{"isi":1,"intvolume":"       322","external_id":{"isi":["000335377400001"]},"quality_controlled":"1","abstract":[{"text":"Avian forelimb digit homology remains one of the standard themes in comparative biology and EvoDevo research. In order to resolve the apparent contradictions between embryological and paleontological evidence a variety of hypotheses have been presented in recent years. The proposals range from excluding birds from the dinosaur clade, to assignments of homology by different criteria, or even assuming a hexadactyl tetrapod limb ground state. At present two approaches prevail: the frame shift hypothesis and the pyramid reduction hypothesis. While the former postulates a homeotic shift of digit identities, the latter argues for a gradual bilateral reduction of phalanges and digits. Here we present a new model that integrates elements from both hypotheses with the existing experimental and fossil evidence. We start from the main feature common to both earlier concepts, the initiating ontogenetic event: reduction and loss of the anterior-most digit. It is proposed that a concerted mechanism of molecular regulation and developmental mechanics is capable of shifting the boundaries of hoxD expression in embryonic forelimb buds as well as changing the digit phenotypes. Based on a distinction between positional (topological) and compositional (phenotypic) homology criteria, we argue that the identity of the avian digits is II, III, IV, despite a partially altered phenotype. Finally, we introduce an alternative digit reduction scheme that reconciles the current fossil evidence with the presented molecular-morphogenetic model. Our approach identifies specific experiments that allow to test whether gene expression can be shifted and digit phenotypes can be altered by induced digit loss or digit gain.","lang":"eng"}],"doi":"10.1002/jez.b.22545","date_updated":"2025-09-29T11:18:02Z","publist_id":"4701","year":"2014","scopus_import":"1","language":[{"iso":"eng"}],"user_id":"317138e5-6ab7-11ef-aa6d-ffef3953e345","department":[{"_id":"CaHe"}],"date_published":"2014-01-01T00:00:00Z","volume":322,"citation":{"ista":"Capek D, Metscher B, Müller G. 2014. Thumbs down: A molecular-morphogenetic approach to avian digit homology. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 322(1), 1–12.","apa":"Capek, D., Metscher, B., &#38; Müller, G. (2014). Thumbs down: A molecular-morphogenetic approach to avian digit homology. <i>Journal of Experimental Zoology Part B: Molecular and Developmental Evolution</i>. Wiley-Blackwell. <a href=\"https://doi.org/10.1002/jez.b.22545\">https://doi.org/10.1002/jez.b.22545</a>","short":"D. Capek, B. Metscher, G. Müller, Journal of Experimental Zoology Part B: Molecular and Developmental Evolution 322 (2014) 1–12.","mla":"Capek, Daniel, et al. “Thumbs down: A Molecular-Morphogenetic Approach to Avian Digit Homology.” <i>Journal of Experimental Zoology Part B: Molecular and Developmental Evolution</i>, vol. 322, no. 1, Wiley-Blackwell, 2014, pp. 1–12, doi:<a href=\"https://doi.org/10.1002/jez.b.22545\">10.1002/jez.b.22545</a>.","chicago":"Capek, Daniel, Brian Metscher, and Gerd Müller. “Thumbs down: A Molecular-Morphogenetic Approach to Avian Digit Homology.” <i>Journal of Experimental Zoology Part B: Molecular and Developmental Evolution</i>. Wiley-Blackwell, 2014. <a href=\"https://doi.org/10.1002/jez.b.22545\">https://doi.org/10.1002/jez.b.22545</a>.","ieee":"D. Capek, B. Metscher, and G. Müller, “Thumbs down: A molecular-morphogenetic approach to avian digit homology,” <i>Journal of Experimental Zoology Part B: Molecular and Developmental Evolution</i>, vol. 322, no. 1. Wiley-Blackwell, pp. 1–12, 2014.","ama":"Capek D, Metscher B, Müller G. Thumbs down: A molecular-morphogenetic approach to avian digit homology. <i>Journal of Experimental Zoology Part B: Molecular and Developmental Evolution</i>. 2014;322(1):1-12. doi:<a href=\"https://doi.org/10.1002/jez.b.22545\">10.1002/jez.b.22545</a>"},"month":"01","publication_status":"published","publication":"Journal of Experimental Zoology Part B: Molecular and Developmental Evolution","article_processing_charge":"No","issue":"1","page":"1 - 12","type":"journal_article","status":"public","oa_version":"None","publication_identifier":{"issn":["1552-5007"]},"author":[{"first_name":"Daniel","last_name":"Capek","id":"31C42484-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0001-5199-9940","full_name":"Capek, Daniel"},{"full_name":"Metscher, Brian","first_name":"Brian","last_name":"Metscher"},{"last_name":"Müller","first_name":"Gerd","full_name":"Müller, Gerd"}],"_id":"2248","title":"Thumbs down: A molecular-morphogenetic approach to avian digit homology","day":"01","date_created":"2018-12-11T11:56:33Z","publisher":"Wiley-Blackwell"}