Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . nes deposited in an intertidal to littoral situation (Shone 1976).The ammonite fauna, dominated by Olcostephanus, with occasional Distoloce-ras, Neohoploceras, Partschiceras, Eodesmoceras, Bochianites and Umgazani-ceras (Cooper 1981, 1983), indicates a latest Valanginian age for surfaceexposures, though Hauterivian microfossils are reported from the subsurface(McLachlan & McMillan 1979). LOWER CRETACEOUS TRIGONIOIDA FROM THE ALGOA BASIN 3 SYSTEMATIC PALAEONTOLOGY Order trigonioida Dall, 1889 Discussion If taxonomy is to
Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . nes deposited in an intertidal to littoral situation (Shone 1976).The ammonite fauna, dominated by Olcostephanus, with occasional Distoloce-ras, Neohoploceras, Partschiceras, Eodesmoceras, Bochianites and Umgazani-ceras (Cooper 1981, 1983), indicates a latest Valanginian age for surfaceexposures, though Hauterivian microfossils are reported from the subsurface(McLachlan & McMillan 1979). LOWER CRETACEOUS TRIGONIOIDA FROM THE ALGOA BASIN 3 SYSTEMATIC PALAEONTOLOGY Order trigonioida Dall, 1889 Discussion If taxonomy is to reflect phylogeny, it is clear that the current subdivision ofthe Trigoniidae into as many as 19 subfamilies is inappropriate. It implies thatthis evolutionary radiation is devoid of phyletic lines and that no two subfamiliesare more closely related to each other than to any other subfamily. This isspurious. On phylogenetic grounds these subfamilies are here distributedamong two suborders and four superfamilies (Fig. 1). re 8 co .2 « 5 a> o U) Q- o a co 1 f 2 I. Fig. 1. Hypothesized relationships among the proposed superfamilies of Trigonioida. Charac-ter states: 1 = prominent marginal carina,* myophorian hinge, radial ornament to areasubordinate to transverse ornament; 2 = hinge trigonian, radial ornament to area predominant;3 = marginal carina relatively fine, nodate, area with transverse ornament, flank costaepredominantly nodate, mostly oblique or V-shaped; 4 = escutcheon carina generally obsoleteand marginal carina commonly restricted to umbonal region, shell often pyriform or posteriorlyrostrate, also somewhat produced and often inflated anteriorly. Suborder trigoniina Dall, 1889 Discussion Since strict application of the phylogenetic principles of Hennig (1966) leadsto almost as many supraspecific taxa as there are species, the writer prefers amore utilitarian approach in which paraphyly is preferred to a burgeoning andunwieldy higher taxonomy. Consequently, the subo
Size: 1980px × 1262px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsouthafr, bookcentury1800, bookdecade1890, bookyear1898
