Table 2 Meristic comparison among B. groenlandica B, stensiöi, Birgeria liui and Birgeria acuminata
New Specimen of Birgeria liui | Holotype of B. liui | B. groenlandica | B. stensiöi | Birgeria acuminata | |
|---|---|---|---|---|---|
Neural arches | ≈ 84 | ? | ≈ 80 | ≈ 80 | ≈ 80 |
Pectoral fin | |||||
Radial ossification | 8 | ? | 10 | 11 | 9–10 |
Lepidotrichia | > 40 | ? | ≈ 40 | 44 | 43 |
Pelvic fin | |||||
Radial ossification | ≈ 17 | ? | 13 | 13 | ? |
Lepidotrichia | ≈ 40 | ? | 50 | 50–60 | > 60 |
Dorsal fin | |||||
Axonost | 13 | 14 | 13-15 | 3 (?) | 17 |
Baseost | ≈ 38 | > 24 | 30 | 24 (?) | 21 |
Axonost plate | Present | ? | Present | Present | ? |
Distal radial ossification | Absent | Absent | 3–4 | Absent | Absent |
Lepidotrichia | ≈ 115 | > 50 | 53–57 | 55–60 | > 40 |
Fulcra | 5 | ? | Absent | Absent | ? |
Anal fin | |||||
Axonost | 16 + 8 | 14 + 7 | 17 + 5 | 17 + 7 | 17 + 4 |
Baseost | ≈ 20 | > 3 | 10 | 6–8 | 4 |
Axonost plate | Present | Present | Present | Present | Present |
Lepidotrichia | ≈ 110 | >50 | 60-62 | 53 | ≈ 80 |
Fulcra | 6 | ? | absent | ≥ 2 | ? |
Caudal fin | |||||
Lepidotrichia | > 140 | > 60 | 65 | 37 | > 95 |
Fulcra | > 10; 3 | > 12; 2–3 | 14; 0 | 14; 2–3 | 15 |
Intersecting angle of the dorsal and ventral margins of the caudal fin | 76° | 70° | 40° | 65° | 73° |