Aptian and Early Albian Douvilleiceratidae, Acanthohoplitidae and Parahoplitidae of Colombia

Seventy nine species and subspecies of the following ammonite genera and subgenera of the families Douvilleiceratidae Parona & Bonarelli, Acanthohoplitidae Stoyanow, and Parahoplitidae Spath are described from the study area. Fourteen species are new; Cheloniceras rectangulatum, Ch. guanense, Epicheloniceras wiedmanni, E. douvillei, E. bradleyiformis, Vectisites (Zambranoites) nodosus, V. (Z.) etayosernai, V. (Z.) obscurus, V. (Z.) grandis, Gargasiceras subpulcher, Colombiceras formosum, Protacanthoplites originalis, Riedelites latecostatus, R. microtuberculatus

On the Barremian-Early Albian biogeography (by ammonites) of Colombia

On the basis of new and published palaeontological and stratigraphical data, the qualitative and quantitative variations in the Barremian-early Albian ammonite fauna of Colombia have been documented and analyzed. The position adopted here is that in the early Barremian the Andean Province became replaced by the Caribbean Subprovince in Colombia. The Caribbean Subprovince became separated as an independent unit from the Andean Province on the generic level (Buergliceras, Pedioceras), but especially on the species level. In the middle/upper Aptian many new endemic genera and subgenera appeared; Juandurhamiceras, Neodeshayesites, Laqueoceras, Zambranoites, Riedelites and Pseudoptychoceras. Besides, many endemic middle Aptian species of other, non-endemic genera appeared. Beginning from the middle Aptian the Caribbean area was a separate biogeographic enitity with the rank of Province; the Colombian region is considered to be the core area of the Caribbean Province

Power scaling of ammonitic suture patterns from Cretaceous Ancyloceratina: constraints on septal/sutural complexity

The spatial scaling of 77 hemisutures from 65 species of Cretaceous heteromorphic ammonites was quantified with the fractal box-counting method. Fractal dimensions within Baculites compressus did not significantly differ between adult hemisutures; however, the juvenile suture of this species did exhibit a significantly lower fractal dimension. This suggests that variation in sutural complexity between explicitly adult ontogenetic stages may not contribute to significant noise in comparisons between other species/morphotypes. High-spired, three-dimensionally coiled heteromorphs with a larger degree of septal asymmetry exhibit higher fractal dimensions in outer whorl hemisutures than inner whorl hemisutures due to their elongation and improved space occupation over a larger whorl surface. Three-dimensionally coiled ammonites also have higher fractal dimensions on average (mean Db = 1.45) with respect to their 2-D coiled counterparts (mean Db = 1.38). All ammonites in this study exhibit a positive trend between sutural complexity and shell size (proxied by whorl height). These relationships suggest that septal frilling is constrained by shell morphology and whorl section geometry during septal morphogenesis. This, in turn, influences the scaling, space-filling properties and scaling limits of ammonitic suture patterns. Sutural/septal complexity is also found to positively influence the amount of liquid retained in marginal septal recesses. However, as these septa approach larger scales, less cameral liquid is retained per septal mass. This may further explain the positive relationship between sutural complexity and shell size