. Bulletin of the British Museum (Natural History), Geology. 146. Fig. 16 Palaeogeographic reconstruction of the Iapetus region in mid-Caradoc times (c. 448 Ma) showing the main continental masses of Laurentia, Baltica, Gondwana and Eastern and Western Avalonia. The main brachiopod provinces of Scoto-Appalachian, Baltic and Mediterranean affinity are also shown. At this time, an Anglo-Welsh Province, including these Leinster faunas, was centred on Eastern Avalonia (after Parkes, 1992). bride and Carrigadaggan made measurement of all variates difficult, but a principal component analysis (PCA)
. Bulletin of the British Museum (Natural History), Geology. 146. Fig. 16 Palaeogeographic reconstruction of the Iapetus region in mid-Caradoc times (c. 448 Ma) showing the main continental masses of Laurentia, Baltica, Gondwana and Eastern and Western Avalonia. The main brachiopod provinces of Scoto-Appalachian, Baltic and Mediterranean affinity are also shown. At this time, an Anglo-Welsh Province, including these Leinster faunas, was centred on Eastern Avalonia (after Parkes, 1992). bride and Carrigadaggan made measurement of all variates difficult, but a principal component analysis (PCA) of all three samples shows that in plots of the first four eigen- vectors (see Fig. 17) the two small samples fall within the same region as the Kildare sample. It is possible that analysis of a larger topotype sample of the species would show significant differences between the Welsh and Irish forms, but the original description was based on fewer than ten valves. The mean percentage length of the ventral muscle field relative to the valve length is significantly longer in the Irish form (Kildare - 39% compared to 35%, p < 0-01). This is considered inadequate to justify erection of even a new subspecies, since the Bala sample consisted of only 5 speci- mens. A larger, better preserved sample would probably encompass the same variation seen in the Kildare form. BC PLATE 6 Figs 1-7 Cremnorthis parva Williams. Figs 1-5, Kildare, Grange Hill Horizon 1. 1, BC 12689, internal mould of brachial valve, x 5. 2, 3 12690, internal mould of pedicle valve, latex cast and mould, x 15. 4. BC 12691, internal mould of brachial valve, and BC 12692, internal mould of pedicle valve, both x 6. 5, BC 12693, internal mould of brachial valve, x 3. Figs 6, 7, Carrigadaggan. 6, BC 12694, ventral view of conjoined internal mould, X 10. 7, BC 12695, internal mould of pedicle valve, x 10. Figs 8-16 Skenidioides costatus Cooper. Kildare, Grange Hill Horizon 1. 8, 12, BC 12696, dorsal and ventral views o
Size: 1616px × 1546px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbritishmuseumnaturalhistory, bookcentury1900, bookcoll
