---
_id: '2248'
abstract:
- lang: eng
  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.'
author:
- first_name: Daniel
  full_name: Capek, Daniel
  id: 31C42484-F248-11E8-B48F-1D18A9856A87
  last_name: Capek
  orcid: 0000-0001-5199-9940
- first_name: Brian
  full_name: Metscher, Brian
  last_name: Metscher
- first_name: Gerd
  full_name: Müller, Gerd
  last_name: Müller
citation:
  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>'
  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>'
  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.'
  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.'
  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>.'
  short: 'D. Capek, B. Metscher, G. Müller, Journal of Experimental Zoology Part B:
    Molecular and Developmental Evolution 322 (2014) 1–12.'
date_created: 2018-12-11T11:56:33Z
date_published: 2014-01-01T00:00:00Z
date_updated: 2021-01-12T06:56:16Z
day: '01'
department:
- _id: CaHe
doi: 10.1002/jez.b.22545
intvolume: '       322'
issue: '1'
language:
- iso: eng
month: '01'
oa_version: None
page: 1 - 12
publication: 'Journal of Experimental Zoology Part B: Molecular and Developmental
  Evolution'
publication_identifier:
  issn:
  - '15525007'
publication_status: published
publisher: Wiley-Blackwell
publist_id: '4701'
quality_controlled: '1'
scopus_import: 1
status: public
title: 'Thumbs down: A molecular-morphogenetic approach to avian digit homology'
type: journal_article
user_id: 4435EBFC-F248-11E8-B48F-1D18A9856A87
volume: 322
year: '2014'
...