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| Antwerpibalaena liberatlas Lavigerie, Bosselaers, Goolaerts, Park, Lambert & Marx, 2020 |
Abstract
Right whales (Balaenidae) are the most distinctive family of extant baleen whales, thanks to their highly arched rostrum, tall lips and robust body shape. They are also the oldest, originating as much as 20 million years ago (Ma). Nevertheless, their fossil record is patchy and frequently understudied, obscuring their evolution. Here, we describe a new stem balaenid, Antwerpibalaena liberatlas, from northern Belgium, adding to the rich but historically problematic baleen whale assemblage of the Pliocene North Sea. Within right whales, Antwerpibalaena forms a clade with two previously described extinct genera, Balaenella and Balaenula. The holotype preserves much of the postcranial skeleton, and informs the emergence of typical balaenid traits like fused neck vertebrae and paddle-shaped flippers. Its size is intermediate between that of extant right whales and most of their extinct forebears revealing a more complex pattern of balaenid size evolution than previously thought.
Keywords: Balaenidae, gigantism, cervical vertebrae, ear bones, forelimb, phylogeny
Systematic palaeontology
Cetacea Brisson, 1762
Neoceti Fordyce & de Muizon, 2001
Mysticeti Gray, 1864
Balaenidae Gray, 1821
Antwerpibalaena gen. nov.
Derivation of name. Antwerp, after the city
(Antwerpen in Flemish) that lends its name to the harbour area where the fossil was found and which has
long been at the centre of Belgian cetacean research;
balaena, Latin for whale.
Antwerpibalaena liberatlas sp. nov.
Derivation of name. From liber, Latin for free; and
atlas, after the name of the first cervical vertebra. The
latter is unfused in the holotype of the new species.
Holotype. IRSNB M2325, comprising a fragmentary
basicranium, both tympanoperiotics, the right auditory
ossicles, both mandibles, parts of the hyoid apparatus,
the right forelimb, all seven cervical vertebrae, five
thoracic vertebrae, the sternum and several ribs.
Occurrence. The type and only specimen came
from the Kieldrecht Lock (previously known as
Deurganckdoksluis, Port of Antwerp area) on the left
bank of the river Scheldt, north-west of the city of
Antwerp, Belgium (Fig. 1). The specimen derives from
the base of the Oorderen Sands Member (Lillo
Formation), dated to 3.21–2.76 Ma (Piacenzian, late
Pliocene) based on its dinoflagellate cyst assemblage
(Louwye et al. 2004; De Schepper et al. 2009).
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| Consensus tree showing all compatible groups arising from the Bayesian total evidence (molecular þ morphological data) analysis. Numbers next to nodes represent posterior probabilities, values below 50 are not shown. Grey shading within Balaenidae indicates extant species. Drawing of whale by Carl Buell. |
Conclusions:
Antwerpibalaena liberatlas is a new, medium-sized
(9.5–11.9 m) extinct balaenid from the Pliocene of
Belgium. Its well-preserved postcranial remains provide
novel insights into the evolution of extant balaenid anatomy and function, such as the emergence of a fused
neck and paddle-shaped flippers. Its total body length
falls between that of extant right whales and most extinct species, and points to a more complex pattern of
body size evolution than previously thought. The
Pliocene North Sea was home to a disparate balaenid
assemblage, ranging from small species like Balaenella
brachyrhynus to comparative giants like Eubalaena ianitrix. Despite its chequered history, the Belgian Pliocene
fossil record holds great potential to illuminate cetacean
evolution at a time of major global change.
Guillaume Duboys de Lavigerie, Mark Bosselaers, Stijn Goolaerts, Travis Park, Olivier Lambert and Felix G. Marx. 2020. New Pliocene Right Whale from Belgium informs Balaenid Phylogeny and Function. Journal of Systematic Palaeontology. 18(14); 1141-1166. DOI: 10.1080/14772019.2020.1746422
