Enamel microstructure in lemuridae (mammalia,primates): Assessment of variability

This study describes the molar enamel microstructure of seven lemurid primates: Hapalemur griseus, Varecia variegata, Lemur catta, Lemur macaco, Lemur fulvus rufus, Lemur fulvus fulvus, and Lemur fulvus albifrons. Contrary to earlier accounts, which reported little or no prism decussation in lemurid enamel, both Lemur and Varecia molars contain a prominent inner layer of decussating prisms (Hunter-Schreger bands), in addition to an outer radial prism layer, and a thin, nonprismatic enamel surface layer. In contrast, Hapalemur enamel consists entirely of radial and, near the surface, nonprismatic enamel. In addition, for all species, prism packing patterns differ according to depth from the tooth surface, and for all species but Varecia (which also has the thinnest enamel of any lemurid), average prism area increases from the enamel-dentine junction to the surface; this may be a developmental solution to the problem of accommodating a larger outer surface area with enamel deposited from a fixed number of cells. Finally, contradicting some previous reports, Pattern 1 prisms predominate only in the most superficial prismatic enamel. In the deeper enamel, prism cross-sections include both closed (Pattern 1) and arc-shaped (Pattern 2 or, most commonly, Pattern 3). This sequence of depth-related pattern change is repeated in all taxa. It should also be emphasized that all taxa can exhibit all three prism patterns in their mature enamel. The high degree of quantitative and qualitative variation in prism size, shape, and packing suggests that these features should be used cautiously in phylogenetic studies. Hapalemur is distinguished from the other lemurids by unique, medially constricted or rectangular prism cross-sections at an intermediate depth and the absence of prism decussation, but, without further assessment of character polarity, these differences do not clarify lemurid phylogenetic relations. Some characters of enamel microstructure may represent synapomorphies of Lemuridae, or of clades within Lemuridae, but homoplasy is likely to be common. Homoplasy of enamel characters may reflect functional constraints. © 1994 Wiley-Liss, Inc.     

Enamel microstructure and molar wear in the greater galago,Otolemur crassicaudatus (mammalia,primates)

This study describes the molar enamel microstructure of the greater galago, based on SEM study of four individuals. Galago molar enamel consists primarily of radially oriented Pattern 1 prisms. However, the most superficial enamel is characterized by regions of poorly developed prisms or nonprismatic enamel, and Pattern 3 prisms can be found at depths intermediate and deep to the enamel surface. Orientations of prism long axes relative to wear surfaces differ among functionally distinct regions (cuspal facets, Phase I/II facets, and crushing basins). Consequently, orientations of enamel crystallites relative to these surfaces also differ. Because crystallites are the structural unit involved in enamel abrasion, these differences in orientation may have important effects on molar wear patterns. Crystallite orientations differ most between cuspal facets and Phase I/II facet surfaces. Cuspal facets are characterized by near surface-parallel interprismatic and surface-oblique prismatic crystallites. Previous experimental studies suggest that this arrangement is most resistant to wear when surface-normal (compressive) loads predominate. In contrast, prismatic and interprismatic crystallites intercept Phase I/II facet surfaces obliquely, an arrangement expected to resist abrasion when surface-parallel (shearing) loads predominate. Superficial enamel is preserved at most basin surfaces, indicating that these regions are subject to comparatively little abrasive wear. These results support the hypothesis that galago occlusal enamel is organized so as to resist abrasion of different functional regions, a property that may prove important in maintaining functional efficiency. However, this largely reflects constraints of occlusal topography on a microstructure typical of many mammals and thus does not appear to represent a structural innovation. © 1993 Wiley-Liss, Inc.     

Enamel thickness and development in a third permanent molar of Gigantopithecus blacki

A ground section was prepared from a lower right M3 attributed to Gigantopithecus blacki as close as possible to axial plane of the mesial cusps. Daily cross striations were imaged, measured and counted in each cusp using polarised light microscopy. Long-period striae of Retzius were counted in the lateral enamel and their periodicity determined from counts and measurements of daily cross striations between adjacent striae. Cross striation spacings in the cusps were between 3.8 microm at the enamel dentine junction and 6 microm close to the enamel surface. Cuspal enamel formation times were long (800 days in the protoconid and 620 days in the metaconid). Linear enamel thickness was as much as 3.75 mm in the protoconid. There were 63 and 61 long-period striae of Retzius in the mesial aspects of the lateral enamel and the periodicity was 11 days. Lateral enamel formation took 1493 and 1291 days and when summed with cuspal enamel formation times totalled 4 years in the protoconid and 3.5 in the metaconid. Relative enamel thickness was 23, calculated through the mesial cusps. This falls short of that in the so-called 'thick hyper-thick' enamel described in 'robust' australopithecines to which Gigantopithecus blacki has previously been compared in both its dental and mandibular morphology. With respect to enamel thickness, therefore, Gigantopithecus blacki falls squarely among an increasingly large number of Miocene hominoids that can all be described as having 'thick enamel'.     

Enamel thickness in the Middle Miocene great apes Anoiapithecus,Pierolapithecus and Dryopithecus

On the basis of industrial computed tomography, relative enamel thickness (RET) is computed in three Middle Miocene (ca 11.9–11.8 Ma) hominoids from Abocador de Can Mata (Vallès-Penedès Basin, Catalonia, Spain): Pierolapithecus catalaunicus from BCV1 and Anoiapithecus brevirostris from C3-Aj, interpreted as stem hominids; and Dryopithecus fontani from C3-Ae of uncertain phylogenetic affinities. Pierolapithecus displays an average RET value of 19.5, Anoiapithecus of 18.6 and Dryopithecus of 10.6. The thick-enamelled condition of Pierolapithecus and Anoiapithecus is also characteristic of afropithecids, including the more derived kenyapithecins from the early Middle Miocene of Eurasia (Griphopithecus and Kenyapithecus). Given the presence of other dentognathic and craniofacial similarities, thick enamel may be interpreted as a symplesiomorphy of the Hominidae (the great ape and human clade), which would have been later independently modified along several lineages. Given the correlation between thick enamel and hard-object feeding, our results suggest that thick enamel might have been the fundamental adaptation that enabled the out-of-Africa dispersal of great-ape ancestors and their subsequent initial radiation throughout Eurasia. The much thinner enamel of Dryopithecus is difficult to interpret given phylogenetic uncertainties, being either a hominine synapomorphy or a convergently developed feature.     

Enamel thickness,microstructure and development in Afropithecus turkanensis

Afropithecus turkanensis, a 17-17.5 million year old large-bodied hominoid from Kenya, has previously been reported to be the oldest known thick-enamelled Miocene ape. Most investigations of enamel thickness in Miocene apes have been limited to opportunistic or destructive studies of small samples. Recently, more comprehensive studies of enamel thickness and microstructure in Proconsul, Lufengpithecus, and Dryopithecus, as well as extant apes and fossil humans, have provided information on rates and patterns of dental development, including crown formation time, and have begun to provide a comparative context for interpretation of the evolution of these characters throughout the past 20 million years of hominoid evolution. In this study, enamel thickness and aspects of the enamel microstructure in two A. turkanensis second molars were quantified and provide insight into rates of enamel apposition, numbers of cells actively secreting enamel, and the time required to form regions of the crown. The average value for relative enamel thickness in the two molars is 21.4, which is a lower value than a previous analysis of this species, but which is still relatively thick compared to extant apes. This value is similar to those of several Miocene hominoids, a fossil hominid, and modern humans. Certain aspects of the enamel microstructure are similar to Proconsul nyanzae, Dryopithecus laietanus, Lufengpithecus lufengensis, Graecopithecus freybergi and Pongo pygmaeus, while other features differ from extant and fossil hominoids. Crown formation times for the two teeth are 2.4-2.6 years and 2.9-3.1 years respectively. These times are similar to a number of extant and fossil hominoids, some of which appear to show additional developmental similarities, including thick enamel. Although thick enamel may be formed through several developmental pathways, most Miocene hominoids and fossil hominids with relatively thick enamel are characterized by a relatively long period of cuspal enamel formation and a rapid rate of enamel secretion throughout the whole cusp, but a shorter total crown formation time than thinner-enamelled extant apes.     

Paleosols and paleoenvironments of the middle Miocene,Maboko Formation,Kenya

The middle Miocene (15 Ma) Maboko Formation of Maboko Island and Majiwa Bluffs, southwestern Kenya, has yielded abundant fossils of the earliest known cercopithecoid monkey (Victoriapithecus macinnesi), and of a kenyapithecine hominoid (Kenyapithecus africanus), as well as rare proconsuline (Simiolus leakeyorum, cf. Limnopithecus evansi) and oreopithecine apes (Mabokopithecus clarki, M. pickfordi), and galagids (Komba winamensis). Specific habitat preferences can be interpreted from large collections of primate fossils in different kinds of paleosols (pedotypes). Fossiliferous drab-colored paleosols with iron-manganese nodules (Yom pedotype) are like modern soils of seasonally waterlogged depressions (dambo). Their crumb structure and abundant fine root-traces, as well as scattered large calcareous rhizoconcretions indicate former vegetation of seasonally wet, wooded grassland. Other fossiliferous paleosols are evidence of nyika bushland (Ratong), and early-successional riparian woodland (Dhero). No fossils were found in Mogo paleosols interpreted as saline scrub soils. Very shallow calcic horizons (in Yom, Ratong, and Mogo paleosols) and Na-montmorillonite (in Mogo) are evidence of dry paleoclimate (300-500 mm MAP=mean annual precipitation). This is the driest paleoclimate and most open vegetation yet inferred as a habitat for any Kenyan Miocene apes or monkeys. Victoriapithecus was abundant in dambo wooded grassland (Yom) and riparian woodland (Dhero), a distribution like that of modern vervet monkeys. Kenyapithecus ranged through all these paleosols, but was the most common primate in nyika bushland paleosols (Ratong), comparable to baboons and macaques today. Mabokopithecus was virtually restricted to riparian woodland paleosols (Dhero), and Simiolus had a similar, but marginally wider, distribution. Habitat preferences of Mabokopithecus and Simiolus were like those of modern colobus monkeys and mangabeys. A single specimen of Komba was found in dambo wooded grassland paleosol (Yom), a habitat more like that of the living Senegal bushbaby than of rainforest galagids. A shift to non-forest habitats may explain the terrestrial adaptations of Victoriapithecus, basal to the cercopithecid radiation, and of Kenyapithecus, basal to the hominoid radiation. Both taxa are distinct from earlier Miocene arboreal proconsulines, oreopithecines and galagids.     

Preliminary investigation of dental microstructure in the Yuanmou hominoid (Lufengpithecus hudienensis), Yunnan Province,China

Fieldwork in the Yuanmou Basin of southern China has uncovered a large assemblage of late Miocene hominoid fossils assigned to Lufengpithecus hudienensis. Two mandibular first molars from this species were made available for histological analysis as part of a larger ongoing study on the ontogeny of dental development in Miocene to Recent hominoids. Results are compared with published and unpublished data on tooth growth in a wide range of extant and extinct hominoids. The Yuanmou molars are smaller than those of Lufengpithecus lufengensis and have markedly shorter crown formation times, overlapping slightly with Pan, but most similar to Proconsul and Dryopithecus. In other aspects of molar development (including enamel extension rates and enamel thickness), L. hudienensis shows similarities with all extant hominoids, in particular, Pongo. Ultimately, charting the ontogeny of molar crown formation may help shed light on the relationship of Lufengpithecus hudienensis to orangutans, and other Miocene to Recent hominoids.     

Some observations on enamel thickness and enamel prism packing in the miocene hominoid Otavipithecus namibiensis

Otavipithecus namibiensis is currently the sole representative of a Miocene hominoid radiation in subequatorial Africa. Several nondestructive techniques, such as computed tomography (CT) and confocal microscopy (CFM), can provide useful information about dental characteristics in this southern African Miocene hominoid. Our studies suggest that the molars of Otavipithecus are characterized by (1) thin enamel and (2) a predominance of pattern 1 enamel prism. Together, these findings provide little support for the recent suggestion of an Afropithecini clade consisting of Otavipithecus, Heliopithecus, and Afropithecus. Instead, they lend some (though not conclusive) support to the suggestion of an Otavipithecus/African ape clade distinct from Afropithecus. © 1995 Wiley-Liss, Inc.     

Microstructural Reinforcement in the Canine Enamel of the Hyaenid Crocuta crocuta, the FelidPuma concolorand the Late Miocene Canid Borophagus secundus

In bone-eating carnivores such as the hyena Crocuta crocuta, the tooth enamel contains a secondary vertical prism decussation phyletically derived from the wavelike horizontal decussation of primitive carnivores. The structure resists fracture under vertical, oblique, and horizontal tensile stresses, owing to the following modifications of the primitive structure. Positions of wave crests and of wave troughs are synchronized in the vertically successive layers of decussating prisms. Prisms in each successive layer run in a common direction at the crests and in a common but reversed direction at the troughs. Between the crests and troughs, prisms in obliquely slanting layers often retain their primitively reversed prism directions. Near the enamel–dentine junction (EDJ), irregular horizontal decussation is retained. In the upper canine of C. crocuta, a consumer of large bones, secondary vertical decussation is largely confined to the labial and anterior sides of the crown toward the tip where modeling of the static stresses predicts the tensile stresses to be highest and aligned vertically. In Puma concolor, which does not consume large bones, secondary vertical decussation is absent, indicating stress magnitude to be a critical factor in the selection for secondary vertical decussation. The canine enamel in Borophagus secundus, an extinct canid with derived aspects of skull and dental shape like those in hyenas, has dental structures similar to those in C. crocuta but which differ in several ways. The wavelike shapes of the decussation planes are better developed in transverse sections in B. secundus than in C. crocuta, suggesting either the folds are less modified or they dip at a steeper angle. Secondary vertical decussation in B. secundus is more extensive around the circumference of the canine than in C. crocuta, related to a difference in cross-sectional shape of the tooth. Vertical prism decussation may have been more frequently attained in carnivorous mammals than in ungulates because of the more random orientation of dental stresses which creates a selective advantage for wavy decussation planes—a structural transition to vertical decussation.     

Early Miocene catarrhine dietary behaviour: the influence of the Red Queen Effect on incisor shape and curvature

The early Miocene catarrhine fossil record of East Africa represents a diverse and extensive adaptive radiation. It is well accepted that these taxa encompass a dietary range similar to extant hominoids, in addition to some potentially novel dietary behaviour. There have been numerous attempts to infer diet for these taxa from patterns of dental allometry and incisor and molar microwear, however, morphometric analyses until now have been restricted to the post-canine dentition. It has already been demonstrated that given the key functional role of the incisors in pre-processing food items prior to mastication, there is a positive correlation between diet and incisal curvature (Deane, A.S., Kremer, E.P., Begun, D.R., 2005. A new approach to quantifying anatomical curvatures using High Resolution Polynomial Curve Fitting (HR-PCF). Am. J. Phys. Anthropol. 128(3), 630-638.; Deane, A.S., 2007. Inferring dietary behaviour for Miocene hominoids: A high-resolution morphometric approach to incisal crown curvature. Ph.D. Dissertation. The University of Toronto.). This study seeks to re-examine existing dietary hypotheses for large-bodied early Miocene fossil catarrhines by contrasting the incisal curvature for these taxa with comparative models derived from prior studies of the correlation between extant hominoid incisor curvature and feeding behaviour. Incisor curvature was quantified for 78 fossil incisors representing seven genera, and the results confirm that early Miocene fossil catarrhines represent a dietary continuum ranging from more folivorous (i.e., Rangwapithecus) to more frugivorous (i.e., Proconsul) diets, as well as novel dietary behaviours that are potentially similar to extant ceboids (i.e., Afropithecus). Additionally, early Miocene fossil catarrhine incisors are less curved than extant hominoid incisors, indicating a general pattern of increasing mesio-distal and labial curvature through time. This pattern of morphological shifting is consistent with the Red Queen Effect (Van Valen, L., 1973. A new evolutionary law. Evol. Theory 1, 1-30), which predicts that taxa that are removed from one another by geological time, although potentially having similar diets, may exhibit differing degrees of a similar dietary adaptation (i.e., differing degrees of incisal curvature).     

Sivapithecus simonsi,a new species of miocene hominoid,with comments on the phylogenetic status of the ramapithecinae

The Ramapithecinae are an extinct, mainly Miocene group of hominoids, whose relationship to modern taxa is disputed. Some regard them as hominids, while others view them as ancestral toPongo,or even as the group ancestral to both hominids and extant apes. In this paper a systematic revision of Ramapithecinae is undertaken. Sivapithecus sivalensis andRamapithecus punjabicus are considered the same species, with the former name having priority. A new Indian species,Sivapithecus simonsi,is recognized. Ramapithecine anatomy is reviewed and compared with that of gracileAustralopithecus, early and middle MioceneProconsul andDryopithecus, and living pongidsPan, Gorilla, andPongo.Ramapithecines are shown to be much more primitive or “ape-like” than some have argued. Anatomical data are evaluated cladistically with several results. Parallel evolution in the jaws, teeth, and facial structure of hominoids appears to be the rule rather than the exception. Bearing this in mind, nevertheless, from the available evidence of anatomy, ramapithecines are cladistically hominids.     

The species of Thalerosphyrus Eaton, 1881 (Insecta,Ephemeroptera, Heptageniidae,Ecdyonurinae) in Java and Sumatra,with some comments on the diversity of the genus in the Oriental Realm

Three species belonging to the genus Thalerosphyrus Eaton, 1881 are reported from Java and Sumatra. The nymphs of Th. determinatus (Walker, 1853) from Java, Th. sinuosus (Navás, 1933) from Java and Sumatra and Th. lamuriensis Sartori, 2014 from Sumatra are redescribed. The egg morphology of the three species is also presented for the first time. A key to the nymphs is proposed. General considerations on the composition of the genus Thalerosphyrus in the Oriental Realm are given. The distribution of the genus is greatly expended, and currently ranges over the Himalaya and Sumbawa in the Sunda Islands.     

A fossil fruit wing of Dipterocarpus from the middle Miocene of Fujian, China and its palaeoclimatic significance

Dipterocarpus zhengae sp. nov. is described from the middle Miocene Fotan Group of Zhangpu county, Fujian Province, Southeast China on the basis of a fruit wing. Three kinds of venation of the calyx longer lobes (enlarged sepals) occur in the winged fruits of extant Dipterocarpus. The fossil species is referred to the kind having three primary veins and within that category is most similar to extant Dipterocarpus gracilis Blume in the size of the longer lobe as well as its venation. The occurrence of the fruit wing of Dipterocarpus, together with palynological evidence, indicates unequivocally that a tropical climate and tropical rain forest occurred in Zhangpu during the middle Miocene, warmer and more humid than at the present day. The palaeobiogeography of Dipterocarpus is reviewed.     

Correlation of tooth size and body size in living hominoid primates, with a note on relative brain size in Aegyptopithecus and Proconsul.

Second molar length and body weight are used to test the correlation between tooth size and body size in living Hominoidea. These variates are highly correlated (r= 0.942, p less than 0.001), indicating that tooth size can be used in dentally unspecialized fossil hominoids as one method of predicting the average body weight of species. Based on tooth size, the average body weight of Aegyptopithecus zeuxis is estimated to have been beteen 4.5 and 7.5 kg, which is corroborated by known cranial and postcranial elements. Using Radinsky's estimates of brain size, the encephalization quotient (EQ) for Aegyptopithecus was between 0.65 and 1.04. A similar analysis for Proconsul africanus yields a body weight between 16 and 34 kg, and an EQ between 1.19 and 1.96.     

A juvenile skull of Acerorhinus yuanmouensis (Mammalia: Rhinocerotidae) from the Late Miocene hominoid fauna of the Yuanmou Basin (Yunnan,China)

A unique juvenile skull bearing both milk premolars and unerupted but fully developed permanent premolars and molars (observed using X-ray microcomputed tomography), and some isolated upper cheek teeth, all from the Late Miocene hominoid fauna of the Yuanmou Basin (Yunnan, China), closely resemble craniodental material of Acerorhinus yuanmouensis Zong, 1998 from the same locality, and are referred to this species. A phylogenetic analysis based on 214 craniodental morphological characters scored for 31 terminal taxa reveals that A. yuanmouensis should be assigned to the genus Acerorhinus indeed. The newly discovered specimens improve our understanding of this species, especially with respect to the morphology of the milk premolars and premolars. Two intraspecific variations in the upper premolars are noted: a lingual bridge may be present or absent, and the lingual cingulum continuous or reduced. The analysis also indicates that: the phylogenetic status of Acerorhinus lufengensis Deng and Qi, 2009 should be reconsidered; “Aceratherium” huadeensis Qiu, 1979 does neither belong to Aceratherium nor Acerorhinus, and its phylogenetic status remains debatable.     

饲料中糖水平对不同食性海水鱼类PEPCK基因表达和酶活性的影响

磷酸烯醇式丙酮酸羧激酶(Phosphoenolpyruvate carboxykinase, PEPCK, E.C.4.1.1.32)是水生生物糖异生代谢的关键限速酶. 实验以杂食性罗非鱼(Oreochromis niloticus)、温和肉食性卵形鲳鲹(Trachinotus ovatus)、凶猛肉食性军曹鱼(Rachycentron canadum)三种不同食性海水养殖鱼类为研究对象, 以糊精为饲料糖源, 分别设置不同饲料糖添加水平(低糖组LD、中糖组MD、高糖组HD)等氮等能饲料, 每种鱼分别随机选取60尾体格均匀的幼鱼进行为期8周的饲养实验, 同时克隆卵形鲳鲹胞质型PEPCK基因cDNA全长序列, 以期探讨不同饲料糖水平对不同食性鱼类PEPCK活性及其mRNA表达的影响. 结果显示: 卵形鲳鲹PEPCK基因cDNA共2652 bp, 含1个编码624个氨基酸的开放阅读框, 三种不同食性海水鱼类PEPCK的生物信息学比较分析显示相似度达90%以上, 在结构和功能上具有较高的保守和同源性. 养殖实验结果显示: 随着饲料糖水平的增加, 三种鱼肝脏中PEPCK酶活性均降低, 其中卵形鲳鲹、军曹鱼HD组PEPCK活性比LD组分别显著降低28.05%和26.03% (P0.05). 而其肝脏中PEPCK mRNA表达水平同样均随饲料碳水化合物水平增加而受到抑制, 其中罗非鱼、卵形鲳鲹、军曹鱼中LD组PEPCK的mRNA分别是HD组的100倍、4.3倍和4.77倍. 结果表明鱼类的糖异生能力可能与其食性有关, 三种鱼PEPCK酶活性与基因表达量随着饲料糖水平的增加而受到显著抑制, 且mRNA表达抑制程度随食性不同而具有较大差异, 以杂食性罗非鱼受抑制程度最高, 凶猛肉食性军曹鱼受抑制程度最低.       

A new species of Dicranocentrus (Collembola,Entomobryidae) from China with comments on the systematic position of the genus

Dicranocentrus liuae sp. n. is described from the northern subtropical region of China. The new species is most similar to D. wangi Ma & Chen, 2007, but differs from it in the relatively shorter Ant. V, the 1+1 central macrochaetae on Abd. III, the number of chaetae on tenaculum, and the absence of dental spines. The systematic position of Dicranocentrus is also discussed. Present evidence, particularly S-chaetotaxy, indicates that the genus is closer to Heteromurus than to the unscaled species of Orchesella and Orchesellides.     

Microwear, mechanics and the feeding adaptations of Australopithecus africanus

Recent studies of dental microwear and craniofacial mechanics have yielded contradictory interpretations regarding the feeding ecology and adaptations of Australopithecus africanus. As part of this debate, the methods used in the mechanical studies have been criticized. In particular, it has been claimed that finite element analysis has been poorly applied to this research question. This paper responds to some of these mechanical criticisms, highlights limitations of dental microwear analysis, and identifies avenues of future research.