Squamata (amphisbaenians, “lizards”, mosasaurs, and snakes) is an extremely diverse clade with a rich fossil record. There is little consensus about the interrelationships of the major squamate clades (i.e., Iguania, Gekkota, Scincomorpha, Anguimorpha, Amphisbaenia, and Serpentes), or even the membership of some of these clades. Morphology-based cladistic analyses typically agree only that the major dichotomy in extant squamates is between Iguania and all other taxa. The phylogenetic placement of Amphisbaenia and Serpentes is particularly problematic. Incomplete taxon sampling is likely a major contributing factor to the absence of a consensus about squamate interrelationships. This study examines squamate relationships using 222 ingroup taxa scored for 363 morphological characters. Analysis of these data recovered 2,213 equally short trees with a length of 3,273 steps and a retention index of 0.7164. The results confirm the monophyly of the clades Scleroglossa (extant squamates exclusive of Iguania), Gekkota, Scincomorpha, Lacertoidea, Scincoidea, Anguimorpha, Carusioidea, Platynota, and Varanoidea. Novel results include the identification of a clade containing Scincidae sensu lato, Dibamidae, Amphisbaenia, and Serpentes; identification of a Mesozoic clade containing Bainguis, Eoxanta lacertifrons, Globaura venusta, and Myrmecodaptria; and identification of Dalinghosaurus as a basal shinisaur. A new taxonomic scheme is outlined. The names Iguanomorpha, Scincogekkonomorpha, Evansauria, and Mosasauriformes are applied to the stem-based groups including Iguania, Scleroglossa, Autarchoglossa, and Mosasauria, respectively. The importance of strict rigidity within taxonomy is questioned; taxonomy is most useful as a tool for communication about organisms or groups of organisms.
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3 June 2008
Phylogeny And Systematics Of Squamata (Reptilia) Based On Morphology
Jack L. Conrad
Author Affiliations +
Jack L. Conrad1
1Postdoctoral Fellow, Division of Paleontology (Vertebrate Paleontology), American Museum of Natural History jconrad@amnh.org
1Postdoctoral Fellow, Division of Paleontology (Vertebrate Paleontology), American Museum of Natural History jconrad@amnh.org
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ARTICLE - Introduction
- Subject Matter and Goals
- Historical Analyses
- Precladistic Studies
- Estes et al., 1988
- Molecular Analyses
- Comparisons
- Broadly Sampling Fossils
- Materials and Methods
- Breadth of the Analysis
- Taxon Sampling
- The Outgroup
- Stem Squamates
- Iguania
- Gekkota
- Scincomorpha
- Anguimorpha
- Dibamidae
- Amphisbaenia
- Serpentes
- Data Analysis
- Principle Tree Searches
- Consensus Trees and Apomorphy Lists
- Viewing Trees
- Deformation Comparisons and Decay Indices
- Institutional Abbreviations
- Character List for Squamata
- Citation Abbreviations
- Character Descriptions
- The Characters of Estes et al. (1988)
- Estes et al. (1988) Character 40
- Estes et al. (1988) Character 51
- Estes et al. (1988) Character 57
- Estes et al. (1988) Character 62
- Estes et al. (1988) Character 88–89
- Estes et al. (1988) Character 117
- Estes et al. (1988) Character 123
- Estes et al. (1988) Character 130
- Analyzing the Data
- Phylogeny and Taxonomy
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- Secondary Analyses
- Osteology-Only Analysis
- Iguania (fig. 60a)
- Gekkonomorpha (fig. 60b)
- Scincomorpha (fig. 60b)
- Carusioidea and Anguidae (fig. 60c)
- Platynota (fig. 60d)
- Deformation Comparisons
- Morphology
- Molecular Data
- Bremer Support
- Discussion and Conclusions
- Phylogenetic Hypothesis
- Basic Tree Structure
- Gekkonomorphs, Scincomorphs, and Snake Origins
- Anguimorpha
- Why the Differences?
- Scincophidia, tax. nov.
- A New Test for the Fossorial Ecomorph
- Basal Scincogekkonomorphs and Evansaurs
- Basal Gekkonomorpha?
- Taxonomic Considerations
- Stringency
- Continuity and Superfluous Taxonomy
- Conclusions
- Institutional Abbreviations
- Amphisbaenia
- Anguimorpha
- Gekkota
- Iguania
- Lacertiformes
- Rhynchocephalia
- Scincoidea
- Serpentes
- Xantusiidae
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Jack L. Conrad "Phylogeny And Systematics Of Squamata (Reptilia) Based On Morphology," Bulletin of the American Museum of Natural History, 2008(310), 1-182, (3 June 2008)
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