Bothrioiepis yeungae, Johanson, 1998

Johanson, Zerina, 1998, The Upper Devonian fish Bothriolepis (Placodermi: Antiarchi) from near Canowindra, New South Wales, Australia, Records of the Australian Museum 50 (3), pp. 315-348 : 318-323

Bothrioiepis yeungae n.sp.

Figs. 3-10 , lIC,J, 13-18

Bothriolepis sp. Conolly, 1965: 56.

Bothriolepis sp. Gilbert-Tomlinson, 1965: 208.

Bothriolepis sp. Long, 1982: 66.

Bothriolepis sp. Young, 1993: 251.

Bothriolepis sp. Iohanson & Ahlberg, 1997: 39.

Bothriolepis sp. Ahlberg & Iohanson, 1997: 653.

Bothriolepis sp. Iohanson, 1997a: 213.

Bothriolepis sp. Iohanson, 1997b: 201.

Holotype. AM F101247 , external head and trunkshield, left pectoral fin in dorsal view ( Figs. 3A , lOG).

Other material. AM F99692 , AM F100838-844, AM F100885-904, AM FI01232-273, 101275-277, AM F101608, AM FI01609, AM F. I02397 -399, AM F105479-540, representing internal and external views of the head and trunkshield as well as disarticulated plates. Proportions given below are taken from specimens used in PCA, including (AM Fl01247 and 105479-540). Measurements available from the author upon request.

Locality and horizon. 10 km SW of Canowindra, NSW , Australia, along the road to Gooloogong (33°35'56"S 148°33'59" E). The fossil fish layer is located within the Mandagery Sandstone ( Upper Devonian ) .

Etymology. The species is named after Monica Yeung, Gondwana Dreaming Pty Ltd, Canberra, for her invaluable contributions to the Canowindra project.

Diagnosis. Differs from all other Bothriolepis in possessing a reduced anterior process of the submarginal, separated from the posterior process of the submarginal by a wide, open notch. Characterised by: Preorbital recess trifid. Oval attachment area for prelateral on the lateral plate small, laterally oriented, separated from a strongly developed, horizontal anterior submarginal attachment on the lateral plate. Posterior submarginal attachment on lateral plate ending at posterior margin of spiracular groove. Pineal plate with reduced posterolateral corners. Postlevator cristae of anterior median dorsal plate sharply defined and short, often dissociated from the postlevator thickenings and situated in the levator fossa. Crista transversalis interna anterior on anterior ventrolateral plate obliquely oriented. Cv2 and Mml plates do not overlap on mesial margin of pectoral fin.

Remarks. Despite criticisms of quantitative measurements above, the diagnosis illustrates the difficulty in finding a large number of unique qualitative characters to diagnose species of Bothriolepis . However, the unusually low anterior process of the submarginal and the wide notch between this and the posterior submarginal process are present on all individuals of Bothriolepis from the Canowindra type locality.

A large number of specimens of Bothriolepis are available for examination, and the majority are well preserved (although flattened) with articulated plates in the head and trunkshield. The majority of specimens are preserved in life position. Although this appears to be an ideal situation for species description and comparison, it is in fact limiting. Views of the internal surface of the head and trunkshield are present, but less common. The pectoral fin is most frequently preserved attached to the trunkshield so that the articular area on the anterior ventrolateral plate is not generally visible. Flattening of specimens means the medial wall of the pectoral fin is rarely visible, as are the plates comprising the lateral lamina of the trunkshield. These problems were also apparent in description of Remigolepis walkeri from Canowindra ( Johanson, 1997a) .

Figures

Figure 3. Bothriolepis yeungae n.sp. A, AM F.101247, holotype; E, AM F.100901; C, AM F.101271; D, AM F.101272; all dorsal view of head and trunkshield. Scale = 1 cm.

Figure 4. Bothriolepis yeungae n.sp. A, AM F.100891, dorsal view of head and trunkshield; B, AM F.100901, ventral or internal view of head and trunkshield; C, AM F.101241, dorsal view of head and trunkshield; D, AM F.100891, lateral view of head and trunkshield and partial pectoral fin; E, AM F.lO1250, lateral view of head and trunkshield with proximal plates of pectoral fin. Scale = 1 cm.

Figure 10. Bothriolepis yeungae n.sp. A, AM F.100842, internal view of headshield with suborbital plates; E, AM F.100904, internal headshield; C, AM F.100904, detail of right submarginal plate; D, AM F. 100844, internal view of headshield; E,F, AM F. 100891; G, AM F.101247; H, AM F.100802a, all dorsal view of head and trunkshield, except F, lateral view. Scale = 1 cm.