Atavisms and the Homology of Hyobranchial Elements in Lower Vertebrates

JOURNAL OF MORPHOLOGY 195237-245 (1988)

STEPHEN M. REILLY AND GEORGE V.LAUDER Department of Developmental and Cell Biology, University of California, Iruine, CA 92717

ABSTRACT The homology of branchial arch segments in salamanders has been a matter of controversy since the last century. Many investigators term the most medial paired elements of salamander branchial arches "ceratobranchials" and the next distal paired elements "epibranchials." This suggests that the first two segmental elements of the salamander branchial arch are not homologous with elements occupying the same position in ray-finned fishes, Latimeria, "rhipidistians," and lungfishes, in which these bones are called hypobranchials and ceratobranchials, respectively. Three lines of evidence suggest that it is more parsimonious to interpret urodele branchial arch segments as being homologous with those of other vertebrate clades-1) comparative osteology, 2) comparative myology, and 3) the discovery of cartilaginous structures forming a third segmental unit that we interpret as atavistic epibranchials of the branchial arch in one population of the salamander Note phthalmus uiridescens. These structures possess all the defining attributes of atavisms, and illustrate the special role that atavistic features play in resolv- ing questions of homology recognition.

For more than a century, detailed descrip- structures of the hyobranchial apparatus are tions of hyobranchial morphology in lower called basibranchials because they lie at the vertebrates have appeared in the scientific base of the branchial basket. The segmental literature (Gegenbaur, 1865; Parker, 1877; component of each left and right branchial Wiedersheim, 1877). As traditionally de- arch that articulates with the basibranchial scribed, the hyobranchial apparatus of ver- is called the hypobranchial (Fig. 1). Distal to tebrates contains postmandibular visceral the hypobranchial is the ceratobranchial, arches consisting of the hyoid arch (visceral which articulates distally with the segmen- arch 2) and the branchial arches posterior to tal component called the epibranchial. Fi- the hyoid arch, usually five in number in nally, the anterodorsally oriented elements fishes. The hyoid and branchial visceral of the branchial basket are called pharyngo- arches are involved, at least primitively, in branchials (Fig. 1). Anatomically, the hypo- cranial functions such as feeding and branchials and ceratobranchials are ventral respiration. elements of the branchial basket, whereas The paired visceral arches are segmented epibranchials and pharyngobranchials are and meet midventrally to articulate with one dorsal elements. or more median elements. In the generalized This terminology for the branchial arch vertebrate configuration, the branchial arch segments has been used widely by morphol- on each side of the head is composed of five ogists, except in the literature dealing with basic elements, each of which originates de- salamander morphology and evolution. Here, velopmentally as a cartilaginous structure elements that would be called hypobranchi- that may ossify later (Nelson, '69; Jollie, '73, als in fishes often are referred to as cerato- '86). The nomenclature of these five bran- branchials and the next distal elements are chial arch elements has been widely accepted called epibranchials (e.g., Alberch et al., '85; (see Nelson, '69 for a review), and is de- Dock and DeVree, '86; Erdman and Cun- scribed (at least generally) in all textbooks of dall, '84; Krogh and Tanner, '72; Larsen and comparative anatomy (e.g., Jollie, '73; Romer Guthrie, '75; Lombard and Wake, '76, '77; and Parsons, '77; Walker, '87). The midline Ozeti and Wake, '69; Regal, '66; Wake, '82).

0 1988 ALAN R. LISS, INC. 238 S.M. REILLY AND G.V. LAUDER in vertebrates. Here, we attempt to resolve c ANTERIOR the question of branchial-arch segmental homology in salamanders (Caudata) by present- ing three lines of evidence. First, the morphology of hyobranchial skeletal ele- PB ments in fishes and salamanders is compared. Second, muscles associated with these hyobranchial elements are compared and discussed in relation to the positional information that they provide on the homology of their insertions. Finally, we present new data on the occurrence of distal branchial arch elements in a population of newts. We interpret these elements as atavisms and as evi- Fig, 1. Lateral view of the left first gill arch of Polyp dence that the true epibranchials have been terus senegalua The gill arch consists of a segmented series of endochondral ossifications in the following or- lost in salamanders. der (ventral to dorsal): Hypobranchial (HB), ceratobran- We contend that the most parsimonious chial (CB), epibranchial (EB), and pharyngobranchial interpretation of the comparative morpholog- (PB). Note the position of both the cartilaginous and ical data, together with the novel informa- bony portions of the epibranchial in relation to the tip of is the ceratobranchial, and its similarity to the location of tion on atavistic branchial arch segments, the additional segmental elements (which we term epi- that the most medial two paired structural branchials) in Figure 3. Bony tissue is white, cartilage elements of salamander branchial arches are is stippled. Scale = 0.5 cm. hypobranchials and ceratobranchials. MATERIALS AND METHODS Use of this nomenclature assumes that the Specimens hypobranchial of all other lower vertebrates Branchial morphology was examined in 65 either is lost or fused with the ceratobran- branchiate adult Notophthalmus uiridescens, chial, and that the epibranchials, which fre- collected from McGuire’s Pond, 9.7 km south quently are lost in vertebrates, are retained of Carbondale, Jackson Co., Illinois. All spec- in salamanders. The first authors to use the imens were killed in chlorotone and fixed in terms ceratobranchials and epibranchials in 10% formalin. This population was used in salamanders (Huxley, 1874; Parker, 1877; two previous morphological analyses of Wiedersheim, 1877) stressed the importance metamorphosis in salamanders (Reilly, ’86, of ascertaining the homology of structures ’87). Sex, snout-vent length, and condition of among lower vertebrates, yet did not discuss external gills were recorded before the speci- their choice of the term ceratobranchial for mens were cleared and double-stained for the most medial branchial element of each bone and cartilage following the procedure of arch in caudates, when it is termed the hy- Dingerkus and Uhler (’77). Metamorphic pobranchial in all other lower vertebrates. condition of the skull and hyobranchial ap- Also, they did not offer any explanation of paratus were examined and photographed the fate of the hypobranchial. using a Zeiss SV-8 binocular dissecting mi- Marche and Durand (’83)discussed the dis- croscope. Voucher specimens are deposited in cordance of branchial arch terminology the Museum of Natural History, The Univer- within salamanders and marshaled evidence sity of Kansas (KU 203963-203987, KU to support their view that salamanders have 206794-206833). true hypobranchials and ceratobranchials. Duellman and Trueb (’86) briefly reviewed Comparative analyses this controversy, noting that although they Branchial arch morphology in several adopted the term “ceratobranchial” in lieu lower vertebrate clades was examined to pro- of the often used “epibranchial” for caudates, vide a basis for positional analyses of seg- there were no data in the literature that mental homology. Relevant clades for permitted a resolution of the homology of comparison were chosen on the basis of cur- these gill arch segments. rent phylogenetic hypotheses relating tetra- The terminological confusion present in the pods, lungfishes, coelacanths, ray-finned literature reflects differing views on the ho- fishes, and chondrichthyans (Lauder and mology of the segmental gill arch elements Liem, ’83; Maisey, ’86). ATAVISMS AND HYOBRANCHIAL HOMOLOGY 239

A C

Fig. 2. Morphology of the hyobranchial apparatus in ure and Figure 3: BB, basibranchial; CB 1-5, Cerato- three lower vertebrates: A Polypterus senegalus, a ray- branchials 1to 5; CH, ceratohyal; EB1, Epibranchial 1; finned fish (Actinopterygii); B: Eusthenopteron fordii HB 1-2, Hypobranchials 1 and 2 (solid black); HH, Hy- (after Jarvik, 'BO), a "rhipidistian;" C: Ambystoma ti- pohyal; W,transversus ventralis muscle. grinum (larval morphology). Abbreviations for this fig-

Information on hyobranchial osteology and ogy (Figs. 1, 2). In chondrichthyans, the hyo- myology in lower vertebrates is derived from branchial apparatus consists of median both descriptive and comparative studies of basibranchial elements which articulate with fishes and amphibians in the literature (e.g., four or five hypobranchials, each of which in Allis, '17, '22; Druner, '02, '04;Eaton, '36; turn, articulates with the ceratobranchials, Edgeworth, '35; Jarvik,. '80; Jollie, '82; Lom- epibranchials, and pharyngobranchials in se- bard and Wake, '76; Ozeti and Wake, '69; ries. This arrangement forms a complete Piatt, '39, '40;Rosen et al., '81; Wiedersheim, branchial basket posterior to the skull (Ed- 1877; Wiley, '79a,b; Winterbottom, '74), as geworth, '35; Jollie, '73). well as from our own previous studies of In primitive actinopterygians (e.g., Polyp branchial arch morphology and function in terus, Figs. 1, 2A), the same general pattern lower vertebrates (Lauder, '80; '83; Lauder of elements is present (Allis, '22). The ventral and Shaffer, '85; Reilly, '87; Reilly and Lau- gill arch elements consist of a large median der, '88). Muscle terminology is adapted from basibranchial which articulates with short Winterbottom ('74) for fishes and Edgeworth hypobranchials on each side. Elongate cera- ('35) for salamanders. tobranchials articulate with the distal end of Throughout the Results and Discussion each hypobranchial (Fig. 2A: CB). sections, in order to avoid confusion, we will In rhipidistians, epibranchials and phar- anticipate our final conclusions on the ho- yngobranchials are found on the first two mology of the salamander branchial arch branchial arches and connect to the occipital segments and refer to the most medial paired bone (via infrapharyngobranchials). On the ventral segments as hypobranchials, and the third arch only a small epibranchial re- next distal segments as ceratobranchials. We mains; it joins to Ceratobranchial 2 by con- do this in order to have a name to place on nective tissue (Jarvik, '80). The ventral gill the various segments of disputed homology arch elements consist of short hypobranchi- as we present the evidence for our als articulating with the median basibran- conclusions. chial and elongate ceratobranchials (e.g., Eusthenopteron, Fig. 2B: HB, CB). RESULTS Salamanders have a median basibranchial, Hyobranchial osteology two pairs of hypobranchials, and from one to The hyobranchial apparatus among lower four ceratobranchials (e.g., Ambystoma ti- vertebrates is very similar in gross morphol- grinum larva, Fig. 2C). The number of cera- 240 S.M. REILLY AND G.V. LAUDER tobranchials depends on the metamorphic stage in transforming salamanders or the point at which metamorphosis is fixed in the various paedomorphic lineages. Occasion- ally, in some individuals, rudiments of Hy- pobranchial 3 (Druner, '02, '04; Kallius, '01; Rosen et al., '81; Stadmuller, '24) and even Hypobranchial4 (Druner, '04) are found. On Arches 3 and 4, which usually lack hypobranchials, the proximally widened heads of the ceratobranchials articulate with the previous ceratobranchial. In salamanders, as in all other lower vertebrates, the ceratobranchials are the longest elements and they always project posterodorsally. Reduction of hyobranchial elements is seen in many lower vertebrate groups (Nelson, '69; Rosen et al., '81). The number and size of hyobranchial elements vary in actinopterygians, Latimeria, Neoceratodus (Dipnoi), and salamanders. In Latimeria, the pharyngobranchials are reduced or absent, and they are lost in lungfishes (Miles, '77). Both Lati- meria and lungfishes have lost Hypobran- chial 5, and Ceratobranchial 5 articulates with Ceratobranchial 4 (Forey, '81; Rosen et al., '81). In Latimeria, lungfshes, and salamanders, when hypobranchials are absent, the proximal head of the posterior ceratobranchial articulates directly with the head of the preceding ceratobranchial and not with the basibranchial. Many ray-finned fishes possess reduced pharyngobranchials andor epibranchials, especially on the most posterior branchial arches (Nelson, '69). It is not surprising that these are the most commonly lost or reduced elements of the hyobranchial apparatus, as during ontogeny the hyobranchial apparatus of fishes typically develops from anteroventral to dorsoposterior.

Comparative myology Ventral branchial muscles of gnathostomes are found in association with the hypobranchials and ceratobranchials but never attach to the third element distal from the basibranchial (epibranchials). Therefore, hyobranchial elements of the branchial arches that have ventral muscles attached to them must be either hypobranchials or ceratobranchials. Several branchial muscles always are found connected to the same hyobranchial elements; the positions of three of these are indicated in Table 1. First, the transversi ventrales muscles of all lower vertebrates (Table 1; Fig. 2: TV) invariably originate on ATAVISMS AND HYOBRANCHIAL HOMOLOGY 241

ceratobranchials (identified as the elongate TABLE 2. Atavistic epibranchials (EB) found in adult element of each branchial arch attaching me- Notophthalmus viridescens from southern Illinois, on dially to a smaller element that in turn artic- the left (L),right (R),or on both (L + R) sides ulates with the unpaired median element) Specimen EB 1 EB 3 EB 4 and insert at the midline on a median raphe KU 206808 R - - (Edgeworth, '35; Jollie, '82; Winterbottom, KU 2039'72' L* + R - - '74). Many ray-finned fishes possess several KU 206814l L+R - - of these muscles which may extend between KU 203966 L+R - - KU 206814 L+R - - ceratobranchials of successive arches (Wiley, KU 206801' i+R - - '79a; Winterbottom, '74). The most posterior KU 206826 L+R - - transversus ventralis muscle invariably orig- KU 203965 R* L - KU 206812 - inates from the most posterior cerato- - L+R branchial. *Ossified Second, the obliquus ventralis one muscle 'Photograph in Figure 3 (also called the subarcualis rectus one) of lower vertebrates originates from the hyoid arch (hypohyal, ceratohyal, or both) and ex- small cartilaginous rod extending from the tends posteriorly to insert on the first end of each Ceratobranchial 1 (Fig. 3A). ceratobranchial. Closer examination of the articulation of this Third, the pharyngocleithralis (Wiley, '79a; terminal element clearly shows that it is an Winterbottom, '74) or omoarcualis (Edge- independent structure (Fig. 3B). A second worth, '35) muscles always are associated specimen (KU 203972) has a large bony Epi- with ceratobranchials. As indicated in Table branchial 1 on the left side (Fig. 3C) and a 1, this muscle originates from the pectoral small, round, cartilaginous Epibranchial 1 girdle and inserts on one or more of the pos- on the right (similar to that shown in Figure terior ceratobranchials (Wiley, '79a; pers. 3D). An additional five specimens (Table 2) obs.). have small, round epibranchial cartilages on A comparison of branchial myology across Ceratobranchial 1 (as in Fig. 3D). Another lower vertebrates (Table 1) reveals that no specimen (KU 203965) has a small bony epi- ventral branchial muscle ever attaches to an branchial 1 on the right side. It also has epibranchial (identified as the third paired retained bony Ceratobranchials 2 and 3 with element from the ventral midline). a cartilaginous Epibranchial 3 on the left side. The last specimen (KU 206812) has car- Segmental variation within branchial arches tilaginous remnants of all four ceratobran- The morphology of the branchial arches of chials, and has epibranchial cartilages on the most individual Notophthalmus viridescens fourth pair of ceratobranchials. examined is similar to the modal condition described in the literature for salamanders; DISCUSSION each of the first two arches contains two The view that the two segmental elements paired elements (e.g., Fig. 2C). However, 17 of the salamander branchial arch are cerato- instances of cartilaginous or ossified ele- branchials and epibranchials implies that ments located distal to the ceratobranchials hypobranchial elements have been lost. The were observed in nine of the series of 65 alternate view is that the salamander ele- neotenic newts examined (Table 2; Fig. 3). In ments are homologous to those of other ver- each case, a clearly separate cartilaginous tebrates, and represent hypobranchials and (and sometimes ossified) element is con- ceratobranchials. Which of these two inter- nected to the distal end of a ceratobranchial. pretations is most parsimonious in light of Fourteen cases can be interpreted as first the three classes of evidence presented above? epibranchials, because the novel element is We suggest that there are three reasons for located distal to Ceratobranchial 1. The su- interpreting salamander arch segments as barcualis rectus one muscle does not attach hypobranchials and ceratobranchials: 1) The to the novel epibranchial element, and re- first segment of the urodele branchial arch tains its normal morphology in mapping articulates with the midline basibranchials around the posterior end of the ceratobran- (about which there is no debate) as in other chial. These individuals thus have a first vertebrates. 2) The early ontogenetic stages branchial arch with three paired segments. of Notophthalmus viridescens or Ambystoma One specimen (Table l:KU 206814) has a talpoideum examined for this paper show no 242 S.M. REILLY AND G.V. LAUDER

Fig. 3. Photographs of the hyobranchial apparatus of Ceratobranchial 1 (CB1).B: enlargement of the distal adult Notophthalmus viridescens to show representa- end of gill arch one from panel A to show the junction tives of the structures interpreted here as atavistic epi- between the ceratobranchial and the atavistic epibran- branchials. A ventrolateral view of the entire hypo- chial. C: Ventrolateral view of the left hyoid and first branchial apparatus (in KU 206814) illustrating the first branchial arch (in KU 203972). The atavistic epibran- gill arch on the left side which consists of a hypobranchial in this specimen is ossified completely. D: Speci- chial, articulating proximally with the basibranchial, men KU 206801 showing the small cartilaginous a ceratobranchial, and a small cartilaginous epibran Epibranchial 1. Arrows indicate the junction between chial (EB1). Note that the second branchial arch lies be- adjacent gill arch elements; for abbreviations see caption hind the junction between Hypobranchial 1 (HB1)and to Figure 2. Scale = 1mm.

small elements adjacent to the basibranchial 1) that there has been fusion during ontog- that might have been lost during ontogeny. eny (which has never been observed);2) alter- 3) The relative size of the ceratobranchial ation of the shape of the fused element to (the longest ventral element) and its shape look like hypobranchials of other verte- and position (Figs. 1, 2) is consistent with brates; and 3) alteration of the shape of the that of other lower vertebrates. epibranchial to look like the ceratobran- Interpretation of the second segment as an chials of other vertebrates. The view that epibranchial requires the following assump- salamanders have hypobranchials and cerato- tions about transformations of branchial arch branchials involves no character-state tran- characters: 1) loss of the hypobranchials; 2) sitions. The comparative myological evi- alteration of the shape of the ceratobranchi- dence also is interpreted most parsimoniously als to look like the hypobranchials of other as an indication that salamanders have hy- vertebrates; and 3) alteration of the shape of pobranchials and ceratobranchials. In order the epibranchial to look like the ceratobran- to interpret the second arch segment of sala- chials of other vertebrates. Alternatively, the manders as an epibranchial one must accept view that first element is the fusion of the the following assumptions about character hypobranchial and ceratobranchial assumes: transitions in branchial myology. Each of the ATAVISMS AND HYOBRANCHIAL HOMOLOGY 243

three ventral branchial muscles, that attach ter possessed by all members of an ancestral to the ceratobranchials in all other verte- population” (Hall, ’84: p. 89). We interpret brates (Table 11, must shift their insertions the extra branchial arch elements observed from the ceratobranchial to an epibranchial, here in Notophthalmus viridescens as ata- as the ceratobranchial moves ventrally to oc- vistic epibranchials. These structures have cupy the place of the lost (or fused) all the essential features of an atavism. hypobranchial. If one accepts the view that Atavisms need not arise as the result of salamanders have hypobranchials and cerato- gene mutations (Hall ’84). Epigenetic events branchials, then no character transitions in such as timing of development, tissue inter- branchial myology are required; thus, sala- actions andlor growth and morphogenesis can manders are hypothesized to retain the prim- activate previously quiescent portions of the itive condition. genome. This population of Notophthalmus The occurrence of terminal segmental viridescens found to contain the atavistic epi- structures illustrated herein (Fig. 3) also sup- branchials is known to contain branchiate ports the view that salamanders possess hy- (gilled)adults (Brandon and Bremer, ’66).De- pobranchial and ceratobranchial elements, tailed studies of the cranial and hyobran- because the novel segments resemble epi- chial ontogeny of members of this population branchials of other vertebrates both in shape have shown that neoteny is limited to the and position. An alternative view is that the variable retention of larval ceratobranchials true hypobranchials of caudates have been and external gills (Reilly, ’86, ’87). The ata- lost (or fused with the ceratobranchial), and vistic epibranchials in this population clearly that the novel structures found in Note resemble epibranchials found in other lower phthalmus viridescens are pharyngobranchi- vertebrates, and their presence in a few in- als. This interpretation predicts that early in dividuals shows that the genetic potential to development a small remnant of an element produce this character has persisted and is just lateral to the midline basibranchials oc- once again being expressed. Whatever causes casionally should be found, and that rare delay in the completion of metamorphosis atavistic segments intercalated between the (many adults delay the complete resorption midline and the bone we are terming the of larval ceratobranchials and external gills, hypobranchial should be discovered. To our see Reilly, ’87) in this population of newts knowledge, no such anomalies have ever also occasionally may remove the repressive been reported. In contrast, several authors mechanism that is blocking the formation of have reported atavistic posterior hypobran- epibranchials. chials in just the position we would expect if The special significance of atavistic char- the first paired segments are in fact true acters in the context of this investigation is hypobranchials. Druner (‘04)noted the pres- that they provide evidence of homology. The ence of atavistic Hypobranchials 3 and 4 in reappearance of an ancestral character in Cryptobranchus, and atavistic third hypob- descendent taxa tests hypotheses of homol- ranchials have been found in Salamandra ogy in these descendent taxa. In this case, maculosa (Driiner, ’02; Kallius, ’01; Stad- the reappearance of an atavistic structure muller, ’24; Francis, ’34) and Salamandra that closely resembles an epibranchial in atra (Tarapini, ’09). shape and position indicates that any ele- Lost characters typical of remote ancestors ments previously considered to be epibran- and not seen in the parents or recent ances- chials must be homologous to another tors of the organisms displaying them are structure. Since two distinct morphological referred to as atavisms. Particularly well- structures in salamanders cannot both be known examples of atavisms are the cases of epibranchials, one must be homologous to naturally occurring supranumerary digits in another branchial arch segment. horses (Ewart, 1894) and the induced produc- The comparative morphological and devel- tion of teeth in chicks (Kollar and Fisher, opmental evidence presented here show that ’80). Four essential attributes that define the elongate branchial arch element in the atavistic characters are 1) “persistence into salamander hyobranchium is a ceratobran- adult life,” 2) “absence in the parents or re- chial. In all respects it is comparable to cer- cent ancestors,” 3) “presence in one or only a tobranchials in ray-finned fishes, lungfkhes, few individuals within a population,” and 4) Latimeria, and Eusthenopteron in both rela- “close resemblance to . . . . the same charac- tive topographic position and in the muscles 244 S.M. REILLY AND G.V. LAUDER originating from and inserting on it. Conse- ing the formation of atavisms. Biol. Rev. 59:89-124. quently, the basic segmental arrangement of Huxley, T.H.(1874) On the structure of the skull and of the heart of Menobranchus lateralis. Proc. Zool. Soc. parts in the visceral arches has been con- London. Mar. 17,1874:186-204. served across the transition from aquatic to Jarvik, E. (1980) Basic Structure and Evolution of Ver- terrestrial life in vertebrate evolution. tebrates. London: Academic Press. Jollie, M. (1973)Chordate Morphology. Huntington, New ACKNOWLEDGMENTS York Krieger. Jollie, M. (1982)Ventral branchial musculature and syn- We thank Ronald Brandon and Bob Weck apomorphies questioned. Zool. J. Linn. Sac. 75:35-47. for assistance in collecting specimens. Spe- Jollie, M. (1986) A primer of bone names for the under- cial thanks are due to Tim Bradley for his standing of the actinopterygian head and pectoral girdle skeletons. Can. J. Zool. 64:365-379. generous assistance in translating German Kallius, E. (1901) Beitrage zur Entwicklung der Zunge. sources. Ronald Brandon, Zoe Eppley, Carl I. Theil: Amphibien und Reptilien. Anat. He%. I, Gans, Brian Hall, Scott Schaefer, Peter 16:533-760. Wainwright, David Wake, and two anony- Kollar, E.J., and C. Fisher (1980) Tooth induction in chick epithelium: Expression of quiescent genes for mous reviewers provided valuable comments enamel synthesis. Science 207:993-995. on the manuscript. This work was supported Krogh, J.E., and W.W. Tanner (1972)The hyobranchium by NSF grants DCB 8602606 and BSR and throat myology of adult Ambystomatidae of the 8520305 (to GVL). United States and northern Mexico. Brigham Young Univ. Sci. Bull. Biol. Ser. 16:l-69 LITERATURE CITED Larsen, J.H., and D.J. Guthrie (1975)The feeding system of terrestrial tiger salamanders (Ambystoma tigrinum Alberch, P., G.A. Lewart, and E.A. Gale (1985) The fate melanosticturn Baird). J. Morphol. 147:137-154. of larval chondrocytes during the metamorphosis of Lauder, G.V. (1980) The role of the hyoid apparatus in the epihranchial in the salamander, Eurycea bisli- the feeding mechanism of the living coelacanth, Lati- neuta. J. Embryol. Exp. Morph. 88r71-83. meria chalumnue. Copiea 1980: 1-9. Allis, E.P. 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