Distribution Of Diadectomorpha
The suborder Diadectomorpha consists of three families. The Late Pennsylvanian-Early Permian Limnoscelidae and Early Permian Tseajaiidae have a strictly North American record, whereas members of the Late Pennsylvanian-Early Permian Diadectidae are found in both North America and central Europe. It is important to note here two taxonomic reassessments of reported limnoscelids. Initially, Martens 1989 reported the occurrence of a limnoscelid-like form from the Bromacker locality in the Lower...
Evolution of Selected Characters
The new phylogeny has interesting implications for the evolution of four characters frequently used in considerations of amniote relationships. The tabular-parietal contact has usually been considered to unite embolomeres and seymouriamorphs to diadectomorphs and amniotes Gauthier et al., 1988 , but this character is also present in all lepospondyl groups that have a tabular Figs. 2 and 3 . Therefore, this character is diagnostic of node J embolomeres and batrachomorphs . Of course, the...
literature cited
Berman, D. S, S. S. Sumida, and R. E. Lombard. 1992. Reinterpretation of the temporal and occipital regions in Diadectes and the relationships of diadectomorphs. Journal of Paleontology, 66 481-499. Burggren, W. W., and W. Bemis. 1990. Studying physiological evolution paradigms and pitfalls. Pages 191-228 in Evolutionary Innovations M. H. Nitecki, ed. . Chicago The University of Chicago Press. Carroll, R. L. 1969a. Origin of reptiles. Pages 1-44 in Biology of the Reptilia, Volume 1, Morphology...
methods
Representative taxa of all the major groups of Paleozoic choanates and modern amphibians were selected Appendix 2 . The terminal taxa are restricted to small, well-defined groups whose monophyly is well established. This procedure allows the monophyly of large taxa to be tested and avoids the problematic reconstruction of the primitive condition of relatively diverse taxa. Therefore, taxa such as Seymouriamorpha and Microsauria are not included as terminal taxa but are represented by a sample...
discussion
Comparisons with Previous Phytogenies The close relationships between amniotes and lissamphibians is probably the most unorthodox result of this analysis. However, close relationships between some lepospondyls and amniotes have been postulated in the past. Vaughn 1962 suggested that microsaurs probably a paraphyletic group were closely related to captorhinomorphs another paraphyletic group including early relatives of diapsids . Carroll 1995 produced a phylogeny in which lepospondyls were...
L
One of the most surprising results of this analysis is that Lissamphibia seems to be only remotely related to dissorophoids. Most of the discussions during the past quarter century on the origins of modern amphibians have focused on temnospondyls, especially dissorophoids Bolt, 1969, 1977, 1979 Bolt and Lombard, 1985 Milner, 1988 Trueb and Cloutier, 1991 . The results of our analysis suggest that lissamphibians are lepospondyls. Indeed, Lepospondyli, as redefined here, is one of the most robust...
overview of text
A major concern in approaches to the study of the origin of amniotes is the controversy surrounding nomenclature and phylogeny of the groups formerly known as the Amphibia and the Reptilia. In a rigorous use of cladistic terminology, these two groups are radically re-defined Gauthier et al., 1988b . The word amphibian is not used in a taxonomic sense, although it is often used by authors included here as a colloquial means of communicating the concepts of anamniote tetrapods. Groups of animals...
Origin of Amniotes
The significance of this new phylogeny to the origin of amniotes lies in the recognition of an entirely new set of outgroups beyond diadectomorphs. The new phylogeny indicates that future phylogenetic studies of amniote phylogeny will have to include lepospondyls as outgroups. This has not been a common practice, but it will be necessary if the phylogeny presented here is accepted. Using lepospondyls could certainly help to polarize several characters used in phylogenetic studies of amniotes...