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A metabolic system composed of nucleic acid enzymes is proposed to have existed prior to the evolution of ribosomal protein synthesis. Vestiges of these nucleic acid enzymes persist in contemporary coenzymes. This proposal rationalizes the fact that many coenzymes are nucleotides or heterocyclic bases which could be derived from nucleotides.
A skull from the Barstovian of South Dakota has typical leptarctine characteristics, including robust zygomatic arches, double sagittal crests, grooves on the lingual side of the lower canines, and bony projections from the tympanic bullae. The robust mandibles and expanded masseteric fossa of this specimen indicate that it had large jaw muscles. Dental morphology and other characters lead us to agree with earlier suggestions that Hypsoparia is a valid genus. The morphology of Hypsoparia suggests that leptarctines were more herbivorous than most other Carnivora. Mustelids vary greatly in size and include 67 extant species in 25 genera. These species occupy many habitats, including fresh and salt water, and all land areas of the world except the West Indies, Madagascar, Sulawesi, Antarctica, and most oceanic islands (Nowak 1999). Qiu and Schmidt-Kittler (1982) considered Leptarctinae to be a subfamily of mustelids including Craterogale (North America, Middle Miocene), Trocharion (Europe, Middle Miocene), Hypsoparia (North America, Upper Miocene), and Leptarctus (North America and Asia, Lower to Upper Miocene). Leptarctus ranges from basal Hemingfordian strata to the Early Hemphillian (Lim 1999). The characters diagnosing Leptarctus as a mustelid include absence of M2, absence of a notch between the paracone and the metacone of the upper carnassial, and a reduced dentition with loss of P1 and p1. Among mustelids, Leptarctus also has many unique characters, including prominent double sagittal crests, a well-developed hypocone on P4, grooved lower canines, heavy zygomatic arches, and bony projections on the tympanic bullae (Lim 1999). Dorr (1954) erected a new genus and species of leptarctine mustelid from the Late Miocene of Montana, USA: Hypsoparia bozemanensis. Qiu and Schmidt-Kittler (1982) confirmed it as a taxon separate from Leptarctus. However, McKenna and Bell (1997) and Baskin (1998) synonymized H. bozemanensis with Leptarctus primus. The new specimen from the Miocene of South Dakota, USA, provides evidence that Hypsoparia is a separate genus from Leptarctus. We can describe this animal as follows: Systematic paleontology: class, Mammalia; order, Carnivora; family, Mustelidae (Fischer von Waldheim 1817); subfamily, Leptarctinae (Gazin 1936); genus Hypsoparia (Dorr 1954). Emended diagnosis: the muzzle short, deep, and wide compared with that of Leptarctus; small, round infraorbital foramen; relatively greater height of zygomatic arch; upper canine with anterior wear; P2 and P3 unicuspid with complete cingula; P4 and M1 longer than wide; labial side longer than lingual side on P4; anterior margin of M1 curving inward; mandibles larger and more robust than in L. primus; mandible deep with two mental foramina located below p2 and p3; masseteric fossa enlarged; m2 longer than wide; m1 with a broadly basined talonid; p3 and p4 with prominent cingula.
We report on a new Mesozoic bird, Longirostravis hani, from the Early Cretaceous Jehol Biota of northeastern China. The new taxon has a long, slender rostrum and mandible, and a small number of rostralmost teeth. Postcranial characters such as a furcular ramus wider ventrally than dorsally, a centrally concave proximal margin of the humeral head, and a minor metacarpal that projects distally more than the major metacarpal, support the placement of Longirostravis within euenantiornithine Enantiornithes, the most diverse clade of Mesozoic birds. The morphology of the skull, however, suggests that Longirostravis had a probing feeding behavior, a specialization previously unknown for Enantiornithes. Indeed, this discovery provides the first evidence in support of the existence of such a foraging behavior among basal lineages of Mesozoic birds.
We report on the oldest European songbird (Passeriformes), from the early Oligocene (30-34 million years ago) of Frauenweiler in Germany. The specimen represents the earliest associated remains of an early Tertiary passerine described so far. It ties the first appearance of Passeriformes in Europe to a minimum age of 30 million years. Passeriform birds are absent in Eocene deposits that yielded abundant remains of small land birds and apparently dispersed into Europe around the Eocene/Oligocene boundary (about 34 million years ago), not at the Oligocene/Miocene boundary (about 24 mya) as hitherto thought. This possibly relates the appearance of songbirds in Europe to a well-known major faunistic break at the Eocene/Oligocene boundary, called the " grande coupure". The Frauenweiler songbird most notably differs from extant Passeriformes in having a larger processus procoracoideus on the coracoid and appears to be outside Eupasseres, the taxon which includes Oscines (all modern European and most Old World songbirds) and Suboscines (most South and Central American songbirds). It shows that there were earlier dispersal events of non-oscine songbirds into Europe before the arrival of Oscines from the Australian continental plate towards the late Oligocene.
During a research cruise in July 1997 in the Gulf of Mexico we discovered a gas hydrate approximately 1 m thick and over 2 m in diameter which had recently breached the sea floor at a depth of 540 m. The hydrate surface visible from the submarine was considerably greater than that of any other reported hydrate. Two distinct color bands of hydrate were present in the same mound, and the entire exposed surface of the hydrate was infested (2500 individuals/m2) with 2 to 4 cm-long worms, since described as a new species, Hesiocaeca methanicola, in the polychaete family Hesionidae (Desbruyères and Toulmond 1998). H. methanicola tissue stable isotope values are consistent with a chemo-autotrophic food source. No evidence of chemo-autotrophic symbionts was detected, but geochemical data support the presence of abundant free living bacteria on the hydrate. The activities of the polychaetes, grazing on the hydrate bacteria and supplying oxygen to their habitats, appears to contribute to the dissolution of hydrates in surface sediments.
Sediments of the Eckfeld maar (Eifel, Germany) bear a well-preserved Eocene fauna and flora. Biostratigraphically, Eckfeld corresponds to the Middle Eocene mammal reference level MP (Mammals Paleogene) 13 of the ELMA (European Land Mammal Age) Geiseltalian. In the maar crater, basalt fragments were drilled, representing explosion crater eruption products. By 40Ar/39Ar dating of the basalt, for the first time a direct numerical calibration mark for an Eocene European mammal locality has been established. The Eckfeld basalt inverse isochron date of 44.3 +/- 0.4 Ma suggests an age for the Geiseltalian/Robiacian boundary at 44 Ma and, together with the 1995 time scale of Berggren et al., a time span ranging from 49 to 44 Ma for the Geiseltalian and from 44 to 37 Ma for the Robiacian, respectively. Additional 40Ar/39Ar dating on a genetically related basalt occurrence close to the maar confirms a period of volcanism of ca. 0.6 m.y. in the Eckfeld area, matching the oldest Eocene volcanic activity of the Hocheifel volcanic field.
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Studies using surface or internal enamel growth indicators in hominids have suggested that crown-formation times were shorter than those in modern man. The crown-formation time in a robust australopithecine premolar tooth was calculated by counting enamel cross-striations, which correspond to daily increments of formation, on a replica of the fractured internal enamel surface of cuspal enamel using scanning electron microscopy. Cervical enamel completion time was estimated using other growth indicators including striae, and using measured and calculated cross-striation repeat intervals, giving a completion time of approx. 2.4 yr. This is much shorter than reported premolar crown formation times in modern man. These findings support the concept of an abbreviated period of dental development, with implications on the duration of the growth period in early hominids.
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Saponified extracts of rock samples colonized by cryptoendolithic microbial communities from the McMurdo Dry Valleys of Southern Victoria Land, Antarctica, were separated into hydrocarbon and fatty acid fractions by silica gel column chromatography. Hydrocarbons and methyl esters of fatty acids were analyzed by capillary gas chromatography-mass spectrometry. Unusually, a suite of long-chain anteiso-alkanes (a-C20 to a-C30) and anteiso-alkanoic acids (a-C20 to a-C30) were detected in many samples, together with straight-chain, branched and/or cyclic and acyclic isoprenoid compounds. These novel compounds are probably derived from unidentified heterotrophic bacteria or symbiotic processes in a unique microbial community in the Antarctic cold desert and suggest the occurrence of a special biosynthetic pathway. Long-chain anteiso-alkanes are probably formed through microbial decarboxylation of corresponding anteiso-alkanoic acids. They may serve as new biomarkers in environmental and geochemical studies.
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Chemical fractions from 4 shale oils including one produced in an above-ground retort (Paraho), 2 produced below ground by in situ method (Occidental and Geokinetics), and 1 produced by a simulated modified in situ process (Livermore), were tested for mutagenicity against Salmonella typhimurium TA98 in the Ames assay system. Their mutagenic activities were compared with 2 other complex materials: a high-boiling coal distillate (The Solvent Refined Coal Process I (SRC II) heavy distillate), and a crude petroleum (Prudhoe Bay). Each material was fractionated by Sephadex LH-20 partition chromatography and by acid-base solvent extraction to provide chemical fractions for bioassay. Mutagenic activity was detected in the coal liquid (and their fractions), but not in the natural crude oil nor in any of its fractions. The basic and tar fractions derived by solvent extraction, and the LH-20 methanol fractions contained most of the mutagenic activity recovered from the unfractionated material. The heavy distillate was approx. 10 times more active in the Ames assay than the most mutagenically active shale oil. The most mutagenically active of the shale oils was about 10 times more active than the least active shale oil.
Skin tumor response in mice to solvent fractions of heavy distillate (HD) from a solvent-refined coal (SRC-II) process indicated that the basic tar and neutral tar were the most carcinogenically potent fractions. Assays of another SRC-II coal liquid that had been fractionally distilled indicated that the carcinogenicity of this material for mouse skin is due to that portion boiling above 371 degrees C (700 degrees F), and that the carcinogenic potency of the material increased with boiling point. Samples of the 399-427 degrees C (750-800 degrees F) distillate were nitrosated to destroy primary aromatic amines and were chemically fractionated to assess the carcinogenicity of chemical class fractions of these complex mixtures. Data from these assays indicated that neutral polycyclic aromatic hydrocarbons (PAH) and nitrogen-containing polycyclic aromatic compounds (NPAC) both contribute to the carcinogenicity of this distillate.
Sequence data, even if only marginally significant, and evolutionary arguments suggest that a similarity may exist between class II aminoacyl-tRNA synthetases and proteins involved in the nonribosomal biosynthesis of peptide antibiotics, and more in general, those belonging to the family of adenylate-forming enzymes. If correct, this hypothesis of homology may imply that the first peptide syntheses might have occurred on phosphopantetheine molecules in a thioester world and/or on a variant of the coenzyme A (CoA) in an RNA world. Therefore, peptide synthesis probably evolved on tRNA-like molecules from the CoA (or a variant CoA molecule) that had the potential for nucleotide extension, that made possible the evolution to the current mechanism of protein synthesis. Our hypothesis on the existence of such homology implies that a series of evolutionary steps such as the existence of a primitive catalytic domain with poor substrate specificity towards both (amino acids + ATP + pre-CoA (and/or CoA)) and (amino acids + ATP + tRNA-like) molecules may have occurred. Therefore, the pre-CoA (and/or CoA) and the tRNA-like molecules were able to use this enzyme ambiguity for a certain period, thus giving weight to the scheme of evolutionary transitions mentioned above.
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