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You are here:   animal list > Sagitta tasmanica and other chaetognaths

Chaetognatha

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                   CHAETOGNATHA

                          Arrow Worms

Michael Le Roux (2011)

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Overview

General Information


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Fossil History


The chaetognaths do not have a very extensive fossil history, as they do not contain a mineralized skeleton (Chen & Huang 2002, Szaniawski 2002). However, there has been one fossil specimen found, Paucijaculum samamithion (figure 1), which dates from the Carboniferous (360-286 MYA). More recently though, Chen & Huang (2002) proposed that a second fossil chaetognath, Eognathacantha ercainella, may have been found from the Lower Cambrian Maotianshan Shale (520 MYA). This specimen bares similar features to modern chaetognaths, including three segments (head, trunk, and possible tail), 12 grasping spines, possible teeth, and possibly a hood – which is chaetognath synapomorphy. Despite these similarities, there are some differences between E. ercainella and modern chaetognaths, including: a narrow, non-rayed tail fin (c.f. wide, rayed tail fin).

Other suggestions regarding the evolution of chaetognaths are that they may be one of the earliest active predators, and that their ancestor was probably planktonic, and lived in close associated with the benthos (Harzsc et al. 2009).





Figure 1: Possible Lower Cambrian fossil Chaetognath. From Chen & Huang 2002.

Images

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(2 objects, created 5/6/2011)

Album: This is a private album that is not visible to anonymous users Great Barrier Reef Invertebrates

Summary:

Date:

Album: 2012

Album: 2011

Classification

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Kingdom
Animalia
Phylum
Chaetognatha
Class
Sagittoidea
Order
Aphragmophora
Family
Sagittidae
Genus
Serratosagitta

Synonyms

Sagitta serratodentata tasmanica ()
Sagitta tasmanica (Thompson, 1947)
Serratosagitta selkirki ((Faggetti, 1958))

Common Names

arrow worm