Marcelo F. Tejedor

Platyrrhine Ecophylogenetics in Space and Time

We are far from developing an informed synthesis regarding the evolution of New World Monkeys – probably decades away. For even with the important strides made over the past 30–40 years regarding platyrrhine ecology and behavior, there are large gaps in our knowledge of the evolutionary and historical context. The scarceness of fossils is but one factor. Equally critical is our incomplete knowledge of largescale changes to the continent of South America (SAM), pertinent to the evolution of its fauna. An objective of this paper is to review some of this information as a basis for interpreting the platyrrhines from an ecophylogenetic point of view in space and time. Our goal is to integrate information on living and extinct forms in order to identify community or regional patterns of platyrrhine evolution, rather than examining the moderns and fossils as distinct entities or evolutionary problems. In keeping with the South American emphasis of this volume, we do not consider the primate fauna of the Middle American mainland but have elected to examine the Caribbean subfossil monkeys for reasons that will become clear below. We suggest that the casual way of thinking about New World Monkeys (NWM) as a monolithic radiation inhabiting a rainforest wonderland – South America – is a model that needs to be changed. The continent is about 2.5 times the size of today’s Amazonian rainforest in area, it contains diverse landscapes and habitats, and the Amazonian region changed vastly during the Cenozoic (e.g., Bigarella and Ferreira 1985). At present, more of the continent is grassland than rainforest (Fig. 4.1a), and the grasslands have been flourishing for 20–30 million years (see below). The first primates to arrive did not encounter the Amazonia we know, for it may have begun to take on its present character only about 15 Ma (Campbell et al. 2006). Thus, even though the NWM have a monophyletic, unitary origin, their

Divergence Times and the Evolutionary Radiation of New World Monkeys (Platyrrhini, Primates): An Analysis of Fossil and Molecular Data

The estimation of phylogenetic relationships and divergence times among a group of organisms is a fundamental first step toward understanding its biological diversification. The time of the most recent or last common ancestor (LCA) of extant platyrrhines is one of the most controversial among scholars of primate evolution. Here we use two molecular based approaches to date the initial divergence of the platyrrhine clade, Bayesian estimations under a relaxed-clock model and substitution rate plus generation time and body size, employing the fossil record and genome datasets. We also explore the robustness of our estimations with respect to changes in topology, fossil constraints and substitution rate, and discuss the implications of our findings for understanding the platyrrhine radiation. Our results suggest that fossil constraints, topology and substitution rate have an important influence on our divergence time estimates. Bayesian estimates using conservative but realistic fossil constraints suggest that the LCA of extant platyrrhines existed at ca. 29 Ma, with the 95% confidence limit for the node ranging from 27–31 Ma. The LCA of extant platyrrhine monkeys based on substitution rate corrected by generation time and body size was established between 21–29 Ma. The estimates based on the two approaches used in this study recalibrate the ages of the major platyrrhine clades and corroborate the hypothesis that they constitute very old lineages. These results can help reconcile several controversial points concerning the affinities of key early Miocene fossils that have arisen among paleontologists and molecular systematists. However, they cannot resolve the controversy of whether these fossil species truly belong to the extant lineages or to a stem platyrrhine clade. That question can only be resolved by morphology. Finally, we show that the use of different approaches and well supported fossil information gives a more robust divergence time estimate of a clade.

Modeling lineage and phenotypic diversification in the New World monkey (Platyrrhini, Primates) radiation

Adaptive radiations that have taken place in the distant past can now be more thoroughly studied with the availability of large molecular phylogenies and comparative data drawn from extant and fossil species. Platyrrhines are a good example of a major mammalian evolutionary radiation confined to a single continent, involving a relatively large temporal scale and documented by a relatively small but informative fossil record. Here, we present comparative evidence using data on extant and fossil species to explore alternative evolutionary models in an effort to better understand the process of platyrrhine lineage and phenotypic diversification. Specifically, we compare the likelihood of null models of lineage and phenotypic diversification versus various models of adaptive evolution. Moreover, we statistically explore the main ecological dimension behind the platyrrhine diversification. Contrary to the previous proposals, our study did not find evidence of a rapid lineage accumulation in the phylogenetic tree of extant platyrrhine species. However, the fossil-based diversity curve seems to show a slowdown in diversification rates toward present times. This also suggests an early high rate of extinction among lineages within crown Platyrrhini. Finally, our analyses support the hypothesis that the platyrrhine phenotypic diversification appears to be characterized by an early and profound differentiation in body size related to a multidimensional niche model, followed by little subsequent change (i.e., stasis).

Persistence of a Mesozoic, non-therian mammalian lineage (Gondwanatheria) in the mid-Paleogene of Patagonia

We describe two isolated molariforms recovered from early–middle Eocene (early Lutetian) levels of northwestern Patagonia, Argentina. Comparisons with major lineages of therian and non-therian mammals lead us to refer them to a new genus and species of Gondwanatheria (Allotheria). There is a single root supporting each tooth that is very short, wide, rounded, and covered by cementum; the steep sidewalls, lack of a neck between the crown and root, and the heavily worn stage in both molariforms suggest that they were of a protohypsodont type. Both teeth are strongly worn at their centers, all along their length, with the labial edge less worn than the lingual; they show strong transverse crests that alternate with lingual grooves. The protohypsodont aspect of the teeth, as well as the strong, transverse crests, are suggestive of sudamericid affinities; on the other hand, the thin enamel layer and the occlusal pattern formed by the crests and grooves shows more similarities to molariform teeth of the Ferugliotheriidae. The new taxon adds evidence regarding the (1) extensive radiation of the Gondwanatheria throughout the Southern Hemisphere, (2) persistence of several lineages well after the Cretaceous/Paleogene boundary, and (3) early evolution of hypsodont types among South American herbivorous mammals.

New fossil platyrrhine from Argentina.

A new fossil primate was found in the Pinturas Formation, south-western Patagonia, at the type locality of the rare Soriacebus ameghinorum. It is a mandibular fragment with two molars that strongly resemble those of S. ameghinorum in their high and closed trigonid, distal expansion of the talonid, small hypoconulid, buccal expansion of the enamel and similar cusp development. But the type of S. ameghinorum differs by having mesiodistally longer trigonids, long premetacristids and more oblique distal trigonid walls, with the metaconid more lingually placed and the postmetacristid distolingually oriented and with the talonid being buccolingually smaller than the trigonid with a more restricted basin. M2 is slightly smaller than in the new specimen, and the buccal enamel is less flared. Although it is difficult to determine if this new specimen represents an individual variation of S. ameghinorum or a new species of Soriacebus, its morphology appears to be less derived than that of the type mandible, and it is, therefore, of systematic significance.

New early Miocene primate fossils from northern Patagonia, Argentina

Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ e CONICET, Av. Angel Gallardo 470, 1405 Ciudad de Buenos Aires, Argentina Centro Nacional Patagónico e CONICET, Boulevard Alte. Brown 2915, 9120 Puerto Madryn, Provincia de Chubut, Argentina Museo de Historia Natural de San Rafael e CONICET, Parque Mariano Moreno s/nro, 5600 San Rafael, Provincia de Mendoza, Argentina Museo Provincial de Ciencias Naturales ‘Prof. Dr. Juan A. Olsacher’, Dirección Provincial de Minería, Zapala, Provincia de Neuquén, Argentina

Fossil Alouattines and the Origins of Alouatta: Craniodental Diversity and Interrelationships

The howler monkey clade includes species of Alouatta and four extinct genera, Stirtonia, Paralouatta, Protopithecus, and probably Solimoea as well. Contrary to expectations, this radiation may have originated as a largely frugivorous group; advanced, Alouatta-like leaf-eating is a novelty well-developed in the Alouatta-Stirtonia sublineage only. Revised body mass estimates place Stirtonia and Paralouatta within the size range exhibited by the living forms and confirm the place of Protopithecus in a larger, baboon-like size range. While their dentitions are more primitive than the Alouatta-Stirtonia pattern, the cranial anatomy of Protopithecus and Paralouatta is distinctly similar to living howler monkeys in highly derived features relating to enlargement of the subbasal space in the neck and in head carriage, suggesting that ancestral alouattines may have had an enlarged hyolaryngeal apparatus. All alouattines also have relatively small brains, including Protopithecus, a genus that was probably quite frugivorous. The successful origins of the alouattine clade may owe more to key adaptations involving communication and energetics than dental or locomotor breakthroughs. While the fossil record confirms aspects of previous character-analysis reconstructions based on the living forms, alouattines experienced a complexity of adaptive shifts whose history cannot be recoverable without a more complete fossil record.*

New fossil primate from Chile

The southern parts of South America have yielded an important collection of a growing number of fossil platyrrhines, but the records so far have come exclusively from the Argentine Patagonia. No fossil primates have been found previously in southern Chile until the discovery of an isolated talus described below. This specimen was collected in February, 2000, at the locality of Alto Rio Cisnes, Aisen, Chile (Fig. 1), during a paleontological expedition of the Facultad de Ciencias Naturales, Sede Esquel (Universidad Nacional de la Patagonia “San Juan Bosco”). It is the second fossil primate ever found in Chile, after Chilecebus from the central part of the country (Flynn et al., 1995). The new talus (Fig. 2; Table 1) was collected at locality 5 of Marshall and Salinas (1990). It is approximately the size of Pithecia or slightly smaller and similar to other fossil tali found in Patagonia, such as that of cf. Dolichocebus from Gaiman (Gebo and Simons, 1987), those of cf. Soriacebus and cf. Carlocebus from Pinturas (Meldrum, 1990), and the recently described specimen from Canadon del Tordillo attributed to Proteropithecia (Kay et al., 1998). The new specimen SGO-PV 974 shows the following morphological characters. The talar head is broken dorsally, but appears oval in distal view. The talar neck is long relative to the body, forming an angle of about 45( relative to the plane of the fibular facet of the trochlea. In plantar view, the transition between the navicular facet and the anterior calcaneal facet is smooth with no ridge. The trochlea is moderately high, almost parallelsided and fairly flat, with a shallow trochlear groove. Also, the dorsal surface of the trochlea extends onto the dorsal surface of the neck, where a distinct lateral tibial stop is present. The medial tibial malleolar surface ends distally in a relatively shallow depression. The pit for the posterior talofibular ligament is deep. The lateral trochlear rim is sharp, but the distal end does not project forward, while the medial trochlear rim is lower and more rounded. The fibular trochlear facet is nearly flat, but the lateral process is broken. Both the posterior medial and lateral tubercles are eroded. The posterior calcaneal facet is long and quite broad and extends onto the posterior medial tubercle. Functionally, the characters described above indicate that the Rio Cisnes talus was from a predominantly quadrupedal and arboreal platyrrhine, with some features associated with leaping behavior (i.e., moderately high talar body with parallel-sided rims and long neck; see Gebo and Simons, 1987; Meldrum, 1990, 1993). Concerning this morphology, Meldrum (1990) has also found similarities between the tali of Carlocebus (which is the most similar to the Rio Cisnes talus—see below) and callitrichines, reflecting generalized quadrupedal adaptations, but lacking E-mail address: mtejedor@ciudad.com.ar (M.F. Tejedor). ARTICLE IN PRESS

A new species of the rare batomorph genus Hypolophodon (?latest Cretaceous to earliest Paleocene, Argentina)

Isolated teeth of a new species of the rare batomorph genus Hypolophodon were found in Paleocene beds of the Lefipan Formation (Maastrichtian-Paleocene) of southern Argentina. The new species H. patagoniensis differs from the type species H. sylvestris in the absence of an occlusal tranverse crest on the crown of unworn teeth and of a broad and rounded central uvula on the lingual face of the crown; and in the presence of a lower boundary of the enameloid smooth on all crown faces, many expanded basoapically striae on all sides of the root, and a deep root. It differs from the Eocene species H. dockery in the larger size, the less widely separated root branches, the presence of root foraminae or striae, the absence of uvula, and the deeper crown. The new species material, the two teeth from Jaguel Formation, and an indeterminate tooth of Hypolophodon from the Lower Cenozoic of Chile represent the sole records of the genus in the Southern Hemisphere. The shark fauna helped to date the bearing beds.

New primate locality from the early Miocene of Patagonia, Argentina

OBJECTIVES The purpose of this work is to present a new primate locality with evidence that increases the knowledge on the radiation of the extinct platyrrhine primates. MATERIALS AND METHODS We studied the new specimen and compared it to specimens identified as Mazzonicebus almendrae. RESULTS The new first and second molars were comparable to Mazzonicebus almendrae in all morphological details, allowing us to allocate the new specimen to M. almendrae and add comments on morphological variation in this species regarding the orientation of the labial cristae and development of the anterolingual cingulum. This new maxilla also present the first known M3 for the species. DISCUSSION The new specimen increases our knowledge of the extinct platyrrhines from Patagonia. Their age and geographical distribution ranges from early to middle Miocene in an area between 40° to 47° of southern latitude.