Publications

1993
Hanken, J. & Hall, B.K. ed., 1993. The Skull: Vol. 1, Development; Vol. 2, Patterns of Structural and Systematic Diversity; Vol. 3, Functional and Evolutionary Mechanisms, Chicago: University of Chicago Press.
Hanken, J. & Thorogood, P., 1993. Evolution and Development of the Vertebrate Skull - the Role of Pattern Formation. Trends in Ecology & Evolution , 8 , pp. 9-15.Abstract

The vertebrate skull is anatomically complex and phylogenetically diverse; it presents unique opportunities to examine the role of developmental processes in evolutionary change. Previous studies have largely examined phylogenetic trends in tissue composition or change in the timing of developmental events (heterochrony). Additional important insights may be gained if skull evolution and development are viewed from the standpoint of pattern formation. Contemporary models of pattern formation offer the possibility of linking developmental mechanisms of cranial morphogenesis from the level of genes, through cell biology, to adult form.

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Hanken, J. & Wake, D.B., 1993. Miniaturization of Body Size: Organismal Consequences and Evolutionary Significance. Annual Review of Ecology and Systematics , 24 , pp. 501-519.Abstract

Miniaturization, or the evolution of extremely small adult body size, is a widespread phenomenon in animals. It has important consequences for both organismal biology and phyletic diversification above the species level. The miniaturized phenotype is a complex combination of ancestral and derived traits, including reduction and structural simplification, increased variability, and morphological novelty. Many features likely represent secondary consequences of size decrease, which may be the result of selection primarily for small body size or some related attribute such as life history characteristics. In some cases, miniaturization has resulted in novel bauplans associated with the origin of higher taxa. Evaluation of causes and consequences of miniaturization should consider obvious features of physical size as well as less obvious, but biologically important, features such as genome and cell size.

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Hanken, J., 1993. Model Systems Versus Outgroups: Alternative Approaches to the Study of Head Development and Evolution. American Zoologist , 33 , pp. 448-456.Abstract

There is widespread recognition of a recent coming together of developmental and evolutionary biology in the study of problems of mutual interest. Contemporary studies into the development and evolution of the head largely comprise two parallel approaches, or research strategies: the model systems approach and the comparative approach. The two strategies share the same general goal-greater understanding of cranial development and evolution-but typically emphasize different problems, ask different questions, and employ different methods, reflecting the contrasting backgrounds and biases of each group of investigators; there has been relatively little true synthesis. Each strategy is making important and valid contributions, but both have limitations. Resolution. of many fundamental and long-standing problems in cranial development and evolution will require a combined approach that incorporates the technical and conceptual strengths of each discipline.

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1992
Thorogood, P. & Hanken, J., 1992. Body building exercises. Curr. Biol. , 2 , pp. 83-85. PDF
Hanken, J., et al., 1992. Cranial Ontogeny in the Direct-Developing Frog, Eleutherodactylus coqui (Anura, Leptodactylidae), Analyzed Using Whole-Mount Immunohistochemistry. Journal of Morphology , 211 , pp. 95-118.Abstract

Direct development in amphibians is an evolutionarily derived life-history mode that involves the loss of the free-living, aquatic larval stage. We examined embryos of the direct-developing anuran Eleutherodactylus coqui (Leptodactylidae) to evaluate how the biphasic pattern of cranial ontogeny of metamorphosing species has been modified in the evolution of direct development in this lineage. We employed whole-mount immunohistochemistry using a monoclonal antibody against the extracellular matrix component Type II collagen, which allows visualization of the morphology of cartilages earlier and more effectively than traditional histological procedures; these latter procedures were also used where appropriate. This represents the first time that initial chondrogenic stages of cranial development of any vertebrate have been depicted in whole-mounts.Many cranial cartilages typical of larval anurans, e.g., suprarostrals, cornua trabeculae, never form in Eleutherodactylus coqui. Consequently, many regions of the skull assume an adult, or postmetamorphic, morphology from the inception of their development. Other components, e.g., the lower jaw, jaw suspensorium, and the hyobranchial skeleton, initially assume a mid-metamorphic configuration, which is subsequently remodeled before hatching. Thirteen of the adult complement of 17 bones form in the embryo, beginning with two bones of the jaw and jaw suspensorium, the angulosplenial and squamosal. Precocious ossification of these and other jaw elements is an evolutionarily derived feature not found in metamorphosing anurans, but shared with some direct-developing caecilians. Thus, in Eleutherodactylus cranial development involves both recapitulation and repatterning of the ancestral metamorphic ontogeny. These modifications, however, are not associated with any fundamental change in adult morphology and cannot at this time be causally linked to the evolutionary success of this extraordinarily speciose genus.

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Hanken, J., 1992. Life History and Morphological Evolution. Journal of Evolutionary Biology , 5 , pp. 549-557. PDF
Trueb, L. & Hanken, J., 1992. Skeletal Development in Xenopus laevis (Anura: Pipidae). Journal of Morphology , 214 , pp. 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.

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1991
Hanken, J. & Wake, M.H. ed., 1991. Symposium: Experimental approaches to the analysis of form and function. Amer. Zool. , 31 , pp. 601-756. PDF
Wake, D.B., et al., 1991. Development and Evolution - the Emergence of a New Field. In E. C. Dudley, ed. Unity of Evolutionary Biology: The Proceedings of the Fourth International Congress of Systematic and Evolutionary Biology. Portland. Portland: Dioscorides Press, pp. 582-588. PDF
Hanken, J. & Wake, M.H., 1991. Introduction to the Symposium: Experimental Approaches to the Analysis of Form and Function. American Zoologist , 31 , pp. 603-604. PDF
Klymkowsky, M.W. & Hanken, J., 1991. Whole-Mount Staining of Xenopus and Other Vertebrates. In B. K. Kay & H. B. Peng, ed. Xenopus laevis: Practical Uses in Cell and Molecular Biology. New York. New York: Academic Press, pp. 419-441. PDF
1990
Hanken, J., 1990. Review of Thomson, K.S., Morphogenesis and Evolution. Copeia , 1990 , pp. 247-248. PDF
Dinsmore, C.E. & Hanken, J., 1990. Amputation Level-Dependent Patterning in Urodele Limb Regeneration. Journal of Morphology , 205 , pp. 77-84. PDF
Dwyer, C.M. & Hanken, J., 1990. Limb Skeletal Variation in the Jemez Mountains Salamander, Plethodon neomexicanus. Canadian Journal of Zoology , 68 , pp. 1281-1287. PDF
Roth, G., et al., 1990. Miniaturization in Plethodontid Salamanders (Caudata, Plethodontidae) and Its Consequences for the Brain and Visual-System. Biological Journal of the Linnean Society , 40 , pp. 165-190. PDF
1989
Hanken, J., 1989. Development and evolution of the neural crest (review of Developmental and Evolutionary Aspects of the Neural Crest). Evolution , 43 , pp. 1337-1338. PDF
Hanken, J., 1989. Developmental characters in phylogenetic inference: a test case using amphibians. In H. Splechtna & H. Hilgers, ed. Trends in Vertebrate Morphology. Fortsch. Zool. pp. 174-179. PDF
Hanken, J., 1989. Development and Evolution in Amphibians. American Scientist , 77 , pp. 336-343. PDF
Lauder, G.V., et al., 1989. How Are Feeding Systems Integrated and How Have Evolutionary Innovations Been Introduced. In D. B. Wake & G. Roth, ed. Complex Organismal Functions : Integration and Evolution in VertebratesComplex Organismal Functions : Integration and Evolution in VertebratesComplex Organismal Functions : Integration and Evolution in Vertebrates. Chichester. Chichester: John Wiley & Sons Ltd. pp. 97-115.

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