SERRANIDAE, Swainson, 1839

Alvarado-Ortega, Jesús, Cuevas-García, Martha, Melgarejo-Damián, Pilar, Cantalice, Kleyton Magno, Alaniz-Galvan, Abril, Solano-Templos, Gisel & Than-Marchese, Bruno Andrés, 2015, Paleocene fishes from Palenque, Chiapas, southeastern Mexico, Palaeontologia Electronica 10 (14), pp. 1-22 : 10-14

Family “ SERRANIDAE ” Swainson, 1839

Genus and species indeterminate

Referred Material. IGM 4550 (Figure 6), specimen from the División del Norte quarry (= Locality-IGM 3869). This specimen has an estimated standard length of 69 mm and lacks the caudal fin.

Remarks and comparison. IGM 4550 was previously described by Alaniz-Galvan (2011) and temporarily catalogued as JAO 70. At present, additional specimens from both the División del Norte and Belisario Domínguez quarries are being collected. A further analysis of all the above will contribute to an extensive descriptive and taxonomic study of the serranids in the surroundings of Palenque.

The Percomopha series was firstly recognized by Rosen (1973) and recently renamed as Percomorphacea by Wiley and Johnson (2009). Proposed by Stiassny and Moore (1992), the naturalness of the group is based on two shared characteristics: a pelvic fin located below the pectoral fin, and an association between both pectoral and pelvic girdles (including ligamentous attachments, which are hardly preserved in the fossil record). Both characteristics are present in specimen IGM 4550 (Figure 6). A number of other authors ( Johnson and Patterson, 1993; Patterson and Johnson, 1995, p. 4; Wiley and Johnson, 2009) have recognized the occurrence of six or fewer rays in the pelvic fin as an additional diagnostic characteristic of the percomophs.

FIGURE 6. Specimen IGM 4550, a “ Serranidae ” fish from the Paleocene marine strata at División del Norte quarry, Municipality of Palenque, Chiapas, Mexico. Scale bar equals 10 mm. Abbreviations: afr, anal fin ray; afs, anal fin spine; dfr, dorsal fin rays; dfs, dorsal fin spine; mx, maxilla; op, opercle; par, parapophysis (in the vertebra 10); pcfr, pectoral fin rays; pmx, premaxilla; pvb, pelvic bone; pvfr, pelvic fin rays; pvfs, pectoral fin spine; smx, supramaxilla; numbers show the position of the vertebrae.

The relationships among Percomorphacea have been so controversial that the order Perciformes is presently considered an incertae sedis group within this Division ( Wiley and Johnson, 2009). On the other hand, Patterson (1964, p. 466) considers that perciforms were derived from Beryciformes and have a number of distinctive characteristics. One of these characteristics is the reduction of the pelvic fin to one spine and only five rays (Figure 7), an attribute that can be easily observed in IGM 4550.

Moreover, Nelson (2006, p. 341) provided a list of diagnostic characteristics for the suborder Percoidei . Of these features (Figure 6), IGM 4550 exhibits the presence of anterior spines in the dorsal fin (which may be formed by one or two lobes), a ventral edge on the upper jaw only formed by the premaxilla; and vertebral column not associated with epipleurals and epicentral (intermuscular bones). Based upon this context, specimen IGM 4550 is considered a member of the suborder Percoidei .

The suborder Percoidei is considered the most diverse of all Perciformes ( Nelson, 2006) , with about 79 families, which are often diagnosed based on the body and fin shapes and some meristic features such as number of vertebrae, spines and fin rays. After comparing IGM 4550 to all 79 families, it can be inferred that this specimen belongs in the family Serranidae . IGM 4550, as other serranids, shows the following combination of characters (e.g., Nelson, 2006; Smith and Craig, 2007) (Figure 6): 1) The single dorsal fin is separated from the caudal fin; 2) the dorsal fin presents a notch at the middle of its length (in IGM 4550 this notch is formed because the dorsal spine 8 is shorter than the nearest; 3) the vertebral column includes 24 vertebrae. 4) The anal fin formula presents three spines and 6-12 rays (III+6-12) (IGM 4550 exhibits three spines and seven rays). 5) The dorsal fin formula includes 5-10 spines and 11-32 rays (VX+11-32). Although the nine spines of IGM 4550 follow this formula, its ten rays are just below the lower limit of this account; the study of additional specimens will clarify this uncertainty.

Swainson (1839) created the family Serranidae to include the genus Serranus Cuvier, 1817 , and related forms; however, it quickly became a taxonomic "wastebasket group." Gosline (1968) included three subfamilies within Serranidae : Serraninae , Anthiinae , and Epinephelinae , which are mainly characterized by the presence of three spines on the operculum. Smith and Atz (1969) suggested the addition of a fourth serranid group, the subfamily Grammistinae . Although the opercle in IGM 4550 is poorly preserved, an evident spine can be distinguished.

The interrelationships of serranids, an extremely diverse group of basal perciforms, are problematic (e.g., Thomson et al, 1979; Johnson, 1983). Smith and Craig (2007) found no phylogenetic differences between Percoidei , Perciformes and Percomorpha; their results show that “percoids" are scattered all throughout Percomorpha. Although these authors regard the family Serranidae as unnatural, they proved the naturalness of the serranid subgroups by re-ranking them. Their family Epinephelidae includes the “epinephelins” and the “grammistins.” In their analysis, Smith and Craig (2007) found that a number of “serranid” genera are intimately associated with the superfamily Notothenioidea , and that Serraninae , Trachininae, and Anthiinae are closely related to each other and therefore might constitute a natural family placed near the base of the Percomorpha. Considering the observations above and the comparative analysis on the arrangement of supraneurals and support structures of percoid dorsal fins developed by Kendall (1976), it is possible to categorize IGM 4550 as a likely member of the subfamily Serraninae (Figure 7). This Mexican fish presents three supraneurals that occupy the interneural spaces in a one to one order (the first supraneural is in front of the first neural spine and the second supraneural is between neural spines 1 and 2. Its third supraneural and first dorsal pterygiophore occupy the interneural space between neural spines 2 and 3; its first dorsal pterygiophore is robust, with a wide longitudinal section and an articulation with the first two spines of the dorsal fin. In addition, its dorsal pterygiophores 2 and 3 are placed in the next interneural space (between the neural spines 3 and 4). This arrangement is similar to that described in the subfamily Serraninae by Kendall (1976, figure 1).

The record of putative perciforms includes fossils discovered in both Late Cretaceous and Paleogene localities ( Patterson, 1964) (Table 1). The known perciform species to date are Eoserranus hislopi Woodward, 1908 , described from skull and pectoral girdle fragments, from Eocene Lameta (Training Dongargaon), India, a species repeatedly identified as a serranid ( Pondella et al., 2003; Arratia et al, 2004; Taverne, 2010); Proserra- FIGURE 7. Close-up and line drawing of the anterior dorsal region of the body of IGM 4550, a “ Serranidae ” fish from the Paleocene marine strata at División del Norte quarry, Municipality of Palenque, Chiapas, Mexico. Scale bar equals 10 mm. Abbreviations: dfs, dorsal fin spine; dpt, dorsal pterygiophopre; ns, neural spine; sn, supraneurals; numbers show the position of the vertebrae.

nus lundensis ( Davis, 1890) from Paleocene sediments (Danian) from Limhamn, southern Sweden; Prolates heberti ( Priem, 1899) from the Paleocene deposits of Mont Aimé, Chalons-sur-Marle, France; and Prolates dormaalensis ( Casier, 1967) , found in deposits in lower Eocene Dormaal, Belgium. Other species to be considered are the recently

Palaeoperca VIII + I, 8-9 III + 6-8 23(10+ 13) 7?? cte? Rhenanoperca IX-XI +9-10 III+7-9 24-25(9-11?+14-15 7? 0/0/0+2/1+1/ cte 1

IGM 4550 IX+10 III+7 24(10+14) 3 (8-10) 0/0/0+2/1+1/ cte 1

described Nardoichthys francisci Sorbini and Bannikov, 1991 , from the Campanian-Maastrichtian marine deposits near Nardo, Italy; Bannikovperca apula Taverne, 2010 ; Johnsonperca annavaccarii Taverne, 2010 ; and Zorzinperca weverberghi Taverne, 2010 . Some additional fossils described by Arratia et al. (2004), Indiaichthys bamanborensis and "Percomorpha indet.", have been collected from the Late Cretaceous-Paleocene deposits of the Deccan Plateau, near Bamanbor, India. Bannikov and Carnevale (2007) described a perciform species from the Eocene of Monte Bolca, Italy, as Jimtylerius temnopterusa (including some specimens previously described as Dules temnopterus (Agassiz, 1836) , and considered as belonging to the family Scianidae ). Finally, the incomplete perciform specimens collected in the Maastrichtian deposits of Saldeño, Province of Mendoza, Argentina, were identified as Saldenioicthhys remotus López-Arbarello et al., 2003 , and "Undeterminated Acanthomorpa." Other three Middle Eocene perciformes are known from the freshwater deposits of Messel, including Amphiperca multiformes Weitzel, 1933 ; Palaeoperca proxima Micklich, 1978 ; and Rhenanoperca minuta Gaudant and Micklich, 1990 .

Table 1 compares all fossils referred above and specimen IGM 4550. In many cases, the anatomy of these fossils is only partially known; however, it is noticeable that IGM 4550 resembles Prolates , Proserranus , Jimtylerius, Indiaichthys , and Rhenanoperca in that they all exhibit ctenoid scales, 24 total vertebrae (including 10 abdominal and 14 caudal, a condition considered as primitive among “percoids”; e.g., Gosline 1968, 1971; Johnson, 1984; Bannikov and Carnevale, 2009). In Palaeoperca the dorsal fin include two lobes clearly separated from each other; hence, this German species is clearly different from IGM 4550 that has a continuous dorsal fin. Among these fishes, IGM 4550, Rhenanoperca , Prolates , and Proserranus share the same dorsal fin pattern, nine spines and 10 rays forming a single and continuous dorsal fin. Although in the last two nominal genera the FIGURE 8. Specimen IGM 4551, Pycnodus sp. from the Paleocene marine strata of División del Norte quarry, Municipality of Palenque, Chiapas, Mexico. Scale bar equals 20 mm. Abbreviations: cls, cloacal scale; cp, caudal peduncle; dmfe, dermocranial fenestra; drs, dorsal ridge scales; ms, modified bar-like scales; papr, parietal process; partt, prearticular teeth; vks, ventral keel scales; vt, vomer teeth.

composition of the anal fin remains uncertain; the pattern III+7 (spine + soft rays) found in the anal fin of IGM 4550 is into the range of Rhenanoperca (III+7-9).

Although the predorsal formula of IGM 4550 (0/0/0+2/1+1/) has been previously documented in Prolates, Proserranu s, Amphiperca , Palaeoperca , Rhenanoperca , and probably in Indiaichthys; the presence of one premaxilla is documented only IGM 4550, Prolates , Rhenanoperca , and Indiaichthys. Additionally, it is noteworthy the fact that the number of abdominal vertebrae with parapophysis is still an undocumented characteristic in some of the fossils here included. In this context, IGM 4550 shows an attribute never documented in any of the other fossils, only the last three abdominal vertebra (8-10) presents a parapophysis; in contrast, this structure of the bdominal centra is developed in two centra of Indiaichthtys and Amphiperca ( Micklich, 2008, figures 1 and 2) and at least in five of the other fossil fishes previously discussed in this work (Table 1). Despite this observation, a full anatomical analysis of IGM 4550 and similar taxa (including Indiaicthys, Rhenanoperca , Amphiperca , and Palaeoperca ) is required before naming a possibly new species.