Observations on the Asteroid Fauna of the Danian.

Transkript

1 Observations on the Asteroid Fauna of the Danian. By H. WiENBERG RASMUSSEN.. A description of the asteroid fauna of the Cretaceous deposits of Denmark was given by the late K. BRÜNNICH NIELSEN Ph. D. in In this work, which has greatly helped and inspired me in the course of my investigations, BRÜNNICH NIELSEN was unable to deal with some rather comprehensive collections, brought together during the last few years, so that the description, more particularly as far as the upper Danian is concerned, is not 'exhaustive. By means of the above-mentioned new collections the knowledge of the asteroids in the Danian is now so greatly increased that all more common species may be considered known. I am therefore of the opinion that a description of the new observations will prove to be of interest. A considerable part of the material used was collected by Professor A. ROSENKRANTZ and comprises collections from Fakse, partly from a variety of the coral limestone, where the fossils are remarkably well preserved, partly from a boring through the Danian at the brewery. From the uppermost Danian limesand at Copenhagen (Enghave Brygge, Knippelsbro, Svanemøllen and Teglholm) a rather comprehensive collection has moreover been placed at my disposal. For access to this material I extend my cordial thanks to Professor ROSENKRANTZ. TO the Keeper of the Palæontologicai Department of the Mineralogical and Geological Museum at Copenhagen, Professor CHE. POXJLSEN Ph. D. I am greatly indebted for the permission to include the large asteroid collections of the Museum in my investigations. Finally, I am very grateful for the support given towards my collections at Stevns cliff, Kagstrup, Trælløse and Herfølge by a grant from the JAPETFS STEENSTRUP Fund. 29»

2 418 H. WiENB.ERG RASMUSSEN: Observations on the Asteroid Fauna First of au, mention should be made of some biological data. Evidence of attacks made by other animals is well known in the case of the echinids, where the shells now and then bear the marks of bites and borings. The presence of such marks on the asteroids is unknown up to the present, identifiable marks of bites being more difficult to recognize on the comparatively small surfaces. In the extraordinarily well preserved material from the coral limestone at Fakse I have, however, recognized several undoubted bite marks. A couple of plates here show distinct grooves from bites, and on one plate, fig. 1, a weu-defined star-shaped bite is visible. From Fakse a plate has furthermore been observed of a completely deviating type. It resembles an ordinary marginal plate of a Metopaster, but one end of the plate has been cut off obliquely, and instead of the articular facet a free, ornamented surface has developed. This pecukar plate fig. 2 was undoubtedly produced by regeneration, after the distal part of the arm had been bitten off. A supposed regeneration in fossil asteroids was formerly observed by MERCIER 1935 p. 28. A peculiar phenomenon, of which mention has been made by several authors, is the broken-down terminal supra-marginaha in' the genus Metopaster. This genus is characterized by its ornamentation and by having large terminal supra-marginaha, which correspond with several infra-marginalia and may be supposed to be due to a fusion of several embryonic plates. As to these plates SPENCER writes 1913 p. 108: "In catagenetic varieties, however, the plates may be broken down into their primitive constituent ossicles..." SPENCER is of the opinion that the large terminal supra-marginalia vary in appearance within the individual species, and that they may be entirely wanting, so that "radiate" varieties with several supernumerary marginal plates normally correspond to the species of Metopaster. He therefore regards the terminal supra-marginaha as useless from a systematic point of view, and here exclusively relies on the median marginalia. In the monograph of BRÜNNICH NIELSEN 1943, the editors in a footnote disassociate themselves from the term of "broken-down terminal plates" and put forward the opinion that the plate shown by BRÜNNICH NIELSEN as an example of this phenomenon is only a fragment. On closer inspection this, however, proves not to be the the depressed border of the free surface curves round and distinctly follows the proximal margin. When going over the literature and the material at our disposal

3 Medd. fra Dansk Geol. Forening. København. Bd. 10 [1944]. 419 it appears that the terminal supra-marginalia in the genus Metopaster are practically speaking quite constant and a decisive systematic characteristic, whereas the forms which SPBNCEE terms "var. radiatus" are not the result of a breaking-down of the terminal marginaha into numerous small plates, but, as was shown by BRÜN- NiCH NIELSEN, belong to a distinct separate genus, viz. the Recurvaster. On the other hand, the terminal supra-marginalia are sometimes a little smaller and lack one or two facets corresponding with infra-marginaha, there being at the same time one or two supernumerary median supra-marginalia. This is illustrated by SLADEN and SPENCEE, 1908, plate 11 fig. 2, plate 12 fig. 1 and figure in the text p. 98, and mention is also made of it in the text. Finally, a species Metojxister dividuus is mentioned below,, being characterized by a simple breaking-down of the terminal supra-marginalia. In connection with this is also mentioned a terminal supra-marginal plate fig. 6, which seems to have adjoined a broken-down supramarginal plate on the other side of the arm. Metopaster dividuus n. sp. Figures 3, 4 and 5. At the base of the Paleocene series of beds in the harbour of Copenhagen there is a conglomerate, which chiefly consists of derived Danian fossils from the limesand. Through washing and sifting a material of this kind, which was created by the excavations at Svanemøllen, a great number of asteroid plates have been brought to light. These i. a. comprise numerous plates of a Metopaster, nearly all of them in a fine state of preservation, smooth and shining. As practically no other species of Metopaster occur in this bed, there is no doubt that the plates belong to one and the same species. It is also easy to undertake a combination of the various marginalia. The median supra-marginalia are evenly and strongly vaulted with a faint abactinal tumidity. The proportions length/ width/ height have been measured at 3.5 /~3.7 / 3.2 mm. Corresponding with these there are distal plates, a little larger and, hke the median ones, each only corresponding with one infra-marginal plate. Viewed from the abactinal side they are pentagonal in outhne, the side towards the body of the animal being divided into two parts, a proximal one

4 420 H. WIENBERG RASMUSSEN: Observations on the Asteroid Fauna towards the body with small facets adjoining the small abactinal covering plates, and a distal one which consists of a single oblique facet adjoining the corresponding plate on the opposite side of the arm. This characteristic plate cannot have been the terminal one, but shows a relatively large facet, which must have been adjacent to a small terminal supra-marginal plate. In this species there is thus (figure 3) a row of supra-marginaha, fairly equal in size, which towards the extremity of the arm end in a larger subterminal supramarginal plate, deviating in appearance and succeeded by a quite small terminal supra-marginal plate, the extremity of the arm finally consisting of an unpaired terminal plate. Infra-marginalia are of dimensions similar to supra-marginaha, and so there is no large terminal infra-marginal plate as there was in the genus Ravniaster. The plates are more flattened, not vaulted as the supra-marginaha. The ornamentation is that usually found in Metopaster, with a narrow depressed border and scattered small circular spine pits on the free surface. This species has not the curve of the arms which is so characteristic of Recurvaster, and is accompanied by an increasing obhquity and a modified ornamentation of the distal plates; nor can it, as already demonstrated, be referred to the genus Ravniaster. In spite of its deviations this asteroid is most nearly related to the genus Metopaster. It must be imagined as having developed from a norma] Metopaster by a cleaving of the terminal supra-marginal plate. A single plate from Svanemøllen serves as an example that such a process may take place. It is a terminal supra-marginal plate, which deviates from that of the normal Metopaster by having not one but two large facets for supra-marginalia on the face towards the median Une of the arm. Thus the opposite side of the arm in question cannot have had any large terminal supra-marginal plate, but must instead have had.two smaller plates, as shown in the combination figure 6. Horizon and localities. Younger Danian. Zone with Tylocidaris vexillifera. Svanemøllen, Trælløse and Herfølge.

5 Medd. fra Dansk Geol. Forening. København. Bd. 10 [1944J. 421 Ravniaster pianus, BB. NIELSEN. Figures 7 and Ravniaster pianus BRÜNNICH NIELSEN p Ravniaster carinatus BRÜNNICH NIELSEN p. 52. After examining a fairly large number of Ravniaster plates, particularly from the coral limestone at Fakse, I began to suspect that two of the species described by BEÜNNICH, NIELSEN from, the Danian are plates belonging to one and the same species, there being only two common types of Ravniaster plates in the Danian, one of which represents the supra- the other the infra-marginalia. Both types agree with the holotype of R. planus, whereas most of the supra-marginalia also agree with BRÜNNICH NIELSEN'S description of R. carinatus, as the ridge may be sharp or just visible, and there are quite gradual transitions. Nor was there any difference from the point of view of occurrence, such as suggested by BRÜNNICH NIELSEN, both extremities being found from the oldest to the youngest Danian. An examination of the only find where the plates occurred in situ (1943 plate 3, fig. 9 13) proved my suspicion to be well founded, and a more detailed description of the species is therefore justifiable. When viewed from the actinal side the infra-marginaua are squarely wedge-shaped, the proximal articular facet being long and the distal one quite short, whereas they are of equal height. The face towards the opposite infra-marginal plate consists of a single facet. The free surface is always evenly vaulted and ornamented like Metopaster, with a depressed border and a few spine pits. Viewed from the abactinal side the supra-marginalia are pentagonal. The proximal articular facet is nearly as high as the entire plate, rather narrow and curved, with the concavity towards the body cavity of the animal. The distal articular face is quite small and low; it is adjacent to a somewhat larger inner facet joining the corresponding one on the supra-marginal plate facing it. Then, on the upper part of the inner surface, there are some small facets adjacent to the dorsal plates. The underside of the plate shows a single large facet. In some cases an additional smaller facet has been observed. In BRÜNNICH NIELSEN'S description of R. carinatus the underside is composed of two oblong facets. However, the existence of two facets is not confined to carinated plates, but may equally well be found in non-carinated plates. Between the large downward

6 422 H. WiENBERQ RASMUSSEN: Observations on the Asteroid Fauna facet and the small facets facing the dorsal plates, there is an uneven, concave surface adjoining the body. The free surface has a dorsal and a lateral part, in some cases passing gradually into each other, in other cases with a more or less sharp distinction. The ornamentation is of the Metopaster type. Spine pits are particularly frequent on the outward surface and the ridge, but might also be more evenly distributed. The specimen used by BRtrNNiCH NIELSEN as a holotype of i2. carinatus (1943, plate 4, fig. 34) has thus evenly distributed spine pits and no carina. Horizon and localities. Most Danian localities. Ravniasier granulatus n. sp. Figure 9.. From the coral limestone at Fakse we have a fairly large number of plates which must be referred to the genus Ravniaster. They are all strongly vaulted and granulated, as a rule also with spine pits in between them. There are both faintly unsymmetrical median marginaha, as weu as pronouncedly oblique distal marginalia. The proportions length / width / height are in the median marginalia measured at 3.7 / 3.4 / 2.7 mm and in the distal ones at 2.8 / 2.9 / 2.3 mm. On the inner side the distal marginalia partly show small facets adjoining the dorsal covering plates, partly a large oblique facet, where the plates of the two sides of the arm unite. The median plates only have the small facets corresponding with the covering plates. Like the median plates the distal ones have only a single downward facet, and there has thus been an equal number of supraand infra-marginalia. In a number of the other localities granulated marginalia have been observed which possibly belong to this species. Horizons and locality. Younger Danian. Zone with Tylocidaris Briinnichi. Fakse. Older Danian. Zone with Tylocidaris Abildgaardi. The boring at Fakse brewery. Chomataster Briinnichi n. sp. Figures 10 and Chomataster acutes SPENCER. BRÜNNICII NIELSEN, p. 59. Under the name of Chomataster acutes SPENCER, BKÜNNICH NIEL SEN mentions various plates. Among these are some plates from the older Danian. However, he says they deviate from this species by

7 Medd. fra Dansk Geol. Forening. København. Bd. 10 [1944]. 423 their ornamentation. These plates are up to 10 mm high and up to hak as long. The edges are parallel. The free surface is covered by closely set, rather small spine pits. On the edge between the lateral and dorsal face there is a large facet for a big spine. These plates mostly resemble Pycinaster Rosenkrantzii, from the uppermost Danian. They can, however, be distinguished by the parallel sides, the internal outline when seen in profile and by the ornamentation, which is not so coarse. In the older Danian the boring at the Fakse brewery has brought to light not only plates of this species, but also spines up to 4.5 mm long and 2.2 mm wide, which must be supposed to have corresponded with the large spine pits of these plates. Horizons and localities. Older Danian. Zones with Tylocidaris Ödumi and T. Ahildgaardi. Stevns, Kagstrup, Korporalskroen and the boring at Fakse brewery. Pycinaster cornutus n. sp. Figures 12, 13 and 14. In the very youngest Danian plates have been found which belong to a Pycinaster, very constant in appearance and distinctly different from P. Rosenkrantzii. Median supra-marginalia tall, wedge-shaped with a large dorsal swelling of the shape of a cylinder or a truncated cone, terminating in a very large dorsally placed spine facet. Length / width / height 5.7 / 4.5 / 9.2 mm. Most specimens are greatly worn, but in a few well-preserved ones the whole of the free surface is seen to have been covered by closely placed, quite small round spine pits. From Svanemøllen, where the species is particularly numerous, and also from a few other localities there are further a few broad coneshaped spines, up to 9 mm long and 3.5 mm broad, which undoubtedly corresponded with the dorsal facets of this species. Horizon and localities. Youngest Danian. Zone with Tylocidaris vexillifera. Copenhagen (Svanemøllen, Teglholm, Enghave Brygge, Knippelsbro) and Trælløse. Lophidiaster punctatus Figure 15. BR. NIELSEN Lophidiaster punctatus BRÜNNICH NIELSEN, p._67. By far the greater part of the specimens of Lophidiaster occurring in the Danian belong to this species. The variation is rather small.

8 424 H. WiENBERo RASMUSSEN: Observations on the Asteroid Fauna A few specimens, however, seem to have been smooth, but this may possibly be due to weathering or re-crystallization. In the upper Danian limesand at Limhamn in Scania A. ROSBNKEANTZ collected a number of plates originating from a single individual of this species. The plates were found pell-mell, agglutinated to the valve of a Chaiwinothyris lens. As the diagnosis of the species is based on isolated plates, it may be of interest to point out that the marginal plates were all of the Lophidiaster type, the distal ones being somewhat smaller and relatively longer than the others. Polygonal dorsal plates have been observed and likewise a terminal plate, fig. 15, semi-cyhndrical in shape, with a furrow on the inner side and an obhquely cut-off tip. Horizon and locality. Youngest Danian. Zone with. Tylocidaris vexillifera. Limhamn. Lophidiaster postornatus n. sp. Figure 16. In the very youngest Danian a number of marginal plates have been found, which in ornamentation and partly also in shape greatly resemble Lophidiaster ornatus SPENCER. They deviate by the somewhat lower ridge having almost the same height everywhere and not forming a lateral wing. Supra-marginalia : the proportions length / width / height are measured at 1.7 / 4.0 / 2.8 mm. The free surface consists of a lateral and an abactinal part, which unite in an arch. The ornamentation consists of large, rather deep spine pits. Infra-marginalia are of the same dimensions or a little lower. The free surface has an even and straight course from the actinal to the lateral border. The height of the ridge is.about 0. 5 mm. The ornamentation consists of a rather pronounced granulation. The species occurs in particularly great number at Svanemøllen, originating from the Danian limesand, a shallow water deposit. Thus this species agrees with L. ornatus, which in widely separated stratigraphical levels occurs in the Cretaceous coast deposits of England and Scania. Horizon and localities. Youngest Danian. Zone with Tylocidaris vexillifera. Copenhagen (Svanemøllen, Knippelsbro and Enghave Brygge) Saltholm, TræUøse, Mønsted and Bredstrup cuff.

9 Medd. fra Dansk Geol. Forening. København. Bd. 10 [1944]. 425 LITERATURE. MERCIER, JEAN: Les Stellendes Mésozoiques du Bassin de Paris (Bourdure Occidentale). Mém. de la Soc. Linnéenne de Normandie. Nouv. Sér. Géologie. Vol. 1, fasc NIELSEN, K. BRÜNNICH: The Asteroids of the Senonian and Danian Deposits of Denmark. Det Kongelige Danske Videnskabernes Selskab. Biol. Skrifter Bind II, Nr RosENKRANTz, ALFRED : Bemærkninger om det østsjællandske Daniens Stratigrafi og Tektonik. Meddelelser fra Dansk Geologisk Forening, Bind 9 Hefte SLADEN, W. PERCY and SPENCER, W. K. : A Monograph on the British Fossil Echinodermata from the Cretaceous Formations. Vol. 2. The Asteroidea and Ophiuroidea. Palæontogr. Soc SPENCER, K. \V.: The Evolution of the Cretaceous Asteroidea. Phil. Transactions of the Royal Soc. of London RESUMÉ Iagttagelser over Daniets Asteroidfauna. I den varietet af faksekalken, som udmærker sig ved forsteningernes overordentlig smukke bevaringstilstand, er fundet en par- randplader af søstjerner, fig. 1, som vidner om andre dyrs angreb, idet de har tydelige mærker efter bid. Sammesteds er ligeledes fundet en plade, fig. 2, hvis afvigende udseende maa være fremkommet ved regeneration. Dens ene ende er blevet skraat afskaaret, og i stedet for en ledflade er udviklet en fri ornamenteret overflade.. Et omstridt fænomen, som bestaar i en opspaltning af den terminale randplade hos slægten Metopaster diskuteres. Denne plade er større end de øvrige og svarer til flere nedre randplader. Den tænkes fremkommet ved en sammensmeltning af flere pladeanlæg. Der tages afstand fra den form for opspaltning i de primære bestanddele, som ifølge SPENCER har ført til de»radiate«varieteter af Metopaster arterne, idet disse varieteter i overensstemmelse med^bnijnnich NIELSEN henføres til slægten Recurvaster. Derimod anerkendes den type, som kendes fra SPENCER og SLADEN 1908 tavle 11 fig. 2, tavle 12 fig. 1 og textfiguren side 98, og der omtales en terminal randplade fra Svanemøllen, fig. 6, som maa have stødt op til to ved en saadan deling fremkomne plader paa armens modstaaende side, idet den viser to store facetter vendende mod armens midtlinie. Fra vort Danien beskrives fem nye søstjerner. Metopaster dividuus n. sp., fig. 3^5, karakteriseres ved at have en stor, femkantet, subterminal- og en ganske lille terminal øvre randplade. Dette forhold tænkes fremkommet ved spaltning af den terminale ovre randplade hos en Metopaster af den sædvanlige type.

10 426 H. WIENBERG RASMUSSEN: Observations on the Asteroid Fauna Horisont og lokaliteter. Yngre Danien. Zonen med Tylocidaris vexillifera. Svanemøllen, Herfølge, Trælløse. Ravniaster granulatus n. sp., fig. 9, har kraftigt granulerede plader. Den er især almindelig i Fakse, men ogsaa paa en række andre lokaliteter er iagttaget plader, som muligvis hører til denne art. Horisont og lokaliteter. Ældre Danien. Zonen med Tylocidaris Abildgaardi. Boringen ved Fakse bryggeri. Yngre Danien. Zonen med Tylocidaris Bmnnichi. Fakse Kalkbrud. Chomataster Brünnichi n. sp., fig , omfatter plader fra det ældre Danien, som af BRUNNICH NIELSEN provisorisk blev henført til Chomataster acules SPENCER. Pladerne er indtil 1 cm høje og halvt saa lange. Siderne er parallele. Den frie overflade er dækket af tætstillede, fine torngruber og har en facet for en stor torn. Pycinaster cornutus n. sp., fig , har haft ejendommelige, kileformede plader. Hver plade har paa den brede, opadvendende side baaret en meget kraftig torn. Horisont og lokaliteter. Zonen med Tylocidaris vexillifera. København (Svanemøllen, Teglholm, Enghave Brygge, Knippelsbro) og Trælløse. Lophidiaster postornatus n. sp., fig. 16, har haft korte randplader med en kraftig kam. Kammen har omtrent samme højde overalt, og har paa de øvre randplader haft torngruber, paa de nederste en kraftig granulering. Horisont og lokaliteter. Yngre Danien. Zonen med Tylocidaris vexillifera. København (Svanemøllen, Knippelsbro, Enghave Brygge) Saltholm, Trælløse, Monsted og Bredstrup Klint. Af de tidligere fra Danienet kendte arter forenes Ravniaster carinatus med R. pianus. Et fund af sammenhørende plader af Lophidiaster punctatus fra Limhamn i Skaane omtales. Metopaster dividuus, Pycinaster cornutus og Lophidiaster postornatus er sammen med Pycinaster danicus BR. N. og Pycinaster Rosenkrantzii BR. N. elementer af den specielle fauna, som findes i vort yngste Danien, og er iagttaget dels i kalksandskalken dels i det paleocæne bundkonglomerat, som i væsentlig grad bestaar af omlejrede forsteninger fra det yngste Danien. Færdig fra Trykkeriet 15. Januar 1945.

11 PLATE IX

12 Explanation of the plate. The figured specimens are preserved in the Mineralogicai and Geological Museum of the University of Copenhagen. Fig. 1. Star-shaped bite mark on a marginal plate of an asteroid, c. 6/1. Fakse. 2. Regenerated plate of a Metopaster. 4/1. Fakse. 3. Metopaster dioiduus n. sp. Reconstruction of an arm. 3/1. Svanemøllen, a. Abactinal view. b. Lateral view. 4. Same. Profile of supero- and infero-marginal plates. 3/1. 5. Same. Terminal articular face of subterminal supero-marginal plate. 3/1. 6. Combination showing the hypothetical origin of Metopaster dividuus. 3/1. Svanemøllen. 7. Ravniaster planus BR. N. Supero-marginal plate. 3/1. Fakse. 8. Same. Infero-marginal plate. 3/1. Fakse. 9. Ravniaster granulatus n. sp. Reconstruction of an arm. 3/1. Faxe. 10. Chomataster Brünnichi n. sp. Profile of marginal plate. 3/1. The boring at Fakse brewery. 11. Same. Dorsal spine, c. 3/1. The boring at Fakse brewery. 12. Pycinaster cornutus n. sp. c. 3/1. Svanemollen. a. Outer side. b. Profile. 13. Same. Another specimen, c. 3/1. Svanemøllen. 14. Same'. Dorsal spine, c. 3/1. Svanemøllen. 15. Lophidiaster pundatus BR. N. Terminal marginalia, c. 6/1. Limhamn, Scania. 16. Lophidiaster postornatas n. sp. c. 3/1. Svanemøllen, a. Supero-marginal plate, abactinal view. b. Infero-marginal plate, actinal view. c. Profile of supero- and infero-marginalia.

13 Medd. fra Dansk Geol. Forening Bd. 10. Tvl. IX. 3b. Ém I 8. II. laa. 12b. I <3-g-(!) IA-. 15 Pig. 1. Chr. HaUder phot. Pigs Wienberg Easmussen del.