An official website of the United States government
Fossil gibbons are exceedingly rare, with much of the hylobatid fossil record and, consequently, hylobatid evolutionary history remaining unknown. Kapi ramnagarensis was described as a stem hylobatid on the basis of an isolated lower right M3 from ~13.0-12.5 Ma deposits surrounding Ramnagar (J&K), India. This interpretation was recently challenged, with alternative hypotheses suggesting that it is instead a stem catarrhine or a strangely derived pliopithecoid that has converged on hylobatid morphology. A series of morphological features were said to distinguish Kapi from fossil and extant hylobatids; notably, however, none of these features were examined or compared using quantitative analyses. Here, we further examine the dental morphology of Kapi, providing quantitative analyses to critically evaluate the hypothesis that Kapi represents a stem catarrhine or pliopithecoid rather than a stem hylobatid. Results demonstrate that none of the claimed differences between Kapi and hylobatids hold up under closer scrutiny, and multivariate discriminant analyses taking size and shape into account strongly support Kapi as a hylobatid with high posterior probabilities. Although only represented by a single lower molar, Kapi remains the most compelling candidate for the earliest known hylobatid in the fossil record and thus likely documents the simultaneous arrival of lesser and great apes to Asia during the Middle Miocene.
more »
« less
New Middle Miocene Ape (Primates: Hylobatidae) from Ramnagar, India fills major gaps in the hominoid fossil record
The fossil record of ‘lesser apes’ (i.e. hylobatids = gibbons and siamangs) is virtually non-existent before the latest Miocene of East Asia. However, molecular data strongly and consistently suggest that hylobatids should be present by approximately 20 Ma; thus, there are large temporal, geographical, and morphological gaps between early fossil apes in Africa and the earliest fossil hylobatids in China. Here, we describe a new approximately 12.5–13.8 Ma fossil ape from the Lower Siwaliks of Ramnagar, India, that fills in these long-standing gaps with implications for hylobatid origins. This ape represents the first new hominoid species discovered at Ramnagar in nearly a century, the first new Siwalik ape taxon in more than 30 years, and likely extends the hylobatid fossil record by approximately 5 Myr, providing a minimum age for hylobatid dispersal coeval to that of great apes. The presence of crown hylobatid molar features in the new species indicates an adaptive shift to a more frugivorous diet during the Middle Miocene, consistent with other proposed adaptations to frugivory (e.g. uricase gene silencing) during this time period as well.
more »
« less
- PAR ID:
- 10276298
- Date Published:
- Journal Name:
- Proceedings of the Royal Society B: Biological Sciences
- Volume:
- 287
- Issue:
- 1934
- ISSN:
- 0962-8452
- Page Range / eLocation ID:
- 20201655
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
INTRODUCTION Inherent in traditional views of ape origins is the idea that, like living apes, early large-bodied apes lived in tropical forests. In response to constraints related to locomoting in forest canopies, it has been proposed that early apes evolved their quintessential upright torsos and acrobatic climbing and suspensory abilities, enhancing their locomotor versatility, to distribute their weight among small supports and thus reach ripe fruit in the terminal branches. This feeding and locomotor transition from a quadruped with a horizontal torso is thought to have occurred in the Middle Miocene due to an increasingly seasonal climate and feeding competition from evolving monkeys. Although ecological and behavioral comparisons among living apes and monkeys provide evidence for versions of terminal branch forest frugivory hypotheses, corroboration from the early ape fossil record has been lacking, as have detailed reconstructions of the habitats where the first apes evolved. RATIONALE The Early Miocene fossil site of Moroto II in Uganda provides a unique opportunity to test the predictions of terminal branch forest frugivory hypotheses. Moroto II documents the oldest [21 million years ago (Ma)] well-established paleontological record of ape teeth and postcranial bones from a single locality and preserves paleoecological proxies to reconstruct the environment. The following lines of evidence from Moroto II were analyzed: (i) the functional anatomy of femora and a vertebra attributed to the ape Morotopithecus ; (ii) dental traits, including molar shape and isotopic profiles of Morotopithecus enamel; (iii) isotopic dietary paleoecology of associated fossil mammals; (iv) biogeochemical signals from paleosols (ancient soils) that reflect local relative proportions of C 3 (trees and shrubs) and C 4 (tropical grasses and sedges that can endure water stress) vegetation as well as rainfall; and (v) assemblages of phytoliths, microscopic plant-derived silica bodies that reflect past plant communities. RESULTS A short, strong femur biomechanically favorable to vertical climbing and a vertebra indicating a dorsostable lower back confirm that ape fossils from Moroto II shared locomotor traits with living apes. Both Morotopithecus and a smaller ape from the site have elongated molars with well-developed crests for shearing leaves. Carbon isotopic signatures of the enamel of these apes and of other fossil mammals indicate that some mammals consistently fed on water-stressed C 3 plants, and possibly also C 4 vegetation, in a woodland setting. Carbon isotope values of pedogenic carbonates, paleosol organic matter, and plant waxes all point to substantial C 4 grass biomass on the landscape. Analysis of paleosols also indicates subhumid, strongly seasonal rainfall, and phytolith assemblages include forms from both arid-adapted C 4 grasses and forest-indicator plants. CONCLUSION The ancient co-occurrence of dental specializations for leaf eating, rather than ripe fruit consumption, along with ape-like locomotor abilities counters the predictions of the terminal branch forest frugivory hypotheses. The combined paleoecological evidence situates Morotopithecus in a woodland with a broken canopy and substantial grass understory including C 4 species. These findings call for a new paradigm for the evolutionary origins of early apes. We propose that seasonal, wooded environments may have exerted previously unrecognized selective pressures in the evolution of arboreal apes. For example, some apes may have needed to access leaves in the higher canopy in times of low fruit availability and to be adept at ascending and descending from trees that lacked a continuous canopy. Hominoid habitat comparisons. Shown are reconstructions of a traditionally conceived hominoid habitat ( A ) and the 21 Ma Moroto II, Uganda, habitat ( B ).more » « less
-
Pierolapithecus catalaunicus(~12 million years ago, northeastern Spain) is key to understanding the mosaic nature of hominid (great ape and human) evolution. Notably, its skeleton indicates that an orthograde (upright) body plan preceded suspensory adaptations in hominid evolution. However, there is ongoing debate about this species, partly because the sole known cranium, preserving a nearly complete face, suffers from taphonomic damage. We 1) carried out a micro computerized tomography (CT) based virtual reconstruction of thePierolapithecuscranium, 2) assessed its morphological affinities using a series of two-dimensional (2D) and three-dimensional (3D) morphometric analyses, and 3) modeled the evolution of key aspects of ape face form. The reconstruction clarifies many aspects of the facial morphology ofPierolapithecus. Our results indicate that it is most similar to great apes (fossil and extant) in overall face shape and size and is morphologically distinct from other Middle Miocene apes. Crown great apes can be distinguished from other taxa in several facial metrics (e.g., low midfacial prognathism, relatively tall faces) and only some of these features are found inPierolapithecus, which is most consistent with a stem (basal) hominid position. The inferred morphology at all ancestral nodes within the hominoid (ape and human) tree is closer to great apes than to hylobatids (gibbons and siamangs), which are convergent with other smaller anthropoids. Our analyses support a hominid ancestor that was distinct from all extant and fossil hominids in overall facial shape and shared many features withPierolapithecus. This reconstructed ancestral morphotype represents a testable hypothesis that can be reevaluated as new fossils are discovered.more » « less
-
Abstract The fossil record of treeshrews, hedgehogs, and other micromammals from the Lower Siwaliks of India is sparse. Here, we report on a new genus and species of fossil treeshrew, specimens of the hedgehog Galerix , and other micromammals from the middle Miocene (Lower Siwalik) deposits surrounding Ramnagar (Udhampur District, Jammu and Kashmir), at a fossil locality known as Dehari. The treeshrew from Dehari ( Sivatupaia ramnagarensis n. gen. n. sp.) currently represents the oldest record of fossil tupaiids in the Siwaliks, extending their time range by ca. 2.5–4.0 Myr in the region. Dietary analyses suggest that the new tupaiid was likely adapted for a less mechanically challenging or more frugivorous diet compared to other extant and fossil tupaiids. The occurrence of Galerix has only been recently documented from the Indian Siwaliks and the Dehari specimens help establish the likely presence of a relatively large Siwalik Galerix species in the Ramnagar region. In addition to the new treeshrew and hedgehogs, new specimens of the rodents Kanisamys indicus , Sayimys sivalensis , and Murinae indet. from Dehari help confirm that age estimates for the Ramnagar region are equivalent to the Chinji Formation in Pakistan, most likely corresponding to the middle to upper part of the Chinji Formation. UUID: http://zoobank.org/56fb160c-2df8-4cd3-be91-af4dc02d0979more » « less
-
Eastern African terrestrial ecosystems in the Early Miocene are characterized by habitat heterogeneity resulting from local rifting, climate variation, and biogeography. These dynamic landscapes profoundly influenced the evolutionary trajectories of hominoids and other mammals. In western Kenya, a collection of Early Miocene fossil-rich sites (ca. 20 Ma) proximate to the extinct Tinderet Volcano, offers a unique window into understanding habitat preferences and ecological drivers to the evolution of hominoids. Here, we present data from one of the sites, Koru 16, with evidence of remarkably preserved fossil fauna, fossil leaves, tree stump casts, and paleosols, to provide invaluable insights into the ancient ecological dynamics of the region. We use multiple proxies to reconstruct the paleoclimate and paleoecology of the Koru 16 site. The lithofacies of the Koru 16 area are characterized as interbedded ash and weakly developed paleosols indicating episodic landscape disturbance from eruptions of the volcano followed by intervals of stability. Paleosol features together with paleoclimate estimates using two models based on elemental weathering (RF-MAP and PPM) indicate warm and wet conditions. More than 1000 fossil leaves collected from two stratigraphic locations at Koru 16 yielded seventeen morphotypes which were identified across both localities and displaying different distributions of morphotypes between them. The average leaf size of morphotypes form both localities is mesophyll to megaphyll and mean annual precipitation estimates using multiple leaf physiognomic methods indicate >2000 mm/yr. Leaf lifespan estimates derived from the leaf mass per area (MA) proxy suggest that the site was predominantly characterized by evergreen taxa, with limited deciduous taxa. The distribution of MA is consistent with tropical rainforests and tropical seasonal forests in equatorial Africa, indicating similarities in leaf characteristics and ecological patterns. Tree stump casts corroborate this observation, as they indicate an open forest, with density similar to modern tropical forests that support large-bodied primates. The fauna includes a medium- sized pythonid, and at least two species of apes, along with other mammalian taxa typical for the early Miocene. Our comprehensive paleoclimate and paleoecological analyses suggest that the Koru 16 site was very warm and wet, which is a climate conducive for a tropical seasonal forest transitioning into a rainforest biome. This environmental reconstruction underscores the broad distribution of Early Miocene apes in a variety of habitats, and calls into question a recent hypothesis that apes only lived in environments with a significant open component.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1098/rspb.2020.1655
