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Related Concept Videos

Convergent Evolution01:54

Convergent Evolution

Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.The structures that arise from convergent evolution are called analogous structures. They are similar in function even if they are dissimilar in structure. Further, structures can be analogous while also...
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Overview of the Skull

The cranium (skull) is the skeletal structure of the head that supports the face and protects the brain. It is subdivided into the facial bones and the brain case, or cranial vault. The facial bones underlie the facial structures, form the nasal cavity, enclose the eyeballs, and support the teeth of the upper and lower jaws.
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Cranial Bones: Superior and Posterior View01:14

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The superior view of the cranium shows the frontal and paired parietal bones.
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Cranial Bones: Lateral View

The lateral view of the cranium is dominated by temporal, sphenoid, and ethmoid bones.
The temporal bone forms the lower lateral side of the skull. The temporal bone is subdivided into several regions. The flattened upper portion is the squamous portion of the temporal bone. Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. Posteriorly is the mastoid portion of the temporal bone. Projecting...
Sutures of the Skull01:22

Sutures of the Skull

The human skull is composed of several bones that come together to protect the brain and support the structures of the face. The junctions where these bones meet are called sutures.
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Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon (singular). Taxa (plural) can span different levels of the evolutionary hierarchy. For instance, the group containing all birds is a taxon (comprising the class Aves), and the group of all species of daisies (the genus Bellis) is a taxon. Phylogenies can likewise include just one genus (i.e., depict species relationships) or span an entire...

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Assessing Species-specific Contributions To Craniofacial Development Using Quail-duck Chimeras
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Cranial shape and correlated characters in crocodilian evolution.

Rudyard W Sadleir1, Peter J Makovicky

  • 1Committee on Evolutionary Biology, University of Chicago, Chicago, IL 60637, USA. rsadleir@uchicago.edu

Journal of Evolutionary Biology
|September 24, 2008
PubMed
Summary

Crocodilian cranial ecomorph shapes (ESCs) influence evolutionary changes in skull traits. These shape transitions impact phylogenetic analyses, suggesting non-phylogenetic factors affect crocodilian evolutionary history.

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Area of Science:

  • Paleontology
  • Evolutionary Biology
  • Comparative Anatomy

Background:

  • Crocodilian phylogeny is complex due to extensive cranial variation and convergence over 80 million years.
  • Conflicting phylogenetic results arise from different data types and homoplasies, particularly concerning slender-snout species like Gavialis gangeticus and Tomistoma schlegelii.
  • Eusuchian cranial ecomorph shapes (ESCs) represent functional or ecological specializations, with slender-snout skulls being one of five identified categories.

Purpose of the Study:

  • To investigate the impact of transitions among general, blunt, and slender ESCs on cranial character-state distributions in phylogenetic reconstruction.
  • To assess character independence and correlations within the morphological character matrix using tree-free analysis.
  • To determine if cranial ecomorph shape categories influence evolutionary patterns of skull morphology in crocodilians.

Main Methods:

  • Concentrated changes test applied to analyze character-state gains associated with ESC transitions.
  • 'Tree-free' character compatibility analysis conducted on the morphological character matrix to evaluate character independence.
  • Comparison of results across morphological, molecular, and combined-data phylogenetic tree topologies.

Main Results:

  • Cranial ESCs significantly affect cranial character-state gains in phylogenetic analyses.
  • Concentrated changes identified numerous character-state changes correlating with transitions to slender, general, and blunt ESCs across different tree topologies.
  • The number of correlated characters varied depending on the phylogenetic tree topology, and character compatibility analysis results differed from the concentrated changes test.

Conclusions:

  • Cranial ecomorph shape categories demonstrably influence evolutionary transitions in crocodilian skull morphology.
  • Phylogenetic inferences in crocodilians may be affected by non-phylogenetic variables that impact cranial morphology, such as ESCs.
  • Understanding the role of ecomorphological specialization is crucial for accurate crocodilian phylogenetic reconstruction.