A new small balaenid is described and compared to all fossil and living balaenid taxa. The specimen represents a new genus and species and is named Balaenella brachyrhynus. It was discovered in the Lower Pliocene of Kallo (northwest Antwerp, Belgium) and adds new information on the diversity and evolution of Balaenidae. Based on both comparative morphology and phylogenetic analysis, Balaenella brachyrhynus is morphologically closer to the genus Balaena, including the living Greenland Bowhead whale (B. mysticetus), and two Pliocene species (B. montalionis and B. ricei) from central Italy and the eastern USA. Balaenella brachyrhynus has very short nasals, a short rostrum relative to the total skull length and a horizontal supraoccipital. A cladistic treatment of 81 morphological character states scored for 10 balaenids and nine non-balaenid cetaceans revealed that the other small balaenids generally included in the genus Balaenula (including Balaenula astensis, B. balaenopsis and a Pliocene Balaenula sp. from Japan) are closer to the living genus Eubalaena (the Right whale). As the new skull is so different from the nominal Balaenula species, and as it is more closely related to Balaena than to Eubalaena, it is concluded that a small body size was a common condition in different Balaenidae clades.Key words: Balaenula, Balaenidae, Belgium, Cetacea, Mysticeti, Phylogeny, Pliocene.In zoological textbooks, balaenids are usually regarded as gigantic, slow-swimming Mysticeti (Mammalia, Cetacea) with an arched rostrum and long baleen (Ridgway and Harrison 1985; Berta and Sumich 1999), but it is often forgotten that small and more streamlined forms have flourished during their evolutionary history. Small balaenids are represented by a conspicuous and widespread fossil record. They occur in the Upper Miocene-Lower Pliocene of California (eastern Pacific; Barnes 1977), and in Pliocene sediments of Belgium (north-east Atlantic; Van Beneden 1880, 1878, Italy (central Mediterranean; Trevisan 1941; Pilleri 1987;Bisconti 2000), Japan (western Pacific; Excavation Research Group for the Fukagawa Fossil Whale 1982), and eastern USA (western Atlantic; Whitmore 1994). Despite their worldwide occurrence, only a few species have been described and figured in detail; these are: the Japanese Balaenula sp. (Excavation Research Group for the Fukagawa Fossil Whale 1982), the Italian Balaenula astensis (Trevisan 1941; Pilleri 1987;Bisconti 2000) and, to some extent, the Belgian Balaenula balaenopsis (Van Beneden 1878, 1880.The small balaenids are usually grouped within the genus Balaenula Van Beneden, 1880. Balaenula is based on a fragmentary skull and associated skeleton but unfortunately an unambiguous character-based diagnosis of the genus has been lacking until recently . Abel (1941) re-assessed some Belgian material pertaining to Balaenula and provided a reconstruction of the type skull (Van Beneden did not designate any holotype material). However, some morphological details (such as the dorsal surface of the supraoccipita...

A fossil pygmy right whale (Cetacea, Mysticeti, Neobalaenidae) with exquisitely preserved baleen is described for the first time in the history of cetacean palaeontology, providing a wealth of information about the evolutionary history and palaeobiogeography of Neobalaenidae. This exquisitely preserved specimen is assigned to a new genus and species, Miocaperea pulchra gen. et sp. nov., and differs from Caperea marginata Gray, 1846, the only living taxon currently assigned to Neobalaenidae, in details of the temporal fossa and basicranium. A thorough comparative analysis of the skeleton of M. pulchra gen. et sp. nov. and C. marginata is also provided, and forms the basis of an extensive osteology-based phylogenetic analysis, confirming the placement of M. pulchra gen. et sp. nov. within Neobalaenidae as well as the monophyly of Neobalaenidae and Balaenidae; the phylogenetic results support the validity of the superfamily Balaenoidea. No relationship with Balaenopteroidea was found by the present study, and thus the balaenopterid-like morphological features observed in C. marginata must have resulted from parallel evolution. The presence of M. pulchra gen. et sp. nov. around 2000 km north from the northernmost sightings of C. marginata suggests that different ecological conditions were able to support pygmy right whale populations in what is now Peru, and that subsequent environmental change caused a southern shift in the distribution of the living neobalaenid whales.

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A new eschrichtiid, Eschrichtioides gastaldii gen. nov., comb. nov., is established based on a specimen previously assigned to Balaenoptera gastaldii Portis, 1885. The holotype is from the Early Pliocene of north-east Italy. It represents a fossil mysticete closely related to the living grey whale, Eschrichtius robustus. Comparative morphology and phylogenetic analysis support the monophyly of Eschrichtiidae and Cetotherium-like mysticetes and a sister group relationship between this clade and Balaenopteridae. Eschrichtiid fossils previously described are all from the Pleistocene and Late Pliocene while Eschrichtioides gastaldii is from the Early Pliocene. The recognition of this new eschrichtiid genus suggests that the Mediterranean trophic web of the Early Pliocene was more complex than at present and that the Neogene mysticete family-level biodiversity of the Mediterranean was higher than that currently observed in this basin.

A new basal balaenopterid genus and species, Archaebalaenoptera castriarquati, is described and compared with all the living and fossil members of the family Balaenopteridae and related fossil rorqual-like taxa. It was found in the Lower Pliocene of northern Italy, and is characterized by a supraoccipital with a transversely compressed anterior process, the zygomatic process of the squamosal diverging from the longitudinal axis of the skull, very long nasal bones, and subtle exposition of the parietal on the dorsal wall of the skull. It is primitive in having a maxilla with a long ascending process that is posteriorly unexpanded and round, and a dentary that is straight and not bowed outward, unlike that of living Balaenopteridae. In particular, the discovery of this new genus suggests that, among the early members of Balaenopteridae, the acquisition of the typical sutural pattern shown by maxilla, frontal, parietal and supraoccipital preceded the acquisition of the feeding-related traits that are characteristic of the family. The primitive morphology of the feeding-related structures of A. castriarquati (i.e. the straight dentary and the flat glenoid fossa of the squamosal) suggests that this whale was unable to undertake the intermittent ram feeding typical of Balaenopteridae as efficiently as living members of the family.