Geologists and biologists in palaeontology

Whereas zoopalaeontology is one-sidedly a geological science, palaeobotany is predominantly a science cultivated by biologists. Under the influence of increased application as a stratigraphical and palaeoenvironmentological tool in exploration geology as well as in pure geology, palaeopalynology is also becoming more and more a one-sidedly orientated field of science.     

Proteins, exons and molecular evolution

The discovery of the eukaryotic gene structure has prompted research into the potential relationship between protein structure and function and the corresponding exon/intron patterns. The exon shuffling hypothesis put forward by Gilbert and Blake suggests the encodement of structural and functional protein elements by exons which can recombine to create novel proteins. This provides an explanation for the relatively rapid evolution of proteins from a few primordial molecules. As the number of gene and protein structures increases, evidence of exon shuffling is becoming more apparent and examples are presented both from modern multi-domain proteins and ancient proteins. Recent work into the chemical properties and catalytic functions of RNA have led to hypotheses based upon the early existence of RNA. These theories suggest that the split gene structure originated in the primordial soup as a result of random RNA synthesis. Stable regions of RNA, or exons, were utilised as primitive enzymes. In response to selective pressures for information storage, the activity was directly transferred from the RNA enzymes or ribozymes, to proteins. These short polypeptides fused together to create larger proteins with a wide range of functions. Recent research into RNA processing and exon size, discussed in this review, provides a clearer insight into the evolutionary development of the gene and protein structure.     

Ultrasonic probes in palaeontology

The Ultrasonic Probe was specially designed, patented and made by the Simms Group Research and Development Limited, London, during Dr E. I. White's final year of office as Keeper of Palaeontology at the British Museum (Natural History). It utilizes the same principles as those of ultrasonic tanks (Firth, 1960; Organ, 1959). The probe tip vibrates at a very high frequency and causes cavitation in the cleaning fluid, which breaks up porous and incompetent matrices. Its small diameter and area of activity make it invaluable when only parts of a specimen require cleaning, or when specimens are too big for the tank.     

Proteins of the kidney microvillar membrane. Enzymic and molecular properties of aminopeptidase W.

Aminopeptidase W is a newly discovered enzyme of the renal and intestinal brush borders, having been first isolated as a 130 kDa glycoprotein recognized by a monoclonal antibody [Gee & Kenny (1985) Biochem. J. 230, 753-764]. It is particularly effective in the hydrolysis of dipeptides, Glu-Trp (Km 0.57 mM; kcat. 6770 min-1) being a favoured substrate. Dipeptides with tryptophan, phenylalanine or tyrosine in the P1 position were rapidly hydrolysed, but the requirements in respect of the P1 residue were not stringent. The activity of aminopeptidase W is markedly influenced by ionic conditions. The highest activity was observed in 100 mM-Tris/HCl, pH 8; phosphate ions were strongly inhibitory. Activity was also greatly affected by bivalent metal ions, and the magnitude and direction of the effects depended on the nature of the buffer anions and on pH. The most effective inhibitors were amastatin and bestatin. Some thiols also inhibited, but other chelating agents, EDTA and 1,10-phenanthroline, had no effect over the concentration range 1-10 mM. Other group-specific inhibitors, for cysteine, serine or aspartic peptidases, were also ineffective. Some molecular properties were studied. Deglycosylation by treatment with N-glycanase diminished the apparent subunit Mr from 130,000 to 90,000. The enzyme contained zinc, 1.2 atoms/subunit, and in spite of the atypical properties of this enzyme in respect of chelating agents, a zinc-catalysed mechanism is the most probable. Its roles in digestion and in renal function are not yet clear.     

Biomineral electron backscatter diffraction for palaeontology

Electron backscatter diffraction (EBSD) originated in materials science and has transferred to biomineral research providing insight into fossil and modern biominerals. An electron microscopy technique, EBSD requires a fine polished sample surface where the electron beam diffracts in the first few lattice layers, identifying mineral, polymorph and crystallographic orientation. The technique is particularly well suited for the analysis of modern and fossil calcium carbonate biominerals, where it provides key insight into biological control of mineral formation such as in molluscs and brachiopods. EBSD readily identifies original and secondary mineralogy, which helps to inform our understanding of biomineral evolution such as the identification of original aragonite in Silurian trimerellid brachiopods. As a technique to identify and thus avoid the inclusion of secondary minerals in proxy organisms such as corals, EBSD can be used to ensure accuracy of palaeoproxy data. Even when fossil systems have no modern equivalents, EBSD can provide key data to determine functional mechanisms such as in the lenses of schizochroal eyes of phacopine trilobites. These few examples illustrate that EBSD is proving to be a valuable component of the palaeontology toolkit.     

Origin and early evolution of the vertebrates: new insights from advances in molecular biology, anatomy, and palaeontology

Recent advances in molecular biology and microanatomy have supported homologies of body parts between vertebrates and extant invertebrate chordates, thus providing insights into the body plan of the proximate ancestor of the vertebrates. For example, this ancestor probably had a relatively complex brain and a precursor of definitive neural crest. Additional insights into early vertebrate evolution have come from recent discoveries of Lower Cambrian soft body fossils of Haikouichthys and Myllokunmingia (almost certainly vertebrates, possibly related to modern lampreys) and Yunnanozoon and Haikouella (evidently stem-group vertebrates). The earliest vertebrates had an unequivocally marine origin, probably evolved mineralised pharyngeal denticles before the dermal skeleton, and evidently utilised elastic recoil of the visceral arch skeleton for suction feeding. Moreover, the new data emphasise that the advent of definitive neural crest was supremely important for the evolutionary origin of the vertebrates.     

The application of Correspondence Analysis in palaeontology

Correspondence analysis (CA) is frequently used in the interpretation of palaeontological data, but little is known about the minimum requirements for a result to be valid. Far from being a fundamental mathematical study of CA, this paper aims to present a tool, which may serve to evaluate results obtained in (palaeontological) praxis. We created matrices of random data, grouped by matrix size and varying percentages of zero cells. Each matrix was submitted to CA. Per matrix group the minimum, mean and maximum percentages of total inertia were calculated for the first four axes. We compared these results with several real cases in vertebrate paleontology. Valid conclusions based on CA can only be drawn on percentages that are considerably higher than the axis percentages obtained from random matrices.     

Allometric scaling in palaeontology: A critical survey

Allometric scaling models, used to describe morphological and functional relationships between two sets of observations, are examined both in concept and in application. This paper focuses on the underlying assumptions and statistics of the methods most frequently used: linear regression, principal axis and standard major axis analysis. It is shown that the standard major axis (SMA) is the most appropriate bivariate linear model in palaeonotological research. Differences among the models discussed are illustrated by a morphometric analysis of dental dimensions in australopithecines.     

Molecular palaeontology: New life for old molecules

It is perhaps not generally realized that rocks contain at least J0 000 times more organic material than the present day global biomass. More importantly, it has now been demonstrated that some diagnostic molecular structures survive in recognizable form for many millions of years. The development of powerful new techniques for the recovery, purification and identification of organic compounds has provided a major stimulus to the study of these molecular fossils.