Phylogenetic relationship of catshark species of the genus Scyliorhinus (Chondrichthyes, Carcharhiniformes, Scyliorhinidae) based on comparative morphology

The genus Scyliorhinus is part of the family Scyliorhinidae, the most diverse family of sharks and of the subfamily Scyliorhininae along with Cephaloscyllium and Poroderma. This study reviews the phylogenetic relationships of species of Scyliorhinus in the subfamily Scyliorhininae. Specimens of all Scyliorhinus species were examined as well as specimens of four of the 18 species of Cephaloscyllium, two species of Poroderma, representatives of almost all other catshark (scyliorhinid) genera and one proscylliid (Proscyllium habereri). A detailed morphological study, including external and internal morphology, morphometry and meristic data, was performed. From this study, a total of 84 morphological characters were compiled into a data matrix. Parsimony analysis was employed to generate hypotheses of phylogenetic relationships using the TNT 1.1. Proscyllium habereri was used to root the cladogram. The phylogenetic analysis, based on implied weighting (k = 3; 300 replications and 100 trees saved per replication), resulted in three equally most parsimonious cladograms with 233 steps, with a CI of 0.37 and an RI of 0.69. The monophyly of the subfamily Scyliorhininae is supported as well as of the genus Scyliorhinus, which is proposed to be the sister group of Cephaloscyllium. The phylogenetic relationships amongst Scyliorhinus species are presented for the first time.


Introduction
Contrasting hypotheses on the classification of catsharks are widespread in literature and divide opinions of many authors (e.g. White 1936White , 1937Compagno 1973Compagno , 1988aMaisey 1984;Nakaya 1975;Iglésias et al. 2005;Human et al. 2006;Naylor et al. 2005Naylor et al. , 2012aNelson et al. 2016;Weigmann 2016;Weigmann et al. 2018). On the basis of morphological data, Compagno (1988a) proposed that the family Scyliorhinidae is composed of 17 genera, following the traditional arrangement for the group (Nakaya 1975;Springer 1979). Posteriorly, Iglésias et al. (2005), analysing molecular data, hypothesised that the family Scyliorhinidae is paraphyletic and proposed the re-allo-cation of 11 catshark genera to the family Pentanchidae, elevated in rank from subfamily (Compagno 1988a). According to Iglésias et al. (2005), both families could be morphologically distinguished by the presence/absence of the supraorbital crest on the neurocranium.
Although the paraphyly of Scyliorhinidae has been corroborated by later works (Human et al. 2006;Naylor et al. 2012aNaylor et al. , 2012b, recent molecular analysis, including a larger sample of taxa, recovered three different paraphyletic lineages of catsharks instead of two and species of Parmaturus were placed in distinct clades (Naylor et al. 2012a(Naylor et al. , 2012b. No cladistic analysis considering morphological data has been performed to elucidate the phylogenetic relationships of catshark species and enlarge our knowledge about the evolution and distribution of morphological characters, such as the supraorbital crest. Thus, we decided to adopt here Scyliorhinidae sensu lato (Compagno 1988a;Weigmann et al. 2018) until a more extensive evaluation of morphological characters is done, thus providing a better definition for Scyliorhinidae sensu stricto and Pentanchidae (Nelson et al. 2016). Compagno (1988a) united the genera Scyliorhinus, Cephaloscyllium and Poroderma in the subfamily Scyliorhininae, following Gill (1862) and on the basis of muscle and neurocranial characters. Herman et al. (1990) proposed the same arrangement, based on dental characters. Later, studies using molecular data corroborated the monophyly of the subfamily (Iglésias et al. 2005;Human et al. 2006;Naylor et al. 2012aNaylor et al. , 2012b, although divergences in phylogenetic relationships amongst its taxa have been observed between morphological and molecular data (cf. Compagno 1988a;Naylor et al. 2012aNaylor et al. , 2012b. Doubts concerning the monophyly of the genus Scyliorhinus are found in many works and focus mainly on the relationships amongst S. canicula and its congeners (Springer 1966(Springer , 1979Compagno 1988a). Scyliorhinus canicula presents unique characteristics in the nasoral region, such as the presence of nasoral grooves and anterior nasal flaps very close to each other. Similar features are also found in the catshark genera Atelomycterus and Haploblepharus (Compagno 1988a). These differences would be, according to Springer (1979), sufficiently great and unique to guarantee the allocation of the other species of Scyliorhinus to a distinct genus, as was proposed by Jordan & Evermann (1896) and Danois (1913). Compagno (1988a) even suggested the adoption of the name Betascyllium Leigh-Sharpe, 1926, if this new arrangement should prove to be necessary. Bell (1993) pointed out the importance of cautiously analysing the characters of the nasoral region and examining a representative number of taxa to better comprehend the evolution of these characters amongst scyliorhinids.
Scyliorhinus presents a unique configuration of the labial furrows comprised of the absence of an upper furrow concomitant with the presence of a narrow lower furrow (Compagno 1988a). The presence of a projecting flap ventral to and covering the lower labial furrow, cited by some authors as a reliable character to identify species belonging to Scyliorhinus (Bigelow and Schroeder 1948;Springer 1966Springer , 1979, was not considered as synapomorphy for the genus by Compagno (1988a). Yet, according to some authors (Springer 1979;Compagno 1988a), the labial furrows observed in Poroderma and in some species of Cephaloscyllium are poorly developed or absent and could be easily confused with the configuration present in Scyliorhinus species (Compagno 1988a).
Detailed descriptions of all Scyliorhinus species, mainly based on external morphology, neurocranium and claspers, were provided in the generic revision of Soares and de Carvalho (2019). The morphological characters raised and analysed in that study, as well as additional morphological characters and broader comparisons with other scyliorhinid and proscyllid genera, are included in the present paper, which aims to provide a phylogenetic hypothesis amongst scyliorhinine species. As mentioned, the most recent phylogenetic hypotheses to infer relationships amongst catsharks are based on molecular evidence (Iglésias et al. 2005;Human et al. 2006;Naylor et al. 2012aNaylor et al. , 2012b; we set out to provide a phylogenetical appraisal, based on a renewed examination of morphological characters. The main objective of the present study is to clarify the phylogenetic significance of the interspecific morphological variation in Scyliorhinus and shed light on the relationships amongst its species and other scyliorhinines.

Selection of taxa
Thirty-five taxa were included as terminals in the phylogenetic analysis. Species representing the three genera assigned to the Scyliorhininae by Compagno (1988a) were included. Specimens of all 16 valid species of Scyliorhinus were examined (Soares and de Carvalho 2019) and, amongst these, 41 specimens were dissected for anatomical investigation corresponding to 14 species of this genus. Specimens of S. comoroensis and S. garmani were not dissected due to the lack of available material for study. Data on meristics, external morphology and internal anatomy of S. cabofriensis, S. haeckelii and S. ugoi were extracted from Soares et al. (2015Soares et al. ( , 2016. Specimens of the other genera of the subfamily Scyliorhininae were examined and dissected, including four of the 18 species of Cephaloscyllium and the two species of Poroderma. For comparative taxa, we examined Proscyllium habereri (family Proscylliidae) and other representatives of Scyliorhinidae sensu lato (Table 1). Specimens of Bythaelurus were not available for dissection and not included in the analysis. The other genus not included here, Pentanchus, is only known from two specimens; one is the holotype of P. profundicolus (USNM 70260;in poor preservational condition) and the other is a specimen cited by Nakaya and Séret (2000) (MNHN 1999-0270) that could not be found. In any case, Pentanchus may not be valid (Compagno 1988a). All material examined and collection data are listed in Appendix 1.

Specimen preparation and characters examined
This study was based on the examination of 84 morphological characters (79 qualitative and five quantitative) that included external morphology, branchiomeric and hypobranchial cranial muscles, clasper morphology, dermal denticles and skeleton. External morphological characters were observed directly or with the aid of a stereomicroscope. Anatomical preparation was performed through manual dissections. For the examination of clasper anato- Table 1. List of species examined (except Scyliorhinus), data available for each species and institutions where the material is deposited. Abbreviations for institutions follow Sabaj (2016). my, the left clasper was chosen to study the external morphology and the right clasper for the internal anatomy. Neurocrania and musculature of adult specimens were examined through dissection. Skin samples were taken for examination of dermal denticles from the right side of the body above the pectoral fin, below the origin of the first dorsal fin and below the insertion of the second dorsal fin. Dermal denticles were photographed using scanning electron microscopes (DSM 940 and ZEISS SIGMA VP), housed in the Departamento de Zoologia of the Universidade de São Paulo. Data of intestinal valves, tooth and vertebral counts were obtained directly from the examined specimens or taken from Compagno (1988a) and other works Stevens 1993a, 1993b;Last et al. 1999;Human 2006aHuman , 2006bHuman , 2007Gledhill et al. 2008;Sato et al. 2008;Nakaya et al. 2013).
Radiographs were taken in the Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo (FMVZ-USP) and in the radiology facilities of the following institutions: BMNH, HUMZ, MCZ, NRM, NSMT, USNM and ZMUC (according to Sabaj, 2016). Counts of monospondylous and diplospondylous vertebrae were based on Compagno (1988a). The vertebral centra present in the transition zone between monospondylous and diplospondylous vertebrae is generally smaller than the last monospondylous centrum and larger than the diplospondylous one and is included in the counts of monospondylous vertebrae.
Character descriptions, related to meristic data, are presented first, followed by characters of external morphology, myology, skeleton and clasper. Skeletal characters are grouped into character complexes, such as neurocranium, jaws, hyoid and gill arches and pectoral girdle. The number preceding each character in the description corresponds to its number presented in the character matrix. A brief summary of each character and its states is followed by its recovered consistency and retention indices (CI and RI, respectively) which reflect their ACCTRAN optimisations (chosen because it maximises initial homology hypotheses). Multistate qualitative characters (6, 22, 43 and 49) and quantitative characters (1-5) were analysed as ordered.
Characters were illustrated with photographs and schematic drawings made from digital photographs. Photographs were taken with a digital camera (Canon Power Shot SX610 HS). Characters and their states are indicated by arrows and numbers in the figures. Figures were digitised and edited with the aid of Adobe Photoshop CS6. Whenever a character is described in the text for a genus without a species citation, that citation refers only to the species examined in the present study and does not imply that the character is present in all congeners.

Phylogenetic procedures
Hypotheses of phylogenetic relationships were proposed using the cladistic method formalised by Hennig (1950Hennig ( , 1965Hennig ( , 1966 and operationally detailed in other works (Farris 1969;Nelson and Platnick 1981;Goloboff 1993Goloboff , 1995Goloboff , 1999Goloboff et al. 2006. Qualitative and quantitative characters were considered in the analysis; values for meristic data were normalised and concatenated with the other characters (Goloboff et al. 2006). Character polarity was determined by outgroup comparison (Nixon and Carpenter 1993); the outgroups are composed of Proscyllium habereri (Proscylliidae) and taxa from the subfamilies Atelomycterinae, Pentanchinae and Schroederichthyinae. Proscyllium habereri was chosen to root the cladogram, as it was recovered as closely related to scyliorhinids in previous studies (Compagno 1988a;Human et al. 2006;. The data matrix (Appendix 2) was assembled and analysed with the aid of TNT 1.1 (Goloboff et al. 2003. Parsimony analysis was performed with implied weighting (k = 3) and the 'Traditional Search' option, using the TBR (tree bisection reconnection) algorithm, with 500 replications and 100 trees retained per replica. A strict consensus cladogram was used to summarise the equally most-parsimonious hypotheses obtained from the different topologies yielded by the analysis. Tree edition was performed with the aid of Figtree version 1.4.3 and Adobe Photoshop CS6.
CI and RI values and synapomorphies of the various nodes were obtained from the set of equally most-parsimonious trees. Relative Bremer support was calculated for each clade using TBR and retaining suboptimal trees by seven steps. Missing entries were used to represent two different instances where characters could not be determined: (1) lack of appropriate study material; and (2) inapplicable character state. For Scyliorhinus comoroensis and S. garmani, it was not possible to extract information on internal anatomical characters (e.g. musculature, neurocranium). Adult males of the terminal taxa Cephaloscyllium isabella, C. umbratile, C. variegatum and Scyliorhinus garmani were not available for dissection and, thus, claspers were not examined for these species. Autapomorphies were not included in the phylogenetic analysis, but are detailed in the section 'Non-informative characters'.
The section 'Description and character analysis' presents the description of each character, its variation within the subfamily Scyliorhininae and other taxa of Scyliorhinidae. Character optimisation and character transformations are presented in Appendices 4 and 5, respectively.

Character descriptions and analysis
Meristics 1 Counts of monospondylous vertebrae: minimum = 28; maximum = 54. (CI = 26; RI = 43-46). Springer and Garrick (1964) pointed out the relevance of vertebral counts to elucidate phylogenetic relationships in Carcharhinidae and other shark families, stating that the values would increase in less inclusive taxonomic levels. These authors considered only precaudal and caudal vertebral counts. Springer (1966Springer ( , 1979   The anterior nasal flap is a triangular or subrectangular structure and is situated medial to the incurrent aperture and lateral to the excurrent one. This flap can cover partially or entirely the excurrent aperture and posterior nasal flap, which is situated on the posterior border of the excurrent aperture (Compagno 1988a(Compagno , 1999. Scyliorhinines present a nasal flap that entirely covers the excurrent aperture and posterior nasal flap and is separated from the mouth by a short distance (state 0; Fig. 1 7 Distance between anterior nasal flaps: (0) distant by one-half or more of the width of the flap; (1) distant by less than one-half. (CI = 33; RI = 33).
In relation to the distance between anterior nasal flaps, these are separated by one-half or more of the width of the flaps in Cephaloscyllium, Poroderma and Scyliorhinus (state 0; Figs 1-3), except in S. canicula and S. duhamelii. In these species, anterior flaps are separated by a short distance, shorter than one-half of their width, as in Atelomycterus (state 1; Figs 1-3). In the other taxa examined, anterior flaps are separated by a similar to slightly larger distance than the width of the flaps. The presence of a mesonarial crest was observed and described by Compagno (1988b) for Scyliorhinus comoroensis. The same structure was also found in the other Scyliorhinus species, Cephaloscyllium and Schroederichthys (state 1; Figs 1 and 2). In S. stellaris, this crest is well developed and extends beyond the posterior border of the anterior nasal flap; this condition is considered here as an autapomorphy for this species (Soares and de Carvalho 2019). In Poroderma, a nasal barbel is found in the same position as the mesonarial crest (Fig. 2). Compagno (1988a) proposed a hypothesis of homology between the barbel of Poroderma and the mesonarial crest of Scyliorhinus which was followed by Human et al. (2006). This hypothesis is rejected here; the nasal barbel in Poroderma is composed by muscle fibres which overlap the external nasal cartilage, whereas, in Scyliorhinus, the mesonarial crest corresponds to extensions of the external nasal cartilage. Therefore, we considered that Poroderma presents an inconspicuous mesonarial crest as in the other examined taxa (state 0; Fig. 2C).
The presence of a muscular nasal barbel is observed in Poroderma (state 1; Fig. 2C) and its extension varies between the two species of the genus, P. africanum and P. pantherinum. In the latter, the nasal barbel is much longer and reaches the upper lip, while, in the former, it is shorter and distant from the mouth. This barbel originates on the ventromedial surface of each anterior nasal flap and is totally separated from the posterior tip of the nasal flap (Compagno 1988a). Considering other carcharhiniforms, only the genus Furgaleus presents a similar nasal barbel.
In Leptocharias, the lateral portion of the nasal flap is well developed and long, but does not form a muscular barbel. The nasal barbel present in some orectolobiforms (Chiloscyllium, Ginglymostoma, Hemiscyllium, Orectolobus and Stegostoma) originates on the rostral surface, medial and partially anterior to the anterior nasal flap (Compagno 1988a) and has a cartilaginous base (Goto 2001), differing from the condition observed in Poroderma and Furgaleus.
A posterior nasal flap, associated with the excurrent nasal aperture, is present in all scyliorhinines, most scyliorhinids and Proscyllium (state 0; Fig. 2). This flap is absent    In relation to the position of the posterior nasal flap, Scyliorhinus canicula and S. duhamelii present a unique condition, i.e. the posterior nasal flap is anteroposteriorly elongated and laterally situated at the excurrent aperture (state 1; Fig. 3A). In other species of Scyliorhinus and carcharhiniforms, this flap is situated along the posterior margin of the excurrent aperture (state 0; Fig. 2). In orectolobiforms, a posterior nasal flap is also laterally situated at the excurrent aperture (Goto 2001). The similarity to the position of the posterior flap in S. canicula, S. duhamelii and in orectolobiforms may be related to the presence of a nasoral groove (Bell 1993).
A nasoral groove, which links the excurrent aperture and the mouth, is observed only in Scyliorhinus canicula and S. duhamelii, amongst scyliorhinines (state 1; Fig.  3A). Nasoral grooves are also observed in the scyliorhinids, Atelomycterus and Haploblepharus (Fig. 3B, C). White (1937) pointed out that the occurrence of nasoral grooves, as well as the distance of nasal flaps from the mouth, may be directly related to the environment in her Catuloidea (= Scyliorhinidae). However, species that present the same habitats and same geographic range as S. canicula and S. duhamelii (e.g. S. stellaris) lack these structures. Shirai (1996) andde Carvalho (1996) listed and coded the occurrence of nasoral grooves in their analyses, but did not comment on the differences found in the nasoral region of scyliorhinids and orectolobiforms. In carcharhiniforms, such flaps are shallow and wide, distinguishing them from the deep nasoral grooves of orectolobiforms that are flanked by a complex arrangement of flaps and projections. According to Bell (1993), the sporadic occurrence of nasoral grooves and associated features suggest that such structures have evolved independently at least three times in scyliorhinids and once in triakids.  In Scyliorhinus species and Poroderma africanum, there is a projected flap on the upper lip margin that laterally covers the lower labial furrow and its external margin does not extend anteriorly (state 1; Figs 1A, 2A, 3A); this is a unique condition in the family Scyliorhinidae. The presence of this flap was considered a diagnostic character of Scyliorhinus by Springer (1979), Compagno (1988a) and Soares and de Carvalho (2019) and may be related to the position of the upper labial cartilage, which is internal to the preorbitalis muscle anteriorly and ventral and external to the m. adductor mandibulae posteriorly.
In taxa, where both labial furrows are found, there is a difference concerning their configuration. In Poroderma pantherinum, these furrows are narrow and discontinuous and the posterior tip of the upper furrow is ventrally situated at the lower one (state 1; Fig. 2C). The same condition is also found in Parmaturus and Schroederichthys.
The configuration of labial furrows may be related to the presence or absence of a fusion between labial cartilages; taxa, in which the furrows are continuous, also presented fused labial cartilages, whereas the furrows are discontinuous in taxa with separated labial cartilages.
19 Number of upper labial cartilages: (0) two; (1) one. (CI = 50; RI = 92). Compagno (1988a) pointed out that the reduction or loss of labial furrows and flaps may be related to loss or reduc-tion of labial cartilages. Shirai (1992a) divided labial cartilages into four states, according to their number: (1) three cartilages present (two upper and one lower); (2) two cartilages (one upper and one lower); (3) only one upper cartilage present (lower absent); (4) both cartilages absent. In this study, only the number of upper labial cartilages was considered, ranging between one and two. In Scyliorhinus, as well as in Cephaloscyllium and Schroederichthys, only one upper cartilage was observed (state 1; Fig. 4A).
In Proscyllium and the other catsharks, two upper cartilages were found (state 0; Fig. 4B), with the exception of Holohalaelurus, which presents no upper labial cartilage, but only a lower one (an autapomorphy for this genus).
In species of Cephaloscyllium, a postoral groove is found, consisting of a slit extending from the oral commissure by an extension of up to one-fifth of the width of the mouth (state 1; Fig. 2B); the extension of this groove is variable amongst species of this genus. In other taxa examined, this groove is absent (state 0; Figs 1-3). In Holohalaelurus, in which labial furrows are absent as in Cephaloscyllium, no notch or postoral groove is observed (Fig. 1C). The fusion of the pelvic inner margins, known as the pelvic apron and defined by Compagno (1988a), is observed in males of species of Scyliorhinus, covering their claspers (state 0; Fig. 5). In Cephaloscyllium and Poroderma, the pelvic inner margins are fused only at their origin; however, this condition is not considered a true pelvic apron because it has also been observed in females where no claspers are found. This fusion is absent in most other scyliorhinids, except in Asymbolus and Holohalaelurus.
22 Extension of pelvic apron: (0) fusion extending up to one-half the length of pelvic inner margins; (1) fusion extending up to two thirds of the length of pelvic inner margins; (2) pelvic inner margins almost entirely fused. (ordered; CI = 100; RI = 100).
Amongst the taxa presenting the pelvic apron, there is some variation in its extension. In Asymbolus and Holohalaelurus, the pelvic apron may be present only in the proximal portion of the pelvic inner margins, corresponding to less than one-half of the length of the inner margins. Species of Scyliorhinus present a more developed pelvic apron, ranging from up to two thirds of the length of the pelvic inner margins (most of species; Fig. 5A) to almost their entire length (S. canicula, S. capensis, S. duhamelii, S. torazame and S. torrei). In these species, claspers of juveniles are totally concealed ventrally by the pelvic apron and visible only when it is lifted (state 2; Fig. 5B). The more developed pelvic apron, extending up to two thirds of the length of pelvic inner margins, was considered by Soares and de Carvalho (2019) as a synapomorphy for Scyliorhinus species.
23 Origin of the first dorsal fin: (0) closer to the vertical line that passes through the insertion of pelvic fins; (1) closer to the vertical line that passes through the origin of pelvic fins. (CI = 33; RI = 0).
The posteriormost origin of the first dorsal fin is the main character used to diagnose the family Scyliorhinidae (Springer 1979;Compagno 1988a;Compagno et al. 2005;. Most of its genera present the origin of the first dorsal fin well posterior to the vertical line that passes through the origin of the pelvic fins and closer to their insertion, ranging from opposite the insertion to half-length of pelvic inner margins. In general, dorsal fins are more posteriorly situated in males than in females. The exception is observed in Cephalurus and Parmaturus, in which the origin of the first dorsal fin is slightly anterior or opposite to the origin of pelvic fins. In Proscyllium and other carcharhiniforms, the first dorsal fin is completely anterior to pelvic fins and its origin may be opposite to the posterior tip or to the half-length of the pectoral inner margins. According to White (1937) and Nakaya (1975), the relative position of the dorsal fins is more anterior in more derived carcharhiniforms and is a character of great phylogenetic relevance. By this criterion, the Scyliorhinidae would be considered the most basal clade within carcharhiniforms. However, Compagno (1988a) pointed out that this character should be cautiously interpreted and better investigated. Regarding the fossil record and the widespread occurrence amongst diverse groups, the anterior position of the first dorsal fin would be primitive in carcharhiniforms, whereas posterior dorsal fins might be a secondary condition, correlated with a more derived benthic habit (Compagno 1988a).
24 Origin of second dorsal fin: (0) posterior to the vertical line that passes through half-length of anal fin base; (1) anterior to the vertical line that passes through half-length of anal fin base. (CI = 25; RI = 50).
Two conditions were observed concerning the origin of the second dorsal fin: posterior (most scyliorhinids; state 0, Fig. 6) or anterior to the vertical line that passes through half-length of anal fin base (Cephaloscyllium, Cephalurus, Parmaturus and Proscyllium; state 1, Fig. 6).
The crown of the dermal denticles on the dorsolateral surface of the body varies from 'teardrop' to 'trident' shape due to the presence or absence of cusplets lateral to the  principal cusp of the crown. Cusplets are present in most scyliorhinids (state 0; Fig. 7), but absent in Cephalurus, Parmaturus and Schroederichthys (state 1; Fig. 7). According to Reif (1985), a greater number of cusplets and ridges would contribute to drag reduction during swimming, improving hydrodynamics.
26 Extension of ectodermal pits in dorsal surface of the crown denticles: (0) extending through more than half the length of the crown; (1) restricted to anterior portion of the crown (CI = 25; RI = 50).
White (1937) categorised the dermal denticles of elasmobranchs according to the features observed in the crown. According to her, scyliorhinids have dermal denticles with flat crowns presenting incomplete median ridges not extending to the distal tip of the crown (e.g. Scyliorhinus retifer and Schroederichthys bivius) or complete median ridges, extending to the distal tip of the crown (e.g. Atelomycterus spp., Halaelurus burgeri and Parmaturus spp.). We observed that the extension and degree of development of median ridges present variation according to taxa and body region examined. However, the number of ridges varies in a consistent manner, making it possible to separate the dermal denticles into two categories: one or two median ridges present on the dorsal surface of the crown, extending from its base to the distal tip or close to it. In scyliorhinines, Apristurus, Cephalurus, Galeus and Holohalaelurus, only one median ridge, more prominent than lateral ridges, is observed (state 1; Fig. 7). In other scyliorhinids, two prominent median ridges, forming a gutter in between them, are present (state 0; Fig. 7).
The presence of a caudal crest of dermal denticles distinct from the denticles on dorsolateral surfaces and situated on the upper lobe of caudal fin, is found in Figaro, Galeus, Parmaturus and some species of Apristurus (state 1; Fig. 8), varying widely amongst species of these genera. This crest is absent in other taxa examined. In Figaro, a crest of enlarged dermal denticles on the lower lobe of the caudal fin was also observed. The occurrence of a caudal crest of dermal denticles is widely used in taxonomic studies of the family Scyliorhinidae (Linnaeus 1758; Regan 1908;Garman 1913;Bigelow and Schroeder 1948;Springer 1966Springer , 1979), but has never been analysed in a cladistic study until now.
The postorbital musculature is composed of three muscles: m. depressor palpebrae nictitantis, m. levator palpebrae nictitantis and m. retractor palpebrae nictitantis. These muscles are responsible for elevation and depression of the nictitating lower eyelid, which is a diagnostic character for carcharhiniforms. These muscles were found in most of the taxa examined, except in scyliorhinines, in which only the muscles levator palpebrae nictitantis and retractor palpebrae nictitantis are present (state 1; Fig.  9A). The absence of the depressor palpebrae nictitantis in the subfamily Scyliorhininae was already reported by Compagno (1988a) and is one of the characters used by that author to diagnose it. Specimens of Aulohalaelurus labiosus, Scyliorhinus comoroensis and S. garmani were not available for dissection (these taxa are scored with a question mark in the matrix). The presence of m. coracohyoideus composed of two distinct muscle bundles originating in the fascia of the  In Proscyllium and some scyliorhinids, the origin of the muscles coracobranchialis II, III and IV is on the coracoid bar (Apristurus, Asymbolus, Atelomycterus, Cephaloscyllium, Figaro, Galeus, Parmaturus, Poroderma and Scyliorhinus; state 0, Fig. 12A). In other scyliorhinids, these muscles originate from the pericardial membrane, a layer of connective tissue anterior to the coracoid bar and ventral to the heart (Cephalurus, Halaelurus, Haploblepharus, Holohalaelurus and Schroederichthys; state 1, Fig. 12B).
The insertion of the m. coracobranchialis presents the following pattern in the taxa examined: coracobranchialis II, on the medial border of the ceratobranchial II cartilage and anterolateral border hypobranchial II; coracobranchialis III, on the medial border of the ceratobranchial III cartilage and anterolateral border of hypobranchial III; coracobranchialis IV, on the medial border of the ceratobranchial IV cartilage and anterolateral border of hypobranchial IV. Muscle coracobranchialis V presents the same pattern in the taxa examined, originating from the anterolateral borders of the coracoid bar and inserting on the medial border of ceratobranchial V and lateral border of the basibranchial copula.
In scyliorhinines, Atelomycterus and Aulohalaelurus, the rostrum is formed by three rostral cartilages anteriorly united only by connective tissue (state 1; Fig.  13A-D), whereas in other taxa examined, these cartilages are fused anteriorly, sometimes forming or not a rostral node (state 0; Fig. 13E-G). Compagno (1988a) proposed that the absence of fusion between rostral cartilages could be an independently derived and the secondary condition for scyliorhinids and proscylliids based on their proximity to taxa in which the fused condition is present.
The distance between lateral rostral cartilages may vary, positioned medially or laterally to the lateral borders of the anterior fontanelle. In some cases, the lateral rostral cartilages are confluent with the lateral borders of the anterior fontanelle, connected to it through ridges that extend from the base of the rostral cartilages to the border of the fontanelle; this condition was observed in Apristurus, Figaro, Galeus and Parmaturus (state 1; Fig. 13F, G). In other taxa examined, the lateral rostral cartilages are distant from the anterior fontanelle and do not present ridges in between both structures (state 0; Fig. 13).
The distance between the median rostral cartilage and anterior fontanelle varies amongst taxa examined. In scyliorhinines and other taxa examined, the median rostral cartilage and the anterior fontanelle are separated by the internasal space, distant by at least two thirds of the length of the median rostral cartilage (state 0; Fig. 13A). In Cephalurus, Haploblepharus and Holohalaelurus, the anterior border of the anterior fontanelle is adjacent to the base of the medial rostral cartilage, without an internasal space separating them (state 1; Fig. 14). Compagno (1988a) listed the measurement 'distance from the ventral border of the anterior fontanelle to the base of the median rostral cartilage' as a way of measuring the space between these structures.  37 Orientation of nasal capsules: (0) nasal capsules perpendicular to the anteroposterior axis of the neurocranium; (1) nasal capsules oblique. (CI = 50; RI = 0).
In Apristurus and Galeus, the nasal capsules are obliquely orientated to the anteroposterior axis of the neurocranium (state 1; Fig. 15), whereas in the other scyliorhinids, the nasal capsules are orientated perpendicularly and laterally expanded (state 0; Fig. 15).
38 Relative position between nasal apertures: (0) incurrent aperture anterior to excurrent one; (1) nasal apertures at the same level. (CI = 50; RI = 90). The external nasal cartilage, situated anteriorly to the nasal apertures and ventrally to the nasal capsules, may or may not be fused to the anterodorsal portion of the nasal capsules (Goto 2001 40 Degree of development of the subnasal plate: (0) restricted to the medial portion of the nasal capsules and ventral to the internasal septum; (1) laterally expanded and united to the lateral border of the nasal capsule. (CI = 33; RI = 0).
The subnasal plate is the ventral floor of the nasal capsules, generally associated with a cavity posteromedial to the incurrent aperture and covered by a layer of connective tissue (nasal fontanelle of Compagno 1988aCompagno , 1999. In most taxa examined, the subnasal plate is restricted to the medial portion of the nasal capsules and ventral to the internasal septum and the nasal fontanelle occupies the entire region posterior to the excurrent aperture (state 0; Fig. 15). In Apristurus, Galeus and Proscyllium, the subnasal plate is laterally expanded, occupying almost the entire region posterior to the excurrent aperture and the nasal fontanelle is reduced to a narrow strip at the posterior border of the excurrent aperture, divided into two portions (state 1; Fig. 15G). Compagno (1988a) suggested a tendency concerning the enlargement of the subnasal plate in derived taxa and consequent substitution of the nasal fontanelle by cartilage. The anterior fontanelle, the anterodorsal aperture of the neurocranium covered by a layer of connective tissue, presents different shapes amongst species and also varies between sexes (Soares et al. 2015(Soares et al. , 2016. This fontanelle may present a notch or an indentation on its posterior border, the epiphyseal notch to the pineal body, as observed in Atelomycterus, Halaelurus, Holohalaelurus, Schroederichthys and Scyliorhinus (state 1; Figs 13A, C, D, 14) or a straight and continuous border, as in Cephaloscyllium, Poroderma and in the other taxa examined (state 0; Figs 13B, E and G). In Holohalaelurus, this notch is well developed, corresponding to two thirds of the length of the anterior fontanelle (Fig. 14). The occurrence of a supraorbital crest on the neurocranium is widely used for identification and separation of shark genera and families. The presence of this crest is considered primitive for elasmobranchs and its absence secondary in some sharks and rays (Compagno 1988a structure is situated dorsally to the orbits and continuous to pre-and postorbital processes in scyliorhinines, Atelomycterus, Aulohalaelurus, Proscyllium and Schroederichthys (state 1; Fig. 13 A-D). In scyliorhinids of the subfamily Pentanchinae (sensu Compagno, 1988a), the supraorbital crest is absent (state 0; Fig. 13E-G). Iglésias et al. (2005) used the occurrence of this crest to distinguish the families Scyliorhinidae and Pentanchidae (= subfamily Pentanchinae of Compagno 1988a), although these authors did not provide further information about the condition found in other families of carcharhiniforms. According to Compagno (1988a), the loss of the supraorbital crest in Hemigalei-dae, Carcharhinidae and Sphyrnidae may be related to the anterior expansion of the muscle levator palatoquadrati dorsal to the orbital wall and neurocranial roof. However, in scyliorhinids without a crest, the muscle levator palatoquadrati originates in the ventral surface of the postorbital process and is situated entirely posterior to the orbit.
Four foramina are present on the posterior portion of the basal plate: two for the medial internal carotid arteries and two for the lateral stapedial arteries. Compagno (1988a) reported the median position of the foramina of the internal carotid artery on the basal plate in scyliorhinids, proscylliids and Pseudotriakis, but did not propose any distinction between the patterns observed. The distance between these foramina varies widely amongst scyliorhinids. In Cephaloscyllium, Holohalaelurus, Proscyllium, Schroederichthys and Scyliorhinus, foramina to the internal carotid artery are very close to each other and separated by a shorter distance than the distance between the internal carotid and stapedial foramina, which are fused in some cases (state 1; Fig.  15A 44 Relative size of postorbital groove: (0) groove corresponds to more than one-half the height of the hyomandibular facet; (1) groove corresponds to less than one-half the height of the hyomandibular facet. (CI = 33; RI = 0).
The postorbital groove is situated posteriorly to the orbits and ventral to the postorbital processes, limited dorsally by the opisthotic process and ventrally by the hyomandibular facet; the lateral vein of the head passes along this groove (Compagno 1988a). In most scyliorhinids, the postorbital groove corresponds to more than one-half of the height of the hyomandibular facet, resulting in a prominent and laterally visible structure (state 0; Fig.  16A, B). In Apristurus, Aulohalaelurus and Cephalurus, this groove is very narrow and shallow, corresponding to one-third or less of the height of the hyomandibular facet (state 1; Fig. 16C).
The pre-and postorbital processes are laterally expanded from the neurocranial roof, as wide as or wider than the nasal capsules. In most scyliorhinids, the distal tip of the postorbital process has a large fenestra through which passes the infraorbital canal of the lateral line (Compagno 1988a; state 0, Fig. 13). In Apristurus and Schroederichthys, this fenestra is absent. In the latter, the infraorbital canal passes through a bifurcation situated at the distal tip of the postorbital process (Fig. 13C). In Apristurus, the postorbital process is narrow and rod-like, not presenting any bifurcation or fenestra and the infraorbital canal of the lateral line passes posteriorly to it (Fig. 13G).
The palatoquadrate articulates to the neurocranium by ethmopalatine ligaments, which are inserted on the postorbital processes of the palatoquadrates and origi-nate from the orbital notches; these notches are situated between the posteroventral region of the nasal capsules and the preorbital wall. Orbital processes are situated in variable positions in the dorsal border of each antimere of the palatoquadrate, delimitating the extension of palatine and quadrate processes. In most scyliorhinids,  Fig. 17B). As de-scribed by Compagno (1988a), more posterior orbital processes are situated at a greater distance from the orbital notches and connected to them through elongated ethmopalatine ligaments (except in Haploblepharus); this arrangement is probably an adaptation to increase jaw protusibility. In Haploblepharus, a unique condition is found as the ethmopalatine ligaments are short and the articulation occurs directly between orbital processes and notches.  Fig. 17B). In the other taxa examined, the degree of calcification is equal throughout Meckel's cartilage (state 0; Fig. 17A).   Fig. 19), but absent in other scyliorhinids (state 1). In taxa without a thyroid foramen, the duct of the thyroid gland passes anteriorly to the anterior border of the basihyal cartilage. The occurrence of a bifurcation on the anterior border of the basihyal cartilage, anterior to the thyroid foramen and not confluent with it, was observed in Atelomycterus, Halaelurus, Holohalaelurus and Schroederichthys (state 1; Fig. 19B). This bifurcation was reported and illustrated for Schroederichthys chilensis by Leible et al. (1982). In scyliorhinines and other taxa examined, the basihyal cartilage has a smooth and slightly convex anterior border (state 0; Fig. 19A).
Processi rastriformis were observed and illustrated in Squalus acanthias by Marinelli and Strenger (1959) and defined as anteriorly directed cartilaginous projections situated on the internal borders of the cerato-and epibranchial cartilages. Compagno (1988a; fig. 2.7) used the term 'dermal papillae' to refer to short structures without cartilaginous support observed in scyliorhinids, proscylliids and some carcharhinids, distinguishing these from the processi rastriformis found in squaliforms, hexanchiforms and Megachasma pelagios. The presence and distribution of these papillae vary widely in the taxa examined, whereas processi rastriformis sensu strictu were observed only in some taxa in which they occupy specific positions in relation to the gill arches. Processi rastriformis greater than the dermal papillae and situated  only on the anterior surface of the articular region between cerato-and epibranchial cartilages were observed in Asymbolus, Atelomycterus, Halaelurus, Poroderma and Schroederichthys (state 0; Fig. 21). In Cephaloscyllium, Scyliorhinus and other taxa examined, processi rastriformis are absent. The term 'gill rakers' used by Daniel (1934) and Compagno (1988a) is not used here, as the structures observed in elasmobranchs are formed by cartilage, whereas gill rakers of bony fishes have a dermal origin and are, therefore, not homologous to processi rastriformis. Nelson (1970) described macroscopic features, such as shape, distribution and abundance of oropharyngeal denticles in Rhizoprionodon terraenovae. Later, Ciena et al. (2016) and Rangel et al. (2017) described the ultrastructure of oropharyngeal denticles and their disposition amongst dermal papillae in Rhizoprionodon lalandii and Prionace glauca, respectively. In all of these species, the denticles are distributed on the entire ventral surface of the oropharyngeal cavity. Heemstra (1997) observed rows of oropharyngeal denticles greater than the denticles around the fifth ceratobranchial of Mustelus norrisi. Here, we report a different condition for oropharyngeal denticles in Apristurus longicephalus, Cephaloscyllium sufflans, C. variegatum, Halaelurus natalensis and Parmaturus xaniurus (state 1; Fig. 22). Besides the denticles of the ventral surface, rows of denticles, greater than the surrounding ones and similar in shape and size to the dermal denticles of dorsolateral surfaces of the body, were found on the internal surface of gill components (ceratoand/or epibranchial) in these taxa. Two rows parallel to the gill arches and composed of 5 to 13 denticles were observed. In other taxa examined, these denticles were absent (state 0).
The fusion between the dorsal tips of gill arches IV and V, forming a unique plate known as the gill pickax (Shirai 1992a), is observed in many neoselachians, with the exception of some rays (Shirai 1996). Despite the presence of this structure having been listed by Shirai (1992a) as a diagnostic character for modern elasmobranchs (except Heterodontus and Trigonognathus), no mention of its morphological variations was provided. Amongst the taxa examined, we observed some differences regarding the shape of the gill pickax. In Cephaloscyllium and Poroderma, the gill pickax is short and triangular in shape (state 1; Fig. 23B). In Proscyllium and other scyliorhinids, this structure is distally elongated and sling-like (state 0; Fig. 23). In taxa in which a medial projection of the coracoid bar is present, differences concerning its shape and degree of development were observed. In Asymbolus, Apristurus, Atelomycterus, Galeus, Halaelurus, Poroderma and Proscyllium, the medial projection has an anterior border that is slightly convex and not very prominent (state 0; Fig.  24B). In Cephalurus, Cephaloscyllium and Scyliorhinus, the projection is well developed and corresponds to more than twice the lateral portion of the coracoid bar. In these taxa, the medial projection entirely covers the heart ventrally (state 1; Fig. 24A, D).
Lateral processes on the coracoid bar, medial to the articular region between pectoral girdle and fins, were observed in Cephaloscyllium, Halaelurus, Haploblepharus, Schroederichthys and Scyliorhinus (state 0; Fig. 24A, B). The processes observed in scyliorhinids correspond to two thirds of the length or similar in size to the medial projection of the coracoid bar. In the illustrations provided by Silva and de Carvalho (2015), projections similar to the lateral processes are present in Alopias superciliosus (p. 17; fig. 14) and Pseudocarcharias kamoharai (p. 30; fig. 27); the authors briefly mentioned the presence of these processes in the latter species. Leigh-Sharpe (1926b) subdivided the genus Scyliorhinus (as Scyllium) into four 'pseudogenera' based on characters of the external morphology of the claspers, including the distribution of dermal denticles on dorsal surface of the clasper glans. Only two of the four groups proposed (Alphascyllium and Betascyllium) included species currently valid for Scyliorhinus. According to Leigh-Sharpe (1926b), species allocated to Alphascyllium presented claspers totally covered by dermal denticles, whereas in Betascyllium denticles are restricted to certain areas; no further details were provided by the author. In    Soares et al. (2015) described the terminal dermal cover in Scyliorhinus ugoi, which consists in a membrane situated on the posterior tip of the clasper glans, lacking denticles and in contact with the posterior borders of the cover rhipidion and exorhipidion. This structure was illustrated by Springer (1966) in Scyliorhinus torrei (p. 588, fig. 4a) and by Compagno (1988a) in Holohalaelurus cf. punctatus ( fig. 13.14f-g), but they did not propose a name nor a definition for it. A terminal dermal cover is found in most taxa examined (state 0; Fig.  25 Fig. 25).
65 Configuration of the terminal dermal cover: (0) smooth; (1) rough. (CI = 33; RI = 0). Compagno (1988a) described and illustrated the presence of a 'brush-like papillose structure' on the distal tip of the clasper glans of Holohalaelurus cf. punctatus; this structure is here considered the terminal dermal cover (as per Soares et al. 2015). The adjective 'rough' is used as a substitute for 'papillose' by considering that the structure does not present papillae but rugosities. Additionally, we observe that, besides having a different texture, the terminal dermal cover projects posteriorly, corresponding to two-thirds of the clasper glans length in Holohalaelurus spp. A terminal dermal cover with similar texture was also observed in Scyliorhinus canicula and S. capensis (Soares and de Carvalho 2019; state 1, Fig. 25B). In the other taxa examined, this structure is smooth and without rugosities (state 0; Fig. 25).
68 Cover rhipidion: (0) poorly developed; (1) well developed and medially expanded. (CI = 100; RI = 100). Compagno (1988a) pointed out that the condition 'clasper groove closed and covered' would be a primitive character for Carcharhiniformes related to the absence or presence of a poorly developed cover rhipidion on claspers.
He reported the presence of a slightly differentiated and short cover rhipidion, well anterior to the clasper glans, in scyliorhinines, Galeus and Holohalaelurus spp. In this study, we observed some differences amongst scyliorhinines and the other scyliorhinids, regarding the degree of development of the cover rhipidion. In scyliorhinines, Atelomycterus fasciatus and Aulohalaelurus labiosus (Soares 2020), the cover rhipidion is medially expanded and reaches the exorhipidion and is sometimes covered by it anteriorly and both cover the clasper groove (state 1; Fig. 25). In the other taxa examined, the cover rhipidion is nearly straight and restricted to the dorsolateral margin of claspers, lateral to the dorsal terminal 2 cartilage and not covering it (state 0).  Fig. 25). In the other taxa examined, a poorly-developed exorhipidion is observed (state 1) corresponding to a narrow strip restricted to the posterior portion of the ventral terminal 2 cartilage and not reaching the cover rhipidion medially.  A different condition from the one described by Jungersen (1899) concerning the position of the ventral terminal 2 cartilage was observed in Aulohalaelurus labiosus and Poroderma spp. In these species, this cartilage is more posteriorly situated, posterior to the half-length of the ventral terminal 2 cartilage and not attached to the anterior tip of the ventral terminal cartilage (state 1). In the other taxa examined, the ventral terminal 2 cartilage presents the same condition described by Jungersen (1899) (state 0). 81 Extension of the clasper siphon: (0) extending beyond the half distance between the coracoid and cloaca; (1) shorter than the coracoid-cloaca half distance. (CI = 33; RI = 78).
Leigh-Sharpe (1920) proposed the term 'siphon' for 'a sac with extremely muscular walls, situated immediately below the corium of the ventral surface of the abdomen, close to the median line and ending blindly, having no communication with the coelom' (1920, p. 246). Leigh-Sharpe (1924a) proposed a transformation series between Scyliorhinidae and Carcharhinidae, with Triakis as an intermediate link, on the basis of siphon length: Scyliorhinidae presenting a short siphon and slightly anterior to the pelvic girdle and Carcharhinidae with extremely long siphons reaching the insertion of the pectoral fin in some taxa. Gilbert and Gordon (1972) suggested a relationship between siphon extension and reproductive mode, with oviparous sharks presenting short siphons and viviparous sharks long siphons. However, a great variation in siphon length was observed herein amongst scyliorhinids, which are reported as oviparous with several descriptions of egg capsules in literature (Springer 1979;Compagno 1988a;Gomes and de Carvalho 1995;Flammang et al. 2007;Flammang et al. 2008;Castro 2011;Ebert and Stehman 2013;Gordon et al. 2016;Silva and Soares 2017;Soares and de Carvalho 2019). Two conditions were observed in the present study: i) long siphons, extending beyond the coracoid-cloaca half distance; and ii) short siphons, shorter than the coracoid-cloaca half distance. In Proscyllium and most scyliorhinids, the longer condition was observed (state 0; Fig. 28A-C), similar to the siphons of Mustelus and Carcharhinus (Leigh-Sharpe 1924a). Short siphons were observed in scyliorhinines, Apristurus longicephalus, Galeus antillensis and Holohalaelurus regani (state 1; Fig. 28D, E, F).   The presence of transverse bands darker than the background colour over most of the body, known as 'saddles', is widespread amongst catsharks. Gomes et al. (2006), in their re-description of Schroederichthys tenuis, proposed three types of saddles: primary saddles, secondary saddles and subsaddles; these latter are situated ventrally to the lateral line. Primary saddles, more prominent in relation to the background colour, were observed in most species of Scyliorhinus (Soares and de Carvalho 2019; Fig. 29), except in S. duhamelii and S. garmani. In S. torrei, these saddles are found only in juvenile specimens. In S. boa and S. retifer, spots and dark lines, slightly darker than the background colour, are bordering the saddles (Fig. 29B). In Asymbolus spp., Atelomycterus spp., Cephaloscyllium spp., Halaelurus spp., Haploblepharus spp., Proscyllium habereri and Schroederichthys spp., saddles were also observed, varying in number and position (state 0; Fig. 29E). In Apristurus spp., Cephalurus spp., Galeus spp., Holohalaelurus regani, Parmaturus spp., and Poroderma spp., saddles are absent (state 1; Fig. 29F).

Colouration
83 Dark spots: (0) present; (1) absent. (CI = 20; RI = 50). Springer (1979) pointed out the relevance of colouration for identification of Scyliorhinus species to the detriment of other features, such as morphometric data and internal morphology. In Scyliorhinus, we observed some differences amongst species regarding the occurrence of dark spots. Dark spots are present in S. boa, S. cabofriensis, S. canicula (Fig. 29A) A colour pattern, composed of dark stripes running in different directions, was observed in Scyliorhinus retifer (Fig. 29B) and Poroderma africanum (state 1; Fig. 29G), differing from all other scyliorhinid species examined. In Scyliorhinus retifer, stripes form polygons and are bordering saddles, while in Poroderma africanum, stripes are parallel to the anteroposterior axis and do not form saddles, extending throughout the body.

Non-informative (autapomorphic) characters
Anterior nasal flaps in Haploblepharus Bell (1993) described anterior nasal flaps as expanded and medially fused, forming a nasal curtain that covers the upper lip, in Haploblepharus. However, according to our observations, nasal flaps in Haploblepharus (Fig. 3C) are not fused, but present the same point of origin, medially; this pattern is unique amongst carcharhiniforms.
Muscle preorbitalis originating from the posterolateral wall of the nasal capsules The muscle preorbitalis is situated anteriorly to the m. adductor mandibulae and limited posteriorly by the mandibular ramus of the nerve V (Huber et al. 2011). This muscle originates from the posteroventral wall of the nasal capsules and extends to the orbital notch in most taxa examined. In Holohalaelurus regani, a unique condition was observed; m. preorbitalis originates from the posterolateral surface of the nasal capsules. In all other scyliorhinid species, insertion of these muscles is on the muscle adductor mandibulae.
Muscle levator hyomandibulae with undifferentiated muscle fibres Shirai (1992b) described the muscle levator hyomandibulae as united to the m. constrictor hyoideus dorsalis in Carcharhiniformes and separated from it in batoids. In Orectolobiformes and Heterodontus, the muscle levator hyomandibulae is situated internally to the m. constrictor hyoideus dorsalis, with its ventral portion laterally exposed (Goto 2001). In most of the examined taxa, muscle fibres are differentiated in m. levator hyomandibulae, internally to the m. constrictor hyoideus dorsalis, originating on the pterotic process of the neurocranium and inserting in the distal tip of the hyomandibular cartilage. In Apristurus longicephalus, the m. levator hiomandibulae seems to be fused to the m. constrictor hyoideus dorsalis or is absent; the same condition is also observed in Squalus acanthias (Marinelli and Strenger 1959;Huber et al. 2011).
Origin of the muscle coracomandibularis on the lateral borders of the coracoid bar The m. coracomandibularis is dorsally situated to the muscles intermandibularis and interhyoideus, consisting of a median bundle originating from the m. coracoarcualis (most taxa examined) or from the medial surface of the coracoid bar (Apristurus longicephalus; Fig. 11D). According to Shirai (1992b), the first condition is widely distributed amongst neoselachians. Association of the m. coracomandibularis directly with the coracoid bar was reported by Shirai (1992a) for Centroscyllium and Rhina and by Goto (2001) for Brachaelurus, Ginglymostoma and Stegostoma. Shirai (1996) coded in his character matrix the origin of the m. coracomandibularis on the fascia of the m. coracoarcualis for all carcharhiniforms (his character 51), differing from what we observed in Apristurus longicephalus. Shirai (1996) also coded the origin of this muscle on the coracoid bar or pericardial membrane for Heterodontus, Hexanchus, Heptranchias, Squatina, Squaliformes and some rays.

Clasper hooks
In Scyliorhinus torazame, we observed specialised hooks in the claspers forming a row that extends from the beginning of the ventral marginal cartilage to the terminal dermal cover and running along the medial margin of the exorhipidion (Schimidt 1930; Soares and de Carvalho 2019; Fig. 24F). This arrangement is unique amongst the taxa examined.

Phylogenetic reconstruction
The phylogenetic analysis of the data matrix (Appendix 2) including 84 morphological characters (five quantitative and 79 qualitative) and 35 terminal taxa and the use of implied weighting (k = 3) resulted in three equally most-parsimonious trees with 233 steps, CI = 0.37 and RI = 0.69. A strict consensus was generated and is presented in Figure 30 and its analysis is detailed below. The char- acter matrix was divided into two datasets: in Appendix 2, quantitative characters with absolute and normalised values for each terminal are presented, whereas in Appendix 3 only qualitative characters are included. Character listings for clades numbered in Figure 30 are summarised in Appendix 4. The list of synapomorphies, presented below, begins in Scyliorhininae and progressively continues to less inclusive clades within this family. For each clade, only non-ambiguous synapomorphies are listed. After each synapomorphy, the number of the referred character and its state changes are shown in brackets. Synapomorphies followed by an asterisk represent unique transformations in the present analysis. A complete list of character transformations is presented in Appendix 5. Relative Bremer support values are shown in Figure 30 below each node.

Monophyly of clade 1
The hypothesis of the monophyly of the Scyliorhininae is supported by eight synapomorphies, four of them proposed for the first time herein. This clade is composed of Scyliorhinus, Cephaloscyllium and Poroderma. Monophyly of the Scyliorhininae was previously proposed by Compagno (1998a), who listed loss of the depressor palpebrae nictitantis muscle and loss of the fourth ventral extrabranchial cartilage as synapomorphies for the subfamily (both corroborated herein). However, no cladistic analysis was performed by this author. Later, Iglésias et al. (2005), Human et al. (2006 and Naylor et al. (2012aNaylor et al. ( , 2012b corroborated the monophyly of this clade using molecular data.

Monophyly of clade 3
The monophyly of the clade formed by Scyliorhinus and Cephaloscyllium is supported by seven synapomorphies. Compagno (1988a) already had proposed a close relationship between both genera, listing the loss of upper labial furrows and pseudopera rudimentary and absent as synapomorphies. Here, absence of the upper labial furrows is not considered a synapomorphy for this clade and features of the pseudopera were not included in the present analysis as this structure is poorly defined. Monophyly of clade 9 The monophyly of the clade, formed by S. stellaris, S. cabofriensis, S. canicula, S. capensis, S. comoroensis, S. cervigoni, S. duhamelii, S. garmani, S. haeckelii, S. meadi, S. torazame, S. torrei and S. ugoi, is supported by the following synapomorphy: 1. Accessory terminal cartilage absent [char. 72, 0 > 1].
Scyliorhinus stellaris is hypothesised as the sister group of all remaining species of Scyliorhinus (cited above) and characterised by the following autapomorphy: 1. Higher intestinal valve count [char. 5, 0.420 > 0.670-0.750].
In some trees: Scyliorhinus cabofriensis is hypothesised as the sister group of S. haeckelii, S. cervigoni and S. ugoi, but no unique autapomorphies were found for this species.
No unique autapomorphies were found in the present analysis for S. haeckelii and S. ugoi. Scyliorhinus cervigoni is characterised by the following autapomorphy:

Phylogeny of Scyliorhinus species
The phylogenetic relationships of species of the subfamily Scyliorhininae on the basis of morphological data and inferred from a numerical cladistic study including all Scyliorhinus species, are here presented for the first time. The monophyly of Scyliorhininae is supported by the absence of the muscle depressor palpebrae nictitantis, nasal apertures at the same level on nasal capsules, articular region of the quadratomandibular joint of Meckel's cartilage, characterised by a posterior lingual condyle opposite to the facet, three ventral extrabranchial cartilages, terminal dermal cover extending to one-third of the clasper glans, absence of accessory dorsal marginal cartilage and clasper siphon short and restricted to the pelvic region. Compagno (1988a) listed the absence of the muscle depressor palpebrae nictitantis and the loss of the fourth ventral extrabranchial cartilage as synapomorphies for Scyliorhininae. He also mentioned the reduction of claspers components and of the second dorsal fin as diagnostic characters for this subfamily. However, Compagno (1988a) did not mention which parts of the clasper are reduced or absent in the subfamily and his descriptions of carcharhiniform genera did not present detailed information on the skeletal anatomy of the copulatory organs. Soares (2020) reported the presence of an accessory dorsal marginal cartilage in many scyliorhinid taxa, but not in species of Cephaloscyllium and Poroderma. Regarding the great variability of sizes and position between dorsal fins, their relative sizes were not included in the present analysis as they are highly influenced by ontogeny and preservation, especially in specimens of Apristurus and Cephalurus.
Scyliorhinus is hypothesised to be the sister group of Cephaloscyllium, sharing with it the presence of only one upper labial cartilage, lateral processi rastriformis similar in size to the dermal papillae, coracoid bar with a well-developed medial projection corresponding to more than twice the size of its lateral portion, a well-developed rhipidion presenting a prominent posterior margin and extending throughout the clasper glans and the absence of the ventral marginal 2 cartilage. A closer relationship between Scyliorhinus and Cephaloscyllium was also pro-posed by Compagno (1988a) who listed the absence of upper labial furrows and pseudopera absent or rudimentary in claspers as diagnostic characters.
The monophyly of Scyliorhinus is supported by the presence of a projected flap on the upper lip margin, of a pelvic apron and an ephyseal notch at the posterior border of the anterior fontanelle on the neurocranium. The presence of a pelvic apron is observed in Scyliorhinus, Asymbolus and Holohalaelurus, being more developed and extending to at least two thirds or almost the entire length of pelvic inner margins in Scyliorhinus species. The presence of an ephyseal notch on the neurocranium of Scyliorhinus species is unique amongst scyliorhinines. The presence of a projected flap is the main character used by many authors to identify species of Scyliorhinus (Garman 1913;Bigelow and Schroeder 1948;Springer 1966Springer , 1979Compagno 1988a;Compagno et al. 2005;), but is proposed as a synapomorphy for these species for the first time herein. This flap is also present in Poroderma africanum, but this species is hypothesised as the sister group of P. pantherinum, sharing with it the following characters: anterior nasal flap divided into two portions (medial and lateral), presence of a muscular nasal barbel, distance between internal carotid foramina greater than the distance between internal carotid and stapedial foramina, absence of an accessory terminal cartilage, ventral terminal cartilage posteriorly situated (posterior to the half-length of the ventral terminal cartilage) and colour pattern not composed of transverse saddles. Additionally, Poroderma is hypothesised as sister group of the clade formed by Cephaloscyllium + Scyliorhinus. Springer (1979) pointed out that the unique configuration of the nasoral region of S. canicula would be sufficient to guarantee the allocation of all other species of the genus in a distinct taxon; we note here that the same configuration is present in S. duhamelii. Some authors also made comments on the similarities observed in the nasoral region of Scyliorhinus canicula and species of Atelomycterus and Haploblepharus, highlighting the need of a more detailed examination and the investigation of phylogenetic relationships amongst these taxa (Compagno 1988a;Bell 1993). According to our results, S. canicula and S. duhamelii are distinguished from species of Atelomycterus and Haploblepharus by the absence of upper labial furrows and the presence of posterior nasal flaps (vs. upper furrows present and posterior flaps absent in Atelomycterus and Haploblepharus). Additionally, S. canicula and S. duhamelii share with their congeners the presence of a flap on the upper lip that projects laterally, covering the lower labial furrows and the presence of a pelvic apron in males. Similarities amongst S. canicula and S. duhamelii and species of Atelomycterus and Haploblepharus have been suggested as being the result of adaptative convergence to benthic habits (Bell 1993). However, these characters are not present in other demersal scyliorhinids.
Species of Cephaloscyllium, here examined, shared the following synapomorphies: absence of an upper labial furrow, presence of a postoral groove, origin of a second dorsal fin anterior to the half-length of the anal fin, muscle bundles of muscle coracohyoideus well separated along all their extension and higher values for monospondylous vertebrae, upper and lower tooth row counts. Postoral grooves are observed in all species of Cephaloscyllium with varied extensions, but no flap or labial furrow is found in any of them (17 species are considered valid; Fricke et al. 2020). Notches near the lower edge of the mouth are observed and illustrated for specimens of C. signorum , C. variegatum and C. zebrum  and can be confused with lower labial furrows without a detailed examination.
Clasper morphology contributed important characters that helped elucidate the phylogenetic relationships among species of Scyliorhinus and other scyliorhinines (21 characters from the clasper were included in the present analysis). Amongst the most relevant characters are the following: dermal denticles along the dorsal surface of the clasper, degree of development of the envelope, configuration of terminal dermal cover, occurrence of accessory terminal and ventral terminal 2 cartilages and shape of dorsal terminal 2 cartilage. A closer relationship between S. boa and S. retifer was proposed by Goode and Bean (1896) and Garman (1913), based on colour pattern of both species, which is corroborated here by clasper morphology. Both species share the presence of a well-developed and medially-expanded envelope that lacks dermal denticles, covering the anterior portion of the cover rhipidion; this condition is also observed in S. hesperius. The clade, formed by Scyliorhinus cabofriensis, S. cervigoni, S. haeckelii and S. ugoi, is supported by the presence of a reduced dorsal terminal 2 cartilage. These species are distributed in the Southern Atlantic Ocean, off the eastern coast of Brazil (S. cabofriensis, S. haeckelii and S. ugoi) and west coast of Africa (S. cervigoni), with records in similar latitudes, suggesting a common evolutionary history that may date from the formation of the Atlantic Ocean.
According to Springer (1966: p. 597), species of Scyliorhinus distributed in the Western Central Atlantic may form a 'compact infrageneric group', as they are more similar to each other than they are to species in the Eastern Atlantic and Western Pacific. According to our results, however, this hypothesis is not corroborated because of the closer phylogenetic relationships of species from the Western Central Atlantic with those from other regions. Scyliorhinus torrei is hypothesised here to being more closely related to S. capensis (Southeastern Atlantic), S. torazame (Western Pacific), S. canicula and S. duhamelii (North-eastern Atlantic and Mediterranean Sea) by sharing a well-developed pelvic apron with pelvic inner margins almost entirely fused. Scyliorhinus boa, S. hesperius and S. retifer form a clade hypothesised as the sister group of all species of Scyliorhinus.

The impact of morphological characters
Characters from the nasoral region, dermal denticles, claspers, vertebrae and intestinal counts were revealed to be extremely important to shed light on the phylogenetic relationships amongst scyliorhinines and may contribute to future phylogenetic analyses concerning scyliorhinids. A more detailed examination of the nasal flaps and labial furrows allows for the identification of differences amongst the genera Atelomycterus, Haploblepharus and Scyliorhinus and clarifies questions related to the distribution and variation of characters amongst species of Scyliorhinus (e.g. S. canicula and S. duhamelii).
Data from tooth morphology of catsharks are scarce and the only study that reported tooth characters for Scyliorhinidae is Herman et al. (1990). Besides this study, information on sexual and ontogenetic heterodonty are found only for a few species (Brough 1937;Nakaya 1975;Springer 1966;Compagno 1988a;Gomes and Tomás 1991;Litvinov 2003;Soares and de Carvalho 2019) and for some scyliorhinid species, heterodonty seems to be absent (Weigmann et al. 2018). In this study, males and females, adults and juveniles were not available for some species and, thus, it was not possible to investigate the influence of sexual dimorphism and ontogeny in tooth characters (mainly regarding the number of cusplets and degree of development of striae). As a consequence, characters of tooth morphology were not included in the present analysis.
Despite the relevance of characters associated to claspers in species identification and phylogenetic analyses, information on the internal anatomy of these organs are found only for some species and mainly in classical works about clasper morphology (Jungersen 1899;Leigh-Sharpe 1920, 1921, 1922, 1924aCompagno 1988a), being absent in most species descriptions and taxonomic reviews (Human 2006b;Séret and Last 2007;Nakaya et al. 2013; amongst others). Soares (2020) provided detailed descriptions of clasper structures in almost all catshark genera and demonstrated the uselfulness of claspers for taxonomic and systematic purposes. We highlight here the importance of including clasper descriptions in taxonomic studies.

Morphology and molecular data
The monophyly of the subfamily Scyliorhininae is corroborated by the present study, as well as by phylogenetic analyses, based on molecular data (Iglésias et al. 2005;Human et al. 2006;Naylor et al. 2012aNaylor et al. , 2012b. However, morphology and molecular-based studies diverge on the hypotheses of relationships amongst Scyliorhinus, Cephaloscyllium and Poroderma (Fig. 31). In this study, Cephaloscyllium is hypothesised as the sister group of Scyliorhinus, based on clasper and skeletal characters. Naylor et al. (2012aNaylor et al. ( , 2012b) hypothesised a closer relationship between Poroderma and Scyliorhinus, analysing the NADH2 mitochondrial gene and conducting a model-Bayesian phylogenetic analysis.
The monophyly of the genus Scyliorhinus is supported here and also by Human et al. (2006) and Naylor et al. (2012aNaylor et al. ( , 2012b. The phylogeny of Iglésias et al. (2005) resolved Scyliorhinus as paraphyletic, with a weakly-supported relationship between S. torazame and Cephaloscyllium umbratile. These authors analysed only few species of Scyliorhinus and no species of Poroderma was included in the analysis (Iglésias et al. 2005).
In the present study, we contribute to the understanding of the phylogenetic relationships amongst Scyliorhinus species. In recent molecular studies, only few species of Scyliorhinus were included and, therefore, little information on infrageneric relationships could be obtained (Iglésias et al. 2005;Naylor et al. 2012aNaylor et al. , 2012b. Nevertheless, a closer relationship between S. retifer and S. stellaris was recovered by Naylor et al. (2012a), which agrees with the results presented here.
Despite the contributions presented here for the phylogeny of Scyliorhininae, there is a great need to review the taxonomy of Cephaloscyllium, including the examination of clasper morphology in its species. Deeper considerations on the monophyly of Scyliorhinidae and the phylogenetic relationships amongst scyliorhinids and other taxa were not performed here, since additional taxa of other carcharhiniform families should be included in a broader phylogenetic analysis. Taxonomic reviews, detailed morphological studies and cladistic analyses, based on morphological and molecular data, are necessary to improve our understanding of the phylogenetic relationships amongst scyliorhinids and other carcharhiniforms.

Conclusions
• The monophyly of Scyliorhininae is supported by four characters proposed by Compagno (1988a) and other four proposed for the first time; • Scyliorhinus is hypothesised to be the sister group of Cephaloscyllium, sharing with it the presence of only one upper labial cartilage, lateral processi rastriformis similar in size to the dermal papillae, coracoid bar with a well-developed medial projection corresponding to more than twice the size of its lateral portion, a well-developed rhipidion presenting a prominent posterior margin and extending throughout the clasper glans and the absence of the ventral marginal 2 cartilage. • The monophyly of Scyliorhinus is supported by the presence of a projected flap on the upper lip margin, of a pelvic apron and an ephyseal notch at the posterior border of the anterior fontanelle on the neurocranium. • Characters from the nasoral region, dermal denticles, claspers, vertebrae and intestinal counts were revealed to be extremely important to shed light on the phylogenetic relationships amongst scyliorhinines and may contribute to future phylogenetic analyses concerning scyliorhinids and carcharhiniforms. • Results presented here mostly agree with those obtained in recent phylogenetic analyses, but further work integrating molecular and morphological data is still needed.