Abstract
The family Balaenidae includes two genus and four extant species. Extinct balaenids are known for at least four genus and 10 species. The oldest known record of members of the Balaenidae is known from the early Miocene, but still need more early members of the family to provide better phylogenetic hypotheses. FCCP 1049 from the lower part of the Chippubetsu Formation, Fukagawa Group (3.5–5.2 Ma, Zanclean, early Pliocene) was preliminary described and identified as Balaenula sp. by Furusawa and Kimura in 1982. Later works discussed that FCCP 1049 is different from the genus, and is placed in different clade from Balaenula astensis. The result of our phylogenetic analysis places FCCP 1049 basal to Balaenella brachyrhynus, and is again separated from B. astensis. In this study, FCCP 1049 is re-described and named as Archaeobalaena dosanko gen. et sp. nov. Archaeobalaena dosanko is distinguishable from other balaenids by having a deep promontorial groove of the pars cochlearis of the periotic. Archaeobalaena dosanko can be differentiated from other balaenids, except Morenocetus parvus by having a slender zygomatic process, and posteriorly oriented postorbital process in dorsal view. Archaeobalaena dosanko adds detailed skull, periotic and bulla morphologies for the earlier balaenids.
Highlights
The family Balaenidae includes two genus and four extant species
The type species of the genus Balaenula balaenopsis from Antwerp was established by Van Beneden [9], but the holotype is doubtfully recognized as an individual [1]
Bisconti [8] mentioned that FCCP 1049 is different from Balaenula based on an extended temporal fossa ( p. 47)
Summary
The family Balaenidae includes two genus and four extant species. Extinct balaenids are known for at least four genus and 10 species [1,2,3]. Oldest known nominal species of the members of the Balaenidae is known from the early Miocene of Patagonia, 2 Argentina [1], and its body length was estimated as 4.8–6.2 m [5]. The type species of the genus Balaenula balaenopsis from Antwerp was established by Van Beneden [9], but the holotype is doubtfully recognized as an individual [1]. The second species, Balaenula astensis from the late early Pliocene of Villafranca d’Asti, was established by Trevisan [11] and re-described by Bisconti [8]. Bisconti [8] mentioned that FCCP 1049 is different from Balaenula based on an extended temporal fossa One of the diagnoses for the genus, not having a protruding nuchal crest is not seen on FCCP 1049. To expand diversity and morphological information for understanding the earlier balaenid evolution, we update the identification of FCCP 1049 and its geological age, and re-describe the specimen
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