Tertiary Irregular Echinoids from the Chatham Islands, New Zealand,
[The material on which this paper is based was collected by the Otago Institute Party at the Chathams in January and February, 1924. Abstract read by Dr. J. Marwick before the Wellington Philosophical Society 22nd May, 1929; received by the Editor 5th June, 1929; issued separately, 17th August, 1929.]
My thanks are due to Mr. R. S. Allan for the opportunity of examing this small collection of Echinoids; although not sufficiently well preserved for complete identification, they are interesting enough to be described in some detail. The Regular Echinoids will form the subject of a future communication. Some particulars of the stratigraphy and localities have already been published by Dr. J. Marwick (1928 Tertiary Mollusca of the Chatham Islands ….; Trans. N.Z. Inst., vol. 58, pp. 432–506), who has discussed the age of the beds from the evidence of the mollusca. Mr. Allan proposes to give in the near future a full description of the stratigraphy of the Chatham Islands in the same publication. Reference should be made to these two accounts for definitions of the strati-graphical terms used in this paper.
I.—Echinoids from the Te Wanga Series.
Preservation. The matrix of the fossils from this series is of three types: a soft calcareous material; a hard, compact, crystalline, pink limestone; and secondary calcite. The latter has been deposited in crystalline continuity with the plates of the echinoid tests so that the sutures are prolonged through the covering and are visible at the surface where naturally weathered. If this caleite be partially ground away, leaving only a thin film, the pores become visible, with sometimes the sutures and occasionally the details of the ornamentation.
1.—Apatopygus aff. Recens (Milne Edwards).
Figures 1–5; text figures 1–7.
1836 Nucleolites recens Milne Edwards, in Cuvier, Règne Animal, Illus. Ed., Zoophytes, pl. 14, fig. 3.
1873 Echinobrissus recens (Milne Edwards), A. Agassiz, Revision of the Echini, Part 3; Mem. Mus. Comp. Zool. Harvard, vol. 3, pp. 556–7; pl. 14a, figs. 2–4; pl. 21b, figs. 1–2.
1920 Apatopygus recens (Milne Edwards), Hawkins, Geol. Mag. vol. 57, pp. 393–401; pl. 7, figs. 1–2.
1922 Echinobrissus (Oligopodia) recens (Milne Edwards), Mortensen, Vid. Meddel. Dansk natur. Foren., vol. 73, pp. 184–92, text-figs. 19–22, pl. 8.
Echinoids from the Te Whanga Series, north end of Red Bluff, six miles north of Waitangl.
Figs. 1–5.—Apatopygus aff. recens (Milne Edwards). Fig. 1; adapical surface; fig. 2: adoral surface; fig. 3: posterior view; fig. 4: right lateral view; specimen A. The dotted lines in figs. 3 and 4, indicate the position of the test along a vertical transverse section through the peristome, and along a vertical longitudinal section through the periproct and peristome. Fig. 5: adoral surface, specimen B.
Figs. 6–8.—Cardiaster?, sp. nov. Fig. 6: adoral surface; fig. 7: anterior view; the adapical region is slightly tilted away from the observer; fig. 8: right lateral view; dotted lines show an attempted restoration of the test, and a vertical longitudinal section showing the depth of the anteal sulcus.
Material. Of the two examples of this form, specimen A is complete the petals and apical disc being covered with secondary calcite, and the details of the base obscured; specimen B is broken (much of the adapical surface is missing), but shows the plating-structure of the base. Where not covered with a layer of secondary calcite, the specimens are weathered and the ornamentation partially destroyed; secondary calcite, deposited irregularly, often obscures the scrobicules and pores. For comparison, I have examined four dried specimens of the modern form, A. recens, in the Zoological Department of the British Museum (Natural History); my thanks are due to the keeper of that Department, and to Mr. C. C. Monro, for permission and facilities to investigate these specimens.
Locality. North end of Red Bluff, six miles north of Waitangi.
Description. The dimensions in mm. are:—
|Length (L).||Width (W).||100 W/L.||Height (H.)||100 H/L.|
|Longitudinal diameter.||Ternsverse diameter.|
|Periproct (specimen A)||4.5||3.0|
|Peristome (specimen B)||3.5||2.25|
Test depressed, adapical surface and ambitus rounded. Ambital outline oval to subpentagonal; the line of greatest width is excentric posteriorly. Periproct oval, longitudinally elongated; at the anterior end of the sulcus beginning at the ambitus (but not notching it). Peristome invaginate, subpentagonal, excentric anteriorly. Adoral surface undulate; interambulaera 1 and 4 are raised into slight prominences near the ambital margin. Ambulacrum 3 is in a broad shallow depression; the two similar depressions in which are situated ambulacra 1 and 5 coalesce near the peri-stome, by the suppression of the ridge into which interambulacrum 5 is raised towards the ambital margin. The size and shape of the petals are shown in figure 1; the outer pore of each pore-pair is slightly elongated and larger than the inner. There appear to be 24 and 25 pore-pairs respectively in each column of ambulacrum 3, and 26 to 28 in each column of ambulacra 1 and 5, and about 23 in each column of ambulacra 2 and 4. So much as can be deciphered of the plating-structure is shown in text-figures 1–7. In the apical disc, the posterior oculars appear to meet; irregularities in alternation are seen in the adapical parts of petals 2 and 3 (text-figure 2). The plates within the peristomial invagination are obscured by secondary calcite; the erratic weathering makes it somewhat difficult to determine the pores, which are usually filled with secondary calcite. The adapical transverse sutures of the plates bordering the peristome are to some extent hypothetical as shown in text-figures 3–7, but are based on the position of the pores; the adradial sutures are, however, quite distinct. The first three plates in each column of the paired ambulacra bear three or four pores in a straight line; these form the adoral portions of what are here termed the “inner columns” of pores. Above this, the plates are of three types:—
a demiplate, not reaching the perradial suture (near the peristome, this plate is sometimes represented by a primary).
a large primary, touching three (or, less usually, four) plates of the adjoining column.
a small primary (in one case—plate 5 of column 4b—this is represented by an occluded plate).
Plates of types A and B bear pores near the adradial suture, forming the “outer columns” of pores; plates of type C near the peristome bear their pores near the centre, and their pores thus continue the “inner columns” Traced towards the ambitus, the “inner columns” slope adradially to join the “outer columns”; when the columns merge, the pores are arranged triserially. Ambitally and adapically (outside the petals), the pores are irregularly uniserial. In ambulacrum 3 there is no distinction into “inner” and “outer columns”; on the adoral surface, the pores are triserial, but are uniserial and central near the peristome. There are no bourrelets.
The tubercles are weathered; but the better preserved are perforate, and some retain traces of crenulation.
Comparison with A. recens. The specimens closely resemble the modern New Zealand species Apatopygus recens (Milne Edwards). The values (relative to the length) of the width and height of the test, and of the dimensions of the periproct and peristome, fall within the range of variation exhibited by the specimen figured by Agassiz (op cit.) and by the examples in the British Musuem (Natural History); except that specimen B is slightly narrower. The peristome and apical disc are very slightly more excentric anteriorly than in the modern form. The shape of the adoral surface agrees with that of the British Museum specimens. The apical disc of A. recens has been figured by Mortensen (1922, op. cit., pp. 187–8 text figures 21 a, b), and by Agassiz (1873 op. cit., pl. 14a, figure 2), and shows a certain amount of variation. The apical disc of specimen A is of the same type as that figured by Mortensen in his text-figure 21a, in the protrusion of the oculars 2, 3 and 4 into the corona, and the complete separation of oculars 2 and 4 by the madreporite; but in Mortensen's figure the posterior oculars are separated, the genital pores extend outside the apical disc, and the madreporic pores encroach on the left anterior genital plate. In the figure given by Agassiz, the posterior oculars meet, as they appear to do in specimen A.
The ambulacral plating structure is identical in type with that described by Hawkins (1920, op. cit., pl. 7, figs. 1, 2) in A. recens, although there are differences, which examined in the light of Hawkin's morphogenetic theory (discussed below), possess varying degrees of significance. Thus the “trifling imperfection of alternation” in petal 3 of the modern form which “may well be but an individual irregularity” (Hawkins, op. cit., p. 396), is seen in both petals 2 and 3 of the fossil (text-figure 2). Of possibly more significance, is the absence of “Discoidiid” plating adorally in
Figs. 1–7.—Apatopygus aff. recens (Milne Edwards), Te Whanga Series north end of Red Bluff. Fig. 1: adoral surface, specimen B, × 1; fig. 2, apical disc, specimen A, × 10. Figs. 3–7: adoral parts of ambulacral, specimen B; fig. 3: ambulacrum 1; fig. 4: ambulacrum 2; fig. 5: ambulacrum 3; fig. 6: ambulacrum 4; fig. 7: ambulacrum 5; position of ambitus indicated by horizontal lines; × 3.5 (approx).
Figs. 8–12.—Apatopgus recens (Milne Edwards), recent; British Museum (Natural History). Fig. 8: ambulacrum 1; fig. 9: ambulacrum 2; fig. 10: ambulacrum 3; fig. 11: ambulacrum 4; fig. 12: ambulacrum 5.
Fig. 13.—Hypophyllode 3 of Trematopygus faringdonensis Wright, Lower Greensand Aptian, Faringdon, Berkshire, England; Sedgwick Museum Collection. × 5.
ambulacra 1 and 5 in specimen B. Differences in the distribution of “Pyrinid” plating are much more significant. In ambulacrum 4 of the fossil form, “Pyrinid” plating does not reach the ambitus (text-figure 6); unhappily in the Recent form examined by Hawkins the plating - structure of ambulacrum 4 was obscure in the region of the ambitus, although “Pyrinid” plating “seems not to reach the petals” (Hawkins, op. cit., p. 396). In ambulacrum 3 of the Recent form, “Pyrinid” plating reaches the petals; in the fossil form it certainly reaches nearly to the ambitus (text-figure 5); adapically the structure can not be ascertained, but there are indications that demiplates are absent. In ambulacra 1 and 5 of specimen B, of the 30 plates in each column below the ambitus, there are from 8 to 10 “Cidaroid” plates above the “Pyrinid” plates (text-figures 3, 7); in the recent form (Hawkins, op. cit., pl. 7, figure 1) in ambulacrum 1, there are below the ambitus 5 and 3 “Cidaroid” plates in each column respectively, out of 38 and 40. Thus in ambulacra 1 and 5 “Pyrinid” plating affects the fossil form to a less extent than the living form; and it is at least possible that a similar relation obtains in the other ambulacra.
The arrangement of the pores round the peristome has been described by Mortensen (1922, op. cit., pp. 184–5), and described and figured by Hawkins (op. cit., p. 395 et seq., pl. 7); the disposition as seen in two specimens in the British Museum (Natural History) is illustrated in text figures 8–12. In both these examples, the arrangement of the pores in ambulacra 2 and 4 may be regarded as intermediate in type between that in ambulacra 1 and 5, and that in ambulacrum 3; futher, in ambulacrum 3 the triserial arrangement of the pores appears at the fifth pore in each column, counting from the peristome. In all other respects, the fossil and the recent form here figured are similar. Mortensen states (op. cit.) that there are four columns of pores in all the “phyllodes”* in the specimen of the recent form which he examined; so that in this respect the recent form has in some examples the arrangement seen in the fossil form. Moreover, in the figure given by Hawkins† of ambulacrum 3 in the Recent form (Hawkins, op. cit., pl. 7, figure 2), the triserial arrangement of the pores appears at the seventh pore, as in the fossil (text-figure 5). It would seem, therefore, that the arrangement of the pores in the fossil can be paralleled amongst the variation exhibited in the living form.
The arrangement of the tubercles is similar in both the living and the fossil form. Mortensen states (op. cit., p. 188) that the tubercles in A. recens are perforate and crenulate; the tubercles in
[Footnote] *Mortensen's description applies probably to the paired ambulacra only; for in the two specimens examined by me, and in the form figured by Hawkins, there is no arrangement of the pores into four columns in ambulacrum 3.
[Footnote] †The figures given by Hawkins show the two pores in each of the plates at the peristomial margin in columns 1a and 3b, arranged sloping adradially and adorally. Mortensen's description, however, implies the arrangement here figured (text figures 8–12), in which both pores are central.
the British Museum specimens, and in the fossil form, are also perforate and crenulate.
Of the various differences between the fossil and the living form which have been discussed above, the most important is probably the difference in the extent to which “Pyrinid” plating affects ambulacra 1 and 5. That the ambulacra of the fossil form are less affected than those of the living form, affords support to the hypothesis, suggested by Hawkins (op. cit.), that A. recens is morphologically the end member of a series in which “Pyrinid” plating progressively affects the ambulacra to an increasing extent. Since, however, our knowledge of the plating-structure is founded on but one example of each form, and we are ignorant of the amount of variation which may exist in each, it seems better not to create a new species for the fossil form.
Comparison with other species. The genus Apatopygus is at present known to contain but one species. Of Australasian forms which superficially resemble A. recens, Nucleolites papillosus Zittel* is distinguished easily by the posterior sulcus, which nearly reaches the apical disc; the plating-structure (and consequently the true generic position) is unknown.
Discussion of Apatopygus and its affinities. The arrangement of the pore-pairs adorally in A. recens as described by Hawkins, and by Mortensen, and as here figured, are all to some extent different. In the specimens I have examined, the pores are arranged in four columns in ambulacra 1 and 5 (text-figures 8, 12); in ambulacra 2 and 4 text-figures 9, 11) the pores are triserial, but with a distinct tendency towards the arrangement in four columns, which is described in A. recens by Mortensen, and here figured in the fossil form (text-figures 4, 6).
It may be suggested that, in the specimen figured by Hawkins (op. cit., pl. 7, figure 1), the pores of plates 10 and 12 in column 1b, and of plates 5 and 12 in column 1a (counting from the peristomial margin) may be regarded as pores of the “inner columns”; the irregularity of the arrangement of the pores (as compared with that in specimens examined by Mortensen and myself) may be due to “irregularities” in the plating-structure—the interruption of the succession of “Pyrinid” plates by two groups of “Discoidiid” plates in column 1a, and the consequent “irregularity” in the adjacent parts of column 1b. Whether the normal arrangement in the posterior ambulacra of A. recens, is a regular succession of “Pyrinid” plates with four columns of pores, or the less regular arrangement with “Discoidiid” plates (as described by Hawkins), can only be determined by the examination of more material.
In either case, the diagnosis of Apatopygus, and the description of A. recens, must be revised in the light of the descriptions given here and by Mortensen, and of the examination of the fossil form.
[Footnote] *Zittel, 1864. Fossilen Mollusken und Echinodermen aus Neu-Seeland. Reise der Osterr. Frigatte Novara um die Erde, Geologischer Theil, Band 1, p. 62, pl. 11, figs. 2a-c.
Hawkins, in discussing the affinities of his genus Apatopygus (op. cit., Geol. Mag., 1920, pp. 397–8), recognises in the Nucleolitidae (s. str.) four types which “illustrate a morphogenetic sequence”:—
Lower Oolite; example, Nucleolites quadratus (see Hawkins, 1920, Phil. Trans. Roy. Soc. Lon., Series B, vol. 209, pl. 68, figure 2).
Upper Oolite; N. scutatus (op. cit., pl. 68, figure 3).
Cretaceous; Trematopygus faringdonensis Wright (op. cit., pl. 68, figure 4).
Recent; A. recens (Hawkins, 1920, Geol. Mag., op. cit., pl. 7, figures 1, 2).
Comparison of the figures quoted above shows that in this morphological sequence, in the hypophyllodes* of Nucleolites and the corresponding areas in the other genera.
(a) the arrangement of the pores is modified. In types 1 and 2, there are four columns of pore-pairs; in type 3, the pore-pairs are irregularly triserial; while type 4 resembles type 3, except that near the peristome the pores are central.
(b) the shape of the region changes. In types 1 and 2, the hypophyllodes are slightly expanded and become narrow at the peristome. In type 3, the ambulacra narrow steadily from the ambitus to the peristome. In type 4, the ambulacra are similar, but expand at the peristomial margin.
Since such a morphogenetic sequence may throw light on the problem of determining the age of the fossil form A. aff. recens, it is unnecessary to offer excuses for recording further information concerning the European species on which the sequence is in part founded. The specimens of A. recens in the British Museum (Natural History), mentioned above, and examples of Trematopygus faringdonensis both in the same Museum, and in the Sedgwick Museum, Cambridge, differ in some respects from the figures given by Hawkins. In the specimens of T. faringdonensis which I have examined, the pore-pairs in each hypophyllode† are arranged in four columns (text-figure 13) as in types 1 and 2. In Apatopygus (type 4), there is an increase in the number of plates near the peristome which bear central pores; this is probably connected with the more marked invagination of the peristome in Apatopygus, as compared with that in Trematopygus. The width of the paired ambulacra is less in the region of these plates than in the region bearing four columns of pores. Above these plates, the pores are arranged as in type 2 in ambulacra 1 and 5 but all trace of phyllodal characters is lost in ambulacrum 3. The evidence of these specimens thus strengthens the hypothesis of a morphogentic sequence.
One of the changes seen in this sequence occurs in the extra-petaloid parts of the ambulacra; the pore-pairs of types 1–3 (Lower Oolite to Cretaceous) are replaced by single pores in type 4 (Recent). Lambert has described a species of the related genus
[Footnote] *This term was introduced by Hawkins, 1911, Geol. Mag., p. 260.
[Footnote] †Compare Hawkins, 1911, Geol. Mag., p. 260, pl. 13, fig. 5.
Clitopygus (C. marticensis; Santonian, S. France) in which “les plaques ambulacraires deviennent uniporifères entre les pétales et la face inférieure.” (Lambert and Thiery, “Essai de Nomenclature Raissonnée Echinides:” 1921, fasc. 5, p. 345; diagnosis of species, p. 347 footnote; and 1924, fasc. 6 and 7, pl. 10, figs. 1–3). Of another species of an allied genus, Nucleopygus coravium Defrance (Aturien), Lambert and Thiery state (1921, op. cit., fase. 5, p. 347) that the plates “avaient commencé à devenir uniporifères.”
2.—Cardiaster?, sp. nov.
Figures 6–8; text-figures 14–17.
Material. One specimen, showing part of the adapical surface, and the anterior region with a portion of the margin of the peristome. The measurements and description of the shape are therefore of necessity based on the attempted restorations shown in the figures. The holotype of “Cardiaster” tertiarius Gregory has been examined and parts of the ambulacra figured for purposes of comparison; my thanks are due to the Keeper of the Geological Department of the British Museum (Natural History), and to Mr. T. H. Withers, for permission and facilities to examine this specimen (registered E 3382). Although the material is poor, it is described in some detail as a contribution to our scanty knowledge of the Tertiary Australasian members of a family which in other regions flourished and became extinct in Cretaceous times.
Locality. North end of Red Bluff, six miles north of Waitangi.
Description. The dimensions in mm. are estimated as:—
|Length (L).||Width (W).||100 W/L.||Height (H).||100 H/L|
Adapical surface tumid, with apical disc at ?highest point. Anteal sulcus extending almost to the apical dise, and into the peristome; bordered by two slight carinae. Peristome almost vertical
the anterior margin being situated in a deep depression. Apical disc typical of the family (text-fig. 14). Ambulacra 2 and 4 curve anteriorly from the apical disc towards the ambitus, ambulacra 1 and 5 curve posteriorly to a less extent. The details of the parts of the subpetals preserved are shown in text-figures 16 and 17.
Each column of the paired ambulacra figured differs in the maximum size of the pores and width of the pore-pairs: and in the relative position in the column at which
(1) the pore-pairs attain their maximum width
(2) the pore-pairs attain the centre of the column, having moved (when traced ambitally) from near the adradial suture. Further, in the posterior columns the outer pore of each pore-pair is more elongated and larger than the inner. Ambulacrum 2, which alone of the paired ambulacra is preserved from the apical disc as far as the ambitus, possesses about 37 pore-pairs in each column above the ambitus; just above the ambitus the pores have become smaller and each pore-pair contracted while the plates are 2.5 mm. high. In ambulacrum 3 (text figure 15) the pores are minute and circular, and the two pores of each pore-pair are separated by a granule. The tubercles are small, perforate and crenulate; larger and sparser immediately below the ambitus anteriorly, larger and more crowded on the carinae and ambitus. Granules occur on the whole surface of the test.
Discussion and comparison. The generic characters agree with those of species usually placed in the Holaster-Cardiaster group (“tribu Cardiasterinae” of Lambert and Thiery, 1924, Essai de Nomenclature Raisonnée Échinides, fasc. 6 and 7, p. 401). There is no trace of a marginal fasciole on the only portion of the test preserved which might show it, but in Cardiaster the fasciole is often not visible round the anteal sulcus in specimens in which it is well-marked posteriorly (compare, for instance, Forbes' description of C. granulosus Goldfuss sp., 1852, Mem. Geol. Survey British Organic Remains, Decade 4, pl. 9 and text). The plastron, the plating-structure of which distinguishes Sternotaxis, Cardtiotaxis and Aurelianaster (Lambert and Thiery, op. cit., pp. 405–6, 589) from other genera of the group, is not preserved. The specimen closely resembles “Cardiaster” tertiarius Gregory (1890, Geol. Mag., pp. 484–5, pl. 14, figs. 2–3) from the “Murravian, south of Adelaide, Australia.” In the holotype of this species the slope from the apical disc towards the truncated posterior portion as seen in profile, appears more gentle than in the Chatham Island form; further, in “C.” tertiarius the two pores of each pore-pair in ambulacral columns, 1a, 2a, 4b and 5b, are equal in size (text-figures 18 a, b.) According to the original diagnosis, Cardiaster Forbes (1850, Ann. Nat. Hist. 6, pp. 443–4) differs from Holaster in the possession of a marginal fasciole and a deep and steep-sided anteal suleus. Forms with slight carinae and without the fasciole are often placed in the genus Holaster. In describing Cardiaster tertiarius, Gregory states that “……as is so often the case in this genus [Cardiaster], the fasciole cannot be seen; nevertheless the general form, the deep anterior groove, and the tuberculation, leave no doubt of its correct generic position.” Since the plastron of the holotype of “C.” tertiarius is not sufficiently well preserved for the plating-structure to be determined, the specimen can not be generically identified, and may be left provisionally in the genus in which Gregory has placed it.
Of extra-Australasian specimens, Cardiaster orientalis Stoliczka (1873, Pal. Indica, Ser. 8, Cret. Fauna S. India, vol. 4, No. 3, Echinodermata, p. 22, pl. 4, figs. 1–2) from the “Arrialoor Beds,” closely resembles the Chatham Island specimen.
The age of the Te Whanga Series. The close approximation of A. aff. recens to the living form A. recens (Milne Edwards) suggests that the Te Whanga Series is not older than Upper Tertiary. But of the features which distinguish Apatopygus, “Pyrinid” plating-structure is well established in the Lower Cretaceous Trematopygus faringdonensis, and single pores in the extra-petaloid parts of the ambulacra are seen in the Upper Cretaceous Clitopygus marticensis and Nucleopygus coravium; the possibility of the appearence of Apatopygus in the Lower Tertiary must not be overlooked.
Figs. 18a, b.—“Cardiaster” tertiarius Gregory; Murravian, south of Adelaide, Australla. Holotype, British Museum (Natural History), E. 3382. Fig. a: subpetal 1; fig. b: subpetal 2. × 5.
Cardiaster?, sp. nov. belongs to a group which in the northern hemisphere is characteristic of the Cretaceous, but which has been proved to occur in the Tertiary of Australia. It seems more reasonable to suppose that it would occur in the Lower Tertiary than in the Upper; unfortunately there is a considerable difference of opinion among Australian Geologists as to the exact horizon (expressed in terms of the European time-scale) at which “Cardiaster” is found.
Mr. Allan informs me that “stratigraphically the Te Whanga Series lies unconformably below a series of fossiliferous tuffs and intercalated limburgities, for which the mollusca determined by Dr. J. Marwick (op. cit., supra) suggest an Upper Oligocene age.”
II.—Echinoids from the Tioriori Series.
Locality. Waikaripi, cliffs south of Wireless Station.
1. A broken specimen, about 21 mm. in length, is referred without doubt to the genus Apatopygus. It is preserved in soft white limestone, and the adoral surface is covered with secondary calcite. The anterior portion is missing, the apical disc, the region surrounding the periproct and part of the adoral surface. It closely resembles the form described above as A. aff. recens, in the description of which it has not been utilised since it is possibly not identical. In ambulacrum 1 there are seven and eight “Cidaroid” plates respectively in each column below the ambitus and above the “Pyrinid” plates.
2.A second broken specimen is not sufficiently well preserved for discussion.
Mr. Allan informs me that the position of the Tioriori Series in the rock sequence as developed in the Chatham Islands could not be adequately demonstrated. It may possibly be equivalent to the Te Whanga Series.
The specimens here described will be preserved in the Otago University Museum, Dunedin.