Devonian features in Ludlovian graptolites — no guide to ancestry
Article first published online: 9 OCT 2007
Volume 11, Issue 4, pages 301–306, October 1978
How to Cite
JAEGER, H. (1978), Devonian features in Ludlovian graptolites — no guide to ancestry. Lethaia, 11: 301–306. doi: 10.1111/j.1502-3931.1978.tb01886.x
- Issue published online: 9 OCT 2007
- Article first published online: 9 OCT 2007
A diverse group of Ludlovian Monograptus species is characterized by the retarded growth of thecal hoods, either proximally [M. colonus (Barrande), M. chimaera (Barrande) and M. haupti Kühne] or throughout the rhabdosome [M. micropoma (Jaekel)]. In all these species the hoods are secondary structures, i.e. later growth additions to the thecae. By contrast, in the Devonian Monograptus species the thecal hoods are primary structures, i.e. the outward extension of the dorsal thecal wall. and are formed by undelayed growth that typically is completed before growth of the succeeding theca begins. It is among Ludlovian (M. uncinatus Tullberg) and Pridolian (M. simih Přibyl) forms with homologous hoods that the roots of the majority of the Devonian Monograptus species might be found. The Ludlovian M. micropoma and M. haupti should not be affiliated to the group of Monograptus vomerinus (Nicholson), which is highly characteristic of, and restricted to, the late Llandovery and Wenlock graptolite faunas.