Korzoun L.P., Gerasimov K.B., Kalyakin M.V.
This paper is written in honour of the 80th birthday of F.Y. Dzerzhinsky, emeritus professor of the Lomonosov Moscow State University, professor of the Department of Vertebrate Zoology, and the principal investigator of the A.N. Severtsov Laboratory of Evolutionary Morphology of the Biological Faculty. We describe his march and trace the main ideas developed by this outstanding morphologist, a brilliant teacher and a wonderful person who brought up a pleiad of researchers at the Moscow University. The paper is supplemented by a list of the works by F.Y. Dzerzhinsky.
Ivlev Yu. F.
One of the means for body insulation in mammals during their transition from terrestrial to semi-aquatic and then aquatic life is based on the usage of fur in water as an effective “dry” insulator. Fur functional conditions are changed drastically and instantaneously when fur contacts with water. The physical mechanisms underlying fur waterproofing were analyzed and their relations to both fur structure and animal body size established. The results of the analysis allow us to define to what extent the fur structural features of a mammal in relation to its body size are capable of trapping an insulative air layer when the animal swims in water. Based on our analysis, both the body size of the ancestors of fur seals and the type of thermal insulation changing in the postnatal ontogeny of sea bears are hypothesized.
An electron microscopic study (SEM) of the fine structure of the primary remex in owls (Strigiformes) was conducted using 13 species: Nyctea scandiaca, Bubo bubo, Asio otus, Otus scops, O. sunia, Aegolius funereus, Athene noctua, Glaucidium passerinum, Surnia ulula, Strux aluco, S. uralensis, S. nebulosa, Tyto alba. Owls are shown to have a number of species-specific microstructural primary remex characteristics that are taxonomically important. First of all, these are the structural features of the pennaceous barb which differ markedly not only at the ordinal, but also at the species level: cross-section configuration, pith architectonics in cross- and longitudinal sections, cuticular barb structures. The work emphasizes that the identified elements are of taxonomic significance only when comparing the specific, strictly analogous sections of the barbs in different bird species. Based on the present study, along with the typical elements of feather architectonics characteristic of representatives of other bird orders, the owls show a number of peculiar fine structural features. Thus, as the result of an analysis of the fine structure of the owl remex’s pennaceous barb vanules, unique features of the distal barbules and the structure of the apical section of the barb with tightly adjacent and elongate proximal and distal barbules could be distinguished. These characteristics are revealed to cause a dense fleecy structure of the vane dorsal surface and the presence of a complex of peculiar “bunches” that form the cleft edge, i.e. the purely specific traits of the owl feather that are not found in representatives of any other bird order we have investigated.
Badikova A.A., Dzerzhinsky F. Ya., Kuznetsov A.N.
The parakeet (Aethia psittacula) jaw apparatus was studied in comparison with that of the crested auklet (A. cristatella). Mechanical and biological properties of the peculiar parakeet bill were analyzed. Due to the concavity of the oral slit, a balance of any object clamped in its bill is achieved at any position with disabling neither the rear nor the front portions of the dorsal adductor of the lower jaw, so that it can always develop the maximum force. Cutting larger food objects, such as polychaetes and jellyfish, by the bill, has become the parakeet’s jaw apparatus specialization unique among birds. Strengthening the jaw apparatus originally adapted to capturing small planktonic crustaceans could have occurred via the development of additional aponeuroses in the external adductor, its consolidation, as well as bill shortening and oral slit reshaping.
In this work, I describe the structure of the hyoid apparatus of the Old World suboscine birds which I dissected layer by layer. I made a comparative morphological analysis of their tongues using several species from each of the three families (Pittidae, Eurylaimidae and Philepittidae). All parts of the hyoid apparatus are well-developed in these avian groups, their tongues being very mobile. I also describe particular details characterizing each of these groups. The tongue of the pittas is the most common in structure, but the parts of its skeleton are of considerable length. An especially broad and thick tongue, particularly in carnivorous species, distinguishes the broadbills. The tongue of asities consists of two parts: a narrow rostral tube and a wide caudal platform. These differences are obviously closely related to the features of their feeding behavior and diet. The functioning of the hyoid apparatus of these birds will be discussed in Part 2.
Modern fossil evidence shows an extensive ecomorphological radiation of Mesozoic mammals. By the mid-Cretaceous, mammals evolved all main adaptations of modern small-sized Mammalia except for true powered flight. In addition, new palaeontological and embryological data on the morphogenesis of the auditory ossicles demonstrate parallel developments of the definitive mammal middle ear in the placentals, marsupials and monotremes, as well as independent origins of a number of early groups: Allotheria (Haramiyida and Multituberculata) within Mammaliamorpha (irrespective of the lineage including eucynodonts Brasilodontidae and the mammaliaform Apotheria, Prototheria and Acrotheria) and Prototheria (including Monotremata) within the Mammaliaformes (parallel to the Acrotheria lineage).
Based on 63 species from 20 genera, the specificity of the sciurid auditory capsule was analyzed. It is characterized by a special combination of primitive and advanced features stable within the group, such as: 1) a rounded and inflated bulla with internal septa and a primitive attachment of the tympanic annulus to the inner tympanic wall; 2) a transverse position of the bulla relative to the axis of the promontory, resulting in the presence of deep petrosal fossae in front of and above the promontory which are not covered by the tympanic bone; 3) a fully formed osseus facial canal and a developed bone tube of the stapedial artery; 4) the presence of a meato-cochlear bridge connecting the promontory to the posterior wall of the acoustic duct which, in a fully developed form, does not occur in any other Recent rodents; 5) pneumatization of the mastoid due to the epitympanic recess being expanded both anteriorly and posteriorly, with the formation of a “premeatal pocket” and a large epitimpano-mastoid chamber divided into parts. The sciurid auditory capsule can generally be considered as morphologically advanced. Its diversity within the family concerns functionally significant features and is manifested in the structure of the external acoustic meatus, the size of the eardrum, the length of the auditory ossicles’ processes, and, most importantly, the degree of pneumatization of the auditory capsule as a whole or its departments. This is associated with quantitative variations of characters and does not affect its structural plan, as a rule.
Due to F.Ya. Dzerzhinsky and his scientific school, the avian jaw apparatus has become a traditional and well-studied topic in Russian functional morphology. Based on decades of communication with Dzerzhinsky, the author attempts to critically review his scientific heritage in order to derive the most promising directions for further research. The analysis undertaken shows that the most significant gap in Dzerzhinsky’s methodology lay in underestimating the problem of muscular mass economy in the avian jaw apparatus, in spite of the severe limitations for weight burden in birds. A new model is suggested, which solves the problem of decreasing the excess mass of jaw muscles, based on the presumed difference in the kinematics of bill opening and food-object compression. In the bill opening, the major adductor muscles can keep almost constant lengths, thus acting as inextensible links in the closed kinematic chain of the kinetic skull. The absence of a necessity to change the length with mouth opening allows for these muscles to be short-fibered and hence light-weight, but strong. Only when a food-object is taken in the bill, the bird makes use of the muscular force by means of locking the quadrate-mandible articulation, which leads to a reformation of the kinematic chain when the food-object is being compressed. Further enhancements of the model are achieved by introducing non-parallel lines of action of the pterygoid muscle and jugal bar. With this feature, the avian jaw mechanism gains a profit of completely employing the available forces of the jaw adductor muscles, avoiding special adjustments to every food-object and to every specific case of its capturing. The major elements of the suggested model, which were discovered by Dzerzhinsky himself, gain new significance in the light of the concept of muscular mass economy. Therefore, a general conclusion is inferred on the adaptive significance of the avian cranial kinesis as a means to reduce the mass of the jaw adductor muscles saving their force. In addition to the new model of jaw mechanics, several other promising directions for the development of Dzerzhinsky’s research are suggested, based on an enriched methodological menu. A challenging topic employing CT-scans and numerical simulations is research of aponeurotic structures in the jaw muscles as a way to optimally pack the muscular fibers of required length in the 3D space available between the other head structures.
Zherebtsova O.V., Potapova E.G.
Based on literature and original data, several morpho-functional systems are compared in the extant species of Diatomyidae and Ctenodactylidae, both families being considered as sister taxa. The subcutaneous and ear musculature, auditory capsule, jaw apparatus and distal limbs are examined. These groups are shown to differ significantly both in the level and direction of the morpho-functional transformations of the above systems. Ctenodactylids are a much more specialized group than Laonastes. They have an auditory capsule, a jaw apparatus and the distal limb sections that reach the maximum level of morphological and functional specialization in the rodents, while in the case of Laonastes, they correspond approximately to the average level of their development. Both groups are characterized by different pathways of morphological transformations of all systems considered, even those of them (jaw apparatus and limbs) that are associated with adaptations to similar ecological conditions, i.e. life on stones and herbivory. In Lanastes, the structure of the above systems retains the archaic characteristics which are combined with features specific only to this group. In the gundi, the direction of morphological transformations is completely specific as regards some of the parameters, while in other respects it corresponds to the trends typical of the hystricognathous rodents, this having led to a large number of structural parallelisms. In the structure of each morphological system examined, synapomorphies that support the monophyly of Ctenohystrica are revealed. There is no single-valued morphological evidence for the close relationship between Ctenodactylidae and Laonastes relative to Hystricognathi, although in the structure of almost all of the systems examined there are common features distinguishing these taxa from other rodents, in particular from Hystricognathi. Characters reflecting the pattern of differentiation of the subcutaneous muscle and the features of mastoid pneumatization can be regarded as the most significant for assessing the phylogenetic relationships of Diatomyidae, Ctenodactylidae and Hystricognathi. However, for a more reliable judgment of the relationships based on morphological data, more extensive material is needed to cover the diversity of the structures considered in hystricognath rodents.
Among the ancient and modern marine reptiles, several structural types of the locomotor apparatus were or are present, providing different styles of swimming. Ichthyosaurs, mosasaurs, sea crocodiles and representatives of many other groups swam or swim using horizontal undulations of the body mainly with the help of a tail equipped with a vertical caudal fin. Sea turtles with a reduced tail and with a body completely immobilized by the carapace use only limbs transformed into fins when swimming. Sauropterygia possessed a substantially immobilized trunk and a horizontal caudal fin. They realized a unique type of subaquatic locomotion with the leading role of two pairs of powerful fins and vertical undulations of the tail, partial analogs of which are found in sea turtles, sirens, cetaceans and several semi-aquatic mammals.
Dzerzhinsky F. Ya.
Information comcerning a two-unit construction of the neurocrania of rhipidistian fishes and Latimeria coelacanth, as well as on the splanchnocranial components (their constructions differ in these fishes) is presented. The accessory cranial kinetics definitely associated with elevating the snout also differs in these fishes. Rhipidistians expand the cheeks and entire skull, whereas Latimeria lower the mandible. In the head of Latimeria, only the muscles capable of an efficient depression of the snout were found, and the mechanism of its elevation remained a troublesome puzzle. This deadlock gave rise to concepts anticipating a crucial effect of the m. coracomandibularis mediated by the mentioned accessory movements. However, in rhipidistians the mandible was unable to expand actively, like a sprawling stepladder, under the action of the retrograde force of the mentioned muscle, since the reaction of the hyomandibulare that takes up this force has a medial component constricting the mandible. Whereas in Latimeria the upward move of the posterior end of the mandible that is presumably depressed by this muscle cannot facilitate the snout elevation, because the flexible upper part of the hyoid arch is unable to serve as a required brace between the posterior end of the mandible and the otoccipital portion of the skull. The inability of the m. coracomandibularis to elevate the ethmosphenoid even in such an indirect way was proved by the elongation of this muscle in experiments on the forced elevation of the snout in fresh (thawed) specimens of Latimeria, performed by other authors. This shows that in live Latimeria a contraction of the m. coracomandibularis leads to a depression rather than an elevation of the snout. Rebound resistance of the notochord to a depression of the snout revealed in these manipulations gave rise to assumptions concerning its crucial roles played in snout elevation. However, in this case the notochord is anticipated to be first compressed by the upward move of the otoccipital portion resulting from the epaxial muscles’ contraction. Nobody minded that the ability of the notochord as an axial skeleton to resist the force of the parietal musculature is based on the incompressibility of its semi-liquid content (liquid in the anterior segment of the notochord in Latimeria). Its content always being exposed to high pressure; the notochord acts not only as a liquid skeleton, but also as a hydraulic drive. A forward pressure of the notochord to the posterior end of the ethmosphenoid portion set a constant tendency for snout elevation in rhipidistians, which was compensated for in these fishes by large m. subcephalicus and m. coracomandibularis. In Latimeria, the two-unit construction of the neurocranium does not downgrade its protective properties, because its relatively small brain is located wholly in the posterior unit. Precision of the mutual mobility of the units in the sagittal plane is enhanced by sliding articulations of their overlapping edges. The construction of the skull reflects an adaptation to the optimal use of the pressure of the notochord, which originally exceeds the functional requirements of the visceral apparatus. The major portion of this force is passively taken up by the intracranial articulation, while the lesser one is used for elevating the snout under the control of m. subcephalicus, m. coracomandibularis, and m. adductor mandibulae (only in Latimeria and, possibly, extinct coelacanths due to the characteristic association of this movement with the mandible depression). When the snout is elevated, the anterior end of the notochord is displaced downward due to a soft suspension in the fenestra at the base of the otoccipital portion.
The problem of vertebrate head metamerism was first posed more than 200 years ago. This issue gave rise to two approaches: segmentalism, which relies on the model of the typical head segment, and antisegmentalism, which rejects the existence of cephalic segments at all. Probably the truth lies somewhere in the middle. Data on the development of the head mesoderm, cranial neural crest and cranial nerves leads to the conclusion that there are five metameres in the vertebrate head: premandibular, mandibular, hyoid, 1st metahyoid and 2nd metahyoid. According to the hypothesis of F. Edgeworth, this number of head metameres is primary; head spreading back occurred as a result of the polymerization of visceral arches inside the nervus vagus metamere which had originally included only the 2nd metahyoid arch. According to the hypothesis of K. Gegenbaur, had always been more visceral arches in this area and the branchial nerves merged into a single nervus vagus system only secondarily. Cambrian palaeontology may assist in resolving this controversy. In any case, vertebrate head metamerism is primarily heteronomous in the sense of P.P. Ivanov: the premandibular and mandibular metameres are morphologically atypical and lie beyond the Hox gene expression zone. Developmental biology shows that the bodies of other metameric animals are arranged based on similar principles.
ZELENKOV N.V., STIDHAM T.A.
xml:lang="en"> The fossil avian genus Presbyornis and its relatives (Family Presbyornithidae) are almost universally considered as one of the oldest known filter-feeding specialists among Anseriformes. Such an assumption is based almost entirely on the bill morphology which in Presbyornis is very similar to that of some modern ducks. However, the quadrate bone (key element of the kinetic apparatus of the avian skull) is different in Presbyornis as compared to that in other anseriforms, and shares plesiomorphic similarities with primitive non filter-feeding galliforms. This observation alone requires a functional explanation, as no modern (filter-feeding) anseriforms possess such quadrate bone. Here, we analyze the structural adaptations to filter-feeding in the feeding apparatus of modern ducks, as developed mainly by the late Prof. F.Ya. Dzerzhinsky, and assess their presence in the skull of Presbyornis. We show that a duck-like bill is one of the few duck-like features in the skull of Presbyornis, and most other functional units of its feeding apparatus are similar to those of Galliformes. Most importantly, Presbyornis lacks features indicative of the presence of the ligament-based system fixing the lower jaw against a rostral and caudal displacement. Such fixation is necessary for powerful piston-like tongue movements which in modern ducks provide water inflow and expulsion during filtration. Thus, Presbyornis could not have effectively filtrated very small particles using high-frequency jaw and tongue movements (as do modern ducks) and most likely fed on larger objects which it filtered with slower jaw movements. Presbyornis likely illustrates an important step in the evolution of Anserifomes, when these birds switched from feeding on fixed (likely underwater) to floating food items. The acquisition of specialized filter-feeding in anatids may be viewed as a gradual process initiating from a Presbyornis-like feeding apparatus. Our conclusions highlight a slow and stepwise evolution of the complex morphological traits and emphasize a mosaic nature of intermediate forms.
xml:lang="en"> Places of origin of certain pelvic muscles of the extinct Haast's eagle are reconstructed. The reconstruction is based on the detailed drawing of the Haast's eagle pelvis from the paper of Richard Owen (1879). Outward rotation of the femur by its muscular retractors is compensated by mm. iliotrochanterici. Powerful muscular retractors and mm. iliotrochanterici along with the tilted postacetabular pelvis were involved in the process of tearing large prey.
The origin of flapping flight in animals is always the result of such profound transformations of the organism that, in every case, this process presents a significant problem for the reconstruction of an evolutionary scenario. The flight of mammals is no exception. The theory of the origin of bats from a gliding ancestor is well substantiated and acknowledged by the majority of researchers. Nevertheless, works that deny the very possibility of the flapping flight origin from gliding are still published. In this article, I consider the main arguments of the opponents of the gliding ancestor and propose justifications for the untenability of these objections. The following issues are considered: the role of food specialization in the formation of flight; the homology of the parts of the flying membrane; the inefficiency of flapping flight using “terminal” wings; and, finally, the fundamental possibility of flapping by a glider wing in terms of aerodynamics. An explanation is offered for the rarity of the use of gliding flight in birds and bats. Moreover, features of the locomotor apparatus of the most primitive bat Onychonycteris are discussed in comparison with modern representatives of the order, and morphological evidences is proposed for the leading role of flapping flight already at this archaic stage of invading the air.