@article {374,
	title = {[TITLE BLANK]},
	journal = {Journal of Morphology},
	volume = {214},
	number = {1},
	year = {1992},
	pages = {1-41},
	abstract = {Postembryonic skeletal development of the pipid frog Xenopus laevis is described from cleared-and-stained whole-mount specimens and sectioned material representing Nieuwkoop and Faber developmental Stages 46-65, plus postmetamorphic individuals up to 6 months old. An assessment of variation of skeletogenesis within a single population of larvae and comparison with earlier studies revealed that the timing, but not the sequence, of skeletal development in X. laevis is more variable than previously reported and poorly correlated with the development of external morphology. Examination of chondrocranial development indicates that the rostral cartilages of X. laevis are homologous with the suprarostral cartilages of non-pipoid anurans, and suggests that the peculiar chondrocranium of this taxon is derived from a more generalized pattern typical of non-pipoid frogs. Derived features of skeletal development not previously reported for X. laevis include 1) bipartite formation of the palatoquadrate; 2) precocious formation of the adult mandible; 3) origin of the angulosplenial from two centers of ossification; 4) complete erosion of the orbital cartilage during the later stages of metamorphosis; 5) development of the sphenethmoid as a membrane, rather than an endochondral bone; and 6) a pattern of timing of ossification that more closely coincides with that of the pelobatid frog Spea than that recorded for neobatrachian species.},
	author = {Trueb, Linda and Hanken, James}
}
@article {199,
	title = {Life history and morphological evolution},
	journal = {Journal of Evolutionary Biology},
	volume = {5},
	number = {4},
	year = {1992},
	pages = {549-557},
	author = {Hanken, James}
}
@article {202,
	title = {Jaw muscle development as evidence from embryonic repatterning in direct-developing frogs},
	journal = {Proceedings of the Royal Society of London - Series B: Biological Sciences},
	volume = {264},
	number = {1386},
	year = {1997},
	pages = {1349-1354},
	abstract = {The Puerto Rican direct-developing frog Eleutherodactylus coqui (Leptodactylidae) displays a novel mode of jaw muscle development for anuran amphibians. Unlike metamorphosing species, several larval-specific features never form in E. coqui; embryonic muscle primordia initially assume an abbreviated, mid-metamorphic configuration that is soon remodelled to form the adult morphology before hatching. Also lacking are both the distinct population of larval myofibres and the conspicuous, larval-to-adult myofibre turnover that are characteristic of muscle development in metamorphosing species. These modifications are part of a comprehensive alteration in embryonic cranial patterning that has accompanied life history evolution in this highly speciose lineage. Embryonic {\textquoteright}repatterning{\textquoteright} in Eleutherodactylus may reflect underlying developmental mechanisms that mediate the integrated evolution of complex structures. Such mechanisms may also facilitate, in organisms with a primitively complex life cycle, the evolutionary dissociation of embryonic, larval, and adult features.},
	author = {Hanken, James and Klymkowsky, Michael W. and Alley, Keith E. and Jennings, David H.}
}
@article {201,
	title = {Mechanistic basis of life-history evolution in anuran amphibians: Direct development},
	journal = {American Zoologist},
	volume = {37},
	number = {2},
	year = {1997},
	pages = {160-171},
	abstract = {The primitive, or ancestral reproductive mode for Recent amphibians involves a complex, biphasic life history. Yet evolutionarily derived, alternate modes are seen in all three living orders and predominate in some clades. Analysis of the consequences and mechanistic bases of one such mode-direct development-can provide insights into the evolutionary opportunities and constraints conferred by the ancestral metamorphic ontogeny. Direct development in the anuran genus Eleutherodactylus involves fundamental alterations to many features of embryonic and posthatching development. At hatching, young emerge as fully formed, albeit tiny versions of the adult; most larval features are absent. Pervasive changes in ontogenetic timing, in particular the precocious (embryonic) formation of many adult structures, appear to be correlated with early development of the thyroid axis, although responsiveness to exogenous thyroid hormone is diminished or even lacking in at least some peripheral tissues. Changes in cranial patterning are likely mediated by the embryonic neural crest, although many gross features of crest biology are highly conserved. Laboratory-based analyses of direct development and other derived reproductive modes in amphibians, using contemporary methods developed for more standard, "model" organisms, may contribute important insights into life-history evolution that complement those derived from analyses of morphology, ecology and phylogeny.},
	author = {Hanken, James and Jennings, David H. and Olsson, Lennart}
}
@article {322,
	title = {There is no highly conserved embryonic stage in the vertebrates: Implications for current theories of evolution and development},
	journal = {Anatomy \& Embryology},
	volume = {196},
	number = {2},
	year = {1997},
	pages = {91-106},
	abstract = {Embryos of different species of vertebrate share a common organization and often look similar. Adult differences among species become more apparent through divergence at later stages. Some authors have suggested that members of most or all vertebrate clades pass through a virtually identical, conserved stage. This idea was promoted by Haeckel, and has recently been revived in the context of claims regarding the universality of developmental mechanisms. Thus embryonic resemblance at the tailbud stage has been linked with a conserved pattern of developmental gene expression - the zootype. Haeckel{\textquoteright}s drawings of the external morphology of various vertebrates remain the most comprehensive comparative data purporting to show a conserved stage. However, their accuracy has been questioned and only a narrow range of species was illustrated. In view of the current widespread interest in evolutionary developmental biology, and especially in the conservation of developmental mechanisms, re-examination of the extent of variation in vertebrate embryos is long overdue. We present here the first review of the external morphology of tailbud embryos, illustrated with original specimens from a wide range of vertebrate groups. We find that embryos at the tailbud stage - thought to correspond to a conserved stage - show variations in form due to allometry, heterochrony, and differences in body plan and somite number. These variations foreshadow important differences in adult body form. Contrary to recent claims that all vertebrate embryos pass through a stage when they are the same size, we find a greater than 10-fold variation in greatest length at the tailbud stage. Our survey seriously undermines the credibility of Haeckel{\textquoteright}s drawings, which depict not a conserved stage for vertebrates, but a stylised amniote embryo. In fact, the taxonomic level of greatest resemblance among vertebrate embryos is below the subphylum. The wide variation in morphology among vertebrate embryos is difficult to reconcile with the idea of a phylogenetically-conserved tailbud stage, and suggests that at least some developmental mechanisms are not highly constrained by the zootype. Our study also highlights the dangers of drawing general conclusions about vertebrate development from studies of gene expression in a small number of laboratory species.},
	author = {Richardson, Michael K. and Hanken, James and Gooneratne, Mayoni L. and Pieau, Claude and Raynaud, Albert and Selwood, Lynne and Wright, Glenda M.}
}
@article {321,
	title = {Somite number and vertebrate evolution},
	journal = {Development},
	volume = {125},
	number = {2},
	year = {1998},
	month = {Jan.},
	pages = {151-160},
	abstract = {Variation in segment number is an important but neglected feature of vertebrate evolution. Some vertebrates have as few as six trunk vertebrae, while others have hundreds. We examine this phenomenon in relation to recent models of evolution and development. Surprisingly, differences in vertebral number are foreshadowed by different somite counts at the tailbud stage, thought to be a highly conserved (phylotypic) stage. Somite number therefore violates the {\textquoteright}developmental hourglass{\textquoteright} model. We argue that this is because somitogenesis shows uncoupling or dissociation from the conserved positional field encoded by genes of the zootype. Several other systems show this kind of dissociation, including limbs and feathers. Bmp-7 expression patterns demonstrate dissociation in the chick pharyngeal arches. This makes it difficult to recognize a common stage of pharyngeal development or {\textquoteright}pharyngula{\textquoteright} in all species. Rhombomere number is more stable during evolution than somite number, possibly because segmentation and positional specification in the hindbrain are relatively interdependent. Although developmental mechanisms are strongly conserved, dissociation allows at least some major evolutionary changes to be generated in phylotypic stages.},
	author = {Richardson, Michael K. and Allen, Steven P. and Wright, Glenda M. and Raynaud, Albert and Hanken, James}
}
@article {90,
	title = {Frogs with claws: Diversity, morphology, and function of pedal unguals in the Astylosternidae},
	journal = {Journal of Morphology},
	volume = {268},
	number = {12},
	year = {2007},
	month = {Dec 2007},
	url = {<Go to ISI>://PREV200800136900},
	author = {Blackburn, David C. and Hanken, James and Jenkins, Farish A., Jr.}
}
