Сбор, диагностика и обработка палеонтологических материалов при проведении учебных геологических практик. Учебное пособие на модульной основе

4. The system of the organic world

same time, some sea lilies have adapted to life in the pelagial (plankton or pseudoplankton). Benthic echinoderms either move along the bottom, rarely burrow into soft soils, or lead a nonmotile lifestyle, most often attaching themselves to the bottom with the help of a stem. This determined the long-existing division of this type into stalked, or attached (Pelmatozoa), and free-living, or detached (Eleutherozoa). However, the geological history of echinoderms, which began a very long time ago, most likely in Vendian, revealed a much greater diversity, which necessitated the revision of the system as a whole.

Currently, the Echinodermata type is divided into four subtypes Homalozoa (Є-C), Crinozoa (Є-Q), Asterozoa (O-Q), Echinozoa (V?,Є-Q) (Bondarenko, Mikhailova, etc.). The possible echinodermsbelongtotheEchinozoasubtype,whilemoreprimitive Homalazoa are known only from the Cambrian. Apparently, due to the incompleteness of the geological chronicle, the initial page of the history of echinoderms has not been preserved (or has not yet been discovered), or the Vendian finds do not belong to the type of echinoderms.

Characteristic of SEA LILIES class. CLASSIS CRINOIDEA. (Greek krinoн – lily)

The sea lilies is the only one of the three classes of the Crinozoa subtype that still exists. Sea lilies are numerous and varied. Their skeleton consists of a calyx, stem and brachioles – arms.

The calyx has a different shape – from round, oval to hemispherical or conical. The calyx formed by two or three belts of plates is most simply arranged, each belt has five plates. Plates of the upper belt are called radial, and one or two lower belts are called main. Among the latter, there are: the main ones (basal) and the lower main ones (infrabasal).

The stem of sea lilies has a different length and consists of segments, the movable articulation of which provides the possibility of bending and some rotation. Stem segments, arm segments, and the calyx are most often buried separately, and therefore the skeleton of fossil sea lilies is studied both as a

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4. The system of the organic world

whole and discretely: both the calyces and the stem are studied independently (in parallel).

The stem segments of sea lilies are extremely variable in structure. First of all, the variety of segment shapes is striking: from stellate to rounded-pentagonal and round, as well as roundedquadrangular and oval, i.e. not having five-beam symmetry. The shape and size of the central axial canal, the sculpture of the articulation surface, the shape and size of the ligament field are very diverse and are the subject of special studies.

Sea lilies appeared in the Ordovician and reached great diversity in the seas of the Late Paleozoic. They led a motionless lifestyle, attaching to the bottom and rising above it with the help of a stem. In the Mesozoic, forms appeared that lost their stem and switched to a planktonic or pseudoplanktonic way of life. Sometimes the disappearance of a single stem was accompanied by the appearance of numerous (up to 100) segmented appendages – cirri. Cirri, like arms, contribute to the adaptation of lilies to living in the pelagic zone. Moments of motion are replaced by moments of rest, and then the cirri temporarily wrap around floating objects or bottom irregularities.

Among modern sea lilies, stemless forms dominate. They account for at least 85 % of the total number of modern species. At shallow depths, such lilies constitute a permanent component of the marine fauna. The stalked sea lilies in modern basins are of sharply subordinate importance and make up no more than 15% of the total number of modern species. They moved to great depths and the first specimens of stalked lilies were caught and described only in the second half of the 18th century, i. e. much later than stemless forms. It has now been established that stalked sea lilies live at depths up to 10,000 m. Their stem is no more than 1 m in length, whereas in their fossil ancestors it could reach 20 m, as a result of which fossil lilies are included in the group of the largest invertebrates along with modern internal shell cephalopods (giant squids) (Bogoyavlenskaya, 1990).

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Characteristics of Echinozoa subtype. Subphylum Echinozoa. ECHINOIDEA CLASS. CLASSIS ECHINOIDEA

(Greek echinos – hedgehog)

The Echinozoa subtype includes three classes of echinoderms, which have a hemispherical, spherical, barrel-shaped, fusiform or other body, often enclosed in a shell and not having beams compared to Asterozoa, and compared to Crinozoa – arms and stem. This subtype includes at least seven classes. It is most probable that the first Echinozoa appeared in the Vendian (Edrioasterroidea, V?, Є-C1) (Drushchits, Bondarenko, etc.). Echinoidea have existed from the Ordovician to the present, and fossil holothurians are somewhat problematic, although, apparently, they appeared no later than the Devonian.

ECHINOIDEA CLASS. CLASSIS ECHINOIDEA (Greek echinos – hedgehog)

Marine mobile echinoderms, whose soft body is enclosed in a shell. The structure of the shell and the main internal organs of sea urchins was described above.

Recall that the mouth opening of sea urchins was originally located in the center of the lower side, and the anal opening in the center of the upper side. The sea urchin shell is separated from the mouth and anus by small leathery areas. The mouth opening is surrounded by the oral field (periosteum), and the anus is surrounded by the anal field (periproct). Five-beam symmetry can be traced in the structure of the ambulacral, nervous, circulatory and reproductive systems. The carapace of sea urchins is subdivided into 5 ambulacral and 5 interambulacral fields, starting from the eye and genital plates, grouped into an apical shield. Ambulacral fields may consist of simple or complex plates. Simple plates are pierced by two pairs; complex plates arose due to the merger of simple ones and bear several pairs of pores. The interambulacral fields are formed by larger plates, on which there are tubercles for attaching spines. The tubercles are usually differentiated in size. A large tubercle rises in the center of the plate, and around it there is a ring of small tubercles.

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A largespine was articulated with a large tubercle, and its base was covered by a system of small spines attached to a series of small tubercles. In the fossil state, the spines are usually preserved separately from the shell.

Apical shields have a different structure. In Paleozoic sea urchins, 5 genital and 5 eye plates approach the anus; this type of apical shield is called monocyclic. In younger sea urchins, only the genital plates are grouped around the anus, and the eye plates form a second cycle; this type of apical shield is called dicyclic. In the course of evolution, in many sea urchins, the anus has shifted back from the center of the upper side of the shell (between two rows of plates of the posterior interambulacrum).

The classification of sea urchins is based on the following features: the position of the mouth and anus, the structure of the ambulacral and interambulacral fields, the type of apical shield, and the nature of symmetry. It is in sea urchins that a change in the type of symmetry and a transition from five-beams to two-sided symmetry can be traced. In parallel, there are two classifications: natural, representing the division of sea urchins into an order, and artificial, which resolves into the allocation of several groups without regard to phylogeny.

The artificial taxonomy of sea urchins is simple and easy to understand and use (Bondarenko et al.). Sea urchins appeared in the Ordovician and exist to this day. In accordance with this, ancient (O-P) and new (T-Q) sea urchins are distinguished. The first difference between the ancient sea urchins and the new ones is that the number of rows of plates in the interambulacral field is usually more than two, and in the ambulacral field at a minimum is one row, and at a maximum over 15. The second difference is that the ancient sea urchins had a flexible shell, in in some cases, and in others – from non-contiguous plates, articulated with the help of ligaments. The flexible shell after the death of the sea urchin fell apart into separate elements and only in exceptional cases could it be completely preserved. In modern seas, there are several deep-water forms with a flexible

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shell, but with an ordered two-row structure of fields. Ancient sea urchins, apparently, were predators.

New sea urchins are subdivided into regular (T-Q) and irregular (J-Q) (Mikhailova et al.) Regular sea urchins are characterized by the central position of the mouth and anus. Therefore, in regular sea urchins, the apical shield is cyclic. They have full five-beam symmetry, have long spines used for walking and protection, as well as a vertically located “Aristotle’s lantern”, with which they collect food, primarily algae. Regular sea urchins live mainly on rocky soils.

Irregular sea urchins have a displaced anus. This group is divided into jawed (the mouth remains in the center of the lower side, the “Aristotle’s lantern” has an inclined position or is absent) and jawless (the mouth moves forward, the jaw apparatus is absent). In jawed sea urchins, the five-beam symmetry is broken by the displaced position of the anus, and in jawless sea urchins, by the displaced position of the mouth opening and anus, as well as by the bilaterally symmetrical shape of the shell – oval or heart-shaped.

Sea urchins, as shown by observations of them in aquariums, are omnivorous. They devour both dead fish and other carrion, live daphnia, small starfish and snails, shells, their own conspecifics, as well as algae of all kinds, lettuce, even wood and groundnut oil.

On the other hand, echinoderms can starve for a long time. Some starfish, for example, did not eat anything for 18 months and remained alive (Akimushkin, 1992).

Rocks, even granite or basalt, are sometimes drilled by sea urchins, where the water is shallow and the surf is strong. Sometimes these caves are designed for only one resident – a sea urchin, sometimes they are whole cauldrons half a meter deep and a third of a meter in diameter, where several dozen sea urchins the size of an apple or a fist sit. This way of life saves sea urchins from drying out at low tide or other decline of water, and from predators, and from the blows of the surf.

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It is quite clear that for drilling such hard rocks as granite, sea urchins must have a very strong drilling apparatus. And indeed, their jaws and teeth are something amazing. The very appearance of the chewing apparatus, called by former scientists the “Aristotle’s lantern”, clearly proves its purpose. This is a real drill, like those used in metal workshops.

But with this drill, the sea urchin only gnaws at granite. Work is progressing quickly, and soon the cave drilled in the stone is ready. Then the sea urchin proceeds to its more thorough finishing. It twirls, twirls inside it, its spines scraping against rough-hewn walls, scraping them and polishing them to a shine.

Echinoderms are found only in the seas and oceans at all latitudes and at all depths – from the littoral to the abyssal (10 thousand meters from the surface).

All echinoderms are very sensitive to the slightest desalination of water. They are absent in the Caspian Sea, in the Baltic Sea they are represented by only three species, and in the Black Sea by only eight species, but in the Barents, Kara, Chukchi and Okhotsk Seas they make up the bulk of bottom animals.

Project specification for the material

Analyzing the geological structure of the territories adjacent to the training grounds (based on the study of bibliographic and cartographic material), and relying on reference collections of fossil organisms, identify the guiding fauna within them and determine with its help the age of sediments and the conditions of their accumulation (paleogeographic reconstructions).

Use the data when performing laboratory work on structural and historical geology.

Questions for self-control

1.What is the difference between echinoderms and other types of animals?

2.Why is there a special focus on sea urchins and sea lilies?

3.What is the ambulacral system?

4.What elements does the ambulacral system consist of and what is its purpose?

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4. The system of the organic world

5.What is the morphology of representatives of the ECHINOIDEA class?

6.How many subtypes is the type currently subdivided into?

7.Are Echinoderms stenohaline or euryhaline organisms?

8.What are the dimensions of echinoderms?

9.Which animals of the echinoderms type have a change in symmetry? What is the reason for this?

10.What is the significance of sea urchins for geology?

11.Are there sea urchins and sea lilies in the Sea of Azov?

Why?

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5. TASKS TO CONTROL RESIDUAL KNOWLEDGE ON THE HISTORY OF EARTH DEVELOPMENT

Category A

1.The science of the sequence of geological events of the past and present:

ecology;

geochronology;

lithology;

stratigraphy.

2.Layers distinguished by their characteristic material composition, structure, color, abundance of certain remains or inclusions:

basic;

determining;

marking;

bearing.

3.Name the method that is used exclusively in the study of quaternary sediments:

spore-and-pollen;

lithological and mineralogical; radiocarbon;

paleomagnetic.

4.A set of methods for determining the absolute age of rocks according to the decay data of naturally radioactive elements:

radiogenic;

radioactive;

radiometric;

radiological.

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5.Tasks to control residual knowledge on the history of Earth development

5.Geological processes periodically repeated in the history of the Earth:

dinosaur extinction;

global transgressions and regressions; appearance of mammals; cratonization.

6.Geophysical methods of dissection and correlation of sediments are based on the comparison of rocks by:

lithological properties; physical properties; paleontological characteristics; hydrogeological properties.

7.Evaporites include:

limestone;

granite; potassium salts; gravelite.

8.The process of clumping and compaction of stardust: concretion;

coagulation;

accretion;

paragenesis.

9.The process of stretching the continental crust: subduction;

spreading;

rifting;

orogeny.

10.The oldest formations testifying to the processes of spreading and the existence of oceanic crust:

kimberlites;

ophiolites;

olistostromes;

traps.

11.The global process that gave the planet a permafrost

zone:

transgression;

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5. Tasks to control residual knowledge on the history of Earth development

regression;

accretion;

glaciation.

12.Types of precipitation dominating in shallow-lagoon basins in hot climates:

eukaryotes;

halogens;

evaporites;

bauxite.

13.The process of comparing rock layers to identify the same age of strata:

correlation;

stratification;

identification;

comparison.

14.Ancient organisms that lived for a short period of time, were widely distributed over the area with individual, specific features:

defining fauna; main fauna; guiding fauna; basic fauna.

15.The process of dividing the megacontinent into separate structures:

reconstruction; splitting up; extension; destruction.

16.What does the prefix paleo- (paleotectonics) mean? ancient;

early;

previous;

former.

17.Traces (products) of the vital activity of blue-green algae: stromatolites;

ophiolites;

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