A New Early Cretaceous Lamniform Shark (Chondrichthyes, Neoselachii)

Home , Cardabiodon, Eostriatolamia, Leptostyrax

Zoological Journal of the Linnean Society, 2008, 154, 278–290. With 3 ﬁgures

A new Early Cretaceous lamniform shark (Chondrichthyes, Neoselachii)

JÜRGEN KRIWET1*, STEFANIE KLUG2, JOSÉ I. CANUDO3 and GLORIA CUENCA-BESCOS3 Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 1Museum of Natural History, Department of Collection, Humboldt-University Berlin, Invalidenstr. 43, 10115 Berlin, Germany 2Museum of Natural History, Department of Research, Humboldt-University Berlin, Invalidenstr. 43, 10115 Berlin, Germany 3Grupo Aragosaurus, Universidad de Zaragoza, Facultad de Ciencias, c. Pedro Cerbuna 12, 50009 Zaragoza, Spain

Received 6 September 2007; accepted for publication 17 September 2007

Eoptolamna eccentrolopha gen. et sp. nov. (Chondrichthyes, Lamniformes) from the near coastal upper Barremian Artoles Formation (Early Cretaceous) of Castellote (northwestern Spain) is described on the basis of about 50 isolated teeth. This taxon represents one of the earliest lamniform sharks known to date. We hypothesize that most pre-Aptian lamniforms belong to an ancient group characterized, amongst others, by a very weak gradient monognathic heterodont dental pattern, and by tearing-type dentition. There is a nutritive groove in the lingual root protuberance in juveniles of Eoptolamna, which persists in adults. A single pair of symphysial and a pair of upper intermediate teeth might have been present. Consequently, a new family, Eoptolamnidae, is introduced to include the new form, as well as Protolamna and probably Leptostyrax. The Eoptolamnidae represent an ancient family within Lamniformes. The origin of lamniform sharks remains, however, ambiguous despite recent advances. The new Spanish taxon is widespread in the Barremian of north-eastern Spain, and occurs in a wide range of facies from near-coastal to lake deposits. This lamniform also occurs in the Lower Cretaceous of northern Africa. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290.

ADDITIONAL KEYWORDS: Eoptolamna – Eoptolamnidae – Leptostyrax – morphology – plesiomorphic condition – Protolamna.

INTRODUCTION Early Cretaceous, neoselachians seem to have diver- siﬁed rapidly, and in the late Early Cretaceous, shark Neoselachian sharks are a highly diversiﬁed group of faunas of modern appearance, including open pelagic marine vertebrates occupying the top levels in food and deep-water forms, appeared (Kriwet & Klug, webs, with almost all major clades being known as 2008). However, the fossil record of neoselachians fossils in the Late Jurassic, with the exception of from the uppermost Jurassic and Early Cretaceous Squaliformes and Lamniformes (e.g. Saint-Seine, continues to be relatively incomplete, and interpret- 1949; Thiollière, 1854; Beaumont, 1960; Schweizer, ing Early Cretaceous lamniform diversity is still 1964; Cappetta, 1987; Thies, 1992; Duffin & Ward, ambiguous (e.g. Rees, 2005; Kriwet & Klug, 2008). 1993; Cavin, Cappetta & Seret, 1995; Brito & Seret, Early Cretaceous neoselachian sharks have been 1996; Leidner & Thies, 1999; Kriwet & Klug, 2004; less intensively studied compared with those from the Underwood, 2006). During the Late Jurassic and Late Cretaceous (e.g. Cappetta, 1975; Biddle & Lan- demaine, 1988; Batchelor & Ward, 1990; Biddle, 1993; *Corresponding author. Underwood & Mitchell, 1999; Underwood, Mitchell & E-mail: [email protected] Veltkamp, 1999; Underwood, 2004; Rees, 2005). This

278 © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290 A NEW EARLY CRETACEOUS SHARK 279 is especially evident for those from the Iberian Pen- were dissolved in buffered acetic acid for a maximum insular. The knowledge of Early Cretaceous Iberian of 24 h. The residues were screen washed with a neoselachians, although it has improved in recent 500-mm sieve, and the vertebrate remains were sorted years, is based mainly on small assemblages compris- under a stereoscopic microscope. ing only a few taxa from near-coastal to brackish, The Maestrat sub-basin is one of four Early and even freshwater, deposits in the province of Cretaceous sub-basins (Maestrat, Cameros, Colum- Teruel (Estes & Sanchiz, 1982; Canudo, Cuenca- bres, and South Iberian) in the Iberian Basin, and Bescós & Ruiz-Omenaca, 1996a; Kriwet & Kussius, forms the easternmost Iberian Range. The Iberian 1996; Kriwet, 1999). Basin is a wide intracratonic Mesozoic basin located This paper provides the description of one of the in the north-east of Iberia (Aurell, Bosence &

oldest fossil lamniform species. The new species from Waltham, 1995; Canudo et al., 1996b; Salas & Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 the upper Barremian of Castellote (north-eastern Guimer, 1996; Martín-Chivelet et al., 2002). Its devo- Spain) is assigned to a new genus based on its tooth lopment is related to an anticlockwise rotation of the morphology. The suprageneric placement within lam- Iberian plate and crustal thinning during the Meso- niforms and the generalized and plesiomorphic dental zoic (Martín-Chivelet et al., 2002). This thinning was condition within Lamniformes are discussed. inverted in the Palaeogene, producing the present- day Iberian and Catalonian Coastal Ranges and parts of the surroundings of the Ebro, Duero, and Tajo MATERIAL AND GEOLOGICAL SETTING basins. Generally, two rifting phases are identiﬁed, This paper focuses on about 50 teeth recovered from spanning from the Late Permian to the Triassic and the fossil site of Vallipón in the north-western part of from the late Oxfordian to the Early Cretaceous the Maestrat sub-basin, near the city of Castellote, (Martín-Chivelet et al., 2002). c. 150 km southeast of Zaragoza (Fig. 1). Most teeth The development of the Maestrat, Cameros, Colum- are damaged, i.e. lacking parts of the root and/or bres, and South Iberian sub-basins is related to a crown. Sediment samples of c. 500 kg containing ver- prolonged phase of intracontinental rifting, and coin- tebrate bones and teeth were collected from the basal cided with the gradual opening of the North Atlantic part of the Artoles Formation in this sub-basin, and (e.g. Ziegler, 1988; Vergés & Garcia-Sanz, 2001). They

Figure 1. Geographical and geological situation of the Vallipón site, upper Barremian, near Teruel in north-eastern Spain.

© 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290 280 J. KRIWET ET AL. contain a sedimentary and structural record of three of parasymphyseals(?) present; mesiodistally com- main phases of tectonic subsidence (Salas et al., 2001) pressed teeth, with generally a single pair of lateral and 13 depositional sequences, which are character- cusplets; robust roots with short branches; lingual ized by massive successions of continental to shallow- protuberance more or less massive; with nutritive marine carbonates and clastics. groove, which might be secondarily closed. The Maestrat sub-basin is filled with Upper Jurassic–Lower Cretaceous palustrine and marine Genera included: Eoptolamna gen. nov., Leptostyrax, sediments. The Valanginian–Barremian sequence and Protolamna. (K1.1–K1.7) is up to 1500-m thick, and is characterized by estuarine shallow-water carbonate platforms GENUS EOPTOLAMNA GEN. NOV. along the basin margins with important freshwater Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 discharges. Molluscs and calcareous algae dominated Derivation of name: From the Greek words: ‘eos’, the carbonate production. Three Early Cretaceous meaning ‘dawn, early’; ‘adruptos’, meaning ‘tearing’; formations are recognized in the Vallipón section and ‘Lamna’, meaning ‘modern lamniform shark’, in (from bottom to top): Mirambel (lower Barremian), allusion to the early occurrence and tearing-type Artoles (upper Barremian–lower Aptian) and Utrillas dentition of this lamniform. (Albian) formations. The Artoles Formation, mainly marls and limestones with abundant invertebrate Type species: Eoptolamna eccentrolopha gen. et sp. nov. remains, was formed on a shallow marine platform. There is a 30–50-cm thick layer at its base, consisting Generic diagnosis: Eoptolamnids with the following of sands and conglomerates of red and yellow colour characteristics: tooth crown faces with distinct verti- (e.g. Canudo et al., 1996b; Cuenca-Bescós & Canudo, cal median crest extending from cusp–root junction 2003). This represents a transgressive lag deposit almost to apex; few additional shorter and flexuous containing abundant isolated bones and teeth of ver- ridges present; well-developed lateral cusplets tebrates. The top of the Artoles Formation is dated on broadly united with main cusp, stronger inclined lin- the basis of the macroforaminifer Paleorbitolina len- gually than main cusp, and in front of labial cusp ticularis lenticularis (Blumenbach, 1805), confirming plane in profile view; lingual face of main cusp a late Barremian age for the fossiliferous layers strongly cambered; cutting edges well developed and (Canudo et al., 1996b). Up to now, 43 vertebrate taxa continuous; labial basal sledge smooth, delineating a representing a mixture of marine and continental short and narrow concavity; root high and coalescing forms have been identified (Ruiz-Omeñaca & Canudo, in upper parts, free in lower part; lingual protuber- 2001). Canudo et al. (1996b) proposed a coastal setting ance well developed, but low; nutritive groove narrow for the fossiliferous layer with a hard substrate. The and marked in teeth of juveniles, more faint and isolated bones and teeth of vertebrates were accumu- almost completely closed in adults. lated by predators, shallow streams, and tidal action. Differential diagnosis: The teeth of Eoptolamna gen. SYSTEMATIC PALAEONTOLOGY nov. distinctly differ from all other lamniforms in the presence of a faint, almost completely closed nutritive The terminology and homologies applied here follow groove in the teeth of adult individuals, which is those of Cappetta (1987), Siverson (1996), and marked in juveniles. Shimada (2002).

EOPTOLAMNA ECCENTROLOPHA GEN. ET SP. NOV. CLASS CHONDRICHTHYES HUXLEY, 1880 1996a Protolamna cf. sokolovi Cappetta, 1980; SUBCLASS ELASMOBRACHII BONAPARTE, 1838 Canudo et al.: 51, fig. 8. INFRACLASS NEOSELACHII COMPAGNO, 1977 1999 Protolamna cf. P. sokolovi Cappetta, 1980; SUPERORDER GALEMORPHII COMPAGNO, 1973 Kriwet: 120, text-fig. 2, pl. 2, fig. 4 (non fig. 5). ORDER LAMNIFORMES BERG, 1958 2003 Protolamna cf. sokolovi Cappetta, 1980; FAMILY EOPTOLAMNIDAE NOV. Mendiola & Martinez: 36. Derivation of name: Derived from the name of the 2004 Protolamna cf. sokolovi Cappetta, 1980; Cuny type genus, Eoptolamna gen. nov. et al.: 132, pl. 1, fig. 17–19, pl. 2, figs. 1–3.

Diagnosis: Lamniform sharks only known by isolated Derivation of name: From the Latin word ‘eccentri- teeth and characterized by the following combination cus’, meaning ‘eccentric’, and the Greek word ‘lophos’, of characters: tearing-type dentition with very weak meaning ‘crest’, in allusion to the distinctive labial gradient monognathic heterodonty; a single pair crests.

Type specimen: Anterolateral tooth, MPZ 2005-4 The root of the holotype is badly damaged, with no (Fig. 2A–D), housed in the Museo Paleontológico, Uni- root lobes being preserved. The preserved upper por- versidad de Zaragoza, Spain. tions of the root lobes are coalescing in their upper parts. The lingual protuberance is well developed Type locality and age: Vallipón, west of Castellote, and quite massive. A narrow and shallow nutritive c. 150 km south-east of Zaragoza; Artoles Formation, groove, with a small central foramen, divides the upper Barremian. protuberance.

Type stratum: Basal conglomeratic bed. PARATYPES AND DENTAL HETERODONTY

The dentition of Eoptolamna eccentrolopha gen. et sp. Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 Referred material: About 30 teeth from the Albian of nov. is characterized by a very weak gradient monog- Castellote, Province of Teruel (Figs 2E–Z, 3). nathic heterodonty, exhibiting almost homodont dentition, as exemplified by the tooth morphologies of the Diagnosis: As for genus, monotypic. holotype and the paratypes. We cannot confidently discern whether any real dignathic heterodonty pattern was developed. It is also impossible to estab- ANATOMICAL DESCRIPTION lish the number of anterior, intermediate, lateral, and HOLOTYPE posterior tooth rows. The holotype, an anterolateral tooth (Fig. 2A–D), dis- All teeth are morphologically very similar and bear plays a mesiodistally compressed and erect main cusp a more-or-less well-developed vertical median crest, that is slender and acute. In profile view, the crown is from which the species name is derived. In lateral bent lingually, and in its upper part very slightly teeth the median crest may bifurcate basally. We sigmoidal. The labial crown face is very flat and bears hypothesize that the upper teeth have slightly stron- a vertical median crest, which is broad and superfi- ger distally inclined cusps than the lower ones. cially flattened. This crest is accompanied by a pair of The labial face of the tooth crowns is barely convex short flexuous folds. All folds originate well above the but without a medial flattening, as in several odon- crown–root junction at the level of the notch separat- taspidids. The basal portion of the labial crown face ing the lateral cusplets from the main cusp, and do slightly bulges out over the root in anterior teeth, less not reach the apex. The base of the labial face is so in lateral ones. The enameloid boundary labially constricted, giving the crown a lanceolate appearance. delineates a long and narrow concavity reaching up The cutting edges are well developed and continuous between the bases of the lateral cusplets in all teeth. with the cutting edges of the lateral cusplets. Basally, There are few small and mesiodistally compressed the cutting edges are very close together so that the teeth (Fig. 3F, G) that display, with their very narrow marginolingual portions of the strongly cambered and lanceolate cusps, low number of labial folds, lingual crown face are visible in labial view. closely arranged lateral cusplets, and irregular The base of the crown is quite high and devoid of length of the root lobes, the general morphology of any ornamentation. The enameloid extends tongue- symphyseal teeth. Symphyseal teeth are those located like onto the upper portions of the root lobes. There is near the jaw symphysis, but are not directly on it and a single pair of lateral cusplets without any ornamen- are generally small by convention (Shimada, 2002). tation, with the distal one being slightly abraded. The root lobes of all teeth coalesce in their upper They are massive, broad, and acute, with a rounded part, but are free in their lower parts. The lobe base in cross section. Both are divergent from the extremities, as far as being preserved, are subtabular main cusp: rising from bases below that of the cusp, but not spatulate. but being broadly united with the base of the cusp. The number of anterior and lateral tooth rows The lateral cusplets are separated from the main cusp remains unknown, because these teeth are formed in by narrow notches. In lateral view, the lateral cus- the anterior and posterior dental bullae, respectively, plets are inclined lingually and well in front of the which generally are not preserved in fossil forms labial cusp plane. The basal portion of the cusp is (Siverson, 1999). Anterior and anterolateral teeth of bulbous, and overhangs the root to some extent. the new taxon (Figs 2A–J, 3A–C) are characterized by The lingual crown face is very convex from side to high and slender main cusps, and display only a few side, and bears some closely arranged and flexuous labial folds. The root is very narrow, with root lobes folds that originate at the base of the crown and reach forming an acute angle in labial view. The angle up to the middle of the crown. The lingual neck, between the basal face of the root and the long axis of which separates the crown from the root, is broad and the crown is 30–40° in profile view. Unfortunately, all completely smooth. anterior to anterolateral teeth are damaged, so that

© 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290 282 J. KRIWET ET AL. Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021

Figure 2. Eoptolamna eccentrolopha gen. et sp. nov. from the upper Barremian of Vallipón. A–D, anterolateral tooth, MPZ 2005-4, holotype. A, labial view. B, profile view. C, lingual view. D, occlusal view. E–G, symphyseal? tooth, MPZ 2005-5, paratype. E, labial view. F, profile view. G, lingual view. H–J, anterior tooth, MPZ 2005-6, paratype. H, labial view. I, profile view. J, lingual view. K–N, lateral tooth, MPZ 2005-7, paratype. K, labial view. L, labio-occlusal view. M, profile view. N, lingual view. O–R, lateral tooth, MPZ 2005-8, paratype. O, labial view. P, labio-occlusal view. Q, profile view. R, linguo-occlusal view. S–V, lateral tooth, MPZ 2005-9, paratype. S, labial view. T, labio-occlusal view. U, profile view. V, lingual view. W–Z, posterior tooth, MPZ 2005-10, paratype. W, labial view. X, profile view. Y, lingual view. Z, occlusal view. Scale bar: 0.5 cm. ᭣ Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021

Figure 3. Eoptolamna eccentrolopha gen. et sp. nov. from the upper Barremian of Vallipón. A, anterolateral tooth, MPZ 2005-11, paratype, labial view. B, lateral tooth, MPZ 2005-12, paratype, labial view. C, lateral tooth, MPZ 2005-13, paratype, lingual view. D, lateral tooth, MPZ 2005-14, paratype, lingual view. E–F, anterolateral tooth, MPZ 2005-15, paratype. E, lingual view. F, labial view. G, intermediate? tooth, MPZ 2005-16, paratype, labial view. Scale bars: 0.25 cm. the exact morphology of the root lobes of most tooth posterior dental bullae in the upper jaw (Siverson, positions is not detectable. However, several specimens 1999). Several small specimens (Fig. 3G) display mor- (Fig. 2E–G) display mesial or distal, or both, root lobes, phological features that may correspond to those of which are elongated, quite delicate, and narrow, with upper intermediate teeth. However, because of the size rounded, not-spatulate extremities. In lateral view, the of these teeth, they may also come from juvenile attachment surface of the root is almost horizontal, individuals. with slightly basally curved root lobes in lateral posi- In lateral teeth, the number of labial folds increases tions. The angle between the basal root face and the (Fig. 2K–P). The median labial fold is longer and axis of the crown is generally 30°. In a few teeth, the reaches the apex in most teeth from these positions. root lobes are slightly curved or are bent basally. In addition, the lateral cusplets also bear vertical and Identiﬁcation of intermediate teeth in lamniform ﬂexuous labial and lingual folds reaching the apex. sharks is very difficult. Intermediate teeth are consid- The root lobes are more distinctly separated, forming ered to be small teeth formed more-or-less directly on a more obtuse angle in more lateral tooth positions the intermediate bar separating the anterior from the (Fig. 3D). The lingual root protuberance is also less

© 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290 284 J. KRIWET ET AL. well developed in anterolateral–lateral teeth (Fig. 2F, and their assignment to distinct tooth rows in fossil M, U). The vertical nutritive groove separating the lamniforms is generally hampered by the fact that lingual protuberance is narrow, but is deeper than in the teeth are generally not found associated or anterior teeth. articulated. Complete lamniform skeletons are, for The tooth crowns become lower towards the com- instance, only known from the Upper Cretaceous missure, and the number of labial folds increases limestones of Lebanon (e.g. Cappetta, 1980). progressively (Fig. 2W–Z). The lateral cusplets are The origin of Lamniform sharks and their ﬁrst less well separated from the main cusp. appearance in the fossil record has been continuously The material contains abundant small teeth, with argued about. For instance, Maisey, Naylor & Ward total heights less than 1 mm. These teeth most prob- (2004) placed the Jurassic neoselachian Sphenodus

ably belong to juveniles. Small teeth of juvenile indi- within lamniforms, based on dental characters such Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 viduals mainly differ in their overall size and a deeper as the form of the tooth crown. However, the skeletal vertical nutritive groove in the lingual root protuber- and dental morphology (Duffin & Ward, 1993; ance. This lingual nutritive groove is still present in Böttcher & Duffin, 2000; Kriwet & Klug, 2004) of adult individuals, although it is less well marked. this shark is more similar to Synechodus, an extinct and basal Mesozoic galeomorph, suggesting closer relationships between both. Another Jurassic shark, SYSTEMATIC AFFINITIES AND DISCUSSION Palaeocarcharias from the Tithonian of southern Lamniform sharks constitute a well-defined mono- Germany, which is known by several well-preserved phyletic group (e.g. Carvalho, 1996; Shirai, 1996; skeletons, was considered to be a basal lamniform by Martin & Naylor, 1997; Naylor et al., 1997), with a Beaumont (1960). Duffin (1988), however, concluded fossil record that mainly consists of isolated teeth or that this shark shows many orectolobiform characters artificial tooth sets. The order comprises 15 living but has teeth more similar to lamniforms, and thus species in mid-to-low latitude oceans worldwide, represents a stem-group representative of Lamni- ranging from intertidal zones to deep seas formes. In the following, Cappetta (1987) placed this (Compagno, 1999). Most lamniforms possess a unique selachian in the vicinity of lamniforms, and Applegate heterodont dentition called the ‘lamnoid tooth (2001) suggested thatPalaeocarcharias should be pattern’, indicating that lamniform sharks possess placed within its own family because of the interme- teeth that are well differentiated in the jaws, depend- diate morphology. We do not confer with Underwood’s ing on their formation in the anterior and posterior (2006) statement that the intermediate morphology dental bullae, respectively. These generally include of Palaeocarcharias would suggest an origin of enlarged anterior teeth, a gap or small intermediate lamniforms (and probably carcharhiniforms) within teeth separating the anterior teeth from the lateral a paraphyletic clade Orectolobiformes, because teeth in the upper jaw, lateral teeth, and smaller the monophyly of orectolobiforms is well supported posterior ones (Compagno, 1984; Shimada, 2001). (Shirai, 1996; Goto, 2001; Winchell, Martin & Mallatt, Symphyseal teeth are present in some modern 2004). lamniforms such as Mitsukurina, Carcharias, and A major reason for disputing the origin of lamni- Odontaspis (Shimada, 2002). According to Compagno forms (as well as other neoselachians) is that Early (1990), lamniform sharks share three synapomor- Cretaceous marine sediments are quite rare, and, phies: (1) lamnoid dental pattern (symphyseal, additionally, the lowermost Early Cretaceous is still anterior, intermediate, and lateral tooth rows); (2) not well studied. The Albian is the earliest Cretaceous reduction of labial cartilages; (3) elongate ring-type period that was extensively studied, for neoselachian intestinal valve with more than 15 turns. In addition, remains from a wide array of facies, and that yielded Shimada (2002) considers the presence of upper and abundant lamniform remains (e.g. Biddle, 1993; lower dental bullae supporting the symphyseal and Welton & Farish, 1993; Siverson, 1997; Underwood anterior teeth to be a synapomorphy of Lamniformes. & Mitchell, 1999; Underwood & Rees, 2002; Cuny The dental bullae are hollows on the inner side of the et al., 2004; Kriwet, 2006). Conversely, Berriasian– jaws where the teeth are formed. These hollows are Barremian sediments were only rarely targeted for separated from each other by a marked thickening neoselachians (e.g. Biddle, 1988; Canudo et al., 1996a; (‘intermediate bar’), which generally (with the excep- Kriwet, 1999; Rees, 2005; Sweetman & Underwood, tion of extant Carcharias species) bears no teeth. The 2006). absence of these bullae in the microphageous lamni- The systematic arrangement of Cretaceous lamniforms, Megachasma and Cetorhinus, are supposed to forms is subject to controversy. So far, the following be secondary losses. The presence of such bullae in lamniform taxa have been indicated in Early Hemipristis, conversely, is regarded as convergent Cretaceous strata (Cappetta, 1987; Siverson, 1997; development. However, identification of isolated teeth Kriwet, 2006; J. Kriwet, pers. observ.): Anacoracidae

– Eoanacorax, Microcorax, Palaeoanacorax, and Eoptolamna gen. nov.; (3) lateral cusplets are sepa- Squalicorax; Cretoxyrhinidae sensu Cappetta (1987) rated by a comparably broader notch from the main – Archaeolamna, Cretalamna, Cretodus, Cretox- cusp in the lateral teeth of Protolamna; (4) teeth of yrhina, Leptostyrax, Paraisurus, and Protolamna; Protolamna have only the basal part of the crown Mitsukurinidae – Anomotodon, Paranomotodon, and covered by folds; (5) there is no distinct vertical Scapanorhynchus; Odontaspididae – Eostriatolamia, median fold in Protolamna; (6) the lateral cusplets Hispidaspis, and Johnlongia; Cardabiodontidae – are more-or-less in the same plane as the labial crown Cardabiodon; Family incertae sedis – Dwardius, and face in Eoptolamna gen. nov., and are signiﬁcantly in Priscusurus. The arrangement of these taxa into front of the labial face plane; (7) the lateral cusplets families, however, differs among researchers, and are without ornamentation in the anterior teeth of

depends on the interpretation of the dental formulas Eoptolamna gen. nov.; (8) root lobes are generally long Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 derived from arranging isolated teeth into artificial and parallel in Protolamna, giving the root a rectan- tooth sets. For instance, Siverson (1999) considers gular appearance in labial and lingual view, and are Cretoxyrhinidae to be monotypic, and that taxa, pre- more divergent in Eoptolamna gen. nov.; (9) the viously assigned to Cretoxyrhinidae (e.g. Cappetta, lingual root protuberance of the root is very 1987), should be placed into other suprageneric pronounced and high in Protolamna, whereas the taxa. Others (e.g. Underwood, 2006) follow a more protuberance is less well-developed and is lower in traditional approach. Here, we follow the arguments Eoptolamna gen. nov.; (10) the lingual protuberance of Siverson (1999) and Siverson & Lindgren (2005), of anterior teeth is sometimes divided by a median and consider Cretoxyrhinidae to represent a suitable groove in Protolamna, whereas teeth of all positions genus within which to place different Cretaceous and all sizes (ontogenetic stages?) of Eoptolamna gen. lamniforms with similar tooth morphologies. Never- nov. display a more-or-less well-developed median theless, the grouping of fossil lamniforms according nutritive groove; (11) the basal face of the root pro- to their dental pattern (e.g. number of tooth rows) tuberance and root lobes are in the same plane in interpreted from artificial tooth sets (e.g. Siverson, Eoptolamna gen. nov., whereas the root lobes are bent 1996, 1999) is quite precarious. Consequently, we basally compared with the basal face of the protuber- did not use the number of individual tooth rows ance in Protolamna. (e.g. number of anterior tooth rows and presence/ The genus Protolamna was originally described for absence of intermediate upper tooth rows) in fossil teeth from the Aptian of France by Cappetta (1980). taxa only known from isolated teeth for arranging Teeth of this taxon are characterized by a very fossil lamniforms into systematic categories, but massive root with a protruding lingual protuberance, instead used general morphological traits. which is at least half as high as the total tooth. Other Most Early Cretaceous lamniforms are not known characteristics include strongly lingually inclined from sediments older than the Aptian. So far, teeth of lateral cusplets and that the lateral margins of the Eostriatolamia, Cretalamna, and Protolamna have crown are visible in labial view, a character that is been recovered from Valanginian–Barremian strata. also present in Leptostyrax and Eoptolamna gen. nov. Kriwet (1999) described and illustrated fragmentary So far, six species have been assigned to Protolamna: teeth from the Barremian of Galve (north-eastern Protolamna borodini Cappetta & Case, 1975 from the Spain) as Carcharias sp., which most probably belong lower Maastrichtian of New Jersey, USA (Case & to Eostriatolamia. The only record of a single pre- Cappetta, 2004); Protolamna carteri Cappetta & Aptian tooth of Cretalamna also comes from the same Case, 1999 from the Cenomanian of Texas; Protola- locality (Kriwet, 1999). All other pre-Aptian lamni- mna compressidens (Herman, 1977) from the form records were assigned to Protolamna, which also Coniacian of Belgium, Turonian of France, and include the oldest known lamniform remains from the Turonian–Coniacian of Texas (Cappetta & Case, Valanginian to date (Rees, 2005). Additional lamni- 1999); Protolamna gigantea from the Cenomanian of form teeth from the Barremian of Spain and France Minnesota (Case, 2001); Protolamna roanokeensis were also placed into Protolamna (Biddle, 1988; Cappetta & Case, 1999 from the Albian of Texas; Canudo et al., 1996a; Kriwet, 1999). Protolamna sokolovi Cappetta, 1980 (the type species) Of these genera, the teeth of Protolamna and from the Aptian of France and Albian of Russia Leptostyrax resemble those of Eoptolamna gen. nov. (Sokolov, 1978). Biddle (1988), Kriwet (1999) and Rees However, as demonstrated below, Eoptolamna gen. (2005) described small samples of lamniform teeth nov. is easily separable from these two genera. from the Barremian and Valanginian, respectively, Dental differences between Eoptolamna gen. nov. that superficially resemble those of Protolamna.All and Protolamna include: (1) teeth of adult individuals teeth are comparably small, not reaching 10 mm in of Eoptolamna gen. nov. are comparably smaller; (2) total height, and are characterized by an easily dis- lateral teeth are more mesiodistally compressed in cernable nutritive foramen in the lingual protuber-

© 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290 286 J. KRIWET ET AL. ance. Although similar, the assignment of the pairs of lateral cusplets, indicating some degree of Barremian teeth to Protolamna was already ques- gradient monognathic heterodonty. tioned by Kriwet (1999), who, however, maintained Teeth of Leptostyrax differ in many aspects from a conservative interpretation. All lamniform teeth teeth of Protolamna (see also Cuny et al. (2004) for a from the lowermost Cretaceous of Spain previously listing of dental differences between both). A very assigned to Protolamna share a more-or-less well- remarkable difference is the lingual crown ornamen- pronounced nutritive groove in the lingual root pro- tation, which is very faint and restricted to the crown tuberance of supposed juvenile and adult teeth, and base in Leptostyrax, whereas it comprises long folds are morphologically more-or-less identical with the reaching up to the cusp tip in Protolamna. However, teeth from Castellote. Cappetta & Case (1999) illustrated a tooth of P.

Dental differences between Eoptolamna gen. nov. compressidens from the Turonian–Coniacian of Texas, Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 and Leptostyrax include: (1) teeth of adult individuals which displays a completely smooth lingual crown of Eoptolamna gen. nov. are distinctly smaller; (2) face. Teeth of P. compressidens, however, are easily labial ornamentation of Eoptolamna gen. nov. are separated from those of Eoptolamna gen. nov. by characterized by a distinct median vertical crest, having more delicate and higher lateral cusplets, whereas the labial ornamentation of Leptostyrax con- which are more acute and distinctly curved inwards sists of short, flexuous, and densely arranged folds, towards the main cusp. Moreover, the root is almost which are restricted to the basal portion of the crown; as high as the crown. (3) lateral cusplets are more needle-like and are well The Spanish teeth are remarkably small and separated from the main cusp by a deep notch in display different degrees of labial ornamentation. In Leptostyrax, whereas the lateral cusplets are more anterior teeth, there are only a few labial folds, massive and smaller in Eoptolamna gen. nov.; (4) in whereas the number of folds increases towards the Eoptolamna gen. nov. the cutting edges are continu- commissure of the jaws. This pattern indicates some ous between the main cusp and the lateral cusplets, sort of heterodonty, although teeth of anterior and in contrast with Leptostyrax; (5) two pairs of lateral lateral positions are rather similar in morphology. cusplets may be present in the lateral teeth of Lep- The teeth described as Protolamna sp. cf. P. sokolovi tostyrax; (6) in Eoptolamna gen. nov. there is lingual by Kriwet (1999) from the Barremian of Galve and ornamentation by long, flexuous ridges, with the Alcaine, and as cf. Protolamna by Cuny et al. (2004) middle ridge extending up to the tip of the cusp; (7) from the Albian of Tunisia also display this variation the lingual protuberance of the root is more pro- in fold numbers, and are referred to the new genus, nounced and high in Leptostyrax; (8) the lingual pro- Eoptolamna gen. nov. Lamniform teeth described tuberance of the root is always devoid of a median from the Valanginian of Poland (Rees, 2005) and nutritive groove in Leptostyrax; (9) the root lobes Barremian of France (Biddle, 1988), conversely, are more strongly curved basally in profile view in display the characteristic morphology and ornamen- Leptostyrax. tation of teeth of Protolamna. Leptostyrax is a lamniform shark that is generally Eoptolamna gen. nov. forms, together with Lep- assigned to the Cretoxyrhinidae, although its tooth tostyrax and Protolamna, a distinct species group that morphologies strongly differ from those of Cretox- is characterized by a very weak gradient monognathic yrhina. This genus is best known from the Albian– heterodonty, with a ?single pair of symphyseal teeth, Cenomanian of the USA (Welton & Farish, 1993; and anterior and lateral teeth characterized by a Cappetta & Case, 1999), but it also occurs in the distinct root morphology (high and robust), with a ?lower Campanian of Germany (Albers & Weiler, more-or-less well-developed vertical nutritive groove 1964), ?Santonian of Sweden (Siverson, 1992), dividing the lingual root protuberance. Assignment to Albian–Cenomanian of England (Underwood & other Cretaceous lamniform families is difficult. Simi- Mitchell, 1999), Albian of Australia (Siverson, 1997), larities exist with members of the Cretoxyrhinidae, and Albian of Angola (Antunes & Cappetta, 2002). Odontaspididae, and Miitsukurinidae. Cretoxyrhin- So far, no associated dentition of this shark has idae sensu Siverson (1999) only contain Cretoxyrhina been recovered. However, Welton & Farish (1993) (cf. Cappetta, 1987; Underwood, 2006). Teeth of Cre- presented a tentative dental reconstruction of Lep- toxyrhina are characterized by a very well-developed tostyrax macrorhiza, a species seemingly restricted to lingual root protuberance with a vertical nutritive the Albian of the USA (Cappetta & Case, 1999) that groove in juveniles, which is absent in adult individu- shows a pair of parasymphyseals and an intermediate als. In addition, the overall morphology of the crown upper tooth. In the reconstruction of Welton & Farish and root differs from that of Eoptolamna gen. nov. and (1993), all teeth bear a single pair of lateral cusplets. similar forms. Teeth of members of Mitsukurinidae However, Cappetta & Case (1999) and others indicate differ most significantly in the lingual crown orna- that the lateral teeth of L. macrorhiza often bear two mentation consisting of folds, which are basally

© 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 278–290 A NEW EARLY CRETACEOUS SHARK 287 always parallel. More similar are teeth of odontaspi- whereas the Spanish material has very distinctive dids. These generally are characterized inter alia by dental features, and represents a new genus of ple- very irregular and ﬂexuous lingual folds, and a well- siomorphic lamniforms. This taxon is very common in developed lingual root protuberance with a well- the Lower Cretaceous of Oliete, Aguilón, and Aliaga marked nutritive groove in all ontogenetic stages. The in north-eastern Spain, where it occurs in near- teeth of Eoptolamna gen. nov., however, differ in the coastal to even lake depositional settings (J. Kriwet presence of a faint, almost completely closed nutritive and S. Klug, pers. obser.). groove in adult teeth, although it is more marked in juveniles. Additionally, the crown morphology of Eop- tolamna gen. nov. differs remarkably from the odon- ACKNOWLEDGEMENTS

taspidid teeth. We therefore assign the new Spanish Downloaded from https://academic.oup.com/zoolinnean/article/154/2/278/2614020 by guest on 25 March 2021 species and similar forms to a new family of Early This research was made possible by two DFG Cretaceous lamniform sharks, Eoptolamnidae. The (German Research Foundation) grants to JK (KR presence of a fairly homodont dentition, with probably 2307/1-1 and KR 2307/3-1), by financial support from a single pair of parasymphyseals, is considered to the Spanish Ministry of Education and Science and represent the plesiomorphic dental pattern in lamni- the ERDF (‘CGL200403393’), and by the Government form sharks. of Aragon (‘Financiación de Grupos Consolidados 2005–2006’) to JIC and GC-B. Special thanks go to the Grupo Aragosaurus at the Universidad de Zara- CONCLUSIONS goza for assistance and support during JIC’s and The teeth described in this study are representatives GC-B’s fieldwork. We also acknowledge discussions of one of the earliest lamniform sharks known to date. with and information provided by C.J. Underwood Previously, most lamniform teeth from the Early Cre- (London, UK). The constructive reviews and helpful taceous have been assigned to the genus Protolamna, suggestions of two anonymous reviewers are greatly displaying quite generalized tooth and dental mor- acknowledged. phologies. This taxon has generally been, along with others, arranged into the Cretoxyrhinidae, which is, however, considered to be monotypic (sensu Siverson, REFERENCES 1999). Here, we hypothesize that most pre-Aptian Albers H, Weiler W. 1964. Eine Fischfauna aus der oberen lamniforms belong to an ancient, probably systemati- Kreide von Aachen und neuere Funde von Fschresten aus cally basal, group that is inter alia characterized by a dem Maastricht des angrenzenden belgisch-holländischen very weak homodont dental pattern and by a robust Raumes. Neues Jahrbuch für Geologie und paläontologie, root. Abhandlungen 120: 1–33. Consequently, we introduce a new family, Eoptola- Antunes MT, Cappetta H. 2002. Sélaciens du Crétacé mnidae, for these taxa. Unfortunately, it is not pos- (Albien-Maastrichtian) d’Angola. Palaeontographica 264: sible to reconstruct the number of rows because the 85–146. material of all these taxa comprises isolated findings Applegate SP. 2001. The origin of the lamniform sharks – a that cannot be arranged unambiguously into tooth study in morphology and paleontology of recent and fossil sets. The Eoptolamnidae represent a basal family genera. American Elasmobranch Society 2001, Annual within the Lamniformes. Other pre-Aptian lamni- Meeting, Abstracts. form records include a few teeth of Cretalamna Aurell M, Bosence D, Waltham D. 1995. Carbonate ramp (Otodontidae) and Eostriatolamia? (Odontaspididae). depositional systems from a late Jurassic epeiric platform The origin of lamniform sharks remains, however, (Iberian Basin, Spain): a combined computer modelling and ambiguous. The dental pattern of Palaeocarcharias outcrop analysis. Sedimentology 42: 75–94. Batchelor TJ, Ward D. 1990. Fish remains from a from the Upper Jurassic of southern Germany differs temporary exposure of the Hythe Beds (Aptian – Lower significantly from the earliest Cretaceous lamniform Cretaceous) near Godstone, Surrey. Mesozoic Research 2: teeth, especially in the morphology of the root. 181–203. Isolated lamniform shark teeth are quite common Beaumont G de. 1960. Contribution à l’étude des genres in marine, lagoonal, and even brackish deposits of the Orthacodus Woodw. et Notidanus Cuv. (Selachii). Mém. Early Cretaceous throughout Europe. The oldest lam- Suisses Paléontol. 77: 1–46. niform remains are from the Valanginian of Poland Berg LS. 1958. System der rezenten und fossilen Fischartigen (Rees, 2005). In the Barremian, lamniform remains und Fische [Translated from the 2nd Russian edition]. were reported from the Paris Basin, France (Biddle, Berlin: VEB Deutscher Verlag der Wissenschaften. 1988), and from northeastern Spain (Canudo et al., Biddle J-P. 1988. Contribution a l’étude des sélaciens du 1996a; Kriwet, 1999). The Polish and French speci- Crétacé du Bassin de Paris. Découverte de quelques nouv- mens display the characteristics of Protolamna, elles espèce associées à une faune de type wealdien dans le

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