The early Cambrian eodiscid Neocobboldia chinlinica reportedly displays intraspecific variation in the development of segmentation in the pygidium in which some, but apparently not all, meraspid specimens possessed an additional segment when compared to the holaspid pygidium. Zhang (1989) recognized two axial rings (including the terminal piece) in the pygidium of the smallest meraspid specimens recovered, followed by appearance of forms with three, four, and five axial rings progressively as pygidial size increased. A pygidial size interval followed in which forms with either five or six axial rings occurred, succeeded by an interval in which all forms had five axial rings, which appears to be the final holaspid number. This study aims to assess the pattern of segment accumulation and release in this taxon, in order to test two models put forward recently to explain it.
Trunk segmentation of the Early Cambrian eodiscid trilobite Neocobboldia chinlinica
FUSCO, GIUSEPPE
2008
Abstract
The early Cambrian eodiscid Neocobboldia chinlinica reportedly displays intraspecific variation in the development of segmentation in the pygidium in which some, but apparently not all, meraspid specimens possessed an additional segment when compared to the holaspid pygidium. Zhang (1989) recognized two axial rings (including the terminal piece) in the pygidium of the smallest meraspid specimens recovered, followed by appearance of forms with three, four, and five axial rings progressively as pygidial size increased. A pygidial size interval followed in which forms with either five or six axial rings occurred, succeeded by an interval in which all forms had five axial rings, which appears to be the final holaspid number. This study aims to assess the pattern of segment accumulation and release in this taxon, in order to test two models put forward recently to explain it.Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
