"The current concept of the order Asaphida was proposed to accommodate some Cambrian and Ordovician trilobite clades that are characterized by the possession of a ventral median suture. The family Tsinaniidae was recently suggested to be a member of the order Asaphida on the basis of its close morphological similarity to Asaphidae," scientists in Seoul, South Korea report (see also Evolution).
"Postembryonic development of the tsinaniid trilobite, Tsinania canens, from the Furongian (late Cambrian) Hwajeol Formation of Korea, reveals that this trilobite had an adult-like protaspis. Notable morphological changes with growth comprise the effacement of dorsal furrows, sudden degeneration of pygidial spines, regression of genal spines, and loss of a triangular rostral plate to form a ventral median suture. Programmed cell death may be responsible for degenerating the pygidial and genal spines during ontogeny. Morphological changes with growth, such as the loss of pygidial spines, modification of pleural tips, and effacement of dorsal furrows, suggest that T. canens changed its life mode during ontogeny from benthic crawling to infaunal. The protaspid morphology and the immature morphology of T. canens retaining genal and pygidial spines suggest that tsinaniids bear a close affinity to leiostegioids of the order Corynexochida," wrote T.Y. Park and colleagues, Seoul National University.
The researchers concluded: "Accordingly, development of a ventral median suture in T. canens demonstrates that the ventral median suture could have evolved polyphyletically, and thus the current concept of the order Asaphida needs to be revised.."
Park and colleagues published their study in Evolution & Development (Post-embryonic development of the Furongian (Late Cambrian) trilobite Tsinania canens: implications for life mode and phylogeny. Evolution & Development, 2009;11(4):441-455).
For more information, contact T.Y. Park, Seoul National University, School Earth & Environmental Science, Seoul 151747, South Korea.
Publisher contact information for the journal Evolution & Development is: Wiley-Blackwell Publishing, Inc., Commerce Place, 350 Main St., Malden 02148, MA, USA.
Keywords: South Korea, Seoul, Life Sciences, Embryonic Research, Evolution, Seoul National University.
This article was prepared by Science Letter editors from staff and other reports. Copyright 2009, Science Letter via NewsRx.com.
"Research on evolution described by scientists at Seoul National University." Science Letter 4 Aug. 2009: 1209. Academic OneFile. Web. 5 Dec. 2009.
Gale Document Number:A204744594
Disclaimer:This information is not a tool for self-diagnosis or a substitute for professional care.
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