Mola alexandrini, Ranzani, 1839

Sawai, Etsuro & Nyegaard, Marianne, 2023, Response to Britz (2022) regarding the validity of the giant sunfish Mola alexandrini (Ranzani, 1834) (Teleostei: Molidae), Zootaxa 5383 (4), pp. 561-574 : 570-571

Validity of Or. alexandrini when interpreted as if there were no holotype

Although we are of the opinion that the PHMA specimen is the holotype of Or. alexandrini and that Ranzani’s (1839a) illustration is broadly representative of the fresh specimen morphology, here we consider Britz’s (2022) argument that “… there is little in Ranzani’s (1839) description of O. alexandrini that would enable one to assign the name to one of the three currently recognized species of Mola .” Specifically, we examine the validity of the proposed status as ‘ species inquirenda ’ using only the information in the description of Or. alexandrini by Ranzani (1839a). The key question is if there is sufficient morphological information without an extant holotype to tie M. alexandrini to Mola sp. A sensu Yoshita et al. (2009).

Key taxonomic characters of large Mola sp. A specimens (confirmed for specimens> 162.5 cm TL) that distinguish them from the other Mola species are as follows: a combination of a head bump, a chin bump and a rounded clavus margin; rectangular body scales;> 17 clavus fin rays (average);> 10 clavus ossicles (average); absence of a smooth band back-fold on the clavus; absence of raised skin wrinkles (craniocaudal direction) on the body behind the pectoral fin ( Sawai et al. 2018; Sawai 2021). As the TL of the holotype of Or. alexandrini exceeds 162.5 cm TL whichever unit of measurement is applied ( Table 1 ), all the above morphological features are relevant for evaluation.

The morphological characters of Or. alexandrini are summarized by Ranzani’s (1839a: foldout table) as “ Corpus oblongum scabrum, in parte postica fere ovatum, colore fusco ac lutescente varium; fronte altissima prominenti; pinnae pectrales in margine posteriori ad basim sinuosae; pinna dorsalis ab extremitate dorsi haud parum distans, analis extremitate ventris insidens, utraque magna apice obtuso, basi fascia rugosa cincta; pinna caudalis brevissima, integra = Habitat in mari adriatico = Tab. 1 P .10. A.15. D.13. ” [The body is oblong, rough, almost oval in the posterior part, of a brownish color and variegated with luster; a very high forehead; pectoral fins at the posterior margin sinuous at the base; the dorsal fin is not a little distant from the extremity of the back, the anal (fin) is inserted at the extremity of the abdomen, both with a large blunt tip, the base surrounded by a wrinkled band; caudal fin very short, complete = It lives in the Adriatic Sea = table 1. 10 pectoral-fin rays. 15 anal-fin rays. 13 dorsal-fin rays.]. Among these characters, ‘a very high forehead’, ‘almost oval in the posterior part’ and ‘caudal fin very short’ are also evident in the illustration of Ranzani (1839a) (see also Sawai et al. 2018: page 149), and among the three Mola species, the only species with these two combined morphological characters (i.e., ‘a very high forehead’ and ‘almost oval in the posterior part’) is Mola sp. A ( Nyegaard et al. 2018; Sawai et al. 2018). While large Atlantic M. mola may also develop a head bump, the clavus margin in large specimens is distinctly scalloped ( Caldera et al. 2020).

Further, nearly 100 years after Ranzani (1839a) published his revision of the family Molidae, Barnard (1935 : fig. 5a–b on page 654; 1947: fig. 7 on plate XXV on page 212) illustrated a large specimen of the genus Mola stranded in South Africa (Sup. Mat. 2_2; the ‘Kommetje specimen’; 6 feet 4 inches = 193 cm). Barnard (1935, 1947, 1948) identified it as Mola alexandrini based on a tracing of Ranzani’s (1839a) illustration, provided to him by a colleague. Barnard (1935: pages 655–656, 658) commented “ This figure c losely resembles the Kommetje Sun-fish, having an evenly rounded tail, and prominent convexities on the throat and the forehead, especially on the latter.” (Sup. Mat. 2_2). He mentioned that these three morphological features (i.e., a head bump, a chin bump, and a rounded clavus margin) distinguished the Kommetje specimen from M. mola . This indicates that information from Ranzani (1839a) alone, without the inspection of the holotype, could be used by others to identify this species.

As only one specimen was used by Ranzani (1839a) in describing Or. alexandrini as a new species, the specimen on which the description and illustration were based can be considered the type specimen itself ( ICZN 1999, Art. 72.5.6.). Even if the actual specimen itself no longer exists, this does not invalidate the designation ( ICZN 1999, Art. 73.1.4. and 74.4.). Where more than one scientific name has been assigned to the same species, the oldest scientific name applies ( ICZN 1999, Art. 72.9.). It follows that Or. alexandrini should be applied as the scientific name for Mola sp. A sensu Yoshita et al. (2009) on the basis of the information in the description by Ranzani (1839a) alone.