Fossil primates and the evolution of some primate locomotor systems

Of Paleocene primates only Plesiadapis is complete enough to reconstruct locomotor patterns; it was an arboreal scrambler, perhaps functioning like a large squirrel. Eocene lemurs (adapids) show an array of locomotor types much like certain modern Malagasy lemurs. The European Eocene tarsiid Necrolemur and the American Hemiacodon show the beginning of saltatory specializations in possession of elongated calcaneum and astragalus. Although not a direct anthropoid ancestor Necrolemur seems one of the best models for representing the early locomotor type from which higher primates arose. The Oligocene primates of Egypt (among which are the earliest undoubted pongids) are preserved with a forest fauna. Structures of long bones suggest they were arboreal. A considerable number of Miocene ape bones are known and those of Pliopithecus and Dryopithecus indicate similar adaptations. Of African Miocene forms, Dryopithecus major was a large, gorilla-sized animal, and hence perhaps primarily terrestrial. D. africanus was somewhat more arboreally adapted and a partial brachiator. The Italian fossil Oreopithecus, a coal-swamp dweller, shows indications of bipedality in pelvic structure. Ramapithecus, which is presumably ancestral to Australopithecus, shows palatal and facial patterns much like these later hominids, and probably hence had locomotor patterns more like men than like living apes; its lack of the dental specializations of apes strongly supports this suggestion.     

The nature of the transition in the dental mechanism from pongids to hominids

Many recent discoveries of Ramapithecus, and of probably ground-living dryopithecines, Dryopithecus (subgenus Sivapithecus), clarify the nature of the transition of the dental mechanism from that of pongids to the hominid stage with reduced canines and flattened cheek teeth with thick enamel.Faunal correlation with potassium/argon dated sites indicates that Sivapithecus and Ramapithecus appeared in the Old World about the same time, approximately 13 million years ago. The thickened molar enamel of these hominoids suggests a terrestrial adaptation in both groups, probably resulting from climatic changes. This adaptation was not necessarily a unique event in the ancestry of the two genera, for species of the two seem to have been different sizes when the change was made.New Ramapithecus finds come from Pyrgos, near Athens, from Çandir in Anatolia, and from Rudabánya, Hungary. At the latter site various specimens preserve all upper and lower teeth in place, while the Çandir and Pyrgos mandibles give important new information about symphyseal structure and orientation, as well as about arcade arrangement. The Rudabánya finds confirm, as do the others, marked facial foreshortening, relatively orthal incisors, anteriorly abbreviated mandible and canine reduction in Ramapithecus. The dental mechanics of Ramapithecus suggested from earlier described finds recovered in the Siwalik deposits of India and Pakistan, as well as at Fort Ternan, Kenya are clarified by the finds from Athens, Anatolia, and Hungary. Like Australopithecus, Ramapithecus mandibles have well-developed double transverse, shallow but transversely thick horizontal rami and anteriorly shifted, vertically oriented, deep ascending branches. These addes resemblances increase the probability that Ramapithecus is in or near the ancestry of Australopithecus and other hominids.     

A comment on relative molar breadth in Ramapithecus

The evidence for broad molars in Ramapithecus is reviewed in this study. Extensive comparisons are made with living and fossil pongids and the earliest undoubted hominids, the australopithecines. These comparisons suggest that Ramapithecus is like its closely related Indian relatives, D. indicus and D. sivalensis. Trends in molar shape are discussed as well as some problems in the interpretation of the adaptive meaning of relative molar breadth in hominoids.     

Anterior tooth reductions inRamapithecus

A metric study comparing the maxillary dentition ofRamapithecus to modern hominoids is undertaken. From such a study, one can determine whether the criterion of relative anterior tooth reduction is significant enough to support the placement ofRamapithecus in the hominid line of evolution. As it turns out, the anterior dental reduction is not significant and thus this particular criterion cannot be used for this purpose.     

Multivariate discriminant analysis of dental data bearing on early hominid affinities

The dimensions of hominoid dentitions are compared by multiple discriminant analysis. By this technique the fossil taxa are compared with living pongids and modern man in a multivariate framework. This enables the classification of the fossils to be made consistent with that of the living forms. H. africanus and H. erectus generally form the most compact grouping within the hominids, thus suporting the argument that these two species can indeed be lumped into a single genus. The degree of separation between H. africanus and Paranthropus is found to be at least as great as that between the genera of modern apes. Gigantopithecus sorts with the hominids rather than with the pongids and seems to be most closely related to Paranthropus.     

Notes on Ramapithecus, the earliest known hominid, and Dryopithecus

Recent paleontological analysis of the Higher Primate subfamily Dryopithecinae shows that fossils in this group can be referred to two genera, Ramapithecus and Dryopithecus. Ramapithecus is known from India and East Africa in Late Miocene or Early Pliocene time (about 14 m. years ago). The remains of Ramapithecus resemble closely the equivalent parts of the later Hominidae and contrast with those of the Pongidae. It is concluded that Ramapithecus is the earliest known hominid, some 5 or 6 times older than the oldest Pleistocene hominids. Dryopithecus is a pongid and contains as subgenera (Dryopithecus), (Proconsul), and (Sivapithecus). Probably part of (Proconsul) is ancestral to the chimpanzee and part to the gorilla, while part of (Sivapithecus) is ancestral to the orang-utan.     

Observations on mid-tertiary hominoids Sivapithecus and Ramapithecus

Detailed palaeontological analyses of the hominoids of the Miocene indicate the occurrence of forms belonging to Pongidae and Hominidae. Of these, Sivapithecus (Pongidae) with three contained species and Ramapithecus (Hominidae) with two distinct species can be recognized. These two families Pongidae and Hominidae were sufficiently well defined and distinct by the late Miocene about 14 million years ago. The author has discussed in brief the status of a few interesting finds of Sivapithecus and Ramapithecus based on the study of the originals preserved in India and America.     

Historical distribution,habitat requirements and feeding ecology of the genus Equus (Perissodactyla)

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Evidence of strong stabilizing effects on the evolution of boreoeutherian (Mammalia) dental proportions

The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolar–molar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of N = 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammals.     

Individual tooth macrowear pattern guides the reconstruction of Sts 52 (Australopithecus africanus) dental arches

The functional restoration of the occlusal relationship between maxillary and mandibular tooth rows is a major challenge in modern dentistry and maxillofacial surgery. Similar technical challenges are present in paleoanthropology when considering fragmented and deformed mandibular and maxillary fossils. Sts 52, an Australopithecus africanus specimen from Sterkfontein Member 4, represents a typical case where the original shape of the dental arches is no longer preserved. It includes a partial lower face (Sts 52a) and a fragmented mandible (Sts 52b), both incomplete and damaged to such an extent to thwart attempts at matching upper and lower dentitions. We show how the preserved macrowear pattern of the tooth crowns can be used to functionally reconstruct Sts 52's dental arches. High‐resolutiondental stone casts of Sts 52 maxillary and mandibular dentition were mounted and repositioned in a dental articulator. The occlusal relationship between antagonists was restored based on the analysis of the occlusal wear pattern of each preserved tooth, considering all dental contact movements represented in the occlusal compass. The reconstructed dental arches were three‐dimensional surface scanned and their occlusal kinematics tested in a simulation. The outcome of this contribution is the first functional restoration of A. africanus dental arches providing new morphometric data for specimen Sts 52. It is noteworthy that the method described in this case study might be applied to several other fossilspecimens. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.     

New proconsuloid postcranials from the early Miocene of Kenya

New early Miocene forelimb fossils have been recovered from the Songhor and Lower Kapurtay localities in southwestern Kenya. We describe four specimens that are similar in size and functional capabilities. Their specific allocation is problematic but these forelimb specimens must belong to either Rangwapithecus gordoni or Proconsul africanus. If these new postcranial specimens should belong to R. gordoni, on the basis of size and common dental specimens found at Songhor, they represent a new elbow complex. The morphology of these fossils is anatomically and functionally similar to that of Proconsul. The proconsuloid elbow complex allows extensive forelimb rotations and is capable of performing arboreal quadrupedalism and climbing activities. No suspensory adaptations are apparent. The proconsuloid elbow complex remains a good ancestral condition for hominoid primates.     

Underestimating intraspecific variation: The problem with excluding Sts 19 from Australopithecus africanus

Two analyses conclude that Sts 19 cannot be accommodated within the Australopithecus africanus hypodigm (Kimbel and Rak [1993] In Kimbel and Martin [eds.]: Species, Species Concepts, and Primate Evolution. New York: Plenum, pp. 461–484; Sarmiento [1993] Am. J. Phys. Anthropol. [Suppl.] 16:173). Both studies exclude Sts 19 because it possesses synapomorphies with Homo. Furthermore, according to Kimbel and Rak (1993), including Sts 19 in A. africanus results in an unacceptably high degree of polymorphism. This study aims to refute the null hypothesis that Sts 19 belongs to A. africanus. Twelve basicranial characters, as defined and implemented in Kimbel and Rak's study, were scored for casts of seven A. africanus and seven Homo habilis basicranial specimens. These characters were also examined on specimens from a large (N = 87) sample of African pongids. Contrary to Kimbel and Rak's (1993) findings, the null hypothesis is not refuted. The degree of polymorphism among A. africanus with Sts 19 included is less than that seen in Pan troglodytes. In addition, Sts 19 shares only one apomorphy with Homo. However, when treated metrically, Sts 19's morphology for this character is not significantly divergent from other A. africanus specimens. Am J Phys Anthropol 105:461–480, 1998. © 1998 Wiley-Liss, Inc.     

Palato-facial comparison ofDryopithecus (Proconsul) with extant catarrhines

Multivariate shape analysis of 15 palato-facial measurements of the RusingaD. africanus and MorotoD. major specimens in comparison with apes and monkeys fails to support the hypothesis of special relationship between the dryopithecine species and extant African pongids. TheD. africanus shares with gibbons and cercopithecoids the primitive catarrhine metrical pattern, while chimpanzees and gorillas show a different, derived pattern. TheD. major shows partial convergence on the shape pattern typifying gorillas.     

Critique of ‘Australopithecus afarensis’ as a single species based on dental metrics and morphology

Leonard andHegmon (1987) compare a series of dental metrics of ‘Australopithecus afarensis Johanson, White, andCoppens, 1978’ with criteria for modern apes, to test the hypothesis that ‘A. afarensis’ represents a single species. They also compare the morphology of the lower third premolar. The dental breadth of ‘A. afarensis’ shows a wide range of variation, particularly in the lower third premolar morphology which displays greater variation than in modern apes—yet the study concludes that the single species hypothesis cannot be rejected. The study is flawed by applying criteria for pongids inappropriate for a hominid. When ‘A. afarensis’ is compared with criteria for hominids, the range of variation in dental size, breadth, and third premolar morphology is greater than that in any hominid species. The single species hypothesis is, therefore, once again rejected. Moreover, the name ‘A. afarensis’ is preoccupied byPraeanthropus africanus (Weinert) and must be dropped.     

Size and shape variation in the proximal femur of Australopithecus africanus

Aside from use as estimates of body mass dimorphism and fore to hind limb joint size comparisons, postcranial elements have not often contributed to assessments of variation in Australopithecus africanus. Meanwhile, cranial, facial, and dental size variation is interpreted to be high or moderately high. Further, the cranial base and face express patterns of structural (shape) variation, which are interpreted by some as evidence for the presence of multiple species. Here, the proximal femur is used to consider postcranial size and shape variation in A. africanus. Original fossils from Makapansgat and Sterkfontein, and samples from Homo, Pan, Gorilla, and Pongo were measured. Size variation was assessed by comparing the A. africanus coefficient of variation to bootstrapped distributions of coefficient of variation samples for each taxon. Shape variation was assessed from isometrically adjusted shape variables. First, the A. africanus standard deviation of log transformed shape variables was compared to bootstrapped distributions of logged standard deviations in each taxon. Second, shape variable based Euclidean distances between fossil pairs were compared to pairwise Euclidean distance distributions in each reference taxon. The degree of size variation in the A. africanus proximal femur is consistent with that of a single species, and is most comparable to Homo and Pan, lower than A. afarensis, and lower than some estimates of cranial and dental variation. Some, but not all, shape variables show more variation in A. africanus than in extant taxa. The degree of shape difference between some fossils exceeds the majority of pairwise differences in the reference taxa. Proximal femoral shape, but not size, variation is consistent with high estimates of A. africanus cranial variation.     

The postcranium of Miocene hominoids: Were dryopithecines merely “dental apes”?

This paper reviews the non-dental morphological configuration of Miocene hominoids with special reference to the hypothesis of linear relationships between certain fossil species and living analogues. Metrical analysis of the wrist shows thatDryopithecus africanus andPliopithecus vindobonensis are unequivocally affiliated with the morphological pattern of quadrupedal monkeys. Similar analyses of the fossil hominoid elbow shows that they are more cercopithecoid-like than hominoid-like. Multivariate analysis of theP. vindobonensis shoulder in the matrix of extant Anthropoidea indicate that this putative hylobatine fossil shows no indication of even the initial development of hominoid features. The total morphological pattern of theD. africanus forelimb as assessed by principal coordinates analysis of allometrically adjusted shape variables has little resemblance toPan. Likewise, the feet and proximal femora of the Miocene fossils are unlike any living hominoid species. Even theD. africanus skull is similar to extant cercopithecoids in several features. Although ancestors cannot be expected to resemble descendants in every way, the striking dissimilarity between Miocene and extant hominoids seems to eliminate the consideration of a direct ancestor-descendant relationship between specific Miocene and modern forms.     

Gliridae (Rodentia,Mammalia) with a simple dental pattern: a new genus and new species from the European Early and Middle Miocene

A new genus of Gliridae, Simplomys gen. nov. is proposed. It contains glirids with a simplified dental pattern from the European Early and Middle Miocene. Simplomys gen. nov. includes several species originally described as Pseudodryomys such as Simplomys simplicidens, Simplomys robustus, Simplomys julii, and Simplomys aljaphi. In addition, a new species, Simplomys meulenorum sp. nov. , is proposed from the Spanish Miocene. The species of this genus share not only a very reduced and simplified dental morphology, but also unique dental proportions that clearly separate them from any other genera of Gliridae. Simplomys gen. nov. is recorded in most of the fossil faunas from the Early and Middle Miocene of the Iberian Peninsula, and shows the maximum diversity in this area during Mammal Neogene Zones MN 3 and MN 4. The genus has been also recorded in other European countries such as France, Germany, and Switzerland, conferring to this very characteristic taxon an important role for biochronological correlations within the European continent. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 157 , 622–652.     

Tooth Wear Difference Between the Yuanmou Hominoid and <Emphasis Type="Italic">Lufengpithecus</Emphasis>

The Late Miocene hominoids recovered from Lufeng (Lufengpithecus) and Yuanmou of Yunnan Province, China, are among the most numerous hominoid fossils in Eurasia. They have yielded critical evidence for the evolutionary history, biogeography and paleobiology of Miocene hominoids. We examined and compared the wear pattern and differences of 804 molars of the Yuanmou hominoid and Lufengpithecus. Our results indicate that both the upper and lower molars of the Yuanmou hominoids were more heavily worn than those of Lufengpithecus. The wear patterns of the individual molars between the Yuanmou hominoid and Lufengpithecus also are different. The heaviest wear of lower molars of the Yuanmou hominoid occur in M₂, followed by M₁ and M₃. In Lufengpithecus, M₁ and M₃ were more heavily worn than M₂. There are differences in wear between the upper and lower molars for the two hominoids. Among the various factors related to tooth wear, we suggest that the main reason for the tooth wear differences between the Yuanmou hominoid and Lufengpithecus may be that they had different diets. More soft dietary items like leaves and berries were probably consumed by Lufengpithecus, and the Yuanmou hominoid may mainly have feed on harder or frugivorous diets. This result complements findings from previous studies of tooth size proportion, and the development of lower molar shearing crests in the 2 samples. Enamel thickness, living environment, behavior patterns, and population structure also might account for dental wear differences between the Yuanmou hominoid and Lufengpithecus.     

Australopithecus, Meganthropus and Ramapithecus

The South African members of Australopithecus form a single group, trending from earlier, more gracile or smaller forms, to later, more robust or larger forms, in accordance with the “Law of Cope”. This is supported by the evidence of the lower first deciduous molar: it is only slightly molarized in the earlier, smaller forms and astonishingly heavily molarized in the later, robust forms, such as that of Kromdraai. Hence, Robinson's view that two different genera are represented by the gracile and robust forms is not supported here. A. robustus is seen as a late offshoot of the Australopithecus stem. The resemblance of the Taung dm₁ to that of Sinanthropus, except for the more differentiated talonid of the Taung specimen, suggests that the separation of the Australopithecinae and Homininae must have taken place at an earlier stage than that represented by the oldest South African Australopithecinae. The lower jaw of Meganthropus of Java combines certain characteristics of A. africanus with those of A. robustus: Meganthropus might provisionally be called “Australopithecoid”. The geographically intermediate India has yielded a hominid, Ramapithecus punjabicus, but the author does not consider “Kenyapithecus” to be a hominid. “K. wickeri” is a pongid species of its own and “K. africanus” a Proconsul. Ramapithecus sensu stricto is known only from the Indian Siwaliks and the author suggests that the transition from Ramapithecus to a still unknown Australopithecus took place in the same region prior to their migration into Africa and Southeast Asia.