. Bulletin of the British Museum (Natural History), Geology. after Halstead Tarlo (1967). consensus tree Fig. 9 Tree of osteostracan taxa produced by Halstead Tarlo (1967) compared with computer consensus tree rooted at tremataspids. (Ateleaspis as ancestor) rates this character as an acquisition within a small group of osteostracans and so appears a more plausible alternative. My main reasons for preferring the 'Ateleaspis tree' centre on the behaviour of characters 3, 12 and 20. I believe that micromery is a primitive condition and that the tesserate (3) condition is derived. The micromeric
. Bulletin of the British Museum (Natural History), Geology. after Halstead Tarlo (1967). consensus tree Fig. 9 Tree of osteostracan taxa produced by Halstead Tarlo (1967) compared with computer consensus tree rooted at tremataspids. (Ateleaspis as ancestor) rates this character as an acquisition within a small group of osteostracans and so appears a more plausible alternative. My main reasons for preferring the 'Ateleaspis tree' centre on the behaviour of characters 3, 12 and 20. I believe that micromery is a primitive condition and that the tesserate (3) condition is derived. The micromeric undersurface of Ateleaspis and Aceraspis may be associated with the very small trunk scales in these forms which is probably also a plesiomorphic feature (Janvier 1985a: 106). I also believe that the ventral enclosure of the abdominal region (12) is a derived. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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