results
Only three most parsimonious tree were found. They require 654 steps and have a consistency index of 0.52. The character optimizations and discussions below are all based on the strict consensus tree Fig. 1 . The consensus tree differs substantially from the commonly accepted phylogeny of tetrapods and has important implications for hypotheses of amniote origins. For instance, Lepospondyli includes Lissamphibia and is closely related to diadectomorphs and amniotes. Previously, seymouriamorphs...
Info Wch
Figure 1. A synoptic view of the tetrapod radiations extending from the panderichthyid fishes of the Late Devonian to the major lineages present at the beginning of the Triassic. This synopsis highlights lineages leading to modern tetrapods and is not all-inclusive. Nodes are not intended to show time of origin. Data compiled from information contained in Benton 1990 , Lombard and Sumida 1992 , Ahlberg 1995 , Laurin and Reisz 1995 , and Modesto 1995 . Figure 1. A synoptic view of the tetrapod...
H
0.1 1 mg 10 100 1 g 10 Ovum or Egg Mass Figure 2. Relationship between the rate of oxygen consumption in hatching stage embryos of amphibians Seymour and Bradford, 1995 and reptiles Vleck and Hoyt, 1991 . The equation for amphibians is V02 1.06 M0 52 and that for reptiles is V02 0.68 M 82 in which rate of oxygen consumption V02 has units of il hr and egg mass M has units of mg. Some of the data for amphibian eggs were corrected to 30 C assuming a Q10 of 1.5. The data for reptilian eggs were...
characteristics of specific taxa
Griffiths 1978 provides a detailed summary of monotreme reproduction and development. Luckett 1977 and Hughes 1993 are excellent descriptions of the development of the extraembryonic membranes of echidna, Tachyglossus aculeatus, and platypus, Ornithorhynchus anatinus, that incorporate original observations into classical literature accounts. There is great similarity in the development of the extraembryonic membranes of these two species. An intrauterine phase of development is followed by...
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...
appendicular skeleton
With the conspicuous exception of Holmes 1977, 1980 , few since the early work of Romer 1922 have concentrated on both the osteological and muscular components of the basal tetrapod limb. Figure 5. Left lateral views of the atlas-axis complex of taxa near the origin of amniotes. Except where noted, all illustrations are after Sumida et al. 1992 . A The embolomerous anthracosaurian Proterogyrinus B the seymouriamorph Seymouria C the diadectomorph Limnoscelis D the diadectomorph Diadectes E the...
Introduction Xxx
Water is the most important substance in an animal's body in terms both of composition and of exchange with the environment. Animals are about 70 water by mass and at least 99 water by number of molecules. Animals, whether aquatic or terrestrial, exchange more water molecules per unit time between themselves and their surroundings than any other kind of molecule. Thus, a change in the water availability of an environment can have a major and rapid impact on an animal. The challenge of living in...
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...
Defining Amniota Keycharacter And Crown Concepts
Given the above described phylogeny, applying the crown-clade definition of Amniota is very straightforward. Amniota would consist of the most recent common ancestor of clade E and all its descendants. Thus, the boundaries of this clade are very clear, and this definition is therefore very precise Fig. 2 . Drawing the boundary of Amniota under the traditional definition is more problematical, because it requires knowledge of when the amniote egg arose. With fossil taxa, this requires making...
Info Ptq 1
Initial values seeds for nodes taken as overall mean for the six tip species. Final values resulting from multiple iterations of the squared-change parsimony algorithm. other, then back and forth many times, the nodal values are replaced with the average of the values of all adjacent nodes. If branch segment lengths are not all set equal to one, then this average is computed by weighting by the reciprocal of the branch lengths see Maddison, 1991 Martins and Garland, 1991 . In a fully...
literature cited 1
Beaumont, E. H. 1977. Cranial morphology of the Loxommatidae Amphibia Labyrinthodontia . Philosophical Transactions of the Royal Society of London, B280 29-101. Beerbower, J. R. 1963. Morphology, paleoecology, and phylogeny of the Permo-Pennsylvanian amphibian Diploceraspis. Bulletin of the Museum of Comparative Zoology, 130 33-108. Berman, D. S, R. R. Reisz, and D. A. Eberth. 1985. Ecolsonia cutlerensis, an Early Permian dissorophid amphibian from the Cutler Formation of north-central New...
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...
Distribution Of Captorhinomorpha
The suborder Captorhinomorpha contains two, for the most part easily distinguishable, families the Protorothyrididae and Captorhinidae. Whereas the Protorothyrididae is mainly a Late Carboniferous family, with a few Early Permian members, the Captorhinidae is restricted to the Early and Late Permian, though only the Early Permian distributions are plotted here. The Early Permian captorhinids are known to occur only in the southwestern and Figure 7. Late Carboniferous distributions of the...
Phylogenetic Framework
Our revised phylogeny of Anthracosauria sensu Gauthier et al., 1988b , the clade consisting of amniotes and their nearest amphibian-grade relatives, is depicted in Figure 1. This is based on a cladistic analysis of anthracosaurians summarised in the appendix. This study considered 45 characters for seven terminal taxa Solenodonsauridae, Diadectomorpha, Synapsida, and Sauropsida. It was extracted from a much larger cladistic analysis that considered both the external relationships of amniotes...
Candidates For Omnivory
Among the early amniotes, sundry captorhinids, protorothyridids, araeoscelids, and primitive ophiacodonts and the edaphosaurians are likeliest candidates for omnivory, consuming nutrient-rich plant materials along with invertebrates Fig. 1 . Some of their shared characteristics, such as relatively short coupled bodies, robust limbs, and big feet, indicate a primitive emphasis on wide foraging in terrestrial habitats. Their jaw mechanics embody a derived form of the static-pressure bite marked...
Literature Cited Sej
Abler, W. L. 1992. The serrated teeth of tyrannosaurid dinosaurs, and biting structures in other animals. Paleobiology, 18 161-183. Altman, P. L., and D. S. Dittmer eds. . 1971. Biological Handbooks Respiration and Circulation. Bethesda FASEB Committee on Biological Handbooks. Alvarado, R. H. 1972. The effects of dehydration on water and electrolytes in Ambystoma tigrinum. Physiological Zoology, 45 45-53. Alvarado, R. H. 1979. Amphibians. Pages 261-303 in Comparative Physiology of...