Ceratonereis Kinberg, 1865

Key to atokes of American Ceratonereis Kinberg, 1865 View in CoL

(Modified from de León-González 2009) 1

1. Dorsal ligules reducing greatly their size and disappearing from middle chaetigers.................................. 2

- Dorsal ligules present throughout body, often reducing progressively their size toward posterior chaetigers.............. 3

2. Blades of notopodial and neuropodial falcigers, in middle and posterior body, with nearly rounded distal tip ( i.e. unidentate).................... Ceratonereis excisa View in CoL ( Grube & Müller in Grube, 1873) ( Santa Catarina Island, Santa Catarina, Brazil) 2

- Blades of both notopodial and neuropodial falcigers in middle and posterior body with a small tooth at the distal tip ( i.e. bidentate)............... Ceratonereis longicirrata Perkins, 1980 View in CoL (Hutchingson Island, Florida, United States of America)

3. Blades of both notopodial and neuropodial falcigers, in middle and posterior body, with a small tooth at the distal tip ( i.e. bidentate)........................................................................................... 4

- Blades of notopodial and neuropodial falcigers, from middle and posterior body, with rounded distal tip ( i.e. unidentate)... 6

4. Jaws broad, teeth coarse............................................................................... 5

- Jaws narrow, teeth minute.......................... Ceratonereis nancyae View in CoL n. sp. (Buenavista, Quintana Roo, Mexico)

5. Antennae lanceolate; dorsal ligules in chaetigers 10–13 shorter than the half of median ligules..................................................................................... Ceratonereis mirabilis Kinberg, 1865 View in CoL (9ºS Brazil)

- Antennae subulate; dorsal ligules in chaetigers 10–13 longer than the half of median ligules.................................................................................. Ceratonereis gracilis ( Webster, 1884) reinst. ( Bermuda)

6. Both dorsal and ventral ligules subequal throughout body................................................................................... Ceratonereis singularis Treadwell, 1929 View in CoL (San Jose Island, Baja California Sur, Mexico)

- Both dorsal and ventral ligules greatly diminishing their size toward posterior end.................................................................................. Ceratonereis maya View in CoL n. sp. (Contoy Island, Quintana Roo, Mexico)