New Echinodermata (Ophiocistoidea) found on the North-East of Russian Plate (Europe part of Russia)

 Grigory Winter

I. The object of research

The object of research is oral side of Ophiocistoidea the maximum diameter of which is 105 MM, with completely undamaged Aristotle lantern and other structures. This windfall has great science importance as the number of found fossilized Ophiocistia is very few due to small number of representatives of this class in general. The class of Ophiocistia is a typical transition link which is vaguely entered in the list of geological history due to quick morphological changes. They combined the features of ancient regular sea-urchins, starfishes and ophiuroids. The distinctive features of Ophiocistia is that this class is the link between the organisms from sedentary to free style of life. The nearest ancestor of Ophiocistia is probably Edrioasteroidea. After the death of  the organism the shell usually comes apart into calcium plates. The specimens found before this Ophiocistoidea had lower sizes and were not in such undamaged state comparing with the one found 600 km to the North from Moscow on the North-East of Russian Plate (Europe part of Russia).

II. Time and place of windfall

On the 8th of August of 1996 on the bank of Jagorba river (Cherepovets), which is forming together with Sheksna river the largest artificial storage in the world, was found quartzite copy of large Echinodermata. The windfall was made due to the lowest level of the water in the river of all the seasons of the last century. Thanks to it  a lot of stones and minerals laying at the bottom were seen on the surface. The place of windfall is practically in the center of metallurgist industrial city; which is 100 meters to the South from the Severni bridge  (The Northern Bridge) which connects two parts of city Cherepovets.

III. The history of investigation of the windfall

I found this Echinodermata being a teacher of natural History of Cherepovets State University. At that time I was  a specialist in Paleozoic paleontology but  not a good specialist on the field of Echinodermata. Great help in taxonomy identification of windfall was given by Doctor of Biology, specialist of invertebrates Mrs Tatijana Ermoshenkova. It was her who identified this Echinodermata as representative of Class Ophiocistoidea. For 2 years the  head of University laboratory of Zoology Mr. Roman Fedorov and I have been studying the morphological peculiarities of this windfall.

In the spring of 1998 the windfall was named Augustina winteri and it was included into the State list of new found invertebrates of Russia. The article about the peculiarities of Augustina winteri was published the same year in Cherepovets (Annual collection of researches of young scientists). The next 3 years the structural reconstruction and some other technically difficult investigations took place in the laboratories of Cherepovets State University under the  leadership of Doctor of technical science Mr.Fedorchuk.. The  main result of these investigations was the age determination of Augustina winteri – it lived 320 –330 millions of years ago. Thus we can see that the windfall belongs to middle Carbon period. It is extremely interesting peculiarity of this windfall as all before described in literature Ophiocistia lived not later than Devon. It was also confirmed by founding of Brachiopod Brachythyrina sp. in the same quartzite  copy with Ophiocistia. Two clam-shells of Brachythyrina sp. were seen in full and the fragments of one more Brachythyrina sp. were found  near the  Aristotle lantern of Augustina winteri which tells us about the fact that most probably this Echinodermata was a  predator and made short work of her victims like nowadays large tropic starfishes. Thanks to undamaged state and  large size of the windfall  we managed to reconstitute  the details of morphological construction of oral side of Augustina winteri, in spite of the fact that 1/3 of the fossil  is destroyed by erosion.

IV. Biofacies analyze: The way of life and peculiarities of burial.

Found Ophiocistia was enclosed into the quartzite mould of 130 x 225 MM  size. Biofacies analyses or the peculiarities of  disposition of  Augustina winteri  in the mould and the characteristics of the mould let us make some findings both of  possible ways of life of fossil Echinodermata and undamaged state of the windfall.

Most probably it is possible to state that Augustina winteri lived on the  shallow shelf lower the underwater built-up terrace where the streams grow weak making sand "saucer" among firm or clay soil. Investigated  Ophiocistia lived in such a "saucer" the form of which  was saved by the quartrite mould appeared by metamorphization (change) of quartz sand grains into rock. Like nowadays living representatives of sea-urchins Augustina winteri lived into the upper layer of the soil getting out of it only in case of changing its usual living conditions. With the current of water Ophiocistia received plankton through the special passage the track of which is seen in the mould. For catching plankton Ophiocistia used a pair of  highly developed ambulacral tubes having external skeleton. To our regret they are  seen only in fragments in the fossil condition. It was finding larger prey which shared econiche with  Ophiocistia by slowly moving in the soil and breaking hard shells by teeth of  Aristotle lantern.  It is easy to imagine the strength of  jaws knowing that the material covering each tooth (it is saved in the fossil condition turned into opal) has the thickness more than 1 MM. Besides that there were found wreckage of brachiopod Brachythyrina sp. near the mouth of Ophiocistia proving our conclusions.

Making deduction out of above mentioned we concluded that Augustina winteri was buried in living condition due to which fact there is  undamaged state of her fossilized remains. If Ophiocistia died before burial the lime plates composing it would be seen separately,  not in the form of  the whole shell as they had joining of muscular or other  tissue. Most probably sand "saucer" in which  Augustina winteri lived was covered by landslide of muscular tissue and Echinodermata died not being able to get out. Thanks to this sad event we have an excellent specimen for studying.

Picture 1: Expected appearance of Augustina  winteri and associate fauna (corallite Chaetetes and brachiopod Brachythyrina)

V. Morphological structure and peculiarities of oral side of Augustina winteri

Thanks to undamaged state fossil Ophiociastia remained the main part of it's morphological structure. The main peculiarity of  Augustina winteri is a pronounced radial-beam symmetry L88P.  This quality is an important taxonomic  feature as the most part of Pelmatozoa Echinodermata have the  radial-beam symmetry L55P. This quality of fossil Ophiocistia was taken from the following details of its structure:

  • Mouth  of Augustina winteri consists of Aristotle lantern which looks like a pyramid out of eight dental plates. The length of each dental plate is 12 –14 MM.
  • There is perignathic girdle around the mouth. On the perignathic girdle there are pore-pairs for tube-feet near the bottom of the dental plates. The "foot- parts" of the pore-pairs for tube-feet are seen behind the perignathic girdle till the end of the oral side of Ophiocistia. They divide this side into 8 ambulacral zones and 8 interambulacral zones. This fact proves our presupposition of radial-beam symmetry L88P of Augustina winteri.     
  • Besides the ends of oral side represent not a smooth round or oral but  shaped fans in the form of 4 smooth fans. These cuts couldn't be possible in case of other symmetry.

The other peculiarities of the given organism are:

  • Perignathic girdle consists of chess order situated calcium plates having considerable angle of inclination regarding horizontal  level. The angle of inclination of these plates is so large as they look like a number of  inclined hollows submerged into the surface of oral side for  2- 3 MM.
  • The pore-pairs for tube-feet are situated between the inclined hollows of perignathic girdle. These pore-pairs are also seen on the ambulacral zones looking like  the "foot-tracks" situated with the interval of 1 MM. The diameter of them is also 1 MM.
  • The ambulacral zones have special anatomic peculiarity – they are not situated in one level with interambulacral zones but graphically overhanged above the last. These overhangs can be  up to 5 MM. To our regret  this peculiarity of ambulacral zones was the reason of their damage during the mechanical erosion of fossil Ophiocistia. However the situation of ambulacral zones is seen by the pore-pairs for tube-feet as they are heavily extended into the oral disk. The difference in the construction of Ophiocistia Augustina winteri comparing with sea-urchins is in the way the ambulacral zones look like – in the case of Augustina winteri we can see ambulacral zone like massive calcium bars while sea-urchins have the ambulacral zones in the form of 2 rows of plates.

Interambulacral zones are much wider comparing with ambulacral zones. Interabulacral zones consist of 3 rows of large (up to 5 MM) calcium plates deposited by it's ends on each others like tile. In each of these plates there are seen a lot of small holes one of which is the largest and is situated in the center. Probably these holes  served for maintenance of osmosis pressure of water in the organism and appeared during the process of growing of calcium plates. Some of the scientists thinks that these holes are the sex pores but this point of view is not current opinion.

One of the interesting morphological details of Augustina winteri is the remaining of the coverlet or a breastplate protecting the structures of oral excluding Aristotle lantern. This coverlet was reduced during Augustina winteri life. Probably,  like class Ophiuroidea Augustina winteri gradually lost its coverlet during some period of time due to its hard abrasion as it crawled on the bottom. The degree of abrasion of  coverlet indicates the age of organism (like in the case of class Ophiuroidea). The less size has the remaining part of the coverlet the older is the organism. Biofacies analyses opened 2 fragments of such coverlet.  The coverlet consists of a large number of little squared scales situated in the chess order. These scales have no holes as they consist not of calcium being the blistering on the skin like in many representatives of Ophiuroidea class.

On the right side of the photo you can see the fragments of  blistering  quite distinctly. The holes for foot tubes are twice smaller on the coverlet comparing with the ambulacral zone. On this coverlet the pore-pairs are also seen but they are not between the scales transfixing them through.

Thanks to the fact that the quartzite mould was broken during erosion  the lateral side is seen. Due to it the buttresses are observable. In Ophiocistia Augustina winteri the upper and lower surface of the test are connected by an often extensive series of buttresses and pillars. These are purely structural and reinforce the test. These buttresses are shown on the picture with reconstruction of lateral side.

The main distinction of class Ophiocistoidea as you know from the other classes of free living Echinodermata is that they have one or several pairs of hypertrophied tube- feet. The other found before Ophiocistia similar  pairs of tube-feet had the length up to ½ of diameter of oral disk of the organism.  They also had surface skeletonization by calcium plates. The similar construction had Ophiocistia Eucladia jonstoni reconstructed by Russian scientist Fedotov. Hepertrophied tube-feet helped in spatial motion and in nutrition. Unfortunately erosion rubbed sore hypertrophied tube- feet of  Augustina winteri. The only remaining part (3 calcium plates) forms a straight line with the oral disk of Ophiocistia. It gives us grounds to suggest that Augustina winteri also like other Ophiocistia had this interesting peculiarity. Due to this reason the hypertrophied tube-feet of Augustina winteri are shown in the picture with reconstruction admittedly (it is the only anatomic detail which is shown in the picture conceivably).         

XII. The main deductions

After studying all these morphological details of construction of the found Ophiocistia me can make the following deductions:

  • all described before reports that Augustina winteri has significant distinctions comparing with the other described in the literature Ophiocinsia Eucladia jonstoni, Sollasina, Volchovia.
  • First of all the symmetry of Augustina winteri is L88P which confirms the sibling connection of class Ophiocistoidea and class  Ophiuroidea. One more detail confirms this connection – coverlet of living now Ophiuroideas was the same as Augustina winteri had.
  • Many details of construction of oral side of Augustina winteri agree with the regular old sea-urchins like in the case of Archaeocidaris wortheni (Cidaroidea) – the presence of perignathic girdle around Aristotle lantern; the construction of plates in interambulacral zone is also very much alike (the form of the plates and the sizes of them).
  • Extremely important point of investigation  was dating of Augustina winteri: it lived in the middle Carbon 320–330 million year ago (according to the results of radiocarbon measurements). The dating of Augustina winteri clashed with dating of Archaeocidaris wortheni (Cidaroidea) which is very interesting!
  • Before this windfall it was used to consider Ophiocistoidea as dead-end branch of  phylogenetic table. After the investigation of Augustina winteri we made diversification of this point of view and came to the conclusion that class Opiocistoidea is the transitional link between  Edrioasteroidea and all free living Echinodermata with the exception of holothurian.
  • It is necessary to underline that Augustina winteri lived 50 million years after the dating of other Ophiocistoideas.

Most probably the class of Ophiocistoidea died out as ¾ of all Echinodermata in the beginning of Perm due to the abrupt change of the climatic regime. We presuppose it due to the fact that Agustina winteri lived 50 million years after the dating of  other Ophiocistoideas. Besides it had some progressive for evolution of Echinodermata details of construction  can be seen now in the orders of Lepidocentroida and Camarodonta.

All above mentioned informs that the investigation of Ophiocistia is a prior task for the phylogenetic table of Echinodermata.