• Article |

    Growth series of Palaeozoic stem lampreys do not include a filter-feeding larval phase seen in modern lampreys, which suggests that modern lamprey larvae are a poor model of vertebrate ancestry.

    • Tetsuto Miyashita
    • , Robert W. Gess
    •  & Michael I. Coates
  • Article |

    Three-dimensionally preserved fossils of Parmastega aelidae, a newly described tetrapod from the earliest Famennian (Late Devonian) of Russia, provide detailed insights into the morphology and palaeobiology of the earliest tetrapods.

    • Pavel A. Beznosov
    • , Jennifer A. Clack
    •  & Per Erik Ahlberg
  • Letter |

    Jawless fish were recently shown to possess T- and B-like lymphocytes expressing diverse assembled antigen receptors. This study identifies and characterizes lympho-epithelial thymus-like structures at the tips of gill filaments of lamprey larvae, thus providing evidence that the similarities underlying the adaptive immune systems of both types of vertebrate appear to extend to primary lymphoid organs.

    • Baubak Bajoghli
    • , Peng Guo
    •  & Thomas Boehm
  • Letter |

    Müllerian mimics have convergently evolved similar warning colouration because of the advantage of strength in numbers. However, it is not clear if this effect is sufficient to maintain coexistence when competitive exclusion would be expected to favour one mimic at the expense of the others. Here, Müllerian mimicry in catfish is characterized, and it is shown through morphometric and stable isotope analysis that mimics do not occupy identical niches, so are not in direct competition, thus explaining their coexistence.

    • Markos A. Alexandrou
    • , Claudio Oliveira
    •  & Martin I. Taylor
  • Letter |

    One of the steps in the evolution of tetrapod limbs was the loss of the distinctive fringe of fin rays and fin folds found in the fins of fishes. It is now shown that two novel proteins, actinodin 1 and 2, are essential structural components of fin rays and fin folds in zebrafish, and are also encoded in the genomes of other teleost fish and at least one species of shark, but not in tetrapods. It is suggested that the loss of these genes may have contributed to the fin-to-limb transition in tetrapod evolution.

    • Jing Zhang
    • , Purva Wagh
    •  & Marie-Andrée Akimenko