Reassessment of the phylogenetic relationships of the late Miocene apes Hispanopithecus and Rudapithecus based on vestibular morphology

Abstract

Late Miocene great apes are key to reconstructing the ancestral morphotype from which earliest hominins evolved. Despite consensus that the late Miocene dryopith great apes Hispanopithecus laietanus (Spain) and Rudapithecus hungaricus (Hungary) are closely related (Hominidae), ongoing debate on their phylogenetic relationships with extant apes (stem hominids, hominines, or pongines) complicates our understanding of great ape and human evolution. To clarify this question, we rely on the morphology of the inner ear semicircular canals, which has been shown to be phylogenetically informative. Based on microcomputed tomography scans, we describe the vestibular morphology of Hispanopithecus and Rudapithecus, and compare them with extant hominoids using landmark-free deformation-based three-dimensional geometric morphometric analyses. We also provide critical evidence about the evolutionary patterns of the vestibular apparatus in living and fossil hominoids under different phylogenetic assumptions for dryopiths. Our results are consistent with the distinction of Rudapithecus and Hispanopithecus at the genus rank, and further support their allocation to the Hominidae based on their derived semicircular canal volumetric proportions. Compared with extant hominids, the vestibular morphology of Hispanopithecus and Rudapithecus most closely resembles that of African apes, and differs from the derived condition of orangutans. However, the vestibular morphologies reconstructed for the last common ancestors of dryopiths, crown hominines, and crown hominids are very similar, indicating that hominines are plesiomorphic in this regard. Therefore, our results do not conclusively favor a hominine or stem hominid status for the investigated dryopiths.

Size and shape of the semicircular canal of the inner ear: A new marker of pig domestication?

“…The bony labyrinth morphology has been proven to be a very efficient marker for the reconstruction of mammal phylogeny (e.g., Mennecart et al 2016Mennecart et al , 2017Urciuoli et al, 2021). Though based on only two geographically close wild boar populations and a limited number of domestic pigs (especially for the intensively bred category), extant wild boar and domestic pigs differ in their semicircular canal size and shape.…”

Shape analysis of the StW 578 calotte from Jacovec Cavern, Gauteng (South Africa)

“…We compared StW 578 to extant specimens and Sts 5 by using landmarkfree registration based on smooth and invertible surface deformation. [26][27][28][29][30] This approach has been previously applied to a number of craniodental and postcranial structures, including endocasts 27,29 , enamel-dentine junctions 28,31 , vertebrae 32 and bony labyrinths 33 and comparisons between the landmark-based and landmark-free approaches have revealed the ability of the latter approach for capturing geometric details and for statistical determination of geometric correspondence 34 . Because the StW 578 calotte is partial, instead of using the whole surface to align specimens as in previous studies [27][28][29] , we used four landmarks, i.e.…”

Total evidence tip-dating phylogeny of platyrrhine primates and 27 well-justified fossil calibrations for primate divergences

“…In a situation equivalent to that seen in cercopithecoids (see "Crown Cercopithecidae"), the early Miocene African fossil record of Hominoidea is characterized by a diversity of stem taxa (proconsuline and nyanzapithecine "proconsulids") without any evidence of crown representatives (Harrison, 2010b;Stevens et al, 2013;Nengo et al, 2017;Almécija et al, 2021).…”

“…A number of "dryopiths" (sensu Almécija et al, 2021;Urciuoli et al, 2021) from Europe, including the ~9.6-8.7 Ma old Ouranopithecus macedoniensis (Sen et al, 2000;Koufos et al, 2016), have been found to be stem hominines in some published phylogenetic analyses (e.g., Begun et al, 2012), but not others (e.g., Alba et al, 2015, and their position appears sensitive to analytical assumptions (Young and MacLatchy, 2004;Worthington, 2012). Given the ongoing controversy regarding the affinities of the European "dryopiths" (see Benoit and Thackeray, 2017;Fuss et al, 2018;Almécija et al, 2021), we follow Gilbert et al (2020) in viewing them as Hominoidea incertae sedis, and do not use them as the oldest record of Homininae. Instead, we use the slightly younger Chororapithecus abyssinicus, which we recognize as a crown hominine (stem gorillin), with an age range of 8.33-7.5 Ma (see "Crown Homininae" below).…”