The World at the Time of Messel

Primates in the

PHILIP D. GINGERICH1

1Department of Geological Sciences and Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109-1079 USA, [email protected].

The Eocene, like many epochs, started in crisis. primitive characteristics of Steinius vespertinus, there The first evidence of the crisis came in Wyoming with remains only one distinctive dental trait separating discovery of a distinct basal-Wasatchian Wa-0 basal omomyids from primitive adapids: a one-rooted (vs. two-rooted) P2. mammalian fauna that included some seemingly dwarfed species of lineages present before and after Given their similarity in space, time, and form, it is (Gingerich, 1989). The best-documented lineage with natural to group Tarsioidea and Adapoidea together dwarfing is that of Ectocion, where E. osbornianus as sister taxa and difficult to imagine that they are was replaced briefly by E. parvus. Stable isotope anything but closely related. Both superfamilies were studies later linked the dwarfing of Ectocion in forged in the PETM and seemingly cast from the Wyoming to the extinction of benthic foraminifera in same mold. the world’s oceans, and tied both to a global green- From this very similar beginning, Tarsioidea and house warming event now known as the Paleocene- Adapoidea diversified through the Eocene on all three Eocene thermal maximum or PETM (Kennett and northern continents. Tarsioidea and Adapoidea are Stott, 1991; Koch et al., 1992; Clyde and Gingerich, known from the Eocene of Africa as well 1998; reviewed in Gingerich, 2006). The Wa-0 crisis (Hartenberger and Marandat, 1992; Pickford et al., fauna includes the first representatives of the 2008; Seiffert et al., 2009; Jaeger et al., 2010), important mammalian orders Artiodactyla, Perisso- which may be their center of origin. By the late Eo- dactyla, and modern (‘Euprimates’) to be cene, the oldest anthropoids, Parapithecoidea, are found in . Two Wa-0 primates are known from Africa (Bonis et al., 1988; Seiffert et al., known: Cantius torresi Gingerich, 1986 and 2005; Jaeger et al., 2010). Africa is the logical place brandti Gingerich, 1993. to search for the origin of anthropoid or higher pri- Teilhardina and Cantius represent different super- mates, but the Eocene fossil record there is still families of primates, Tarsioidea and Adapoidea, inadequately studied. respectively, that have never been found in older Eocene primates are best known from the north- Paleocene strata but were seemingly cosmopolitan ern continents, where they are represented by some- from very early in the Eocene (Gingerich, 1986; Smith thing on the order of a hundred thousand specimens. et al., 2006). Early tarsioids and adapoids have the Most are isolated teeth or teeth in jaws, but there are same dental formula, 2.1.4.3 / 2.1.4.3, and similar also crania and partial skeletons. The advantage of upper and lower cheek teeth. They are generally having Eocene primates by the thousands is that in distinguished by size and by the relative length of the favorable stratigraphic settings large numbers of premolars. Tarsioids are smaller, generally below 500 specimens enable lineages to be traced through long g in estimated body weight, and adapoids are larger, intervals of time. Fossils, even fragmentary fossils, generally above 500 g in estimated body weight. are important for understanding geographic distribu- Premolars in tarsioids are short anteroposteriorly and tions, ecological associations, and environmental compact, while those of adapoids are more elongated constraints. anteroposteriorly. However, premolars of Cantius The advantage of crania and partial skeletons is torresi are similar to those of early omomyid tarsioids that they provide more information about the (Gingerich, 1986). as a whole, which is necessary to constrain hypothe- Rose and Bown (1991, p. 101) developed this ses of relationship to living primates. This is where theme, writing of early adapoids and omomyid tarsioids: Messel specimens are so important. Europolemur and are each known from exceptional Although adapids and omomyids have generally been placed in separate higher taxa of primates (e.g., specimens preserving crania and articulated post- suborders), the earliest members of each group are in cranial elements, sometimes in association (e.g., fact very similar both dentally and postcranially— Koenigswald, 1979; Franzen, 1987; Franzen et al., sufficiently so that diagnoses of these two families have 2009). Darwinius is particularly interesting in being been chronically vague, and confusion has surrounded so complete. Integrating Darwinius into a phylogeny the proper family assignment of such taxa as of living primates indicates that it groups with higher Donrussellia (D. gallica, the type species of primates (Gingerich et al., 2010). Donrussellia, was initially allocated questionably to Putting all of this together (Fig. 1), we have a phy- Teilhardina). As our knowledge of the earliest eupri- logeny of higher primates, or Anthropoidea, including mates has improved, the number of characters distinguishing adapids and omomyids has steadily the superfamilies Ceboidea, Cercopithecoidea, and declined, making separation of from Hominoidea. Anthropoidea originated and diversified Adapidae exceedingly difficult on dental characters sometime near the end of the Eocene. Combining alone (dentitions constitute by far the principal fossil Anthropoidea with Adapoidea and Tarsioidea, we remains for most early euprimates). In view of the have a more inclusive group, , that origi

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Figure 1. Phylogram showing the relationships of Eocene Tarsioidea (including Eosimias) and Adapoidea (including Darwinius), in the shaded box, to more primitive (Lemuroidea and Lorisoidea) and more derived Anthropoidea (Ceboidea, Cercopithecoidea, and Hominoidea). Analysis follows Gingerich et al. (2010).

nated and diversified sometime near the beginning of Strepsirrhini, including Lemuroidea and Lorisoidea, the Eocene. The Eocene can be viewed as the age of has a deeper root and, by inference, may go back to Tarsioidea and Adapoidea. Darwinius is an adapoid the early part of the Paleocene (no Paleocene and phylogenetically also a stem anthropoid. The strepsirrhines are known). designation ‘stem anthropoid’ is misleading for Darwinius, as it is for most stem taxa, because it has ACKNOWLEDGMENTS none of the characteristics that would make it a true My research on Messel fossils has been supported by anthropoid. The sister group to Haplorhini, the Alexander von Humboldt Stiftung.

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