Search PubMed⌕ Search

Biomedical subjects

E L Simons

Publications and source records attributed to E L Simons.

At least 19 recordsLinked to original sources
PubMed1992

Diversity in the early tertiary anthropoidean radiation in Africa.

Between 1987 and 1991 recent field seasons in the Fayum Depression of Egypt have yielded five species and genera of primates that were earlier unknown. Three of these species and genera are described below. All these genera and species are known only from Fayum site L-41, which has been dated as of late Eocene age. In the Fayum, these 5 species from L-41 are added to 3 kinds of prosimians (1 species formally described) and 11 earlier named species of Anthropoidea. When certain undescribed species are added, the total of known Fayum primate species comes to 21, belonging to at least 10 genera, genera that, in turn, could belong to as many as seven families. This arguably represents more taxonomic diversity of primates, especially higher primates, than has been demonstrated before in one so spatially and temporally limited area. These facts argue that an important, perhaps primary, radiation of anthropoideans took place in the African Eocene.

Animals↗
PubMed1991

Phylogenetic and functional affinities of Babakotia (primates), a fossil lemur from northern Madagascar.

Recent paleontological expeditions to the Ankarana range of northern Madagascar have recovered the partial remains of four individuals of a newly recognized extinct lemur, Babakotia radofilai. Craniodental and postcranial material serve to identify Babakotia as a member of the palaeopropithecids (also including the extinct genera Palaeopropithecus, Archaeoindris, and Mesopropithecus). Living indrids form the sister group to this fossil clade. The postcranial anatomy indicates that Babakotia was a medium-sized (approximately 15 kg) indroid whose inferred positional behaviors were primarily slow climbing and hanging. Although it is probable that a leaping component typified the ancestral positional repertoire of all Malagasy lemurs, the mosaic nature of the locomotor skeleton of Babakotia further suggests that vertical climbing and hang-feeding rather than ricochetal leaping were primitive for indrids and palaeopropithecids and that the dramatic saltatory adaptations of the living indrids postdate the divergence of these two lineages.

Animals↗
PubMed1991

Similarities in Aegyptopithecus and Afropithecus facial morphology.

Recently discovered cranial fossils from the Oligocene deposits of the Fayum depression in Egypt provide many details of the facial morphology of Aegyptopithecus zeuxis. Similar features are found in the Miocene hominoid Afropithecus turkanensis. Their presence is the first good evidence of a strong phenetic link between the Oligocene and Miocene hominoids of Africa. A comparison of trait lists emphasizes the similarities of the two fossil species, and leads us to conclude that the two fossil genera share many primitive facial features. In addition, we studied facial morphology using finite-element scaling analysis and found that the two genera show similarities in morphological integration, or the way in which biological landmarks relate to one another in three dimensions to define the form of the organism. Size differences between the two genera are much greater than the relatively minor shape differences. Analysis of variability in landmark location among the four Aegyptopithecus specimens indicates that variability within the sample is not different from that found within two samples of modern macaques. We propose that the shape differences found among the four Aegyptopithecus specimens simply reflect individual variation in facial characteristics, and that the similarities in facial morphology between Aegyptopithecus and Afropithecus probably represent a complex of primitive facial features retained over millions of years.

Animals↗
PubMed1991

Hematology, serum chemistry values, and rectal temperatures of adult greater galagos (Galago garnetti and G. crassicaudatus).

Hematological and serum chemistry values, as well as rectal temperatures, were obtained from greater galagos (Galago garnettii and G. crassicaudatus), in order to establish normative values. No species or sex differences were found for four hematological parameters and 15 serum chemistry parameters. Species differences were seen in phosphate, magnesium, cholesterol, alkaline phosphate, G-glutamyl transferase, mean corpuscular volume and leucocyte, neutrophil, and lymphocyte number. Significant sex differences were observed in glucose, hemoglobin, and hematocrit values. Species and sex differences were seen in chloride and erythrocyte number.

Animals↗
PubMed1990

Vectors for constructing kan gene fusions: direct selection of mutations affecting IS10 gene expression.

We describe several vectors for constructing translational fusions to the kan gene of Tn5. Fusions are constructed in vitro using multi-copy vectors containing unique cloning sites situated between upstream transcriptional terminators and a downstream kan gene lacking transcriptional and translational start signals. Multi-copy fusions can be converted to single-copy chromosomal fusions by in vivo recombination with specific phage lambda vectors and vice versa. We find that kan fusions are often more suitable than lacZ fusions for the direct selection of mutations that increase fusion expression. These vectors were developed for isolating mutations that increase IS10 transposase expression; we describe strategies used to isolate such mutations, which map to IS10 or the Escherichia coli himA, himD(hip), dam or infC genes.

Bacteriophage lambda↗
PubMed1990

Discovery of the oldest known anthropoidean skull from the paleogene of Egypt.

A group of primate fossils newly discovered in the Fayum badlands of Egypt is probably of Eocene age. The site is much older than the localities of previously known Egyptian early Tertiary primates. These finds include a crushed cranium that is the oldest skull found to date of a higher primate. This skull shows four characteristics of higher primates: a catarrhine dental formula, an ectotympanic at the rim of the auditory bulla, a fused frontal bone, and postorbital closure. Details of tooth structure (premolars and molars) and a possibly unfused mandibular symphysis resemble these parts in certain Eocene prosimians.

Animals↗
PubMed1990

The IS10 transposase mRNA is destabilized during antisense RNA control.

RNA stability is an important component of gene expression, and antisense RNAs have been proposed to alter target RNA stability. We show here that the IS10 transposase mRNA, RNA-IN, is rendered unstable during control by the IS10 antisense RNA, RNA-OUT. Destabilization requires RNA-OUT/RNA-IN pairing and ribonuclease III cleavage. Independent of such cleavage, RNA-OUT is rendered unstable through disruption of its secondary structure. Pairing has no other obvious effects on RNA-IN transcription or stability. Nevertheless, RNA-IN destabilization is not required for antisense control in vivo. In the accompanying paper [Ma,C. and Simons, R.W. (1990) EMBO J., 9, 1267-1274 we show that pairing blocks ribosome binding to RNA-IN. Were it not for control at this level, destabilization would play a more prominent role.

Base Sequence↗
PubMed1990

Taxeopody in the carpus and tarsus of Oligocene Pliohyracidae (Mammalia: Hyracoidea) and the phyletic position of hyraxes.

Recent hyracoids and elephants share a taxeopode arrangement of tarsal and carpal bones, a condition in which bones are aligned with minimal interlocking between adjacent elements. Taxeopody has often been interpreted as a synapomorphy reflecting a close phyletic link between Hyracoidea and Proboscidea, but recently it has been suggested [Fischer, M. S. (1986) Cour. Forschungsinst. Senckenberg 84, 1-132] that hyracoid taxeopody is an independent acquisition resulting from selection favoring increased midcarpal and midtarsal rotation and that Hyracoidea is actually allied with Perissodactyla. As a test of this hypothesis, isolated carpal and tarsal bones of primitive Oligocene hyracoids from the Fayum, Egypt, have been examined to determine whether these indicate a taxeopode or diplarthral carpus and tarsus. Four complete astragali from the Fayum, representing at least three taxa, show a single, slightly convex articular surface on the head for articulation with the navicular and lack a facet for the cuboid. Two complete magna representing two species have a single proximal facet for articulation with the lunar, and they lack a facet for the scaphoid. Thus, both the carpus and tarsus of Fayum hyracoids are taxeopode. Taxeopody in hyracoids cannot be attributed to selection for carpal and tarsal rotation in climbers because the Oligocene, Miocene, and Recent species show great diversity in body size and probably locomotor specializations, despite relative uniformity of structure in the carpus and tarsus. The shared taxeopody of hyracoids and proboscideans, along with other osteological characters and similarities in hemoglobin, eye lens proteins, and other molecules, all suggest that Hyracoidea belongs within Paenungulata.

Animals↗
PubMed1989

Human origins.

New discoveries combine to indicate that all the major steps in human evolution took place in Africa. Skeletal analysis of oldest human forbears around 3 million years ago reveal many anatomical similarities to African Great Apes. These and biochemical resemblances indicate a common ancestry for humans and apes, perhaps only a few million years earlier. Enlarged knowledge through recent recovery of skeletons of several successive stages in the line leading to modern peoples shows that many attributes or skills by which we define humanity arose much more recently in time than heretofore believed.

Africa↗
PubMed1989

Tarsius delta- and beta-globin genes: conversions, evolution, and systematic implications.

Comparisons between duplicated genes have shown that gene conversions play an important role in the evolution of multigene families. Previous comparisons have documented in the recently duplicated gamma-fetal globin genes of catarrhine primates, over 15 separate conversions affecting extensive stretches of coding and noncoding sequences. In the present study, delta- and beta- globin genes from a lower primate Tarsius syrichta, and the delta-globin gene of the Asian great ape, Pongo pygmaeus, have been isolated and sequenced. Comparisons of these sequences with other primate delta and beta sequences confirmed a previously reported conversion in an anthropoid ancestor and revealed additional conversions in basal primate, stem haplorhine, tarsier, and early lemur lineages. Conversions found between primate delta- and beta-globin genes contrast with those found in the gamma-genes in that delta-beta conversions appear much less frequently and are more restricted to regions conserved by selection (i.e. coding and 5'-regulatory sequences). These differences indicate that soon after a duplication occurs, conversions can be quite frequent and encompass extensive portions of the duplicated region. With time, sequence differences accumulate, particularly in noncoding regions, and limit both the frequency and size of the conversions. Sequences conserved by selection accumulate differences more slowly and are therefore subject to gene conversions for a longer period of time. Both unconverted and converted sequences were consistent in supporting the placement of tarsier with anthropoids.

Animals↗
PubMed1989

Cranial morphology of Aegyptopithecus and Tarsius and the question of the tarsier-anthropoidean clade.

New crania of the Oligocene anthropoidean Aegyptopithecus provide a test of the hypothesized tarsier-anthropoidean clade. Three cranial characters shared by Tarsius and some modern anthropoideans (apical interorbital septum, postorbital septum, "perbullar" carotid pathway) were examined. 1) An apical interorbital septum is absent in Aegyptopithecus. A septum does occur in Galago senegalensis (Lorisidae) and Microcebus murinus (Cheirogaleidae), so the presence of a septum is not strong evidence favoring a tarsiiform-anthropoidean clade. 2) In Aegyptopithecus and other anthropoideans, the postorbital septum is formed mainly by a periorbital flange of the zygomatic that extends medially from the lateral orbital margin onto or near the braincase. The postorbital plate of Tarsius is formed by frontal and alisphenoid flanges that extend laterally from the braincase to the zygomatic's frontal process, which is not broader than the postorbital bars of other prosimians. Periorbital flanges evolved in Tarsius for support or protection of the enormous eyes, as suggested by the occurrence of maxillary and frontal flanges that cup portions of the eye but do not separate it from temporal muscles. 3) The internal carotid artery of Aegyptopithecus enters the bulla posteriorly and crosses the anteroventral part of the promontorium. The tympanic cavity was probably separated from the anteromedial cavity by a septum stretching from the carotid channel to the ventrolateral bullar wall. In Tarsius, the carotid pathway is prepromontorial, and a septum stretches from the carotid channel to the posteromedial bullar wall. Quantitative analyses indicate that anterior carotid position has evolved because of erect head posture. The cranium of Oligocene anthropoideans thus provides no support for the hypothesized tarsier-anthropoidean clade.

Animals↗
PubMed1989

Description of two genera and species of late Eocene Anthropoidea from Egypt.

In 1987 and 1988 fossils of two previously unknown genera and species of Egyptian early Tertiary Anthropoidea were discovered in the Fayum Depression of Egypt. These are much older than all other Fayum, Oligocene primates and are believed to be Eocene in age. These genera, here named Catopithecus and Proteopithecus, come from a new Fayum site, L-41, and resemble Oligopithecus from the Jebel Qatrani Formation (lower sequence) at quarry E. They are here placed with the latter in a subfamily, Oligopithecinae, that is ranked in the Propliopithecidae. The level of L-41 is separated from quarry E by at least one major unconformity and 47 m of section. Only a maxilla of Proteopithecus is known. Its molars and premolars resemble those of later Fayum Propliopithecus and Aegyptopithecus and do not resemble those of Apidium and Parapithecus, all of which come from the Jebel Qatrani Formation, upper sequence. The type specimen of Catopithecus confirms a lower dental formula of 2-1-2-3, as in Catarrhini. These species appear to be the oldest primates undoubtedly related to humans. Their dental anatomy points to a derivation of Anthropoidea from Eocene adapids.

Animals↗
PubMed1988

Analysis of the promoters and transcripts involved in IS10 anti-sense RNA control.

Genetic analysis of eleven mutations affecting the IS10 promoters, pIN and pOUT, involved in anti-sense RNA control of transposase gene expression, and characterization of the transcripts, reveal that: (i) The transposase message (RNA-IN) and the anti-sense RNA (RNA-OUT) have been unambiguously identified in vivo. (ii) Five mutations affect pIN activity, and establish that pIN is the only IS10 promoter transcribing the tnp gene, and the only such IS10 promoter that responds to DNA-adenine methylation. (iii) Six mutations alter pOUT activity, and establish that pOUT is the only IS10 promoter specifying the anti-sense RNA-OUT. (iv) The latter, however, need not be so: heterologous promoters, if properly positioned, can also specify active anti-sense RNAs. (v) These heterologously promoted anti-sense RNAs are processed to species closely resembling native RNA-OUT.

Bacteriophage lambda↗
PubMed1988

New specimens of Oligopithecus savagei, early Oligocene primate from the Fayum, Egypt.

New specimens of the early Oligocene anthropoidean, Oligopithecus savagei, from the Fayum, Egypt, include unworn specimens of lower teeth plus the first known upper molar, premolar, and incisor. These finds confirm the anthropoidean status of Oligopithecus. Comparisons with other Fayum taxa suggest that Oligopithecus is more closely related to Propliopithecidae than to Parapithecidae. Dental similarities between Oligopithecus and early platyrrhines are probably primitive retentions that do not support the hypothesis of an Oligocene trans-Atlantic crossing by primates. Among prosimians, the upper teeth of Oligopithecus very closely resemble those of Protoadapis and allied forms (Europolemur, Mahgarita, Periconodon, Hoanghonius), but differ substantially from other prosimian taxa. Most of the dental and osteological resemblances between Oligopithecus and the Protoadapis group are derived features, thus favoring the hypothesis that Oligopithecus and other Anthropoidea are descended from Adapidae.

Animals↗
PubMed1987

A new species of Propliopithecus from the Fayum, Egypt.

Propliopithecus ankeli is described as a new species of hominoid from the early Oligocene of Egypt. The new species occurs at a stratigraphic level 80 m below quarries yielding P. chirobates and Aegyptopithecus zeuxis. P. ankeli differs from other species of the genus in its large size, relatively robust canines, larger and proportionally broader premolars, and M1 that has as great or greater mesiodistal length than M2. Thus, P. ankeli is characterized by increased relative size and robustness of the antemolar dentition, which contrasts with the pattern observed in the Fayum's other large hominoid, A. zeuxis. P. ankeli probably represents a lineage not ancestral to other Fayum hominoids. Discovery of this new species emphasizes the diversity of anthropoid primates that had already evolved by the early Oligocene.

Animals↗