![]() Relatively larger (and rare) morphotypes may show slight 'uncoiling' (resembling the typical Hildoceras bifrons), though limitedly to the final part of the adult-stage last whorl. ![]() Besides overall smaller size (usually < 40 mm), Mediterranean specimens attain marked whorl embracement, comparable to that of the kin species Hildoceras semipolitum (albeit retaining a less compressed whorl section). It is historically renown that morphotypes referred to Hildoceras bifrons from the Apennines (Italy) and other Mediterranean localities differ in many ways from the typical species of the Central and North-West Europe. We aim to encourage the broader adoption of this framework and these ideas as a foundation to bring the field close to comprehensive synthesis and reconstruction of organisms. With this we show a framework for consolidating the current understanding of the form–function relationships in an organism, and assess when they are insufficiently characterizing the dynamics those data are being used to explain. Our analysis finds that hydrodynamic measures of performance do little to explain the shift in morphological occupation, highlighting a need for a more robust investigation of alternative functional hypotheses that are often intellectually set aside. However, conflicting interpretations of hydrodynamic performance remain despite this scrutiny, with scant offerings of alternative explanations. The hydrodynamic capacities and limitations of the shell have seen intense scrutiny as a likely explanation of this transition. Across this time interval, morphospace occupation shifts from a broad occupation across Westermann Morphospace to a dense occupation of a region emphasizing an exposed umbilicus and modest frontal profile. We present an example framework for applying these tools to such a problem using the morphological transition of ammonoids from the Middle Triassic to the Early Jurassic. ![]() Joint performance landscapes determined by maximum likelihood are a valuable tool that can be used to synthesize our understanding of these multiple functional hypotheses to further explore an organism's ecology. There is more to each organism than any one of these form–function relationships. However, in order to adequately investigate each of these dense datasets, one must often consider only one functional narrative at a time. Subsequent correlations with environmental constraints (e.g., sea-level changes), although suspected, cannot be shown.Ī boom in technological advancements over the last two decades has driven a surge in both the diversity and power of analytical tools available to biomechanical and functional morphology research. The only pattern that can be connected with a particular episode of Early Jurassic ammonite history is the initial increase in size disparity during the first four biozones attributable to phyletic radiation after the T/J crisis. Our analysis reveals that (1) a size continuum (normal distribution from ''dwarfs'' to ''giants'') exists for all Early Jurassic ammonites (2) although there are no sus-tained trends (e.g., no Cope's rule), the succession is not monotonous and patterns may differ con-spicuously from one biozone to the next and (3) increases and decreases in size range are the most frequent evolutionary styles of size change. ![]() Size patterns are studied for the entire period and then at the biozone scale for the first four stages of the Jurassic (28 Myr), during which ammonites recovered from the crisis at the Tri-assic/Jurassic (T/J) boundary. The shell size of 1236 ammonite species representing all known Early Jurassic faunas is analyzed.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |