Journal of Paleontology; January 2008; v. 82; no. 1;
p. 183-187; DOI: 10.1666/06-028.1
© 2008 Paleontological Society
TWO MISSISSIPPIAN CAENOGASTROPOD LIMPETS FROM AUSTRALIA AND THEIR MEANING FOR THE ANCESTRY OF THE CAENOGASTROPODA
ALEX COOK1,
ALEXANDER NÜTZEL2 and
JIRI FR
DA3
1 Queensland Museum, PO Box 3300, South Brisbane, Queensland 4101, Australia, <alexc{at}qm.qld.gov.au>,
2 Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Str. 10, 80333 Munich, Germany,
3 Czech Geological Survey, Klárov 3/131, 118 21 Prague 1, Czech Republic
Two new limpets with a caenogastropod-type larval shell are described from the Mississippian (Early Carboniferous) of Australia and assigned to Australoscutula n. gen. of the family Pragoscutulidae. This family has previously been reported only from the Early Devonian of Europe (Czech Republic, Prague Basin). Therefore, it survived the Late Devonian biotic crisis. The fact that one of the earliest certain caenogastropods has a patelliform shell is noteworthy given most other Middle to Late Paleozoic caenogastropods are high-spired or fusiform. Pragosutulidae are interpreted as an early patelliform caenogastropod offshoot derived from coiled ancestors. The Pragoscutulidae are the oldest gastropod limpets with well-preserved larval shells. Their teleoconch is entirely limpet-shaped without helicoid coiling. However, the helicoid turbiniform larval shells suggests that this group evolved from an ancestor with turbiniform or even high-spired adult shell. Moreover, the multi-whorled dextral larval shells show that Pragoscutulidae are Caenogastropoda and document that early Caenogastropoda displayed considerable disparity.
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