Early Pliocene fishes (Chondrichthyes, Osteichthyes) from Gran Canaria and Fuerteventura (Canary Islands, Spain)
Los peces (Chondrichthyes, Osteichthyes) del Plioceno inferior de Gran Canaria y Fuerteventura (Islas Canarias, España)

J.F. Betancort¹, A. Lomoschitz², J. Meco¹ 

¹ Departamento de Biología, Campus Universitario de Tafira, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain. Email: jbetancor@becarios.ulpgc.es; joaquinfrancisco.meco@ulpgc.es

² Instituto de Oceanografía y Cambio Global (IOCAG), Campus Universitario de Tafira, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain. Email: alejandro.lomoschitz@ulpgc.es

IntroductionTOP

There is little documentation of Canary fossil fishes, with the exception of two publications from the 19th century: (1) the study carried out by Cocchi (1864) in which he created the genus Pharyngodopilus and its two species Ph. canariensis and Ph. Africanus, catalogued in 1857 by the British Museum of Natural History and which formed part of the collection of Charles Lyell; and (2) the study conducted by Rothpletz & Simonelli (1890), which includes Oxyrhina plicatilis, Ag., Oxyrhina sp., Galeocerdo cf. egertoni, Ag., Chrysophrys sp., Nummopalatus africanus, Cocchi and Diodon sigma Martin (Fig. 1). It should be noted that the age of the deposits which contained these fauna were ascribed to the Upper Miocene (Cocchi, 1864; Lyell, 1865) and were included in the Helvetian or Tortonian (Rothpletz & Simonelli, 1890).

The Canary Islands is a volcanic archipelago (Carracedo et al., 2002) and the marine deposits occur intercalated between lava-flows. Pillow-lavas are structures that are formed during the interaction of lava and water. Accordingly, if a pillow-lava enters into contact with a marine deposit under formation, it indicates that they both have the same age. This is the case of the Canary marine deposits containing the fossil fishes studied in this paper that have a ⁴⁰Ar/³⁹Ar age of 4.80 ± 0.03 Ma in Gran Canaria (Meco et al., 2015) and a K/Ar age of 4.83 ± 0.10 Ma in Fuerteventura (Meco et al., 2007). This clearly places the marine deposits in the first half of the Early Pliocene which began 5.33 Ma ago and concluded around 3.60 Ma ago (Grandstein et al., 2004; Walker & Geissman, 2009).

On the basis of this information, we propose: (a) to present the list of fossil fishes contained in these dated deposits, thereby contributing to the elaboration of a corrected biochronostratigraphy, and (b) to check if the fossil ichthyofauna that have been found is consistent with the palaeoceanographic scenario in the area for the Early Pliocene. This scenario is characterised principally by an open Central American Seaway (CAS) (Schmidt, 2007; Montes et al., 2012; Erkens, 2015; Meco et al., 2015; 2016), an open Gibraltar Seaway after the so-called Messinian crisis (Garcia-Castellanos et al., 2009) and warm pantropical waters (Meco et al., 2015) in the Pacific, Subtropical North Atlantic (Ávila et al., 2012) and Mediterranean (Pawellek et al., 2012).

Geological, palaeontological and stratigraphic settingTOP

The Canary Islands comprise seven main volcanic islands and several islets and are located in the Eastern Atlantic Ocean between N 27° and N 30° latitudes, forming a chain that extends latitudinally about 450 km; with the easternmost point just over 100 km off the north-western African coast (Fig. 2). The islands have a complex geological history, with volcanic formations over 20 million years old (Carracedo et al., 2002), but they also include extensive sedimentary deposits (Meco & Stearns, 1981).

They are composed of layers of two materials: (1) reddish conglomerate (rubefacted conglomerates as a result of Fe oxidation) consisting of coarse gravel, cobble and medium to coarse size sand, and (2) grey to white sands, medium to fine in size, with bioturbation structures, which constitute reference layers (or strata) in the local stratigraphy of each island. The original conglomerates, comprised of cobbles and sands with a wide variety of fossils, were deposited on wave-cut platforms tens of kilometres long. Subsequent withdrawal of the sea resulted in oxidation of pebbles and fossil remains because of contact with freshwaters. These reddish sandy conglomerates as a whole are considered regional key layers, in both a stratigraphic and palaeontological sense (Fritsch, 1867; Lomoschitz et al., 2011). All the fossil fish teeth that have been found in these deposits have a heavy layer of enamel with a dark orange colour.

The fauna which accompany the fossil fishes in Gran Canaria and Fuerteventura indicate ecological and climatic conditions very different to those of today. The first information about invertebrate fossils of the Canary Islands was provided by Lyell (1865) and Rothpletz & Simonelli (1890). Detailed studies were later conducted of foraminifera (Anguita Virella & Ramírez del Pozo, 1974), of genus Strombus (=Perisitistrombus) (Meco, 1977), neogastropods (Meco, 1981), bivalves (Meco, 1982), bryozoans (Sendino & Taylor, 2014) and crustaceans (Betancort et al., 2014). The presence of fossil species belonging to the gastropod genus Persististrombus and Nerita, and the coral genus Siderastrea, and others, suggest climate conditions equivalent to those of present day tropical and sub-tropical regions, like the Caribbean Sea (West Atlantic) or the Gulf of Guinea (East Atlantic) (Meco, 1977; Meco et al., 2007, 2015).

Stratigraphic sectionsTOP

The fossil fish specimens were found in sedimentary layers consisting of old coastal and marine deposits which outcrop along over 130 km, if all the stretches are considered together (Fig. 2). As these layers show many lateral variations throughout the outcrops, three sections were chosen as representative of the whole area: Barranco Seco and Tamaraceite sections from NE Gran Canaria Is. (Figs. 3 and 4) and Ajuí section from W Fuerteventura Is. (Figs. 3 and 5). The Barranco Seco locality provided the most numerous and the largest variety of fossil fishes, while the Tamaraceite and Ajuí localities are characterised by the presence of lava flows which have allowed dating of the marine deposits at ca 4.8 Ma.

Barranco Seco sectionTOP

Location: NE Gran Canaria Is., slope on Barranco Seco ravine.

Latitude: 28° 05′ 25.40″, longitude: 15° 25′ 40.25″, height: 85 m (apsl).

This section comprises seven units which are (bottom to top):

Tamaraceite sectionTOP

Location: NE Gran Canaria Is., slope on Tamaraceite ravine mouth.

Latitude: 28° 07″ 12.99″, longitude: 15° 27″ 30.64″, height: 97 m (apsl).

This section comprises seven units which are:

Ajuí sectionTOP

Location: W Fuerteventura Is., slope on Barranco de Ajuí ravine mouth.

Latitude: 28° 24″ 03.86″, longitude: 14° 09″ 21.20″, height: 7 m (apsl).

This section comprises five units which are:

Methodology - Canary Island fossil fishesTOP

The specimens that have been studied form part of the collection belonging to the University of Las Palmas de Gran Canaria (Laboratory of Palaeontology) [ULPGC], with one specimen coming from the collection that belongs to El Museo Canario in Las Palmas de Gran Canaria. We were also able to consult the Rothpletz collection in the Paläontologisches Museum München. Systematics of the present publication for Chondrichthyes follows Cappetta (2012). The teeth terminology for Sparidae is in accordance with Day (2002).

As the Canary marine deposits containing fossil fishes have been isotopic dated in ca 4.8 Ma, we focused the search on bio-geographic and climatic data of the Early Pliocene, and sometimes on the more imprecise Mio-Pliocene information. We also selected one representative locality in the Mediterrannean Sea (Lybia), two in the eastern Atlantic (Morocco and Azores), one at the Atlantic entrance of the Mediterranean Sea and some in the Pacific coast of America just in order to show the dispersal of this fossil fishes at that time.

Systematic palaeontologyTOP

Class CHONDRICHTHYES Huxley, 1880

Order LAMNIFORMES Berg, 1958

Family OTODONTIDAE Glickman, 1964

Carcharocles megalodon (Agassiz, 1843)

Material:

4 teeth (Fig. 6: A1, El Museo Canario); ULPGC fisches n°: f61 to f63.

Localities:

Barranco Seco, La Pardilla (Figs. 2– 4).

Comparisons and systematic attribution:

The teeth are large, thick and robust with a curvature towards the labial commissures in relation to the central position. The distal curvature is more marked as the position of the tooth becomes more posterior. The anterior teeth are, if at all, only very slightly curved towards the internal (lingual) face. The upper teeth are wider, slightly inclined towards the posterior edge and vertical grooves or ridges can be observed on the external (labial) face. Contrastingly, the lower teeth are narrower and more symmetrical. The crown has an equilateral triangular shape with a uniform, strongly serrated edge. The root is bilobed and coarse. All the teeth that have been found correspond to adult specimens (Gottfriend et al., 1996; Pimiento et al., 2010). Those found at La Pardilla site and kept at the Museo Canario are anterior and lateral upper teeth from the right jaw. C. megalodon is a very well known species and our specimens are identified with those studied by Menesini (1969).

Stratigraphic and geographic records:

Pan-oceanic except for the polar seas (Pimiento el al 2016). Late Miocene of Panama (Pimiento et al., 2013) Miocene and Pliocene of Morocco (Lecointre, 1952), Azores (Ávila et al., 2012), Europe (Reinecke et al., 2011), Africa (Antunes, 1978), American Atlantic and the Pacific, Ecuador (Carrillo-Briceño et al., 2014; Yabe et al., 2004).

Genus Parotodus Cappetta, 1980

Parotodus benedeni (Le Hon, 1871)

Material:

2 teeth; ULPGC n°: f71 (Fig. 6: B), f72.

Locality:

Barranco Seco (Figs. 2–4).

Comparisons and systematic attribution:

Robust, triangular crown, inclined towards the commissure. Flat labial face and markedly convex lingual face of the crown. The crown bends towards the commissure, increasing the curvature with the lateral position of the tooth. Smooth edge. Very thick root with two globular and separated lobules. Nutrient canal absent. Our specimens are identified with those from the Azores shown by Ávila et al. (2012).

Stratigraphic and geographic records:

Pliocene de North America, Australia, Japan, Angola, Belgium, Italy (Cappetta, 1987), Mio-Pliocene of the Balearic Islands (Mas, 2003) and the Azores, (Ávila et al., 2012), Lower Pliocene of Huelva (Garcia et al., 2009).

Family LAMNIDAE Müller and Henle, 1838

Genus Cosmopolitodus Glikman, 1964

Cosmopolitodus hastalis (Agassiz, 1843)

Material:

41 teeth; ULPGC n°: f31 (Fig. 6: C) to f341.

Localities:

Barranco Seco, San José, Ciudad Jardín, Arenales-Chil, Bañaderos (Fig. 2–4).

Comparisons and systematic attribution:

The length from tip to base of the crown of the numerous teeth varies between 2.5 cm and 4.3 cm. The teeth are very similar to those of C. carcharias, differing in their smooth edge. The teeth are triangular, thin and compressed. The external face of the crown is concave or flat, with vertical grooves observable on rare occasions. The root is short with strongly diverging lobes that are generally blunt and small. The teeth of the lower jaw are thicker than their upper counterparts, with a more dense and robust appearance though their crown is narrower and rises vertically describing a slight sigmoidal curve in the anterior teeth. The external face presents a slight concavity that is particularly noticeable in the anterior teeth. We attribute these specimens to C. hastalis given their strong resemblance to the material published by Ávila et al. (2012, Fig. 5) of Azores origin.

Stratigraphic and geographic records:

Cosmopolite Mio-Pliocene, Miocene of Peru (Klug & Kriwet, 2008), Pliocene of Belgium (Herman et al., 1974) and North America (Purdy et al., 2001). Pliocene Mediterranean (Marsili et al., 2007), Late Miocene and Early Pliocene of the Azores (Ávila et al., 2012), late Early Pliocene of Spain (García et al., 2009).

Genus Isurus Rafinesque, 1810

Isurus cf. oxyrinchus Rafinesque, 1810

Material:

4 teeth; ULPGC n°: f41 (Fig. 6: D1), f42, (Fig. 6: D2) to f44.

Locality:

Barranco Seco (Figs. 2–4).

Comparisons and systematic attribution:

The teeth display different states of preservation: none retain the root and two retain the tip of the crown. The teeth have a narrow crown with a very sharp edge. The bulging external face is scored with longitudinal grooves and the internal face is convex and smooth. The teeth are labially inclined and present a slight sigmoidal curvature. The lingual face resembles that of the anterior teeth of C. hastalis, though differing in the thickness of the tooth and the bulging appearance of its external face. The narrowness of the crown and the bulging appearance of the external face from base to tip are characteristic features of this species, along with a slight depression at the base of the crown observable on both faces though more pronounced on the external face. Our specimens are very similar to those shown in Marsili et al. (2007).

Stratigraphic and geographic records:

Upper Miocene and Lower Pliocene of Chile (Long, 1993) Pliocene of the south and southeast of Spain (Malaga and Catalonia) (Marsili et al., 2007). In the present day, it appears near shores with a temperate climate and tropical waters, and can migrate into warmer waters in winter (Dyldin, 2015).

Family ODONTASPIDIDAE Müller and Henle, 1839

Genus Carcharias Rafinesque, 1810

Carcharias cf. acutissima (Agassiz, 1843)

Material:

7 incomplete teeth; ULPGC n°: f11 (Fig. 6: E), to f17

Localities:

Barranco Seco, Aljibe de la Cueva and Barranco de los Molinos (Figs. 2–5).

Comparisons and systematic attribution:

The available material is considered scarce and fragmented. The most complete specimen (Fig. 6) is a long and vertical crown 18 mm in length that is a first upper anterior tooth in the left side of the upper jaw. Even tough dental morphology varies with the position on the jaw, the longer and vertical teeth of C. acutissima, and the most similar species C. taurus, correspond to the upper or lower anterior position (Cunningham, 2000).

For the purpose of making a roughly quantitative comparison with other similar teeth and given the longer teeth of C. acutissima, we calculated a slenderness index of the crown (width at midlength / length, on the lingual side). This index gave us a value of ca 0.17. We compared the value of this index with that of the single specimen of the Azores (Ávila et al., 2012, Fig. 4; an upper anterior tooth) and found them to be practically identical (ca 0.16). Bauzá & Plans (1973) specimen (lám 4 Fig 28; Catalonya) is ca 0.16 as well. The corresponding slenderness index of the most similar teeth to these, those of C. cuspitada, is ca 0.25 (Bauzá & Plans, Lám 5, Fig. 36) and C. taurus is ca 0.23 measured in a identical dental piece (Cunningham, 2000).

Stratigraphic and geographic records:

Cosmopolite Mio-Pliocene species (Cappetta, 1987). Pliocene of Morocco (Lecointre, 1952), Pliocene of Majorca (Mas, 2000), Early Pliocene of North Carolina USA (Purdy et al., 2001) and Pliocene of Ecuador (Cione et al., 2007).

Order CARCHARHINIFORMES Compagno, 1977

Family Carcharhinidae Jordan and Evermann, 1896

Genus Carcharhinus Blainville, 1816

Carcharhinus cf. leucas (Valenciennes, 1839 in Müller and Henle, 1839–1841)

Material:

One tooth and 3 incomplete teeth; ULPGC n°: f21 (Fig. 6: F1), f22 (Fig. 6: F2), to f24.

Localities:

Barranco Seco, Ciudad Jardín, Bañaderos (Figs. 2–4).

Comparisons and systematic attribution:

Though found specimens are scarce, one of them is nearly complete (Fig. 6, F1) and corresponds to an upper anterior-lateral tooth comparable to those from the Italian Pliocene (Marsili, 2007).

The triangular shaped fragments correspond to a broad crown of small thickness. Inclination of the teeth is slightly towards the lingual face. The lingual face is flat and the labial face slightly convex. Grooves can be seen at the base of the crown that are more marked on the labial face. The lateral teeth have a marked curvature.

Stratigraphic and geographic records:

Miocene to Recent. They lived in warm oceans. Miocene Pacific coasts of South America (Lovejoy et al., 2006), Pliocene of North Carlolina (Purdy et al., 2001) and California (Applegate, 1978) in the USA, Angola (Antunes, 1978) and Italy (Marsili, 2007).

Carcharhinus cf. priscus (Agassiz, 1843)

Material:

One tooth; ULPGC n°: f81 (Fig. 6: G1)

Locality:

Barranco Seco (Figs. 2–4).

Comparisons and systematic attribution:

A single lateral tooth from the lower jaw with complete root. Small-sized triangular crown (0.8 cm high), smooth internal and convex external faces. Smooth edge. Very open root. Our tooth is comparable with those from Hungary studied by Kocsis (2007).

Stratigraphic and geographic records:

Neogeno de Peru y Ecuador (Carrillo-Briceño et al., 2014), Miocene and Early Pliocene of the Mediterranean and Belgium (Menesini, 1969; Cappetta 1987). Early Pliocene of Huelva (García et al., 2011).

Genus Galeocerdo Müller & Henle, 1837

Galeocerdo cf. aduncus Agassiz, 1843

Material:

11 teeth; ULPGC n°: f51 (Fig. 6: H1), f52 (Fig. 6: H2) to f511.

Locality:

Barranco Seco (Fig. 2–4).

Comparisons and systematic attribution:

The teeth are triangular, highly curved and in general more wide than long. The crown is markedly crenulated. A strongly serrated talon emerges from the posterior edge, with denticles or secondary cusps whose size decreases regularly in a backwards direction. The differences in size and inclination of the tooth become more pronounced as they are found in a more posterior position. The anterior edge of the crown is convex and the posterior edge is strongly inclined forming an angle close to 90° with the talon. The whole edge is heavily dentated. Crenulation is finer on the main cusp and more pronounced in the anterior region. Denticles or secondary cusps can be observed emerging from the talon. The root is slender and presents two very open lobes which form an angle of between 130° and 140°. It is separated from the crown by a small groove parallel to the base of the crown. The Miocene Galeocerdo aduncus disappears in the Pliocene, giving place to G. cuvier (Menesini, 1969). However, our specimens resemble those shown in Marsili et al., (2007), while differing from those shown by Pawellek et al., (2015) particularly with respect to the angle formed by the posterior edge and the talon, which is much bigger in G. cuvier. They also differs a lot to those G. cuvier shown by Carrillo-Briceño et al., (2015; Table Fig. 3 OP Miocene and QR Early Pliocene), mainly because those are very small and long and, by contrast, the canary specimens are nearly the same in length and in thickness. Lobule aperture at the root is wider in G. cuvier (about 160°) than in our specimens.

Stratigraphic and geographic records:

Neogene of Ecuador (Carrillo-Briceño, 2014), Miocene of Europe, America, Asia (Marsili et al., 2007), Early Pliocene of Huelva (García et al., 2011).

Class OSTEICHTHYES Huxley, 1880

Order PERCIFORMES Johnson and Patterson, 1993

Family SPARIDAE Linné, 1758

Genus Archosargus Gill, 1865

Archosargus cinctus (Agassiz, 1843)

Material:

593 teeth; ULPGC n°: f91 (Fig. 7: A1), f92 (Fig. 7: A2), f93 (Fig. 7: A3), f94 (Fig. 7: A4), f95 (Fig. 7: A5), f96 (Fig. 7: A6), f97 (Fig. 7: A7) to f9593.

Localities:

A few specimens appear in all the localities (Fig. 2), but the largest collection comes from the Barranco Seco (Figs. 3–4) locality with a total of 469 teeth.

Comparisons and systematic attribution:

There are three dentition types: molariform, conical and incisiform. The largest sized teeth are molariform, ranging between 42 mm and 162 mm in diameter. These are circular, hemispherical shaped and have a central depression. Some of the molariform teeth are significantly smaller in size, ranging between 5 mm and 8 mm, while others have an oval contour and yet others a somewhat reniform contour. A neck-like root structure with radial grooves can be observed at the base of the crown. The size of the conical teeth is approximately half that of the molariforms. As for the incisiforms, the crown is quadrangular and slightly broader than the root, convex and concave respectively in the external and internal faces. The concave part of the internal face becomes wider from the base to the cutting edge where it extends along its full length.

The morphology of the Sparid fossil teeth allows us to assign them for the first time to the genus Archosargus. According to Day (2002, Fig. 13), the Sparidae which have molariform teeth belong to the genera: Sparus, Argyrops, Calamus, Archosargus, Acacthopagrus, Diplodus, Crenidens, Stenotomus, Lithognatus and Pagrus. If we eliminate the genera which possess caniniform as well as molariform teeth (Sparus, Argyrops, Calamus, Acacthopagrus, Crenidens, Stenotomus, Lithognatus and Pagrus) and the genus in which conical teeth are absent (Diplodus), the only genus that satisfies the condition of having only molariform, conical and incisiform teeth is Archosargus. In Archosargus probatocephalus (Walbaum, 1792; Worcester, 2012), a present day species of the Caribbean (Smith, 1997), the following features are observed: (a) some 120 – 130 teeth; (b) the lingual teeth are the largest with a spheroid shape that becomes more ellipsoidal towards the anterior part; (c) the labial series is comprised of conical teeth; and (d) there are central teeth in the maxilla of notably smaller size. There are 6 incisiforms in the upper maxilla and 8 in the lower. From the deposits of the Early Pliocene of the Canary Islands, we have examined 382 spheroidal molariform teeth, 154 oval-shaped molariforms, 55 conical teeth and 2 incisiform belonging to sparid fossils. The proportions and morphologies are roughly in agreement with, on the one hand, a dentition pertaining to the genus Archosargus and, on the other with fossils attributed before the work of Day (2002) to the species Sparus cinctus and subsequently to sparid morphotypes of undetermined genus (Marsili et al., 2007). Accordingly, we consider we are justified in attributing the sparid fossils of the Canary Islands to a species of the genus Archosargus.

Stratigraphic and geographic records:

Miocene of Morocco (Lecointre, 1952). Miocene and Pliocene of Europe and the Mediterranean, in the Atlantic from the north coast of Africa to the coast of Angola and in the Caribbean (Menesini, 1968; Bauzà & Plans, 1973; Mas, 2000). A Lower Pliocene fossil fish found in Mediterranean Libya could be attributed to the genus Archosargus (Pawellek et al., 2015).

Family LABRIDAE Cuvier, 1816

Genus Labrodon Gervais, 1857

Labrodon pavimentatum Gervais, 1857

Material:

63 pharyngeal plates; ULPGC n°: f101 (Fig. 7: B1), f102 (Fig. 7: B2), f103 (Fig. 7: B3), f104 (Fig. 7: B4), f105 (Fig. 7: B5 and B6) to f1063.

Localities:

Barranco Seco, Ciudad Jardín (Figs. 2–4).

Comparisons and systematic attribution:

Among the numerous pharyngeal plates found in various states of conservation we have chosen for representation purposes: three lower pharyngeal plates, and one right and one left upper pharyngeal plates (Fig. 7, B). These plates were described in detail by Cocchi (1864), who based his species Pharyngodopilus africanus on material from the same Barranco Seco site on the island of Gran Canaria. In some of our specimens, there also appears a sigmoidal shape similar to that of Pharyngodopilus crassus. The Barranco Seco pharyngeal plates are very similar, if not identical, to L. multide, according to Sacco (1916), and to L. pavimentatum, according to Simonelli (1889). Moreover, according to Sacco (1916), Pharyngodopilus crassus is synonymous with L. pavimentatum.

Stratigraphic and geographic records:

Very abundant in Miocene deposits of the Mediterranean coasts (Cocchi, 1864). Miocene of France and Portugal (Sauvage, 1875). Miocene of Costa Rica (Laurito et al., 2014). Pliocene of Morocco (Lecointre, 1952).

Order TETRAODONTIFORMES Regan, 1929

Family DIODONTIDAE Bibron in Duméril, 1855

Genus Diodon Linné 1758

Diodon scillae Agassiz, 1843

Material:

2 complete dental plates and one fragment; (Fig. 1, Paläontologisches Museum München) and; ULPGC n°: f111 (Fig. 7: C1) to f113.

Localities:

Barranco de Guiniguada, Barranco Seco (Fig. 2–4).

Comparisons and systematic attribution:

Complete upper dental plate, approximately 18 mm wide. Bilobed structure with heart-shaped contour and triangular-shaped lobes comprised of 14–16 fused blades or platelets. The uppermost pair of platelets are very thin and narrow whereas the two at the base are wider and ellipsoidal or trapezoidal in shape. The specimens are identical to that described by Rothpletz & Simonelli (1890) from Gran Canaria island, which is currently part of the PMM collection [Paläontologisches Museum München] (Fig. 1) and very similar to the specimen from the Miocene of Cuba in shape and dimensions. D. scillae is a senior synonym of D. sigma (Iturralde-Vinent & Case, 1998).

Stratigraphic and geographic records:

Miocene of France (Leriche, 1957), Italy (Menesini, 1969), Miocene of Cuba (Iturralde-Vinent & Case, 1998).

DiscussionTOP

The presence of pillow lavas in relation to the deposits (Meco et al., 2007, 2015) has allowed a dating (ca 4.8 Ma) for Canary fossil fishes, which - from the 19th through to the 21st century - have gone from being attributed to the “Miocene′ (Fig. 1), “Mio-Pliocene′ or “Neogene′ to finally being assigned to the first half of the Early Pliocene.

The age of the Canary deposits allows a reconstruction of the palaeoceanographic scenario in which the fossil fishes considered in this paper lived. A means of communication was open at the time between the Atlantic and Pacific Oceans via the CAS (Erkens, 2015), while the Gibraltar Seaway was again connecting the Atlantic Ocean with the Mediterranean Sea (Garcia-Castellanos et al., 2009). In addition to these circumstances, we need to consider the capacity of some of these fishes to travel large distances.

About 5 to 4 Ma ago, in the Early Pliocene, the earth had a warm, temperate climate (Fedorov et al., 2013). The marine waters of the Canary Islands between 4.8 and 4.2 Ma (Meco et al., 2015, 2016), as well as those of the Azores (Santa Maria Island), were subtropical to warm-temperate seas (Ávila et al., 2012). The presence in the Mediterranean (Lybia) of the genera Galeocerdo, Carcharhinus, Archosargus (?) and Diodon indicates a tropical to equatorial climate (Pawellek et al., 2012).

Among the Chondrichthyan fishes studied we find Carcharocles megalodon and Isurus hastalis, the largest marine predators of the Pliocene (Randall, 1987; Gottfried et al., 1996). It is thought that these were trophic migrators with a pan-oceanic distribution who sought out stable food sources. All of the above lived in all seas during the Early Pliocene. Notable among the Osteichthyes is the presence of the genus Archosargus. The few present day species of this genus live mainly in the western Atlantic, the Caribbean and the Galapagos islands (Smith, 1997). Their presence in the eastern Atlantic and the Mediterranean would be consonant with the palaeogeographic conditions described above (Meco et al., 2015) and related to the CAS. One possible Archosargus has been found in the Early Pliocene of Libya (Pawellek et al., 2012). Diodon scillae has been found in the Miocene of Cuba and the Mediterranean (Iturralde-Vinent & Case, 1998).

The coincidental circumstances of an open CAS and Gibraltar Seaway, along with the capacity of the Chondrichthyes to travel long distances, highlight the tropicopolitan nature of Canary fossil fishes in the Early Pliocene. This is a factor to be considered in the explanation of the presence of numerous Indo-Pacific sharks in the Mediterranean (Pawellek et al., 2012).

The teeth of the genus Galeocerdo found in Gran Canaria Island are comparable to G. aduncus which is a Miocene species (Marsili et al., 2007). For Cigala-Fulgosi & Mori (1979), the main difference between this fossil species and the present-day species (G. cuvier) lies in the greater robustness of the teeth of G. cuvier. Nonetheless, many teeth attributed to G. aduncus due to their stratigraphic origin cannot be distinguished from those of young, small or immature specimens of G. cuvier. According to Cigala-Fulgosi & Mori (1979), the transition or evolution from G. aduncus to G. cuvieri was very rapid and possibly coincided with the start of the Early Pliocene (5.33 Ma); both are present in deposits of the Late Miocene whereas only G. cuvier has been found in Early Pliocene deposits. Consequently, the presence of G. aduncus in the Early Pliocene of Gran Canaria (ca 4.80 Ma) could be added to those from the Early Pliocene of Huelva (SW Spain) (Garcia et al., 2011).

ConclusionTOP

A total of 8 taxa of Chondrichthyes and 3 of Osteichthyes have been identified and classified: Carcharocles megalodon, Parotodus benedeni, Cosmopolitodus hastalis, Isurus oxyrinchus, Carcharias cf. acutissima, Carcharhinus cf. leucas, Carcharhinus cf. priscus, Galeocerdo cf. aduncus, Archosargus cinctus, Labrodon pavimentatum and Diodon scillae.

Of seven fossil shark species found in the Azores and eight in the Canary Islands, six or seven are common to both archipelagos (Carcharocles megalodon, Parotodus benedeni, Cosmopolitodus hastalis, Isurus oxyrinchus Carcharias cf. acutissima, Carcharhinus cf. leucas, and perhaps Galeocerdo cf. aduncus = Carcharhinus egertoni?) (Fig. 8).

In addition, we have also identified among the Osteichthyan fishes from the Canary Islands, thanks to the numerous teeth and dental fragments that have been found the tropical genera Archosargus and Diodon.

The fossil species found in the Early Pliocene of Libya that have also been found in Gran Canaria are: Carcharocles megalodon, Cosmopolitodus hastalis, Isurus oxyrinchus, genera Archosargus cinctus and Diodon scillae.

Carcharocles megalodon, Cosmopolitodus hastalis, Isurus cf. oxyrinchus, Carcharias cf. acutissima, Carcharhinus cf. leucas, Carcharhinus cf. priscus, Galeocerdo cf. aduncus were also present in the Pliocene Pacific coasts of South America. Consequently, their preference for warm waters suggests an open CAS between the Atlantic and Pacific oceans at that time.

Galeocerdo adunctus from the Canary Early Pliocene should to be added to the reference from the same epoch in Huelva (SW mainland Spain).

ACKNOWLEDGEMENTSTOP

This work was sponsored by the Spanish Ministry of the Environment and the University of Las Palmas de Gran Canaria (CN-62/03-02139). We thank the curators of the Paläontologisches Museum München, Bayerische Staatssammlung für Paläontologie und Geologie and of El Museo Canario. We also thank the comments from the Editor and the suggestions from the reviewers.

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