Chaetodon ficheuri, ARAMBOURG, 1927

Carnevale, Giorgio, 2006, Morphology and biology of the Miocene butterflyfish Chaetodon ficheuri (Teleostei: Chaetodontidae), Zoological Journal of the Linnean Society 146 (2), pp. 251-267 : 252-254

CHAETODON FICHEURI ARAMBOURG, 1927 ( FIGS 2–5 )

1927 Chaetodon ficheuri Arambourg , pp. 154–156, pl. 28.

Material examined: Holotype: MNHN ORA89, complete articulated skeleton of 157 mm SL. Messinian, Saint-Denis du Sig, Algeria . Paratypes: MNHN ORA 46, ORA 47, Messinian, Raz-el-Aïn, Algeria. Referred specimens: MNHN ORA 169, Messinian, Raz-el-Aïn, Algeria; MHNH ORA 1435, Messinian, Les Planteurs, Algeria; MNHN ORA 1613, Messinian, St. Eugène , Algeria .

Diagnosis (amended): As for the subgenus.

Etymology: Named after the geologist Professor Doyen E. Ficheur.

Remarks: Anatomical analysis of the specimens revealed a number of characters that strongly support the inclusion of this species in the family Chaetodontidae , and, more precisely, in the genus Chaetodon , including: general physiognomy of the body, squamation pattern, presence of high supraoccipital crest, number of vertebrae, structure and composition of caudal fin and skeleton, predorsal formula, pelvic fin spine articulation, lateral line morphology, frontals sutured to the epiotics, second infraorbital bone excluded from the orbit and presence of a medially incomplete supracleithral lateral line canal ( Regan, 1913; Ahl, 1923; Nalbant, 1974; Burgess, 1978; Mok & Shen, 1983; Johnson, 1984; Mok & Chang, 1986; Blum, 1988; Ferry-Graham, Wainwright & Bellwood, 2001a; Smith et al., 2003). Among chaetodontids, the genus Chaetodon is by far the most speciose, with about 90 species recognized at present. This genus has been subdivided in many subgenera (see Burgess, 1978; Blum, 1988). According to the recent phylogenetic analysis performed by Smith et al. (2003), the genus Chaetodon consists of 11 subgenera and an incertae sedis species ( C. striatus ), formerly considered as belonging to the more basal subgenus Chaetodon (e.g. Blum, 1988). The species of the subgenus Chaetodon (including C. striatus ) inhabit the Atlantic coasts of Africa and North and South America today. The remaining subgenera, Citharoedus , Corallochaetodon , Discochaetodon , Exornator , Gonochaetodon , Lepidochaetodon , Megaprotodon , Rabdophorus , Roaops and Tetrachaetodon are distributed throughout the Indo-Pacific region. Chaetodon ficheuri does not belong to any of the living subgenera. The morphology of its first dorsal fin pterygiophore is a key character for the evaluation of its relationships within the genus Chaetodon . As described above, this bone has a dorsoventrally compressed median anterior process possessing two lateral expansions that form a definite groove. A similar structure of the first dorsal pterygiophore characterizes the species of the subgenera Corallochaetodon , Discochaetodon , Gonochaetodon , Megaprotodon , Rabdophorus and Tetrachaetodon , while Citharoedus , Exornator , Lepidochaetodon and Roaops posess a more derived condition of this feature. Chaetodon ficheuri shares many features with Megaprotodon and Rabdophorus , including: posterior face of the mesethmoid extending posterior to the lateral ethmoids, vomerine teeth apparently present, (presumed) possession of primitive jaw morphology and tooth arrangement, a broad ventral arm of the ectopterygoid, six branchiostegal rays and a sequential articulation between first dorsal pterygiophore, supraneurals and supraoccipital crest. However, C. ficheuri apparently has a solid, unperforated posterior face of the mesethmoid, which has not been observed in either of these genera, but characterizes Citharoedus , Corallochaetodon and Discochaetodon ( Blum, 1988) . A solid, unperforated posterior face of the mesethmoid is also present in the genera Amphichaetodon , Forcipiger , Hemitaurichthys , Heniochus and Roa . Blum (1988), and Smith et al. (2003) considered this character as primitive, and its presence in Citharoedus , Corallochaetodon and Discochaetodon could be interpreted as a reversal.

The monophyly of Rabdophorus was not recognized, but Blum (1988) found no variation in skeletal anatomy among species placed in this subgenus. But the monophyly of this subgenus has been evidenced by a recent molecular study performed by Littlewood et al. (2004). In contrast, the structure and composition of the subgenus Megaprotodon is well defined and it strongly differs from C. ficheuri in many meristic and osteological characters (see Blum, 1988; Smith et al., 2003). Chaetodon ficheuri is also characterized by a vacant interneural space located between the neural spines of the sixth and the seventh precaudal vertebrae. Blum (1988) suggested that a vacant interneural space between the neural spines of the precaudal vertebrae five and six and eight and nine is present in many higher squamipinnes, such as Chaetodipterus , Drepane , chaetodontids, scatophagids and acanthuroids (in the sense of Tyler et al., 1989). However, based on the radiographs published in Nalbant (1974), it is possible to observe that some chaetodontids are characterized by a pattern similar to that of C. ficheuri . Although a more detailed survey of this character will be necessary, it could be provisionally interpreted as diagnostic, at least at the specific level.

The new subgenus Arambourgchaetodon is presently monotypic and is diagnosed by a unique combination of characters. As discussed above, Smith et al. (2003) proposed a new hypothesis of the relationships of chaetodontids. They based their analysis on a set of characters previously recognized by Blum (1988), plus some other features derived from the study of soft anatomy, mainly concerning the sensory apparatus (see also Webb & Smith, 2000). Unfortunately, many of these characters can be observed only on extant taxa. In addition, some of the characters originally discussed by Blum (1988) refer to features that are not observable on the specimens due to the quality of preservation. Because of this, in the present state of knowledge of this material, it is not possible to assign C. (Arambourgchaetodon) ficheuri to a more precise position in the chaetodontid phylogeny. This species represents the only member of a new separate subgenus that should be included in the large clade formed by the Indo-Pacific subgenera of the genus Chaetodon .

Distribution: This taxon is known only from the Chelif Basin, north-western Algeria, with a stratigraphical range restricted to the early Messinian.

Figures

Figure 2. Chaetodon (Arambourgchaetodon) ficheuri Arambourg (1927). A, holotype, MNHN ORA89. B, C, MNHN ORA1613. D, holotype, MNHN ORA89. Scale bar 20 mm.

Figure 3. Chaetodon (Arambourgchaetodon) ficheuri Arambourg, 1927. A, paratype, MNHN ORA46. B, paratype, MNHN ORA47. C, MNHN ORA1435. D, paratype, MNHN ORA46. Scale bar 20 mm.

Figure 4. Chaetodon (Arambourgchaetodon) ficheuri Arambourg, 1927, reconstruction of the head, left lateral view. Abbreviations: aa, angulo-articular; d, dentary; dsp, dermosphenotic; ecp, ectopterygoid; enp, endopterygoid; epo, epioccipital; fr, frontal; h, hyomandibula; io, infraorbital bones; iop, interopercle; l, lacrimal; le, lateral ethmoid; me, mesethmoid; mtp, metapterygoid; mx, maxilla; n, nasal; op, opercle; pa, parietal; pal, palatine; pmx, premaxilla; pop, preopercle; pto, pterotic; pts, pterosphenoid; q, quadrate; soc, supraoccipital; sop, subopercle; sym, symplectic.

Figure 5. Chaetodon (Arambourgchaetodon) ficheuri Arambourg, 1927. A, holotype, MNHN ORA89, urohyal, left lateral view. Scale bar 5 mm. B, holotype, MNHN ORA89, particular of the gill rakers, left lateral view. Scale bar 1 mm. C, holotype, MNHN ORA89, supracleithrum, left medial view. Scale bar 3 mm. D, holotype, MNHN ORA89, reconstruction of the caudal skeleton, left lateral view. Scale bar 5 mm. E, paratype, MNHN ORA46, supraneurals and first dorsal pterygiophore, right lateral view. Scale bar 5 mm. Abbreviations: ep, epural; hyp, hypural; ns, neural spine; phy, parhypural; pt, pterygiophore; sn, supraneural; soc, supraoccipital; un, uroneural.