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1. New Middle Miocene Ape (Primates: Hylobatidae) from Ramnagar, India fills major gaps in the hominoid fossil record

   https://doi.org/10.1098/rspb.2020.1655  

   Gilbert, Christopher C.; Ortiz, Alejandra; Pugh, Kelsey D.; Campisano, Christopher J.; Patel, Biren A.; Singh, Ningthoujam Premjit; Fleagle, John G.; Patnaik, Rajeev (September 2020, Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   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. 

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2. The complete sequence and comparative analysis of ape sex chromosomes

   https://doi.org/10.1038/s41586-024-07473-2  

   Makova, Kateryna D; Pickett, Brandon D; Harris, Robert S; Hartley, Gabrielle A; Cechova, Monika; Pal, Karol; Nurk, Sergey; Yoo, DongAhn; Li, Qiuhui; Hebbar, Prajna; et al (June 2024, Nature)

   Apes possess two sex chromosomes—the male-specific Y chromosome and the X chromosome, which is present in both males and females. The Y chromosome is crucial for male reproduction, with deletions being linked to infertility¹. The X chromosome is vital for reproduction and cognition². Variation in mating patterns and brain function among apes suggests corresponding differences in their sex chromosomes. However, owing to their repetitive nature and incomplete reference assemblies, ape sex chromosomes have been challenging to study. Here, using the methodology developed for the telomere-to-telomere (T2T) human genome, we produced gapless assemblies of the X and Y chromosomes for five great apes (bonobo (Pan paniscus), chimpanzee (Pan troglodytes), western lowland gorilla (Gorilla gorilla gorilla), Bornean orangutan (Pongo pygmaeus) and Sumatran orangutan (Pongo abelii)) and a lesser ape (the siamang gibbon (Symphalangus syndactylus)), and untangled the intricacies of their evolution. Compared with the X chromosomes, the ape Y chromosomes vary greatly in size and have low alignability and high levels of structural rearrangements—owing to the accumulation of lineage-specific ampliconic regions, palindromes, transposable elements and satellites. Many Y chromosome genes expand in multi-copy families and some evolve under purifying selection. Thus, the Y chromosome exhibits dynamic evolution, whereas the X chromosome is more stable. Mapping short-read sequencing data to these assemblies revealed diversity and selection patterns on sex chromosomes of more than 100 individual great apes. These reference assemblies are expected to inform human evolution and conservation genetics of non-human apes, all of which are endangered species. 

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3. First digital study of the frontal sinus of stem-Canini (Canidae, Carnivora): evolutionary and ecological insights throughout advanced diagnostic in paleobiology

   https://doi.org/10.3389/fevo.2023.1173341  

   Frosali, Samuele; Bartolini-Lucenti, Saverio; Madurell-Malapeira, Joan; Urciuoli, Alessandro; Costeur, Loïc; Rook, Lorenzo (May 2023, Frontiers in Ecology and Evolution)

   IntroductionThe phylogenetic and ecological importance of paranasal sinuses in carnivorans was highlighted by several previous authors, mostly in extant species. Nevertheless, no specific study on this feature on extant canids, and no one on fossil representatives of the family, has been published up to now. Here, we analyze for the first time the paranasal sinus of extant and fossil canids through computed tomographic techniques to characterize them morphologically and morphometrically, making ecological inferences. MethodsTo do so, we applied for the first time an innovative deformation-based morphometric approach. ResultsThe results obtained for extant species highlight a remarkable correlation between morphology and ecomorphotypes previously defined by some scholars (namely hypercarnivorous group-hunters; small-prey hypercarnivores, mesocarnivores, hypocarnivores). Our results thus support the direct relationship between diet preferences and the development of frontal sinus in canids. Regarding fossil specimens, we reconstructed for the first time the frontal sinus of threeEucyonspecies and compared it to those of living forms. DiscussionThe best-preserved specimen, the only known cranium ofEucyon adoxusdated to the Late Pliocene of Saint-Estève (France), displayed similarities with hypercarnivorous group-hunter canids by the large sinus prominences. Given that the overall craniodental morphology ofE. adoxussuggests that it acted as a small prey hypercarnivore—similar to extantCanis simensis—the aforementioned affinities might have evolved independently, in relation to high stresses during feeding. Overall, our study demonstrates that morphological inspection and deformation-based geometric morphometrics complement each other and allow a thorough investigation of sinus shape variability, thus enabling the study of sinus morphology in other fossil carnivorans with the ultimate goal of inferring their ecological preferences. 

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4. Neuroanatomy of the crocodylian Tomistoma dowsoni from the Miocene of North Africa provides insights into the evolutionary history of gavialoids

   https://doi.org/10.1111/joa.13846  

   Burke, Paul_M J; Mannion, Philip D (July 2023, Journal of Anatomy)

   Abstract The interrelationships of the extant crocodyliansGavialis gangeticusandTomistoma schlegeliihave been historically disputed. Whereas molecular analyses indicate a sister taxon relationship between these two gavialoid species, morphological datasets typically placeGavialisas the outgroup to all other extant crocodylians. Recent morphological‐based phylogenetic analyses have begun to resolve this discrepancy, recoveringGavialisas the closest living relative ofTomistoma; however, several stratigraphically early fossil taxa are recovered as closer toGavialisthanTomistoma, resulting in anomalously early divergence timings. As such, additional morphological data might be required to resolve these remaining discrepancies. ‘Tomistoma’dowsoniis an extinct species of gavialoid from the Miocene of North Africa. Utilising CT scans of a near‐complete, referred skull, we reconstruct the neuroanatomy and neurosensory apparatus of ‘Tomistoma’dowsoni. Based on qualitative and quantitative morphometric comparisons with other crocodyliforms, the neuroanatomy of ‘Tomistoma’dowsoniis characterised by an intermediate morphology between the two extant gavialoids, more closely resemblingGavialis. This mirrors the results of recent studies based on the external anatomy of these three species and other fossil gavialoids. Several neuroanatomical features of these species appear to reflect ecological and/or phylogenetic signals. For example, the ‘simple’ morphology of their neurosensory apparatus is broadly similar to that of other long and narrow‐snouted (longirostrine), aquatic crocodyliforms. A dorsoventrally short, anteroposteriorly long endosseous labyrinth is also associated with longirostry. These features indicate that snout and skull morphology, which are themselves partly constrained by ecology, exert an influence on neuroanatomical morphology, as has also been recognised in birds and turtles. Conversely, the presence of a pterygoid bulla inGavialisand several extinct gavialoids, and its absence inTomistoma schlegelii, could be interpreted as a phylogenetic signal of crocodylians more closely related toGavialis than toTomistoma. Evaluation of additional fossil gavialoids will be needed to further test whether these and other neuroanatomical features primarily reflect a phylogenetic or ecological signal. By incorporating such previously inaccessible information of extinct and extant gavialoids into phylogenetic and macroecological studies, we can potentially further constrain the clade's interrelationships, as well as evaluate the timing and ecological association of the evolution of these neuroanatomical features. Finally, our study supports recent phylogenetic analyses that place ‘Tomistoma’dowsonias being phylogenetically closer toGavialis gangeticusthan toTomistoma schlegelii, indicating the necessity of a taxonomic revision of this fossil species. 

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5. The evolution of hominoid locomotor versatility: Evidence from Moroto, a 21 Ma site in Uganda

   https://doi.org/10.1126/science.abq2835  

   MacLatchy, Laura M.; Cote, Susanne M.; Deino, Alan L.; Kityo, Robert M.; Mugume, Amon A.; Rossie, James B.; Sanders, William J.; Cosman, Miranda N.; Driese, Steven G.; Fox, David L.; et al (April 2023, Science)

   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 ). 

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