Updated chronology for the Miocene hominoid radiation in Western Eurasia

Abstract

Extant apes (Primates: Hominoidea) are the relics of a group that was much more diverse in the past. They originated in Africa around the Oligocene/Miocene boundary, but by the beginning of the Middle Miocene they expanded their range into Eurasia, where they experienced a far-reaching evolutionary radiation. A Eurasian origin of the great ape and human clade (Hominidae) has been favored by several authors, but the assessment of this hypothesis has been hampered by the lack of accurate datings for many Western Eurasian hominoids. Here we provide an updated chronology that incorporates recently discovered Iberian taxa and further reevaluates the age of many previously known sites on the basis of local biostratigraphic scales and magnetostratigraphic data. Our results show that identifiable Eurasian kenyapithecins (Griphopithecus and Kenyapithecus) are much younger than previously thought (ca. 14 Ma instead of 16 Ma), which casts serious doubts on the attribution of the hominoid tooth from Engelswies (16.3–16.5 Ma) to cf. Griphopithecus. This evidence is further consistent with an alternative scenario, according to which the Eurasian pongines and African hominines might have independently evolved in their respective continents from similar kenyapithecin ancestors, resulting from an early Middle Miocene intercontinental range extension followed by vicariance. This hypothesis, which would imply an independent origin of orthogrady in pongines and hominines, deserves further testing by accurately inferring the phylogenetic position of European dryopithecins, which might be stem pongines rather than stem hominines.

Inferring the phylogeny of both living and extinct taxa is essential for understanding the evolutionary history of any particular clade. In this regard, chronostratigraphic data are of utmost significance, not only for testing paleobiogeographic scenarios but even for testing phylogenetic hypotheses (1). Current evidence indicates that hominoids originated in Africa, where they experienced an impressive early radiation during the Early Miocene (2, 3). During the Middle and Late Miocene, however, hominoids are also known from Eurasia, where they are recorded by a plethora of new forms, coinciding with a likely decline in hominoid diversity recorded in Africa. This Eurasian radiation partly reflects the acquisition of diverging adaptative strategies along several lineages in response to new habitats and changing environmental conditions through time (4–6), although geographic isolation followed by vicariance probably also played a significant role (7–9). Our understanding of the Miocene hominoid radiation in Eurasia and its implications for the origin of the great ape and human clade has been seriously hampered by the lack of a robust chronostratigraphic background and accurate datings for many sites. Here we provide an updated chronology for the Miocene hominoid sites of Western Eurasia (Europe, Turkey, and Georgia) which incorporates Iberian sites where several new hominoid taxa have recently been described. Particular emphasis is placed on those localities for which controversial and uncertain ages have been previously reported, and their implications for hominoid evolution are further discussed.

Results and Discussion

Oldest Eurasian Hominoid?

A partial upper third molar from Engelswies (Bavarian Molasse Basin, Germany), previously tentatively attributed to Griphopithecus (a discussion of the taxonomy of Miocene Eurasian hominoids is provided in SI Appendix, Text 1), has been considered to be the oldest Eurasian hominoid (10) (Fig. 1). An age of ca. 17 Ma was favored for Engelswies on the basis of associated mammals and lithostratigraphic correlation with the main units of the Bavarian Molasse (10) (see SI Appendix, Text 2 for more details on the regional chronological systems units and Dataset S1 for additional data on the chronology of the Miocene hominoid sites of Western Eurasia). Preliminary magnetostratigraphic data (11) enabled a correlation of the short (less than 5 m) Engelswies section to longer magnetostratigraphic profiles of the Bavarian Molasse (12, 13), resulting in a correlation to geomagnetic polarity chron C5Cr (17.235–16.721 Ma) that confirmed previous age estimates. On biostratigraphic grounds, Engelswies can be correlated to the Keramidomys–Megacricetodon bavaricus Overlap zone of the Swiss Molasse, which ranges from 16.2 to 16.7 Ma (14). The Middle Miocene biozonations for the Swiss and the Bavarian Molasse are identical but for an age discrepancy (diachrony) regarding the boundaries of the different units, so that older ages are usually proposed based on the Bavarian Molasse succession (14). Such discrepancy is attributable to the fact that the Bavarian Molasse magnetostratigraphic sections record too few geomagnetic reversals, which precludes an unambiguous correlation to the geomagnetic polarity timescale (GPTS). Therefore, correlations for the Bavarian Molasse frequently rely on second- and even third-order lithostratigraphic correlations, together with the occurrence of radiometrically dated bentonites within the successions (12, 13). If the higher-resolution record of the Swiss Molasse is considered, the reversed magnetozone of the Engelswies section best correlates either to chron C5Cn.1r (16.303–16.268 Ma) or C5Cn.2r (16.543–16.472 Ma), that is, immediately before the Langhian. Hence, if the exact stratigraphic provenance of the hominoid teeth is accurately recorded (10), hominoids would have dispersed into Eurasia by the latest Early Miocene. This earliest occurrence is, however, very surprising, because it predates the other oldest Eurasian sites by at least 1.3–1.5 Myr (see below). Even more surprising is that hominoids have not been recorded from Sandelzhausen, a temporally equivalent locality from the Bavarian Molasse that after decades of excavation has delivered more than 50,000 identifiable specimens (15).

Fig. 1.

Early and Middle Miocene hominoid localities of Western Eurasia and their correlation to the geological timescale. Three different regional chronological systems are included (from left to right): for the Iberian Peninsula and France, for Central and Eastern Europe, and for Turkey. Preferred magnetostratigraphic correlations are indicated by solid blue lines and alternative correlations with dashed blue lines. The scale is the same for all of the magnetostratigraphic sections. Red bars indicate biostratigraphic correlations based on mammal faunas, the length of the bar referring to the uncertainty in this correlation. Correlations based in marine/freshwater stages are indicated with a green bar, and the length of this bar also refers to the uncertainty in the correlation. A question mark indicates a highly uncertain correlation because of lack of data. For additional details regarding the local/regional chronological systems used, see SI Appendix, Text 2; for more data on the age of a particular site, see Dataset S1.

Middle Miocene Sites.

After Engelswies, the oldest hominoid sites of Western Eurasia are Paşalar and Çandir in Turkey. Both record Griphopithecus alpani, and recently a second hominoid, Kenyapithecus kizili, was reported from Paşalar (16). On biostratigraphic grounds, Çandir can be correlated to either Mammal Neogene Zone 5(MN5) or MN6 (17, 18). Unfortunately, magnetostratigraphic results (19) do not allow an unambiguous correlation to the GPTS; three correlations are possible: C5ACn (14.095–13.734 Ma), C5ABn (13.605–13.369 Ma), or C5Cn (16.721–15.974 Ma). Although the latter correlation requires assuming large sedimentary and/or tectonic hiatuses in the Çandir section, it has been favored by some (20). Based on biostratigraphy, Çandir was initially correlated to the MN6 (18) and subsequently to the MN5 (17). The presence of Megacricetodon collongensis argues against the former correlation, because this taxon is last recorded in the MN4 in Central Europe and in the MN5 in Spain. However, because the disappearance of this rodent appears to be highly diachronic, an alternative correlation to the MN6 and chron C5ACn or C5ABn, as favored by Krijgsman (19), is supported by the rest of the fauna, resulting in an estimated age of ca. 13.4–14.1 Ma. Regarding Paşalar, the correlation must entirely rely on biostratigraphy. The rodent fauna suggests a correlation to the MN6 (21) or to the equivalent Turkish Zone F (22). Therefore, as further suggested by the macrofauna (23), Paşalar would be close in age to Çandir, although slightly older. A hominoid tooth from the Lower Sinap Member (24) in Turkey might be somewhat older, although the exact situation of this ancient find is unknown. On the basis of the associated fauna, this find has been correlated to the locality of Inönü with an estimated age of ca. 15 Ma (25, 26) (Dataset S1). Be that as it may, this earliest occurrence is much younger than customarily assumed by most paleoprimatologists (4, 5, 20), and postdates by at least 1.3 Myr the earliest Eurasian occurrence of hominoids as documented by Engelswies.

Regarding the hominoid sites from Slovakia (Devínská Nóva Ves) and Austria (Klein Hadersdorf), they include several teeth and postcranials attributed to Griphopithecus suessi (=G. darwini; SI Appendix, Text 1). These localities occur in transitional facies that delivered a mixed assemblage of terrestrial vertebrates with both MN6 and MN7+8 elements (27). Planktonic foraminifera from the same facies allow a correlation to zones MMi9/MMi13 (28), whereas nannoplankton indicates an MNN6/MNN7 age (29), suggesting an age not older than 11.6 Ma. Similarly, the clay pit of St. Stefan im Lavanttal (Austria), the type locality of the nominal taxon Dryopithecus fontani carinthiacus (here considered a junior synonym of D. fontani), can be correlated to the Central Paratethys stages. The mollusk fauna from this site indicates a Late Sarmatian (Upper Ervilia Zone) age (30), which is congruent with the results provided by the rodent fauna indicating an MN7+8 age (31).

The densest Middle Miocene hominoid record occurs at the Vallès-Penedès Basin (Catalonia, Spain) (see SI Appendix, Text 3 for an updated synthesis of the biostratigraphy and magnetostratigraphy of the Vallès-Penedès record). Comprehensive fieldwork in the 250-m-thick Abocador de Can Mata (ACM) local stratigraphic series (els Hostalets de Pierola) has recently led to the description of two new genera and species, Pierolapithecus catalaunicus (32) and Anoiapithecus brevirostris (33), as well as to the recovery of new material of D. fontani (34) and some fragmentary hominoid remains yet to be described. High-resolution magnetostratigraphic studies at the ACM series allow an unambiguous correlation to the GPTS (34). The series spans from ca. 12.5 to 11.4 Ma and includes more than 150 mammal localities, enabling a detailed local biozonation. The oldest hominoid occurrence corresponds to locality ACM/C1-E*, with an estimated age of 12.2–12.3 Ma, whereas the youngest occurrence is a single tooth from Can Mata I (35), which would be close to 11.2–11.1 Ma. The remaining ACM hominoid sites cluster in a tight interval of less than 0.2 Myr (11.8–11.9 Ma). The holotype of “Sivapithecus” occidentalis (nomen dubium) has an uncertain stratigraphic provenance, so that an estimated age spanning the whole ACM series (12.5–11.4 Ma) cannot be further specified.

On biostratigraphic grounds, other hominoid sites from the Vallès-Penedès Basin can be correlated to the ACM series. Thus, Castell de Barberà and Sant Quirze correspond to the Democricetodon crusafonti + Megacricetodon ibericus Concurrent range zone and would be somewhat younger than most of the ACM hominoid sites. This local biozonation can also be recognized in France, which allows refining the age of some ancient localities, including the fissure fillings from La Grive-Saint-Alban (Dataset S1 and SI Appendix, Text 3). D. fontani has been reported from La Grive fissures M and L3 (or L5) (Dataset S1). La Grive M is correlated to the Vallès-Penedès D. larteti + M. ibericus Concurrent range zone (ca. 12.4–11.8 Ma), whereas La Grive L3 and L5 sites are correlated to the D. crusafonti + M. ibericus Concurrent range zone (11.8–11.2 Ma). Finally, the karstic site of Saint Gaudens, the type locality of Dryopithecus fontani, has delivered a poor macromammal assemblage that merely suggests an MN7+8 correlation (ca. 12.5–11.1 Ma), not allowing further accuracy.

Late Miocene Sites.

During the early Vallesian (earliest Late Miocene), hominoids are still diverse and widespread across Western Eurasia. In the Iberian Peninsula, most hominoids occur in the Vallès-Penedès Basin, where they are represented by Hispanopithecus laietanus and H. crusafonti. This genus occurs at several early Vallesian sites (i.e., Can Poncic, Can Llobateres 1) but becomes rarer during the late Vallesian, being last recorded at La Tarumba 1. The range of Hispanopithecus in the Vallès-Penedès Basin can be constrained between 11.1 and 9.5 Ma, thanks to the detailed bio- and magnetostratigraphic data available for most of the sites (Fig. 2) (SI Appendix, Text 3). Regarding the mandible of cf. H. crusafonti from Teuleria del Firal (36, 37), in the small intra-Pyrenean Seu d'Urgell Basin, such detailed information is not available. This locality delivered a macromammal assemblage that includes Hippotherium primigenium, indicating a Vallesian age. The location of this site in the lithostratigraphic unit of Bellestar enables further refinement of this age, on the basis of two micromammal sites (38) from the same unit. These localities can be correlated to the Cricetulodon hartenbergeri Local range zone of the Vallès-Penedès, indicating an age close to that of Can Poncic (10.4–9.9 Ma), which is the type locality of H. crusafonti.

Fig. 2.

Late Miocene hominoid localities of Western Eurasia and their correlation to the geological timescale. For the regional chronological systems used and conventional symbols, see Fig. 1. For the Italian sites, the red line refers to a radiometrically dated tuff layer within the Baccinello succession (see text for details). For additional details regarding the local/regional chronological systems used, see SI Appendix, Text 2; for more data on the age of a particular site, see Dataset S1.

In Germany, isolated hominoid molars have been recovered from a series of fissure fillings and from Wissberg and Eppelsheim. These sites are located within the well-known Dinotheriensande Formation, which ranges from the early Vallesian to the early Turolian, and consists of an alternation of conglomerates and sands of fluvial origin. Part of the assemblage may be reworked, because some fossils show signs of abrasion (39). The fauna associated to the as yet undescribed material from Eppelsheim (40) clearly points to an early Vallesian age (MN9). On the other hand, the fauna from Wissberg is a mixture of predominantly Vallesian elements with Astaracian (Prodeinotherium bavaricum, Anchitherium aurelianense) and Turolian ones (cf. Mesopithecus pentelicus). Regarding the karstic sites, Salmendingen, the type locality of Neopithecus brancoi (nomen dubium), deserves special attention. The poor fauna from Salmendingen includes a few taxa that may indicate a Vallesian age as well as the beaver Dipoides, which dispersed into Europe from North America during the early Turolian (MN11) (41). Hence, Salmendingen has been assigned to either the MN9/MN10 (37) or the MN11 (27), and it is likely that the fauna represents a mixture of Vallesian and Turolian elements, as it is frequent in karstic sites. The same situation may apply to Melchingen, which apparently mixes Vallesian and Turolian elements, including Dipoides. The remaining German karstic sites, Ebingen and Trochtelfingen, have not delivered additional material to the few primate teeth, so nothing can be said about their age.

The chronology of Götzendorf and Mariathal, in the Vienna Basin (Austria), is more firmly established because they are located in fluvial and lacustrine sediments related to Lake Pannon. The successions of the Vienna Basin have been intensively studied and a highly detailed biostratigraphy based on molluskan faunas is available (42). On this basis, Götzendorf can be correlated to the late Pannonian Zone F2 (i.e., latest early Vallesian) (43). Mariathal is correlated to the early to middle Pannonian age (zones C or D) (44), indicating a slightly older Vallesian age. All these finds are very fragmentary and contrast with the much more complete material recovered from Rudabánya (Hungary) attributed to Hispanopithecus hungaricus. This site, located within lacustrine sediments of Lake Pannon, delivered an extremely rich fossil assemblage that suggests an MN9 age (45). Nevertheless, the occurrence of Hippotherium intrans, a derived member of the Hippotherium primigenium lineage, may indicate an age of 10.0–9.8 Ma, closer to the early/late Vallesian boundary (46).

During the Vallesian, two additional distinct hominoid genera are recorded in the Eastern Mediterranean: Ankarapithecus in Turkey and Ouranopithecus in Greece. The former is known from the densely sampled Sinap Formation, and its age is well-constrained by the means of bio-, litho-, and magnetostratigraphy (25, 26). The specimens, including postcranial and cranial remains, have been recovered from the similarly aged localities 8A and 12. Locality 8A is correlated to chron C5n.1r (9.987–9.934 Ma), whereas locality 12 can be correlated either to chron C5n.1n (9.934–9.779 Ma) or to C4Ar.2n (9.717–9.656 Ma) (26). Therefore, the age of the specimens would lie close to the early/late Vallesian boundary, being very close in time (if not synchronous) to the specimens of Can Llobateres 1 (9.7 Ma) and/or Rudabánya (10.0–9.8 Ma). On the other hand, O. macedoniensis is recorded from Nikiti 1, Xirochori 1, and Ravin de la Pluie. All these Greek localities have delivered a rich mammal assemblage, which at Ravin de la Pluie includes both micro- and macromammals that clearly indicate a late Vallesian (MN10) age (47). Typical MN10 large mammal faunas also occur at Xirochori 1 and Nikiti 1. However, at Nikiti 1, a few early Turolian (MN11) taxa are recorded (Oioceros, Helladotherium) which suggest a slightly younger age (47). The magnetostratigraphic survey of the Late Miocene mammal succession of the Lower Axios Valley (48) has allowed further refining the age of these sites, even though the studied sections are too short to provide an independent correlation to the GPTS. Ravin de la Pluie is correlated to chron C4Ar.1n (9.409–9.312 Ma), and the somewhat older site of Xirochori 1 is correlated to chron C4Ar.2n (9.717–9.656 Ma). Nikiti 1 is supposed to be slightly younger than Xirochori 1 but still late Vallesian (MN10) in age (47), like the other localities.

Latest Hominoids from Western Eurasia.

Hominoids are last recorded from the Vallès-Penedès Basin at 9.5 Ma, whereas their youngest unambiguous record from Central Europe is that of Rudabánya ca. 10.0–9.8 Ma. Nevertheless, they clearly persist longer in the Eastern Mediterranean, so that many Late Miocene hominoid sites of that area have been assigned to the Turolian, even though available data do not always support such age. These latest hominoid occurrences comprise that of Graecopithecus freybergi (nomen vanum) from Pyrgos Vassilissis in Greece. The mammal fauna from this site is too fragmentary to reach sound chronological conclusions (47), although several taxa (Tragoportax amalthea, Gazella deperdita) indicate a Turolian age (MN11-MN12; i.e., 8.7–6.8 Ma).

A maxillary fragment attributed to ?Udabnopithecus garedziensis, from the Shiraki Formation close to Udabno (Georgia), has also been assigned to the Turolian (49). The Shiraki Formation is a 300-m-thick clay succession with two mammal localities (Udabno 1 and 2). The primate remains were found 40 m above Udabno 1 (49), which yielded a rich mammal assemblage indicating a late Vallesian (MN10) age. Udabno 1 yielded a normal polarity that is correlated to chron C4An (9.098–8.769 Ma) (50). Therefore, ?Udabnopithecus would be a late Vallesian taxon roughly contemporaneous to Ouranopithecus macedoniensis, although maybe slightly older.

Furthermore, another species of Ouranopithecus, O. turkae, has been described from Çorakyerler in Turkey (51). This site delivered a rich assemblage including small and large mammals. The rodent fauna is dominated by the murid Hansdebruijnia, exclusively known from this site (52), but further includes two species of Byzantinia and a species of Pseudomeriones. These elements suggest a correlation to the Turkish zones J or K (MN9–MN12) (22), although a tentative correlation to the MN11 (8.7–7.9/7.5 Ma) has been favored (52). The macromammal fauna also suggests an MN11 age, although certain ruminants (Pliocervus sp., Miotragocerus valenciennesi, Oioceros rothi) would alternatively favor an MN12 age (7.9/7.5–6.8 Ma). On this basis, a somewhat younger age (MN12) cannot be discarded for O. turkae. Regarding the hominoid dental material from the Ahmatovska Formation in Bulgaria (53), although additional faunal data would be required, a Turolian age (8.7–4.9 Ma) is suggested by the presence of Protragelaphus and Anancus.

Finally, the latest Western Eurasian hominoid is Oreopithecus, which evolved under insularity conditions in the Tusco-Sardinian paleobioprovince during the Late Miocene (54). The dating of the so-called Oreopithecus faunas has always been problematic because of their endemism. The Baccinello-Cinigiano Basin succession from Tuscany has been divided into four different biochronological units, V-0 to V-3 (55). Unlike V-1 and V-2, the V-0 and V-3 faunas are not completely endemic and can be correlated to the MN11 and MN13, respectively (55). Therefore, the Oreopithecus faunas were short-lived, spanning from about 8.5/8 Ma to 7/6.5 Ma. This fully agrees with a radiometric dating of 7.5 ± 0.03 Ma for a volcanic layer within the Baccinello succession (56). Thus, Oreopithecus was contemporary with other Turolian hominoids from the Eastern Mediterranean, but may have survived until slightly later, probably becoming extinct when the Tusco-Sardinian archipelago became connected to the mainland at ca. 7 Ma (57).

Conclusions

If the stratigraphic provenance of the Engelswies tooth is correctly recorded, hominoids must have first dispersed into Eurasia shortly before the Langhian transgression (Fig. 3), that is, before 16.3 Ma. The partial molar from this locality, however, offers very limited morphologic information, other than indicating an attribution to a thick-enameled undetermined hominoid. The previous assignment of this tooth to cf. Griphopithecus (10) was largely based on similarly old previous age estimates for the Turkish localities where this taxon has been securely recorded. Here we show that, on the contrary, these localities are much younger (ca. 14 Ma). This considerable temporal gap therefore casts serious doubts on the attribution of the Engelswies hominoid to Griphopithecus, so that a phylogenetic link with kenyapithecins remains to be established. On the basis of currently available evidence, it can only be confidently concluded that, after the Langhian transgression, a group of hominoids of African origin, the pronograde kenyapithecins (2, 3, 5, 58, 59), extended their geographic range into Eurasia, being first recorded in Turkey by both Griphopithecus (Eurasia) and Kenyapithecus (Eurasia and Africa). The retention of kenyapithecin features in the late Middle Miocene Iberian dryopithecins (33) at ca. 12 Ma suggests that the Eurasian hominoid radiation might have originated from some kenyapithecin ancestor, but it remains to be ascertained whether this radiation gave origin exclusively to extant pongines or to both pongines and hominines.

Fig. 3.

Range chart for Miocene hominoids of Western Eurasia. For details on the taxonomy, see SI Appendix, Text 1; for details on the age of particular sites, see SI Appendix, Text 2 and Dataset S1.

During the last decade, some authors have favored a Eurasian origin of the great ape and human clade (Hominidae) followed by a later back-into-Africa dispersal of the Homininae (4, 9, 37, 60). This biogeographic scenario is dismissed by the recent description of putative hominines from the African Late Miocene (61, 62), as well as by phylogenetic uncertainties surrounding Hispanopithecus and Ouranopithecus, interpreted either as hominines (2, 37, 60, 63) or as pongines (64–66). Deciphering the phylogenetic status of Middle Miocene European dryopithecins, previously considered stem hominids (32–34), is of much higher significance for testing this scenario, because undoubted pongines are almost simultaneously recorded in Asia ca. 12.5 Ma (67). This is consistent with an initial far-reaching range extension of kenyapithecins throughout Eurasia between 14 and 12.5 Ma, followed by vicariance processes giving rise to pongins in Eastern Eurasia and dryopithecins in Western Eurasia. If correct, this would indicate an independent evolution of pongines (including dryopithecins) and hominines in their respective continents from similar pronograde kenyapithecin ancestors, that is, that orthogrady is homoplastic among crown hominids.

Such a high degree of homoplasy is not as unlikely as it might seem at first sight (68–70), particularly given global paleoenvironmental changes that could have prompted similar adaptive responses in both groups. In particular, the climatic deterioration initiated at 14 Ma (71) apparently acted as a trigger of the hominoid Eurasian radiation, as reflected by the wide geographic range, and increased taxonomic and ecological diversity shown by hominoids until the early Vallesian. After the late Vallesian (ca. 9.5 Ma), however, hominoids are no longer recorded in Western and Central Europe—with the exception of Oreopithecus, which survived until ca. 7 Ma on its insular refuge. This probably reflects a true regional extinction event (the so-called Vallesian Crisis) (72–74), resulting from the crossing of some paleoenvironmental threshold that hominoids were unable to manage. Only in the Eastern Mediterranean did hominoids survive somewhat longer (until ca. 8.0–7.5 Ma), probably thanks to the preexisting adaptations of ouranopithecins to the environmental conditions of the Greco-Iranian biome. Ultimately, however, the paleoenvironmental changes associated with increased aridification and seasonality (75, 76) completely wiped out hominoids from Western Eurasia during the Turolian, further leading to their progressive diversity decline and geographic range restriction in Asia throughout the Plio-Pleistocene (77, 78). This heavily contrasts with the evolutionary response of hominoids to climatic change in Africa where, coinciding with the extinction of European hominoids, purportedly bipedal hominins are already recorded during the Late Miocene [ca. 7–6 Ma by Sahelanthropus and Orrorin (79, 80)] and during the latest Miocene (5.8–5.2 Ma) and earliest Pliocene (4.4 Ma) by Ardipithecus (81, 82).

Materials and Methods

Chronological Framework: Regional Timescales and Correlation.

For decades, the chronology of European Neogene sites has relied extensively on the use of MN zones. This biochronological system, introduced during the 1970s (83), takes into account the first and last appearances of selected taxa as well as the characteristic association of taxa within a particular unit. Furthermore, a reference fauna is attached to each unit. The system was immediately accepted and applied to all European regions, and even to Asia and Africa. Since then, MN zones have gone through successive reviews and updates and, at the same time, have witnessed the development of more refined regional biochronological and biostratigraphic scales. Recently, the system has been criticized because its accuracy and applicability across Europe is strongly affected by the provinciality of the faunas and the diachrony of first and last appearances (84, 85). Furthermore, the diachrony of important faunal events has been clearly shown (85), implying discrepancies in MN-zone boundaries sometimes exceeding 1 Myr. In the present work, we favor the use of regional chronological scales together with the correlation of magnetostratigraphic sections to the GPTS (86) (SI Appendix, Text 2). As such, we have only relied on the MN-zone system for rough, long-distance correlations when other relevant data are not available. In these cases, a certain error margin that can be of ±0.5–1.0 Myr has to be assumed.