiiforms). Implications of new molecular, morphological, and biogeographic lines of evidence are explored with respect to the likely time and place of the origin of anthropoids. Four competing, testable hypotheses are reviewed in detail: 1) the Paratethyan hypothesis, 2) the continental Asian hypothesis, 3) the Indo-Madagascar hypothesis, and 4) the African hypothesis. A case is made that current evidence best supports a relatively ancient Gondwanan origin for primates, as well as a Gondwanan (African or Indo-Madagascan) origin for anthropoids at least as old as that of any other currently documented major primate clade. Available fossil evidence at present seems to be most compatible with the African hypothesis, but it is noteworthy that primates are included not in Afrotheria but in Euarchontoglires. Yrbk Phys Anthropol 48:60–95, 2005. © 2005 Wiley-Liss, Inc.
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Deep time and the search for anthropoid origins.
American journal of physical anthropology, 2005Co-Authors: Ellen R. Miller, Gregg F. Gunnell, Robert D. MartinAbstract:Recent fossil discoveries, phylogenetic analyses, revised reconstructions of continental drift, and accumulating molecular evidence have all yielded new information relating to anthropoid origins within the broader context of primate evolution. There is an emerging consensus among molecular studies that four superorders of eutherian mammals can be recognized: Afrotheria, Euarchontoglires (to which primates belong), Laurasiatheria, and Xenarthra. Overall, molecular phylogenies for mammals agree with some statistical analyses of the primate fossil record in indicating an early origin for primates around 85 Ma ago, and the divergence of haplorhines and strepsirrhines at ca. 77 Ma. Such an ancient date for the origin of haplorhines is some 17 Ma prior to the first known possible primate, and some 22 Ma before the earliest fossil evidence of undoubted euprimates. Because anthropoid fossils date back at least to the late Eocene and perhaps to the middle Eocene, and given indications of an early origin for primates, it is unlikely that ancestral anthropoids arose within any other currently known clade of fossil primates (adapiforms, omomyiforms, strepsirrhines, or Tarsiiforms). Implications of new molecular, morphological, and biogeographic lines of evidence are explored with respect to the likely time and place of the origin of anthropoids. Four competing, testable hypotheses are reviewed in detail: 1) the Paratethyan hypothesis, 2) the continental Asian hypothesis, 3) the Indo-Madagascar hypothesis, and 4) the African hypothesis. A case is made that current evidence best supports a relatively ancient Gondwanan origin for primates, as well as a Gondwanan (African or Indo-Madagascan) origin for anthropoids at least as old as that of any other currently documented major primate clade. Available fossil evidence at present seems to be most compatible with the African hypothesis, but it is noteworthy that primates are included not in Afrotheria but in Euarchontoglires.
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Omomyid primates (Tarsiiformes) from the Early Middle Eocene at South Pass, Greater Green River Basin, Wyoming.
Journal of human evolution, 2002Co-Authors: Kathleen M. Muldoon, Gregg F. GunnellAbstract:Recent fieldwork in the Gardnerbuttean (earliest Bridgerian) sediments along the northeastern edge of the Green River Basin at South Pass, Wyoming, has yielded a large and diverse sample of omomyid (Tarsiiform) primates. This assemblage includes two species each of Artimonius gen. nov., Washakius, and Omomys, one species of Anaptomorphus, Trogolemur and Uintanius, and a new, primitive species of the rare omomyine genus,Utahia. Utahia is known elsewhere only from its type locality in the Uinta Basin and its phylogenetic position is poorly understood. Utahia carina sp. nov. allows for re-evaluation of the affinities of this genus relative to other omomyines. In most characters, such as a lesser degree of molar trigonid compression, more widely open talonid notches, and a lack of molar talonid crenulation, the new species is more primitive than U. kayi. The dental anatomy of U. carina also indicates that Utahia is morphologically intermediate between washakiins and omomyins, although the balance of anatomical features places Utahia as the sister taxon to a broadly defined "Ourayini" clade. Morphological similarity between U. carina, Loveina zephyri, and primitive Washakius suggests that while the omomyin and washakiin clades may have diverged by the middle Wasatchian, substantial morphological distinctions are first evidenced only in the early Bridgerian. This may be due either to a lack of appropriate faunal samples from older sediments, or, more likely, because ecological circumstances in the early Bridgerian favored omomyine diversification and subsequent replacement of previously occurring taxa. This hypothesis is further supported by the stratigraphic co-occurrence of U. carina, W. izetti, and a primitive variant of W. insignis at South Pass, a marginal area. Basin margins have been hypothesized to provide heterogeneous habitats conducive to the production of evolutionary innovation. Basin margin samples have also been cited as evidence that anaptomorphines were relegated to upland refugia as omomyine taxa began to appear in the later part of the early Eocene. Another possible explanation for the unusual co-occurrence of species at South Pass relates to fluctuating lake levels in the Green River Basin, which intermittently would have made lowland environments inhospitable for arboreal fauna. This would have created a situation whereby species which would normally be allopatric become sympatric at South Pass.
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Wasatchian–Bridgerian (Eocene) paleoecology of the western interior of North America: changing paleoenvironments and taxonomic composition of omomyid (Tarsiiformes) primates
Journal of human evolution, 1997Co-Authors: Gregg F. GunnellAbstract:Many changes in mammalian faunas occurred across the early (Wasatchian) to middle (Bridgerian) Eocene boundary as documented in the fossil record from the Western Interior of North America. One of the more striking changes took place within the Tarsiiform primate family Omomyidae. In the early Eocene, omomyids were dominated, both in abundance and diversity, by the subfamily Anaptomorphinae. In the middle Eocene, the subfamily Omomyinae dominated in abundance, while both subfamilies were nearly equally diverse. Examination of a series of paleoecological indicators including leaf-margin analysis, cenogram analysis, ecological diversity analysis of trophic structure, the distribution and development of ancient soil horizons (paleosols), and the distribution of lacustrine and fluvial facies in the Bighorn and southern Green River basins of Wyoming reveals factors that may have influenced the composition of omomyid primates. Subtle but important changes occurred in paleoclimates with mean annual temperatures reaching Cenozoic maximums at the end of the Wasatchian into the early Bridgerian. Both land mammal ages were typified by subtropical, closed forested conditions, but the Bridgerian was probably more humid and wetter than the Wasatchian. Paleohabitats most commonly sampled in the Wasatchian of the Bighorn Basin are proximal and distal floodplains, while those of the Bridgerian in the southern Green River Basin are lake margins and proximal floodplains. Changes in paleoclimate may have triggered a wave of omomyine immigration near the end of the Wasatchian with omomyines entering into habitats previously occupied by anaptomorphines. Lake margin and proximal floodplain habitats are those most commonly occupied by omomyines in the Bridgerian with anaptomorphines being more common in basin margin and distal floodplain areas not commonly sampled. Omomyine immigration and sampling of differing paleohabitats are two possible explanations for the changes documented in omomyid diversity and abundance.
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Primate Phylogeny: Morphological vs Molecular Results
Molecular phylogenetics and evolution, 1996Co-Authors: Jeheskel Shoshani, Elwyn L. Simons, Colin P. Groves, Gregg F. GunnellAbstract:Our comparative study of morphological (our data on selected living primates) and molecular characters (from the literature) confirms that, overall, phylogenetic reconstructions of Primates, and consequently their classifications, are more similar than dissimilar. When data from fossil Primates are incorporated, there may be several possible relationships among living Primates; the difference between most of them hinges mainly on the position of Tarsius. In one hypothesis, tarsiers are closely related to lemurs and lorises, and thus Primates is divided into Prosimii [lorises, lemurs, and tarsiers] and Anthropoidea [Platyrrhini and Catarrhini, i.e., monkeys, apes, and humans]. Two additional alternatives are that Tarsius is a sister group to the clade embracing lorises + lemurs and Anthropoidea and that in which all three lineages (Tarsius, lorises + lemurs, and Anthropoidea) form a polychotomy. In another hypothesis, tarsiers are closely related to anthropoids, giving these two branches: Strepsirhini [lemurs, lorises] and Haplorhini [tarsiers and Anthropoidea (Platyrrhini, the New World monkeys, and Catarrhini, Old World monkeys and Hominoidea)]. The first three alternatives gain some support from the fossil record, and the fourth from morphology of the living Tarsius and molecular data. It is emphasized that the morphological characters employed in this study for Tarsius are based on the only surviving genus of once-diverse Tarsiiform primates known from the Eocene, and, although considered a "living fossil," it cannot represent all of them. Furthermore, Tarsius embodies derived features of its own which may affect its systematic position, but not necessarily the position of Tarsiiformes. Although the early Tertiary adapoids might have more nearly resembled anthropoids in their biochemistry and placental developments, this hypothesis is not testable from fossils, and any inferred relationships here must be based on characters of skeletal anatomy. Alternatively, anthropoids may be derived from certain omomyids or from some as yet undiscovered Eocene African taxon. Close relationships among Homo, Pan, and Gorilla have been confirmed during recent decades; Pongo is the sister group to this trichotomy. With increasing molecular data, Homo and Pan appear to be closer to each other than to any other living hominid taxon. Gorilla is a sister group to the Homo-Pan clade and Pongo is a sister group to all of them. Morphologists have given limited evidence for such a dichotomous grouping. In this study, we support the Homo-Pan clade, although with characters not as strong as for other clades.
Timothy B Rowe - One of the best experts on this subject based on the ideXlab platform.
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Cranial anatomy of the Duchesnean primate Rooneyia viejaensis: new insights from high resolution computed tomography.
Journal of human evolution, 2014Co-Authors: E. Christopher Kirk, Parham Daghighi, Thomas E. Macrini, Bhart-anjan S. Bhullar, Timothy B RoweAbstract:Rooneyia viejaensis is a North American Eocene primate of uncertain phylogenetic affinities. Although the external cranial anatomy of Rooneyia is well studied, various authors have suggested that Rooneyia is a stem haplorhine, stem strepsirrhine, stem Tarsiiform, or stem anthropoid. Here we describe the internal cranial anatomy of the Rooneyia holotype based on micro-computed tomography and discuss the phylogenetic implications of this anatomy. Precise measurements of the natural endocast filling the braincase of the Rooneyia holotype reveal that the genus had a relative brain size comparable to some living callitrichines and strepsirrhines. Rooneyia was thus probably more encephalized than any other known omomyiform, adapiform, or plesiadapiform. Relative olfactory bulb size in Rooneyia was most comparable to some living strepsirrhines and the stem anthropoid Parapithecus. The nasal fossa of Rooneyia resembled that of living strepsirrhines in retaining an obliquely oriented nasolacrimal canal, four ethmoturbinals, and an olfactory recess separated from the nasopharyngeal meatus by a transverse lamina. The ear region of Rooneyia is characterized by large and complete canals for both the stapedial and promontory branches of the internal carotid artery. Rooneyia also retains a patent parotic fissure and thus had an extrabullar origin of the stapedius muscle. In most of these respects, Rooneyia exhibits the condition that is presumed to be primitive for crown primates and lacks a number of key crown haplorhine synapomorphies (e.g., a dorso-ventrally oriented nasolacrimal canal, loss of the olfactory recess, loss of ethmoturbinals 3-4, loss or extreme reduction of the stapedial canal due to involution of the stapedial artery). These data are consistent with the hypothesis that Rooneyia is an advanced stem primate or a basal crown primate but are inconsistent with prior suggestions that Rooneyia is a crown haplorhine.
K. Christopher Beard - One of the best experts on this subject based on the ideXlab platform.
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Phalangeal morphology of Shanghuang fossil primates.
Journal of human evolution, 2017Co-Authors: Daniel L. Gebo, Marian Dagosto, K. Christopher BeardAbstract:Abstract Here, we describe hundreds of isolated phalanges attributed to middle Eocene fossil primates from the Shanghuang fissure-fillings from southern Jiangsu Province, China. Extending knowledge based on previous descriptions of postcranial material from Shanghuang, this sample of primate finger and toe bones includes proximal phalanges, middle phalanges, and over three hundred nail-bearing distal phalanges. Most of the isolated proximal and middle phalanges fall within the range of small-bodied individuals, suggesting an allocation to the smaller haplorhine primates identified at Shanghuang, including eosimiids. In contrast to the proximal and middle phalanges from Shanghuang, there are a variety of shapes, sizes, and possible taxonomic allocations for the distal phalanges. Two distal phalangeal morphologies are numerically predominant at Shanghuang. The sample of larger bodied specimens is best allocated to the medium-sized adapiform Adapoides while the smaller ones are allocated to eosimiids on the basis of the commonality of dental and tarsal remains of these taxa at Shanghuang. The digit morphology of Adapoides is similar morphologically to that of notharctines and cercamoniines, while eosimiid digit morphology is unlike living anthropoids. Other primate distal phalangeal morphologies at Shanghuang include grooming “claws” as well as specimens attributable to tarsiids, Tarsiiforms, the genus Macrotarsius , and a variety of adapiforms. One group of distal phalanges at Shanghuang is morphologically indistinguishable from those of living anthropoids. All of the phalanges suggest long fingers and toes for the fossil primates of Shanghaung, and their digit morphology implies arboreality with well-developed digital flexion and strong, grasping hands and feet.
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Distal phalanges of Eosimias and Hoanghonius
Journal of human evolution, 2015Co-Authors: Daniel L. Gebo, K. Christopher Beard, Marian DagostoAbstract:Seven primate distal phalanges have been identified from two middle Eocene fossil localities (Locality 1 and Nanbaotou) in the Yuanqu Basin, China, providing the first evidence of distal phalangeal morphology in Asian Eocene adapiform and eosimiid primates. The bones are best allocated to the basal anthropoid Eosimias centennicus and to hoanghoniine adapiforms. All distal phalangeal specimens display a morphology consistent with nail-bearing fingers and toes. The hallucal distal phalanx of the basal anthropoid Eosimias is more similar to that of primitive Tarsiiforms than to crown group anthropoids. The adapiform distal phalanges from Locality 1 are allocated to Hoanghonius stehlini while those from Nanbaotou are tentatively assigned to an indeterminate hoanghoniine because dental remains of adapiforms have yet to be identified from this site. The distal phalangeal anatomy of hoanghoniines differs slightly from that documented for adapines and notharctines. One distal phalanx from Locality 1 shows a second pedal digit "grooming claw" morphology as noted for notharctines by Maiolino et al. (2012) and cercamoniines by Von Koenigswald et al. (2012).
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The oldest known primate skeleton and early haplorhine evolution
Nature, 2013Co-Authors: Daniel L. Gebo, Marian Dagosto, Meng, Paul Tafforeau, John J. Flynn, K. Christopher BeardAbstract:Reconstructing the earliest phases of primate evolution has been impeded by gaps in the fossil record, so that disagreements persist regarding the palaeobiology and phylogenetic relationships of the earliest primates. Here we report the discovery of a nearly complete and partly articulated skeleton of a primitive haplorhine primate from the early Eocene of China, about 55 million years ago, the oldest fossil primate of this quality ever recovered. Coupled with detailed morphological examination using propagation phase contrast X-ray synchrotron microtomography, our phylogenetic analysis based on total available evidence indicates that this fossil is the most basal known member of the Tarsiiform clade. In addition to providing further support for an early dichotomy between the strepsirrhine and haplorhine clades, this new primate further constrains the age of divergence between Tarsiiforms and anthropoids. It also strengthens the hypothesis that the earliest primates were probably diurnal, arboreal and primarily insectivorous mammals the size of modern pygmy mouse lemurs.
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Phylogenetic and biogeographic significance of the Tarsiiform primate Asiomomys changbaicus from the eocene of Jilin Province, people's Republic of China
American Journal of Physical Anthropology, 1991Co-Authors: K. Christopher Beard, Banyue WangAbstract:A newly discovered Paleogene mammal locality in Jilin Province, People's Republic of China has yielded a dentary fragment of the Tarsiiform primate Asiomomys changbaicus. Unlike most other Eocene primates from Asia, the phylogenetic position of A. changbaicus is well resolved: it represents the sister taxon of Stockia powayensis, a probable washakiin omomyid from the early Uintan of southern California. The phylogenetic position and geographic provenance of A. changbaicus demonstrate the feasibility of primate dispersal between North America and Asia during middle Eocene time. This finding establishes a biogeographic link between the most diverse known radiation of Tarsiiform primates, which occurred in the Eocene of North America, and the present range of the genus Tarsius. Accordingly, biogeographic considerations no longer detract from the hypothesis of a close phylogenetic relationship between Tarsius and a clade of North American Omomyidae.
