Edaphodon bucklandi Agassiz, 1843

Kovalchuk, Oleksandr, Kriwet, Jürgen, Shimada, Kenshu, Ryabokon, Tamara, Barkaszi, Zoltán, Dubikovska, Anastasiia, Anfimova, Galina & Davydenko, Svitozar, 2023, Middle Eocene cartilaginous fishes (Vertebrata: Chondrichthyes) of the Dnieper-Donets Basin, northern Ukraine, Palaeontologia Electronica (a 32) 26 (2), pp. 1-37 : 6

Edaphodon bucklandi Agassiz, 1843

Figure 3

1843 Edaphodon bucklandi ; Agassiz, p. 351- 352, pl. 40d, figs. 1-4, 9-12, 19-24.

1843 Edaphodon eurygnathus ; Agassiz, p. 352.

1848 Edaphodon Bucklandii [sic] Ag.; Giebel,

p. 378.

1848 Edaphodon eurygnathus Ag. ; Giebel,

p. 379.

1850 Edaphodon eurygnathus ; Dixon, p. 111,

pl. 10, figs. 18, 19, 22; pl. 12, fig. 5.

1850 Edaphodon Bucklandi [sic]; Dixon, p. 111, pl. 10, figs. 20, 21.

1861 Edaphodon Bucklandii [sic] Ag.; Rogovich, p. 60, pl. I, figs. 5, 6.

1861 Edaphodon eurygnathus Ag. ; Rogovich,

p. 61, pl. VIII, figs. 18, 19.

1891 Edaphodon bucklandi, Agassiz ; Woodward, p. 80-81.

1901 Edaphodon Bucklandi [sic] Agassiz; Priem, p. 485.

1902 Edaphodon Bucklandi [sic] Agassiz, 1843; Leriche, p. 35, pl. I, fig. 51.

1905 Edaphodon Bucklandi [sic] Agassiz, 1843; Leriche, p. 137-140, figs. 18, 19.

2012 Edaphodon bucklandi Agassiz, 1843 ; Diedrich, p. 19, fig. 14.19.

Material. Three right palatinal fragments, NMNHUG 391/114, 391/138/1-2; one left mandibular fragment, NMNHU-G 391/115, Vyshhorod.

Description. Palatine tooth plates ( Figure 3A–C )

are robust and broad, with a stepped oral surface.

NMNHU-G 391/138/1 bears three tritors, of which the posterior inner one is the largest and broadest

(albeit partly destroyed in its distal part), reaching 12.6 mm in width. It is separated from the anterior inner tritor with a narrow groove and smoothly tapers anteriorly. The outer tritor is elongated and well separated from both inner ones with a deep valley, and its anterior end lies at the level of the middle part of the anterior inner tritor. Two inner tritors are preserved in NMNHU-G 391/114, which is more than twice as large as in NMNHU-G 391/138/ 1. The length of the anterior and posterior inner tritors is 21.7 and 26.6 mm, and their width is 14.3 and 23.6 mm, respectively. The mandibular tooth plate ( Figure 3D ) with a broad symphyseal surface is also robust. The median tritor occupies more than two-thirds of the lingual surface, has irregular oval shape, and is separated from the posterior border of the symphysis with a narrow band. The anterior outer tritor is triangular with rounded edges, and it is much smaller and lies below the median tritor. Numerous vertical tubules are visible at the cross section of both tritors.

Remarks. The specimens from Vyshhorod were assigned to the genus Edaphodon based on the number of tritors on palatine tooth plates (Woodward, 1891; Stahl, 1999; Stahl and Parris, 2004; Cicimurri and Ebersole, 2015). Albeit being partly broken, they are similar in gross morphology (shape, size, and orientation of tritors, morphology of the labial margin) to those of E. bucklandi erected by Agassiz (1843) from the Eocene of England. Rogovich (1861) identified two of the specimens described (NMNHU-G 391/114, 391/ 115) as E. bucklandi , and two others he assigned to another species, E. eurygnathus Agassiz, 1843 . The latter is no longer valid because it was synonymised with E. bucklandi by Woodward (1891:80) as the ‘differences between the palatine teeth of this species and those of the so-called E. eurygnathus are solely due to the imperfect state of preservation of the type specimens of the latter.’ Apart from England, E. bucklandi is recorded from the Paleocene and Eocene of Belgium (Leriche, 1902, 1905; Casier, 1943; Dobbels, 1994), as well as from the Eocene of France (Priem, 1901, 1908; Leriche, 1906), Germany (Giebel, 1848; Diedrich, 2012) and Morocco (Case and Herman, 1973). An Edaphodon fossil, represented by a left mandibular fragment with morphological traits similar to those in E. bucklandi , was also reported from the late Eocene of North America (Parmley and Cicimurri, 2005). It is similar to NMNHU-G 391/ 115 in having a broad, flat symphyseal surface, a large medium tritor, and an anterior outer tritor of similar shape and punctuate surface pattern.

Figures

FIGURE 3. Chimaera (Edaphodon bucklandi) remains from the middle Eocene deposits of Vyshhorod: A-C – palatine fragments NMNHU-G 391/138/1 (A), NMNHU-G 391/114 (B), and NMNHU-G 391/138/2 (C); D – left mandibular fragment NMNHU-G 391/115.