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- 10 - PALEOECOLOGY OP THE VERTEBRATES By E. C. (University of Llichigan) PaleoecolOQr deals -with life in relation to its environment; this relation is so far reaching and inclusive that it necessarily includes any connotation of the term paleobiology. The environment of any organism ia the sum of its contacts with the external world, either organic or inorgan- ic. Whether the environment foe determinant in any degree of the development of life, or simply selective of forms whoso development has been otherwise determined, it is dominant among the factors that influence and control life. No phase of biology, neo- or paleo-, can be considered without reck- oning with the environment. The paleoecology of the vertebrates must deal with much the same en- vironment which governed tho associated invertebrate animals and plants. The response was conditioned by factors inherent in the vertebrates them- selves. Any discussion that would even approach a satisfactory content would be far too extended for a report of this character. The following is therefore cast in outline form with very limited amount of explanatory and illustrative material included. Tho environment of oxtinct vortobratos must bo inforrod from so much of the morphology as is revealed by the skeletons or such part of them as is recovered; from the associated remnants of life; and from the matrix in which the fossils are found. All such questions as may involve interpretation of the physiolog- ical response (function) must necessarily be answered by our ability to make such. an interpretation ar.d at present this is so limited that any definite conclusions are distracsingly meagre. All such questions as may depend upon a psychological response, which become increasingly important with tho development of tho nervous system, are unanswerable aaid at present no path is open which could lead to any answer. The three categories of interpretable matorial, the morphology of the animal considered, the associated fossils (representing the organic en- vironment), and the matrix in which the skeleton is found (representing the inorganic environment), are briefly considered below. Morphology The utterly fallacious idea that frorc a single bone tho expert can restore a complete skeleton lingers with as much persistence and with as disastrous results as does tho fallacious Biogonotic lav:. In both the

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- 11 - seductive elements of truth are present, expressed in broad generalities which load the uninstz-uctod and the incautious to faulty and incongruous conclusions. Certain structures are commonly correlated and it is usually possible to infer from the structure of tooth, limb or foot something of the habits of an animal and hence something of its environment. The hooves and char- acteristic teeth of a grazing or browsing animal are commonly associated and from these and less obvious characters of the skeleton the paleoecol- ogist may infer broad grass lands, sparsely watorod, and onomios that demand speod for oscapo, things to be checked by the remains of associated animals and by the nature of the matrix in vfoich the skeleton is entombed. For ex- ceptions to such correlation one has but to recall Moropus or Agriochoerus in both of which the teeth, limbs and a::ial skeleton suggest a grazing or browsing ungulate but in which the toes terminate in efficient claws. Either we must imagine an animal strange to the environment and present by chance, or an animal capable of living in the environment of grazing creatures but controlled by an, at least, partially different set of factors; both ex- planations have been made, the latter being the most probable. In South America the limbs and hooves of the Miocene Thpatherium are almost identical with those of the horse and are even more specialized along the same lino being "absolutely single toed, more completely raonodactyl than any horse" (\7. B. Scott, Land Mammals of the Western Hemisphere, p. 248} but the animal belongs to a different order of mammals. "If the protorotheres were not perissodactyla, as I am convinced they were not, they offered one of the most remarkable examples of convergent evolution among mammals yet made known." (W. B. Scott, idem). It is obvious that this last instance may be taken as a lesson in at least two ways. Similar correlation with the environment produced struc- tures almost identical in animals so different that they must be placed in separate orders, and both indicate a hard, grass land. Secondly, such. cor- relation has not produced similarity in more than the limbs; the structure of the teeth and skull are radically different in the North American and South American forms. Only the broadest deductions as to the nature of the environment could be drown from the form and proportions of the limbs. An example drawn from living marsupials will emphasize the diffi- culties j.nd possibilities of misinterpretation. The arboreal kangaroo, Dendrolagus. of Hew Guinea and Queensland differs from the ground kangaroo, Uacropus. only in the proportions of the limbs and minor structures of the posterior feet. Y/aterhouse says the two differ in no "essential part of the structure." Macropus lives on the "arid, withered savannahs and prairies of Australia" (Vogt) and feeds upon harsh vegetation such as the herb called "kangaroo grass." pendrolagus is entirely arboreal, living upon "leaves, bark and fruit" in the "dense, tropical forests" (Flower and Lydokkor). Surely no such radical difference of environment could be inferred from an inspection of the skeleton. As an illustration from another group, suffice it to say that the

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- 12 - author identified ono described genus and spocies of Stegocephalian and two described genera and three spocios of Phytosaur in tho first cornplete denti- tion of the lower jaw discovered; so different were the teeth in different portions of the jaw that different names, taxonomic position and inferred habits were excusably assigned to isolated teeth. Any assured inference as to food or habits of feeding is impossible from the form of the teeth in such animals as the well-known Diadectos of the Pormian, or the very imperfectly known Trilophosaurus. a cotylosaurian reptile, or Colognathus (Xenopyiathus). a fish, both from tho Triassic. Instances such as these could be cited in large numbers; these are suffi- cient to make evident that beyond certain very broad linos no inference as to habit or habitat nay be drawn with certainty from the fragmentary, or even complete, remains of the extinct vertebrates. Associated Fossils To the paleontologist whose interests are at all directed to the study of his material as once living forms, the collection of any specimen involvos a study of every phase.of its occurrence that may revoal something of its oecological relations during life. The author in his desire to obtain such information attempted to place upon paper in categorical form a list of such observations as he should make upon the discovery of a specimen and in tho course of its excavation. This statement with' the necessary explanatory matter grew to a manuscript of 87 typewritten pages with over eighty cita- tions to literature, later published as the "Elements of a Paleogeographical Problem," in Publication 283 of the Carnegie Institution of Washington, 1919. It is evident that if a reasoned list of nocossary observations can grow to such a length anything of the kind in this report must be a mere reference to other material. Thero aro, however, certain major points that may well be called to attention. The position of the specimen with. regard to its natural habitat. This must in part be considered in relation to the enclosing matrix but must also be considered with relation to associated animals and plants. A moment's consideration will make apparent the fact that many verte- brate animals can hardly be preserved in their natural habitat. Petrefuction requires burial under water or in water-bearing layers and for arboreal, aerial, dry land, and any but benthonic forms of aquatic life, this requires that bones found petrified roust have boon transported from their natural habitat to a region of radically different conditions. The transportation of a. cadaver, distended by the gases of decomposi- tion, by moving water is the simplest and most obvious of many menns by which such a change of locus can be accomplished. It is surely rather idlo to spec- ulate upon the habits and habitat of a fish whose structure implies a nectonic

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- 13 - life from the mud in which the cadaver was buried. Posthumous movement, per- haps horizontally by moving current, and certainly vertical by sinking to the bottom, have brought the remains into a position and relation which were en- tirely foreign to the activities of its life. Much inconsequential literature has been based on just such relations, notably the discussions concerning the fish found in the black shales of Triassic and Permian age. The author may here cite his own rather extensive, rather hopeless, and certainly fruitless efforts to discover some morphological structure or combination of structures which -would enable him to determine whether a fish was marine, brackish, or fresh-water in habit. Much futile discussion has gathered around just this point - the fish were fresh-water forms washed out to sea by flood either before or after death, were marine forms killed by sud- den influx of fresh-water, were estuarine and destroyed by an untoward degree of salt concentration in the water. Knowing as we :do how closely some fish are restricted to a definite salt content in the water ond how tolerant are others, it is evident that we are here dealing with a problem of physiological response, not reflected in structure, which at the present is beyond the possi- bility of solution. "By the hoof'of the Wild Goat up-tossed From the cliff where She lay in the sun, Pell the stone To the tarn where the daylight is lost." Changes ns great in degree and by causes as accidental have certainly occurred to many a residuum of life. Who can doubt that the bones of the bison and western Pronghorn Ante- lope lie buried in the delta of the Mississippi River associated with the debris of marine life, and how much more frequent must be such occurrences at the mcuths of shorter and more impetuous streams on abrupt coast lines. Dr. Carl Wiaan of the University of Upsala has described Stegocephalians from marine shales in Spitzbergen. By every implication of the physiology modern amphibians, both in ovum and after hatching, are intolerant of soa water even in extreme dilution. It is true that at least two cases of toler- ance have been reported but one of these is discredited. The author was as- sured in conversation by Dr. Wiman that the specimens were apparently found in their natural habitat, i.e., they were marine stegocephalions, but there is so.much against this, and the possibility of posthumous transportation so great, that. the author cannot give credence to Tr. Wimon's position.. If the amphibia and certain fishes are fresh-water aquatic forms their distribution is fully as acceptable evidence of land connections as is that of any' terrestrial animal. The tests of whether a specimen is preserved in its natural habitat are in part in the matrix, discussed below, in part in th« associated fossils,

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- 14 - and in part in the condition of the specimen.. If the skeleton is complete or approximately complete it may safely be assumed that it has been buried where it died, or if isolated bones are found unworn it may be assumed that they have not been transported a great distance. In general all fossil ma- terial of any locality is apt to be of the same character and with the same history, but this is not necessarily true. Instances may be cited of the two conditions. In fossiliferous areas or localities such as the Big Badlands of South Dakota, the Agate Spring bone beds of Nebraska, or the bone beds at Pikermi in Greece, the nature of the bones indicates preservation in or near the place of death. In the growing river flood-plain of Oligocene time, which is BOW the Big Badlands, the carcasses of the animals commonly found burial in the river beds or mud holes which were an integral part of their habitat. In the other two cases the large assemblage of unworn material has been explained as due to the destruction of a herd of animals of one or more kinds which were fleeing in stampede, perhaps before a grass fire. A different condition occurs in the Permo-Carboniferous beds in the Karroo area of South Africa and in north-central Texas. In the first the skeletons of the great Pareiasaurians are mostly commonly found complete or nearly so, with the bones in normal relation. In the same zone and area the great Deinocephalians are represented by imperfect skulls and isolated bones frequently in bad condition. In the Texas region the skeletons of certain reptiles and amphibians are not uncommonly complete, or with a considerable portion in association. One form, Edaphosaurus, with high dorsal spines provided with lateral knobs or branches, is rarely found except as isolated bones or fragments of the easily recognizable spines. The suggestion has been made that the Deinocephalians and Edaphosaurians were upland forms, and that their bones reached the swarsps, lagoons and river beds only after prolonged transportation and consequent disintegration. The only locality in which there is a close association of the two groups of American Permian forms is the Archer Creek Bone Bed which has every suggestion of having been something like a salt lick where animals gathered from long distances, or the sole surviving pool in a very considerable area, the last resort of animals of every kind for the necessary water. A similar illustration occurs in the Pleistocene deposits of Michigan and adjacent states. The author has records of over eighty Mastodons and only seventeen elephants from Michigan, this is perhaps a quarter of all that have been found, but the proportions would probably remain approximately the same. The records of Mastodons show them to have been found in areas or deposits that were swamps or lowlands. The Mastodon was a browsing animal, at home in such a habitat. The Elephant, a grazing animal with teeth adapted to grinding hard grasses and grains, was of the upland and its remains were destroyed by subaerial and organic processes before they could be buried and preserved. A single specimen of an elephant is known which approaches com- pletion, this was found on a layer of sand beneath eight feet of marl. One imagines a sick or wounded animal seeking and dying upon the bank of an expanding glacial lake. Other traces of the elephant are isolated, and

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- 15 - generally fragmentary, teeth or bones usually found in gravel pits, indicat- ing transportation of the elements of disintegrated skeletons. If it is determined that a group of animals has teen preserved in its natural habitat the paleoecologist is concerned with the balance of the or- ganic elements of the habitat, the adjustment of the herbivorous, carnivor- ous, carrion-eating, malacophagous, durophagous, and other forms to their food supply. Any suggestion as to diet must be checked by evidence of the presence of such a food supply. The forn of the teeth indicates much but only too often the indications are vague or erroneous and only. too often the form of the teeth leaves but a question. The teeth of Diadectes, of Trilophosaurus, of Ptilodus, among many instances, give but the vaguest hints of the habitual food. The author has fed a certain mule, whose teeth were adapted to grazing, soft watermelon rind and has had his tarpaulin chewed by the same mule. He has fed a squirrel soft peppermint candy and his family cat soft, boiled peas. These are abnormalities and would be absurd if they were not facts; I doubt if they are more absurd than some attempts to in- terpret food habits from the forni of the teeth, unchecked by other evidence. The unending strife for food, the battle between the eater and the eaten, can be, must be, read by the paleoecologist. Defense may be by active or passive resistance. Flight or 'offensive defense,• or passive donning of armor, may all be employed but any method implies a reason for its adoption, and every advance in either method implies increased power of attack from the eater. .The process of such adjustment is continuous and leads to a specializa- tion that is the shortest road to extinction. In the case of armored forms versus armed forms, it has led invariably to but one result; in every group and in every age the story has been repeated. As the armor grew heavier, the projectile and propulsive force grew stronger. Tooth and claw and muscular power have been balanced against ever heavier and more complete armor. The invariable result has been the extinction of both. The same history has been written and is being written by warring men, one dares prophecy the same re- sult. . : A most interesting fact has been demonstrated by the process of paleon- tological discovery. The progress of the plant world to modern types has consistently outdistanced the animal world. The modern deciduous trees shaded the Mesozoic reptiles in their later days. The Permian plants sheltered the late Pennsylvanian fauua and the suggestion of plant precedence is carried back even to Devonian time. The paleobotanist and the paleozoologist have been at variance as to the boundaries of eras' and periods. The paleoecologist who would see rightly must not flinch from the vision of a Tyranncsaurus stalking through a forest of modern aspect. Certainly if such a vision were granted the paleoecologist would give thanks for the towering height of the elm or the sturdiness of some giant oak. - • * • There is ample evidence of bacterial decay; there is, except in more recent forms, little evidence of bacterial disease. We can not doubt that bacteria, protozoans and parasites were present early in geological time and wrought help end hindrance as they do today. Evidence of such things is blind or lacking. The bacteriologists and pathologists the author has consulted

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- 16 - are reluctant to recognize these things from the effect produced or from such evidence as can be presented. Dr. Novy refuses to recognize bacteria "until I can see them divide." It is, however, a suggestive coincidence that the blood of living reptiles is abundantly supplied, "swarms," with protozoan fornis, various fojns of which are the cause of communicable dis- eases of virulent and fatal character, and that the blood-sucking flies which are the usual carriers of such protozoans appeared in the Jurassic, preceding by a reasonable interval the extinction of highly specialized reptiles at the end of the Cretaceous. The attitude of the skeleton is frequently of significance. In the case of the dinosaurs at the Dinosaur National Monument in Utah the heavier body dragging on the bottom of the moving waters permitted the long neck and the long tail to advance with the current. This not only gives the direction of the current but explains in many cases the peculiar attitude in which many long-necked and long-tailed forms are found, an attitude vfoich has been in- terpreted as due to an opisthotonic death spasm such as occurs in fatal cases of tetanus and in poisoning by strychnine. The later explanation has not received much support but is mentioned here as one of the ramifications of paleobiology and paleoecology. Another illustration of the attempt to read function from form is the suggested explanation of the common specialization of giantism which occurs in almost every group near the time of extinction. The term giant- ism is, of course, used relatively. Normally minute animals may have giant species or individuals, as well as normally much larger animals. It has been noticed and commented upon that in giant forms of vertebrates the seat of the pituitary gland is relatively enlarged, even to monstrous size. This suggestion has been followed by the late Doctor Nopsca who has shown a very probable relation between this endocrine gland and the size of the animal. He has brought forward evidence to show that giant forms have uniformly a pituitary gland of large size and that the structure of the animal shows ab- normalities of proportionate growth such as occur in cases of enlarged pitu- itary in humans, the condition called acromegally. That such a condition may be endemic in a population of vertebrates is shown by the discovery that a considerable number of the skeletons excavated on the site of one of the long lost and forgotten early colonies of Northmen in Greenland, showed obvious evidence of acromegally. The cause of acromegally is obscure, but if it shall turn out to be due to some lack or excess of material in the food sup- ply, as the thyroid is affected by lack of iodine, the relation of giantism to the environment is obvious. This nay seon a far fetched hypothesis but to those who have paid any attention to the conditions of growth it is very conceivable that such a small thing as ionic concentration in the water vfoich the animal inhabits or imbibes may be the detenainant factor in its development and fate. An instance of the many attempts to translate form and form rela- tions into terms of biology is the constant effort to arrange series in the different groups by the proportions of the body. Such efforts have culmi- nated in Osborn's Monograph upon the Titanotheres and Gregory's recent ef- forts to generalize upon the development of the vertebrate skull. These

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- 17 - gentlemen have arranged various homologous skeletal elements according to proportions and have assumed that their assemblage is in accordance with the true course of phylogenetic development, and have finally attempted an explanation of their series based upon genetic principles. It is admitted that the series selected are plausible and are sus- ceptible of explanation upon. biological principles, but it remains to be proven that the series formed are phylogenetic and not morphological, that the serial differences are the result of phylogenetic change and not acci- dental similarities. It remains to be proven that sufficient material has been recovered to justify the generalizations pronounced or that other characters than those selected might not lead to entirely discordant re- sults. It is but another and perhaps more sophisticated attempt to read the processes of life, physiology, from the form of but a single region of the animal body. The difficulties in the path of the various attempts to bridge the gap between the dead remains and the living animal is reflected in the abundant coinage of new terms which, one and all, have a decided morphological connotation, "budding," "reduplication," "metamerism," "rec- tigradation," "aristogenesis," "polymerism," "differentiation," "allometry,' "heterogony," "acceleration and retardation," "anisomerism." (The terms are quoted from a late paper by Gregory). One has the uneasy sensation of viewing a brittle, artificial edifice lacking the elasticity and re- silience of life. The assemblage of incidents and suggestions in the preceding pages is not, and is not intended to be, even approximately, definitive or ex- haustive but merely serves to direct attention to a few of 1he innumerable factors of paleoecology which influence life. • The Matrix .For the vast majority of land animals and for all fish except benthonic forms, the matrix of entombment is radically different from the normal environment of the animal. As a generality it may be said that the matrix of the aquatic amphibia most nearly represents the environment of the living thing, l»ut even this is subject to exception. The only cases in which terrestrial vertebrates are preserved in a matrix directly picturing the environment is where fonns are buried in the sand dunes of a desert, or covered by other local material, as in the miring of animals in swamps and quicksands. In other cases the animal either perishes in some body of water or the carcass or bones are washed into it. Deposits in a body of water are composed of material which only secondarily and imperfectly records the character of the adjacent land. Even in the quick deposition in a pond or lake the rills and streams which carry the material to it have exercised a sorting and selective action, leaving behind the coarse and conveying the finer, in various degrees de- pendent upon the velocity of the current and the volume of the stream. In larger streams, as rivers, the sorting and selection is more ef- fective. It is obvious that the carcass of a bison carried miles from the

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- 18 - place of death and cast upon a sand bar of the Missouri River, or floated far out upon the flood plain in time of high water and buried in the silt of some slough or'backwater will leave the skeleton in a position where the matrix gives no hint of the normal environment. Knowing the bison and the Missouri River and its course, the situation is clearly understood, but given even the perfect skeleton of an unknown Eocene animal with generalized structure and found in a small exposure of what was perhaps, or probably, an Eocene river bed, the realities of the situation as a problem are more apparent. Within a few square yards of exposure of uniform clay in the Big Badlands, the author recovered remains of a rhinoceros, a three-toed horse, a hawk, a mouse-like rodent, and a catfish. Any accurate interpretation of the assemblage would be difficult. The salmon migrate far up the streams emptying into the Pacific and penetrate to the utmost sources of the waters. Thousands die of exhaustion after spanning or from injury. The skeleton of a salmon far above sea level in tha muck of an upland forest is understandable. Knowing nothing of the habits of a Paleozoic or Mesozoic fish, the peculiarities of the matrix and the associated fossils might be very puzzling and lead to sad misinter- pretation. In younger deposits the matrix may in most cases be taken to be what it vras, in color, texture and content, -when deposited. In more ancient de- .posits the chances that the matrix is unchanged are far less. It w>uld be a most serious error to assume habits' and habitat from the appearance and condition of the matrix in many cases. Take the classic example of the red beds which have been so often, so brilliantly and so inconclusively explained. The color has been explained by original deposition of ferric oxide, by secondary infiltration, by de- hydration due to the pressure of incumbent beds, by change in ground water level. It has even been assxened that red beds mean some.definite condition and that red beds are uniformly red, instead of yellow, green, blue, purple and all intermediate shades. Any interpretation based on the assumption that the matrix has remained unaltered in all its characters since first deposited is the first error of the veriest tyro. The black shales, recurrent in several geological periods, aro equal- ly difficult. Explained in many ways by different authors, they have been but recently reinterpreted by Doctor Ruedemann. . A recent examination of the various possible processes of pyritiza- tion shows how undspendable is any assumption that pyritizcd fossils, or fossils accompanied by pyrite in the matrix, mem foul bottom conditions during the life of the fauna; or that the sulfidcs were derived from the decay of the animal bodies, or indeed, that the pyrite is in any way neces- sarily connected vrith the life of the animals preserved fossil. The chemical, mineralogical and physical character of any matrix is

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- 19 - subject to change and possibly profound change without destroying the evi- dence of life» The author possesses fragmentary remains of Baculites and Placentieeras shells and Plesiosaur bones from the Cretaceous of southwest- ern Minnesota which are completely converted into bright red haematite. Metamorphism (in the sense of Van Hise - "any change in any rock") and structural changes are responsible for a part of the peculiar conditions. It may be truly said, and it has certainly been true with the author, that a vertebrate paleontologist can not write of his faunas without a copy of Van Hise's Metamorphism, Clark's Data of Geochemistry, Twonhofel's Treatise on Sedimentation, near his hand. " " ~ As the remains of terrestrial animals are most commonly found in sub- aqueous deposits, the environment can only be read in the debris from that environment. Any aggraded area is to the land as the negative is to a photographic print. The alteration of material by weathering before trans- portation, the selective action of the water before deposition, the altera- tion of material as it lies below the surface of either stagnant or moving water, the extraction or addition of material by the waters, all those and many more confuse the record. The physical condition of the sediments presents maiy confusing prob- lems. The author has submitted sand and sandstone samples to experts to de- termine their origin, whether aerial or subaquatic, only to be told in sev- eral cases that it was windblown sand that had finally been blown into the water. The question remained Aether the fossils were to be interpreted in correlation with the sand as a terrestrial or as a subaqueous sediment. It is interesting to note that most of the vertebrates of the Upper Triassic in tie western part of the United States are found in river, delta or pool deposits; every implication of these deposits is that they were derived from an arid land. For the Stegocephalia and the Phytosaurs, which latter are so crocodile-like in structure as to leave little doubt of their habitat, the deposits and the animals arc well correlated but it is a little difficult to picture the adjacent lands, because the remains of terrestrial animals and plants are so limited. The occasional pool or water course in the desert of today is crowded with hydrophytic plants. Spalding long ago cited the presence of Willow and Arrowleaves in stream courses wnose banks were sparsely dotted with Xerophytes, Greasewood, Chapparal, Cactus and so forth. The author has seen a large pool caused by the overflow of ah irrigating ditch in extreme south- western VTyoming crowded with wading and swimming birds and circled by gulls. A small exposure of either environment within a quarter of a mile of each other would lead to curious conclusions. The author asks leave to quote an instance reported many years since. "The author again calls to notice his experience on an area of wind-blown sand in a desert portion of Arizona, where he found ripplo-marks, stalks of thin-leaved vegetation, obscure in- sect tracks, and a series of sinuous convolute markings where some insect burrowing beneath the burning sand had thrown up a

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- 20 - long trail indistinguishable from worm tracks at the bottom of a shallow body of water. He went over much of the area most care- fully, certainly over far more than is normally exposed in a geo- logical, outcrop, and utterly failed to find a single criterion that would have prevented him from pronouncing the exposure an old sea-bottom or flood-plain if it had been found fossil, and yet the formation was going on before his very eyes on a sun-stricken bit of desert. The insect "burrows would have unhesitatingly been called worm tracks; the insect tracks might have been made by any one of many aquatic forms instead of beetles or grasshoppers; the vegeta- tion once fallen and recorded only as an imprint could not be told from a bit of aquatic vegetation. The wind ripples upon most care- ful analysis might have revealed their origin, but again, in the author's experience, sand collected in a delta deposit has been pro- nounced dunesand which had drifted into the water." (1) In the Museum of Paleontology of the University of Michigan there is a collection of many Stegoceplialisn skulls and other closely intermingled bones recovered from Triassic deposits in western Texas. The skulls and the clavicles amd interclavicles showing peculiarly sharp and intricate sculpture, the needle-like teeth, are perfect and the paper thin edges of certain bones are intact; they are as perfectly preserved as any fossil ma- terial the author has seen. These bones were recovered from a coarse sand- stone with some bits ranging up to 18 to 30 millimeters in diameter and with some, but slight, evidence of current sorting. How the fragile bones and teeth and the sculpture could have been preserved in such material is dif- ficult to imagine. Perhaps a quicksand, but a hydrostatic pressure that could have given such coarse material the qualities of a quicksand would have prevented the sinking of the flat bodies. No raotion of the material seems possible, the bones would otherwise have been worn or destroyed as in a mill. An abundance of instances could be cited by every worker, drawn from his own experience, illustrating the direction of inquiry and observation and the multitude of pitfalls that await the worker in paleoecology. It is certainly apparent that only an approximation to the correct appreciation of any environment can be realized by methods now at the command of any worker. The most wholesome advice that can be given is that the inevitable separa- tion of the two schools of paleontology be recognized and provided for by adequate training of the workers to come. The stratigrapher and areal geologist is concerned with the fossils only as recognition symbols and time markers. The paleobiologist is con- cerned with them as records of a life that has passed. No matter how clear- ly the stratigrapher recognizes the biologic principles involved his work is on other lines and the biologic factors are remote from his consciousness in solving any problem. The paleobiologist is equally unready with the factors that are of prime importance to the stratigrapher. The condition is already well recognized in Europe inhere chairs of paleobiology, divisions of paleobiology, and even large buildings are devoted to the interpretation of past life and the location of the beds in time is (1) Case, E.G., The Environment of Vertebrate Life in the Late Paleozoic in North .America. Carnegie Instit. of Washington, Publ. no.283 (1919), pp. 42-43.

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- 21 - but one of many necessary tools. As written above, the fission is inevitable, tiie two schools must be prepared to afford mutual criticism and aid, the paleontologist in training must be prepared to know the elements of both phases of the work, but choose one for intensive training - and provision must be made for such intensive training.