On the Development of Cetacean Extremities: II. Morphogenesis and Histogenesis of the Flippers in the Spotted Dolphin (Stenella attenuata)

Sedmera, David; Mı́šek, Ivan; Klima, Milan

doi:10.1076/ejom.35.2.117.13067

Cited by 26 publications

(40 citation statements)

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“…Kü kenthal (1893) hypothesized the loss of digit III based on the presence of cartilaginous remnants in the shape of phalanges (histology of these elements showed they were cartilaginous and surrounded by connective tissue) and two branches of the radial nerve, instead of a single nerve, between the middle two digits in multiple specimens of balaenopterids (Table 1). This hypothesis has been accepted by several contemporary researchers (i.e., Barnes and McLeod, 1984;Sedmera et al, 1997;Kato, 2002;Aguilar, 2002) and was supported by similar findings of cartilage remnants in two specimens of fetal balaenopterids (Burfield, 1920). However, Howell (1930) believed Kü kenthal's (1893) hypothesis was flawed and that he misidentified metacarpal I as a prepollex and that specimens with the cartilage remnants were likely pathological.…”

mentioning

confidence: 58%

Evolution of hyperphalangy and digit reduction in the cetacean manus

Cooper

Berta

Dawson

et al. 2007

The Anatomical Record

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Cetaceans (whales, dolphins, and porpoises) have a soft tissue flipper that encases most of the forelimb, and elongated digits with an increased number of phalanges (hyperphalangy). In addition, some cetaceans exhibit a reduction in digit number. Although toothed cetaceans (odontocetes) are pentadactylous, most baleen whales (mysticetes) are tetradactylous and also lack a metacarpal. This study conducts a survey of cetacean metacarpal and phalangeal morphologies, traces the evolution of hyperphalangy in a phylogenetic context, optimizes characters onto previously published cetacean phylogenies, and tests various digit loss hypotheses. Dissections were performed on 16 cetacean flippers representing 10 species (8 mysticetes, 2 odontocetes). Phalangeal count data were derived from forelimb radiographs (36 odontocetes, 5 mysticetes), osteological specimens of articulated forelimbs (8 mysticetes), and were supplemented with published counts. Modal phalangeal counts were coded as ordered and unpolarized characters and optimized onto two known cetacean phylogenies. Results indicate that digital ray I is reduced in many cetaceans (except Globicephala) and all elements of digital ray I were lost in tetradactylous mysticetes. Fossil evidence indicates this ray may have been lost approximately 14 Ma. Most odontocetes also reduce the number of phalangeal elements in digit V, while mysticetes typically retain the plesiomorphic condition of three phalanges. Results from modal phalangeal counts show the greatest degree of hyperphalangy in digits II and III in odontocetes and digits III and IV in mysticetes. Fossil evidence indicates cetacean hyperphalangy evolved by at least 7-8 Ma. Digit loss and digit positioning may underlie disparate flipper shapes, with narrow, elongate flippers facilitating fast swimming and broad flippers aiding slow turns. Hyperphalangy may help distribute leading edge forces, and multiple interphalangeal joints may smooth leading edge flipper contour. Anat Rec, 290:654-672, 2007. 2007 Wiley-Liss, Inc.

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mentioning

confidence: 58%

Evolution of hyperphalangy and digit reduction in the cetacean manus

Cooper

Berta

Dawson

et al. 2007

The Anatomical Record

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“…These illustrations also indicate that phalangeal number increases with age, contrary to the observations of Kü kenthal (cited in Howell, 1930). Sedmera et al (1997) compare the hyperphalangy of cetaceans with that of ichthyosaurs, although they fail to mention several important morphological differences between the flippers of the two groups. Each digit in cetaceans is separated from the adjacent digit by blubber and dense fibrous connective tissue, while there are extensive interdigital phalangeal articulations in ichthyosaurs.…”

Section: Modifications Of Perichondral Ossificationmentioning

confidence: 97%

“…There are no delta-shaped bones associated with the supernumerary digit in P. sinus. Sedmera et al (1997) describe the development of the flipper in fetal Stenella attenuata. While they do not observe any delta-shaped bones, their illustrations do show that metacarpals 1 and 5 begin as ovoid centers of ossification, while metacarpals 2, 3, and 4 have concave longitudinal borders at the earliest examined stage.…”

Section: Modifications Of Perichondral Ossificationmentioning

confidence: 99%

Patterns of ossification in the manus of the harbor porpoise (Phocoena phocoena): Hyperphalangy and delta‐shaped bones

Dawson

2003

Journal of Morphology

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With the transition from terrestrial to aquatic habitats, cetacean forelimbs have undergone significant modifications in bone morphology and soft tissue distribution. Some, but not all, of these modifications are also demonstrated in other lineages of extant and extinct secondarily aquatic tetrapods. This study examines the ontogenetic pattern of ossification of the manus of the harbor porpoise (Phocoena phocoena), using plain film radiography. Two modifications examined are hyperphalangy (number of phalanges per digit increased beyond the typical mammalian number) and the morphology of delta-shaped bones. Hyperphalangy in Phocoena phocoena is apparent in digits 2 and 3. Phalangeal counts in all digits are variable (sometimes between the right and left flippers of the same individual) and are not necessarily correlated with age. Phalangeal ossification and epiphyseal fusion proceeds along the proximo-distal axis within each digit. In addition, digits 2 and 3 are at a more advanced stage of ossification than more abaxial digits. Delta-shaped bones appear to be a normal stage in the ossification of phalanges in all digits except the third, and may persist in the adult in certain digits. In humans, this morphology is a developmental anomaly usually associated with other malformations, such as polydactyly or syndactyly. Delta-shaped bones in the cetacean manus display a consistent orientation and the process by which they are formed may be similar to that in extinct marine reptiles.

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“…Another unique morphological feature in the manus of cetaceans is hyperphalangy (Figure 1) (Howell, 1930;Sedmera et al, 1997;Richardson & Oelschläger, 2002;Fedak & Hall, 2004). Recent descriptive embryological studies of the pantropical spotted dolphin (Stenella attenuata) found that hyperphalangy was generated due to the terminal addition of phalanges well into the fetal stages, indicative of a delayed offset (heterochrony) or developmental continuation of digital development (Richardson & Oelschläger, 2002).…”

Section: Introductionmentioning

confidence: 99%

Paedomorphic Ossification in Porpoises with an Emphasis on the Vaquita (<I>Phocoena sinus</I>)

Mellor¹,

Cooper²,

Torre³

et al. 2009

aquatic mammals

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Heterochrony, the change in timing of developmental processes, is thought to be a key process shaping the numerous limb morphologies of tetrapods. Through a delayed offset in digit development, all cetaceans (i.e., whales, dolphins, and porpoises) have evolved supernumary phalanges (hyperphalangy). Moreover, some toothed cetaceans further alter digital morphologies by delayed endochondral and perichondral ossification of individual elements. In the harbor porpoise (Phocoena phocoena), these paedomorphic patterns have created poorly ossified phalangeal elements. However, no studies have addressed this morphology in other porpoise taxa. This study documents the timing of carpal and digital epiphyseal ossification in the poorly studied vaquita (Phocoena sinus) based on radiographs (n = 18) of known-age specimens. Patterns of vaquita manus ossification were compared between other porpoise and delphinid taxa. Adult vaquitas are paedomorphic in carpal, metacarpal, and digital development as they maintain a juvenile ossification pattern relative to that of other porpoise species of equivalent ages. Vaquitas also ossify fewer carpal elements as compared to other porpoise and some delphinid cetaceans, and ossification arrests relative to that of the harbor porpoise. Vaquitas also display sexual dimorphism as females reach a greater body size and display more ossified elements in the manus relative to their paedomorphic male cohorts.

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On the Development of Cetacean Extremities: II. Morphogenesis and Histogenesis of the Flippers in the Spotted Dolphin (Stenella attenuata)

Cited by 26 publications

References 0 publications

Evolution of hyperphalangy and digit reduction in the cetacean manus

Evolution of hyperphalangy and digit reduction in the cetacean manus

Patterns of ossification in the manus of the harbor porpoise (Phocoena phocoena): Hyperphalangy and delta‐shaped bones

Paedomorphic Ossification in Porpoises with an Emphasis on the Vaquita (<I>Phocoena sinus</I>)

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