マウソニア科シーラカンスの系統と進化

抄録

Mawsoniids is a well-defined family of Mesozoic coelacanths ranging from the Late Triassic to the Late Cretaceous. They dwelled in marine and freshwater environments, and most species are characterized by the presence of ossified ribs, coarse rugosities of the dermatocranium and cheek bones, spiracular and suboperculum usually absent, and reduction or loss of the descending process of the supratemporal, as well as by a large body size. Although relatively abundant in some localities in South America and Africa, the phylogenetic relationships among the species are still poorly understood. Here, we propose for the first time a species-level phylogeny of the mawsoniids, and we discuss its implications on the evolutionary history of the clade. This evolutionary history can be divided into two main episodes: a Triassic episode that occurred mostly in North America and a Western Gondwanan early Cretaceous episode that occurred mostly on Western Gondwana with a Late Cretaceous European extension. The Jurassic has yielded few mawsoniid remains, except the marine Trachymetopon, whose place in this evolutionary history remains to be understood. Other problematic taxa in this scheme, either for their age or for their phylogenetic relationships, are Parnaibaia and “Mawsonia” lavocati. Lualabaea is closely related, or possibly co-generic with Axelrodichthys. This analysis highlights the rich evolutionary history of this clade, and proposes some biogeographic patterns composed of both vicariant and dispersal events.