View - Kowalewski, M. - Virginia Tech

PALEONTOLOGICAL SOCIETY PAPERS, V. 8, 2002lineages (Kloc, 1992). Kloc (1992, 1993) has alsodocumented the occurrence of possible camouflagestrategies in the Early Devonian selenopeltid trilobiteDicranurus. The elongate cephalic spines aretypically heavily bored and encrusted. Kloc suggeststhat these encrusted spines served to obscure theimage of the trilobite from visual predators in astrategy analogous to that of decorator crabs.Long spines on the calyces and tegmens ofcrinoids are reasonably interpreted as a deterrentto would-be predators. Therefore, it is significantthat no crinoids display spinose calyces prior tothe Wenlock (Silurian), when Calliocrinus displayslarge tegminal spines (Signor and Brett, 1984).Both camerate and cladid crinoids in severalfamilies show a substantial increase in theproportion of spinose genera commencing in EarlyDevonian time (Fig. 11). The proportion of spinosegenera increases to a maximum in Visean time andthen declines in the late Paleozoic in concert withthe decline of camerate crinoids during theChesterian crisis identified by Ausich et al. (1994).Other crinoids, primarily Devonian-LowerCarboniferous camerates, but also a few latePaleozoic cladids, developed elongate spines onthe calyx (Fig. 12). A few genera developed spinoseFIGURE 11—Spinosity in brachiopods. 1—Reconstruction of the productid brachiopod Waagenoconchafrom the Permian of Russia; note juveniles attached to algae by “clasping spines,” and quasi-infaunal modeof life, with “rooting” spines in adults, ×1; from Grant (1966). 2—Brachiopod genera, primarily productides,with spines on the pedicle or both valves. Both show consistent trends; from Signor and Brett (1984).108