Bollettino della Società Paleontologica Italiana, 51 (3), 2012, 203-212. Modena, 30 dicembre 2012

A new species of Sangiorgioichthys (, ) from the Kalkschieferzone of Monte San Giorgio (Middle ; Meride, Canton Ticino, Switzerland)

Cristina Lombardo, Andrea Tintori & Daniele Tona

C. Lombardo, Dipartimento di Scienze della Terra “Ardito Desio”, Via Mangiagalli 34, I-20133 Milano, Italy; [email protected] A. Tintori, Dipartimento di Scienze della Terra “Ardito Desio”, Via Mangiagalli 34, I-20133 Milano, Italy; [email protected] D. Tona, Corso Rigola 64, I-13100 Vercelli, Italy; [email protected]

KEY WORDS - Actinopterygii, Early Semionotidae, new taxon, Ladinian, Monte San Giorgio.

ABSTRACT - The genus Sangiorgioichthys is one of the few Semionotidae known from the Middle Triassic. The type species S. aldae Tintori & Lombardo, 2007 has been found in Late Ladinian marine deposits of both the Italian and Swiss sides of Monte San Giorgio. A second species, S. sui López-Arbarello et al., 2011 described from the Pelsonian (Middle Anisian) of Luoping (Yunnan, South China) has extended the range of the genus both in time and space. A further species of Sangiorgioichthys, Sangiorgioichthys valmarensis n. sp., is described herein from the Late Ladinian Kalkschieferzone (Meride Limestone) of the Monte San Giorgio area, the same unit yielding the type species. Sangiorgioichthys valmarensis n. sp. differs from the already known species in number and arrangement of suborbitals, shape of the teeth and in shape and row number of the scales. The new species of Sangiorgioichthys increases the diversity of Semionotidae already in the Middle Triassic, indicating that the explosive radiation of Semionotidae during the was preceded by a first phase of diversification during the Middle Triassic.

RIASSUNTO - [Una nuova specie di Sangiorgioichthys (Actinopterygii, Semionotiformes) dalla Kalkschieferzone del Monte San Giorgio (Triassico Medio; Meride, Canton Ticino, Svizzera)] - Il genere Sangiorgioichthys è uno dei pochi Semionotidae noti dal Triassico Medio. La specie tipo S. aldae Tintori & Lombardo, 2007 è stata rinvenuta in depositi del Ladinico Superiore sia sul versante italiano che su quello svizzero del Monte San Giorgio. Una seconda specie, S. sui López-Arbarello et al., 2011, del Pelsonico (Anisico Medio) di Luoping (Yunnan, Cina meridionale) ha esteso la distribuzione del genere nello spazio e nel tempo. In questo lavoro viene descritta Sangiorgioichthys valmarensis, una nuova specie di Sangiorgioichthys rinvenuta nella stessa unità da cui proviene la specie tipo (Kalkschieferzone, Calcare di Meride) del Ladinico Superiore dell’area del Monte San Giorgio. Il nuovo taxon differisce dalle specie già note per la forma e la disposizione dei suborbitali, la forma dei denti e per numero di file e forma delle scaglie. La nuova specie di Sangiorgioichthys mostra come i Semionotidae fossero già diffusi e diversificati durante il Triassico Medio, indicando come la loro radiazione esplosiva durante il Norico (Triassico Superiore) sia stata in realtà preceduta da una prima fase di diversificazione durante il Triassico Medio.

INTRODUCTION subdivided in at least two different assemblages (Tintori, 1990; Lombardo, 1999, 2001, 2002; Tintori & Lombardo, The Monte San Giorgio area (Fig. 1) is one of the 1999, 2007; Lombardo & Tintori, 2004), the nothosaurid historically most important areas for marine vertebrates Lariosaurus (Tintori & Renesto, 1990; Renesto et al., of the Middle Triassic. More than 150 years of scientific 2003), three crustaceans (the mysidiacean Schimperella, excavations in a sequence of several fossiliferous levels the conchostracan Laxitextella and very rare undescribed concentrated in a few square kilometres, led this site decapods), a few insects mostly still undescribed to be totally (Italian and Swiss sides) included in the (Krzeminski & Lombardo, 2001; Bechly & Stockar, 2011) UNESCO World Heritage List in 2010 for its unique and a few terrestrial plant remains. If we compare the outstanding palaeontological significance regarding fossil assemblages in the KSZ with those from the lower the evolution of marine vertebrates during the Middle Meride Limestone Cava Inferiore, Cava Superiore and Triassic. The best known fossiliferous unit is the Besano Cassina, we do not see many differences in the number Formation of latest Anisian - earliest Ladinian age, but of vertebrate and invertebrate taxa found in each single since 25 years our research group is working on the poorly level (Bürgin, 1998, 1999); on the contrary, the Besano investigated uppermost part of Meride Limestone, the Formation assemblages are made of many more taxa, both Kalkschieferzone (KSZ), of probable latest Ladinian age vertebrates and invertebrates (Lombardo, 1999; Röhl et (see Stockar et al., 2012). al., 2001) pointing to a strictly marine environment. During about 25 years of excavations lead by two of the authors (AT and CL), a number of interesting fossils has been reported from the lower/middle part of TAPHONOMY AND PALAEOENVIRONMENT OF the upper member of the Meride Limestone, from both THE KALKSCHIEFERZONE the Italian and Swiss sides of the Monte San Giorgio palaeontological area. However, the general biodiversity In the KSZ no sure marine stenohaline organism has of the KSZ is quite low: about 20 species actually been found, leaving apart the nothosaurid Lariosaurus

ISSN 0375-7633 doi:10.4435/BSPI.2012.23 204 Bollettino della Società Paleontologica Italiana, 51 (3), 2012

p. 27), can be considered as a mass mortality one: a flood brought the insects and the plant remains in the basin and also killed the small , which were used to dwell in marine salt waters. The presence of five fish specimens plus three insects are really worth of a ‘mass mortality event’ interpretation, for such a restricted excavation surface: the number of fish specimens per square meter is actually very low in these levels, with the exception of surfaces with up to 50 Prohalecites specimens per square meter. The average ‘richness’ in a fossiliferous level, following many years of field works in the KSZ, could be considered as one specimen every several dozens square meters for each lamina surface. Actually, Bechly & Stockar (2011) did not find any other fossil in the two meters thick sequence yielding Dasyleptus and the small fishes, proving that the fossiliferous surface in the whole is strictly related to the flooding. Fig. 1 - The Monte San Giorgio area. The stout black line indicates The lower and middle KSZ provide a very high the Besano Formation outcrops with small faults displacing number of specimens on mass mortality surfaces, the unit. The Meride Limestone outcrops South to the Besano compared to the regular (attritional) mortality ones. Fig. Formation. Stars indicate the position of the two major sites for the 2 shows the distribution of specimens in different beds Kalkschieferzone. After Lombardo (2002), modified. of the site Meride-Val Mara D (lower part). The genus Peltopleurus is particularly interesting in its distribution as it amounts to 273 specimens on a total of 471 fishes and the fishes, most of them strictly related to the marine recovered during the 1997-2001 excavations, for a bed environment: in fact, many of the KSZ fish genera have surface of about 15 square meters (Fig. 2a). Four single been found also in other localities that can be considered surfaces can be considered as result of a mass mortality surely marine, such as Luoping, in southern China event, with 20 (Bed 15) to 151 specimens (Bed 1) each. (Lombardo et al., 2011; Lopez-Arbarello et al., 2011) or All the remaining layers yield Peltopleurus too, but the Perledo along the eastern coast of the Lario Lake (Tintori number of specimens ranges from one to six for each & Lombardo, 1999; Lombardo et al., 2008) or even the one, widespread throughout the whole laminated bed. Besano Formation in the same Monte San Giorgio area Not considering the genus Peltopleurus (Fig. 2b), mass (Bürgin, 1999). mortality events are the only explanation for the unusual During the deposition of the Meride Limestone, the record of Coelatichthys meridensis Lombardo, 2001 (32 fresh water influence became stronger: conchostracans and specimens in Bed 7) and Prohalecites porroi (Bellotti, insects point to a quite close land with superficial fresh- 1857) (24, 26 and 30 specimens respectively in Bed a, 1, water ponds, permanent or seasonal, as suggested by the 3; the species is unknown in older beds). Owing to these number of conchostracan-rich surfaces. Tintori (1990a) quite common mass mortality surfaces P. porroi is by far and Tintori & Brambilla (1991) proposed an alternation the most common species across the whole KSZ: in the of dry and very rainy seasons, a monsoonal-like climate middle part of the unit (Ca’ del Frate site, Tintori, 1990), where heavy rains could suddenly affect the KSZ basin Prohalecites constitutes about the 95% of the collected causing mass mortality events in the marine fauna, mainly specimens, but also in the upper part (Val Mara site D) it fishes, as happened at least forProhalecites , Peltopleurus makes at least the 90% of the fish specimens (data based and Allolepidotus, but also for the crustacean Schimperella on 2003 excavation by CL and AT). Thus, it is evident that (Tintori, 1990b). Furrer (1995) proposed that the fish we can consider a mass mortality surface in the KSZ when mass mortalities were related to the dry season increase we have only one specimen per square meter of a single of salinity: this appears quite unlikely as a slow increase surface, especially if they all belong to a single genus of salinity should allow fishes to leave the basin itself, (Prohalecites, Peltopleurus, Coelatichthys) or to two while a strong sudden fresh water input can suddenly genera. For the latter case, we know only mass mortality change the salinity. Also, increasing temperature should surfaces yielding Prohalecites and Peltopleurus together, affect benthic organisms rather than nektonic ones (see in Bed 1 and 2 in Val Mara- Meride site D (lower part) and for instance Cebrian et al., 2011). in surface yielding Dasyleptus. Furthermore, specimens A further support to the fresh water hypothesis as from a mass mortality surface in the KSZ are usually of causing mass mortality in a marine basin after flooding the similar size (Tintori, 1990), while less common species, nearby land, is provided by the assemblage yielding the represented by sparse specimens, show a consistent pattern apterygote insect Dasyleptus triassicus (Bechly & Stockar, of size grouping (Tintori & Lombardo, 1999; Lombardo, 2011), from the upper KSZ. This assemblage, including 2002). As already pointed out (Tintori & Lombardo, three specimens of D. triassicus is here re-interpreted 1999), this also implies that the mortality of marine with respect to the hypothesis of Bechly & Stockar dwellers was concentrated possibly in a single season (2011). A surface of only two square meters yielding three of the year even if not always the adverse conditions led specimens of this terrestrial insect together with ‘diffuse to mass mortality. If we do not take into consideration small land plant remains’, and five specimens of the fishes the specimens of Prohalecites and Coelatichthys, we Peltopleurus and Prohalecites (Bechly & Stockar, 2011: obtain (Fig. 2c) the supposed attritional accumulation C. Lombardo et alii - New actinopterygian from the Triassic of Monte San Giorgio 205

Interbedded to the fish-rich layers, there are levels showing massive quantity of Conchostracans: they are usually almost devoid of fishes (and vice-versa, Tintori, 1990), possibly because when the marine basin was too strongly affected by the fresh waters input from the nearby land for quite a long time, the marine fishes almost totally disappeared from the basin itself. Thus, apart from the mass mortality surfaces yielding usually Prohalecites, seldomly Peltopleurus and Coelatichthys, all the other fish genera are quite rare and their presence may be related to the attritional mortality in ‘normal’ marine condition. Sangiorgioichthys spp. display this distribution pattern: for Sangiorgioichthys aldae we know only five specimens from four different outcrops (three from the lower and middle Kalkschieferzone in the Monte San Giorgio area, one from the Perledo-Varenna Formation in the Lario Lake area; Tintori & Lombardo, 2007) and the new species here described is represented only by the holotype. Possibly the Sangiorgioichthys species in the western Tethys had not a gregarious behaviour, while the eastern Tethys S. sui lived in very large schools, as it is proved by the several mass mortality surfaces extending for at least a few square kilometers in the Luoping area (Sun et al., 2009; Lòpez-Arbarello et al., 2011).

Abbreviations MCSN: Museo cantonale di Storia Naturale, Lugano (Switzerland). b.f., basal fulcra; Br, branchiostegal rays; Cl, cleithrum; c.s., caudal scute; De, dental bone; d.f., dorsal fin; d.l.l.s., scales of dorsal lateral line; Dpt, dermopterotic; Dsph, dermosphenotic; Exsc, extrascapular; f.f., fringing fulcra; Fr, frontal; Io, infraorbitals; l.l.l.s., last lateral line scale; Mx, maxilla; Op, operculum; Pa, parietal; Pcl, postcleithrum; Pmx, premaxilla; Pop, preoperculum; Pt, posttemporal; Sbo, suborbital; Scl, supracleithrum; So, supraorbital bones; Sop, suboperculum.

SYSTEMATIC PALAEONTOLOGY

Subclass Actinopterygii Cope, 1887 Fig. 2 - Number of fish specimens per bed from the lower part of Infraclass Regan, 1925 Val Mara site D, Bed a being the top of the fossiliferous sequence. Order Semionotiformes Arambourg & Bertin, 1958 a) all genera considered; b) all genera but Peltopleurus, to allow a Family Semionotidae Woodward, 1890 pro parte better definition of the distribution of the remaining genera; c) after clearing also Prohalecites and Coelatichthys, the left-over genera Genus Sangiorgioichthys Tintori & Lombardo, 2007 show the rarity of their finds. Type species - Sangiorgioichthys aldae Tintori & Lombardo, 2007 of specimens: it is quite clear that on average we have less than three specimens for each fish taxon (always for Other species - Sangiorgioichthys sui López-Arbarello a surface of about 15 square meters), keeping in mind et al., 2011; Sangiorgioichthys valmarensis n. sp. (this that the major peaks are due to indetermined/unprepared paper). genera. We have also observed that usually, but not always, when a mass mortaly event happened, there are also a high Diagnosis (emended from López-Arbarello et al., number of specimens belonging to other species, apart 2011) - Small semionotiform with dermal bones covered from the dominant one. Furthermore, it can be observed with ganoine; broad postemporal and supracleithral bones; that the total number of specimens has a sudden increase elongate anterior supraorbital; large infraorbital at the around Bed 8, which implies a possible improvement in postero-ventral corner of the orbit; several suborbitals, the environmental conditions, allowing a much larger arranged in two or single rows anteriorly to the crescent- number of individuals to dwell in the lagunes of the KSZ. shaped preoperculum and one or two suborbitals 206 Bollettino della Società Paleontologica Italiana, 51 (3), 2012 occupying a triangular area ventral to the infraorbital indicated by Olsen & McCune (1991), Arratia & Schultze bones and lateral to the quadrate; elongate supramaxilla (1999) and Wenz (1999): a ridge of medio-dorsal scales fitting in a notch on the dorsal border of the maxilla; small with a prominent posterior spine, several infraorbital dorsal fin, limited to the area between the origin of the bones, a large antero-dorsal process on suboperculum, a pelvic and anal fins; complete row of scales in the body narrow and forward-curved preoperculum, a high coronoid lobe above the last scale of the lateral line; dorsal ridge of process on dentary, rostral and nasals roughly tubular, and scales conspicuous, but only with a small spine. a single supramaxilla.

Geographic distribution - Rio Vallone and Ca’ del Frate (Viggiù, Varese, Italy), Perledo (Italy), Val Mara D (Meride, Canton Ticino, Switzerland), and Dawazi Sangiorgioichthys valmarensis n. sp. (Luoping County, Yunnan Province, South China). (Figs 3-7)

Stratigraphic distribution - Kalkschieferzone of the Diagnosis - Small species of Sangiorgioichthys with Meride Limestone and Perledo Member of the Perledo- four suborbitals arranged in a single row anteriorly to Varenna Formation (Ladinian, late Middle Triassic), the preoperculum, and a fifth one placed ventrally to the and Vertebrate Level of the upper member of Guanling large infraorbital at the postero-ventral corner of the orbit; Formation (Pelsonian, Middle Anisian, early Middle narrow maxilla with long and upward bending anterior Triassic). region, bearing thin and conical teeth; button-like teeth on palatal bones; scale covering made by 34 vertical Remarks - As already stated by Tintori & Lombardo rows and at least 23 horizontal rows of thin scales; belly (2007) and López-Arbarello (2008), the presence of region covered by scales longer than deep, with a rounded anterior infraorbital bones, premaxilla with long nasal posterior margin; flank scales deeper than long, with a process, several suborbital bones, conspicuous dorsal slightly rounded and serrated posterior margin; few scales ridge scales (with posterior spine) and the lack of gular of the lateral line with one or two pores; dorsal lateral line plates support the referral of Sangiorgioichthys to the on the third horizontal row. Semionotiformes sensu Olsen & McCune, 1991. The phylogenetic relationships within Semionotiformes is Holotype - MCSN 8425, the only known specimen. still controversial. Tintori & Lombardo (2007) referred Sangiorgioichthys to the family Semionotidae, but López- Type locality - Bed n. 76, Site D (upper part), Val Mara Arbarello (2008) stressed the poor definition of this group, (also called Gaggiolo Valley) near Meride, Unesco WH which most probably represents a non-monophyletic Monte San Giorgio, Canton Ticino, Switzerland. assemblage, therefore considering Sangiorgioichthys a rather primitive form among semionotiforms. The new Etymology - From Val Mara, the locality where the species of Sangiorgioichthys here described seems to specimen has been found. confirm the interpretation given by Tintori & Lombardo (2007), with this genus included within Semionotidae, Geographic distribution - Monte San Giorgio (Canton owing to the series of characters typical of the family Ticino, Switzerland).

Fig. 3 - Sangiorgioichthys valmarensis n. sp. The holotype MCSN 8425 from Bed 76 of the Val Mara site D (upper part). Scale bar: 10 mm. C. Lombardo et alii - New actinopterygian from the Triassic of Monte San Giorgio 207

Fig. 4 - Sangiorgioichthys valmarensis n. sp. a) skull of the holotype MCSN 8425; b) drawing of the skull. Scale bar: 5 mm.

Stratigraphic distribution and age - Uppermost part and fragmentary element, ventrally placed to the of the lower Kalkschieferzone (upper member of Meride suboperculum, but detached from it, can be interpreted as Limestone), latest Ladinian (Middle Triassic). the interoperculum. The bones of opercular region are not Description - The specimen is about 8 cm long in ornamented, being covered by a smooth layer of ganoine. standard length and about 2.5 cm deep in the region The narrow and crescent-shaped preoperculum is vertical immediately behind the skull. It is preserved with the right and bends forwards; it is slightly wider in its ventral region side exposed. The specimen is almost complete, except than in the dorsal one. Two rows of pores, corresponding for a slight disarticulation of the bones of the anterior part to the preopercular sensory canal, are visible; on the of the snout, of the distal elements of the fins and of the posterior margin of the element these openings are larger scales of postero-ventral region of the body. than those arranged on the anterior one. The preoperculum is not ornamented (Figs 3-4). Skull - Both the frontal bones are visible; they are The circumorbital ring comprises supraorbitals and about two and a half times longer than the single parietal infraorbitals. There are two subrectangular supraorbitals; left. They are characterized by an elongated shape, with an the anterior element is long about one time and a half the irregular anterior margin ending with a tip and a straight length of the posterior one. Owing to the preservation of and endented posterior one. The lateral margin shows only the specimen, the supraorbitals of both sides of the skull a slight orbital constriction, where the long supraorbital are visible. Their ornamentation is made of scattered is placed. The interfrontal suture is slightly wavy. The tubercles, while two pores are visible on the postero-dorsal pores of the supraorbital sensory canal open along the corner of the posterior right element. lateral margin of each element reaching the suborbitals. The dermosphenotic is roughly diamond-shaped, Ornamentation consists of tubercles mostly concentrated with irregular margins, and it is dorso-ventrally oriented. along the lateral margin and of short ridges arranged Pores of the infraorbital sensory canal are visible along its perpendicularly to the posterior margin of these elements. anterior margin, and ganoine tubercles are scattered on its The parietal is rectangular, ornamented by tubercles near surface. At least three infraorbitals are recognizable. The the lateral margin and the interparietal suture, which shows element placed below the dermosphenotic is rectangular an irregular profile. The lateral and posterior margins in shape and it is dorso-ventrally crossed by the pores of of the bone are quite straight, contacting respectively the infraorbital sensory canal, which ran near the anterior the dermopterotic and extrascapular bones. The large margin; ventrally, there lies the biggest infraorbital, a dermopterotic is trapezoidal in shape, with tubercles in trapezoidal bone placed on the postero-ventral corner of the anterior-dorsal region of the bone. Extrascapular is the circumorbital ring; the sensory canal ran in cranio- roughly triangular, longitudinally crossed by a series caudal direction along the ventral margin, then bending of large pores corresponding to the supratemporal toward the dorsal region. The last visible infraorbital is commissure and surrounded by a row of tubercles. The triangular and it is placed caudally to the maxilla. All partly preserved postemporal is roughly subtriangular the elements are covered by scattered tubercles, limited (Figs 3-4). to the dorsal margin in the anterior one. The region The opercular region is broad, with a semicircular between preoperculum and infraorbitals is occupied by posterior outline. It is made by an oval-shaped operculum five suborbitals. Four elements are placed caudally to the and a sickle-shaped suboperculum with a well-developed infraorbitals: they are arranged in a single row which, antero-dorsal process, with a depth equaling about one proceeding dorso-ventrally, is made by a small semi- fourth of that of the operculum; a small sub-triangular circular, a broad trapezoidal, a small rectangular and a 208 Bollettino della Società Paleontologica Italiana, 51 (3), 2012

Fig. 5 - Sangiorgioichthys valmarensis n. sp. a) dorsal ridge scales and scales of dorsal lateral line in the holotype MCSN 8425; b) drawing of dorsal ridge scales and dorsal lateral line scales; c) ventral scales of the holotype MCSN 8425; d) drawing of the ventral scales. Scale bar: 5 mm. triangular bone. A large triangular element lies ventrally margin is provided with long and thin teeth only on the to the largest infraorbital. All the elements show a smooth anterior half of the bone. The ventral margin shows very surface (Figs 3-4). large pores of the mandibular sensory canal, but the state Jaws - The upper jaw is made of premaxillary and of preservation of this region of the bone prevents to maxillary bones. The specimen shows both premaxillae, determine their exact number. In the palatal region, dorsal shaped like a scalene triangle with the longest side forming to the first visible infraorbital, small cylindrical teeth with the oral margin, and the shortest one facing anteriorly. a flattened cap, probably related to crushing dietary habits, Near the right premaxilla lies a single small and thin tooth, are detectable. Branchiostegal rays form a row of seven probably belonging to this bone. The elongate maxilla has elongated and partially overlapping triangular bones, a subtriangular shape, with a long and narrow ethmoid decreasing in size anteriorly (Fig. 4b). process projecting antero-dorsally from the anterior end. Near the ventral margin of the maxilla there are a few Pectoral girdle - Cleithrum is curved and dorso- small, conical and slightly curved teeth. The lower jaw ventrally elongated; it is crossed by a row of small shows a broad coronoid process posteriorly to the narrow tubercles. Posteriorly to cleithrum there are two and elongated anterior region of the dentary, whose oral postcleithra: a shorter and broader ventral element and a more elongated dorsal bone, which extends dorsally beyond the dorsal end of cleithrum. Supracleithrum is subrectangular and slightly curved forward, partially overlapping the ventral margin of the dorsalmost element of postcleithrum (Figs 3-4).

Squamation - The squamation is made by ganoid scales covering the entire body. They are arranged in 34 transverse and at least 24 horizontal scale rows, all of them showing a smooth surface. The shape of the scales varies according to their position on the body. The scales of the lateral region of the trunk are subexagonal, deeper than broad up to the insertion of the dorsal fin. Their posterior margin is serrated. The scales decrease in size proceeding posteriorly, becoming subrectangular to rhombic and reducing the serration. In the ventral region, between pectoral and pelvic fins, the scales are as long as deep, with a rhombic shape and a round posterior margin. The region of the belly between the pelvic fins is covered by large scutes. Scales of the caudal peduncle Fig. 6 - Sangiorgioichthys valmarensis n. sp. a) drawing of lateral th rd have a rhombic shape, as long as deep; those covering line scales from 16 to 23 transverse scale row of the holotype the axial body lobe, extending up to half of the dorsal MCSN 8425; b) drawing of a few lateral line scales of the holotype MCSNIO P457 of Sangiorgioichthys aldae, from Tintori & lobe of the fin, have a leaf-like shape, longer than deep. Lombardo (2007). Scale bar: 5 mm. The posterior margin of the axial body lobe are made of C. Lombardo et alii - New actinopterygian from the Triassic of Monte San Giorgio 209

Fig. 7 - Sangiorgioichthys valmarensis n. sp. a) dorsal fin of the holotype MCSN 8425; b) drawing of the dorsal fin; c) caudal fin of the holotype; d) drawing of the caudal fin. Scale bar: 5 mm. rhombic scales arranged in a single row beginning from badly preserved, showing only 5-6 proximal segments of the last scale of the lateral line. There is a mid-dorsal lepidotrichia (Fig. 3). ridge scale row made of lanceolate scales, with a marked The triangular dorsal fin inserts at the level of the median keel (Figs 3, 5, 7). 20th transverse scale row and it is made by at least 12 The passage of the lateral line sensory canal is marked lepidotrichia. Each lepidotrichium is composed by a long by a single pore on most of the corresponding scales of proximal segment, followed by shorter distal segments the flank region; some of them show two pores, while branching at least twice, becoming very thin and delicate. others lack these openings, apparently without a pattern. The anterior margin shows 2-3 basal fulcra and a few thin The dorsal lateral line is detectable by a pore and a slit fringing fulcra (Figs 3, 7a-b). visible on two scales placed in the antero-dorsal region of The anal fin seems to be placed at the same level of the the body, belonging to the third scale row, counting from dorsal one, but due to partial disarticulation of the ventral the mid-dorsal ridge (Figs 5-6). region of the body, this cannot be exactly determined. At least 9-12 rays have been counted: they are composed by Fins - The only visible pectoral fin is the right one; it long proximal segments, followed by shorter segments is composed by at least six lepidotrichia. Each ray is made branching at least twice into narrow and cylindrical of elongated proximal segments and short distal ones. elements (Fig. 3). Due to the disarticulation of the distal end of the fin, it The tail is hemiheterocercal, with an axial body is not possible to evaluate how many times lepidotrichia lobe reaching about half the length of the dorsal lobe. branch. Along the anterior margin of the fin there are 2-3 The number of rays is about 23-24: disarticulation and basal fulcra and a few fringing fulcra. The right pelvic fin dispersal of the ventralmost rays makes difficult to give inserts at the level of the 12nd transverse scale row: it is their exact number. Each ray is made by a relatively 210 Bollettino della Società Paleontologica Italiana, 51 (3), 2012 elongated and stout proximal segment followed by shorter type-species show a posterior margin characterized by few and narrower distal ones, which branch at least twice. The denticles with no precise topographic distribution, while dorsal lobe shows at least 6 dorsal caudal scutes, a basal in Sangiorgioichthys valmarensis n. sp. almost all scales fulcrum on the dorsal lobe and a row of fringing fulcra are serrated. Concerning the shape, the ventral scales of along the dorsal margin of the fin. Ventral margin is badly Sangiorgioichthys valmarensis n. sp. have a clear rounded preserved and only a basal fulcrum and very few fringing posterior margin, contrasting the rhombic outline of S. fulcra are detectable (Figs 3, 7c-d). aldae. Lastly, the scales of the middle dorsal ridge row of Sangiorgioichthys valmarensis n. sp. are narrower and more Discussion - The genus Sangiorgioichthys, erected by lanceolate than those of S. aldae. Tintori & Lombardo (2007) on the basis of material coming Sangiorgioichthys valmarensis n. sp. differs from the from Monte San Giorgio, was so far represented by two older species Sangiorgioichthys sui López-Arbarello et species only: the type-species, Sangiorgioichthys aldae al. 2011, as well. In Sangiorgioichthys valmarensis n. Tintori & Lombardo, 2007, found also in material coming sp., a single pair of extrascapulars has been observed, from Perledo, and a second one from the Middle Triassic of instead of the two present in S. sui. The pattern of the China, Sangiorgioichthys sui López-Arbarello et al., 2011. infraorbital series is also quite different: both species The skull pattern, particularly the peculiar arrangement of have a large infraorbital at the postero-ventral corner circumorbital bones, and the morphology of both upper and of the orbit, but in some specimens of S. sui there is an lower jaws allow to put the new taxon within this genus. elongate element anterior to it, while in Sangiorgioichthys Although the attribution of the new taxon to the genus valmarensis n. sp. the same element has a triangular shape. Sangiorgioichthys is clear, many characters distinguish Suborbitals show even greater differences: S. sui has two Sangiorgioichthys valmarensis n. sp. from the other two or more ventral elements and two caudal elements to the species. The new taxon shows fewer suborbitals than infraorbitals, while Sangiorgioichthys valmarensis n. sp. S. aldae, having five elements instead of the nine of the has only one large, triangular ventral and four elements type-species of the genus; furthermore, the dorsalmost caudal to the infraorbitals. Marginal teeth of S. sui are suborbitals of Sangiorgioichthys valmarensis n. sp. are bigger but shorter, on both upper and lower jaws, than arranged in a single dorso-ventral row, instead of two. those of Sangiorgioichthys valmarensis n. sp.; moreover, Moreover, in S. aldae there are two distinct suborbitals the dentition of the lower jaw of Sangiorgioichthys n. sp. placed ventrally to the large infraorbital at the postero- is different from that of S. sui, having teeth only on the ventral corner of the orbit, whereas in Sangiorgioichthys anteriormost end of the dentary. No crushing teeth have valmarensis n. sp. there is only one suborbital. Anyway, it been reported in S. sui. The maxilla of Sangiorgioichthys should be noted that a specimen of S. aldae (MCSNL 5050) valmarensis n. sp. also differs from that of S. sui having a shows an incomplete separation of the suborbitals placed longer ethmoid process, much more inclined backwardly ventrally and posteriorly to the third, large infraorbital, and pointing to the anterior end of the frontals, whereas in therefore this character could be considered as related to S. sui it is short and points forwards, almost aligned with intraspecific variability. the dorsal margin of the bone. The ethmoid process on the maxilla of Sangiorgioichthys The dermal bones of S. sui are much more ornamented valmarensis n. sp. is longer than in S. aldae and forms an than those of Sangiorgioichthys valmarensis n. sp.: in obtuse angle with the dorsal margin of the bone. In the the new species small ganoine tubercles are mostly new taxon this angle is 110°, while in Sangiorgioichthys concentrated on the surface of infraorbitals, supraorbitals aldae is >120°. and the posterior region of skull roof, while the rest A few small and conical scattered teeth have been of the skull bones are almost smooth. S. sui shows an observed along the oral margin of the maxilla of ornamentation more homogeneously distributed, made Sangiorgioichthys valmarensis n. sp.; all specimens of small tubercles, ridges and patches of ganoine (López- belonging to Sangiorgioichthys aldae have a clearly Arbarello et al., 2011). Scale covering in Sangiorgioichthys edentulous maxilla. Concerning dentition, another valmarensis n. sp. differs from that of S. sui, especially significant difference is the presence inSangiorgioichthys in the belly region: ventral scales of Sangiorgioichthys valmarensis n. sp. of palatal teeth made of cylindrical valmarensis n. sp. show a rounded posterior margin; in S. pedicles with flattened crowns, visible in the area dorsal sui these are rhombic in shape. to the infraorbitals. In Sangiorgioichthys aldae palatal Some of the lateral line scales of Sangiorgioichthys bones bear conical teeth of different size, not supported by valmarensis n. sp. present the pores of the corresponding pedicles. Tintori & Lombardo (2007) in fact note that S. sensory canal randomly arranged in single or coupled aldae is devoid of specialized crushing teeth, as seen, e.g., openings; concerning this character, it apparently differs in tendaguruensis Arratia & Schultze, 1999, L. from S. sui, where the scales show only a single pore and elvensis (de Blainville, 1818), L. deccanensis (Sykes, 1851) a notch along the posterior margin. (see also Wenz, 1967 and Jain, 1983) and L. microrhis Wenz, Sangiorgioichthys valmarensis n. sp. shows therefore 2003. The palatal teeth of Sangiorgioichthys valmarensis a set of characters that indicates the need to erect a new n. sp., although clearly not highly specialized, considering species distinct from the already known S. aldae and S. their small size, show that the lacking of crushing teeth is a sui. The presence of three species of this genus confirms character peculiar of S. aldae but not of the genus as a whole. once more the diversification of Semionotiformes, and Another remarkable distinctive feature of Sangiorgioichthys more specifically Semionotidae, during the Middle Triassic. valmarensis n. sp. concerns the squamation: the scales of Although a great radiation of ‘advanced’ Semionotidae the new taxon appear in fact thinner and more delicate occurred during the Norian (Tintori, 1983, 1996, 1998; respect to the thick ones of S. aldae. Only some scales in the Lombardo & Tintori, 2008), the recent findings of C. Lombardo et alii - New actinopterygian from the Triassic of Monte San Giorgio 211

Sangiorgioichthys from Monte San Giorgio and China 1): Composition of the Fauna. Rivista Museo civico Scienze indicate that a first phase of diversification took place in Naturali “E. Caffi” Bergamo, 20: 93-96. the Middle Triassic, anticipating the explosive radiation of Lombardo C. (2001). Actinopterygians from the Middle Triassic Semionotidae during Late Triassic. of Northern Italy and Canton Ticino (Switzerland): anatomical descriptions and nomenclatural problems. Rivista Italiana di Paleontologia e Stratigrafia, 107(3): 345-369. ACKNOWLEDGEMENTS Lombardo C. (2002). Coelatichthys gen. n.: a new palaeonosciform from the Middle Triassic of Northern Italy and Canton Ticino We are deeply indebted to Markus Felber (former curator at (CH). Rivista Italiana di Paleontologia e Stratigrafia, 108: the MCSN Lugano) for providing the financial support to excavate 399-414. the site in Val Mara between 1997 and 2003, and to Rudolf Stockar Lombardo C. & Tintori A. (2004). New perleidiforms from the (current curator at MCSN Lugano) for allowing the study of the Triassic of the Southern Alps and the revision of Serrolepis specimen. Many thanks also to all students and volunteers who from the Triassic of Württemberg (Germany). In Tintori A. & helped in the field activity. Thanks are due to Toni Bürgin and Arratia G. (eds), Proceedings of the Symposium “Mesozoic Markus Felber who kindly revised the manuscript. Fishes 3 - Systematics, Paleoenvironments and Biodiversity”: 179-196, Verlag F. Pfeil, München. Lombardo C., Rusconi M. & Tintori A. (2008). New perleidiform REFERENCES from the Lower Ladinian (Middle Triassic) of the Northern Grigna (LC). Rivista Italiana di Paleontologia e Stratigrafia, Arambourg C. & Bertin L. (1958). Super-Ordres des Holostéens et 114(2): 263-272. des Halécostomes ( et Halecostomi). In Grassé P. (ed.), Lombardo C., Sun Z.Y., Tintori A., Jiang D.Y. & Hao W.C. Traité de Zoologie 13(3): 2173-2203; Paris (Masson et Cie). (2011). 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