Paired Fins Research Articles

Threatened fishes of the world: Cyprinus pellegrini pellegrini Tchang, 1933 (Cyprinidae)

Common name: Boshi carp (or Barbless carp). Conservation status: Listed as a Grade II State Protected Species in China; listed as vulnerable species in China Red Data Book of Endangered Animal— Pieces (Yue and Chen 1998). Identification: Body elongate; head large and broad; mouth large and terminal; eyes on upper half of head; barbels absent or with a pair of papilla at corners of mouth; scales rather large. Lateral line scales 34–37. Dorsal fin grayish dark, paired and caudal fins light yellow; lower lobe of caudal fin red (Yue and Chen 1998). Illustration: Xianwen (1982). Distribution: Endemic to China, in plateau lakes, Xingyun Lake and Qilu Lake of the Nanpanjiang River system, Yunnan province (Li et al. 1995). Habit and ecology: Lives in upper and middle layers of the deep parts of lakes in calm water (Yue and Chen 1998). Filter-feeder, feeding mainly on zooplankton, but its feeding apparatus is less developed and less powerful (filters less water) than those of bighead and silver carp (Cao 1992). It is highly sensitive to low temperatures (Sun and Liang 2004). Reproduction: Spawning period from April to September, peak in May and June. Batch spawning, eggs adhere to hydrophytes (Yue and Chen 1998) in shallow water where their larvae grow (Jia et al. 2008). Its major population is located in Jiangchuan Hatchery now (Jia et al. 2008). Fecundity can reach up to 130,000 in 3 to 4 year old females (Yue and Chen 1998). Threats: Wild populations have declined dramatically in recent decades from environmental fluctuations; slow growth rate; habitat destruction and loss of spawning grounds by decreasing of hydrophytes because of declining water levels; overfishing; and especially the invasion of exotic species (Jia et al. 2008). The proportion of barbless carp in the total fish yield declined to 20% in the 1960s, to 10% in the early 1970s, and now to less than 1% since the 1980s (Huang 1997). Conservation action: Transplanting, domestication and artificial reproduction have been carried out in Jiangchuan County and Yuanjiang County of Yunnan province (Yue and Chen 1998). Conservation activities were conducted in Heilongjiang Fishery Institute of CAFS Environ Biol Fish (2009) 86:485–486 DOI 10.1007/s10641-009-9558-4

Swimming in four goldfish Carassius auratus morphotypes: understanding functional design and performance employing artificially selected forms

Four goldfish Carassius auratus morphotypes of similar length (50 mm): common (streamlined, full complement of paired and median fins, bifurcated caudal fin), comet ('common like' but with a long, deeply forked caudal fin), fantail (short, deep body with twinned caudal and anal fins) and eggfish (similar to the fantail but lacking a dorsal fin) were compared. Drag, steady swimming kinematics, energetics, fast-start performance, stability in yaw and roll and propulsive muscle ultrastructural characteristics were measured. A performance 'pairing' (common and comet; fantail and eggfish) was a recurrent theme for most performance variables. Fantail and eggfish drag were higher (requiring more thrust at any given velocity) than those for the more streamlined common and comet. This was reflected in kinematics; tailbeat frequency and stride length at any given velocity for the common and comet were lower and higher, respectively, than that of the fantail and eggfish. Common and comet fatigue times were not significantly different from those of their ancestor, crucian carp Carassius carassius, and higher than the fantail and eggfish. The cost of transport of the common and comet (c. 0. 6 mg O(2) kg(-1) m(-1)) was accurately predicted by the mass scaling relationship for fish, but values for the fantail and eggfish (c. 1. 3 mg O(2) kg(-1) m(-1)) were not. Rolling and yawing motions in eggfish (dorsal fin absent) during steady swimming were associated with significant energy losses. Eggfish maximum fast-start acceleration (c. 5 m s(-2)) was poor due to the absence of inertial and lifting contributions to thrust from the dorsal fin and energy wasting rolling motions. Common and comet fast-start performance (average velocity c. 0. 45 m s(-1), maximum velocity c. 1. 2 m s(-1), average acceleration c. 7. 5 m s(-2), maximum acceleration c. 35 m s(-2)) was similar to that of other locomotor generalists (e.g. rainbow trout Oncorhynchus mykiss). Artificially selected fishes can contribute to the understanding of form and movement in fishes and complement studies of the role of locomotor adaptations in natural systems.

Fluid–structure interactions of skeleton-reinforced fins:performance analysis of a paired fin in lift-based propulsion

We investigate the thrust generation capacity of a thin foil consisting of a membrane strengthened by embedded rays that is geometrically, structurally and kinematically similar to pectoral fins of bony fishes during lift-based labriform locomotion. Our numerical model includes a fully nonlinear Euler-Bernoulli beam model of the skeleton and a boundary-element model of the surrounding flow field. The fin undergoes a dorso-ventral flapping activated by rotations of the rays. Both the trailing edge vortices (TEV) and the leading edge vortices (LEV) are accounted for and modeled as shear layers. The thrust generation and propulsion efficiency are examined and documented. Our results show that synchronization of rays is pivotal to the performance of the system. A primary factor that determines the performance of the fin is phase lags between the rays, which create variations of the effective angle of attack at the leading edge as well as shape changes throughout the fin surface. Structural flexibility of the rays leads to passive deformations of the fin, which can increase the thrust generation and the propulsion efficiency.

Heterochronic Shift in Hox-Mediated Activation of Sonic hedgehog Leads to Morphological Changes during Fin Development

We explored the molecular mechanisms of morphological transformations of vertebrate paired fin/limb evolution by comparative gene expression profiling and functional analyses. In this study, we focused on the temporal differences of the onset of Sonic hedgehog (Shh) expression in paired appendages among different vertebrates. In limb buds of chick and mouse, Shh expression is activated as soon as there is a morphological bud, concomitant with Hoxd10 expression. In dogfish (Scyliorhinus canicula), however, we found that Shh was transcribed late in fin development, concomitant with Hoxd13 expression. We utilized zebrafish as a model to determine whether quantitative changes in hox expression alter the timing of shh expression in pectoral fins of zebrafish embryos. We found that the temporal shift of Shh activity altered the size of endoskeletal elements in paired fins of zebrafish and dogfish. Thus, a threshold level of hox expression determines the onset of shh expression, and the subsequent heterochronic shift of Shh activity can affect the size of the fin endoskeleton. This process may have facilitated major morphological changes in paired appendages during vertebrate limb evolution.

Fgf-Dependent Etv4/5 Activity Is Required for Posterior Restriction of Sonic hedgehog and Promoting Outgrowth of the Vertebrate Limb

Crosstalk between the fibroblast growth factor (FGF) and Sonic Hedgehog (Shh) pathways is critical for proper patterning and growth of the developing limb bud. Here, we show that FGF-dependent activation of the ETS transcription factors Etv4 and Etv5 contributes to proximal-distal limb outgrowth. Surprisingly, blockage of Etv activity in early distal mesenchyme also resulted in ectopic, anterior expansion of Shh, leading to a polydactylous phenotype. These data indicate an unexpected function for an FGF/Etv pathway in anterior-posterior patterning. FGF activity in the limb is not only responsible for maintaining posterior-specific Shh expression, but it also acts via Etvs to prevent inappropriate anterior expansion of Shh. This study identifies another level of genetic interaction between the orthogonal axes during limb development.

Stem sarcopterygians have primitive polybasal fin articulation

Among osteichthyans, basal actinopterygian fishes (e.g. paddlefish and bowfins) have paired fins with three endoskeletal components (pro-, meso- and metapterygia) articulating with polybasal shoulder girdles, while sarcopterygian fishes (lungfish, coelacanths and relatives) have paired fins with one endoskeletal component (metapterygium) articulating with monobasal shoulder girdles. In the fin-limb transition, the origin of the sarcopterygian paired fins triggered new possibilities of fin articulation and movement, and established the proximal segments (stylopod and zeugopod) of the presumptive tetrapod limb. Several authors have stated that the monobasal paired fins in sarcopterygians evolved from a primitive polybasal condition. However, the fossil record has been silent on whether and when the inferred transition took place. Here we describe three-dimensionally preserved shoulder girdles of two stem sarcopterygians (Psarolepis and Achoania) from the Lower Devonian of Yunnan, which demonstrate that stem sarcopterygians have polybasal pectoral fin articulation as in basal actinopterygians. This finding provides a phylogenetic and temporal constraint for studying the origin of the stylopod, which must have originated within the stem sarcopterygian lineage through the loss of the propterygium and mesopterygium.

Design and Implementation of Paired Pectoral Fins Locomotion of Labriform Fish Applied to a Fish Robot

In present, there are increasing interests in the research on mechanical and control system of underwater vehicles. These ongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations, scientific deep ocean surveys, military purposes, ecological and water environmental studies, and also entertainments. However, the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency and maneuverability. The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrust forces which make the control of the position and motion difficult. On the other hand, fishes and other aquatic animals are efficient swimmers, posses high maneuverability, are able to follow trajectories, can efficiently stabilize themselves in currents and surges, create less wakes than currently used underwater vehicle, and also have a noiseless propulsion. The fish's locomotion mechanism is mainly controlled by its caudal fin and paired pectoral fins. They are classified into Body and/or Caudal Fin (BCF) and Median and/or paired Pectoral Fins (MPF). The study of highly efficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism. There are few studies on underwater vehicles or fish robots using paired pectoral fins as thruster. The work presented in this paper represents a contribution in this area covering study, design and implementation of locomotion mechanisms of paired pectoral fins in a fish robot. The performance and viability of the biomimetic method for underwater vehicles are highlighted through in-water experiment of a robotic fish.

Phylogeny, classification and character polarity of the Osteostraci (Vertebrata)

Synopsis The jawless Osteostraci are the sister taxon to jawed vertebrates and, thus, are integral to understanding the evolution of gnathostomes from a jawless ancestor. Our understanding of this episode is currently hampered by incomplete knowledge of osteostracan phylogenetics and character polarity. Previous hypotheses of osteostracan intrarelations are reviewed and synthesised into two conflicting hypotheses ‐ ’Tremataspis‐basal’ versus ’Ateleaspis‐basal’ models, both related to the ancestral morphotype of the group. Previous analyses are shown to be limited in three main regards ‐ taxonomic scope, phylogenetic methodology and character polarity. To address this problem, direct observations and reconstructions were made for every osteostracan genus. This enabled a taxonomically comprehensive analysis, utilising global parsimony and out‐group analysis. The inclusion of a morphological range of taxa from both extant and extinct osteostracan‐related clades (pteraspidomorphs, galeaspids, placoderms and gnathostomes), enables a test of osteostracan polarity and character evolution. A new phylogeny and classification for the Osteostraci is proposed, identifying three main orders ‐ Benneviaspidida, Zenaspidida and Thyestiida. The ’Ateleaspis‐basal’ model is supported along with the homology of paired pectoral fins of Osteostraci and jawed vertebrates.

The Hox Complex - an interview with Denis Duboule

Denis Duboule is one of the most influential and highly-cited scientists in developmental biology. Born in Geneva in 1955, he holds dual Swiss and French nationality. His undergraduate studies in biology at the University of Geneva included research on mouse embryology. He later learned molecular techniques in the laboratory of Pierre Chambon, becoming a major player in characterising the newly-discovered vertebrate Hox genes. He helped discover their genomic clustering, realising that they had arisen by trans duplication. With Gaunt and Sharpe, he proposed that vertebrate Hox clusters might show spatial colinearity, and subsequently extended this concept to the timing of gene activation (temporal colinearity). Along with the Krumlauf laboratory, he reported the structural and functional conservation of the homeotic systems in flies and vertebrates. His lab was the first to describe nested patterns of Hox gene expression in the developing mouse limb, and later showed that digit-associated Hoxd gene expression was lacking in zebrafish paired fin development. His concept of phylotypic progression helps explain major evolutionary developmental phenomena in terms of Hox gene regulatory networks. His research helped reveal that the genital tubercle may, like the limb, be patterned by Hox genes. His lab developed targeted meiotic recombination (TAMERE), using it to make profound advances in our understanding of Hox gene regulation. Remote enhancers linked to digit patterning have been uncovered, together with a likely mechanism for colinearity. Denis lives in Geneva with his wife Brigitte Galliot, also a scientist, with their four children.

Gait Planning for Steady Swimming Control of Biomimetic Fish Robots

This paper is dedicated to the implementation of biological fish swimming motion onto biomimetic fish robots. By learning from different species of fish, the mechanism design and the motor control of swimming machines could be shaped in different forms. In general, they can be grouped into two major forms, from an engineering viewpoint: serial open-chain design and parallel mechanism design. The gait planning on both forms is then performed based on the well-established theory of fish swimming. By using the associated kinematics equations, the generic solution of the gait planning for multi-link fish robots in the two respective forms of mechanisms is derived. The solution is taken as the gait control input for the swimming testing of a six-link body and/or caudal fin fish prototype and an eight-link media and/or paired fin fish prototype. The experiments show that smooth steady swimming and forward/backward swimming are achievable by making use of the gait planning and control.

Early osteological development of the fins in the hatchery-reared red porgy,Pagrus pagrus(L. 1758)

Summary The present study was undertaken to establish the normal, healthy features of morphological structures at various developmental stages as achieved under well-defined environmental culture conditions (temperature between 16 and 21°C, salinity 36 ppt, pH around 7.6, and oxygen saturation over 95%) common in aquaculture of the species. The pectoral fin supports began to develop at 2.90 mm total length (TL), followed by those of dorsal fins at 5.5 mm TL, caudal fins at 5.6 mm TL, pelvic fins at 5.9 mm TL and anal fins at 6.0 mm TL. The pelvic fins appeared fully at 7.4 mm TL. Development of dorsal lepidotrichia was first observed at 6.9 mm TL, attaining their final number at 7.6 mm TL. The dorsal spines first appeared at 6.5 mm TL and were complete at 7.4 mm TL. The anal lepidotrichia appeared during the development phase from 6.8 to 8.6 mm TL. At 5.6 mm TL, the upward flexion of the urostyle was initiated. The caudal lepidotrichia formed within the primordial fin at 5.6 mm TL and reached the final count at 7.4 mm TL. The caudal dermatotrichia first appeared at 7.3 mm TL and all forms were observed by 15.5 mm TL. The development pattern of fin supports found in Pagrus pagrus is quite similar to that described for other Sparid species.

Ever Since Owen: Changing Perspectives on the Early Evolution of Tetrapods

The traditional notion of a gap between fishes and amphibians has been closed by a wealth of fish-like fossil tetrapods, many discovered since the mid 1980s. This review summarizes these discoveries and explores their significance relative to changing ideas about early tetrapod phylogeny, biogeography, and ecology. Research emphasis can now shift to broader-based questions, including the whole of the early tetrapod radiation, from the divergence from other lobed-finned fishes to the origins of modern amphibians and amniotes. The fish-to-tetrapod morphological transition occurred within the Upper Devonian; the divergence of modern tetrapod groups is an Early Carboniferous event. Modern tetrapods emerged in the aftermath of one of the five major extinction episodes in the fossil record, but the earlier Devonian tetrapod radiation is not well understood. Tetrapod limbs, paired fins, and comparative developmental data are reviewed; again, research emphasis needs to change to explore the origins of tetrapod diversity.

The pectoral fin of Panderichthys and the origin of digits

One of the identifying characteristics of tetrapods (limbed vertebrates) is the presence of fingers and toes. Whereas the proximal part of the tetrapod limb skeleton can easily be homologized with the paired fin skeletons of sarcopterygian (lobe-finned) fish, there has been much debate about the origin of digits. Early hypotheses interpreted digits as derivatives of fin radials, but during the 1990s the idea gained acceptance that digits are evolutionary novelties without direct equivalents in fish fin skeletons. This was partly based on developmental genetic data, but also substantially on the pectoral fin skeleton of the elpistostegid (transitional fish/tetrapod) Panderichthys, which appeared to lack distal digit-like radials. Here we present a CT scan study of an undisturbed pectoral fin of Panderichthys demonstrating that the plate-like 'ulnare' of previous reconstructions is an artefact and that distal radials are in fact present. This distal portion is more tetrapod-like than that found in Tiktaalik and, in combination with new data about fin development in basal actinopterygians, sharks and lungfish, makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal radials present in all sarcopterygian fish.

Description of early ontogeny and osteological development of streaked mojarra Eugerres lineatus (Teleostei: Percoidei: Gerreidae)

Embryos, larvae, and juveniles of the streaked mojarra Eugerres lineatus are described and illustrated from a series of laboratory specimens. The description was based on morphometry, pigmentation pattern, squamation sequence, and osteological development. The eggs were obtained by stripping ripe adults captured in Bahía de La Paz, Baja California Sur, México. Eggs (cleavage egg and embryo phases) had a mean diameter of 0.69 mm with an oil globule of 0.19 mm mean diameter. Eleutheroembryos were 1.05 mm mean notochordal length (NL) at hatching. The yolk sac was absorbed by 2.10 mm mean NL, underwent notochord flexion at 3.16 mm NL-3.86 mm standard length (SL), and transformed to juveniles at 10.0 mm SL. Juveniles were completely scaled by 14.0 mm SL. Osteological development of the neurocranium, jaws and suspensorium, opercular series, hyoid and branchial arches, vertebral column and ribs, and the paired and unpaired fins and the supports were studied. The identification of the earliest stages of development of E. lineatus compared to the other gerreids and allied taxonomic groups present along the northwestern Mexican coast is possible only in the juvenile period (24.1 mm SL), based on anal fin ray count (II, 9-III, 8), the presence of papilliform teeth, and the number of gillrakers on the lower first pharyngeal arch (15–20).

Conservation of linkage and evolution of developmental function within the Tbx2/3/4/5 subfamily of T-box genes: implications for the origin of vertebrate limbs

T-box genes encode a family of DNA-binding transcription factors implicated in numerous developmental processes in all metazoans. The Tbx2/3/4/5 subfamily genes are especially interesting because of their key roles in the evolution of vertebrate appendages, eyes, and the heart, and, like the Hox genes, the longevity of their chromosomal linkage. A BAC library derived from the single male amphioxus (Branchiostoma floridae) used to sequence the amphioxus genome was screened for AmphiTbx2/3 and AmphiTbx4/5, yielding two independent clones containing both genes. Using comparative expression, genomic linkage, and phylogenetic analyses, we have reconstructed the evolutionary histories of these members of the T-box gene family. We find that the Tbx2-Tbx4 and Tbx3-Tbx5 gene pairs have maintained tight linkage in most animal lineages since their birth by tandem duplication, long before the divergence of protostomes and deuterostomes (e.g., arthropods and vertebrates) at least 600 million years ago, and possibly before the divergence of poriferans and cnidarians (e.g., sponges and jellyfish). Interestingly, we find that the gene linkage detected in all vertebrate genomes has been maintained in the primitively appendage-lacking, basal chordate, amphioxus. Although all four genes have been involved in the evolution of developmental programs regulating paired fin and (later) limb outgrowth and patterning, and most are also implicated in eye and heart development, linkage maintenance--often considered due to regulatory constraints imposed by limb, eye, and/or heart associated gene expression--is undoubtedly a consequence of other, much more ancient functional constraints.

Pelvic fin locomotor function in fishes: three-dimensional kinematics in rainbow trout (Oncorhynchus mykiss)

The paired pelvic fins in fishes have been the subject of few studies. Early work that amputated pelvic fins concluded that these fins had very limited, and mainly passive, stabilizing function during locomotion. This paper is the first to use three-dimensional kinematic analysis of paired pelvic fins to formulate hypotheses of pelvic fin function. Rainbow trout (Oncorhynchus mykiss) were filmed swimming steadily at slow speeds (0.13-1.36 BL s(-1)) and during manoeuvres (0.21-0.84 BL s(-1)) in a variable speed flow tank. Two high-speed cameras filmed ventral and lateral views simultaneously, enabling three-dimensional analysis of fin motion. During steady swimming, pelvic fins oscillate in a regular contralateral cycle. This cyclic oscillation appears to have active and passive components, and may function to dampen body oscillation and stabilize body position. During manoeuvres, pelvic fins move variably but appear to act as trimming foils, helping to stabilize and return the body to a steady swimming posture after a manoeuvre has been initiated. Fins on the inside of the turn move differently from those on the outside of the turn, creating an asymmetric motion. This paper challenges the understanding that pelvic fins have a limited and passive function by proposing three new hypotheses. First, pelvic fins in rainbow trout have complex three-dimensional kinematics during slow-speed steady swimming and manoeuvres. Second, pelvic fins are moved actively against imposed hydrodynamic loads. Third, pelvic fins appear to produce powered correction forces during steady swimming and trim correction forces during manoeuvres.

A new anaspid fish from the Middle Silurian Cowie Harbour fish bed of Stonehaven, Scotland

ABSTRACT A new birkeniid anaspid, Cowielepis ritchiei gen. et sp. nov., from the mid Silurian Cowie Harbour fish bed in Scotland is described on the basis of three specimens. Although sharing characters with various well-known anaspids, it possesses a unique combination of features that justifies the establishment of a new genus. Cowielepis is characterized by a single row of dorsolateral scales and a distinctive skull roof pattern with a large pineal plate and elongated posterior plates. The presence of paired ventrolateral fins in C. ritchiei supports previous suggestions that all anaspids possess such fins, but leaves open the question of homology with the gnathostome pectoral fin.

Variability and Conservation in Late Chondrichthyan Development: Ontogeny of the Winter Skate (Leucoraja ocellata)

The ontogeny of the northwestern Atlantic batoid, Leucoraja ocellata, is described with special focus on the development of skate specific morphologies and the development of the fins. The results show that the sequence of events involving the early outgrowth of the paired fins and the initial development of the pharyngeal region is remarkably constant in skates, holocephalians, and sharks. However, differences exist in timing of the reshaping of the mandibular arch region, development of branchial filaments, median fins, denticles, and the order of branchial cleft formation. Despite the similarities of early events related to development of the branchial region and initial outgrowth of the fins, later stages are increasingly characterized by taxon-specific morphologies making a universal staging table for chondrichthyans less applicable. The staging table presented in this study represents an important resource for future studies on batoid embryology.

Tri-phasic expression of posterior Hox genes during development of pectoral fins in zebrafish: Implications for the evolution of vertebrate paired appendages

During development of the limbs, Hox genes belonging to the paralogous groups 9–13 are expressed in three distinct phases, which play key roles in the segmental patterning of limb skeletons. In teleost fishes, which have a very different organization in their fin skeletons, it is not clear whether a similar patterning mechanism is at work. To determine whether Hox genes are also expressed in several distinct phases during teleost paired fin development, we re-analyzed the expression patterns of hox9–13 genes during development of pectoral fins in zebrafish. We found that, similar to tetrapod Hox genes, expression of hoxa/ d genes in zebrafish pectoral fins occurs in three distinct phases, in which the most distal/third phase is correlated with the development of the most distal structure of the fin, the fin blade. Like in tetrapods, hox gene expression in zebrafish pectoral fins during the distal/third phase is dependent upon sonic hedgehog signaling ( hoxa and hoxd genes) and the presence of a long-range enhancer ( hoxa genes), which indicates that the regulatory mechanisms underlying tri-phasic expression of Hox genes have remained relatively unchanged during evolution. Our results suggest that, although simpler in organization, teleost fins do have a distal structure that might be considered comparable to the autopod region of limbs.

Major transitions in vertebrate evolution

Acknowledgments Introduction: Studying Evolutionary Transitions among Vertebrates Hans-Dieter Sues and Jason S. Anderson 1. Plasticity of and Transitions between Skeletal Tissues in Vertebrate Evolution and Development Brian K. Hall and P. Eckard Witten 2. Homologies and Evolutionary Transitions in Early Vertebrate History Philippe Janvier 3. Paired Fins of Jawless Vertebrates and Their Homologies across the Agnathan-Gnathostome Transition Mark V. H. Wilson, Gavin F. Hanke, and Tiiu Marss 4. MODEs of Developmental Evolution: An Example with the Origin and Definition of the Autopodium Hans C. E. Larsson 5. Incorporating Ontogeny into the Matrix: A Phylogenetic Evaluation of Developmental Evidence for the Origin of Modern Amphibians Jason S. Anderson 6. The Cranial Anatomy of Basal Diadectomorphs and the Origin of Amniotes Robert R. Reisz 7. Snake Phylogeny, Origins, and Evolution: The Role, Impact, and Importance of Fossils (18692006) Michael W. Caldwell 8. The Beginnings of Birds: Recent Discoveries, Ongoing Arguments, and New Directions Luis M. Chiappe and Gareth J. Dyke 9. Successive Diversifications in Early Mammalian Evolution Zhe-Xi Luo 10. The Terrestrial to Aquatic Transition in Cetacea Mark D. Uhen Contributors Index