Naslov
Living populations of free-lying bryozoans: Implications for post-Paleozoic decline of the growth habit.

Autori
McKinney, Frank Ken ; Jaklin, Andrej

Izvornik
Lethaia (0024-1164) 26 (1993), 2; 171-179

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
population characteristics; colonies; Palaeozoic; growth; palaeontology; bioturbation; anoxic basins; palaeoecology; Calpensia

Sažetak
Free-lying colonies of bryozoans that grew as thin sheets over fine-grained marine sediments were common during the Paleozoic but apparently have been uncommon for the past 245 million years. Decline in this free-lying growth habit corresponded in general with rise in intensity of marine bioturbation, which has been implied to be a cause of the decline. The occurrence of two short-lived populations of free-lying, sheet-like colonies of the anascan cheilostome bryozoan Calpensia nobilis is consistent with the hypothesized relationship. C. nobilis normally grows as uni- to multilaminate sheets on shells and rock, including common circumrotatory growth. The species recently appeared at two occasions as dense but ephemeral populations of free-lying unilaminate colonies up to 20 cm diameter on muddy sand substrata, 45-50 m deep, in the Northern Adriatic Sea offshore from the southern Istrian Peninsula, Croatia. These population blooms of free-lying C. nobilis occurred adjacent to or within areas where the benthic communities, including bioturbators, recently have been reduced and destabilized by severe anoxic events.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA