On the Classification of the Taxon Tetrapoda

Løvtrup, S

doi:10.1093/sysbio/34.4.463

Cited by 26 publications

(45 citation statements)

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“…After Mu¨l-ler (1831) proved their affiliation to the Amphibia, the debate centred on the question of whether caecilians are more closely related to other Recent Amphibia (the Lissamphibia concept; e.g. Peter 1898; Trueb and Cloutier 1991;Reiss 1996;Laurin 1998), to Amniota (Løvtrup 1985) or to Palaeozoic forms (e.g. Haeckel 1866; Kingsley 1902;Carroll and Currie 1975).…”

Section: Phylogenetic Implicationsmentioning

confidence: 99%

Skeletal development of the direct-developing caecilian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae)

2005

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A few previous studies of skeletal and especially skull development in Gymnophiona often provided contradictory results. We studied the development of the skull and vertebral column of Gegeneophis ramaswamii, a direct-developing Indian caeciliid, based on 13 specimens. The chondrocranium forms at (Brauer in Zool Jahrb Anat 12:477-508,1899) stage 38. First dermal and perichondral ossifications occur at stage 40. The first dermal bones to form are the mentomeckelian, dentary, angular, vomer, and premaxillary. These are followed by the coronoid, palatine, pterygoid, maxillary, and the skull-roofing bones. The last occurring dermal ossifications are the parasphenoid and the squamosal. We present evidence for the occurrence of a lacrimal bone. No ectopterygoid, basioccipital, supraoccipital, pleurosphenoid, postorbital, or supratemporal elements were found. We assess the homology of the bones constituting the caecilian skull and discuss the above-mentioned terminologies. The phylogenetic implications of our findings are briefly discussed and we conclude that the evidence from developmental morphology is at present consistent with a monophyletic Lissamphibia of temnospondyl origin.

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Section: Phylogenetic Implicationsmentioning

confidence: 99%

Skeletal development of the direct-developing caecilian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae)

2005

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“…The monophyletic synapsid lineage, on the other hand, terminates in mammals and represents a Reptilia outgroup according to many investigators (e.g., Gauthier et al 1988a, b;Benton 1991), although this has been disputed by some (Gaffney 1980). This system of Reptilia has been attacked by Gardiner (1982) and Løvtrup (1985), who instead postulated a Mammalia-Aves sister group, which they termed Haemothermia. Although most of the morphological and physiological criteria supporting the grouping of these endothermic amniotes could be refuted as shared derived characters (Kemp 1988), the concept of Haemothermia has found support unexpectedly often in phylogenetic reconstructions using sequences of myoglobin and ␤-hemoglobin (Goodman et al 1987;Bishop and Friday 1988), 18S rRNA (Hedges et al 1990), and tandemly aligned ␣/␤-hemoglobin sequences (Czelusniak et al 1990).…”

Section: Introductionmentioning

confidence: 99%

Phylogenetic Analysis of Reptilian Hemoglobins: Trees, Rates, and Divergences

1998

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Phylogenetic relationships among reptiles were examined using previously published and newly determined hemoglobin sequences. Trees reconstructed from these sequences using maximum-parsimony, neighbor-joining, and maximum-likelihood algorithms were compared with a phylogenetic tree of Amniota, which was assembled on the basis of published morphological data. All analyses differentiated alpha chains into alphaA and alphaD types, which are present in all reptiles except crocodiles, where only alphaA chains are expressed. The occurrence of the alphaD chain in squamates (lizards and snakes only in this study) appears to be a general characteristic of these species. Lizards and snakes also express two types of beta chains (betaI and betaII), while only one type of beta chain is present in birds and crocodiles. Reconstructed hemoglobin trees for both alpha and beta sequences did not yield the monophyletic Archosauria (i.e., crocodilians + birds) and Lepidosauria (i.e., Sphenodon + squamates) groups defined by the morphology tree. This discrepancy, as well as some other poorly resolved nodes, might be due to substantial heterogeneity in evolutionary rates among single hemoglobin lineages. Estimation of branch lengths based on uncorrected amino acid substitutions and on distances corrected for multiple substitutions (PAM distances) revealed that relative rates for squamate alphaA and alphaD chains and crocodilian beta chains are at least twice as high as those of the rest of the chains considered. In contrast to these rate inequalities between reptilian orders, little variation was found within squamates, which allowed determination of absolute evolutionary rates for this subset of hemoglobins. Rate estimates for hemoglobins of lizards and snakes yielded 1.7 (alphaA) and 3.3 (beta) million years/PAM when calibrated with published divergence time vs. PAM distance correlates for several speciation events within snakes and for the squamate left and right arrow sphenodontid split. This suggests that hemoglobin chains of squamate reptiles evolved approximately 3.5 (alphaA) or approximately 1.7 times (beta) faster than their mammalian equivalents. These data also were used to obtain a first estimate of some intrasquamate divergence times.

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“…[alignment; 18S rRNA; RNA secondary structure; Indel; molecular phylogenetics; tetrapod phylogeny. ]One of the early controversies in the phylogenetic relationship among tetrapods is whether birds are more closely related to crocodilians (Romer, 1966;Carroll, 1988;Gauthier et al, 1988) or to mammals (Gardiner, 1982;Løvtrup, 1985). Hedges et al (1990) collected a set of 18S ribosomal RNA (rRNA) sequences to evaluate the relationships among tetrapods and found that the bird-mammal grouping was much more strongly supported, with a bootstrap value of 88%, than the birdcrocodilian grouping.…”

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confidence: 99%

18S Ribosomal RNA and Tetrapod Phylogeny

2003

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Previous phylogenetic analyses of tetrapod 18S ribosomal RNA (rRNA) sequences support the grouping of birds with mammals, whereas other molecular data, and morphological and paleontological data favor the grouping of birds with crocodiles. The 18S rRNA gene has consequently been considered odd, serving as "definitive evidence of different genes providing significantly different estimates of phylogeny in higher organisms" (p. 156; Huelsenbeck et al., 1996, Trends Ecol. Evol. 11:152-158). Our research indicates that the previous discrepancy of phylogenetic results between the 18S rRNA gene and other genes is caused mainly by (1) the misalignment of the sequences, (2) the inappropriate use of the frequency parameters, and (3) poor sequence quality. When the sequences are aligned with the aide of the secondary structure of the 18S rRNA molecule and when the frequency parameters are estimated either from all sites or from the variable domains where substitutions have occurred, the 18S rRNA sequences no longer support the grouping of the avian species with the mammalian species.

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On the Classification of the Taxon Tetrapoda

Cited by 26 publications

References 0 publications

Skeletal development of the direct-developing caecilian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae)

Skeletal development of the direct-developing caecilian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae)

Phylogenetic Analysis of Reptilian Hemoglobins: Trees, Rates, and Divergences

18S Ribosomal RNA and Tetrapod Phylogeny

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