Report of the Committee on Paleoecology, 1936-1937; Presented at the Annual Meeting of the Division of Geology and Geography, National Research Council, May 1, 1937 (1937)

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- 26 - BRACHIOPOD ECOLOGY AND PALEC2CGLCGY >--..;• rv. 6. Arthur Cooper* . .. Introduction' . . . '. J. •.- . . . . . . , Life for most organisms is a struggle against adverse physical conditions and inimical neighbors. Nowhere is this, struggle against en- •:virpnment more severe than in the sea. Any seashore will show windrows of ;dead shells, the victims of storms or rapacious enemies. Although the strife is unceasing and cruel, life itself has survived this uncom- promising environment through countless ages. Eons of struggle, have lead •bo the spinning of an amazingly complicated web of life in which all con- temporary species .in any given environment are more or less remotely in- volved. The enemy of one organism may be the unwitting friend of another and the welfare of one or more species may depend on the prosperity of other forms. The study of the complicated relationships of organisms to one another and to their physical environment is Ecology.,.. The generalities of historical geology are now common knowledge. . Host informed- people know that many sedimentary rocks are solidified sea- •:-.- bottoms. ,Jt is also well known that these petrified sea-bottoms have en- tombed many luckless molluscs and other animals. The sedimentary rocks and their contained fossils thus have a story of their own to tell, but the tale is told in no simple language. Fossils and sediments are the characters that must be read\to understand the earlier stages of the struggle of life against its environment, It has taken millions of years to weave the web of ecology about us. Fossils and sediments are the docu- ments of P. a 1 e o e c o 1 o g y, or the study of ancient ecology. An amazing quantity of data dealing with fossils and sediments has been accumulated during the last century. Yet with this mass of informa- tion relating to these special subjects it is painfully disconcerting to learn that few investigators have concerned themselves with the subject of Paleoecology. The study is new and when seriously pursued should lead to results of distinct benefit to the geological and biological sciences. Although data bearing on the ecology of many groups of animals has been gathered, the ecology of modern brachiopods, as well as their palec— ecology, has been neglected. The various treatises on modern brachiopods yield little direct information bearing on their habits, their relation- ships to contemporary organisms, their embryology and life history. The reason for this gap in our knowledge is not difficult to understand. Brachiopods are now rare animals and usually difficult to secure. More- over, the study of this group is still in the qualitative and descriptive * Published with permission of the Secretary of the Smithsonian Institu- tion.

- 27 - stage. Zoology, embryology and biology have long" since practically aban- doned qualitative research. It is no longer a vogue to describe the life history of a species, consequently many 'years may go by before some of the foremost questions concerning brachiopods and -their ecology will be answered. ' . • - !--'-j- '•• - •*• . J:V •• ' ' This present discussion of brachiopod ecology and paleoecology is admittedly incomplete, because time did not permit an exhauotive search of the voluminous brachiopod literature. The appended bibliography by no means exhausts the papers having ecological information, There are un- doubtediy many data buried in 'descriptive papers, which only future study will bring out. • • • • '" ' • '...-•:• . : -..•••... . ...• • . • . '• •'••« •"••; Brachiopod Anatomy " •• . • .••». • - • • •• . . .. . Mi . . • •: .iT""' " . -.... ' ..,'•'-, • -. . .. . ..-..,... Iri the most general terms the brachiopod may be described as , bilaterally symmetrical, inequivalved bivalves„ The larger shell .as a rule is on the ventral side of the animal and the smaller one on the dorsal side. The valves are -held'together inora.^less.-tightly by teeth and sock- ets (articulate brachiopods) in some forms, but only by muscles in others (inarticulates). The brachiopod i3 either seasile ;t>r- sedentary. When sessile it may be cemented by the ventral valve to some object such as a shell or piece of coral or may be fastened by a fleshy pedicle.which pro- trudes from an opening in the beak of the ventral valve, A few forms have the ability to burrow in sand and mud and to move about with difficulty. • • ,'' ,- .-• i • ' "..'. Inside the valves the. body proper occupies the body cavity at the posterior or beak region. The body cavity contains the gullet, stomach, intestine and liver, as well as other vital organs, and is traversed by a complicated set of muscles which open and close the valves and turn the animal on its pedicle. The mouth opens into the mantle cavity which contains the lophophore or brachia, a cirrate loop or horseshoe-shaped organ, "Movement b'f'cirri 'on the lophophore create the ^urrent,s of water ' necessary $o briiig to the mduth the tiny animals and plants on which the brachipppd.Tee'ds, • • «• ::' \': , . , ., ii • .^. •..; -.-,..,'..,. ' '.".:'!',•' '*" " ' ''•* •'*"•' <":':' "(• ...!..'.v ... ' Brachj'opods in Past and Present Faunas .--.; ;.-. ,•.; ." ',•-.- -ii"- ' ..'.*" •••••' I ".•.'.;•; .- .. '.. , Brachiopods have existed from early Cambrian time,to the present^ Now their numbers are greatly reduced but the past has seen a greatarray of these animals. Many bizarre and little understood types lived,in by- gone eras.and the evolution of the class is now nearly complete. This great group of animals with its glorious past:is thus- an ideal one to Study in otder'.to learn the laws of evolution and ecology. The braphiopod 'by its verjr nature is intimately tied to its environment but ..as.,will be seen below the race is a hardy one, resisting many changes in external conditions--and-persietang since._the known dawn of life. The meaning of all brachiopod' adaptations is by no means 'clearj"spine '.suggSstf'fthe 'Impress

-.28 - of environment but others indicate that initiated trends continued be- yond usefulness to extinction. Today but a handful of genera and species remain to represent the lineages of the past. However, these few modern brachiopods are of ut- most importance to the biologist and geologist, because they yield the only first-hand knowledge of the life processes and habits of these ani- mals. Unfortunately, the brachiopods occupy a very subordinate position in the seas today, consequently the class has been neglected by modern zoologists and biologists. -.••:'.- . - Except in a few instances living brachiopods form a small percent- age of the fauna at any given place. At most stations they are rare prizes but in a few localities species occur in considerable abundance. At the present writing a few more than 200 species distributed among 61 genera are known. It is likely that this number will be materially increased with time but the list of living brachiopods will never attain very im- posing proportions. Distribution of Recent Brachiopods Modern brachiopods are world-wide in their distribution. In general they are located along the coastal margins of the continents and oceanic islands. They may occupy tidal regions or shallow marginal waters or they may live in deeper waters on the continental slopes or in the deep waters margining the oceanic islands. Several important centers of brachiopods have been found. The Mediterranean, northwest coast of Africa, Spain, and the British Isles are inhabited by a group of species whose nearest relatives are found in the West Indies. The West Indian brachiopod fauna extends from the southern tip of Florida to Trinidad. A few species are known from the New England coast to Labrador and Greenland. These are re- lated to Arctic forms. In the Pacific a few species are known from the Hawaiian Islands and the Philippines but the waters about the Japanese Islands contain one- of the most prolific modern brachiopod faunules. The Hawaiian and Japa- nese brachiopods are related to those found along the west coast of North America from southern California to Alaska, li the southern Pacific the waters along the southeastern shore of Australia and New Zealand contain brachiopods of types similar to those found along the shores of southern South America. The cold waters off the Antarctic Continent also contain related austral genera. Modern brachiopods occupy all bethymetric zones of the sea. Some species are confined to shallow water! but others have been found only in deep water. Many species are found in both deep and shallow water. 1. Shallow water is from the tide zone to 100 fathoms.

• ;'<- - 29 - The/bathymetric range of Frieleia halli Pall, for example, is from 21 ' .jfathpms to 1,059 fathotas0~"rX)f"the known .recent species, numbering a .little more than 200, those'confined to shallow water comprise 59 species or about 33 percent„* Iri.this\gfoup occur all known species of Lin^ula (ll). and Glottidia (5). Other genera confined to shallow water are • - .Cnismatocentrum. Megerlina. Coptbthyris. Bouchardla and Mf££JiiYr.if> 'A few other genera have one or more species confined to shallow wafers Discinisca. Crania. Hemi-thyris. Terebi^atulina. Terebratalla. TerebrateLla, and Magellania. A still larger percentage of brachiopods occupies water deeper than 100 fathoms,. Sixty-three species or 36 percent of known species .- with data occupy this realnu Pelagodiscus. Ab^sdthyriSj Neorptaichia . and Macandrevia ameri-cana^ DaU. have been dredged from water deeper than 2000. fathoms. Abyssothyri^ wyv^lei (Davidson) has been taken from - • 29,00 fathoms, and PelagodJ^eus atlariticus (King) from 2737: fathorfis, Other './'. genera taken from deep water are BasiJaola. • Eucalathj.s, and The remaining 55 species or 2? percent of recent brachiopods with bathymetric data are found in w;aters ranging from the tide— zone to the deeps. Some of .these species are able to endure amazing differences of pressure and temperature. . 3ome of the genera having a vride bathymetric -range are: Crania., Frieleia. Terebratulina. GQ&huJ j •• A r^jr £t heca^ JSati Campages. Lagueus and DaUlna. Sixty percent of brachioijod species thus occupy shallow water but only a little more than half of this percentage is actually confined to shallow water. 'The ibove figures thus allow no generalization other than the well known fact that Lingula and its ,61ose relative Glottidia are confined to the shore zone. It will be noticed that these figures do not agree"with those pub- lished by Professor Schuchert in i911s2 Two reasons account for the dis- crepancy. (1) Many new genera and species have been described since 1911-. A large percentage of these new species are deep water forms proposed by Dall in 1924, (2) Many old genera '. have been drastically revised. The eleven species of HemithjjTris rioted by Schuchert have been distributed •among four genera. It is obviously impossible at the present time to generalize on the bathymetric range of the brabhiopods. Too little is now known of these rare animals and future dredging will alter the present figures, '• "•' • '• ' '. 1. This percentage was obtained by eliminating 25 living species on ^ "- which rib,data were availabi&. The figures .arrived_at are based on 177 species with data. ... . 2« The writer's figures were taken from Thomson's."Braehiopoda Morphology and Genera'% and from the Annotated list of Recent Brachiopoda in the U, S. National Museum (Dall, 1920)0

-30- Brachiopods are often very abundant where they live, which is to be expected of sessile animals. If one were to judge by the superb col- lection of recent brachiopods in the U. S. National Museum he might be led to believe that shallow \/ater brachiopcds were more abundant as to individuals than deep water brachiopods. This is also misleading be- cause the shallow water forms are easier to obtain. Deep sea forms may be very numerous at any given place but the dredge actually samples only a minute portion of the bottom. Habitats of Recent Brachiopods The life habits of Linsula and Glottidia are perhaps the best known of all brachiopcds. The species of these two genera live near the shore from tide zone to about 1? fathoms. Some have been found near the mouths of rivers. The animal has a long pedicle which is capable of con- siderable motion. Ordinarily the Lingula lives fastened in burrows by its pedicle. The anterior third protrudes from the sand or mud. If Lin- gula is taken from its burrow and thrown on the sand it will bury itself again. It is thus capable of motion which it accomplishes by means of lateral movements of the dorsal valve, movements of the lateral setae and a wiggling motion of the pedicle. Lingula fixes itself in its burrow by secreting mucus which agglutinates sand grains or mud to form a tube. The pedicle permits protrusion from the burrow and instant withdrawal when alarmed. The mantle edge at the front of the shell is provided with numerous setae, which, when the animal is feeding, are so arranged as to form three elliptical channels. Movement of the cirri causes water to be drawn into the two lateral canals and expels it from the central one which is a little longer than the others.^- •:. . » • : Discinisca is structurally related to Lingule but leads an en- tirely sessile life after fixation. The shell is attached to rocks or other objects by a short stout pedicle. * ' • " ...'-''"*'. The terebratulids are the most abundant group of brachiopcds living today, forming a little less than seventy percent of the known genera. The majority of terebratulid species possess a short pedicle by which they are tightly fixed to the substratum. In general the ventral value lies obliquely over the dorsal valve. Thus the dorsal valve may occupy the lower position when the animal clings to the upper surface of a stone, but the ventral valve may occupy a lower position if the brachiopod fixes itself to the under side of a stone. 1. Morse, E. S. "Observations on Living Brachiopods", Mem. Boston Soc, Nat. Hist., vol. 15, no. 8, p. 319, 1902. '. .,

-31 - *L'v • -j • • * "I- ' "'*:•: ' '..- ' •':. V -• ' • :;, •• ' , •. : 'I :• ..; . . Number a of, Brachiopods ' .' '• ' ' "•"* '' \ '-'. Modern brachiopods are jiifistly'rare -arid little knpwn animals, but in past geological periods they, were an abundant form of life,' The .Paleo- zoic Era mightr.be termed, the age. of brachlppods. They were,.sp abundant that some of the Paleozoic rooks are literally made up of tftdtl' shells. During this vast stretch of time many stocks of brachiopods rose to as- cendancy only to decline and be replaced by new forms. During the Paleo- zoic, types of brachiopods were produced which were never again dupli- cated by later stocks of brachiopods. The paleozoic ascendancy .was brought to a tragic close during Permian time, A few. Paleozoic types survived into the Triassic period and still fewer into the Jurassic- After Jurassic time two stocks, the rhynchonellids and"the terebratulids, flourished while a few inarticulates straggled on. •"-'•;; Throughout time there has been a gradual decline of brachiopods but at the same time, a gradual rise to dominance of the Mollusca, chiefly pelecypods,. oephalopods and gastropods. In the early^Paleozoic the Mol- lusca occupied a position numerically subordinate to the brachiopcds. The.Devonian witnessed an advance in the numbers of pelecypods and gastro- pods, which became still more apparent in the Carboniferous and Permian periods* This increase in Molluscs, continued steadily through the Mesc— zoic to recent times. The snails and ammonites, together with'increas- ing numbers of vertebrates, by their voracious habits, may have played '••'•' ' an important role in overwhelming the brachiopods. * • •' •'- .i, * *. History of Brachiopod Stocks The earliest brachiopods are still shrouded in obscurity. Chapman^- has described two genera, Protobolella and Fermorja from the Pre-Cambrian of India, but the characters of these forms are very indefinite, Fehton '••• and Fenton^ have described Iiingulella from supposed Pre-Cambriah strata - :'/ in Montana but most authorities agree that the age of these beds is very '•' questionable. The earliest undoubted brachiopod genera in North America are Obolella and Rustella. The former is a somewhat advanced type with a pedicle foramen but: Ruatejy^a is the most primitive form known and is a . ' member of Thomson's Paiaeptremata, gusteila with its calcareous' - shell and Cbolella with its 'specialized pedicle opening are both actually advanced'- ' types,, Not long after these two forms there appear several 'more advanced types? Nisusia, Kijtpr_gina and two undescribed genera, onevJitli-.strong ribs and looking somewhat like the Ordovician P^tyjtropMaj the other with fine ribs but a deeply sulcate ventral valve. Pai2£L?ia/ which is a 1. Rec. Geol. Surv. India,'vol. 69, pt^ 1, pp. 114~118, 1935'i . 2, Bull. Geol. Soc. Amer., vol. 47, no...if, pp. 609-620, 1936i-

- . •• - 32 - chitinous inarticulate genus, occurs with the genera nained above. Paterina is regarded by sonie as the most primitive brachiopod but it is actually of a quite advanced and specialized type. Nisusia appears to be the old- est and most primitive known articulate brachiopod, but it has features of a specialized nature. It is apparent, therefore, that a long evolu- tion of brachiopods preceded the genera named* After these forms the Lower Cambrian stocks persist with little change until the Upper Cambrian, when .a number of new types appear.> A brief survey of the rise and decline of the major stocks of brachiopods will, serve as a background for the ecological discussions to follow. The linguloid brachiopods, to which may be added the oboloids, which are chitinous, elongate or oval, compressed animals, appeared in the Lower Cambrian with Lingule'lla. The linguloids have persisted from then until present time. They are hardy animals which have, through most of-geological time, endured the vicissitudes of the shore-region. The Neotremata.are chitinous forms with specialized pedicle open- ings. They flourished in Cambrian time but declined rapidly in the Ordo- vician. From then on the order has straggled along to tfecent time and is represented by three genera today; Disciniscat Pelagodiscus. and Piscina. The Protremata were a great stock of brachiopods having an open delthyrium or one modified by a calcareous plate, the deltidium. In gen- eral it may be said that this order was represented by six major stocks: Syntrophids, clitambonitids, orthids, dalmanellids, pentamerids and strophomenids. The syntrophids had medianly folded shells with a spondylium simplex. They appeared in late Cambrian time and flourished in the Cana- dian but declined and disappeared in the Silurian. The clitambonitids were wide-hinged forms with a spondylium simplex. The stock lived from the Middle to Upper OrdoviaLan. The orthids which had impunctate, wide-hinged shells, appeared in the early Cambrian and persisted to early Devonian time. The dalmanellids were punctate orthids which appeared first in Chazyan time and existed until late Permian. The true pentamerids mostly had large shells with a spondylium duplex. They appeared in the Middle Ordovician and died out in Upper Devonian time. The strophomenids, includ- ing the Sowerbyella-Chonetes stock, the productids, and the strophomenids proper, all had a deltidium and a pseudo-punctate shell. The strophomenids appeared in the late Canadian and persisted through the Permian. The Sowerbyella-Chonetes stock originated in the late Canadian and persisted into the Permian. The productids originated in Middle Devonian and lived through Permian time. fc • '. The Telotremata are characterized by the presence of deltidial plates restricting the delthyrium and consist of three major stocks: zrhynchonellids9spiriferids, and terebratulids or loop-bearers. The rhynchonellids appeared in the Chazyan and have persisted to the present.

•• '• — -33 - Impunctate spiriferids appeared in Chazyan times and lived into the Triassic, but the punctate spiriferids appeared .possibly in late Crdovician, but certainly in early Silurian time, and died out in the Jurassic* The terebratulids appeared doubtfully in Middle Silurian time but are defin- itely known in the Late Silurian and exist at the present time* ',»• The .critical times of brachiopod evolution appear to be late Cant- brian, Late'Canadian, Permian, Triassic and Jurassic times. These periods aij.1 saw the disappearance or appearance of important stocks. A few in- :articulate stocks were very persistent, particularly the linguloids. Among the articulate brachiopods it is interesting to note apparent sur- vival value of punctae. The punctate dalmanellids outlived the impunctate orthoids and the punctate spiriferids persisted into the Jurassic .after the. impunctate forms had died out in the Triassic, The punctate loop- bearers or terebratulids are today the most-.abundant types of brachiopods forming about 70 percent of the known members of the class, thus far out- numbering the rhynchonellids. Except for bizarre types and unusual forms there is nothing to in- dicate that the brachiopods lived in the past in a manner different from that followed today. In the past they were very abundant; these hosts must have used vast quantities of food and must also have furnished the principal.diet of many carnivorous, invertebrates, fish, and marine reptiles* Methods^ j>f Pale cacology of Animals • ... ! In studying the paleoecology of any group of animals the paleon- tologist follows several lines of inquiry. The easiest and perhaps most .accurate is comparison of'fossils with recent animals of similar form and structure. The original position of the fossil in the rock often, yields .a clue to its life habits. Associated fossils may help in explaining > the environment of c'ertain forms. The -type of enclosing sediment may tell in what kind of environment the fossil lived. A study of Paleogeography is also another resort in studying ancient environments. To 'these lines of study may be added the adaptations of form, ornamentation, and struc- ture of the animals under Tjprisideratipn<< -Experience has shown that cer- tain types of animals are customarily'; found in definite environments. AH of the methods'stated have dangers that must be considered. Before an ancient environment can be regarded as established all lines of in- quiry must be investigated, ...-••.. -, . •• ' ••',' .Analogy with modern armnalS.-^Gomparison of fossil forms with Recent ones is the most direct"method of paleoecological research, With .brachio- pods, unfortunately, the method is of very limited application and is hazardous when applied to Paleozoic brachiopods. Comparison of Recent and Tertiary brachibpods is helpful,.^t when the strange and aberrant forms of the Paleozoic are compared, analogy becomes strained9 The method L.

-34 - is applicable only to types related to or structurally like modern brachio- pods, such as, lingulids, discinids, craniids, rhynchonellicis, and tere- bratulids. The Protremata includes few forms suggestive of modern types. A few modern species, however, have adaptations of form fniggestive of ancient genera. ArgjrnAheca, for example, has the same wide-hinged form as Gyrtina of the Devonian,, Argyrotheca. lives with the beaks closely attached to some object of support. Specimens of Cyrtina from the Devonian attached to other shells in their position of growth indicate that this genus had the same habit of life. Although the two genera are thus be- lieved to have had essentially the same habit the structure of their for- amina shows that their pedicles were completely unlike. The terebratulids and rhynchonellids of the Paleozoic are close structurally to the recent representatives of these two groups and all evidence points to the fact that ancient forms lived in the same manner as the modern ones live, "Linpula" of the Paleozoic is structurally very close to modern Lingula. This fact taken with the kind of sediments in which "Lingula" is usually found and the fact that these sediments on paleogeographical evidence can often be shown to be close to an old shore, indicates that this genus must always have inhabited the shore zone. No other fossil and Recent brachiopod stock yields such clear and reliable evidence• The bathymetric range of many recent species is so great as to preclude their usefulness in paleoecology. Lingula is the only brachiopod type known to be restricted to a definite zone. Other brachiopod species now known to be restricted to shallow water are of types that range into deeper water or the abysses. This makes the use of any terebratulid or rhynchonellid of the modern seas dangerous in studies of ancient bathymetry. Furthermore, brachiopods that dwell in shallow waters of a cold region may live also in the deeper waters of a region with a milder climate. This condition has been indicated by species of Gtryphus and other modern genera that are now found in the deep waters of the Atlantic. In Miocene time these species inhabited the Mediterranean. Theee facts have been taken - :. to indicate that in Miocene time the Mediterranean received cold waters from the Atlantic (Fischer and Oehlert, 1890). . ' Position of the fossil in the rock.—When the student can be sure that a fossil has been found in its original position of growth, such a discovery gives definite knowledge of life habits. But it is difficult to be sure that a fossil has actually been entombed in its natural posi- tion of growth. Waves and currents play many tricks in sorting and ar- ranging fossils. In the Upper Devonian of New York the writer has seen large lenses of brachiopod shells consisting almost wholly of the ventral valves of Cyrtospirifer. Most brachiopods are heaviest at the beak end or posterior of the shell, hence many dead brachiopod shells will lie on the bottom with their beaks on the mud but with the anterior portion off the bottom. However, when a hinged brachiopod is found with its inter-

area horizontal or parallel to the bedding planes it is suggestive evi- dence that the shell is in its original position of growth. i The sandy shales of the Hamilton group of New York have yielded Lingulas in an upright position with the anterior margin up and the pos- terior margin down. The occurrence of Ps3udollngula'in this position in • the Dubuque beds at Dubuque, Iowa, is also well known. These and other similar occurrences of lingulids have made it clear that the life habits of this group have probably not changed throughout time. Sardeson (1929) has described interesting occurrences of brachiopods in their position of grovrth in the Black River sediments of MLnnesota0 Here Valcourea. a conyexi-concave brachiopod, occurs in a nearly upright position with the convex dorsal valve lying obliquely over the ventral valve. Hesperorthis is found in the reverse position, with the convex ventral valve lying obliquely over the flat dorsal valve. In each in- stance the animal rested on its broad interarea and was anchored by a pedicle. In the same layers Sardeson discovered countless numbers of a certain species of Sbrophomena lying on the bedding planes. These resent- bled Valcourea in form but had a small, thread-like pedicle* From this evidence Sardeson concludes that Valcourea was a bottom-dweller but, Strophomena may have led a pseudoplanktonic existence. '.. '.', Most wide-hinged forms with a broad interarea that have been found in position of growth, lived with the interarea cloraly appressed to the object of support. Cyrtina, Platystrophia and Hesperorthis are examples, Teichert (1930) has shown, in his study of Porambonites, that in- complete filling of a brachiopod by matrix may yield a clue as to its former life-habits. Teichert illustrates a large Poranfcgnitejs filled with mud at the posterior end but by clear calcite at the front, the junc- tion between the two types of filling forming a sharp line. When this line is brought into a horizontal position, the life' posture of the shell is indicated, .which in this instance showed the animal to have lived in . an almost upright position. Teichert's evidence,, however;, might have been interpreted as indicating a dead shell held upright by gases of decomposi- tion with the light anterior up and heavy posterior down. The habit, of growth of cementing forms has long been known. Craniids are often found attached to corals, bryozoans or other shells. Cementing strophomenids, young and old, have been found clinging to corals or other objects. Schuchertelia has been found in clusters in the Hamilton of Ontario and Michigan. Other shells,.such as Strophalosia may show a cicatrix of attachment. Often this scar shows the"plication pattern of the supporting.,shell with sufficient clearness to allow identification of the host. ..-s < '.'•''

-36- Associated fossils^—Not: inJfreguent'ly the associates of a brachio- pod or group of brachiopods indicate the nature of the environment. The association of brachiopods with large corals is an obvious example. In the Alpena formation of Michigan a .great.variety of brachiopods occurs in and about, the giant Prjsaatophyllum reefsV- Such reefs are an ideal habitat for brachiopods because the waters are warm, aerated, arid lighted. Caves and grottoes in the corals.give.ample protection from the waves. In certain 3-ayers of Devonian and Carboniferous rocks brachibpods have been found associated with abundant thin—shelled clams, ostracodes, and plant fragments. This association suggests very close-shore deposits and probable brackish-water environment. As clear as such evidence seems, the student must beware the possibility of the brachiopods having been drifted into position with the other shells and plants. Waves and cur- rents may bring many animals after death into an association which did not,, or could not, have existed in nature. • ' '-•• • : Enclosing sediments.—To deduce the brachiopod habitat from en- closing sediments is a task fraught with difficulties and dangers. Geolo^ gists are not all agreed on the conditions of deposition of certain types of sediments. Furthermore, the point act which a brachiopod is found may not be the one at which it lived, nor necessarily near its actual abode.' It is also well known that the gradation of sediments away from shore, classically assumed to be from coarse to fine, is more complicated than once supposed. The grade or degree of coarseness of a sediment is not a reliable .clue to its environment of deposition. From paleogeographical considerations it would also appear that old ideas regarding limestone and black shale deposition must be revised. Some limestones by their geological relationships indicate that they were rapidly deposited near shore. ;. • ' . .•.In general brachiopods in a coarse sandstone suggest a near-shore, perhaps littoral zone. The entombed brachiopods may not have lived near the shore but may have been cast up by currents and waves from habitats farther offshore. Lingulids are a common form in'sandstones, particularly in the late Cambrian, and from their habits today would be expected to be the commonest forms in the near-shore zone. •• Heavy-shelled brachiopods have been commonly regarded as shore forms. The Oriskany fauna has been pointed out as a fine example. ^The Oriskany sandstone by its lithologic features and paleogeographic distri- bution is probably a far better indicator of shore conditions than the ' thick-shelled animals found in it because the Griskany fauna is one of large, strong-shelled individual^ regardless of its sedimentary environ- ment. The same heavy-shelled species are found in the fine-grained Little Saline limestone of Missouri and the Grande Greve and Perce limestones of Gaspe.

-37 - -• > • . •• A favorite habitat of many modern brachiopods is the rocky shore where individuals live in hollows and sheltered places on arid about the stones. In Puget Sound, Washington, :and at Eastpbrt, Maine, brachiopods 3ave in the tide zone, where they are left out of water'at low tide. This sort of environment .would be represented by conglomerates., but it. is rare indeed to find brachiopods preserved; in such a matrixi, ,.'.,,'V . •-.... ;./ • . '.r , i' ... . '• -Brachiopods are abundant in the finer sediiierits in most Paleozoic formations. The ecologic relationships of brachiopods found in the fine muds cannot be determined without difficulty. It might be thought that these muds represent off-shore deeper-water-sedijaenb^-but paleogeographic evidence often determines them tb be of near-Shore' origin.' Often such- muds are found, on the flanks of reefs in shallow water. Corals associated with brachiopods in very-fine muds point to shallow water. .'. Much has been written on the environment of deposition',of black . shale. Most authors agree that the bottom conditions were hot hospitable to normal faunas, but few authors agree on the depth at which the shales were deposited. Were they off-shore deep-water deposits or near-shore sediments? It is probable that no generalization will suffice for all black shales; the bathymetric level and conditions of each one mtist be de- termined by its own pale©geographic distribution, contained faunas and any other evidence available. Most Paleozoic black shales contain at least a few brachiopods, mostly lingulids, discinids, or thin-shelled rhynchonellids. The black, shale fauna has been regarded by Ruedemanri (1934) as chiefly planktoniCj. but two of its important forms, by analogy with modern brachiopods of the same type, are bottom dwellers only, the lingulids arid rhynchonellids, The presence of lingulids, which could not possibly have lived in the plankton, is a most forceful indication that these shales were deposits'/ * in shallow water and probably near the shore, • ' . . ".. '. ' '• (;•,•••• Limestones are usually fine-grained sediments and have been con- ventionally regarded as deep-water or off-shore deposits- But the pres- ence in some limestones-of pebbles of quartz or igneous rocks, and intra— f'ormational conglomerates argue for shallow-water deposition, at least' ., for those deposits. Here again each occurrence of limestone niust be weighed individually, with all available evidence, before the environment, it.represents can be determined. .A - ' • '• ! • • . ' ' ". ' „... . Some limestones are composed almost wholly of broken shells, '. rolled corals and other animal debris.- These may have been formed at '.. times when'the bottom-was so' stirred by waves arid currents that fine mate- rial could not settle and was carried away> but the- heavier shell debris remained. The Tichenor and Portland Point limestones of the-Hamilton" group of New York, which are composed chiefly of shell debris, are examples.

-38- : .. .,'.. The environment of deposition of most Paleozoic deposits seems to have been in water less than 100 fathoms deep. Most authorities agree: that the Paleozoic seas did not exceed this figure and some maintain that the .seas were not deeper than 200 feet (KLias 1937). Most Paleozoic de- posits crop out on the margins of uplifts which have brought up only the near-shore regions, but even where Paleozoic off-shore zones can be demon- strated, their fossils, current and wave-markings usually indicate shallow water* v ••. •;. • •.',.• Paleogeographic feature s.—Paleogeography is often a great aid to studies in Paleoecology because it enables a student to outline a basin of deposition, locate its probable shores and oceanic connections. If the study of fossils and sediments is inconclusive or yields conflicting evi- dence, report to paleogeographic data may indicate the ancient environment. For example, thinning of the Hamilton shales westward in Erie County, New York, and the development of layers of concretions and shell breccia, point to a shoal or land on the site of Lake Erie. This ancient positive area was called the Buffalo Axis by Grabau. This region of the Hamilton sea was formerly regarded as a deep-water environment but the facts as now interpreted point to shoal water deposition of the Hamilton black shales and blue calcareous shales of western New York. : ••... -.- . - , .-,•;•• Brachiopod Adaptations . Anyone who has studied bachiopods or collected them, will be im- pressed by the fact that different stocks at different times, develop the same or similar forms. This homeomorphy has been interpreted in some quarters as adaptation to environment, but study indicates that adapta- tion is not the whole ; story. Another school favors an orthogenetic process as an explanation for the phenomena. It has also been suggested that such parallelisms are entirely fortuitous. Only a few combinations of charac- ters are possible in brachiopods. Therefore it is inevitable that many characters will be reinvented. Many of the developmental trends to be discussed below may be inter- preted as more or less directly tending to improve or maintain the animal's ability to bring currents of water into the shell. This is the most im- portant function of a brachiopod because the currents bring life-maintain- ing food and oxygen, Brachiopods that live above the bottom on stones or corals have no great problem in bringing in the necessary currents, but brachiopods that live free or anchored on the mud have the problem of keep- ing the margin away from the bottom. If the margin is covered by mud the animal is likely to perish from suffocation or starvation. Thus many adaptations to keep the margin above the mud and to facilitate entrance and exit of currents are known. ,.:'.••.

- :- 39 - , By their form many brachiopods are adapted to ..keep their margins above.the 'mud if 'they v are torn free from the place 'of attachment. The posterior or umbonal portions of one or both valves are very heavy and thick when compared to the anterior portion. If the shell sinks in the water it will fall with the beaks down and-will lie on the mud with the heaviest or ventral valve on the mud and: the front margin oblique to the bottom. Round or ovoid shells like Gryjafnis yitreus can be rolled about on their posterior by currents,• and the; front margin will never touch the mud. Some shells., Daviesella and Gigantella.. must have relied mainly on the weight of the posterior part of the ventral valve for anchorage, The dorsal valve then serves as a lid. • The development of a ponderous ventral valve.was carried to extremes in .the generd Richthofenia and Prorichihofeniar .. • It is impossible at the present time 'to say why'certain types of brachiopod .shells were .developed. .The modern brachiopods show only a few of the known trends of the Paleozoic. Man^ Paleozoic types, therefore, cannot be compared with any recent forms, hence remarks on their ecology must.be regarded as tentative! until more positive data "can-be collected. In discussing some of the'known adaptations of the brachiopods the writer has .selected the published views that 'seemed most reasonable to hinu The adaptive trends here considered are as follows: folding, ILpbation, plica- tion, cementation, alation and mucronation, elongation^ compressed form/' resupination, reversion, spinescene, geniculation and punctation. Foldin^„—All stocks of articulate brachiopods tend sooner or .••' ' later to develop a strong median fold. In the Paleozoic the fold usually • takes the form' of a strong median plica that undulate'si the interior com- missure or line of valve junction. The folding of the commissure may take place either in a ventral direction or in a dorsal'direction. The prevailing condition is a dorsal fold, but a ventral, fold occurs in a few genera. .- • ,""i." -v' '• •"'.' In young brachiopods or in early genera of certain stocks the v5n-r tral valve is gently folded in a ventral direction Later development, as in Finkelnburgia. leads to loss of the ventral fold and dorsal sulcus to produce a secondarily rectimarginate or straight commissure. In many brachiopods, however, the sulcus is present in the dorsal valve in young stages but as growth continues a well-marked fold develops from the sulcus. Examples are Eridorthis andVirglanAo Two types of folding are now recognizedt an opposite fold and an alternate one. In the former type a fold or sulcus on the ventral valve is opposed by a fold or suJeus on the dorsal valve. The anterior com- missure thus remains rectimarginate but the ventral or dorsal profiles become lobate. Examples of opposite folding ares Pentamerus, £hi£idium, Zeilleria, and Digonella. Alternate folding is produced when a fold in one valve is opposed by a sulcus in the other. This is the more common

-40 - type, of which Platystrpphia or Enteletes will serve as good examples. In instances of alternate folding the anterior commissure is thrown into one or more folds. Orton (1914) has presented the view that development of a median fold produces a trilobate shell, thus facilitating the ingress and outgo of the water currents that aerate the mantle and bring in food. The in- coming currents in spiriferids enter by the median fold of the shell and the unclean water leaves by the lateral flanks„ Folding apparently had little to do in determining the life posi- tion of a shell except where the brachiopods lived in mud. This was not true, however, of shells folded in a ventral direction. These must have been attached with the dorsal valve below because in most known sulcate (anterior commissure folded ventrally) brachiopods the ventral beak is more or less curved over the dorsal umbo. Lobation.—This trend, which is of distinct value in separating the incurrent from the excurrent streams is usually incipient in all folded brachiopods but has been carried to extremes in a few instances. Lobation develops in oppositely and alternately folded brachiopods. Pen- tamerus and Rhipidium tend to develop an elongate central lobe at the front of the valves which thus brings the excurrent channel well forward of the receding flanks of the shell where the water enters. In Spirifer, according to Orton (I914j p. 295)» the condition is reversed, the currents containing oxygen and food enter the front, medial portion of the shell and the currents containing the products of metabolism leave by the flanks* The most extreme instances of lobation occur in Pygope and Pygites.. In young stages of Pygope a strong fold develops on the ventral valve, producing a deep, wide sulcus and flaring flanks. In Pygites the flanks are greatly elongated with growth, and often grow together anteriorly to leave a hole in the center of the valves. The ventral fold of these "keyhole brachiopods" is directed obliquely ventrally, thus directing the incurrent canal far above and posterior to the excurrent lobes. Plication.,—By plication is meant the development of major folds in the shell. This tendency has developed in many different brachiopods, the punctate orthids, strophomenids, and terebratulids. Late-derived mem- bers of the strophomenids and orthids in the Pennsylvanian and Permian periods developed strongly plicated shells. Examples are: Enteletes, Kiangsiella and Meekella, No other advantage than increased shell strength appears to the writer to have accrued from this development. The wide- spread and nearly simultaneous development of plications in these stocks may be an expression of phylogerontism because all of them disappeared with the Permian. The trend may, perhaps, have been induced by world-wide ad- verse conditions such as a slight increase in salinity due to removal of water from eperic seas to form the growing Pennsylvanian and Permian glaciers.

-41 - Cementatioru —When one mentions cementation in connection with brachiopods he naturally thinks of the craniids. The various genera of this family have been cementing forms as far back as they have been found~ in the Middle Ordovician. Their ecology apparently has not changed and need not be further considered. A number of secondarily attached genera are known which may be divided into tiro groups: one that is attached throughout life, and another which in later life may break free and lie on the sea-bottom. * .' Beginning with Liljevallia in the Silurian, strophonenids cement- ing by the entire ventral surface of the ventral valve persist into the Devonian, where they are represented by Irbjp^kites and Davidsonia0 With the advent of Productella in the Middle Devonian two aberrant genera ap~ pear and persist into the early Mississippian. These genera are Legta- losia and Etheridgina, and the two are .pharacterized by cementation of the ventral valve by its ventral surface to corals or other objects,, In addition to this means of attachment peripheral spines also serve 'to anchor these little shells. Etheridgina often grows on crinoid stems ! in such a manner that the anchoring spines appear to wrap around the stem. Many genera are known that are cemented in early stages of growth but, because of their large size, later break from their attachment and lie free on the bottom, Schuchertella, Derbyj-a, Strophalosia and Old- hainina are examples of this group. In much the same category are brachio- pods having the form of cup corals, such as RJchthofeniai. These types were only evolved in Pennsylvanian and Permian times, They, were derived from strophomenid ancestors at the twilight of the Protremata,, Alation and mucronat ion.—Lateral extension of the hinge to form wings or ears is a tendency developed in many different groups of brachio- pods. It may occur as an adult character or in youthful forms only. Argyrotheca johnsoni Cooper, from the West Indies, has a wide-hinged, alate form in its young stages, but' the adult has almost rectangular car-- dinal extremities, Many strophomenids of the Ordovician and Devonian developed alate shells. The development of a wide hinge is uncommon in modern brachiopods but among the spiriferids this development reached its maximum. It is apparent from the structure of the strophomenids that some were attached by a slender pedicle but others, such as Stropheodgnta which has no functional pedicle opening, lived free on the bottom. Such forms would be able to develop the hinge to its limit. For prone shells auriculation or mucronation would readily serve to keep the animal on the surface of the mud and from sinking into depressions. It would also serve to prevent currents from upsetting the shella

- 42 - ..... 'the development of symmetrical alate forms could not have taken .place in shells tightly affixed to a hard'and irregular substratum. Spirjfer micronatus is one of the most mucronate brachiopods known. This and allied species may be collected in New York, Ontario, and Michigan. The writer has collected many hundreds of them but has seen comparatively few unequally developed or distorted individuals. This leads to the be- lief that these brachiopods were not attached closely to a hard substratum. Not only the symmetry of the shell but the strongly incurved beak would make, close attachment to a hard substratum difficult. Because the animal possessed a functional pedicle opening it is believed that Spirifer mu- cronatus was attached by a pedicle of moderate length anchored in soft mud, with the umbo of the dorsal valve resting on the mud and leaving the extremities free to develop laterally. These spirifers may have lived where currents were active. The mucronate form would tend to serve in the same manner as a weathervane, always turning the shells on their pedi- cles so that their long axis was parallel to the direction of the current. Thus the force of the current working against the narrow side of the shell would be unable to uproot the animal and the naicronate extensions would prevent the shell from being driven into the mud. Mucronation or alation may be an orthogenetic trend, because many different stocks of spiriferids have developed the character. Most of these have received generic names. Thus we have Mucro'spjrifer. Fusella. Cyrtospirifer. and Rastelligera. a mucronate development of Spiriferina. the punctate spiriferidc Elongation*—This is an adaptation developed by a few brachiopods having delicate pedicles. Onychotreta and Terebrirostra are the two most extreme examples. The two genera are widely separated by time, the former having lived in the Silurian and the latter in the Cretaceous, yet they have developed identical external forms. Both genera lived in fine lime muds. .';••:-.• It has been suggested by Yakovlev (1908), that Terebrirostra lived with the beak in the mud and the extremely long ventral valve kept the anterior margin well above the surface of the mud. Dacque (1921) has suggested that elongation is an aid to stiffening the pedicle. These forms lived with the ventral beak in. the mud, anchored, perhaps, by a fine pedicle split into many fibers at its extremity. Compressed form.—According to Lament (1934) water immediately in contact with a mud surface is normally very poor in oxygen. Hence, brachio- pods of compressed form, like Strophomena or Radinesquina, have a maximum of oxygen-gathering tissue exposed to the water. This condition enables the animal to get the greatest amount of oxygen from a small amount of water. The early representatives of these brachiopods were provided with a functional pedicle and probably lived lying on the bottom or attached

- 43 - in the usual manner. The later compressed brachiopcds, such as Stropheo- dpntaf had no pedicle, Strophe_pdonta was more or less deeply concave and may have lived1 with its ventral surface stuck tightly on the sticky clay in which it is usually found. .The mud is sufficiently tenacious to pre- vent the shells from being overturned.. If overturned, it is possible that Stropheodonta and other compressed forms, like Cnonetes. may have had setae strong enough to have been useful in restoring the animal to its normal position. Resupinatiqn,—Everyone familiar with brachiopods has been 1m- pressed by the phenomenon of resupination, in which the young shell possesses a convex ventral valve and a flat or concave dorsal valve, but in maturity the condition is reversed, the anterior of the ventral valve becoming more or less deeply concave and the dorsal valve becoming strongly convex. This appears to have been a derived tendency, because brachiopods more commonly have a deeper ventral valve,. .Examples of resupinate brach- iopods are Strophomena. Schucheretella and-Chonostrophia. i •' \ Resupination would be an advantage to compressed types that lived free on the bottom, lying on their ventral valves. The anterior margin would be lifted well above the surface of the mud and the hollow on the ventral valve just anterior to the beak would effectivly prevent the valve from being overturned. According to Lamont (1934, p. 167), radial ornamentation, but more particularly concentric rugae which are commonly -developed in compressed shells, would prevent slipping in the mud and sinking of the lateral margins into the mud when the valves were opening during feeding. ••••...,., Reversion.—This term is applied to the. rare instances in which the anterior commissure is folded in a ventral direction, producing a fold on the ventral valve. This condition is rare but a number of genera are known which are reversed counterparts of more common genera* Examples are? Brac.hyjiimulus of the Silurian, Anabaia of the Devonian, Parenteletes in the Pennsylvanian, Entelejbina and CamGj^^UojrLna. in the Permian, Korella in the Trias sic, Nucleatula in the Jurassic, and flecrghynchi a and 'Abj-s^- thyris in present day seas, .• " " Although all of the genera named would be difficult to separate on 'the basis of an examination of the exterior, the animals probably did not all live in the same manner. BraehvmmiTujs has a minute foramen situated :'at the apex, suggesting that this little brachiopod was attached with the dorsal valve down, thus bringing the anterior margin well above the bottom, The other genera were undoubtedly attached to shells or other objects by a short pedicle in the usual manner of rhynchonellids and terebratulids0 No particular advantage to its possessor seems to be apparent in the known instances of reversed fold and sulcus. 1. This idea was suggested by Dr. J. P. E. Morrison of the U. S. National Museum.

-w- '....' . Spinescence.^-Spines have been developed independently In many different- stocks of brachiopods from Cambrian time to the Recent.. Spines- irt some forms, such as SquamulariaV'are developed as a part of the" orna- mentation and play no apparent part in the life of the animal. On the • other hand, hinge spines arid long, strong spines scattered over the sur- face, as in the productids, appear to have played an important role in the habits of the animal. Nowhere among the brachiopods has evidence been discovered to prove that spinescence indicates a phylogerontic stage. The Chonetids and productids, once initiated had a long and flourishing career. ••"... :i. • -...-- • . .. \- Hinge spines appear first in Eochonetes. which must have developed from Sowerbyella in late Ordovician time. The spines on the hinge'of Chonetes were developed to all degrees, some are short and blunt but others, as in the group of Chonetes emmetensis» are exceedingly long. Such long spines could have served to anchor Chonetes by becoming entangled with submarine seaweeds. Shorter spines have been explained as. anchors to hold the shell upright in the mud, but most of them seem too short to have been effective holdfasts. Chonetesmay have lain on the sea-bottom on its con- vex ventral valve, and the oblique spines may have been an important aid in preventing the shell from being overturned by currents. ... . . • Productella and the later productids have the common feature of. '.. • spines scattered over the body of the ventral valve as well as along the posterior margin. Many genera of productids have been separated on the basis of their ornamentation. The many types.of ornament naturally sug- gest that these shells had different habits of life. Many of the productids are not well known but a study of a few types will give some ideas as to their mode of life. • •••' ' •-.. .. . - Silicified specimens of Productella from the Devonian of Nevada are ornamentated along the hinge of the ventral valve by long spines that curve in an. antero-dorsal direction over the concave dorsal valve. Spines along the anterior border curve postero-dorsally to overhand the dorsal valve. Such spines curved over the dorsal valve and towards the center . of the anircal, will keep the shell above the surface of the mud regardless of the position of the valves. If the shell is thrown up off the bottom by a current, it will make no difference to the animal it settles with the ventral or the dorsal valve down. The curved spines will keep the shell off the bottom as the legs of a water-strider keep their owner's body on the surface. The dorsal valve of Productella carries no spines, consequently it is free to open regardless of the position of the animal on' its spines. In the U. S. National Museum a specimen shows many indi- viduals of Productella entangled by their spines. Even in this tangled mass the dorsal valve had no difficulty in opening. Thus seme productids may have lived on the sea-bottom as a spongy mass of shells held together by interlocking spines. v

Many of the later .productids have: a construction similar to that of Productella and are provided with similarly situated spines. Muir- ' Wood (1928, p. 26) states that Dictyoclostus lived with its ventral valve lying over the dorsal valve. Moore (1929, p. 469) supports this conten- tion. It seems likely that the productids seen by Muir-Wood and Moore Were supported above the; muddy bottom on which they lived by spines in the manner described above„ If they were not, the animal must surely have perished because it could not have functioned with its entire margin in the mud. In productids with long hinge-spines only it is possible that the animal lay on the bottom on its ventral valve which was by far the heavier• Long hinge-spines extending posteriorly would prevent the creature from 'being tipped over onto its dorsal valve, Marginal frills, such as those of Atrypa. may have served their possessor in the same manner as spinea- '.' to keep the valves out of the mud. :.-i. • i- ' * ' ', '• '••.-. r ' Geniculation.-r-Various degrees of geniculation have been developed in all stocks of the thin-bodied or compressed brachiopods, such as Rafinesquina, Lejjtaena, and Productus9 Most of these compressed forms live on mud. Thus the geniculation seems to be a necessary development to keep the margins of the shell above the surface of the mud- In the productids geniculation is carried to an extreme, the front of the valve being produced into a sort of siphon, as in Prob'oscidella, Punctation<.—The function of punctae in the inner layers of a brachiopod shell is still problematical. However, it:. seems clear that punctate branches of the articulate brachiopods were more vigorous and long-lived than the impunctate lineages. The earliest known punctate brachiopods are dalmanellidsj, which appear in the Chazyan or lower'Mid-- . . . d1e Ordovician. These :da.\manellids flourished throughout the remainder" • v of .the Paleozoic, outliving the impunctate orthids by several periods. .•;<.•: It is not possible to prove whether punctae developed once or several times. It is possible that the dalmanellids gave rise to all other punctate forms and that these developed series paralleling those of the impunctate stocks. The punctate spirifers outlived the impunctate ones and today the terebratulids are the dominant race of brachiopods, with the rhynchonellids represented by only a few genera and a handful of species, . • Form and Size of Pedicle Among recent articulate brachiopods nearly all species have a short pedicle. The pedicles vary slightly in length but even the long-beaked . forms are anchored tightly by short pedicles. Of all modern brachiopods" ' only jjhlidonophora, an abyssal species, is noteworthy because of its un~

- 46 - - usually long pedicle. Chlidonophora is a small, subcireular brachiopod with a lenticular profile, suggesting a Paleozoic dalmanellid by its form. The pedicle is almost as long as the animal and its end is divided into many long, slender fibers. These entwine foraminifer shells and anchor the animal in the same manner as the roots of a plant. It is likely that many bottom-dwelling brachiopods of the Paleozoic may have had such a pedicle. For example, some of the brachiopods having small foramina may have had pedicles with divided distal ends. Such a pedicle could have effectively anchored most brachiopods to a muddy bottom, ...-•••: . Brachiopod enemies.' ** '.. • >"'.'•' -• There is little direct evidence to indicate that Paleozoic brachio- pods served as food for such animals as the fishes, cephalopods and trilo- bites. Howevery:if one considers their enormous numbers in the Paleozoic they must have been a prolific source of food, if not in the adult form, certainly their eggs and larvae must have yielded many a feast. Direct evidence indicates that snails equipped with a radula, actually bored brachiopod shells and devoured the succulent tissues within. The earliest example of this molluscan habit known to the writer was found in the Rich- mond (Fenton and Fenton 1931)* This early custom is still in vogue be- cause Jackson (1918) and Dall (1895) record instances of modern brachiopods having been bored by snails. In modern times man has added himself to the list of brachiopod enemies. The natives of the Japanese and Philippine Islands relish the pedicle of Lingula. •• . Embroyology and Distribution ' The young of brachiopods have a free-swimming stage before they finally settle to the bottom for life. Very little is known of these young stages, in fact, they are known in detail in only four genera, . • Argyrotheca. Lacazella, Terebratulina and Lingula. Sach of these genera represents a different large major division of the brachiopods. Observa- tions have been made on a few other genera, but too little is known to permit much generalization on them. It has been long recognized that the chief means of dispersal of brachiopods is by currents during the free-swimming stages. But there are difficulties in the way of a..complete understanding of the process. It has been discovered that the known larvae of :the inarticulates differ from the larvae of the articulate brachiopods. In the former the pelagic larvae are provided with a mouth and functioning stomach, allowing them to live for some time in the free-swimming stage. Larvae of Discinisca and Pelagodiscus have been recognized in the plankton. The known larvae of the articulates do not swim after the development of a functioning stomach. Their free-swimming period is thus short, 10 to 12 days in Terebratulina, and they settle not far from their place of origin.

-.47 -... ... Two obstacles to dispersal are, therefore> apparent. In the articu- lates the free-swimming stage is short, thus limiting dispersal. In the inarticulates, although, the larvae are better adapted to longer free- swimming existence, most of the species live in shallow water only. There- fore, deep water and consequent cold temperatures are a barrier to their distribution. . . .- In the Paleozoic the seas were probably shallow, and there were probably no great depths in the geosynclines to form a barrier to dispersal. Nevertheless, there is evidence to show that species were localized then as now. In the Devonian-'the equivalent Hamilton (Centerfieid) faunas of western New York, Ontario, McMgan, and Indiana contain species peculiar to these areas. In Michigan and Indiana many of the rare species dwelt on and about the coral reefs. Adjustment to the peculiar conditions of reef life may have been the. controlling factor in their Iocalization0 In all periods of the Paleozoic, .local areas characterized by definite assemblages are known and contemporaneous faunas nearby may contain many different species. The reasons for such localization will make inter- , esting ecological material. .. . Allan (1937) has published a note on an overlooked phase of brach- ' iopod migration. He has discovered the young of two species of 'brachio- pods attached to the free-swimming Chlamyji radiatus .(.Hutton). This is a member of the. Pectenidae which contains species known to make migrations. Although the point is not proved, Allan suggests that this may have been a means of distribution. Paleozoic brachiopods have been found attached to mobile forms such as cephalopods, and trilobites, but it is usually difficult to prove whether or not the brachiopods were attached during the life of the 'swimmer or after the creature had died. The latter seems'"• the more likely.", Color Anyone seeing a large collection of recent brachiopods for the first time will be struck by the beauty and high color of some of the species. Perhaps j&he most beautiful species is Argyrothec^ barrettiana (Davidson), with its straw yellow costae and crimson interspaces. The terebratulids are the most highly colored modern brachiopods, the colors ranging from pale yellow through salmon to pink and 'crimson. The recent • rhynchonellids are drab shells of brown, pale bluish-gray and black. Some linguloids are highly colored by bright or dark green mixed vdth rich brown. Most colored brachiopods are dwellers in shallow water, a feature that is true of other groups of animals as well as the braehiopcds. • It is generally true also that, as'deeper water is; approached, colored shells, become fewer and fewer in number. Most shelled invertebrates of the deep waters have thin, white or translucent shells. Forbes (1854) has stated

-48 - that, "In the Mediterranean only one in IS of the shells7 taken from below 100. fathoms exhibited any markings of colour, and even the few that did so, were questionable inhabitants of those depths. Between 35 and 55 fathoms, the proportion of marked to plain shells was rather less than one in three, and between the sea-margin and 2 fathoms the striped or mottled species exceeded one half of the total number". • ' In studying the recent brachiopods in the Uy S. National Museum the writer has found that most of the colored species were collected from shallow waters. A feiif colored species are recorded, however, i'rom con- siderable depth. -One specimen of Argyrotheca barrettiana (Davidson) was taken from 805 fathoms but it is not known whether the animal was alive or dead when dredged. Color-marked fossil braehiopods are of very rare occurrence. A few specimens have been taken from the Paleozoic and a few from succeed- ing periods. The oldest known specimens of color-marked brachiopods are from the Middle Devonian in Europe and the United States. Most fossil brachiopods showing traces of color are terebratulids and the usual pat- tern is one of radial bands with or without a gentle curve towards the front margin. Davidsonnias figured specimens of Dielasma showing the more common type of color mark. Living Laqueus rubellus (Sowerby) from Japan and Hawaii is similarly marked. The usual traces' of color 5jv fossil bpachiopods show the pattern in light or dark gray and usually give no hint as to the original color, < Brachiopods showing traces of original color are known from the Cedar Valley of Iowa and Illinois. The writer and Preston £. Cloud, of the U.S. National Museum, collected several specimens of Cranaena having four or six straight red stripes radiating from the beak to the front margin. Other specimens taken from the same deposits and those figured by Gleland have the same pattern but do not show the red color. The red-marked fossil species and predominant red colors in recent terebra- tulids suggest that this color prevailed also in the fossil forms. Richter (1919) has pointed out by analogy with recent forms and on the basis of Forbes' remarks that,i colored brachiopods in ancient sedi- ments are excellent indicators of shallow, sunlit waters. 1. Brit. Foss. Brach., pt. V, Carboniferous Brachiopoda, Palaeontograph- ical Soc., London, p. 13, pi. 1, 1858-1863. 2. tdsc. Geol. Nat. Hist. Surv., bull. 21, p. 73, p1. 13, figs. 8, 9, 1911. ':• . '.

-49 - • ••••' Pathology . . '....' •. • .".•' Pathologic brachiopods have been recorded many times, but most of the figured specimens that have been interpreted to be pathologic appear to have attained their distorted condition by accidents during growth or unfavorable conditions of growth- Distorted brachiopods are common and are produced under crowded conditions of growth/ Brachiopods'. often grow in clusters or in crannies in corals so that growth of one side or the other may be seriously impeded, Specimens of spiriferids may be found with the mucronate points of only one side developed. Rhynchonellids of the Paleozoic and Jurassic often are unequally devel- oped on one side or the other. These malformations appear to have been produced by crowding. One extreme instance is shown by a specimen of Rafinesquina from Cincinnati, Ohio, in the U. S. National Museum. The front margin of this specimen had impinged against a branch of a small bryozoan and had grown completely around it. Only one example of a diseased brachiopod is known to the writer. This is a specimen of Cariniferella tipga (Hall) from the Chanting of south central New York, now in the U. S, National Museum, showing only half of the muscle scars normally developed. One adductor and the large diductor and adjuster scars are represented only by a small irregular spot. The exterior of the specimen is perfect, indicating that some internal cause must have been responsible. Conmensalism and Parasitism Many instances of commensalism are known in fossil brachiopods. Modern Terebratulina is often found encased by a brown sponge. Bryozoans, worms and other animals often are attached to brachiopod shells, Yakovlev (.1926) claims that encrusting Aulopora served its host advantageously by the presence of sting cells which protected coral and brachiopod alike. Pent on (1932) described a brachiopod, Te_rebratalia transyersa caurina (Gould) living inside the shell of a large gastropod, Arg•qbucc_inum oregonense (Redfield), The brachiopod larva had entered through a rent in the mantle of the shell and grown to considerable size in this unusual environment. Although Penton regarded this association as parasitic it seems rather to have been accidental«, Conclusions Brachiopods are a minority element of modern faunas, but in the Paleozoic and Mesozoic they were very numerous and at times the most abun- dant form of life. With the exception of the lingulids, modern brachiopods have too wide a bathymetric range to be of use in determining the depth of seas older than the Tertiary.

- 50 - Life habits of groups Represented by fossil species and by forms now living probably did not differ throughout, time. life habits ascribed to extinct forms, unless these forms have b,eeh. found in their living positions, must be regarded as speculative.; ./ ! ' :. Aids to the study of Paleoecolo'gy are: (l) Analogy with Recent forms; (2) position of the fossil in the rock; (3) associated fossil forms; (4) the nature of the enclosing sediments; and (5) paleogeography. Some trends of adaptation during past time appear to have been in the direction of increasing the ability to get food and oxygen. Too little is known of brachiopod embryology to permit generaliza- tions on distribution of free-swimming larvae.' Colored brachiopods in general indicate shallow, warm waters. Brachiopods are not known to have been truly parasitic but in- stances of commensalism are well known*

- 51 - "3i:- Selected-Bibliography ,i. :-;•..,.. T""1""^ ' . " .'; Allan, Ki±$t ;;?' Oh'i heglected factor in brachiopod migration. Rec. Canterbury MasV,Lvol. 3#, no. -3y ppv 157-165, 1937. Ashworth, J. H. On Larvae of Ljjigala and Pelagpdiscus ( Trans. Roy. Soc. Edinburgh, vol. 51, pp» 45-69, p1s. 4, .57~!I5i6. Beecher, C. E. • 'Studies in Evolution, Scribner's, New York. 1901, .* '*t "'• ' ' '"",*'•' •' Blochmann, F. Zur Systematik und Geographischen Verbreitung der Brachippoden. Zeitschr, f. wissensch. Zool., Bd. 90, pp. 596- , pis. 36-40, 1908;. v !i *-.-•• Clarke, John M.' Organid dependence and disease: their origin and sig- nificance. New York St. Mus, Bull,, nos. 221, 222, 113 PP-, 1921. Dacque, E, Vergleichende-biblogisChe Formenkiinde; des fossilen niederen Tiere. Berlin, 192li •' Dall, W. H. Report on the brachj.opoda obtained by the United States 'Coast Survey Expedition in charge of L, F, de Pourtales, with a revision of the Craniidae and Discinidae. Bull. Mus0 Comp. Zool. 'V^ .'."'." Harvard, ;Voli 3, no. !„• pp." 1-45, 1871. ^ Scientific results of explorations by the 'U . S, Fish Commission ' steamer "Albatross". No. XXXIV, • •• Report on mollusca and brachiopoda dredged in deep water, chiefly * :'' ' near the Hawaiian Islands, with illustrations of hitherto unfig- ured' species from northeast America ^ -Proc. 00 S^-Nat. Mas., vol. •'• '17, pp. 713-729, 1895. Annotated' list of the recent Brachiopoda in 'the 6611ecti6n of the United States National Museum, with descriptions of thirty- three new forms. Proc. U. S• Nat. Mus., vol. 57, pp. 261-377, 1920. * Davidson, T. • Monograph' -of Recent "Brachiopoda. Trans. Linn. Soc,, ... . ser. 2, vol, 4, Zool., 1886-1888. •"-••" ::' •• -Report -on- the- B-rachiopoda dredged by H. M. S.-, "Challenger" during the years' 1873-1876; Voy.- Challenger, Zool;,, vol- 1, 1£00• ' On the families' Strophomehidae and Productidae. Geologist, vol. 2, pp. 97-117, 1859.- IJu Bois, H. M. Variation induced in brachiopods by environmental con- ditibns. Trans.' 111. Acad.' Scl,i'vol. 9, pp. 225-226, 19l6. Elias, M, K. bepth of deposition of the Big Blue (Late Paleozoic) sediments in Kansas. Bull. Geolv'Soc^ Amer,, voli 48, pp. 403- 432, 1937* ' r'r> ^yk' Fenton, C^ L, A parasitic brachiopod. Nautilus, vol. 46, pp. 52-54, 1932.

- 52 - Fenton, C. L. and M. A. Fenton. Some Snail borings of Paleozoic Age. Amer. Midland Net., vol. 13, pp. 522-528, 1931. . . Alate shell lamellae and spines in' the genus Atrypa. Amer. Mid- land Nat., vol. 13, pp. 203-221, 1932. Orientation and injury in the genus Atrypa. Amer. Midland Nat., vol. 13, pp. 63-74, 1932. Fischer, P., and Oehlert, D. P. Sur la repartition stratigraphique des brachiopodes. Compte Rendu, CXI, pp. 247-249, 1890. Expeditions scientifiques du Travailleur et du Talisman pendant les annees 1880-1883. Brachiopodes Paris, 1891.'. Foerste, A.-F. The color patterns of fossil cephalopods and brachiopods, •with notes on gastropods and pelecypods. Contrib. Mus. Pal. Univ. Mich., vol. Ill, no. 6, pp. 109-150, 1930. Forbes, E. Note on an indication of depth of Primaeval seas, afforded by the remains of colour in fossil Testacea. Proc. Roy. Soc. London, vol. 7; .pp. 21-23, 1854. Jackson, J. W. Brachiopoda. Brit. Ant. ("Terra Nova") Exped., 1910, Nat. Hist. Rep., Zool., vol. 2, no. 8, pp. 177-202, 1918. Lacaze-Duthiers, H. Histoire naturelle des brachiopodes vivants de la Mediterranee, Ire Monographic, Histoire naturelle de la Thecidie. Ann. des Sci. Nat., Zool., ser. 4, vol. 15, pp. 260-330, 1861. Lament, A. Brachiopod morphology in relation to environment. Reprint .'. . from Cement, Lime and Gravel, May Issue, 1934. Lower Paleozoic brachiopods of the Girvan District; suggestions on morphology in relation to environment. Ann. and Mag. Nat. Hist., ser. 10, vol. 14, pp. 161-184, 1934. Moore, R. C. Environment of Pennsylvanian life in North America. Bull. Amer. Asspc. Petrol. Geol., vol. 13, no. 5, pp. 459-487, 1929. Morse, E, S. On the early stages of Terebratulina septentrionalis (Couthouy). Boston Soc. Nat. Hist., Mem. 2, pt. 1, no. 11, 1871. Observations on living brachiopods'. Mem. Boston Soc. Nat. Hist., vol. 5, no. 8> pp. 313-386, 1902. Muir-Wood, H. M. The British Carboniferous Producti. Hem. Geol. Surv. Great Britain, vol. 3, pt. 1, pp. 24-34, 1928. Orton, J. H. On ciliary mechanisms in brachiopcds and some Polychaetes, with a comparison of the ciliary mechanisms on the gills of molluscs, Protochordata, Brachiopods, and Cryptocephalous, Polychaetes, and

- 53- - an account of the:«ndostiyle: of-Crepidula and its allies. Journ. Marine Biol. Assoc. U. K0 (n.s.), vol. 10, pp. 283-311, 1914. Peterson, C. G. J. The animal communities of the sea-bottom and their importance for marine zoogeography. Rep. Danish Biol. Sta., vol. •- 2t, pp. 1-68, 1913. ::• ,!.-*• ,../: ..-. -.' : • • , , I 1 r 1 • -' -. t •'•••-' * '*i. '*.-*• *T, . , ' "f * ' . , • Richter, R. Ztir Fttrbung fossiler Brachiopoden, Senckenbergiana, Bd. 1, nr. 3, pp. 83-96, 1919. ?•• 7.." Ruedemann, R. Paleozoic Plankton of North America. Geol. Soc; Amer., ; Mem. 2, 1934. . .-. • / -*. -.-».'. • -. . Sardeson, F. W, ; Ordovicic brachiopod habitat. Pam. Amer. Geol,, vol. •"- 51, PP. 23-40, 1929. ---..-:. -. .."'-.. . ;: • -r Schuchert, C. Paleogeographic and geologic significance of recent Brachiopoda. Bull. Geol. Soc. Amer., vol. 22, pp. 258-275, 1911. ,:•-Morse on living brachiopods„ Amer. Geol,, volB 31, pp. 112-121, ••^1903< •;.'.;• . - Simroth, -H» Die Brachiopoden der Plankton-Expedition. Ergebn. Plankton- Exped., Bd. 2,-F.f., 1897. ' . Teichert, C. Eiostratigraphie der Poramboniten. N0 Jahrb. Miner, Geol., y& Palaont., BB 63, Abt. B, pp- 177-246, 1930, .. :.-.,• ... Thomson, J. A0 Brachiopod Morphology and.^Genera (Recent and Tertiary)* • New Zealand Board of Science, and Art, Man- 7> 192?. .... T Yakovlev, M. Die anheftung der Brachiopoden.als Grundlage der Gattungen und Arteh. M^m. du Comite Geol., n.s,,,. livre 48, PP" 25-32, 1908. , Parasitism, commensalism and symbiosis in Paleozoic invertebrates. . Ann. Soc. Paleont. Russv, Petrograd, vol. -4, pp* 113/-124, 1?26. .- ^ '--'--On-the development of Lingula asati^a,. Joum, ColX, Sci, -••'••• Tbkyo, vol, 17, art. 4, PP- 1-112, "l9Q2, ~ .. ... ...'., U. S. National Museum, V/ashington, D, C, • i-' : ••- ; ' r «.!•'. •' • I . • .f. * •"• • !•..'.. ' . .. ' ., ',;•;• VI -. i '