N. F. Sohl
J. Pojeta Jr.
1987
<div class="abstract-content"><div class="abstract" data-abstract-type="normal"><p>Cretaceous clavagellid pelecypods are a poorly known group, and have previously received little study.<span> </span><span class="italic">Ascaulocardium armatum</span><span> </span>is conchologically the most complex burrowing pelecypod known. From the study of living clavagellids, it is possible to interpret the various tubes extending outward from the adventitious crypt of<span> </span><span class="italic">A. armatum</span><span> </span>as devices for hydraulic burrowing and deposit feeding. The conchologically complex<span> </span><span class="italic">A. armatum</span><span> </span>occurs near the beginning of the history of the Clavagellidae, and does not seem to have given rise to any younger species.<span> </span><span class="italic">Ascaulocardium armatum</span><span> </span>is known only from the Upper Cretaceous rocks (Santonian–Maastrichtian) of the east Gulf and Atlantic Coastal Plains of the United States of America, as is probably the genus<span> </span><span class="italic">Ascaulocardium</span>. All known Cretaceous clavagellids are burrowing species having a free right valve, and this is the ancestral mode of life of the Clavagellidae. Clavagellids that have a boring habit are a more recent evolutionary development, as are burrowing species having both juvenile valves cemented to the crypt. Clavagellids probably evolved from Jurassic–Early Cretaceous pholadomyids. Almost all Cretaceous clavagellids occur outside the Tethyan Zoogeographic Realm; this distribution is in marked contrast to the modern distribution of the family. Living species mostly inhabit clear, shallow seas in subtropical to tropical shelf areas.</p></div></div>
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10.1017/S0022336000061345
en
Paleontological Society
Ascaulocardium armatum (Morton 1833), new genus (Late Cretaceous): the ultimate variation on the bivalve paradigm
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