South American primates – technically known as platyrrhine primates, in reference to their broad, flat nose – are an interesting lot. They include the only monkeys with prehensile tails (charismatic types such as capuchins, spider, and howler monkeys), the only nocturnal monkeys (owl monkeys of the genus Aotus), and they tend to be both smaller and less terrestrial than their Old World counterparts, the catarrhines (Rosenberger and Hartwig 2012). But as is true for many groups of living mammals, the past diversity of platyrrhines is greater than that of modern species, at least in certain respects. Most conspicuously, a mere tens of thousands of years ago (perhaps less), three species of monkeys were living in Brazil that were all much larger than any species alive today.

Before delving into these platyrrhines of unusual size, I must acknowledge the important role played by Peter Wilhelm Lund in these discoveries. Lund was a physician-turned-naturalist from Denmark who labored for a decade in the mid 1800s excavating Pleistocene fossils in limestone caves in the region of Lagoa Santa in southeastern Brazil (Minas Gerais state). Lund amassed an important collection of some 12,000 fossil specimens that now resides at Denmark’s Royal Natural History Museum at the University of Copenhagen (Fariña et al. 2012). Among the most important of these specimens are a handful of bones of a large monkey that Lund named Protopithecus brasiliensis in 1837. The great size of these bones is what alerted Lund to their distinctiveness, and his realization that they pertained to an extinct species was remarkable for the time. Up until the 1830s, no extinct primate had ever been recognized in the fossil record. In an amazing case of coincidence, similar discoveries of extinct primates in both Europe and Asia slightly predated Lund’s discovery in Brazil and mostly eclipsed Lund’s discovery, but Protopithecus brasiliensis was the first of these new species to be formally named (Hartwig 1995).

Despite the importance of Lund’s discovery, it languished in near-obscurity for more than 150 years until a second specimen was discovered and referred to the same species. In contrast to Lund’s original find, the new specimen was found in a cave system called Toca da Boa Vista located some 1,200 km (nearly 750 miles) to the northeast in the state of Bahia. Additionally, the specimen was essentially complete and included a well-preserved skull. The describers of this new specimen estimated its body mass at roughly 25 kg (55 lbs) – more than double the size of the largest living platyrrhines, muriquis (Brachyteles spp.) – and noted that its skeleton displayed a mixture of traits seen in monkeys of the family Atelidae; the skull resembled that of a howler monkey (Alouatta spp.), but its limbs were more similar to those of spider and woolly monkeys, members of the subfamily Atelinae (Hartwig and Cartelle 1995). These authors ended up placing Protopithecus in the spider monkey subfamily (Atelinae), but were uncertain whether the features it shared with spider monkey reflected a close evolutionary relationship or simply convergent evolution.

The following year, the same pair of researchers described another large-bodied monkey from the same cave system in Bahia: Caipora bambuiorum. Caipora was about the same size as Protopithecus – tipping the scales at more than 20 kg – but its skull resembled that of modern spider monkeys (Ateles spp.), clearly differentiating it from Protopithecus (Cartelle and Hartwig 1996). The generic name Caipora was particularly well-chosen, as it alludes to a mythical Brazilian animal known as the Cayporé that is described as a large, ape-like creature of the forest. This legendary creature could have a basis in fact if it represents sightings of Caipora, Protopithecus, or another extinct Pleistocene primate that were passed down orally through many generations (Blake 1862); early colonizers of South America undoubtedly crossed paths with these and other extinct megafauna of the late Pleistocene (much to the chagrin of said megafauna). It is also possible that the legend originated much more recently with African slaves who brought memories of gorillas and other extant African apes with them to Brazil in the 17th century. I suppose a third possibility it that someone just made it up at some point.

The juxtaposition of the two publications describing these monkey skeletons was no mere coincidence; rather, the coincidence was the discovery of the specimens themselves. Primates are rare in the fossil record, especially in South America. Finding a fossil monkey makes a great field season. Finding a nearly complete monkey makes a season extraordinary. Finding two nearly complete monkeys? Unheard of – at least until Cartelle and coworkers did just that in December of 1992. I will be stunned if the same thing happens again in my lifetime. The presence of two portly Pleistocene platyrrhines in Brazil led its describers to conclude that this group of mammals demonstrated a late Pleistocene increase in body size in parallel to that seen in many other groups of mammals at the same time (Cartelle and Hartwig 1996). That seems to be a reasonable interpretation, but it is difficult to critically evaluate based on the scarcity of the platyrrhine fossil record; it is possible that monkeys reached similar sizes much earlier in their evolutionary history.

Although no new specimens of Protopithecus or Caipora have been found since the early 1990s, the story of giant South American monkeys changed a few years ago when other researchers restudied Lund’s original specimen of Protopithecus from Lagoa Santa as well as the partial skeleton referred to it from Toca da Boa Vista. They judged that the differences between the two were too great to be accommodated by a single species. As result, they coined a new name – Cartelles coimbrafilhoi – for the skeleton. They also shifted the classification of this specimen from the spider monkey subfamily (Atelinae) to the howler monkey one (Alouattinae). Despite the excellent remains that exist for both Caipora and Cartelles, neither of these species has ever been included in a phylogenetic analysis, so all such classifications should be taken with a grain of salt.

Other than Protopithecus, Caipora, and Cartelles, fossils of Pleistocene monkeys are virtually unknown in continental South America. However, a variety of remains have been collected from islands of the Caribbean. As mentioned in my Nesophontes post, these monkeys probably made their way to Cuba and other islands the same way monkeys made it to continental South America in the first place: chance over-water dispersal (as alluded to in the name of this blog). Unfortunately, all of these island primates went extinct within the past few thousand years, probably due in large part to the arrival of humans (MacPhee 2009). Whether or not the same explanation accounts for the extinction of Protopithecus, Caipora, and Cartelles in Brazil is an open question. Although it will never be possible to answer that question with certainty, the fact remains that human encroachment on Neotropical forest ecosystems has placed the futures of many extant platyrrhines in peril. It is our responsibility to do all we can to prevent these monkeys from slipping from the realm of biology into the realm of paleontology.

References Cited:

• Blake, C. C. 1862. Past life in South America. The Geologist 5:323-330.
• Cartelle, C., and W. C. Hartwig. 1996. A new extinct primate among the Pleistocene megafauna of Bahia, Brazil. Proceedings of the National Academy of Sciences 93:6405-6409.
• Fariña, R. A., S. F. Vizcaíno, and G. De Iuliis. 2012. Megafauna: Giant Beasts of Pleistocene South America. Indiana University Press, Bloomington.
• Halenar, L. B. 2012. Paleobiology of Protopithecus brasiliensis, a plus-size Pleistocene platyrrhine from Brazil. Ph.D. dissertation, Graduate Faculty in Anthropology, City University of New York, 240 pp.
• Halenar, L. B., and A. L. Rosenberger. 2013. A closer look at the “Protopithecus” fossil assemblages: new genus and species from Bahia, Brazil. Journal of Human Evolution 65:374-390.
• Hartwig, W. C. 1995. Protopithecus: rediscovering the first fossil primate. History and Philosophy of the Life Sciences 17:447-460.
• Hartwig, W. C., and C. Cartelle. 1996. A complete skeleton of the giant South American primate Protopithecus. Nature 381:307-311.
• MacPhee, R. D. E. 2009. Insulae infortunatae: establishing a chronology for late Quaternary mammal extinctions in the West Indies; pp. 169-193 in G. Haynes (ed.), American Megafaunal Extinctions at the End of the Pleistocene. Springer, New York.
• Rosenberger, A. L., and W. C. Hartwig. 2012. New World Monkeys. In: eLS. John Wiley & Sons. Ltd., Chichester.