A New Nautiloid Species, Cimomia zelandica, from New Zealand

Transactions of the Royal Society of New Zealand : Earth Sciences, Volume 8, Issue 5, 19 July 1970, Page 69

A New Nautiloid Species, Cimomia zelandica, from New Zealand

M. R. Johnston

By

N.Z. Geological Survey,

Department of Scientific and Industrial Research

[Received by the Editor, 21 May 1969 ]

Abstract

The genus Cimomia has not previously been recorded from New Zealand. Four New Zealand specimens belonging to this genus, ranging from the Albian to Oligocene in age, are placed in the new species C. zelandica. A brief description of two Upper Cretaceous (Mata Series) specimens of Eutrephoceras sp. is given.

Introduction

During mapping of the Tinui District, eastern Wairarapa, a nautiloid was collected from a 38cm concretionary boulder in rocks attributed to the Albian, in the head of Mangapakeha Stream. The nautiloid was found to be similar to three others in the New Zealand Geological Survey collection; from the Ngaterian (Genomanian-lower Turonian) at Coverham, Clarence Valley, from the Kaiatan (Upper Eocene) near Westport, and from the lower Landon Series (Oligocene) of Otapiri River, Southland.

Post-Trias sic Nautiloids

Kummel (1956), in an extensive review of the post-Triassic nautiloids, drew attention to their essential homogeneity and placed them in the family Nautilidae. The ancestral stock of the Family is represented by the genus Cenoceras from which “. . . directly or indirectly, all post-Triassic nautiloids are derived ” (Kummel, 1956: 327). This Cenoceras stock was one of great plasticity and gave rise to several distinct evolutionary lines with specialisation of one or more morphological features. The most persistent and stable evolutionary line was the subfamily Nautilinae, represented by the genus Eutrephoceras which has a weakly sinuous suture. Kummel considered that there were a series of radiations from the Eutrephoceras stock one of which involved increasing sinuosity of the suture and gave rise to the subfamilies Hercoglossinae and Aturiinae.

Kummel (1964) raised the subfamilies to family status and the family Nautilidae to superfamily status. The family Aturiidae contains the single genus Aturia of which the New Zealand occurrences have been documented by Fleming (1945) and Beu (1968). The family differs from the Hercoglossidae and the Nautilidae in that the siphuncle is close to the dorsal side of the chamber, rather than being approximately central. The family Hercoglossidae contains Cimomia, which has a

slightly sinuous suture, and Hercoglossa, in which the sinuosity of the suture is more marked.

Although Kummel (1956) did not doubt that Cimomia arose from Eutrephoceras, the evolutionary path is not clear. He stated (1964, p. K 456) : “ [the] genus is a morphologically transitional form between Eutrephoceras and Hercoglossa ” There are many gradational forms, and it is not known whether the Hercoglossidae had a single origin during the late Jurassic, or whether the morphological forms included in the Hercoglossidae evolved several times during the Cretaceous.

Kummel (1956: 330) stated that most nautiloid species are defined from one or a very few specimens, new species are based on slight variations of the shell or suture line, and because of this the “ so-called species . . . have little reality in terms of our concept of neontological species.” However, specimens from all around the world must be identified, and, as the phylogeny of the nautiloids is largely unknown, the only practical way to deal with the fossils is to introduce new species names where necessary. The four New Zealand specimens, described in this paper as a new species, are assigned to the genus Cimomia and the taxonomic classification of Kummel (1964) is adopted.

Superfamily NAUTILACEA Family HERCOGLOSSIDAE Genus Cimomia Conrad, 1866

Type species (by original designation): Nautilus burtini Galeotti, 1837, Eocene, Belgium.

The genus has not previously been recorded from New Zealand, but is known from Australia (e.g., Glenister et al, 1956; McGowran, 1959). It contains many species, and Kummel (1964: K 456) described it as being cosmopolitan and as ranging from Upper Jurassic to Oligocene. The comprehensive diagnosis of the genus by Miller (1947: 39-40) need not be repeated.

Cimomia zelandica n.sp., PI 1, Figs. 1-5; Text-figs. la-d.

Material: Holotype, CE 2243, GS 9943 (Nl5B/657), N.Z. Geological Survey, Lower Hutt; a well-preserved, almost complete specimen, in which the body chamber has been crushed prior to preservation.

Paratypes, CE 2246, GS 3794 (535/524), N.Z. Geological Survey, Lower Hutt, a specimen comprising half the outer whorl, including part of the body chamber; a small part of the inner layer of the shell remains. CE 2244, GS 7056 (S3l/631), N.Z. Geological Survey, Lower Hutt, a small well-preserved, almost complete specimen. CE 2245, GS 10179 (5169/935), N.Z. Geological Survey, Lower Hutt, an internal mould of a body chamber which shows a complete suture of the most adoral septum.

Specific Diagnosis: The shell attains a diameter of at least 130 mm and is subglobular, with a gently inflated outer whorl section which is slightly wider than high (PI. 1, Fig. 2). The venter is more rounded than the flanks and there is a distinct ventrolateral shoulder. The umbilical shoulder is strongly rounded, and the umbilical walls are steep. The umbilicus is moderately wide, sub-circular in shape, with a maximum diameter about a seventh of that of the whole shell, and is not filled by callus.

The body chamber occupies approximately half the last whorl. On one side of the mould of the body chamber of CE 2245 there is a large muscle scar in the posterolateral position (PI. 1, Fig. 5). The adorally concave septa are not closely spaced, and there are approximately 14 in the outer whorl of the holotype and nine in the outer whorl of the smallest of the paratypes (CE 2244). Each suture is sinuous, but not markedly so (Text-fig. la-d). It has a low, broad ventral saddle flanked by a rounded lateral lobe, and a narrowly rounded saddle immediately outside the umbilical shoulder. In CE 2245 a narrowly rounded lobe, on the umbilical wall, extends to a small saddle and a broad dorsal lobe, in the centre of which there is a small, distinct V-shaped annular lobe.

The siphuncle is sub-circular in cross-section and is flattened laterally, except in paratype CE 2244 where it is circular, and septal necks are preserved. The position of the siphuncle is central in two of the paratypes, CE 2244 and GE 2245, and is slightly nearer the dorsum than the venter in the other two.

The surfaces of the internal moulds are almost smooth, the only prominent markings being the sutures. Shell is preserved on the holotype and on paratypes (GE 2244 and CE 2246) and is thicker on the umbilical region than on the venter. The thickness of the shell on the last whorl of the holotype is 2.5 mm and on the venter of the last whorl of CE 2244 is o.Bmm.

Two layers, corresponding to the outer, thinner, porcelanous ostracum and the inner, thicker, nacreous layer of present-day nautiloids, can clearly be seen. In the holotype a third, thinner, layer forms the exterior of the shell. The interior of the shell bears low, very indistinct, transverse and longitudinal lirae and striae. On the external surface there are well-marked growth lines, stronger on the holotype, with a deep hyponomic sinus. On the venter of GE 2244 there are longitudinal lines weaker than the growth lines. The shell on the ventral quarter of the outer whorl of the holotype is undulated, the undulations corresponding to the position of the underlying sutures at the apex of the hyponomic sinus. Adorally from the sinus, the growth lines extend well in front of the sutures.

Dimensions (in millimetres) : Table 1.

Localities and Ages: The holotype, CE 2243, was found in a concretionary boulder in the head of Mangapakeha Stream (grid ref. Nl5B/398728). The rocks cropping out, dominantly unfossiliferous grey siltstone with scattered graded beds, sandstone lenses, and concretions, have been mapped by the writer as the Makirikiri Formation of ?Urutawan-Motuan (Albian) age (Johnston, in prep.). A foraminiferal sample (Nl5B/758) o.Bkm downstream from the nautiloid locality contains a fauna attributed to the Clarence Series (Albian—lower Turonian) (P. N. Webb, pers.comm.). There is no evidence to indicate that rocks other than Motuan in age crop out in the upper Mangapakeha Valley.

Paratype GE 2246 was collected at Sawpit Gully (grid ref. 535/c154480) by B. H. Mason from the “ Sawpit Gully Mudstone ” (now redefined as the Swale Formation, G. J. Lensen, pers. comm.), at Coverham, and was associated with Inoceramus aff, tawhanus Wellman, indicating a Ngaterian (Cenomanian-lower Turonian) age.

Paratype CE 2244 was found in a loose concretion in a road cutting at the eastern end of the Lower Buller Gorge (grid ref. S3l/329599) by a Ministry of Works Engineer. It seems likely that the concretion was derived from the Kaiata Siltstone which crops out in the cutting and is Kaiatan to Runangan (Upper Eocene) in age.

Paratype CE 2245 was collected by J. H. Wilson from the Winton Marls cropping out in Otapiri River (grid ref. 5169/450347). The age of the Winton Marls is lower Landon Series (lower Oligocene) (McKellar, 1969).

Remarks: The four specimens are similar in shape, in suture pattern, and in umbilical form. The two Tertiary specimens differ in that their siphuncles are more rounded and closer to the dorsum, and that the longitudinal markings on their shells are more pronounced than in the Cretaceous specimens. Future work with better material may warrant the placing of the Tertiary specimens in a separate species. The specimens are mature animals, except for CE 2244, which is probably immature.

Comparison and Affinities

Cimomia zelandica is similar in form to Eutrephoceras allani (Fleming), which has a deeper umbilicus than was shown by Fleming (1945, text-fig. 2b). It differs in that E. allani has a smaller umbilicus than Cimomia zelandica, and its umbilicus is filled with callus, whereas that of C. zelandica is open. The sinuosity of the suture is difficult to determine in the single known representative of E. allani, but it appears to be less sinuous than in C. zelandica, and also to lack an annular lobe.

The new species is similar to Cimomia tenuicosta Glenister, Miller and Furnish, from the Upper Cretaceous of Australia, but differs in being less inflated, in the suture being less sinuous, and in the umbilicus being larger and lacking a callus. It is also similar to C. wylliei (Newton) a large species (380 mm diameter) from the Eocene of North Africa (Haas and Miller, 1952). C. zelandica is smaller and less inflated, has a better defined lateral lobe and saddle (Fig. le), and has a higher siphuncle than in C. wylliei.

Matsumoto (1967: 167) has redefined Nautilus sublaevigatus var. indica Spengler (Spengler, 1910: 137) under the name Cimomia indica (Spengler).

Spengler’s specimens from the Cretaceous of India had originally been described by Blanford (1861: 13, pi. 5, fig. 1) as Nautilus bouchardianus (Eutrephoceras bouchardianus (D’Orbigny, 1840), Lower Cretaceous, France; Kummel, 1956: 380). C. zelandica n.sp. is similar to C. indie a, particularly in the sinuosity of the suture (Fig. 2f), but is considerably less inflated. The new species resembles the Paleocene North American species C. subrecta Miller and Thompson and C. vestali Miller and Thompson in suture, but differs in its more widely spaced septa and more prominent umbilicus.

In describing Eutrephoceras kobayashii, Matsumoto (1967: 167-8) has pointed out that the sinuosity of the sutures (Fig. Ig) was greater in the earlier part of the outer whorl than in the later part. Although he thinks this may imply a close relationship between Eutrephoceras and Cimomia, he attributes the change in sinuosity to “ a low and asymmetric lateral lobe rather than from elevating lateral saddles ” and considers that the sinuosity may foreshadow that of Nautilus. In Cimomia zelandica n.sp. the suture does not vary in sinuosity in different parts of the outer whorl.

Present-day nautiloids inhabit shallow water, lack a pelagic larva, and are therefore geographically restricted, although empty shells drift far from the animals’ habitat. The population of Cimomia zelandica was probably restricted to the southwest Pacific.

Eutrephoceras sp. (PI. 2, Figs. 1-4). During this research two specimens of Eutrephoceras were examined, 1 but because of insufficient material neither was placed specifically, A brief description of both is given.

Material: GS 13 (555/25), New Zealand Geological Survey, Lower Hutt, a small, almost complete specimen, with part of the shell preserved. It was in a beach pebble collected by A. McKay from Amuri Bluff. C 697 (N2B/626), University of Auckland, is a large, almost complete but distorted specimen in which the septa have been crushed during compaction; some shell material is present. Collected at Bulls Point, North Auckland, by an Auckland University field party.

Description : Both shells are subglobular, with whorls broadly rounded ventrally and laterally, and expand rapidly adorally. The umbilicus is small and deep with rounded umbilical shoulders.

In GS 13 an umbilical plug is present, but the umbilicus of G 697 is not visible. In both specimens only the adapical part of the body chamber is preserved. The adorally concave septa are moderately widely spaced, but have been severely crushed and distorted in C 697. The suture in both is essentially straight. The central siphuncle is circular in cross-section, and in GS 13 is orthochoantic. Dimensions (in millimetres): Table 11.

Localities and Age: GS 13 was collected from a beach pebble, under a slip, at Amuri Bluff, Marlborough (grid ref. 555/c800738), which is composed of rocks of Mata age. The specimen is most probably from the Piripauan (Campanian) (I. G. Speden, pers.comm.). C 697 is from rocks of Mata (CampanianMaastrichttian) age exposed at Bulls Point, Kaipara, North Auckland (J. A. Grant-Mackie, pers.comm.).

Remarks : Both specimens have a similar shape, but G 697 has a wider umbilicus and the siphuncle is closer to the dorsum than in GS 13. Acknowledgments The writer is indebted to Dr A. G. Beu and Dr G. A. Fleming, New Zealand Geological Survey, for constructive criticism of the manuscript.

References Beu, A. G., 1968. A specimen of the Nautiloid Aturia from the Kapitean Stage (Uppermost Miocene) of New Zealand. N.Z. Jl. Geol. Geophys. 11(1): 161-5. Blanford, H. F., 1861. In Blanford, H. F.; Stolicka, F. The fossil Cephalopoda of the Cretaceous rocks of Southern India ; Belemnitidae-Nautilidae Mem. geol. Surv. India ( Palaeont. Indica), Ser. 1: 1-40.

Fleming, G. A., 1945, Some New Zealand Tertiary cephalopods. Trans. R. Soc. N.Z. 74: 411-18. Glenister, B. F.; Miller, A. K.; Furnish, W. M., 1956. Upper Cretaceous and early Tertiary nautiloids from Western Australia. /. Paleont. 30: 492-503. Haas, O.; Miller, A. K., 1952. Eocene nautiloids of British Somaliland. Amer. Mus. nat. Hist. Bull. 99; 317-54.

Johnston, M. R. (in preparation). Sheet N 159 —Tinui. “Geological Map of New Zealand 1 : 63,360.” New Zealand Department of Scientific and Industrial Research. Kummel, 8., 1956. Post-Triassic nautiloid genera. Bull. Mus. comp. Zool. Harv. 114(7): 324-494. Cephalopoda, Nautiloidea.

McGowran, 8., 1959. Tertiary nautiloids (Eutrephoceras and Cimomia) from South Australia. /. Paleont. 33: 435-48. McKellar, I. C., 1969. Sheet S 169—Winton. “ Geological Map of New Zealand 1 : 63,360.” New Zealand Department of Scientific and Industrial Research. Matsumoto, T., 1967. A Cretaceous nautiloid from Urakawa, Hokkaido. Jap. J. Geol. Geog. Trans. 38: 163-9.

Miller, A. K., 1947. Tertiary nautiloids of the Americas. Mem. geol. Soc. Am. 23: 1-234. Spengler, E., 1910. Untersuchungen iiber die sudindische Kreideformation: Die Nautiliden und Belemniten des Trichinopolydistrikts. Beitr. Palaont. Osterreich—Ungarns und Orients 23: 125-57.

M. R. Johnston, N.Z. Geological Survey, Nelson, New Zealand.

* Calculated.

1. Since this paper was written another nautiloid (GS 10528, Nl4l/1508), discovered in a loose concretion on Kairakau Beach, Southern Hawke’s Bay, by Mr P. Trask, has been lodged at the New Zealand Geological Survey. It is similar in shape to GS 13 and C 697, is slightly smaller than G 697, and can be assigned to the genus Eutrephoceras. It differs from GS 13 and G 697 in that it has a gently sinuous suture and is thus similar to E. kobayashii Matsumoto. It is not sufficiently well preserved to permit definite correlation with this species, the outer whorl being severely crushed before preservation. Although the age of the nautiloid is unknown, the presence on the beach of numerous similar concretions containing Inoceramus bicorrugatus Marwick indicates that a Mangaotanean (Coniacian—Santonian) age is likely (G. R. Stevens, pers. comm.).

* Calculated.

DIAMETER WHORL (at Diameter SIPHUNCLE At septum Calculated maximum Width (W) Height (H) W> /H of umbilicus Height Width , Distance from venter (V) Median height (M) M /V CE 122.0 140 69.8 67.1 1.04 19 5.7 4.5 32.1 46.7 1.45 2246 type — 100 45.0* 42.0 1.07* 3.1 2.4 16.6 23.1 1.37 ? 3.1 2.4 16.6 23.1 1.37 2244 type 110.0 74 29.1 26.6 1.09 10 2.9 3.0 10.9 21.8 2.00 2245Paratype — 130 52.7 47.8 1.10 4.0 3.6 16.8 34.6 2.06 ? 4.0 3.6 16.8 34.6 2.06

Table I.—Dimensions of Cimomia zelandica.

Diameter Width Height of W/ Distance Median M/ (W) Whorl (H) /H from venter height of Tv (V) Whorl (M) \ y. (V) Whorl (M) GS 13 61.5 52.0 45.0 1.15 7.2 13.6 1.88 G 697 165.0 128.0* 121.0* 1.07 47.5 60.5 1.28

Table 11.—Dimensions of Eutrephoceras sp.