Browsing by Subject "Fossils"

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Open Access
A diminutive Pliocene guenon from Kanapoi, West Turkana, Kenya.
(Journal of human evolution, 2019-10) Plavcan, J Michael; Ward, Carol V; Kay, Richard F; Manthi, Fredrick K
Although modern guenons are diverse and abundant in Africa, the fossil record of this group is surprisingly sparse. In 2012 the West Turkana Paleo Project team recovered two associated molar teeth of a small primate from the Pliocene site of Kanapoi, West Turkana, Kenya. The teeth are bilophodont and the third molar lacks a hypoconulid, which is diagnostic for Cercopithecini. The teeth are the same size as those of extant Miopithecus, which is thought to be a dwarfed guenon, as well as a partial mandible preserving two worn teeth, previously recovered from Koobi Fora, Kenya, which was also tentatively identified as a guenon possibly allied with Miopithecus. Tooth size and proportions, as well as analysis of relative cusp size and shearing crest development clearly separate the fossil from all known guenons. Based on the Kanapoi material, we erect a new genus and species, Nanopithecus browni gen. et sp. nov. The small size of the specimen suggests either that dwarfing occurred early in the lineage, or at least twice independently, depending on the relationship of the new species with extant Miopithecus. Further, the distinctive habitat and geographic separation from Miopithecus suggests that the origin of small body size is not uniquely linked to the current habitat of Miopithecus, and possibly that relatives of extant Miopithecus were much more widely distributed in the past. This in turn argues caution in using extant biogeography in models of the origins of at least some guenons.
Open Access
Anthropology. New World monkey origins.
(Science, 2015-03-06) Kay, Richard Frederick
Open Access
Assessing Bayesian Phylogenetic Information Content of Morphological Data Using Knowledge From Anatomy Ontologies.
(Systematic biology, 2022-10) Porto, Diego S; Dahdul, Wasila M; Lapp, Hilmar; Balhoff, James P; Vision, Todd J; Mabee, Paula M; Uyeda, Josef
Morphology remains a primary source of phylogenetic information for many groups of organisms, and the only one for most fossil taxa. Organismal anatomy is not a collection of randomly assembled and independent "parts", but instead a set of dependent and hierarchically nested entities resulting from ontogeny and phylogeny. How do we make sense of these dependent and at times redundant characters? One promising approach is using ontologies-structured controlled vocabularies that summarize knowledge about different properties of anatomical entities, including developmental and structural dependencies. Here, we assess whether evolutionary patterns can explain the proximity of ontology-annotated characters within an ontology. To do so, we measure phylogenetic information across characters and evaluate if it matches the hierarchical structure given by ontological knowledge-in much the same way as across-species diversity structure is given by phylogeny. We implement an approach to evaluate the Bayesian phylogenetic information (BPI) content and phylogenetic dissonance among ontology-annotated anatomical data subsets. We applied this to data sets representing two disparate animal groups: bees (Hexapoda: Hymenoptera: Apoidea, 209 chars) and characiform fishes (Actinopterygii: Ostariophysi: Characiformes, 463 chars). For bees, we find that BPI is not substantially explained by anatomy since dissonance is often high among morphologically related anatomical entities. For fishes, we find substantial information for two clusters of anatomical entities instantiating concepts from the jaws and branchial arch bones, but among-subset information decreases and dissonance increases substantially moving to higher-level subsets in the ontology. We further applied our approach to address particular evolutionary hypotheses with an example of morphological evolution in miniature fishes. While we show that phylogenetic information does match ontology structure for some anatomical entities, additional relationships and processes, such as convergence, likely play a substantial role in explaining BPI and dissonance, and merit future investigation. Our work demonstrates how complex morphological data sets can be interrogated with ontologies by allowing one to access how information is spread hierarchically across anatomical concepts, how congruent this information is, and what sorts of processes may play a role in explaining it: phylogeny, development, or convergence. [Apidae; Bayesian phylogenetic information; Ostariophysi; Phenoscape; phylogenetic dissonance; semantic similarity.].
Open Access
Auditory morphology and hearing sensitivity in fossil New World monkeys.
(Anatomical record (Hoboken, N.J. : 2007), 2010-10) Coleman, M; Kay, RF; Colbert, MW
In recent years it has become possible to investigate the hearing capabilities in fossils by analogy with studies in living taxa that correlate the bony morphology of the auditory system with hearing sensitivity. In this analysis, we used a jack-knife procedure to test the accuracy of one such study that examined the functional morphology of the primate auditory system and we found that low-frequency hearing (sound pressure level at 250 Hz) can be predicted with relatively high confidence (±3-8 dB depending on the structure). Based on these functional relationships, we then used high-resolution computed tomography to examine the auditory region of three fossil New World monkeys (Homunculus, Dolicocebus, and Tremacebus) and compared their morphology and predicted low-frequency sensitivity with a phylogenetically diverse sample of extant primates. These comparisons reveal that these extinct taxa shared many auditory characteristics with living platyrrhines. However, the fossil with the best preserved auditory region (Homunculus) also displayed a few unique features such as the relative size of the tympanic membrane and stapedial footplate and the degree of trabeculation of the anterior accessory cavity. Still, the majority of evidence suggests that these fossil species likely had similar low-frequency sensitivity to extant South American monkeys. This research adds to the small but growing body of evidence on the evolution of hearing abilities in extinct taxa and lays the groundwork for predicting hearing sensitivity in additional fossil primate specimens.
Open Access
Biogeography in deep time - What do phylogenetics, geology, and paleoclimate tell us about early platyrrhine evolution?
(Mol Phylogenet Evol, 2015-01) Kay, Richard Frederick
Molecular data have converged on a consensus about the genus-level phylogeny of extant platyrrhine monkeys, but for most extinct taxa and certainly for those older than the Pleistocene we must rely upon morphological evidence from fossils. This raises the question as to how well anatomical data mirror molecular phylogenies and how best to deal with discrepancies between the molecular and morphological data as we seek to extend our phylogenies to the placement of fossil taxa. Here I present parsimony-based phylogenetic analyses of extant and fossil platyrrhines based on an anatomical dataset of 399 dental characters and osteological features of the cranium and postcranium. I sample 16 extant taxa (one from each platyrrhine genus) and 20 extinct taxa of platyrrhines. The tree structure is constrained with a "molecular scaffold" of extant species as implemented in maximum parsimony using PAUP with the molecular-based 'backbone' approach. The data set encompasses most of the known extinct species of platyrrhines, ranging in age from latest Oligocene (∼26 Ma) to the Recent. The tree is rooted with extant catarrhines, and Late Eocene and Early Oligocene African anthropoids. Among the more interesting patterns to emerge are: (1) known early platyrrhines from the Late Oligocene through Early Miocene (26-16.5Ma) represent only stem platyrrhine taxa; (2) representatives of the three living platyrrhine families first occur between 15.7 Ma and 13.5 Ma; and (3) recently extinct primates from the Greater Antilles (Cuba, Jamaica, Hispaniola) are sister to the clade of extant platyrrhines and may have diverged in the Early Miocene. It is probable that the crown platyrrhine clade did not originate before about 20-24 Ma, a conclusion consistent with the phylogenetic analysis of fossil taxa presented here and with recent molecular clock estimates. The following biogeographic scenario is consistent with the phylogenetic findings and climatic and geologic evidence: Tropical South America has been a center for platyrrhine diversification since platyrrhines arrived on the continent in the middle Cenozoic. Platyrrhines dispersed from tropical South America to Patagonia at ∼25-24 Ma via a "Paraná Portal" through eastern South America across a retreating Paranense Sea. Phylogenetic bracketing suggests Antillean primates arrived via a sweepstakes route or island chain from northern South America in the Early Miocene, not via a proposed land bridge or island chain (GAARlandia) in the Early Oligocene (∼34 Ma). Patagonian and Antillean platyrrhines went extinct without leaving living descendants, the former at the end of the Early Miocene and the latter within the past six thousand years. Molecular evidence suggests crown platyrrhines arrived in Central America by crossing an intermittent connection through the Isthmus of Panama at or after 3.5Ma. Any more ancient Central American primates, should they be discovered, are unlikely to have given rise to the extant Central American taxa in situ.
Open Access
Catarrhine hallucal metatarsals from the early Miocene site of Songhor, Kenya.
(Journal of human evolution, 2017-07) Patel, Biren A; Yapuncich, Gabriel S; Tran, Cassandra; Nengo, Isaiah O
Songhor is an early Miocene fossil locality in Kenya known for its diverse primate assemblage that includes catarrhine species belonging to the genera Kalepithecus, Limnopithecus, Dendropithecus, Rangwapithecus, and Proconsul. Expeditions to Songhor since the 1930s have recovered unassociated catarrhine postcranial remains from both the fore- and hindlimbs, including multiple elements from the feet. In this study, we describe KNM-SO 31233, a complete left hallucal metatarsal (Mt1), along with several other fragmentary Mt1 specimens (KNM-SO 1080, 5129, 5141, 22235). These fossils were compared to extant catarrhines and platyrrhines, as well as available fossil Miocene catarrhine Mt1s. Morphometric data were obtained from 3D surface renderings and subjected to a number of analyses to assess their phenetic affinity with the comparative sample, make predictions of body mass, and to infer their functional morphology. The size and shape of the Songhor Mt1s are diverse, exhibiting a large robust morph (KNM-SO 5141) similar in size but not in shape to extant African apes, medium-sized morphs (KNM-SO 1080, 5129 and 22235), and a smaller, slender one (KNM-SO 31233) that has a shape resembling arboreal quadrupedal leaping monkeys and suspensory atelines and hylobatids. KNM-SO 31233 is unlike other known fossil Mt1s, and in general, none of the Songhor Mt1s resembled any single extant anthropoid clade or species. The morpho-functional diversity of Songhor Mt1s is consistent with an extensive morphological and phylogenetic catarrhine diversity in the early part of the Miocene epoch.
Open Access
Darwinius masillae is a strepsirrhine--a reply to Franzen et al. (2009).
(Journal of human evolution, 2010-11) Williams, Blythe A; Kay, Richard F; Kirk, E Christopher; Ross, Callum F
Open Access
Estimating the normal background rate of species extinction.
(Conservation biology : the journal of the Society for Conservation Biology, 2015-04) De Vos, Jurriaan M; Joppa, Lucas N; Gittleman, John L; Stephens, Patrick R; Pimm, Stuart L
A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100-1000 times pre-human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard-bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification-the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over- and under-estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre-human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05-0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher.
Open Access
Evidence for a single loss of mineralized teeth in the common avian ancestor.
(Science, 2014-12-12) Meredith, Robert W; Zhang, Guojie; Gilbert, M Thomas P; Jarvis, Erich D; Springer, Mark S
Edentulism, the absence of teeth, has evolved convergently among vertebrates, including birds, turtles, and several lineages of mammals. Instead of teeth, modern birds (Neornithes) use a horny beak (rhamphotheca) and a muscular gizzard to acquire and process food. We performed comparative genomic analyses representing lineages of nearly all extant bird orders and recovered shared, inactivating mutations within genes expressed in both the enamel and dentin of teeth of other vertebrate species, indicating that the common ancestor of modern birds lacked mineralized teeth. We estimate that tooth loss, or at least the loss of enamel caps that provide the outer layer of mineralized teeth, occurred about 116 million years ago.
Open Access
Ferns diversified in the shadow of angiosperms.
(Nature, 2004-04) Schneider, Harald; Schuettpelz, Eric; Pryer, Kathleen M; Cranfill, Raymond; Magallón, Susana; Lupia, Richard
The rise of angiosperms during the Cretaceous period is often portrayed as coincident with a dramatic drop in the diversity and abundance of many seed-free vascular plant lineages, including ferns. This has led to the widespread belief that ferns, once a principal component of terrestrial ecosystems, succumbed to the ecological predominance of angiosperms and are mostly evolutionary holdovers from the late Palaeozoic/early Mesozoic era. The first appearance of many modern fern genera in the early Tertiary fossil record implies another evolutionary scenario; that is, that the majority of living ferns resulted from a more recent diversification. But a full understanding of trends in fern diversification and evolution using only palaeobotanical evidence is hindered by the poor taxonomic resolution of the fern fossil record in the Cretaceous. Here we report divergence time estimates for ferns and angiosperms based on molecular data, with constraints from a reassessment of the fossil record. We show that polypod ferns (> 80% of living fern species) diversified in the Cretaceous, after angiosperms, suggesting perhaps an ecological opportunistic response to the diversification of angiosperms, as angiosperms came to dominate terrestrial ecosystems.
Open Access
First virtual endocasts of adapiform primates.
(Journal of human evolution, 2016-10) Harrington, Arianna R; Silcox, Mary T; Yapuncich, Gabriel S; Boyer, Doug M; Bloch, Jonathan I
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.
Open Access
Footprint evidence of early hominin locomotor diversity at Laetoli, Tanzania.
(Nature, 2021-12) McNutt, Ellison J; Hatala, Kevin G; Miller, Catherine; Adams, James; Casana, Jesse; Deane, Andrew S; Dominy, Nathaniel J; Fabian, Kallisti; Fannin, Luke D; Gaughan, Stephen; Gill, Simone V; Gurtu, Josephat; Gustafson, Ellie; Hill, Austin C; Johnson, Camille; Kallindo, Said; Kilham, Benjamin; Kilham, Phoebe; Kim, Elizabeth; Liutkus-Pierce, Cynthia; Maley, Blaine; Prabhat, Anjali; Reader, John; Rubin, Shirley; Thompson, Nathan E; Thornburg, Rebeca; Williams-Hatala, Erin Marie; Zimmer, Brian; Musiba, Charles M; DeSilva, Jeremy M
Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage^1-3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity^3-5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of footprints at site A are readily distinguished from those at site G, indicating that a minimum of two hominin taxa with different feet and gaits coexisted at Laetoli.
Open Access
Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa.
(eLife, 2015-09) Dirks, Paul HGM; Berger, Lee R; Roberts, Eric M; Kramers, Jan D; Hawks, John; Randolph-Quinney, Patrick S; Elliott, Marina; Musiba, Charles M; Churchill, Steven E; de Ruiter, Darryl J; Schmid, Peter; Backwell, Lucinda R; Belyanin, Georgy A; Boshoff, Pedro; Hunter, K Lindsay; Feuerriegel, Elen M; Gurtov, Alia; Harrison, James du G; Hunter, Rick; Kruger, Ashley; Morris, Hannah; Makhubela, Tebogo V; Peixotto, Becca; Tucker, Steven
We describe the physical context of the Dinaledi Chamber within the Rising Star cave, South Africa, which contains the fossils of Homo naledi. Approximately 1550 specimens of hominin remains have been recovered from at least 15 individuals, representing a small portion of the total fossil content. Macro-vertebrate fossils are exclusively H. naledi, and occur within clay-rich sediments derived from in situ weathering, and exogenous clay and silt, which entered the chamber through fractures that prevented passage of coarser-grained material. The chamber was always in the dark zone, and not accessible to non-hominins. Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition. Hominins accumulated over time as older laminated mudstone units and sediment along the cave floor were eroded. Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date.
Open Access
Hands of early primates.
(American journal of physical anthropology, 2013-12) Boyer, Doug M; Yapuncich, Gabriel S; Chester, Stephen GB; Bloch, Jonathan I; Godinot, Marc
Questions surrounding the origin and early evolution of primates continue to be the subject of debate. Though anatomy of the skull and inferred dietary shifts are often the focus, detailed studies of postcrania and inferred locomotor capabilities can also provide crucial data that advance understanding of transitions in early primate evolution. In particular, the hand skeleton includes characteristics thought to reflect foraging, locomotion, and posture. Here we review what is known about the early evolution of primate hands from a comparative perspective that incorporates data from the fossil record. Additionally, we provide new comparative data and documentation of skeletal morphology for Paleogene plesiadapiforms, notharctines, cercamoniines, adapines, and omomyiforms. Finally, we discuss implications of these data for understanding locomotor transitions during the origin and early evolutionary history of primates. Known plesiadapiform species cannot be differentiated from extant primates based on either intrinsic hand proportions or hand-to-body size proportions. Nonetheless, the presence of claws and a different metacarpophalangeal [corrected] joint form in plesiadapiforms indicate different grasping mechanics. Notharctines and cercamoniines have intrinsic hand proportions with extremely elongated proximal phalanges and digit rays relative to metacarpals, resembling tarsiers and galagos. But their hand-to-body size proportions are typical of many extant primates (unlike those of tarsiers, and possibly Teilhardina, which have extremely large hands). Non-adapine adapiforms and omomyids exhibit additional carpal features suggesting more limited dorsiflexion, greater ulnar deviation, and a more habitually divergent pollex than observed plesiadapiforms. Together, features differentiating adapiforms and omomyiforms from plesiadapiforms indicate increased reliance on vertical prehensile-clinging and grasp-leaping, possibly in combination with predatory behaviors in ancestral euprimates.
Open Access
Hip extensor mechanics and the evolution of walking and climbing capabilities in humans, apes, and fossil hominins.
(Proceedings of the National Academy of Sciences of the United States of America, 2018-04-02) Kozma, Elaine E; Webb, Nicole M; Harcourt-Smith, William EH; Raichlen, David A; D'Août, Kristiaan; Brown, Mary H; Finestone, Emma M; Ross, Stephen R; Aerts, Peter; Pontzer, Herman
The evolutionary emergence of humans' remarkably economical walking gait remains a focus of research and debate, but experimentally validated approaches linking locomotor capability to postcranial anatomy are limited. In this study, we integrated 3D morphometrics of hominoid pelvic shape with experimental measurements of hip kinematics and kinetics during walking and climbing, hamstring activity, and passive range of hip extension in humans, apes, and other primates to assess arboreal-terrestrial trade-offs in ischium morphology among living taxa. We show that hamstring-powered hip extension during habitual walking and climbing in living apes and humans is strongly predicted, and likely constrained, by the relative length and orientation of the ischium. Ape pelves permit greater extensor moments at the hip, enhancing climbing capability, but limit their range of hip extension, resulting in a crouched gait. Human pelves reduce hip extensor moments but permit a greater degree of hip extension, which greatly improves walking economy (i.e., distance traveled/energy consumed). Applying these results to fossil pelves suggests that early hominins differed from both humans and extant apes in having an economical walking gait without sacrificing climbing capability. Ardipithecus was capable of nearly human-like hip extension during bipedal walking, but retained the capacity for powerful, ape-like hip extension during vertical climbing. Hip extension capability was essentially human-like in Australopithecus afarensis and Australopithecus africanus, suggesting an economical walking gait but reduced mechanical advantage for powered hip extension during climbing.
Open Access
Oldest known cranium of a juvenile New World monkey (Early Miocene, Patagonia, Argentina): implications for the taxonomy and the molar eruption pattern of early platyrrhines.
(J Hum Evol, 2014-09) Perry, Jonathan MG; Kay, Richard F; Vizcaíno, Sergio F; Bargo, M Susana
A juvenile cranium of Homunculus patagonicus Ameghino, 1891a from the late Early Miocene of Santa Cruz Province (Argentina) provides the first evidence of developing cranial anatomy for any fossil platyrrhine. The specimen preserves the rostral part of the cranium with deciduous and permanent alveoli and teeth. The dental eruption sequence in the new specimen and a reassessment of eruption patterns in living and fossil platyrrhines suggest that the ancestral platyrrhine pattern of tooth replacement was for the permanent incisors to erupt before M(1), not an accelerated molar eruption (before the incisors) as recently proposed. Two genera and species of Santacrucian monkeys are now generally recognized: H. patagonicus Ameghino, 1891a and Killikaike blakei Tejedor et al., 2006. Taxonomic allocation of Santacrucian monkeys to these species encounters two obstacles: 1) the (now lost) holotype and a recently proposed neotype of H. patagonicus are mandibles from different localities and different geologic members of the Santa Cruz Formation, separated by approximately 0.7 million years, whereas the holotype of K. blakei is a rostral part of a cranium without a mandible; 2) no Santacrucian monkey with associated cranium and mandible has ever been found. Bearing in mind these uncertainties, our examination of the new specimen as well as other cranial specimens of Santacrucian monkeys establishes the overall dental and cranial similarity between the holotype of Killikaike blakei, adult cranial material previously referred to H. patagonicus, and the new juvenile specimen. This leads us to conclude that Killikaike blakei is a junior subjective synonym of H. patagonicus.
Open Access
Parvimico materdei gen. et sp. nov.: A new platyrrhine from the Early Miocene of the Amazon Basin, Peru.
(Journal of human evolution, 2019-09) Kay, Richard F; Gonzales, Lauren A; Salenbien, Wout; Martinez, Jean-Noël; Cooke, Siobhán B; Valdivia, Luis Angel; Rigsby, Catherine; Baker, Paul A
Three field seasons of exploration along the Río Alto Madre de Dios in Peruvian Amazonia have yielded a fauna of micromammals from a new locality AMD-45, at ∼12.8°S. So far we have identified the new primate described here as well as small caviomorph rodents, cenolestoid marsupials, interatheriid notoungulates, xenarthrans, fish, lizards and invertebrates. The site is in the Bala Formation as exposed where the river transects a syncline. U-Pb dates on detrital zircons constrain the locality's age at between 17.1 ± 0.7 Ma and 18.9 ± 0.7 Ma, making the fauna age-equivalent to that from the Pinturas Formation and the older parts of the Santa Cruz Formation of Patagonian Argentina (Santacrucian). The primate specimen is an unworn M1 of exceptionally small size (equivalent in size to the extant callitrichine, Callithrix jacchus, among the smallest living platyrrhines and the smallest Eocene-Early Miocene platyrrhine yet recorded). Despite its small size it is unlike extant callitrichines in having a prominent cingulum hypocone. Based on the moderate development of the buccal crests, this animal likely had a diet similar to that of frugivorous callitrichines, and distinctly different from the more similarly-sized gummivores, Cebuella and C. jacchus. The phyletic position of the new taxon is uncertain, especially given the autapomorphic character of the tooth as a whole. Nevertheless, its unusual morphology hints at a wholly original and hitherto unknown Amazonian fauna, and reinforces the impression of the geographic separation of the Amazonian tropics from the more geographically isolated southerly parts of the continent in Early Miocene times.
Open Access
Predicting euarchontan body mass: A comparison of tarsal and dental variables.
(American journal of physical anthropology, 2015-07) Yapuncich, Gabriel S; Gladman, Justin T; Boyer, Doug M
Multiple meaningful ecological characterizations of a species revolve around body mass. Because body mass cannot be directly measured in extinct taxa, reliable body mass predictors are needed. Many published body mass prediction equations rely on dental dimensions, but certain skeletal dimensions may have a more direct and consistent relationship with body mass. We seek to evaluate the reliability of prediction equations for inferring euarchontan body mass based on measurements of the articular facet areas of the astragalus and calcaneus.Surface areas of five astragalar facets (n = 217 specimens) and two calcaneal facets (n = 163) were measured. Separate ordinary least squares and multiple regression equations are presented for different levels of taxonomic inclusivity, and the reliability of each equation is evaluated with the coefficient of determination, standard error of the estimate, mean prediction error, and the prediction sum of squares statistic. We compare prediction errors to published prediction equations that utilize dental and/or tarsal measures. Finally, we examine the effects of taxonomically specific regressions and apply our equations to a diverse set of non-primates.Our results reveal that predictions based on facet areas are more reliable than most linear dental or tarsal predictors. Multivariate approaches are often better than univariate methods, but require more information (making them less useful for fragmentary fossils). While some taxonomically specific regressions improve predictive ability, this is not true for all primate groups.Among individual facets, the ectal and fibular facets of the astragalus and the calcaneal cuboid facet are the best body mass predictors. Since these facets have primarily concave curvature and scale with positive allometry relative to body mass, it appears that candidate skeletal proxies for body mass can be identified based on their curvature and scaling coefficients.
Open Access
Preliminary notes on a newly discovered skull of the extinct monkey Antillothrix from Hispaniola and the origin of the Greater Antillean monkeys.
(J Hum Evol, 2011-01) Kay, RF; Hunt, KD; Beeker, CD; Conrad, GW; Johnson, CC; Keller, J
Open Access
Primate diversification inferred from phylogenies and fossils.
(Evolution; international journal of organic evolution, 2017-12) Herrera, James P
Biodiversity arises from the balance between speciation and extinction. Fossils record the origins and disappearance of organisms, and the branching patterns of molecular phylogenies allow estimation of speciation and extinction rates, but the patterns of diversification are frequently incongruent between these two data sources. I tested two hypotheses about the diversification of primates based on ∼600 fossil species and 90% complete phylogenies of living species: (1) diversification rates increased through time; (2) a significant extinction event occurred in the Oligocene. Consistent with the first hypothesis, analyses of phylogenies supported increasing speciation rates and negligible extinction rates. In contrast, fossils showed that while speciation rates increased, speciation and extinction rates tended to be nearly equal, resulting in zero net diversification. Partially supporting the second hypothesis, the fossil data recorded a clear pattern of diversity decline in the Oligocene, although diversification rates were near zero. The phylogeny supported increased extinction ∼34 Ma, but also elevated extinction ∼10 Ma, coinciding with diversity declines in some fossil clades. The results demonstrated that estimates of speciation and extinction ignoring fossils are insufficient to infer diversification and information on extinct lineages should be incorporated into phylogenetic analyses.

Browsing by Subject "Fossils"

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