Iraida Pavlovna Morozova (1919–2007)

Paleontological Journal -     

Morphological similarity between echinoid taxa as a result of convergent and parallel evolution

Convergence is observed in groups, which are phylogenetically remote. A flat test is typical for some representatives of the order Cassiduloida, such as Jurassic and Early Cretaceous species of the genera Pygurus and Clypeus, and also many Cenozoic «sand dollars,» i.e., echinoids of the order Clypeasteroida. Both usually inhabit coarse sandy grounds of shallow areas. The superorder Spatangacea includes the so-called Echinocorys life form, which is characterized by an oval test with superficial nonpetaloid or subpetaloid ambulacra, marginal or inframarginal periproct, and absence of fascioles. These are the following genera: Early Cretaceous Corthya (family Collyritidae), Late CretaceousLate Paleocene Echinocorys (family Holas-teridae), Paleocene Isaster, Recent Isopatagus (family Isasteridae), Recent Scrippsechinus (family Palaeotro-pidae), and Recent Urechinus (family Urechinidae). In contrast to the majority of spatangaceans with the burrowing mode of life, these genera dwell on the substrate surface. In the Cenozoic, the monobasal apical system appears in some genera of the order Spatangoida, most genera of the order Cassiduloida, all groups of the orders Clypeasteroida and Oligopygoida, and in the genus Echinoneus (order Holectypoida). The paral-lelism is revealed in groups connected by remote relationships. At the end of the Middle Jurassic (Callovian) and, especially, Late Jurassic, the so-called disasterid echinoids (superorder Spatangacea) show a distinct trend to the loss of contact between ocular plates I and V and apices of the posterior ambulacra with the periproct, which are shifted to the anterior part of the apical system (genera Collyrites, Collyropsis, Cyclolam-pas). At the same time, the peristome of some genera was displaced to the anterior margin of the test, which became bilaterally symmetrical in outline. However, in the Jurassic, all spatangaceans remained disasterid echinoids, i.e., had a disjunct apical system, which can be interpreted as a somewhat “abnormal” state. This trend disappeared only at the beginning of the Cretaceous, when “normal” forms with a joint apical system appeared, that is, the families Holasteridae (genera Eoholaster and Holaster, order Holasteroida) and Toxas-teridae (genus Toxaster, order Spatangoida). Interesting examples of synchronous parallelism are provided by the appearance of meridosternous (diasternal) plastron in two collyritid genera (Tetraromania and Corthya) in the Barremian, whereas in the holasterid genus Holaster, this type of plastron apparently appeared in the Valanginian (heterochronous parallelism). The ethmolitic type of the apical system appeared at the end of the Cretaceous and Paleocene at least in five families: Schizasteridae, Paleopneustidae, Brissidae, Spatangidae, and Loveniidae.     

Heterochrony and heterotopy in the phylogeny of sea urchins

The role of heterochrony is evident in ontogeny and phylogeny of irregular (exocyclic) sea urchins. After metamorphosis, a juvenile passes the stage of regular (endocyclic) sea urchin, in which the periproct is surrounded by plates of the apical system. A shift of the periproct in the area of the fifth interambulacrum occurs in extant taxa at early stages of postlarval development and is accompanied by the reduction of genital plate 5. In some ancient (Jurassic) adult irregular sea urchins, the endocyclic state of the apical system is retained for a long time and the derivative of the fifth genital plate is sometimes observed even in Early Cretaceous species. Considerable transformations in the structure of the lower test surface in members of the order Spatangoida are manifested in changes in the relative positions of plastron plates and ambulacral areas I and V, separation of sternal plates from the labrum, etc. The mechanism of these changes is connected with translocation or “sliding” of sutures of particular plates as a result of nonuniform growth and partial resorption. The study of evolutionary lineages of Cretaceous and Cenozoic sea urchins has shown that the evolution was connected with the directional changes in some morphological characters at late ontogenetic stages. The process was accompanied by either extension, peramorphosis (lineages of the genera Micraster, Infulaster–Hagenowia in the European Province), or the loss of these stages, paedomorphosis (Hemiaster (Bolbaster) lineage, Late Eocene–Middle Miocene of Australia). The phenomena of heterochrony and heterotopy in the development of peripetal, marginal, and lateroanal fascioles in the Late Cretaceous and Paleocene families Hemiasteridae, Schizasteridae, and Paleopneustidae are described. The heterotopy is also illustrated by the example of the development of additional genital pores on ocular plates II and IV of the Middle Jurassic species Pygomalus analis (Disasteroida); its apical system has five pores instead of four. In the Late Cretaceous species Guettaria roccardi (Holasteroida), ocular plates II and IV have two pores each; in the apical system, there are eight genital pores instead of four. In some members of the order Holectypoida, the place of lost genital plate 5 is occupied by a new plate sometimes pierced by a pore, but judging from crystallographic data, it is not homologous to other genital plates. The order Clypeasteroida is characterized by the development of very small pores in both ambulacral and interambulacral fields; they provide passage for numerous accessory tube feet.     

Morphology,systematic position,and distribution of Bothriocidaroid echinoids

This is a brief review of conceptions of morphology, distribution and systematic position of the most ancient echinoid group—order Bothriocidaroida. It comprises 3 genera: Bothriocidaris, Neobothriocidaris, and Unibothriocidaris. More than 20 species of these genera are distributed from Upper Ordovician (Caradocian) to Lower Silurian (Llandoveri) in North Western Europe and North America. The question of whether this group belongs to the class Echinoidea or not has been the subject to discussions several times, particularly based on cladistic methodology. In my opinion the peculiarities of bothriocidaroids are quite typical of archetype definition of this class, however, so-called unique modalities of its merons are actually prone to variation both inside the group and among other echinoid groups. For example, Bothriocidaris maquoketensis has a structure transitional from uniserial to biserial interambulacra, however uniserial interambulacra are found in Paleozoic family Cravenechinidae and in some Cretaceous holasteroids and Cenozoic clypeasteroids. Unfortunately, such an important feature as the apical system is found only in one genus Bothriocidaris.     

The role of echinoids in shaping environments

The role of echinoids in shaping the environment of marine and terrestrial biota is considered. The participation of echinoids in bioerosion, bioturbation of sediments, and their relationships with symbionts, parasites and predators, as well as the role of echinoid skeletons in rock formation, are discussed.     

Genomic carrier detection and prenatal diagnosis of haemophilia A in families at risk using the polymerase chain reaction (PCR).

The polymerase chain reaction (PCR) was applied in genomic analysis of families at risk for haemophilia A using the intragenic Bel I and Hind III polymorphism in introns 18 and 19, respectively, of factor VIII gene. For the latter the primers derived from exon 19 and 20 sequences allowed to amplify the whole intron 19 resulting in a 730 bp fragment. Hind III restriction of this fragment provides polymorphic fragments of 250 bp or 160 bp and 90 bp respectively. An also occurring 480 bp fragment can be used as internal control to circumvent misdiagnosis due to incomplete or failure of restriction. The Hind III polymorphism was successfully used in prenatal diagnosis of an affected male in the first trimenon of pregnancy. Fetal sexing was also performed by PCR technique using Y specific primers.