Иван Ефремов - Taphonomy: new branch of paleontology
At the present time paleontology has already passed through the stage during which primary actual data are gathered. The former iconographic papers are replaced by a growing number of articles developing more or less the evolutionary theory based on paleontological data. The phylogeny of different groups of organisms, the interpretation of the biology of forms now extinct the influence of outer surroundings on the organism in process of time, paleozoogeography. All these problems are commonly at least touched upon in every considerable paleontological research. For the better development of this "theoretic" part of paleontology, it is subdivided into different subparts: Biostratigraphy, paleoecology (paleobiology), paleopathology, and others; each subpart unites a series of different problems, not a single one of which can be easily solved.
The greatest difficulty in all paleontological reconstructions is the desultory and incomplete character of the material and casuality of its preservation in the rock. Therefore, Darwin’s theory of the incompleteness of the geological chronicle is of special importance in paleontology. And this is still so, in spite of the voluminous data which have been gathered since Darwin’s time.
It is to be exceedingly regretted that paleontologists do not take into consideration this incompleteness of the geological chronicle; that there have hardly been any attempts to correlate paleontological data with the animal world actually existing in the past. Many phylogenetic theories and general laws have been formed on the basis of data obtained on fossils as if these latter presented a true and complete image of animal life during past geological eras.
All that has just been said is of special importance for the ancient faunas. The older the age of the geological formation is, the scarcer is the actual material, and there are more and more ways in which it can be interpreted. All the general conceptions of ancient faunas and ancient paleozoogeography are very primitive and not convincing. Our knowledge is still more vague about such groups of forms, "faunas," as those which have been found in conditions, showing that they were embedded in alien surroundings and in tanatoceonoses.
The study of sediments which contain some type of fossilized bioccenoses of stationary marine fauna, together with the study of the distribution of different forms in different facies, and in space, such research brings good results for estimating the outer conditions (physico-geographical and biotic ones), and their influence on the fauna as a whole, and on separate forms.
Such methods of paleoecological analysis become hardly possible when a fauna is found in casual groups, tanatoceonoses, and not at the place where it existed when living. Still, this problem is a much more simple one for marine organisms, because the transference of the remains along the bottom of the sea is generally insignificant Moreover, the areas where a fauna is found when alive are nearly always the areas of sedimentation, and the surrounding conditions are simply variations of one large bionomical factor. Thus, the study of sediments containing abundant faunas, and the study of the variations in the sediments along large areas and during great intervals of time leads to perceptible results.
But when we turn to the terrestrial faunas we come upon very different conditions. All the localities where these faunas are found are tanatocoenoses which have been formed in alien vital surroundings. The areas occupied by these faunas when alive are generally regions of wash-out. The fossilized remains of land-organisms are found on very small disconnected areas, so that the incompleteness of the geological chronicle for the land-faunas is much greater than for that of the sea.
Meanwhile, the terrestrial organisms, both insects and vertebrates, are highly organized, having passed through a long period of evolutional development. Because of this land-organisms are of special interest as material for establishing evolutionary laws; but it is just for this group that the precision of theoretical deduction is not great, because the actual material is very incomplete.
The chief and most precise method of paleontology, detailed morphological study followed by comparative analysis, can be of use only for objects which have been well preserved. But it cannot be of any use at all for reconstructing that pan of the fauna, which has not reached us even partly. The paleobiological study of ancient land-forms also does not give any precise notion of the life of the fauna; the remains are preserved in tanatoccenoses which bear no part in the life-surroundings of the fauna; so the analysis of individual adaptive deviation is not sufficiently authentic.
All the other known methods of paleoecological research are also, for the same reason, quite helpless in the study of terrestrial forms. Taking all this into consideration, it will be easy to surmise why it chanced that the first paleontologists who found it indispensable to work from a new point of view, were those who studied the fossilized remains of the vertebrates. This new outlook created a basis for a critical examination of the place which paleontological data must occupy in the tangible animal-life of the past.
It is evident that, apart from the study of fossilized objects in itself, there is another way to the knowledge of the animal world of the past eras, i.e., the study of the conditions in which paleontological records have been preserved, a comparative study of the localities where the remains have been found.
Many of the works published recently contain chapters devoted to the analysis of the conditions under which remains of the terrestrial animals are found in the rocks, fossilization and biostratonomy (Walther, Deecke, Abel, Weigelt, Wepfer, etc.). I.e., an analysis of the processes of embedding. To be able to study comparatively the gathered data it became necessary to study the contemporary processes of embedding. After a series of short articles by different authors (Besser, Braun, Zelizko, Hoernes, Moos, Richter, and others) devoted to separate observations on the destruction of recent animals and the formation of accumulations of their remains. In 1927 there was published Weigelt’s book devoted specially to the problem of the finding of remains of vertebrates in natural surroundings and their paleobiological significance.
The author has gathered together a great deal of data. But the main purpose of this work is the explanation of the causes of death of animals, based on the position of their remains at the time when they were embedded; so, for all that the author has disclosed many general laws, the general problems of embedding of animal remains have not been formulated. The data were discussed only from the point of view of how such study could help forward paleobiology.
Already in the following year (1928) Richter separated the study of contemporary embedding from paleobiology and named this new branch of science "actuopaleontology." The author formulated it thus: " Actuopaleontology is the science of the way paleontological documents are at present formed to be afterwards preserved as fossils."
In his work Richter gave a detailed analysis of the problems and methods of paleobiology and the new actuopaleontology. The author considers that the following three groups of problems are embraced by actuopaleontology:
(1) The science of life-marks (Lebensspuren of Abel), which can be named ichnology;
(2) The science of the destruction of animals and of the embedding of their remains. It can be subdivided into, (a) tanatology, the causes of death and its immediate results, (b) comidology, the transportation of animal remains, (c) biostratonomy (Weigclt), the science of embedding and (d) necrology, the decay of animal remains down to diagenesis.
(3) The science of biofacies. This comprises such different parts of ecology (in the strict sense of the word) as bionomy (of Walther) and morphonomy; they are analyzed from the point of view so important for the paleontologist, the areal differences of life as a reaction to the outer surroundings.
For all that actuopaleontology is subdivided into many branches and embraces many different parts of zoology (botany), it studies only the contemporary conditions of embedding of organic remains. Actuopaleontology on the one hand studies the problem of embedding only from the narrow point of view of explaining individual laws, but on the other hand, the science of biofacies has to combat very wide problems which by far exceed, both as to methods and theme, the actual possibilities of actuopaleontology.
Actuopaleontology by no means exhausts in full the problems of the processes of embedding, as it does not study this problem comparatively during the geological history, but separates the conditions of the present from those of the past. Besides this, the name "actuopaleontology" is badly chosen, being cumbrous and without any meaning when translated from Greek.
In 1934 the author of this article published a short analysis of the reasons why transitional forms arc not included into the geological chronicle; and in 1936 — a short outline of the problems that must be studied regarding the process of embedding of ancient terrestrial vertebrates. The new branch of paleontology is outlined by joining together all the different attempts of analyzing the processes of embedding. The development of this new science has become imperative.
The chief problem of this branch of science is the study of the transition (in all its details) of animal remains from the biosphere into the lithosphere, i.e., the study of a process in the upshot of of which the organisms pass out of the different parts of the biosphere and, being fossilized, become part of the lithosphere.
The passage from the biosphere into the lithosphere occurs as a result of many interlaced geological and biological phenomena. That is why, when this process is analyzed, the geological phenomena must be studied in the same measure as the biological ones.
In the indissoluble unity of geological-biological analysis lies the key to the following most important problems of paleontology, which cannot be determined by the usual methods.
(1) As we go down into the ages we find that the number of forms that arc preserved out of the general mass gets less and less. The cause thereof is the general denudation of continents, the sinking of great areas of the Earth’s crust, below the level of the sea, or under masses of less ancient sediments, the metamorphism of the rocks, and, lastly, the small degree in which large areas of the globe are yet investigated. In what measure that part of the fossil animal world that is known to us for each given space of time tallies with the real living fauna of that period, to what extent is our notion of the geographical localization, centers of development, and expansion of the ancient faunas, casual, is our knowledge of the climate which is characteristic for definite groups of forms in the area within which they lived, correct, these are the main problems which must be solved in the general part of the work.
(2) Each complex of land-forms found in one locality, and called by us a "fauna," is in truth but an accidental accumulation of animal remains. The formation of each locality depends on many causes, and, firstly, on the coincidence in a given place of a concentration of animal remains with geological conditions favorable to the conservation of these remains.
The concentration of animal remains depends on the number of species of that, or other forms, the rapidity with which they perished, or the length of time during which the carcasses of the animals were concentrating in a given place. Because of this it is the more numerous species which are more often embedded in the site, where the conditions are favorable for the conservation and fossilization of the remains. So, nearly every bed of fossilized remains is only a selection (and an accidental one) which does not reflect the real composition of the fauna at the place of its formation.
The processes which form the sediments are also favorable to selection in embedding. The animal remains are located mechanically in accordance with the strength of the flow. The smaller remains are carried along farther than the large ones; so, in accordance with the place which the given locality has in the flow, we can meet one containing only large or only small forms.
Why different forms are embedded in this or that locality depends on the kind of their food, the character of their adaptation, and its relation to the general physico-geographical features of the region where the conditions of sedimentation are favorable for embedding.
In this short outline it is, of course, impossible to enumerate all the causes of "selection," and incompleteness in embedding. For example, the classical localities of Late Carbonic amphibia, Stegocephalians, in Bohemia, Saxony, Ireland, and Canada can be indicated. Here are found in great numbers in argillaceous layers in the coal series small Stegocephalians, chiefly larval specimens. For a long time this fauna was taken for the true terrestrial Carbonic fauna, showing a definite phase in the development of the land vertebrates. Therefore, the subsequent findings in older rocks of large and highly organized Stegocephalia (lower Coal Measures, England), or of a diverse and abundant reptilian fauna in rocks but in a slight degree younger (U. S. A.), were very amazing.
Meanwhile, from the point of view of the tenet of embedding, all the localities of Late Carbonic Stegocephalians just described represented pools or small lakes located in marshy forests. These pools swarmed with larvae, or young Stegocephalians, so that later, when the pools were turned into beds of fossilized remains, they were found to be filled with a singular fauna where young species predominated and which contained some small predacious forms which fed upon the youngest larvae. These latter, having no bony skeletons, have been but rarely preserved.
Another example can be found in the well-known localities of the Permian fauna of Pareiasaurians on the Little North Dvina River. Near the largest lens, "Sokolky," is found the lens "Zavrajie." Here have been found the remains of Pareiasaurians (Scutosaurus) with greatly thickened bones. In the chief lens, "Sokolky," is found a large accumulation of Pareiasaurians (Scutosaurus) with normal skeletons, whereas in the tens "Zavrajie" we have undoubtedly a selected embedding of specimens with thickened bones. If the lens "Zavrajie" had been known before the lens "Sokolky" was discovered, and not the other way, as actually happened, the exceptional fauna found there should have been considered typical, and our idea of the Pareiasaurian fauna of the U. S. S. R. should have been initially erroneous.
A great number of such examples of the findings of terrestrial vertebrates are known. They all show to what poor extent the forms found in a given locality reflect the fauna which actually existed there.
(3) In a great number of localities containing land vertebrates, we are met by an apparently unexpected appearance of great masses of bony remains. The roof and the bed-rock of the layer containing animal remains are formed by rocks similar to the layer, but of much greater thickness. These latter rocks generally do not contain any organic remains.
All the numerous so-called "faunas" of ancient vertebrates appear, it would seem quite suddenly, without any "roots" in the underlying rocks. The existence of such localities is generally explained by the swift destruction of large masses of animals, by their sudden migration into the region or by the influence of catastrophic changings in the outer surroundings. Nevertheless, we do not generally meet in dumb series with conditions suitable for embedding, although the fauna has lived for a long period in this region. Much more rarely are found real "death-fields" caused by anastrophical changings in the outer surroundings of the animals.
The solution of the problem of the character of physicogeographical alterations and of the reasons why large accumulations of animal remains are formed, is of great importance for understanding the processes of embedding.
(4) The fragmentary character of the findings of accidental animal complexes explains the loss of prospect into time. Synchronous complexes of animal forms found in different localities and, because of strong differences in embedding conditions, different one from another, have often been taken for different faunas. Sometimes the same form is found in different localities; in one case with a background of primitive forms, and in the other, of forms of a later appearance. This gives occasion to call such a form a "stable" one in the run of time.
On the other hand, forms of different age, grooped into large systematical complexes with a common age definition (for example "Permian") on a morphological basis, seem to shorten the period of evolution, to augment the number of forms which have reached us from a given space of geological time. In reality, if we distribute, for example, all the Permian forms of terrestrial faunas known to us along the run of time represented by the 40 million years of the Permian era, the seeming diversity and numerousness of the forms known to us shall appear essentially other than now. So we see that the problem of dated detailed coordination of the faunas and the gathering of exact data the whole world over during short periods of time is also one of the problems solved by studying the processes of embedding.
The work of solving the above mentioned problems can be divided into two parts.
The first part, the study of geological processes of the transition of animal remains from the biosphere into the lithosphere, and in the first place, the detailed study of the localities where a terrestrial fauna is found. Up to the present these problems have not been studied, notwithstanding their significance.
The second part, the study of the laws by which are governed contemporary embedding processes of animal remains (in part Richter’s actuopaleontology).
The chief work of the first part is as follows:
1. Biostratonomy of the localities. The study of the spatial distribution of animal remains and their distribution relatively to the planes of stratification, denudation, cross-bedding, relative to shingle and dififerent mineralogical fractions. The construction of biostratonomical diagrams.
2. The study of the lithology of sedimentary rocks, both of those that contain animal remains and those that surround the given locality. These researches conducted reciprocally make it possible to define the character of animal remains, the cause of their disposition in a given manner, and the possibility that part of the fauna has been destroyed during the formation of the locality. Besides this, it is possible to ascertain the direction and hydrodynamical regime of the streams that precipitated the sediments, the distribution of the regions of denudation, the speed of sedimentation, embedding, and lithification, the degree of inspissation and deformation of the sediments, and the fossils contained in them, and the retracing of the physico-geographical conditions in the regions of embedding. In the end all these researches will show to what degree the given locality is a "selected" one, and will make it possible indirectly to approach the solving of the problem of correlation of the fauna embedded with that which actually existed in the region.
3. The study of the processes of fossilization of animal remains. Microscopical and chemical analyses of fossilized remains, conducted together with experimental work of artificial fossilization, and with observations of the destruction of the surfaces of organic remains in different surroundings. The study of the processes of rounding off of the bones during transportation and the calculation for each locality of the relations between the rounded off bones and the object as a whole. Here also must be studied the conservation of organic matter in different rocks, which is of great importance for the definition both of the facial conditions of the region where the locality is situated, the fossilization, and the relative periods of time. To these problems can yet be added the study of pathological changings and damages in skeleton parts and the search for tokens of great episootical illnesses; here can be found an answer to the separate causes of the destruction of animals and the formation of accumulations of remains appertaining to one species. The investigations indicated above make it possible to ascertain the condition of animal remains before fossilization, i.e., to explain the primary stages of the process of embedding and to investigate the process of destroying of animal remains before fossilization, and while it lasted.
4. Estimating the reserves of fossils. The outlining and the calculation of the mass of the layer containing animal remains for each locality. The calculation of the relations of the areas of the localities to the general area of a given layer of continental sediments. The figuring out of the average quantity of animal remains in different parts of the locality and the probable average quantity of remains in the whole locality. With the help of this latter the number of species and, sometimes, the number of forms found in the locality can be calculated.
The above mentioned research paves the way to:
5. The general reckoning up for definite lengths of geological time of the areas where the continental series are developed and the bulk of these sediments, and within them the districts containing localities of embedded land-fauna; this solves the question of the relation between the areas of sedimentation and embedding. The summing up of the results of the above mentioned work for all the continents and then the definition of the relation between the survived areas of sedimentation and the whole area of the continents of the given period, the era where the terrestrial fauna existed. In the end we can reckon up the per cent of embedded fauna.
The general comparative facial analysis of the conditions which form thick series of rocks, on this basis, the explanation of the general laws of embedding of the fauna which are typical for a given length of geological time (historical faciology of the localities). All the data obtained during the first part of the work is verified during the second:
(1) The laws of disposition and conservation of contemporary animal remains in sediments just formed or being formed now.
It is quite evident that this work is carried on in unison with the study of the origin of contemporary continental sediments. This comprises the study of biostratonomical laws in the contemporary sediments, the laws of the concentration and distribution of animal remains in the process of embedding, the laws of the concentration and scattering of animal remains in the process of contemporary sedimentation, etc.
(2) The establishing of general laws in the relations between the areas where a land fauna exists, the regions of continental sedimentation, and inside these latter, the districts where localities containing remains of terrestrial fauna are formed. The establishing of the subsequent wash-out of the sediments formed already and of the localities of sub-fossil fauna, the establishing of the comparative longevity for different types of continental sediments. This latter has a great significance for the study of facies, but rarely preserved in fossilized condition, for instance, the sediments of inclines, mountain streams, river terraces, small bogs and lakes, caves, etc. The calculation of the comparative value of the contemporary continental sediments and the areas of wash-out of the continents which will give the clue for establishing comparative data about the areas of wash-out of ancient continents.
(3) Biological observations of the number of terrestrial fauna, the dynamics of the population as a whole, and particularly, in separate biocoenoses. The establishing of the comparative quantity of destroyed species, the explanation of the causes of destruction en masse, and of the concentration of the remains of animals in habitual surroundings. The establishing of the laws of the dispersion and destruction of animal remains on the sub-aeral surface, and the calculation of the relation between the quantity of destroyed species and forms in general and the quantity of those which fall into such conditions that they are preserved. The establishing of the stability in process of time of separate biocoenoses, the establishing of the relations (quantitative and qualitative) between the population of areas of denudation and sedimentation, the establishing of the fossilized and contemporary terrestrial faunas and a synthesis the first and second areas; these are the chief directions of the work of this (biological) group.
All the works outlined above of both parts give sufficient data for a comparative analysis of the embedding of animal remains both of the fossilized and contemporary terrestrial faunas and a synthesis of the general laws of this process.
Moreover, by comparing the Quaternic fauna of land vertebrates with that of the present time, one can already come near to calculating the approximate numbers of destroyed representatives of terrestrial fauna before it was embedded.
Inasmuch as the Quaternic fauna of terrestrial vertebrates is comparatively well known and in quality (and, one must think, in quantity) greatly resembles contemporary fauna, the calculation of the general number of species and forms found in the Quaternic localities, when compared with the number of species and forms of contemporary faunas, can give an idea of the part of animal life which has been destroyed.
With due accuracy of calculations, bringing in corrections on the unexplored regions, the difference in time and series, and taking into account the changing of the mass of generations, we can obtain a sufficiently probable figure.
Such comparative figures can be obtained by comparing the areas of habitation, continental sedimentation, and of embedding, on contemporary and ancient material for separate geological units. These figures show the limits of accuracy of all our evolutionary and faunal generalities. All that has been said outlines sufficiently distinctly the problems, and methods of solving them, which are studied in the processes of embedding of terrestrial faunas.
In great part neither the problems nor methods are new. Research in the directions outlined above is going on already, being done not only by separate geologists and paleontologists, but also by the whole scientific institutions, national parks and reservations. These latter register the contemporary terrestrial fauna and study its dynamics; the work is of great importance for the comparative analysis of the processes of embedding. However, all such research is deficient from the point of view of paleontology, in the absence of a general plan or uniformity in methods; besides, it all bears an episodic character. It is self-evident that the study of the processes of embedding, as it has been said earlier, is also significant for floras and marine faunas. In this article I have outlined the field of activity for studying the processes of embedding on the material of terrestrial fauna because for these such processes have a greater significance. Because of this they have been better studied and the methods of work are more advanced. It is probable that in the future the study of the processes of embedding will develop on material of the same kind. For the marine faunas one can go along another and more easy line of research, the reconstruction of a whole fauna by the biocoenoses which have been better preserved; this is quite impossible for the terrestrial faunas.
It is necessary to unite all the separate "inclines" and directions in the study of the processes of embedding into a new branch of paleontology, the science of embedding. Earlier I have tried to show the significance of the problems solved by this branch of science, and the complexity of the methods and of the different branches of knowledge embraced by it. All this shows that the new branch of paleontology is evidently a separate and an important one.
I propose for this part of paleontology the name of "TAPHONOMY," the science of the laws of embedding. I find that this name will best reflect the chief direction of work in this new branch of paleontology. Taphonomy is certainly not a separate science. It stands on the border of paleontology, uniting it both with geology and biology into one general geo-biological historical method of study. From this point of view it is not necessary to subdivide it into taphonomy of contemporary fauna, actuotaphonomy, and of fossilized faunas, paleotaphonomy.
Taphonomical research allows us to glance into the depth of ages from another point of view than that which is in general use in paleontology. Therefore, these researches are also of importance for geology, paleogeography, faciology and sedimentology.
As regards paleontology, it is well to remember Darwin’s significant thesis: ’The life of each species is in greater dependence on other organic forms already established than on climate." Meanwhile, in the estimation of the general balance of fauna, paleontology is mostly helpless, so that a most important criterion of the knowledge of the processes of evolution is absent. Taphonomy produces a method for controlling the reconstructions on an evolutionary basis, and so aids these reconstructions to acquire the preciseness of which they are greatly in want.
By Prof. J. A. EFREMOV
Soviet Academy of Sciences. Moscow
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