Dryopithecine palaeobiodiversity in the Iberian Miocene revisited on the basis of molar endostructural morphology

Abstract

Extensive fieldwork at Abocador de Can Mata (north‐east Iberian Peninsula) has uncovered a previously unsuspected diversity of catarrhine primates in the middle Miocene (12.5–11.6 Ma) of Europe. However, the distinction of the great ape genera Pierolapithecus and Anoiapithecus from Dryopithecus (supported by craniodental differences) has been disputed by some authors. Here we revisit the diversity of great apes (dryopithecines) from the Iberian Miocene based on molar 3D endostructural morphology (relative enamel thickness, enamel distribution, and enamel–dentine junction (EDJ)). Using microtomography, we inspected an extensive sample of 49 hominoid molars representing at least five species from 12 localities. 2D and 3D relative enamel thickness values indicate that Dryopithecus and ‘Sivapithecus’ occidentalis (species inquirenda) display the thinnest and thickest enamel, respectively, while the remaining taxa (Hispanopithecus, Anoiapithecus, Pierolapithecus) show intermediate values. Upper molar enamel distribution maps exhibit a similar pattern in P. catalaunicus, A. brevirostris, D. fontani, H. laietanus and H. crusafonti whereas for the lower molars they reveal differences between H. laietanus and H. crusafonti. Lower molar enamel distribution and EDJ morphology of ‘S.’ occidentalis support the distinction of this species but do not resolve whether it is a junior synonym of Anoiapithecus brevirostris or Pierolapithecus catalaunicus. Overall our results support the distinction of middle Miocene dryopithecins from late Miocene hispanopithecins, the distinction of Pierolapithecus and Anoiapithecus from Dryopithecus among the former, and the distinct species status of H. crusafonti compared to H. laietanus among the latter. Our results highlight the potential of inner tooth morphology for hominoid alpha‐taxonomy.

The reconstructed cranium of Pierolapithecus and the evolution of the great ape face

“…Dentally, Pierolapithecus also retains a number of features that have been inferred to be primitive for hominids, including a prominent lingual pillar on the upper central incisors ( 20 ). Other features, such as molar enamel thickness, have been somewhat useful for taxonomic assessments but are more difficult to interpret in a higher-level phylogenetic context ( 21 ).…”

“…The distinctiveness of Pierolapithecus from other ACM hominoids has been questioned, in part due to the distortion of known cranial specimens and the close temporal and spatial proximity of the fossils ( 13 , 22 , 23 ). However, a number of cranial and dental features have been used to differentiate Anoiapithecus , Dryopithecus , and Pierolapithecus from each other ( 2 , 3 , 18 – 21 , 36 , 53 , 54 and SI Appendix, Extended Discussion ) and, based on our results, Pierolapithecus and Anoiapithecus can also be distinguished from Dryopithecus in the superoinferior position of the orbits relative to the nasal aperture, the degree of midfacial prognathism, the breath of the nasal aperture, and (face) size ( SI Appendix, Extended Discussion ). Despite these noted differences, Pierolapithecus and Anoiapithecus are very close to each other (and to most other hominids) in the shape spaces derived from PCA analyses, perhaps reflecting their overall hominid-like morphology.…”

“…In addition to the debate about how European hominoids are related to extant hominoids, the relationships among them are poorly understood ( 17 ) and there are ongoing debates about their taxonomy. The hominoids from ACM have been distinguished from one another primarily on the basis of craniofacial morphology ( 2 , 3 ), although differences in dental morphology between both Pierolapithecus and Anoiapithecus compared to Dryopithecus have also been noted ( 3 , 18 – 21 ). However, the close stratigraphic and geographic proximity of the ACM hominoid fossils, in combination with other factors, has led some authors to question their distinctiveness (e.g., refs.…”