. Bulletin of the British Museum (Natural History), Geology. 40 CLEAL AND SHUTE. 6 5 at | 4 u I3 2 B. - + â² X X'» â¢x»+- * xx^ -âfx-x X X â a 2 3 4 5 6 7 No. of species of same form-genus 6 8 10 12 14 16 18 20 Total no. of species â Laveineopteris + Macroneuropteris * Neuralethopteris â Neurocallipterls X Neuropterls ⦠Parlpteris *â Sphenoneuropteris Fig. 24 Regression of extinction rates against species numbers (parameters L against N of Table 3); (a) regression against number of species of same form-genus; (b) regression against total number of neuropteroid species. Cleal &
. Bulletin of the British Museum (Natural History), Geology. 40 CLEAL AND SHUTE. 6 5 at | 4 u I3 2 B. - + â² X X'» â¢x»+- * xx^ -âfx-x X X â a 2 3 4 5 6 7 No. of species of same form-genus 6 8 10 12 14 16 18 20 Total no. of species â Laveineopteris + Macroneuropteris * Neuralethopteris â Neurocallipterls X Neuropterls ⦠Parlpteris *â Sphenoneuropteris Fig. 24 Regression of extinction rates against species numbers (parameters L against N of Table 3); (a) regression against number of species of same form-genus; (b) regression against total number of neuropteroid species. Cleal & Thomas (in Cleal 1991) refer to as the Europe Palaeoarea, one of the subdivisions of the Eurameria Palaeo- kingdom. There have been suggestions that this phytochorion can be further subdivided based on the plant fossil record ( Gothan 1954). To investigate this possibility, we have examined our data using cluster analysis, to see if any palaeophytogeographical structure can be discerned. Our data is obviously not entirely suited to such an analysis, as it only represents a small portion of the total fossil assemblages. On the other hand, our data has the merit of having been critically assessed, and is thus preferable to some of the other recently published palaeogeographical analyses, based on uncritical literature trawls. The database Initially, we attempted to look at the data as a whole, using an algorithm that could account for empty data points. This was so the analysis could take into account species being sometimes absent from an area merely because there is no strata of the appropriate age there, rather than there being any fundamental phytogeographical reason. However, the results were disappointing, revealing little structure that could be related to the geographical distribution of the areas. It seemed a strong possibility that the empty data points may have significantly distorted the results. To overcome this, the data was split into five, stra
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