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Lower Devonian Pelecypoda from Reefton, New Zealand

[Received by Editor, March 22, 1957.]

Abstract

Actinopteria mackayi n. sp. is described from the Reefton Mudstone of Lankey Creek. Pterinopecten (Pseudaviculopecten) casterorum n. sp. from the same formation in Rainy Creek is the first member of the Pterinopectinidae to be recorded from New Zealand. Paleodora Fleming, a distinctive genus provisionally classed in the Solenomorphidae, is described in detail, and its sole species P. reeftonensis Fleming, from the Reefton Mudstone of Lankey and Rainey creeks, is figured for the first time.

The Devonian fauna of the Reefton beds was described by Allan in 1935, and the abundant Brachiopoda of the Reefton Mudstone were revised by the same author in 1947. They indicate approximately Lower Coblenzian age. Suggate (in press) has revised the stratigraphy and structure of the Reefton Devonian, and has recorded characteristic species of the Reefton Mudstone in Rainy Creek, three miles south of Lankey Creek.

Allan (1935: 24–26) figured three species of Pelecypoda from the Reefton Mudstone, and remarked that the number of genera and species of mollusca could be considerably increased if all the material in the old collections was fit to describe, noting (p. 30) that a pterineoid genus is apparently not uncommon. Subsequent collections, particularly from Rainy Creek, have confirmed the presence of a fairly varied pelecypod fauna, but few of the specimens are well enough preserved for description.

With the species described below, the recorded Pelecypod fauna of the Reefton Mudstone is as follows:

Paleodora reeftonensis Fleming.

Grammysioidea sp. (Allan, 1935, Pl. 3, fig. 10)

Actinopteria mackayi Fleming n. sp.

Pterinopecten (Pseudaviculopecten) casterorum Fleming n. sp.

Goniophora hendersoni Allan (1935, Pl. 3, fig. 6)

I am grateful to Drs. A. J. Boucot and Preston E. Cloud, jun., United States Geological Survey; Dr. N. D. Newell, American Museum of Natural History; Dr. K. E. Caster, University of Cincinnatti; Dr. L. R. Cox, British Museum; and Dr. A. A. Opik, Bureau of Mineral Resources, Canberra, for discussion and advice on the systematic position of Paleodora. The plates accompanying this paper are from drawings by R. C. Brazier (N.Z. Geological Survey) and photographs by S. N. Beatus (Department of Scientific and Industrial Research).

Class Pelecypoda Subclass
Prionodesmacea Dall
Order Palaeobranchia (= Paleoconcha Neumayr)
Superfamily Solemyacea Dall
Family Solenomorphidae Paul (= Solenopsidae Neumayr)

The classification of Paleodora in the Solenomorphidae is quite tentative.

Most of the fossils grouped in the Solenomorphidae (formerly Solenopsidae) have inequilateral shells, and are generally described as having anterior beaks, like.The

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majority of other inequilateral pelecypods. If, however, they are related to the Solemyidae, as indicated by current classifications, the beaks may be posterior as they are in living Solemya. The hinge structure of Paleodora has been interpreted by analogy with that of Solemya (Text-figs. 1–3) and its beaks may thus be posterior. There is little evidence for deciding the true orientation of other Solenomorph genera, but to avoid confusion I have retained the customary terminology in describing Paleodora and comparing it with other genera. Thus, if the hinge of Paleodora corresponds with that of Solemya, the words “anterior” and “posterior” should be transposed in the following descriptions.

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Text-fig. 1–3.—Two living Solemyidae, Solemyarina (Zesoleyma) parkinsoni (Smith) (1) and Solemya mediterranea (Lam.) (2), compared with Paleodora reeftonensis Fleming (3), to show possible analogies in chondrophoric and myophoric internal ribs. Ligament diagonally hachured; muscle scars stippled.
Text-fig. 4.—Pterinopecten (Pseudaviculopecten) casterorum Fleming n.sp., holotype, showing ligamental chevron grooves of crushed left valve.

The characters of the Solenomorphidae are poorly defined, chiefly because hinges can seldom be studied in Paleozoic fossils. Most are distinguished from the Solemyidae (living Solemya and its fossil relatives—e.g., Janeia King, Pleurodapis Clarke, Prothyris Meek, Paraprothyris Clarke) by having a strong oblique umbonal ridge delimiting a differentiated posterior area. Some Solenomorphid genera also have a shallow median umbonal depression such as is characteristic of the related family Grammysiidae. There is no evidence of a projecting periostracal fringe. After death, the strong ligament of Solemya pulls the valves open, and some fossil Solemyids are also preserved with wide open valves (e.g., Pleurodapis, Paraprothyris, see Clarke, 1913, Pl. 14; Prothyris, see Mailleux, 1932, Pl. V, fig. 2). Solenomorphid fossils, on the other hand, are often found with closed valves. The hinge is seldom well preserved in Devonian pelecypods and radiating buttress ridges have not been described in the literature on Solenomorphid genera that I have seen, but the paleoconch Palaeanatina Hall (type species, P. typa Hall, Upper Devonian, U.S.A.) has two slender processes beneath the beak, perhaps analogous with the buttresses of Paleodora and Solemya. In external form Paleodora shows some resemblance to Grammysia caudata Sandberger, type of Arcomyopsis Zittel (= Cercomyopsis Sandberger non Meek), to Cimitaria Hall (usually classed in Anatinacea, sometimes as a paleoconch), and to some of the species formerly classed as Leptodomus McCoy 1844 (not of Schoenberr, 1843).

Dr. A. A. Opik and Dr. N. D. Newell have independently suggested to me that Paleodora may be a member of the order Conchostraca (Class Branchiopoda, Crustacea), which have bivalved shells with (in the family Leaiadidae Raymond)

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two or more widely diverging carinae, or smooth-topped ridges. I have been unable to see the recent publication of Novozhepov (1956), but from figures and descriptions published by Raymond (1946), Kobayashi (1954), Tasch (1956) and others, it appears that Paleodora differs from the Leaiadidae in its concave (not straight) posterior dorsal margin, in its stronger and well-developed hinge mechanism, and in its internal, not external, radial ridges (which are thus clavicles or myophoric buttresses rather than carinae). The external carinae of the Leaiadidae generally continue to the ventral margin, whereas the internal ridges of Paleodora stop short of the margin and are obviusly not the product of a growing mantle edge. Leaiadidae are mostly much smaller than Paleodora, are mostly non-marine, and did not reach their main development till the upper Paleozoic. Paleodora reeftonensis occurs in siltstone with marine brachiopods, pelecypods, and trilobites. The Devonian Conchostracans Rhabdostichus, Praeleaia, Schizodiscus, and the estherian genera, do not resemble Paleodora. Dr. P. Tasch, University of Wichita, has kindly examined rubber casts of Paleodora, and comments that as far as he can tell there are no known conchostracans with which it can be associated. In Leaiadidae, the dorsal margin is straight, and does not have an umbonal rise above it, and the ribs are equally defined on both sides of the valve. The proportions of the valve in Paleodora would be an unlikely feature for a leaian conchostracan, and the growth lines near the margin do not resemble conchostracan growth lines or zones. He concluded that Paleodora is unlikely to be a conchostracan.

Genus Paleodora Fleming
1957. Trans. Roy. Soc. N.Z., 84 (4): 943.

Type Species. Paleodora reeftonensis Fleming. Reefton, New Zealand (Coblenzian, Lower Devonian).

Shell small, thin, compressed, elongate, inequilateral; beaks anterior, low; anterior margin short and rounded, posterior margin long and truncated, posterior dorsal margin concave; well-defined umbonal ridge, reflecting an internal rib delimiting a narrow triangular posterior area with close spaced growth lines; disc sculptured by concentric folds. Hinge edentulous; ligament apparently amphidetic, probably becoming internal in front of beaks. Beak strengthened internally by an oblique radial clavicle, interpreted as a myophoric buttress, and by weaker nymph ridges on either side. Muscle scars and pallial line unknown.

Paleodora is formed from the prefix palaeo (ancient) and the stem of Pandora, the name of a Tertiary and living pelecypod superficially resembling P. reeftonensis. The name is to be considered feminine.

Paleodora reeftonensis Fleming. Plate 14, figs. 1–7.

1935. Palaeoneilo sp. ind., Allan, N.Z. geol. Surv. Pal. Bull. 14: 25, Pl 3, fig. 9.

1957. Paleodora reeftonensis Fleming, Trans. Roy. Soc. N. Z. 84 (4): 943.

Material. Holotype (3755/1 and 3755/2), right valve interior and exterior; figured paratypes, right valve exterior and left valve interior (3755/3) and left valve exterior (3755/4), and four imperfect paratypes (3755/5–8); all in N.Z. Geological Survey collection. The specimens are natural moulds which have been studied from rubber replicas.

Description General characters as described for genus. The specimens have been compressed, so the original amount of gape (if any) and any differences in valve inflation cannot be confidently determined. Sculpture of disc at first consisting of regular concentric ribs, about 3 per mm, triangular in cross section, stopping rather abruptly at umbonal ridge, persisting to the ventral margin in some specimens (Fig. 3) but merging into irregularly spaced growth folds and growth lines in others (Fig. 1). Posterior umbonal ridge well defined near beaks, becoming low and rounded towards the margin but accentuated in some specimens by compression over the internal rib below it (Fig. 4). Posterior area concave near beak, but less so towards margin, sculptured by incremental lines, about twice as abundant as the folds on the disc, and interdigitating with them on the umbonal ridge (Fig. 3). A ridge at the dorsal margin of the area in paratype 3755/3a (Fig. 4) is due to compression.

Interior of valve reflecting external folds, which stop at a radial line corresponding with the external umbonal ridge, just below a prominent, regular, narrow, slightly curved, internal radial ridge, running back from the beak but dying out on approaching the posterior margin.

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Interior of area, dorsad of posterior ridge, smooth except for an obscure irregular ridge hidden behind the hinge plate (Fig. 7). No trace of adductor scars and pallial line can be detected, perhaps owing to solution of inner shell layer prior to compression.

Posterior dorsal margin inflexed to form an edentulous hinge plate thickened and rod-like in front, bearing a weak ventral groove, tapering to a lamina behind, failing to reach posterior dorsal angle (thus suggesting that the shell gaped in the siphonal region) and expanded in front to form a sickle-shaped nymph. Anterior dorsal margin short, curved, thin, separated by a narrow excavate plate from a thin sub-parallel nymph ridge. Clavicle narrow, erect, highest at ventral third, forming an angle of about 120 degrees with posterior dorsal margin, its base linked with the nymph ridges on either side by a smear of callus.

Dimensions. Length 24 mm, height 11 mm, inflation 2 mm (holotype).

Localities. Reefton Mudstone of Rainy Creek (G.S. 129 and G.S. 3755) and of “Lankeys Gully” (G.S. 130). Coblenzian, Lower Devonian. Imprints, generally distorted and imperfect, are not uncommon in Rainy Creek.

Superfamily Pteriacea
Family Pteriidae

Genus Actinopteria Hall

1883. Geol. New York, Palaeont. 5 (1) Lamell., Pl. 17, fig. 1–4.

Type Species. A. decussata Hall, Devonian, U.S.A.

Actinopteria mackayi Fleming n. sp. Plate 14, figs. 8, 9.

1886. Avicula; Hector, Outline N. Z. Geol.: 80, fig. 52 (1).

Material. Holotype, a well preserved natural mould and incomplete steinkern of a left valve (G.S. 130). Paratype, fragment of left valve posterior auricle.

Description. Shell large, strongly prosocline, high, longest at dorsal margin, with very unequal ears, ornamented. Cardinal margin rather straight. Axial line convex forwards. Beak narrow, rising above cardinal margin. Anterior auricle small, rounded, differentiated from body of shell by well defined auricular sulcus. Anterior margin gently convex, overhung by steep anterior flank. Ventral margin short, strongly curved. Posterior umbonal ridge and posterior margin gently concave. Posterior auricle large, triangular, differentiated from body of shell by a shallow auricular sulcus. Auricular sinus broad, shallow, evenly curved.

Sculpture of strong, spaced, rounded costae, reticulated by imbricating lamellae. About 30 costae at ventral margin, arising by intercalation from 18 primary costae on the umbo, ranked in two series on posterior flank, but crowded, subequal, and weaker on steep anterior flank. Concentric lamellae, festooned between costae, about a millimeter apart in the centre, crowded in front and ventrally. Anterior auricle with strong, crowded lamellae, lacking radials. Posterior auricle with about 25 radial costae, the upper three strongest, the rest weak, spaced, dominated by close-spaced incremental lamellae, granulated by the radials. Right valve unknown.

Steinkern reflecting external sculpture. Byssal sinus shallow, retracted behind anterior flank.

Dimensions. Length, 50 mm (at auricles); height, 58 mm (normal to cardinal margin), oblique height, 69 mm (holotype).

Locality. “Lankey's Gully, Reefton, Inangahua County” (G.S. 130), coll. A. McKay, 1874 (holotype). The fragmentary paratype was collected by Professor K. E. Caster from the Reefton Mudstone of Stony Creek in August, 1956.

Actinopteria mackayi is similar to such North American species as A. boydi (Conrad), Hamilton Group (Grabau and Shimer, 1909, fig. 592) which was placed in the Pterineid genus Actinopterella Williams by Williams and Breger (1916: 184), but in Actinopteria by Shimer and Shrock (1944). The steinkern of A. mackayi shows no trace of the hinge teeth diagnostic of Pterineidae, but is incomplete so that its generic position is not certain. This species differs markedly in shape and sculpture from Actinopteria sp. figured by Shirley (1938: 486, Pl. 44, fig. 15) from the Lower Devonian of Baton River. As remarked by Allan (1935), there are true Pterineids at Reefton, but none so far collected is worth description.

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Fig. 1–7.—Paleodota nitonensis Fleming Ramv Creek Reefton (Coblenzian Lower Devonian) — R. C. Brazier del Fig. 1—Paratype G. S.3755/2 right valve exterior × 1⅓rd Fig. 2—Holotype G. S.3755/1 right valve interior × 1⅓rd Fig. 3—Paratype G. S.3155/4 left valve or compressed showing relfection of hing shin × 1⅓rd Fig. 4—Paratype G. S.3755/3a right valve exten × 1⅓rd Fig. 5—Paratype G. S.3755/3b same specimen as Fig. 4 showing anterior fragment of right valve and interior of left valve, × 1⅓rd Figs. 6 7—Holotype G. S.3755/1 lateral (6) and oblique ventral (7) views of hinge × 3 (approx) Figs. 8 9—Actinoptea mackam Fleming n. sp. Lankey Creck Reefton Holotype left valve exterior (8) and interior (9) × 1

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Fig. 1–5—Pternnopecten (Psevdaviculopecten) casterorum Fleming n. sp. Holotype. Ramy Creek, Reefton (Coblenzian, Lower Devonian) Fig. 1—Right valve, exterior. × 3 Fig. 2—Left valve, interior, × 2 Fig. 3—Left valve, exterior, × 2 (with outline restored) Fig. 4, 5—Right valve exterior, crushed across collapsed ligamental area of left valve. × 1 (4) and × 2 (5)

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Superfamily Pectinacea
Family Pterinopectinidae Newell

Genus Pterinopecten Hall

1883. Geol. of New York, Palaeont 5 (1) Lamell.: 3.

Type Species (by subsequent designation, Miller, 1889). Pterinopecten undosus (Hall), Middle Devonian, U.S A.

Subgenus Pseudaviculopecten Newell
1937. Geol. Surv. Kansas 10: 38.

Type Species (by original designation). Aviculopecten princeps (Conrad), Middle Devonian, U.S.A.

For diagnosis and discussion, see Newell (1937). Use of Pseudaviculopecten as a subgenus of Pterinopecten follows Shimer and Shrock (1944).

The species described below agrees closely with the type of the subgenus in hinge, external form, and left valve sculpture, but deviates from Newell's diagnosis of Pseudaviculopecten in its dissimilar valve ornament.

Pterinopecten (Pseudaviculopecten) casterorum Fleming n. sp. Plate 15, figs. 1–5.

Material. Unique holotype in N.Z. Geological Survey Collection (3755/9) consisting of well-preserved natural internal mould of left valve, bearing the incomplete and crushed external mould of the right valve; fragmentary external mould of left valve. The description is based on rubber replicas prepared from the holotype moulds.

Description. Shell thin, prosocline, ornamented. Valves dissimilar. Crushed right valve apparently thinner and less inflated than left. Hinge margin straight, about four-sevenths shell length. Auricles subequal, well differentiated, their outer margins broadly sinused.

Left valve weakly convex and excavated below beak, height two-thirds length, strongly sculptured by intercalate costae arranged in three or more ranks. Primary costae about 17, remaining dominant to ventral margin; secondary costae appearing 9 mm from beak; tertiary costae irregularly at about 15 mm. Costae flatly rounded with flat interspaces. Concentric lamellae (fila) strong, fairly distant, about two per millimeter near ventral margin, with microscopic incremental lines between. Interior of shell, as preserved, plicate, reflecting external costae probably owing to partial solution of inner layer before compression. Ligament area long and narrow, shallowly excavated, extending back half way along dorsal margin of posterior auricle, there showing one clear chevron groove and traces of another, and forward to the base of the anterior auricle, there showing three grooves (deformed by crushing of the beak). Posterior auricle strongly sinused, dorsal margin prolonged as a spine, channelled within. Anterior auricle better defined than posterior (i e., auricular sulcus deeper), outer margin deeply sinused below a blunt antero-dorsal spine. Sculpture of left valve auricles unknown.

Right valve flattish, beak low, not rising above hinge margin; auricles differentiated from disc in sculpture and defined by a weak posterior and strong anterior cardinal ridge. Disc smooth near beaks, but ventrally sculptured by about 65 weak radial costae, subequal in strength at margin, though rising by intercalation of secondaries and tertiaries. Concentric sculpture of weak irregular growth folds and microscopic incremental lines. Posterior auricle with a dorsal costa and about 16 fine spaced radial costae crossed by strong concentric lamellae which stop abruptly at the auricular groove. Anterior auricle differentiated into a long narrow dorsal part with six weak radial costae crossed by growth lamellae convex forwards, and a shorter byssal part, lacking radials, with sloping growth lines weakly concave forwards defining the byssal sinus. Byssal notch well-defined, narrowing back into deep auricular sulcus. Interior not preserved.

Dimensions. Length, 35 mm; height, 26 mm (left valve).

Locality. Reefton Mudstone, Rainy Creek, tributary of Inangahua River, Reefton, New Zealand (G.S. 3755). Lower Devonian.

The specific name is in tribute to Professor and Mrs. K. E. Caster, of Cincinnatti, Ohio, who collected at Rainy Creek in August, 1956, when the holotype was found.

References

Allan, R. S., 1935. The Fauna of the Reefton Beds (Devonian), New Zealand. N.Z. geol. Surv. Pal. Bull. 14.

—— 1947. A Revision of the Brachiopods of the Lower Devonian Strata of Reefton, New Zealand J. Pal. 21 (5): 436–52.

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Beushausen, L., 1895. Die Lamellibranchiaten des rheinischen Devon mit Ausschluss der Aviculiden. Abh. k. Preuss. geol. Landesanst. N.F., 17.

Clarke, J. M., 1913. Fosseis Devonianos do Parana. Mon. Serv. geol. min. Brazil, 1.

Fleming, C. A., 1957. A New Devonian Lamellibranch from Reefton, New Zealand. Trans. roy. Soc. N.Z. 84: 943.

Grabau, A. W., and Shimer, H. W., 1909. North American Index Fossils, New York.

Kobayashi, T., 1954. Fossil Estherians and Allied Fossils. J. Fac. Sci. Univ. Tokyo Sect. II 9 (1): 1–192.

Mailleux, E., 1932. La Faune de l'Assise de Winenne (Emsian moyen) sur les Bordures meridionale et orientale du Bassin de Dinant. Mem. Mus. roy. d'Hist. Nat. Belg. 52.

Newell, N. D., 1937. Late Paleozoic Pelecypods: Pectinacea Publ. State geol. Surv. Kansas 10.

Novozhepov, N. E., 1956. Pal. Inst. Leningrad, Trudy Series, 61.

Raymond, P. E., 1946. The Genera of Fossil Conchostraca—An Order of Bivalved Crustacea. Bull. Mus. Comp. Zool. Harvard Coll. 96 (3): 218–307.

Sandberger, F., 1887. Ueber einen neuen Pelekypoden aus dem nassauischen Unterdevon. N. Jahrb. Min. Geol. Pal., Jahrg. 1887, 1 Bd: 247–9.

Shimer, H. W., and Shrock, R. R., 1944. Index Fossils of North America, New York: John Wiley & Sons.

Suggate, R. P. (in press). The Geology of Reefton Subdivision. N.Z. geol. Surv. Bull., 56.

Tasch, P., 1956. Three General Principals for a System of Classification of Fossil Conchostracans. J. Pal. 30 (5): 1248–57.

C. A. Fleming, N. Z. Geological Survey, Wellington, N.Z.