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.     

Mandibular ontogeny in the miocene great apeDryopithecus

The type mandible of Dryopithecus fontani,Lartet 1856, has been discovered to be not fully adult. Its development corresponds in dental age to that of a 6-to 8-year-old chimpanzee. Because of its immaturity, a number of seemingly distinctive features of this mandible (some of which resemble hominids) would have been lost with full adulthood. Closed tooth rows, a recurved canine, and a vertical ascending mandibular ramus are related to the age of the specimen. They therefore do not foreshadow hominid characteristics. It is stressed that consideration of individual age is an important factor in interpreting the dentitions of fossil and extant hominoids.     

Late miocene magnetobiostratigraphy of Crete

Six Upper Miocene marine clay sections on Crete (Greece) have been subjected to a detailed magnetobiostratigraphic analysis. Six correlatable polarity zones are recognized and these demonstrate the regional synchrony of planktonic foraminiferal biohorizons.By way of correlation to the magnetic polarity time-scale of Lowrie and Alvarez (1981), the Cretan sequence is assigned to polarity chronozones 5 (anomaly 3A) and 6. The new chronology provides an age of 5.6 Ma for the first occurrence datum (FOD) of theGloborotalia conomiozea group in the Mediterranean, an age of 6.0 Ma for the FOD ofG. menardii form 5 and an age of 6.6 Ma for the last occurrence datum (LOD) ofG. menardii form 4.Correlating the polarity record of the New Zealand Blind River section (Kennett and Watkins, 1974), with the magnetic polarity time-scale provides an age of 6.0 Ma for the evolutionary appearance ofGloborotalia conomiozea, which is in complete agreement with the age of 6.1 ± 0.1Ma given by Loutit and Kennett (1979). The demonstrated diachrony of 0.4 Ma between the New Zealand FOD ofG. conomiozea and its Mediterranean counterpart is explicable in view of the different nature of the two events, the one in New Zealand being evolutionary and the one in the Mediterranean migrational.The FOD of theG. conomiozea group in the Tortonian/Messinian boundary stratotype section coincides with the level proposed by Colalongo et al. (1979) to mark the base of the Messinian. Since the FOD of theG. conomiozea group in Crete and in Sicily are most probably time-equivalent, the age of the Tortonian/Messinian boundary is fixed at 5.6 Ma.The youngest sediments incorporated in this study extend into the Gilbert chronozone and antedate the main evaporitic phase. Consequently, the Messinian evaporitic body is younger than the base of the Gilbert chronozone, the age of which is fixed at 5.3 Ma. Adopting an age of 5.0 Ma for the Miocene/Pliocene boundary would imply that evaporites and post-evaporitic Lago Mare sediments were deposited in some 300,000 years and suggests that in the central parts of the Mediterranean basins evaporites must have accumulated at rates of some 3 m per 1000 years.     

Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest

Two opposing niche processes have been shown to shape the relationship between ecological traits and species distribution patterns: habitat filtering and competitive exclusion. Habitat filtering is expected to select for similar traits among coexisting species that share similar habitat conditions, whereas competitive exclusion is expected to limit the ecological similarity of coexisting species leading to trait differentiation. Here, we explore how functional traits vary among 19 understory palm species that differ in their distribution across a gradient of soil resource availability in lower montane forest in western Panama. We found evidence that habitat filtering influences species distribution patterns and shifts community-wide and intraspecific trait values. Differences in trait values among sites were more strongly related to soil nutrient availability than to variation in light or rainfall. Soil nutrient availability explained a significant amount of variation in site mean trait values for 4 of 15 functional traits. Site mean values of leaf nitrogen and phosphorus increased 37 and 64%, respectively, leaf carbon:nitrogen decreased 38%, and specific leaf area increased 29% with increasing soil nutrient availability. For Geonoma cuneata, the only species occurring at all sites, leaf phosphorus increased 34% and nitrogen:phosphorus decreased 42% with increasing soil nutrients. In addition to among-site variation, most morphological and leaf nutrient traits differed among coexisting species within sites, suggesting these traits may be important for niche differentiation. Hence, a combination of habitat filtering due to turnover in species composition and intraspecific variation along a soil nutrient gradient and site-specific niche differentiation among co-occurring species influences understory palm community structure in this lower montane forest.     

Hydraulic architecture of palms

Abstract

The water transport and storage system of palms is adapted to maintain the primary stem xylem functional over the life of the shoot, and in spite of severe drought. However, our structural information far exceeds our knowledge of vascular function, and these functional considerations bring more questions than answers. The tendency to generalize from limited data on a few species begs the question of how the hydraulic parameters discussed vary between palms with different growth forms and ecologies.     

Post-cranial remains of the miocene lorisidae of East Africa

Post-cranial fragments of Early Miocene lorisids from Kenya and Uganda are described. All these early forms, seemingly impossible to assign to subfamily on the basis of cranial and dental material, had a post-cranial skeleton and presumably locomotor habits as in living members of the Galaginae. Whether or not this new evidence indicates that all the Miocene forms were of that subfamily will depend upon a reassessment of the validity of the two accepted subfamilies. There now seems to be a strong possibility that the lorisine morphological habit has been derived several times from a primitive galagine one. It is much less certain that the two subfamilies represent a single division of a basic stock.     

A small gibbon-like hominoid from the miocene of Uganda.

A new palate from Napak IV in Uganda, dated at 19 million years or older, provides information about the facial morphology of a small Miocene hominoid from East Africa. The fossil resembles small extant gibbons in most features of facial and papatal morphology that are preserved, more so than does its European contemporary, Pliopithecus (Epipliopithecus) vindobonensis. The Ugandan hominoid is most closely related to the small Kenyan hominoids formerly placed in the genus Limnopithecus.     

A new lorisid humerus from the early miocene of Uganda

An early Miocene (18–20 mya) distal humerus from Napak, Uganda, is the only element of the forelimb to be allocated to African Lorisinae. Its loris-like features distinguish it from other East African material that more closely resembles galagids. Tracing the evolution of the lorisoid body has been a difficult task due to the lack of good fossil material. Here, we add a single specimen to this poor record. This humerus helps to document the beginning of extant lorisid locomotor specialization and function.     

Fossil platyrrhine forelimb bones from the early miocene of Argentina

Primate scapula and ulna fragments of uncertain taxonomic affinity (MACN-SC 101) have been recovered from the Pinturas deposits at Arroyo Feo, Santa Cruz, Argentina in association with Santacrucian (Early Miocene) land mammals. Least-squares regression of body weight on surface area and on height of the glenoid fossa of the scapula indicates an estimated mean weight of 3.6 kg for this individual. On the basis of qualitative and several metric features, the fossil scapula and ulna most closely resemble living platyrrhine monkeys. In estimated body weight and relative height of the coronoid process, the fossil is similar to arboreal quadrupeds, such as Cebus apella and Chiropotes. However, spinoglenoid, axilloglenoid, and axillospinal angles, length of lever arm, and length and breadth of the sigmoid notch imply behavioral similarity with larger species that also use their forelimbs extensively in climbing, such as Alouatta and Lagothrix. MACN-SC 101 may represent the incipient divergence of a generalized platyrrhine arboreal quadruped toward a more suspensory form.     

Phytoferritin accumulations in leaves of diseased coconut palms

Summary A study by electron microscopy of coconut palm (Cocos nucifera L.) leaves from trees infected by the Cape St. Paul wilt (Kaincopé) disease of West Africa was carried out. Samples were obtained during the dry season (Dec.–Jan.) and fixed immediately upon removal from the trees in buffered glutaraldehyde. Further processing for electron microscopy was carried out within a week. No virus particles, mycoplasma-like organisms (MLO), fungi, or bacteria were detected in thin sections. Crystalline or paracrystalline accumulations of electron-opaque granules, approximately 5.5–6 nm in diameter, were observed in disintegrated chloroplasts of mesophyll cells. Based upon their morphological characteristics, formation of the slightly curved, fingerprint arrays or linear rows running parallel, and the visualization of electron-opaque cores in unstained preparations, the granules were identified as phytoferritin particles.This work was sponsored in part by National Science Foundation Grant GB-29280 and by a travel grant from the Food and Agriculture Organization of the United Nations.