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Homotryblium aculeatum
Homotryblium aculeatum Williams, 1978
Holotype: Williams, 1978, pl. 4, fig. 9
Locus typicus: DSDP-site 370, offshore NW Africa
Stratum typicum: Middle Eocene
Original description: Williams, 1978, p. 797
Diagnosis: Chorate cyst with spherical to slightly ellipsoidal shape. Phragma composed of thin laevigate endophragm and thin scabrate periphragm, from which arise the processes. There is one intratabular process per paraplate, apart from a single, slender, solid acuminate or bifid process, whose location is variable on the hypocyst. Processes are tubiform, slender open distally with and aculeate or secate margin. Aculei and secae may be simple or branched and are commonly recurved. Process formula 4", 6"", 6c, 5""", 1p, 1"""", 2s. Paracingulum delineated by six processes, parasulcus indicated by anterior sulcal paraplate and two processes. Archeopyle epicystal formed from the loss of the four apicals and six precingulars.
Dimensions: cyst diamter 40-53 Ám. Processes, length 19-25 Ám, width 1-3 Ám. Aculei and secae up to 5 Ám in length. 8 specimens measured.
Description: The process formula of Homotryblium aculeatum indicates its gonyaulacacean affinites although it does not reveal the presence of a sixth postcingular paraplate. The paraplates of the epicyst may remain attached or there may be separation of the apicals from the precingulars or within the precingulars. The hypocystal paraplates never show separation. The processes are slender particularly the anterior sulcal and 6"". Some processes proximally exhibit the floral pattern as seen in Homotryblium floripes (Deflandre and Cookson) Stover. Distally the recurved aculei or secae, which can number up to 13 on and individual process, may be simple or bifurcate. Occasionally they exhibit first- and second-order bifurcations as in Spiniferites ramosus (Ehrenberg) Loeblich and Loeblich. The small adventitious process located on the hypocyst is solid, distally acuminate or bifid. The number of processes appears to be constant, there being 10 on the epicyst and 15 on the hypocyst.
Affinities:
Williams, 1978, p. 797
Six species of Homotryblium have been described in the literature. These H. bifurcatum Caro, H. floripes (Deflandre and Cookson) Stover, H. pallidum Davey and Williams, H. plectilum Drugg and Loeblich, H. tasmaniense Cookson and Eisenack, and H. tenuispinosum Davey and Williams. Only H. pallidum, H. tasmaniense, and H. tenuispinosum have simple tubiform processes, open distally. None of these, however, possess the long, recurved, branched aculei or secae as found in H. aculeatum.
Holotype: Williams, 1978, pl. 4, fig. 9
Locus typicus: DSDP-site 370, offshore NW Africa
Stratum typicum: Middle Eocene
Original description: Williams, 1978, p. 797
Diagnosis: Chorate cyst with spherical to slightly ellipsoidal shape. Phragma composed of thin laevigate endophragm and thin scabrate periphragm, from which arise the processes. There is one intratabular process per paraplate, apart from a single, slender, solid acuminate or bifid process, whose location is variable on the hypocyst. Processes are tubiform, slender open distally with and aculeate or secate margin. Aculei and secae may be simple or branched and are commonly recurved. Process formula 4", 6"", 6c, 5""", 1p, 1"""", 2s. Paracingulum delineated by six processes, parasulcus indicated by anterior sulcal paraplate and two processes. Archeopyle epicystal formed from the loss of the four apicals and six precingulars.
Dimensions: cyst diamter 40-53 Ám. Processes, length 19-25 Ám, width 1-3 Ám. Aculei and secae up to 5 Ám in length. 8 specimens measured.
Description: The process formula of Homotryblium aculeatum indicates its gonyaulacacean affinites although it does not reveal the presence of a sixth postcingular paraplate. The paraplates of the epicyst may remain attached or there may be separation of the apicals from the precingulars or within the precingulars. The hypocystal paraplates never show separation. The processes are slender particularly the anterior sulcal and 6"". Some processes proximally exhibit the floral pattern as seen in Homotryblium floripes (Deflandre and Cookson) Stover. Distally the recurved aculei or secae, which can number up to 13 on and individual process, may be simple or bifurcate. Occasionally they exhibit first- and second-order bifurcations as in Spiniferites ramosus (Ehrenberg) Loeblich and Loeblich. The small adventitious process located on the hypocyst is solid, distally acuminate or bifid. The number of processes appears to be constant, there being 10 on the epicyst and 15 on the hypocyst.
Affinities:
Williams, 1978, p. 797
Six species of Homotryblium have been described in the literature. These H. bifurcatum Caro, H. floripes (Deflandre and Cookson) Stover, H. pallidum Davey and Williams, H. plectilum Drugg and Loeblich, H. tasmaniense Cookson and Eisenack, and H. tenuispinosum Davey and Williams. Only H. pallidum, H. tasmaniense, and H. tenuispinosum have simple tubiform processes, open distally. None of these, however, possess the long, recurved, branched aculei or secae as found in H. aculeatum.