Abstract
A new fossil of Ziphiidae from the upper Miocene Gram Formation (ca 9.9–7.2 Ma) is described herein. Computed tomographic scanning of the specimen was performed to visualize the mandibles and to obtain a three-dimensional digital reconstruction. It possesses several characters of the derived ziphiids, such as the dorsoventral thickening of the anterior process of the periotic, the dorsoventral compression of the pars cochlearis and the short unfused symphysis. The specimen cannot be identified beyond the family level, because of the unusual nature of the preserved parts consisting of the mandibles, earbones and postcranial remains. It differs from other ziphiid species from the Gram Formation, Dagonodum mojnum, in its larger size and the more derived morphology of its mandibles and earbones. Its long and thickened stylohyal, combined with its reduced teeth, suggests that this new specimen relied primarily on suction feeding. By contrast, the other ziphiid species from the Gram Formation, D. mojnum, shows adaptations for a more raptorial feeding strategy. Assuming the two species were coeval, their co-occurrence at the same locality with two different feeding strategies, may represent a case of niche separation. They may have hunted different types of prey, thus avoiding direct competition for the same food resource.
Highlights
Beaked whales (Ziphiidae) represent a diversified family of echolocating toothed whales (Odontoceti), currently represented royalsocietypublishing.org/journal/rsos R
Suction feeding forces ziphiids to be more selective with respect to the size of their prey, allowing different species of beaked whales to be sympatric without competing for the same food resource [12,13]
This paper aims at describing the specimen and proposing a reconstruction of its autecology based on morphological features
Summary
Beaked whales (Ziphiidae) represent a diversified family of echolocating toothed whales (Odontoceti), currently represented royalsocietypublishing.org/journal/rsos R. By at least 22 species in six genera [1] with a potential new species of Berardius suspected in the North 2 Pacific [2] Their best-known modern representatives are capable of regular deep dives beyond 1000 m to reach their foraging grounds, where they prey mostly on cephalopods and more occasionally on bathypelagic fish and crustaceans [3,4,5,6,7,8,9,10]. Beaked whales do not use them to capture or manipulate their prey; instead, they use suction as their main feeding strategy, except perhaps for the toothed ziphiid Tasmacetus shepherdi which retains a set of functional teeth in both the upper and lower jaws [4]. Suction feeding forces ziphiids to be more selective with respect to the size of their prey, allowing different species of beaked whales to be sympatric without competing for the same food resource [12,13]
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